Asian Countries Asian Towards a More Effective Operational Response Arsenic Contamination of Groundwater in South and East Asian Countries

VOLUME II TECHNICAL REPORT

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Towards a More Effective Operational Response Arsenic Contamination of Groundwater in South and East Asian Countries

Volume II Technical Report

The World Bank Environment and Social Unit - South Asia Region Water and Sanitation Program (WSP) - South and East Asia

This volume is a product of the staff of the International Bank for Reconstruction and Development/The World Bank and of the Water and Sanitation Program. The findings, interpretations, and conclusions expressed in this paper do not necessarily reflect the views of the Executive Directors of The World Bank or the governments they represent.

The World Bank does not guarantee the accuracy of the data included in this work. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgement on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries. Volume II Technical Report Towards a More Effective Operational Response

2 3 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table of Contents

Acknowledgments 10 Executive Summary of Volume I - Policy Report 11 Abbreviations and Acronyms 17

Paper 1 Acknowledgments 20 Summary 21 1. Introduction 27 • Pathways of Arsenic Exposure 27 • Drinking Water Regulations and Guidelines 28 • World Distribution of High-Arsenic Groundwaters 28 2. Arsenic Distribution in South and East Asia 30 • Overview 30 • Alluvial, Deltaic, and Lacustrine Plains 32 – Bangladesh 32 – Bengal Delta and Associated Aquifers, India 39 – Terai Region, Nepal 41 – Irrawaddy Delta, Myanmar 43 – Quaternary Aquifers, Taiwan, China 44 – Alluvial Plains, Northern China 45 – Red River Plain, Vietnam 49 – Mekong Valley: Cambodia, Laos, Thailand, and Vietnam 51 – Indus Plain, Pakistan 53 • Mining and Mineralized Areas 54 – Ron Phibun, Thailand 54 – Rajnandgaon District, Madhya Pradesh, India 56 – Other Areas 57 3. Hydrogeochemistry of Arsenic 58 • Overview 58 • Arsenic Sources 58 • Processes Involved in Mobilization 60 – Oxidation of Sulfide Minerals 60 – Release from Iron Oxides 62 – Release from Other Metal Oxides 64 – Groundwater Blow and Transport 64 – Impact of Human Activities 65 • At-Risk Aquifers 67 • Variability in Arsenic Concentrations 69 – Spatial Variability 69 – Temporal Variability 69 VOL II TECHNICAL REPORT 4. Groundwater Management for Drinking Water and Irrigation and Water Drinking for Management Groundwater 4. Report Technical II Volume Table 10. Brequency Distribution of Arsenic Concentrations in Groundwater Samples Groundwater in Concentrations Arsenic of Distribution Brequency 10. Table Mekong the in Tubewells from Groundwater for Data Arsenic Summary 9. Table Valley Mekong the in Tubewells from Groundwater for Data Arsenic Summary 8. Table Plain, River Red the in Tubewells from Groundwater for Data Arsenic Summary 7. Table High-Arsenic the in Wells Dug from Groundwater for Data Arsenic Summary 6. Table the from Groundwater in Concentrations Arsenic of Distribution Brequency 5. Table the from Groundwaters in Concentrations Arsenic of Distribution Brequency 4. Table Analyzed in Concentrations Arsenic of Distribution Brequency 3. Table from Tubewells from Groundwater in Arsenic of Distribution Brequency 2. Table Monitoring and Surveying for Recommendations 5. Table 1. Summary of the Distribution, Nature, and Scale of Documented of Scale and Nature, Distribution, the of Summary 1. Table Tables References Glossary Remarks Concluding 6. • • • • • • eietr qies73 73 – – – Aquifers Sedimentary Areas Mineralized and Mining Overview qie eeomn n elTsig81 – – – Monitoring – – – Testing Well and Development Aquifer Overview rmNrhr ujb54 53 52 48 43 48 42 Punjab Northern from PDR Lao of Valley 50 35 Cambodia of Aquifers Pleistocene and Holocene the from Those into Divided Vietnam, Basin Huhhot the of Region Groundwater Mongolia Inner Basin, Huhhot Myanmar of Aquifer Alluvial Nepal from Samples Groundwater 77 Bangladesh in Aquifers Alluvial Quaternary 73 76 Water Surface Aquifers (Older) Deep from Groundwater Groundwater Shallow ep(le)Aufr nAsncPoeAes85 81 81 83 85 L µg (>50 Problems Arsenic 84 Variations Temporal Assess to Needed Research Burther Areas Arsenic-Prone in Aquifers (Older) Deep Problems Arsenic Recognized with Aquifers Sedimentary Shallow Aquifers High-Arsenic below Aquifers Deep Aquifers High-Arsenic Potentially Risk Potential Low of Aquifers Towards a More Effective Operational Response Operational Effective More a Towards -1 nAufr nSuhadEs sa32 Asia East and South in Aquifers in ) 73 73 84 80 80 90 89 87 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 11. Brequency Distribution of Arsenic Concentrations in Water from Ron Phibun Area 56 Table 12. Brequency Distribution of Arsenic Concentrations in Groundwater from Chowki Block, Madhya Pradesh, India 56 Table 13. Typical Arsenic Concentrations in Rock-Borming Minerals 59 Table 14. Typical Arsenic Concentration Ranges in Rocks, Sediments, and Soils 61 Table 15. Risks Associated with the Use of Drinking Water from Various Sources at Various Scales and Potential Mitigation Strategies 79 Table 16. Arsenic Testing Strategies in Potential High-Arsenic Groundwater Provinces 82 3igures Bigure 1. Summary of the World Distribution of Documented Problems with Arsenic in Groundwater and the Environment 29 Bigure 2. Map of South and East Asia Showing the Locations of Documented High-Arsenic Groundwater Provinces 30 Bigure 3. Smoothed Map of Arsenic Distribution in Groundwater from Bangladesh 33 Bigure 4. Maps of the Distribution of Arsenic in Shallow Groundwater from the Chapai Nawabganj Area, Northwest Bangladesh 34 Bigure 5. Variation in Concentration of Arsenic and Other Elements with Depth in a Purpose-Drilled Piezometer in Chapai Nawabganj, Northwest Bangladesh 35 Bigure 6. Map of West Bengal Showing Districts Affected by High Groundwater Arsenic Concentrations 40 Bigure 7. Map of China Showing the Distribution of Recognised High-Arsenic (>50 µg L-1) Groundwaters and the Locations of Quaternary Sediments 45 Bigure 8. Regional Distribution of Arsenic in Groundwaters from the Shallow and Deep Aquifers of the Huhhot Basin 47 Bigure 9. Geological Map of Cambodia Showing Distribution of Potentially High-Arsenic Aquifers 51 Bigure 10. Simplified Geology of the Ron Phibun Area, Thailand, Showing the Distribution of Arsenic in Analyzed Groundwaters 55 Bigure 11. Schematic Diagram of the Aquifers in Southern Bangladesh Showing the 4 5 Distribution of Arsenic and the Configuration of Wells 63 Bigure 12. Sea Level Changes during the Last 140,000 Years 65 Bigure 13. Classification of Groundwater Environments Susceptible to Arsenic Problems from Natural Sources 68 Bigure 14. Monitoring Data for Groundwater from Selected Wells and Specially Drilled Piezometers in Baridpur Area, Central Bangladesh 71 Boxes Box 1. Analysis of Arsenic 31 Box 2. Shallow versus Deep Aquifers 36 Box 3. Dug Wells 38 Box 4. Brequently Asked Questions 66 VOL II TECHNICAL REPORT ne .OeainlRsossUdrae ySuhadEs sa onre 140 MatricesforImplementation ofOperationalResponsesto Annex 2. Operational ResponsesUndertakenbySouthandEast AsianCountries Annex 1. Annexures References 5. Conclusions IncentivesforDifferent Stakeholders toAddress ArsenicContamination 4. ArsenicMitigationintheContextofOverallWater SupplySector 3. Arsenic:HealthEffects, RecommendedValues, andNationalStandards 2. Introduction 1. Summary 2 Paper Report Technical II Volume euainlRs 136 135 135 135 136 134 134 133 128 Reputational Risk • 120 Short-Term versusLong-Term Solutions 130 • Institutional Aspects 132 • Media NationalandInternational • Rural andUrbanAreas 130 • Number ofArsenicosisPatients • NumberofPeopleatRisk • 105 Remaining IssuesandRecommendations • DefinitionandIdentificationofArsenicContaminationHotspots • ArsenicPriority Compared toBacteriological Water QualityPriority • AccesstoImproved Water Sources inAsianCountries • Background • 106 Dissemination ofInformation • 107 107 104 Longer-Term 102 Responses • Initial Responsestowards SuspectedArsenicContamination • Operational ResponsesofCountriesinSouthandEastAsia • Ingestedthrough Arsenic theFoodChain • Major HealthEffects • Major LimitationsofExistingEpidemiologicalStudies • andNational Standards forArsenicIntake International • umr eak 129 115 128 123 118 121 120 SummaryRemarks 113 Regional Arsenic NetworksandNationalDatabases – – Technical Longer-Term ResponsesBasedonGroundwater Technical Longer-Term– ResponsesBasedonSurfaceWater Longer-Term Institutional – Responses(ArsenicCountryPolicy) – 108 Treatment Management ofArsenicosisPatients PatientIdentification – Well Switching,PaintingofTube Wells,– andAwareness Screening andIdentificationofContaminationLevelsin Water Sources – – rei otmnto 141 Arsenic Contamination Towards a More Effective Operational Response Operational Effective More a Towards 161 138 134 130 130 102 101 99 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Annex 3. Operational Responses to Arsenic Contamination: Questionnaire Results 148 Annex 4. Government, NGOs, International Organizations Involved in Operational Responses 155 Annex 5. Health Effects of Chronic Exposure to Arsenic in Drinking Water 157 Tables Table 1. Currently Accepted National Standards of Selected Countries for Arsenic in Drinking Water 102 Table 2. Chronology of Recommended WHO Values for Arsenic in Drinking Water 103 Table 3. Current Population at Risk in Asian Countries 116 Table 4. Summary of Responses to Arsenic Contamination Based on Surface Water 124 Table 5. Summary of Responses to Arsenic Contamination Based on Groundwater 125 Table 6. Access to Improved Water Sources in Selected Asian Countries 130 Table 7. Percentage of Population in Selected Asian Countries with Sanitation 131 Table 8. Child Mortality Rates in Selected South and East Asian Countries 131 Table 9. Conceptualized Incentive Matrix: Stakeholder Incentives for Action on Arsenic Issues 137 Boxes Box 1. Comparison of Field Testing and Laboratory Analysis 109 Box 2. Parameters to Assess the Capacity of Laboratory Analysis 110

Paper 3 Summary 167 1. Introduction 169 2. Treatment of Arsenic-Contaminated Water 170 • Oxidation-Sedimentation Processes 170 • Coagulation-Sedimentation-Filtration Processes 172 • Sorptive Filtration 176 6 7 • Membrane Techniques 182 • Comparison of Arsenic Removal Technologies 182 3. Laboratory and Field Methods of Arsenic Analysis 186 • Laboratory Methods 186 • Field Test Kit 186 4. Alternative Water Supply Options 190 • Deep Tubewell 190 • Dug or Ring Well 192 • Surface Water Treatment 192 • Rainwater Harvesting 194 • Piped Water Supply 195 • Cost Comparison of Alternative Water Supply Options 196 VOL II TECHNICAL REPORT iue1.PatcSetCthet194 191 181 193 179 178 174 180 175 178 PlasticSheetCatchment 174 Figure13. PondSandFilterforTreatment ofSurfaceWater Figure 12. DeepTubewell withClaySeal 173 Figure11. Tetrahedron ArsenicRemovalTechnology Figure 10. 175 Shapla Filter forArsenicRemovalatHouseholdLevel 188 Figure 9. Three KalshiFilterforArsenicRemoval Figure 8. 201 GranularFerricHydroxide-Based ArsenicRemovalUnit 187 Figure 7. AlcanEnhancedActivatedAluminaUnit Figure 6. Correlation betweenIron andArsenicRemovalinTreatment Plants Figure 5. Tubewell-Attached ArsenicRemovalUnit Figure 4. DPHE-DanidaFillandDrawArsenicRemovalUnit Figure 3. StevensInstituteTechnology 194 Figure 2. DoubleBucketHouseholdArsenicTreatment Unit 197 Figure 1. 183 Figures CostofWater SupplyOptionsforArsenicMitigation Table 8. Technological CostsofAlternative OptionsinArsenic-Affected Areas Table 7. AdvantagesandDisadvantages ofRainwaterCollectionSystem Table 6. ComparisonofArsenicFieldTest Kits 185 184 Table 5. LaboratoryAnalysisMethodsforArsenic Table 4. ComparisonofCostsDifferent ArsenicTreatment Technologies inIndia Table 3. ComparisonofArsenicRemovalMechanismsandCostsinBangladesh Table 2. ComparisonofMainArsenicRemovalTechnologies Table 1. Tables References Conclusions 6. OperationalIssues 5. Report Technical II Volume .AnIdealApproach toEvaluationofArsenic MitigationMeasures 2. TheIssue 1. Summary Paper 4 ldeDsoa 199 198 Costs • Sludge Disposal • Technology Verification andValidation • nIelMdl217 219 213 216 Problems withtheIdealModel • AnIdealModel • Uncertainty andtheIdealApproach • • Aims ofThisPaper • iutoa nlss214 Situational Analysis Towards a More Effective Operational Response Operational Effective More a Towards 203 202 199 198 216 213 211 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

• The Nth Best Model 221 • Is Passing a Cost-Benefit Test Sufficient? 222 3. The Cost of Arsenic Mitigation Measures: Review of Possible Actions 225 • Health Effects of Arsenic in Drinking Water 225 – Cancer Health Effects 225 – Treatment of Arsenicosis Sufferers 227 • Mitigation of Arsenic in Drinking Water 227 – Groundwater 227 – Surface Water 229 – Technology Choice 230 4. Applying the Model 240 • Methodology for the Model 240 • Data and Estimates for the Model 240 • Results for the Model 244 5. Summary and Conclusions 250 References 258 Annex 1 Detailed Technology Costs 251 Tables Table 1. Ranking of Projects 223 Table 2. Arsenic Mitigation Technology Options 231 Table 3. Small Village: Capital and Operation and Maintenance Costs 231 Table 4. Small Village: Technology-Specific Level of Service 232 Table 5. Medium Village: Capital and Operation and Maintenance Costs 232 Table 6. Medium Village: Technology-Specific Level of Service 233 Table 7. Large Village: Capital and Operation and Maintenance Costs 233 Table 8. Large Village: Technology-Specific Level of Service 234 Table 9. Small Villages: Present Value Analysis of Technology Costs 235 8 9 Table 10. Medium Villages: Present Value Analysis of Technology Costs 235 Table 11. Large Villages: Present Value Analysis of Technology Costs 236 Table 12. Small Villages: Total Costs of Mitigation Technology Options 237 Table 13. Medium Villages: Total Costs of Mitigation Technology Options 238 Table 14. Large Villages: Total Costs of Mitigation Technology Options 238 Table 15. All Villages: Total Costs of Mitigation Technology Options 239 Table 16. Present Value of Costs of Arsenic Mitigation Options for Whole Population 241 Table 17. Bangladesh: Estimated Health Impact of Arsenic Contamination of Tubewells 242 Table 18. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 5% 246 Table 19. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 10% 247 Table 20. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 15% 248 VOL II TECHNICAL REPORT managed design and publication arrangements. publication and design managed Mehr Vandana Dawson. John by edited was documentation study The study. this for information provided who organizations numerous W the in colleagues many the and survey study the of respondents the Kathmandu, in workshop the hosting for Nepal in Irrigation th from Kansakar Ratna Dibya and Office) Nepal Bank, (World Ranjitkar Shyam thank to like also would team The study. the during for Region) Asia South Economist, (Chief Devarajan Shantayanan and Region) Asia South director, Regional and (Country McKechnie Environm and Social Asia South Director, (Acting Racki Jeffrey to gratitude their express to like would team The 2004. April in Kath in held Workshop Arsenic to Responses Operational Regional the at and 2004 Bebruary in D.C. Washington, in Week Water Bank sessio the at participants from comments numerous from benefited study the addition, In Tavares. Luiz and Saghir Jamal Pollard, Smit Kaufmann, Rachel Ghani, Ejaz Alaerts, Guy Ahmad, Junaid and reviewers); (peer Khouri Nadim and Briscoe, John Berg, den van by provided were comments Valuable GWMATE). and London College University/University (Reading Koundouri Phoebe and Technology) Engine of University (Bangladesh Ahmed Beroze Bank), (World Talbi Amal Survey), Geological (British Smedley Pauline by prepared wer papers background The Asia). (WSP-East Rosenboom Jan-Willem and GWMATE); - Team Advisory Management Groundwater Bank (World a Boster Stephen Bank); (World Vale Carla and Ijjasz-Vasquez, Ede Talbi, Amal leaders); (co-task Minnatullah Khawaja and Kemper com team a by prepared was It (DBID). Development International for Department UK the and Program Partnership Water Netherlands financ additional with Asia, East and South of Programs Sanitation and Water the and Bank World the by conducted was study This Acknowledgments ent Unit), Alastair Unit), ent n held at the World the at held n orld Bank, WSP and WSP Bank, orld e Department of Department e nd Albert Tuinhof Albert nd ering and ering ing from the Bank the from ing their guidance their a Misra, Rick Misra, a posed of Karin of posed mandu, Nepal, mandu, a (WSP) a Caroline e Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Executive Summary of Volume I – Policy Report

Background and Introduction i. The detrimental health effects of environmental exposure to arsenic have become increasingly clear in the last few years. High concentrations detected in groundwater from a number of aquifers across the world, including in South and East Asia, have been found responsible for health problems ranging from skin disorders to cardiovascular disease and cancer.

ii. The problem has increased greatly in recent years with the growing use of tubewells to tap groundwater for water supply and irrigation. The water delivered by these tubewells has been found in many cases to be contaminated with higher than recommended levels of arsenic. In the study region, countries affected include Bangladesh (the worst affected), India, Myanmar, Nepal, and Pakistan (South Asia); and Cambodia, China (including Taiwan), Lao People’s Democratic Republic, and Vietnam (East Asia).

iii. This study concentrates on operational responses to arsenic contamination that may be of practical use to actors who invest in water infrastructure in the affected countries, including governments, donors, development banks, and nongovernmental organizations (NGOs).

Objectives and Audience of the Study iv. The objectives of this study are (a) to take stock of current knowledge regarding the arsenic issue; and (b) to provide options for specific and balanced operational responses to the occurrence of arsenic in excess of permissible limits in groundwater in Asian countries, while taking into account the work that 10 11 has already been carried out by many different stakeholders.

v. The study provides information on (a) occurrence of arsenic in groundwater; (b) health impacts of arsenic; (c) policy responses by governments and the international community; (d) technological options for and costs of arsenic mitigation; and (e) economic aspects of the assessment and development of arsenic mitigation strategies. The focus of the study is on rural rather than urban areas, due to the particular difficulties associated with applying mitigation measures in scattered rural communities.

vi. The study is structured as follows:

Volume I: Policy Report. This report summarizes the main messages of Volume II, and highlights the policy implications of arsenic mitigation. Volume II Technical Report Towards a More Effective Operational Response

This Volume II comprises four specialist papers: • Paper 1. Arsenic Occurrence in Groundwater in South and East Asia: Scale, Causes, and Mitigation • Paper 2. An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia • Paper 3. Arsenic Mitigation Technologies in South and East Asia • Paper 4. The Economics of Arsenic Mitigation

The Scale of the Arsenic Threat

vii. In South and East Asia an estimated 60 million people are at risk from high levels of naturally-occurring arsenic in groundwater, and current data show that at least 700,000 people in the region have thus far been affected by arsenicosis. However, although the negative health effects of arsenic ingestion in general, and the specific impact of ingestion of arsenic- contaminated groundwater, have both been widely studied, there is still no clear picture of the epidemiology of arsenic in South and East Asia, and uncertainty surrounds such issues as the spatial distribution of contamination; the symptoms and health effects of arsenic-related diseases, and the timeframe over which they develop; and the impact of arsenic compared to other waterborne diseases whose effects may be more immediate.

viii. While arsenic is clearly an important public health threat, it needs to be noted that morbidity and mortality due to other waterborne diseases is also a serious health issue. Therefore, mitigation measures to combat arsenic contamination in South and East Asia need to be considered within the wider context of the 12 13 supply of safe water.

ix. Due to the carcinogenic nature of arsenic, the World Health Organization (WHO) recommends a maximum permissible concentration for arsenic in drinking water of 10 µg L–1 (micrograms per liter), which has been adopted by most industrial countries. Most developing countries still use the former WHO-recommended concentration of 50 µg L–1 as their national standard, due to economic considerations and the lack of tools and techniques to measure accurately at lower concentrations. Further studies are needed to assess the relationship between levels of arsenic and health risks in order to quantify the inevitable trade-offs at different standards between such considerations as health risks, the ability of people to pay for safe water, and the availability of water treatment technology. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Distribution of Arsenic Contamination

x. The concentration of arsenic in natural waters globally, including groundwater, is usually below the WHO guideline value of 10 µg L–1. However, arsenic mobilization in water is favored under reducing (anaerobic) conditions, leading to the desorption of arsenic from iron (and other metal) oxides. In South and East Asia such conditions tend to occur in shallow aquifers in Quaternary strata underlying the region’s large alluvial and deltaic plains (Bengal basin, Irrawaddy delta, Mekong valley, Red River delta, Indus plain, Yellow River plain). (Some localized groundwater arsenic problems relate to ore mineralization and mining activity, which are not the focus of this study.) Recent hydrogeochemical investigations have improved our knowledge of the occurrence and distribution of arsenic in groundwater, though much uncertainty remains regarding the source, mobilization, and transport of the element in aquifers.

xi. One of the important findings of recent detailed aquifer surveys has been the large degree of spatial variability in arsenic concentrations, even over distances of a few hundred meters. Temporal variability also occurs, though insufficient monitoring has been carried out to establish a clear picture of variations in arsenic levels over different timescales.

Arsenic Mitigation Measures xii. Arsenic mitigation requires a sequence of practical steps involving enquiry and associated action. Assessing the scale of the problem (now and over time) involves field testing, laboratory testing, and monitoring; identifying appropriate mitigation strategies involves technological, economic, and sociocultural analysis of possible responses; and implementation involves awareness raising and direct action by governments, donors, NGOs, and other stakeholders at local, national, and regional levels. Sustainability in the long run remains a major challenge.

xiii. The two main technological options for arsenic mitigation are (a) switch to alternative, arsenic-free water sources; or (b) remove arsenic from the groundwater source. Alternatives in the first category include development of arsenic-free aquifers, use of surface water and rainwater harvesting; alternatives in the second category involve household-level or community-level arsenic removal technologies. For each option there will be a wide range of design specifications and associated costs.

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

xiv. Despite continuing uncertainty regarding arsenic occurrence and epidemiology, the lethal nature and now well-established effects of arsenic exposure in South and East Asia make it necessary that informed choices and trade-off decisions are made to address arsenic contamination of drinking water sources and the scope and extent of mitigation measures, within the context of the development of the water sector and the wider economy.

xv. Accordingly, a simple cost-benefit methodology has been developed that takes into account data limitations and provides decisionmakers with an approach for rapid assessment of the socioeconomic desirability of different mitigation policies under various scenarios. In particular, the methodology permits an analysis of options in order to choose between different approaches in dealing with (a) the risk that arsenic might be found in an area where a project is planned; and (b) the risk mitigation options where a project’s goal is arsenic mitigation per se.

xvi. Demand-side perspectives are an important consideration for designing arsenic mitigation measures that meet the requirements of households and communities. For example, are users willing to pay for an alternative such as piped water? Demand preferences can be assessed through contingent valuation or willingness to pay studies and can provide important guidance to decisionmakers. There is a need to strengthen institutional capacities in the countries to carry out such assessments.

The Political Environment of Arsenic Mitigation xvii. Arsenic has become a highly politicized topic in the international development 14 15 community and within some affected countries due to its carcinogenic characteristics and due to the earlier failure to consider it as a possible natural contaminant in groundwater sources. This factor makes rational analysis of the issue difficult and highlights the fact that application of mitigation measures needs to consider the political as well as the social and economic climate. The scattered rural communities most affected by arsenic contamination often have limited political presence and are in particular need of support.

xviii. Governments that want to address the arsenic issue will therefore have to take a stronger lead role in their countries and on the international plane. This goes both for more strategic research and knowledge acquisition regarding arsenic in their countries, as well as for the choice and scope of arsenic mitigation activities. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The Importance of an Effective Operational and Strategic Approach xix. Significant strides have been made since arsenic was first detected in drinking water tubewells in Eastern India and Bangladesh in the late 1980s and early 1990s. However, a range of factors — including projected population growth in the region, continuing private investment in shallow tubewells, and the drive towards achievement of the Millennium Development Goal related to safe water supply — add to the urgency of adopting a more strategic approach for effective action at project, national, and international levels.

xx. At project level, any interventions that consider using groundwater as a source must involve an assessment of whether occurrence of arsenic would affect the outcome of the project. Such an assessment would include consideration of technical factors (such as screening and possible mitigation technologies), social and cultural factors, and economic factors (including a cost-benefit or least-cost analysis).

xxi. Some countries have taken arsenic to the national level of attention, including Bangladesh, Nepal, and Cambodia. Others, such as India, Pakistan, and China, have only started to address the issue, while in other international organizations such as UNICEF and local NGOs and universities are the focal points for arsenic-related activities. Although the characteristics of arsenic contamination are unique to each affected country, study results suggest that three simple steps would help governments more effectively address the problem now and in the future: (a) encourage further research in potentially arsenic-affected areas in order to better determine the extent of the problem; (b) ensure that arsenic is included as a potential risk factor in decision-making about water-related issues; and (c) develop options for populations in known arsenic-affected areas.

xxii. At the global level, focused research on the chemistry of arsenic mobilization and the dose-response relationships for arsenic are of vital importance in formulating a more effective approach. If governments and the international community are to achieve the MDGs in water supply and sanitation then the knowledge gaps regarding arsenic need to be filled, notably by (a) further epidemiological research directly benefiting arsenic- affected countries; (b) socioeconomic research on the effects of arsenicosis, understanding behavior and designing demand-based packages for the various arsenic mitigation techniques; and (c) hydrogeological and hydrochemical research.

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

xxiii. It also needs to be made clear that, due to the nature of arsenic itself, in the not- so-distant future there will be diminishing returns on investments in scientific arsenic research to reduce uncertainty. The important challenge will be to identify those areas where improved research-level data collection is likely to provide a major return. For other areas the main question will be how to manage in the face of unavoidable and continuing uncertainty.

xxiv. Accordingly, the international dialogue should shift towards targeted research priorities that address these issues. This would also include the pursuit of the research agenda regarding arsenic in the food chain. Both the World Bank and a number of development partners are contributors to the Consultative Group on International Agricultural Research (CGIAR) and this organization would lend itself to building up a coherent and focused research agenda on this topic in order to provide decisionmakers with guidance regarding arsenic-contaminated groundwater.

16 17 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Abbreviations and Acronyms

The following list includes all abbreviations and acronyms used throughout Volumes I and II of the report. AAN Asian Arsenic Network AAS atomic absorption spectrometer/spectrometry AES atomic emission spectrometry AIIH&PH All India Institute of Hygiene and Public Health APSU Arsenic Policy Support Unit (Bangladesh) As arsenic ASV anodic stripping voltammetry AusAID Australian Agency for International Development AWWA American Water Works Association BAMWSP Bangladesh Arsenic Mitigation Water Supply Project BGS British Geological Survey BUET Bangladesh University of Engineering and Technology CBA cost-benefit analysis CCA chromated copper arsenate CEPIS Pan American Center for Sanitary Engineering and Environmental Sciences (Peru) CGIAR Consultative Group on International Agricultural Research Danida Danish Agency for International Development DB discount factor DOC dissolved organic carbon DPHE Department of Public Health Engineering (Bangladesh) DWSS Department of Water Supply and Sewerage (Nepal) EAWAG Swiss Bederal Institute for Environmental Science and Technology EPA Environmental Protection Agency (United States) GDP gross domestic product GB-AAS graphite furnace-atomic absorption spectrometry GPL General Pharmaceutical Ltd. GPS global positioning system GWMATE World Bank Groundwater Management Advisory Team HG-AAS hydride generation-atomic absorption spectrometry HG-ABS hydride generation-atomic fluorescence spectrometry ICP inductively coupled plasma ICP-MS inductively coupled plasma-mass spectrometry IRC International Water and Sanitation Center (formerly International Reference Center for Community Water Supply) JICA Japan International Cooperation Agency Lao PDR Lao People’s Democratic Republic MDG Millennium Development Goal MS mass spectrometry NAMIC National Arsenic Mitigation Information Center (Bangladesh) NASC National Arsenic Steering Committee (Nepal) NGO nongovernmental organization NPV net present value NRC National Research Council (United States) NRCS Nepal Red Cross Society NTU nephelometric turbidity unit PAHO Pan American Health Organization PV present value SDDC silver diethyldithiocarbamate SORAS solar oxidation and removal of arsenic TCLP toxic characteristic leaching procedure UNCHS United Nations Centre for Human Settlements UNDP United Nations Development Program UNICEB United Nations Children’s Bund WHO World Health Organization WRUD Water Resources Utilization Department (Myanmar) Units of Measurement µg microgram mg milligram kg kilogram L liter µg L-1 micrograms per liter mg L-1 milligrams per liter cm centimeter m meter km kilometer

Units of Currency (January 2004)

1 US$ = 58 taka (Tk) (Bangladesh) 1 US$ = 48 rupees (Rs) (India) Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation VOL 2 TECHNICAL REPORT Paper I Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation

Prepared by Dr. Pauline Smedley, British Geological Survey VOL II TECHNICAL REPORT Bredericks (United Nations Children’s Bund, Cambodia) also provided helpful advice and information on groundwater in Cambodia. in groundwater on information and advice helpful provided also Cambodia) Bund, Children’s Nations (United Bredericks Davi report. this reviewed and information provided who Survey), Geological (British Holmes David and Chilton, John Kinniburgh, David by and Bank/WSP); (World Minnatullah Khawaja and Kemper Karin Team); Advisory Management (Groundwater Tuinhof Albert Steph Bank); (World Talbi Amal by made were contributions Particular elsewhere. and Asia in organizations academic and Nations, the organizations, nongovernmental governments, including sources, of range wide a from drawn was document the for Information Acknowledgments d en Boster; en United Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Summary

1. The detrimental health effects of environmental exposure to arsenic have become increasingly clear in the last few years. Drinking water constitutes one of the principal pathways of environmental arsenic exposure in humans and high concentrations detected in groundwater from a number of aquifers across the world have been found responsible for health problems ranging from skin disorders to cardiovascular disease and cancer. Food represents a further potential exposure pathway to arsenic, particularly where crops are irrigated with high-arsenic groundwater or where food is cooked in high-arsenic water. However, the relative impact on human health is as yet unquantified and in need of further study.

2. The concentration of arsenic in natural waters globally, including groundwater, is usually low. Most have concentrations below the World Health Organization (WHO) provisional guideline value for arsenic in drinking water of 10 µg L–1. However, arsenic mobilization in water is favored under some specific geochemical and hydrogeological conditions and concentrations can reach two orders of magnitude higher than this in the worst cases. Most occurrences of high-arsenic groundwater are undoubtedly of natural origin.

3. Major alluvial and deltaic plains and inland basins composed of young sediments (Quaternary; thousands to tens of thousands of years old) are particularly prone to developing groundwater arsenic problems. Many of the identified affected aquifers are located in South and East Asia. High concentrations have been found in groundwater from such aquifers in the Bengal basin of Bangladesh and eastern India; the Yellow River plain and some internal basins of northern China; the lowland Terai region of Nepal; the Mekong valley of Cambodia; the Red River delta of Vietnam; and the Irrawaddy delta of Myanmar. Problems may also emerge in similar alluvial and deltaic environments 20 21 elsewhere in the world. Unfortunately, such flat-lying fertile plains are often densely populated and so poor groundwater quality can have a major impact on large numbers of people. The increasing incidence of arsenic-related health problems in these areas largely coincided with the change to using groundwater from tubewells, which began in the 1970s and 1980s.

4. The detailed mechanisms by which the arsenic mobilization occurs in sedimentary aquifers are still not well understood. However, the development of reducing (anaerobic) conditions in the aquifers has been recognized as a key risk factor for the generation of high-arsenic groundwater. Indicators of such conditions include lack of dissolved oxygen and high dissolved iron and manganese concentrations. High-pH, oxidizing (aerobic) groundwater conditions have also been linked with high groundwater arsenic concentrations in some

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

parts of the world, though there is as yet no evidence for this means of occurrence in aquifers of South and East Asia. Arid inland basins such as occur in northern China and Mongolia represent possible areas for such conditions, but few data exist for such areas. Slow groundwater movement is also considered an important risk factor since under such conditions arsenic can be dissolved from minerals in the aquifer but is not readily flushed out of the system. Flat-lying sedimentary basins and delta plains are typically areas of such slow groundwater movement.

5. One of the key findings of the last few years has been that the sediments in these high-arsenic aquifers do not contain unusually high arsenic concentrations. Typical concentrations are of the order of 5–10 mg kg–1; values rather close to world averages. Nor do the sediments contain unusual arsenic minerals. It is therefore feasible that any young sedimentary aquifers could develop high-arsenic groundwater, given the special geological and hydrogeological conditions outlined above. Hence, other regions in Asia and elsewhere with young sedimentary aquifers may contain groundwater with high arsenic concentrations, but have not yet been identified. Given the increased awareness of arsenic problems and increased groundwater testing that is currently being undertaken in various parts of Asia, it is likely that other areas with problems will be identified more rapidly than was previously the case. The existence of unrecognized problems on such a large scale as that identified in the Bengal basin is not impossible but is considered unlikely.

6. Mineralized areas, particularly areas of mining activity, are also at increased risk of groundwater arsenic contamination, although, unlike young sedimentary aquifers, the affected areas are typically of local extent (a few kilometers around 22 23 the mineralized zone). Some geothermal areas may also give rise to increased groundwater arsenic concentrations, though this is also a less regionally significant occurrence.

7. Despite the advances made in recent years in understanding where high-arsenic groundwaters are likely to exist on a regional scale, predictability on a local scale is still poor and probably will always be so. Short-range (well-to-well) variability in groundwater arsenic concentrations is often large. This means that individual wells used for drinking water need to be tested in recognized arsenic-affected areas. Despite common associations between arsenic and a number of other trace elements (for example iron, manganese) in groundwater, observed correlations in water samples are usually weak. Hence, although other elements may signal potential problems regionally, they are not reliable as proxy indicators of arsenic concentrations in individual wells. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

8. Temporal variations in groundwater arsenic concentrations are also poorly defined. Significant seasonal and longer-term variations have been claimed to occur in some groundwaters from affected aquifers, though the information is largely anecdotal and difficult to verify. Temporal variation has major consequences for mitigation efforts and is in need of further investigation. However, in the interim, major short-term changes in groundwater arsenic concentrations are not expected in most cases. Hence, it is reasonable to assume that an initial determination is likely to be representative, provided the result is analytically reliable.

9. In areas affected by high-arsenic groundwater, there has been much investigation into finding alternative sources of safe (low-arsenic) drinking water. Many of the options focus on the use of surface water (including rainwater), water from dug wells, and water from deep aquifers.

10. Surface waters usually have low dissolved arsenic concentrations. This is because of the low solid:/solution ratios in surface conditions compared to aquifers, and to the oxidizing conditions that pertain in most surface environments. Under oxidizing conditions, adsorption of arsenic to sediments and soils occurs and mobilization in soluble form is not favored. Exceptions can occur locally in some mining environments as a result of direct contamination or in surface waters with a major proportion of discharging high-arsenic groundwater. However, the normally strong adsorption of arsenic to stream sediments is likely to remove the dissolved arsenic from these sources over time. Arsenic may persist in some surface waters affected by geothermal inputs or evaporation (under high-pH conditions) but high concentrations related to these processes have not been identified in Asia and are not considered of major importance in the region. Some arsenic in surface waters may be associated with particulate matter rather than being truly dissolved, especially if the water is turbid. The overwhelming drawback of surface waters is their often poor bacterial quality. This also has major health implications and has been an important factor in determining the shift towards increased use of groundwater from tubewells in Asia over the last few decades. Surface waters therefore usually require sanitary treatment before use for potable supply.

11. Dug wells have also often been found to contain groundwater with low concentrations of arsenic in areas where tubewell groundwaters yield high concentrations. As with surface waters, groundwater in dug wells is typically relatively oxidizing, comprising a high proportion of freshly recharged rainwater and being open to the atmosphere. Most groundwater samples analyzed from dug wells in Bangladesh, West Bengal, Myanmar, and Nepal have been found to

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contain arsenic concentrations less than 50 µg L–1 (the national standard for most countries in Asia). As a result of this, dug wells have been promoted in some high-arsenic areas as alternative sources of drinking water. However, the concentrations cannot always be guaranteed to be low. Sporadic occurrences above 50 µg L–1 have been found in groundwater from dug wells in a number of the recognized high-arsenic provinces. Some may be in the particulate rather than dissolved fraction, but such details are rarely specified in reports from the affected regions. Nevertheless, dissolved concentrations of up to 560 µg L–1 have been found in dug well water from Inner Mongolia (China) where anaerobic conditions have been maintained in low-lying areas of groundwater discharge that are characterized by sluggish groundwater movement. More chemical analysis is required to obtain an improved database of arsenic concentrations for dug wells. As with surface waters, shallow dug wells are vulnerable to contamination from surface pollutants and pathogenic organisms. They are also more prone to drying up in areas with large water table fluctuations. They are therefore unlikely to represent a major long-term solution to the arsenic problems identified in most areas of South and East Asia, although they may provide a suitable interim solution (given adequate sanitary protection) in some affected areas if their arsenic concentrations can be demonstrated to be reliably low.

12. In some arsenic-affected regions of Asia, low-arsenic groundwater has been found in deeper aquifers underlying the young affected sediments. Groundwater with low arsenic concentrations (<10 µg L–1) has been found in, for example, deep aquifers in the Bengal basin (Bangladesh, India) and the Nepal Terai. The depth at which these aquifers occurs varies considerably (tens to hundreds of meters) and so considerable confusion has arisen over the descriptions of these aquifers. The stratigraphy of the aquifers is poorly defined in most countries. 24 25 More investigation has been carried out in Bangladesh than elsewhere. Here, the deep aquifers with low-arsenic groundwater are mineralogically distinct from the younger overlying sediments and are relatively oxic. They are likely to be of Pleistocene age (Quaternary; greater than 10,000 years old) and are considered to have undergone more flushing by groundwater over their geological history than the sediments bearing high-arsenic groundwater that overlie them.

13. These older aquifers in Bangladesh, West Bengal, and Nepal represent a potential alternative source of safe (low-arsenic) drinking water for the affected populations. However, considerable uncertainty exists over their long-term sustainability in the event of significant exploitation. Further hydrogeological research is required to investigate whether, and to what extent, they would be susceptible to drawdown of high-arsenic groundwater from overlying aquifers or Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

saline water in coastal areas following significant aquifer development. However, research effort on these aquifers should be complementary to the implementation of mitigation measures and not a reason for delaying them.

14. Although older, deeper Quaternary aquifers in the Bengal basin and Nepal have been found to contain low groundwater arsenic concentrations, this has been found not to be the case in some other regions. In parts of northern China, high arsenic concentrations have been found in groundwater from both shallow (young Quaternary) and deeper (older Quaternary) aquifers. Here, the inland deep aquifers are thought not to have been well flushed during the Quaternary ice ages because of slow groundwater flow and closed-basin conditions. Some groundwaters in Pleistocene aquifers of Vietnam also appear to have high arsenic concentrations. Aquifer depth is therefore not an indicator of susceptibility to arsenic mobilization. Rather, dissolved arsenic concentrations are determined by a combination of geochemical conditions suitable for mobilizing it and hydrogeological conditions which prevent its removal. Hence, groundwater quality with respect to arsenic concentrations must be considered on an aquifer-by-aquifer basis and good hydrogeological and geochemical understanding of young sedimentary aquifers is a prerequisite to groundwater development.

15. On a regional scale, our understanding of arsenic mobilization processes is sufficiently developed to allow some kind of prediction of where arsenic problems are likely to occur and where not. Young sedimentary aquifers in alluvial and deltaic plains and inland basins are obvious areas for priority groundwater testing. Randomized reconnaissance groundwater arsenic surveys of such areas are the logical first step in identifying problem areas, followed by more detailed surveys and mitigation if problems emerge. In identified arsenic problem areas, ideally every well used for drinking water should be tested for arsenic. Given the high toxicity of arsenic to humans, there is an argument for reconnaissance testing of groundwaters from any aquifer used for potable water supplies regardless of aquifer type and lithology. However, groundwater testing in Asia necessarily involves prioritization, with greatest emphasis on the aquifers at greatest risk.

16. A central tenet of both understanding the nature and scale of arsenic problems in groundwater and mitigating them is the acquisition of reliable analytical data for arsenic. Poor data can lead to erroneous conclusions and hence inappropriate responses. However, reliable chemical analysis of arsenic in water is not a trivial undertaking and requires continual attention to quality assurance.

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Many groundwater arsenic analyses in Asia have been carried out using field test kits and these are particularly prone to problems with poor precision and accuracy. Great emphasis should be placed on obtaining good-quality analytical data during testing and monitoring programs. Such programs need to take account of local laboratory arsenic analytical capability and build in capability development where necessary.

17. Although a number of groundwater provinces have been found with high arsenic concentrations, it is important to keep the scale of contamination in perspective. Groundwater from most aquifers has acceptably low arsenic concentrations and in most cases is less prone to bacterial contamination. In many areas of Asia and elsewhere, groundwater represents a reliable source of safe drinking water. Indeed, in some arid areas it constitutes the only source of water. Even in Bangladesh, which has suffered by far the greatest impact from groundwater arsenic problems, national statistics based on randomly collected groundwater samples indicate that 27% of shallow groundwaters (from tubewells <150 m deep) have arsenic concentrations greater than the Bangladesh standard of 50 µg L–1 and 46% have concentrations greater than 10 µg L–1. This means that 73% and 54% respectively have concentrations below these values and are therefore deemed to be of acceptable quality. Given that considerable investment has been made in groundwater in countries such as Bangladesh over the last few decades, it would be costly and over-reactive to abandon groundwater in favor of alternatives without first carrying out testing programs and, where necessary, further hydrogeological investigations.

18. This report provides an overview of the current state of knowledge on the occurrence, distribution, and causes of arsenic problems in water supplies in 26 27 South and East Asia. It also characterizes likely ‘at-risk’ aquifers and the types of indicators that may be used to identify them. Response strategies in terms of analytical testing and monitoring will vary widely depending on factors such as the scale of the arsenic problem, the numbers of operating wells, the population served, the water use, and the scope for alternative water sources. Some of these issues are investigated and strategies for testing and monitoring outlined. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

1. Introduction

Pathways of Arsenic Exposure

he dangers associated with long-term exposure to arsenic are now well known. The most Tprominent health problems in affected populations are skin disorders (melanosis, keratosis, skin cancer) but a large range of other disorders, including internal cancers (bladder, lung, kidney), cardiovascular diseases, peripheral vascular disorders, respiratory problems, and diabetes, have also been linked to chronic high doses of ingested arsenic.

Drinking water can be one of the most important pathways of exposure to arsenic in human populations and groundwater sources are thought to be responsible for the majority of the world's chronic arsenic-related health problems. Despite this, most groundwaters have low or very low concentrations of arsenic (well below regulatory and recommended limits) and in a global context they often constitute the most reliable sources of safe drinking water. Groundwater is also less vulnerable to contamination from the waterborne diseases that can be a serious problem in many surface waters. It appears to be only when certain geological and hydrogeochemical conditions arise in aquifers that arsenic problems occur on a regional and problematic scale. This report describes those occurrences and the geochemical processes controlling them and attempts to provide guidance on the criteria for identifying, monitoring, and dealing with these problem areas.

Although drinking water is known to be closely linked to chronic arsenic-related health problems, the sometimes poor relationship observed between arsenic intake from water and health symptoms poses the possibility that other pathways of arsenic exposure may also occur. Food is one potential source. Crops irrigated with high-arsenic groundwater are potentially vulnerable to arsenic take-up, particularly following long-term groundwater use and soil arsenic accumulation. Some studies have shown higher-than-background concentrations of arsenic in vegetables. Higher concentrations have typically been found in roots than in stems, leaves, or economic produce. However, few results have been published so far. Meharg and Rahman (2003) considered that rice irrigated with high-arsenic groundwater could represent a significant contribution to the arsenic intake in some of the Bangladeshi population. In a study of dry rice grain produced by groundwater irrigation, they found concentrations up to 1.8 mg kg-1 (compared, for example, with the 1 mg kg-1 Australian standard for inorganic arsenic in food). However, few samples were analyzed and the values found are higher than those in other studies of naturally cultivated rice carried out to date (Abedin, Cotter-Howells, and Meharg 2002). The bioavailability of arsenic in rice is also uncertain and is strongly influenced by the proportions of organic and inorganic forms present. Comparatively high concentrations have been found in rice straw, which could affect the doses taken by grazing animals (Abedin and others 2002). Clearly, more research needs to be carried out on arsenic uptake by crops in irrigated areas and on food for, and produced from, grazing animals. Since arsenic is phytotoxic, uptake by vegetation may be inhibited and may therefore not be the greatest concern. However, long-term effects on crop yield, especially of rice, could become an important issue (Abedin and Meharg, 2002).

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Arsenic-contaminated air is also a potential exposure pathway in some cases. In Guizhou Province, southern China, severe chronic health problems have arisen from the burning of local coal with very high arsenic concentrations (up to 35,000 mg kg-1), the exposure being both by inhalation and consumption of chillis dried over domestic coal fires (Finkelman, Belkin, and Zheng 1999). This pathway is much more localized than that from drinking water but, in China, an estimated 3,000 people in several villages of Guizhou Province have arsenicosis symptoms as a result of exposure from this source (Ding and others 2001).

Drinking Water Regulations and Guidelines

Regulatory and recommended limits for arsenic in drinking water have been reduced in recent years following increased evidence of its toxic effects to humans. The World Health Organization (WHO) guideline value was reduced from 50 µg L-1 to 10 µg L-1 in 1993 although the recommendation is still provisional pending further scientific evidence. Western countries are reducing, or have reduced, their national standards in line with this change. Despite this, national standards for arsenic in most Asian countries (except Japan and Vietnam) remain at 50 µg L-1, in line with the pre-1993 WHO guideline value. This is largely a consequence of analytical constraints and, in some countries, of difficulties with compliance to a lower standard.

World Distribution of High-Arsenic Groundwaters

The concentrations of arsenic in most groundwaters are low, typically less than the WHO guideline value of 10 µg L-1 and commonly below analytical detection limits. An investigation of some 17,500 groundwater samples from public supply wells in the United States of America, for example, found that 7.6% exceeded 10 µg L-1 and 1% exceeded 50 µg L-1, while 64% contained <1 µg L-1 (Focazio and others 1999). Despite the usually low abundance in water, high 28 29 concentrations can occur in some groundwaters. Under geochemically and hydrogeologically favorable conditions concentrations can reach tens to hundreds of µg L-1 and, in a few cases, can exceed 1 mg L-1.

Most of the world's high-arsenic groundwater provinces result from natural processes involving interactions between water and rocks. Some of the highest concentrations of arsenic are found in sulfide and oxide minerals, especially iron sulfides and iron oxides. As a result, high arsenic concentrations in water are often found where these minerals are in abundance. Mineralized areas are well-documented examples. These contain ore minerals, including sulfide minerals, typically as veins or replacements of original host rocks and result from past infiltration of hydrothermal fluids. In mineralized areas, rates of mineral dissolution can be enhanced significantly by mining activity and arsenic contamination can be particularly severe in water associated with mine wastes and mine drainage. Some geothermal waters also contain high arsenic concentrations. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

A map of the distribution of documented cases of arsenic contamination in groundwater and the environment is given in figure 1. Many of these cases are related to areas of mineralization and mining activity and a few are associated with geothermal sources. While these cases can be severe with often high concentrations of arsenic in waters, sediments, and soils, the scale of contamination is usually not of large lateral extent. This is due to the normally strong adsorption capacity of iron oxides, which leads to removal of arsenic and other potentially toxic trace elements from water.

Despite these associations, other areas with recognized high-arsenic groundwaters are not associated with obvious mineralization or geothermal activity. Some of these occur in major aquifers and may be potentially much more serious because they occupy large areas and can provide drinking water for large populations. Unlike mining and geothermal areas, they are also more difficult to detect without chemical analysis of the groundwater. Several aquifers around the world have now been identified with unacceptably high concentrations of arsenic. These include aquifers in parts of Argentina, Chile, Mexico, southwest United States, Hungary, Romania, Bangladesh, India, China (including Taiwan), Myanmar, Nepal, and Vietnam (figure 1). Many differences exist between these regions, but some similarities are also apparent. The majority of the high-arsenic groundwater provinces are in young unconsolidated sediments, usually of Quaternary age, and often of Holocene (<12,000 years) age. These aquifers are usually large inland closed basins in arid or semiarid settings (for example Argentina, Mexico, southwest United States) or large alluvial and deltaic plains (for example Bengal delta, Yellow River plain, Irrawaddy delta, Red River delta). These aquifers do not appear to contain abnormally high concentrations of arsenic-bearing minerals but do have geochemical and hydrogeological conditions favorable for mobilization and retention in solution.

Figure 1. Summary of the World Distribution of Documented Problems with Arsenic in Groundwater and the Environment

Source: Modified after Smedley and Kinniburgh 2002. Note: In China, arsenic has further been identified in the provinces of Jilin, Qinghai, Anhui, Beijing, and Ningxia (reported at Regional Operational Responses to Arsenic Workshop in Nepal, 26–27 April 2004). In India, further affected states are Assam, Arunachal Pradesh, Bihar, Manipur, Meghalaya, Nagaland, Uttar Pradesh and Tripura.

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2. Arsenic Distribution in South and East Asia

Overview any of the world's aquifers with recognized arsenic problems are located in Asia where Mlarge alluvial and deltaic plains occur, particularly around the perimeter of the Himalayan mountain range (figure 2). This section gives an account of the occurrence and scale of groundwater arsenic problems in countries where such problems have been identified. There may be other Quaternary aquifers with high groundwater arsenic concentrations that have not yet been identified, but since awareness of the arsenic problem has grown substantially over the last few years, these are likely to be on a smaller scale than those already identified.

The information in this section has been compiled from published literature, as well as various unpublished reports and websites. Many of the unpublished data are difficult to access and reports typically not peer reviewed. Data for many countries also lack spatial information,

Figure 2. Map of South and East Asia Showing the Locations of Documented High-Arsenic Groundwater Provinces

30 31

Source: Modified after Smedley 2003. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

particularly georeferenced sample points. Reporting often merely gives an indication of whether an area is or is not affected, rather than an account of percentages of affected wells in a given area. In some cases, the quality of analytical data is also uncertain (box 1). These uncertainties make it difficult to assess the scale of arsenic problems in many parts of South and East Asia. Nonetheless, the information available has been brought together to provide a critical assessment of the current state of knowledge of the scale of groundwater contamination of the aquifers in Asia and to detail where apparent data gaps exist. A summary of the recognized occurrences, aquifers involved, and populations potentially at risk (that is, using drinking water with arsenic concentrations >50 µg L-1) is given in table 1. Some of these population statistics are poorly constrained given the present state of knowledge.

Box 1. Analysis of Arsenic

Arsenic is a trace element that is present at µg L-1 concentrations in most natural waters. Sampling and analyzing such small concentrations is not a trivial task and there have been many examples in recent years where faulty analysis has led to dubious conclusions. All surveys require a planned and maintained quality assurance program to ensure that data produced are of good quality throughout the program. This includes adequate record-keeping, sample tracking, regular use of analytical standards, interlaboratory (round robin) checks, and duplicate analyses.

The most precise and sensitive analytical methods depend on sophisticated laboratory instruments such as hydride generation-atomic absorption spectrometry (HG-AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and hydride generation-atomic fluorescence spectrometry (HG-AFS). The use of HG-AAS has expanded in recent years, but many developing countries do not have such sophisticated facilities or have difficulty maintaining them, especially on the scale required. Costs of analysis by these techniques are typically in the range US$10–20 per sample. The HG-AAS and HG-AFS methods are at the cheaper end of this range, but the more expensive ICP methods are multielement techniques and so provide information on elements other than arsenic. There are cheaper and more robust instruments, such as that employed by the silver diethyldithiocarbamate (SDDC) method, but these are less sensitive, are slow, and may not be appropriate for large screening programs. Field test kits have therefore been widely used as a primary source of data in many surveys, with laboratory methods used for checking some of the results. Field test kits are relatively simple and inexpensive, usually costing less than US$1 per sample for the materials. The early kits were insufficiently sensitive (being barely capable of detecting less than 100 µg L-1). However, they have improved in the last few years and the best can now detect down to 10 µg L-1, the WHO guideline value. In practice, the reproducibility of the kits has often proven disappointing and care has to be taken to ensure that good results are obtained consistently during a survey (Rahman and others 2002).

As a result of the relatively large errors involved in arsenic analysis, especially with field test kits, it is inevitable that some wells will be misclassified as "safe" when they are not, and vice versa. Procedures should be in place to assess the scale and significance of these misclassifications and to minimize their impact, for example by reanalyzing samples that are very different from those taken from neighboring wells. The reliability of the kits increases for concentrations well above the drinking water standard or guideline and so they tend to be more reliable at detecting the most toxic waters.

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Alluvial, Deltaic, and Lacustrine Plains

Bangladesh Of the regions of the world with groundwater arsenic problems Bangladesh is the worst case identified, with some 35 million people thought to be drinking groundwater containing arsenic at concentrations greater than 50 µg L-1 (table 1) and around 57 million drinking water with concentrations greater than 10 µg L-1 (Gaus and others 2003). The large scale of the problem reflects the large area of affected aquifers, the high dependence of Bangladeshis on groundwater for potable supply, and the large population in the fertile lowlands of the Bengal basin. Today, there are an estimated 11 million tubewells in Bangladesh serving a population of around 133 million people (2002 estimate). The scale of arsenic contamination in Bangladesh means that it has received by far the greatest attention in terms of groundwater testing and more is known about the arsenic distribution in the aquifers than in any other country in Asia (as well as most of the developed world). However, much more testing is still required.

Several surveys of arsenic in Bangladesh groundwater have been carried out over the last few years, both by laboratory and field methods. The Bangladesh Department of Public Health Engineering (DPHE) and the United Nations Children's Fund (UNICEF) carried out surveys of

Table 1. Summary of the Distribution, Nature, and Scale of Documented Arsenic Problems (>50 µg L-1) in Aquifers in South and East Asia

Location Areal extent (km2) Population at riska Arsenic range (µg L-1)

Alluvial/deltaic/ lacustrine plains Bangladesh 150,000 35,000,000 <1-2,300 32 33 China (Inner Mongolia, Xinjiang, Shanxi) 68,000 5,600,000 40-4,400 India (West Bengal) 23,000 5,000,000 <10-3,200 Nepal 30,000 550,000 <10-200 Taiwan (China) 6,000 (?) 10,000b 10-1,800 Vietnam 1,000 10,000,000c 1-3,100 Myanmar (?) 3,000 3,400,000 - Cambodia (?) <1,000 320,000d - Pakistan - - -

- Not available. a Estimated to be drinking water with arsenic >50 µg L-1. From Smedley 2003 and data sources therein. b Before mitigation. c United Nations Children's Fund (UNICEF) estimate. d Maximum. Source: World Bank Regional Operational Responses to Arsenic Workshop in Nepal, 26-27 April 2004. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

51,000 wells during 1997-1999 using arsenic field test kits. The British Geological Survey (BGS) and the DPHE conducted a survey of around 3,500 samples nationwide during 1998-1999 (BGS and DPHE 2001). Over the last few years, the Bangladesh Arsenic Mitigation Water Supply Project (BAMWSP) and a number of nongovernmental organizations (NGOs) and international agencies (for example the Japan International Cooperation Agency (JICA), the Asian Arsenic Network (AAN), NGO Forum, UNICEF, World Vision International, and Watsan Partnership) have carried out major screening programs of groundwaters across Bangladesh. Van Geen, Zheng, and others (2003) also analyzed samples from about 6,000 wells in eastern Bangladesh. To date more than 4.2 million tubewells have been tested for arsenic. However, this is still only around 39% of the wells in the country.

High-Arsenic Shallow Aquifers The aquifers affected by arsenic are Quaternary, largely Holocene, alluvial and deltaic sediments associated with the Ganges-Brahmaputra-Meghna river system. These occur as the surface cover over a large part of Bangladesh. Groundwater from the Holocene aquifers contains arsenic at concentrations up to around 2,300 µg L-1, though concentrations span more than four orders of magnitude (BGS and DPHE 2001). Van Geen, Zheng, and others (2003) found concentrations in the range <5-860 µg L-1 in groundwaters from Araihazar, east of Dhaka.

Several surveys of the groundwater have shown a highly variable distribution of arsenic, both laterally and with depth. This means that predictability of arsenic concentrations in individual wells is poor and each well used for drinking Figure 3. Smoothed Map of Arsenic water needs to be tested. Nonetheless, on a Distribution in Groundwater from regional scale, trends are apparent, and the Bangladesh worst-affected areas with the highest average arsenic concentrations are found in the southeast of the country, to the south of Dhaka (figure 3). Here, in some districts, more than 90% of shallow tubewells tested had arsenic concentrations >50 µg L-1. Some areas with low overall arsenic concentrations have localized hotspots with locally high arsenic concentrations. That of the Chapai Nawabganj area of western Bangladesh is a notable example (figure 4 see page 34), where the median concentration in groundwater from Holocene sediments was found to be 3.9 µg L-1 but with extremes up to 2,300 µg L-1 concentrated in a small area of around 5 x 3 km. Overall, the BGS and DPHE survey of shallow groundwaters found that 27% exceeded 50 µg L-1 and 46% exceeded Note: Samples are from tubewells <150 m deep. -1 Source: BGS and DPHE 2001. 10 µg L .

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Figure 4. Maps of the Distribution of Arsenic in Shallow Groundwater from the Chapai Nawabganj Area, Northwest Bangladesh

Note: Samples are from tubewells <150 m deep Source: BGS and DPHE 2001.

Investigation of the depth ranges of affected tubewells suggests that concentrations are low in groundwater from the top few meters of the aquifers close to the water table, but that they 34 35 increase markedly over a short depth range. This is demonstrated by the profile of groundwater compositions in a piezometer (10 cm diameter, 40 m deep) in Chapai Nawabganj, northwest Bangladesh. Arsenic concentration was relatively low (17 µg L-1) at 10 m depth but increased to values in the range 330-400 µg L-1 over the depth interval 20-40 m (BGS and DPHE 2001) (figure 5).

The largest range and highest concentrations of arsenic are typically found at around 15-30 m depth below surface, although the depth ranges of the peaks vary from place to place. Table 2 shows the frequency distribution of arsenic concentrations with depth for all analyzed samples from the BGS and DPHE (2001) survey.

Investigation of other elements of potential health concern reveals that concentrations of manganese are often greater than the WHO health-based guideline value of 0.5 mg L-1 and concentrations of uranium are also sometimes high (up to 32 µg L-1). Concentrations of boron exceed WHO guidelines in some saline groundwaters from the south and east of Bangladesh. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Figure 5. Variation in Concentration of Arsenic and Other Elements with Depth in a Purpose- Drilled Piezometer in Chapai Nawabganj, Northwest Bangladesh

0 0 0 0 0 Water level

10 10 10 10 10

20 20 20 20 20

Well depthWell (m) 30 30 30 30 30

40 40 40 40 40

0 60 120 1000 1200 0 200 400 0 5 10 15 0 5 10

-1 -1 -1 -1 Eh (mV) SEC (µS cm ) AsT (µg L ) FeT (mg L ) SO4 (mg L )

Source: BGS and DPHE 2001.

Table 2. Frequency Distribution of Arsenic in Groundwater from Tubewells from Quaternary Alluvial Aquifers in Bangladesh

Tubewell depth Number of samples (%) Total samples range (m)a <10 µg L-1 10-50 µg L-1 >50 µg L-1

<25 597 (53) 193 (17) 327 (30) 1,117 25-50 740 (57) 211 (16) 354 (27) 1,305 50-100 363 (55) 143 (22) 153 (23) 659 100-150 33 (26) 47 (37) 46 (37) 126 150-200 25 (78) 6 (19) 1 (3) 32 >200 286 (97) 7 (2) 2 (1) 295 a Depth of intake of groundwater is difficult to determine and may be from several horizons at differing depths. Source: BGS and DPHE 2001.

Nitrate concentrations are normally low, as are most other trace elements on the WHO list of elements considered detrimental to health. Concentrations of iron and ammonium are often high but these are issues of acceptability on aesthetic grounds rather than health considerations.

Low-Arsenic Aquifers The BGS and DPHE (2001) map (figure 3) demonstrates the low overall arsenic concentrations of groundwater from coarser sediments in the Tista Fan of northern Bangladesh. Low concentrations are also found in groundwaters from aquifers in the older (Pleistocene) uplifted plateaux of the Barind and Madhupur tracts (north-central Bangladesh). These usually have concentrations less than 10 µg L-1 and often significantly less. Similar results for these areas have also been obtained by other workers (for example van Geen, Zheng, and others 2003).

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Groundwater from these areas is therefore expected to be normally safe from the point of view of arsenic, although concentrations of other elements, notably iron and manganese, may be high.

Arsenic concentrations also appear to be mostly low in groundwater from older ("deep") aquifers which occur in some areas below the Holocene deposits. The stratigraphy of the deep aquifers of Bangladesh is poorly understood at present, but where studied, the aquifers with low-arsenic groundwater appear to be of Pleistocene age (BGS and DPHE 2001; van Geen, Zheng, and others 2003). Limited investigations indicate that they are mineralogically distinct from the overlying Holocene deposits. They are typically more brown in color and relatively oxidized. The deep aquifer sediments are likely to be akin to the aquifers below the Barind and Madhupur tracts, which occur at shallower depths because of tectonic uplift.

Although these sediments are often referred to as the "deep aquifer", the definition of "deep" varies from place to place and between organizations and the subject has become rather confused (box 2). However, depth ranges for the low-arsenic groundwater are usually at least 100-200 m. Recent data produced by the BAMWSP for groundwater samples from 60 upazilas across Bangladesh found that out of 7,123 samples from tubewells >150 m deep, 97% had arsenic concentrations <50 µg L-1 (percentage <10 µg L-1 unspecified; BAMWSP website). The

Box 2. Shallow versus Deep Aquifers

It has been observed that groundwater from deep Quaternary aquifers in the Bengal basin (Bangladesh and West Bengal) has low or very low concentrations of arsenic, often much less than 5 µg L-1. The depth at which these deep aquifers occur varies but is typically more than 100–150 m below surface. Deep aquifers have been tapped in southern coastal areas and northeastern Bangladesh for some time but less so in other areas and their stratigraphy, lithology, and areal extent are often poorly defined. They are often said to be more oxic than the younger overlying deposits with a higher proportion of brown iron oxides. As older formations, they are also likely to have been better flushed by groundwater than the overlying young sediments as a result of 36 37 increased groundwater gradients and more active water movement during past ice ages. As sources of low-arsenic groundwater, these deep aquifers could provide drinking water for affected populations in the region. More research is needed, however, to establish whether they would be secure from the effects of downward leakage of high-arsenic water (or saline water in coastal areas), given significantly increased groundwater abstraction.

In other regions of South and East Asia, groundwater from deep Quaternary aquifers does not always have low arsenic concentrations. In Inner Mongolia, concentrations of arsenic up to 310 µg L-1 have been found in groundwater from wells more than 100 m deep in an area where a shallow aquifer (less than 30 m deep) also has high groundwater arsenic concentrations. The lithology and stratigraphy of the deep aquifer are poorly characterized. However, it is clear from the comparisons that groundwater arsenic concentration is not a simple function of aquifer or well depth. Rather, aquifer geology and groundwater flow history are important controlling factors. Observations show that a good understanding of the hydrogeology and geochemistry of Quaternary alluvial, deltaic, and lacustrine aquifers is needed before significant groundwater development should be allowed to take place. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

BGS and DPHE (2001) national survey categorized shallow aquifers as those less than <150 m depth and deep aquifers as >150 m. Of 335 samples analyzed from >150 m depth, 95% were found to have arsenic concentrations <10 µg L-1 (table 2). Most of the deep groundwater samples analyzed in the BGS and DPHE survey were from the southern coastal area (Barisal) and the northeast (Sylhet). In these areas, the shallow and deep aquifers appear to be separated by thick deposits of clay, which afford some hydraulic separation between the two. By contrast, in a local study of groundwater in Faridpur area of central Bangladesh, BGS and DPHE (2001) defined the deep aquifer as being greater than 100 m, based on the occurrence of sandy sediments and well depths. Here the deeper aquifer was found not to be well separated from the shallower aquifer and a degree of hydraulic connection between the two is therefore possible (BGS and DPHE 2001). Chemical analysis of samples from Faridpur revealed arsenic concentrations up to 52 µg L-1 (five samples) in groundwater from >100 m depth. Closer investigation of the wells with higher concentrations also showed that they were sometimes screened at multiple levels and hence took in water from various horizons.

Van Geen, Zheng, and others (2003) also found consistently lower arsenic concentrations at greater depth in the Araihazar area east of Dhaka. Here the low concentrations were found at depths as shallow as 30 m, although the range of the low-arsenic deep aquifer varied between 30 m and 120 m. There is some question over whether the deep aquifer at 30 m results from uplift of the sediments, as the study area is on the eastern edge of the Madhupur tract.

The results clearly indicate that the depth of safe aquifers varies in different parts of Bangladesh and it is not possible to define the depth at which low-arsenic water will occur, even assuming a deep aquifer exists in all areas. The variable depths are perhaps not surprising given the heterogeneity of sediments in the basin and complexities introduced by past tectonic movements. The important criterion for determining the groundwater arsenic concentrations is the sediment type and sediment history rather than depth.

From available data, it also appears that concentrations of manganese and uranium are lower in the groundwater from the deeper aquifer (BGS and DPHE 2001). Concentrations of most other analyzed trace elements were also within acceptable ranges.

Although a number of studies have been and are being carried out on the Bangladesh deep aquifers, much remains unknown about their distribution across the country, the degree of hydraulic separation from the shallow high-arsenic aquifers, and their viability as a long-term source of water. Questions also remain about why higher arsenic concentrations occur in some samples. Possibilities include drawdown from shallow levels due to hydraulic connection, drawdown via wells due to poor sealing, multiple screening of wells in both aquifers, or in situ high-arsenic groundwater in some parts of the deep aquifer. These questions are critical to the future potential of the deep aquifers for water supply and need further assessment before development of these aquifers takes place on a large scale.

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Dug Wells A number of studies have concluded that arsenic concentrations in shallow dug wells in Bangladesh are usually low, even in areas where tubewells have high concentrations (box 3). Concentrations are generally <50 µg L-1, with most being <10 µg L-1 (for example Chakroborti 2001). BGS and DPHE (2001) found concentrations in five dug wells from north-west Bangladesh (Chapai Nawabganj) in the range <3-14 µg L1 , with a median of 7.6 µg L-1. Two samples exceeded 10 µg L-1, albeit by a small margin. However, these were from an area with lower overall groundwater arsenic concentrations than the worst-affected parts of the country. Little difference was observed in the samples between concentrations in filtered and unfiltered aliquots and the concentrations were therefore considered to be largely dissolved. Concentrations of uranium up to 47 µg L-1, manganese up to 1.7 mg L-1 , and nitrate-N up to

Box 3. Dug Wells

Concentrations of arsenic in dug wells are often low, even in areas where those in groundwater from neighboring tubewells are high. In western Bangladesh, a 30 m deep tubewell with a groundwater arsenic concentration of around 2,300 µg L-1 is located just a few meters from an 8 m deep dug well with an arsenic concentration of less than 4 µg L-1. Groundwater in the top few meters below the water table is likely to be relatively aerobic because of recent inputs of rainfall and more active groundwater movement. However, it is most likely that the tendency for low arsenic concentrations in dug wells relates in large part to their large diameter and openness to atmosphere compared to tubewells.

Despite the tendency for low arsenic concentrations in dug well waters, not all are found to be below acceptable limits. Several dug wells from the Bengal basin have been found with concentrations greater than the WHO guideline value of 10 µg L-1. Worse, in parts of Inner Mongolia where tubewell water has high concentrations, groundwater from dug wells has been found with concentrations up to 560 µg L-1. The concentration of arsenic in dug wells is probably largely controlled by the redox conditions in the wells; where anaerobic conditions can be maintained, arsenic concentrations may be unacceptably high. Concentrations may also be high where locally 38 39 influenced by mining wastes. The concentrations of arsenic in dug wells can therefore not always be guaranteed to be low, and testing for arsenic needs to be carried out to assess their safety for potable purposes.

Additional problems from dug wells occur because of their shallow depths. They can be at increased risk from contamination by surface pollutants, including pathogenic bacteria, and will generally require disinfection before use. Enclosure of the well and adding a handpump may also be necessary. Restricted yields and seasonal drying up of wells are additional problems affecting their usefulness in some areas.

In many parts of South and East Asia, dug wells have been superseded over time by handpumped tubewells as a means of obtaining improved yields and sanitary protection. Nonetheless, they are still used by significant numbers of people, and in some areas they provide an alternative to high- arsenic tubewell water. In Bangladesh around 1.3 million people are estimated to be dependent on dug wells for drinking water (Ahmed and Ahmed 2002), though not all of these draw water from the unconsolidated sediments of the Bengal basin. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

28 mg L-1 were found in the dug wells from the region, all of which exceed current WHO health- based guideline values. Bacterial counts in dug wells are also often high.

Bengal Delta and Associated Aquifers, India Problems with arsenic in groundwater in West Bengal were first recognized in the late 1980s and the health effects are now reasonably well documented. Today, it is estimated that more than 5 million people in the state are drinking water with arsenic concentrations greater than 50 µg L-1 (table 1). More recently, problems have also been found in Arunachal Pradesh, Assam, Bihar, Nagaland, Manipur, Meghalaya, Tripura, and Uttar Pradesh. The state of Mizoram also has important Quaternary sedimentary aquifers that are potentially at risk from high groundwater arsenic concentrations. Recent findings of health problems in the village of Semria Ojha Patti in Bihar prompted a survey of groundwater arsenic concentrations. Of 206 tubewells tested, 57% exceeded 50 µg L-1 and 20% exceeded 300 µg L-1. Concentrations were up to 1,650 µg L-1 (Chakraborti and others 2003). Associated health problems are also severe, with skin lesions reported to be prevalent in 13% of adults and 6.3% of children and neurological problems in 63% of adults. As the water samples were collected from villages with identified health problems, the concentrations represent worst cases and the statistics are unlikely to be representative of the arsenic concentrations in the state as a whole.

More than 100,000 groundwater arsenic analyses have apparently been determined for West Bengal. Despite this, there still appears to be a lack of detailed maps of arsenic to assess the spatial distribution. Worst-affected districts have been identified but the distributions on a larger scale (within districts) are not clear and it is thought that no point source maps of groundwater arsenic concentrations have been produced. The scale of the problem in other states with similar geology (Tripura, Bihar, Uttar Pradesh, Meghalaya, Mizoram) is also not known.

The affected aquifers of the region are mainly Holocene alluvial and deltaic sediments similar to those of large parts of Bangladesh. In West Bengal, they form the western margins of the Bengal basin. High arsenic concentrations have been identified in groundwaters from some tubewells in up to eight districts of West Bengal, the five worst affected being Malda, Murshidabad, Nadia, 24 North Parganas, and 24 South Parganas (figure 6 see page 40). These cover around 23,000 km2 to the east of the Bhagirathi-Hoogli river system. Arsenic concentrations have been found in the range <10-3,200 µg L-1 (table 1; CGWB 1999). At the time of writing, no data on arsenic concentrations in groundwater from Chinsurah District are available. Groundwaters from the laterite upland in the western part of West Bengal, as well as the Barind and Ilambazar formations, the valley margin fan west of the Bhagirathi River, and the lower delta plain and delta front have low groundwater arsenic concentrations (PHED 1991).

The Quaternary sediment sequence increases in thickness southwards (CGWB 1999). Sedimentation patterns vary significantly laterally, but sands generally predominate to a depth of 150–200 m in Nadia and Murshidabad, while the proportion of clay increases southwards into 24 North and South Parganas, as does the thickness of surface clay (Ray 1997).

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

Figure 6. Map of West Bengal Showing Districts Affected by High Groundwater Arsenic Concentrations

Note: Numbers refer to number of blocks with arsenic concentrations >50 µg L–1 relative to total number of blocks. Darker shading shows worst-affected areas (data as of 1999).

The Quaternary sediments have a similar configuration to those of Bangladesh but the aquifers have been categorized slightly differently. A shallow "first aquifer" has been described at 12–15 m depth, with an intermediate "second aquifer" at 35–46 m, and a deep "third aquifer" at 40 41 around 70–90 m depth (PHED 1991). High arsenic concentrations occur in groundwater from the intermediate second aquifer. Shallowest groundwaters (first aquifer) appear to have low concentrations, presumably because many (though not necessarily all) of the sources abstracting from this depth are open dug wells and are likely to contain groundwater that is oxidized through exposure to the atmosphere. Groundwaters from the deep aquifer also have low arsenic concentrations, except where only a thin clay layer separates it from the overlying aquifer, allowing some hydraulic connection between them. CGWB (1999) noted that the depths of arsenic-rich groundwaters vary in the different districts but where high-arsenic groundwaters exist, they are generally in the depth range of 10–80 m. As with Bangladesh, therefore, the groundwater arsenic concentration ranges appear to show a bell-shaped curve with depth.

As with Bangladesh, the distribution of arsenic concentrations in the groundwaters is known to be highly variable. Some particularly high concentrations (>200 µg L-1) have been found in groundwaters from 24 South Parganas, along the international border of 24 North Parganas, and in eastern Murshidabad (Acharyya 1997; CSME 1997). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Terai Region, Nepal Groundwater is abundant in the Quaternary alluvial sediments of the lowland Terai region of southern Nepal and is an important resource for domestic and agricultural use. The region is estimated to have around 800,000 tubewells, which supply groundwater for some 11 million people (World Bank Regional Operational Responses to Arsenic Workshop, Nepal, 26–27 April 2004). About 15% of these wells were supplied by government agencies or NGOs, the rest being private wells. Many have been installed within the last decade. Groundwater is also used for irrigation; these wells generally abstract from deeper levels than those used for drinking water.

Both shallow and deep aquifers occur throughout most of the Terai region, although the thickness of sediments deposited is significantly less than found in Bangladesh. The shallow aquifer appears to be mostly unconfined and well developed, although it is thin or absent in some areas (Upadhyay 1993). The deep aquifer (precise depth uncertain) is artesian. Quaternary alluvium also infills several intermontane basins in Nepal, most notably that of the Kathmandu valley of central Nepal (ca. 500 km2), where sediment thickness reaches in excess of 300 m (Khadka 1993). Recent heavy abstraction of groundwater in the Kathmandu valley has resulted in falling groundwater levels (Tuinhof and Nanni 2003).

A number of surveys of groundwater quality in the Terai region have revealed the presence of arsenic at high concentrations in some shallow tubewells (<50 m depth), though most of those analyzed appear to have <10 µg L-1. Arsenic-related health problems have been detected in some of the affected areas. Water analyses have mostly been determined (using HG-AAS) by four private laboratories in Nepal, with additional analyses from four government laboratories (Tuinhof and Nanni 2003).

The most recent water quality statistics were compiled by the National Arsenic Steering Committee (NASC), set up in 2001 to oversee and coordinate national arsenic testing and mitigation (Neku and Tandukar 2003; Tuinhof and Nanni 2003; Shrestha and others 2004). As of September 2003, some 25,000 water analyses of arsenic had been carried out and results indicate that 69% of groundwaters sampled had arsenic concentrations less than 10 µg L-1, while 31% exceeded 10 µg L-1, and 8% exceeded 50 µg L-1 (Tuinhof and Nanni 2003; Shrestha and others 2004). Worst affected were the districts of Rautahat, Bara, Parsa, Kapilbastu, Nawalparasi, Rupandehi, Banke, Kanchanpur, and Kailali of central and western Terai. The highest concentration observed (Rupandehi District) was 2,600 µg L-1 (Shrestha and others 2004).

Results from earlier surveys (table 3) show similar overall statistics to the more recent summary. The Nepal Department of Water Supply and Sewerage (DWSS) carried out a survey of some 4,000 tubewells from the 20 Terai districts, mostly analyzed by field test kits but with laboratory replication of some analyses. Results from the survey indicated that 3.3% of the samples had arsenic concentrations of >50 µg L-1 (Chitrakar and Neku 2001). The highest observed concentration was 343 µg L-1 (Parsa District). From testing in

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 3. Frequency Distribution of Arsenic Concentrations in Analyzed Groundwater Samples from Nepal

Agency Number of samples (%) Total samples <10 µg L-1 10-50 µg L-1 >50 µg L-1

DWSS 3,479 (89.3) 289 (7.3) 128 (3.3) 3,896 NRCS 2,206 (79) 507 (18) 77 (3) 2,790 Finnida 55 (71) 14 (18) 9 (12) 78 Tandukar 54 (61) 27 (30) 8 (9) 89 NASC (2003) 17,300 (69) 6,000 (23) 2,000 (8) 25,000

Sources: Chitrakar and Neku 2001; Tandukar 2001; Neku and Tandukar 2003.

17 of the 20 Terai districts, the Nepal Red Cross Society (NRCS) also found 3% of groundwater sources sampled having concentrations above 50 µg L-1, the highest observed concentration being 205 µg L-1. The spatial distribution of the worst-affected areas was found to be similar to that reported by Chitrakar and Neku (2001). A Finnida survey found 12% of analyzed samples exceeding 50 µg L-1, while a survey by Tandukar found 9% of samples exceeding this value (table 3). The highest arsenic concentrations observed by Tandukar (2001) were around 120 µg L-1, most of the high-arsenic samples being from the River Bagmati area. The high arsenic concentrations occur in anaerobic groundwaters and are often associated with high concentrations of dissolved iron (Tandukar 2001). The percentage of samples exceeding 50 µg L-1 is generally small and much lower than the percentage observed in, for example, Bangladesh, but the statistics nonetheless indicate a clear requirement for further testing and remedial action. To date, there has been no substantial mitigation program in the region (Tuinhof and Nanni 2003).

42 43 Surveys appear to indicate that deeper tubewells in the Terai region have lower arsenic concentrations. As with Bangladesh, variation in arsenic concentration with depth appears to show a general bell-shaped curve. The largest variation and highest maximum concentrations occur in tubewells with depths in the 10–30 m range. Concentrations are generally <50 µg L-1 at depths greater than around 50 m (Shrestha and others 2004). Recent analysis of groundwater from 522 irrigation wells with depths of >40–50 m were also found to have low concentrations (Tuinhof and Nanni 2003). This suggests that the deep aquifer offers some possibilities as an alternative source of low-arsenic water supply. However, as with Bangladesh, the susceptibility of groundwater from the deep aquifer to drawdown of high-arsenic water from overlying sediments is a matter for concern and further hydrogeological investigation.

At the time of writing, around 13% of wells thought to exist in the Terai region have been tested for arsenic. Data so far available from the Kathmandu valley have revealed no arsenic problems there, although the extent of testing in the valley is not clear. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Irrawaddy Delta, Myanmar As elsewhere in Asia, traditional sources of water for domestic supply in Myanmar were dug wells, ponds, springs, and rivers. However, in the Quaternary aquifer of the Irrawaddy delta, many of these have been superseded since 1990 by the development of shallow tubewells. It is estimated that more than 400,000 wells exist in Myanmar as a whole, more than 70% of which are privately owned. Little testing for arsenic in groundwater has been carried out in tubewells from the alluvial aquifer, though a few reconnaissance surveys have been undertaken and arsenic has been found in excess of 50 µg L-1 in some. Save The Children reported from analysis of 1,912 shallow tubewells in four townships in Ayeyarwaddy Division (southern delta area) that 22% of samples exceeded 50 µg L-1. The United Nations Development Programme (UNDP) and the United Nations Centre for Human Settlements (UNCHS) detected arsenic at concentrations greater than 50 µg L-1 in 4% of samples (125 samples) from Nyaungshwe in Shan State in southern Myanmar (UNDP-UNCHS 2001). The Water Resources Utilization Department (WRUD) carried out a survey of groundwater in Sittway township in the western coastal area, and in Hinthada and Kyaungkone townships close to the south coast of Myanmar (WRUD 2001). In Sittway township, salinity problems occur in some groundwaters and surface waters and most tubewells are less than 15 m deep as a result. Merck field test kits were used for the analysis of arsenic. In Hinthada and Kyaunkone townships well depths are typically around 30–50 m, although some deeper tubewells (55–70 m) were also sampled. In the southern townships of the delta area, high iron concentrations were noted. The distribution of arsenic concentrations determined by 2001 is given in table 4. Exceedances above 50 µg L-1 in shallow tubewells from Sittway, Hinthada, and Kyaunkone townships were around 10-13%. One sample from the depth interval 56-70 m also exceeded 50 µg L-1. As with a number of other affected aquifers, dug wells from the WRUD survey generally had arsenic concentrations of <10 µg L-1 (WRUD 2001).

Table 4. Frequency Distribution of Arsenic Concentrations in Groundwaters from the Alluvial Aquifer of Myanmar

Township Well type Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Sittway STW 17 (29.3) 35 (60.3) 6 (10.3) 58 DW 22 (96) 1 (4) 0 (0) 23 Hinthada STW 56 (68.3) 15 (18.3) 11 (13.3) 82 DW 6 (75) 1 (12.5) 1 (12.5) 8 Kyaungkone STW 48 (80) 5 (8) 7 (12) 60 DW 21 (95) 1 (5) 0 (0) 22 DTW 1 (33.3) 1 (33.3) 1 (33.3) 3

Key: STW shallow tubewell DW dug well DTW deep tubewell (55–70 m) Source: WRUD 2001.

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More recent results from WRUD surveys have shown 15% of groundwater samples exceeding 50 µg L-1 (8,937 analyses by April 2002). In these, dug wells were found to exceed 50 µg L-1 in 8% of samples. As the analyses from the various surveys were carried out using Merck field test kits, the accuracy of the results is uncertain but likely to be limited. As with many other areas, the arsenic concentrations of the groundwaters of Myanmar have not been mapped in detail and investigations are in the reconnaissance stages. However, the divisions of Ayeyarwaddy and Bago (delta area), and the states of Mon and Shan, appear to be the worst affected.

Quaternary Aquifers, Taiwan, China Health problems experienced in Taiwan have been the subject of much research since their initial discovery in the early 1960s and have formed the basis of many epidemiological risk assessments over the last 30 years. Taiwan is the classic area for the identification of blackfoot disease (for example Tseng and others 1968; Chen and others 1985) and other peripheral vascular disorders, but many other arsenic-related diseases have also been described from the area.

Despite being under considerable international scrutiny from an epidemiological perspective over the last 40 years or so, there appears to have been little effort to understand the distribution or causes of arsenic problems in the aquifers of Taiwan. As a result, very little information is available for the region. High-arsenic groundwaters have been recognized in two areas: the southwest coastal area (Kuo 1968; Tseng and others 1968) and the northeast coast (Hsu, Froines, and Chen 1997). Kuo (1968) observed arsenic concentrations in groundwater samples from southwest Taiwan ranging between 10 µg L-1 and 1,800 µg L-1 (mean 500 µg L-1, n = 126), with half the samples analyzed having concentrations of 400–700 µg L-1. An investigation by the Taiwan Provincial Institute of Environmental Sanitation found that 119 townships in the affected area had arsenic concentrations in groundwater of >50 µg L-1, with 58 townships having >350 µg L-1 (Lo, Hsen, and Lin 1977). In northeastern Taiwan Hsu, Froines, and Chen (1997) reported an average arsenic concentration of 135 µg L-1 44 45 for 377 groundwater samples. In the southwest, the high arsenic concentrations are found in deep (100-280 m) artesian well waters. The sediments from which these are abstracted are poorly documented, but appear to include deposits of black shale (Tseng and others 1968). The groundwaters are likely to be strongly reducing as the arsenic is found to be present largely as arsenic(III) (Chen and others 1994) and some of the groundwaters contain methane as well as humic substances (Tseng and others 1968). Groundwaters abstracted in northeastern Taiwan are also reported to be artesian but more typically shallow, with a depth range of 16–40 m (Hsu, Froines, and Chen 1997). As found in several other countries, groundwater from shallow dug wells have low arsenic concentrations (Guo, Chen, and Greene 1994). This is probably a reflection of relatively oxidizing conditions in the shallow parts of the aquifer immediately around the open wells.

The arsenic problems of Taiwan are largely historical, as alternative treated surface water supplies have been provided for the affected communities. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Alluvial Plains, Northern China The presence of endemic arsenicosis has been recognized in China since the 1980s and today the scale of the problem is known to be large. Arsenic problems related to drinking water have been identified in Quaternary aquifers in Xinjiang Province and more recently in parts of Inner Mongolia and Shanxi Province (figure 7). Concentrations of arsenic up to 4,400 µg L-1 have been found in groundwater from these affected areas. These areas represent large internal drainage basins in arid and semiarid settings. Groundwater conditions in the arsenic-affected areas appear to be strongly reducing. High-arsenic drinking water has also been identified in parts of Liaoning, Jilin, and Ningxia Provinces in northeast and north-central China (Sun, pers. comm., 2001), although the distribution and extent of these occurrences, the geological associations, and the health consequences are not yet documented or defined. The population exposed to drinking water with concentrations in excess of 50 µg L-1 (the Chinese standard) has been estimated as around 5.6 million (table 1), and the number of diagnosed arsenicosis patients currently around 20,000 (Sun and others 2001). Mitigation measures are being implemented in some areas in China, including where possible the provision of piped low-arsenic surface water and in some cases the use of small-scale reverse osmosis plants. However, so far the mitigation efforts have covered relatively little of the area affected.

Xinjiang Province The first cases of arsenic-related health problems due to drinking water were recognized in Xinjiang Province of northwest China (figure 7). The region is arid with an average annual

Figure 7. Map of China Showing the Distribution of Recognized High-Arsenic (>50 µg L-1) Groundwaters and the Locations of Quaternary Sediments

Source: Modified after Smedley and others 2003.

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precipitation of less than 185 mm. The basin is composed of a 10 km thick sequence of sediments, including a substantial upper portion of Quaternary alluvial deposits. Artesian groundwater has been used for drinking in the region since the 1960s (Wang and Huang 1994). Wang (1984) found arsenic concentrations up to 1,200 µg L-1 in groundwaters from the province. Wang and Huang (1994) found concentrations of between 40 µg L-1 and 750 µg L-1 in deep artesian groundwater from the Dzungaria basin on the north side of the Tianshan Mountains (up to 3,800 m altitude). The region stretches some 250 km from Aibi Lake in the west to Mamas River in the east. Artesian groundwater from deep boreholes (70–400 m) was found to have increasing arsenic concentrations with increasing borehole depth. Highest concentrations were also found in tubewells from the lower section of the alluvial plain. Many of these are believed to abstract groundwater from Quaternary alluvial sediments but whether some of the deeper artesian wells abstract from older formations is not known. Shallow (nonartesian) groundwaters from wells in the depth range 2–30 m had observed arsenic concentrations between <10 µg L-1 and 68 µg L-1 (average 18 µg L-1). That in the saline Aibi Lake was reported as 175 µg L-1, while local rivers had concentrations between 10 µg L-1 and 30 µg L-1.

Wang and others (1997) reported arsenic concentrations up to 880 µg L-1 from tubewells from the Kuitan area of Xinjiang. A 1982 survey of 619 wells showed 102 with concentrations of arsenic >50 µg L-1. High fluoride concentrations were also noted in the groundwaters (up to 21.5 mg L-1).

Shanxi Province Investigations during the mid 1990s showed that arsenic in groundwater from wells in the Datong and Jinzhong basins in Shanxi Province exceeded 50 µg L-1 in 837 (35%) of 2,373 randomly selected samples (Sun and others 2001). Concentrations in Shanyin County, the worst-affected of the regions in Shanxi Province, reached up to 4,400 µg L-1 (Sun and others 2001). 46 47 Yellow River Plain, Inner Mongolia In Inner Mongolia, concentrations of arsenic in excess of 50 µg L-1 have been identified in groundwaters from aquifers in the Hetao plain, Ba Men region, and in the Tumet plain, which includes the Huhhot basin (Luo and others 1997; Ma and others 1999). These areas are also arid, with a mean annual precipitation of around 400 mm. The affected areas border the Yellow River plain and include the towns of Boutou and Togto. In the region as a whole, around 300,000 residents are believed to be drinking water containing >50 µg L-1 (Ma and others 1999). Arsenic-related health problems from the use of groundwater for drinking were first recognized in the region in 1990 (Luo and others 1997). The most common manifestations of disease are skin lesions (melanosis, keratosis) but an increased prevalence of cancer has also been noted. Ma and others (1999) reported that 543 villages in Ba Men region and 81 villages in Tumet had tubewells with arsenic concentrations >50 µg L-1. Around 1,500 cases of arsenic disease had been identified in the area by the mid 1990s. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The Hetao plain comprises a thick sequence of young unconsolidated sediments. In a study of groundwater from the Wuyuan and Alashan areas, Guo and others (2001) found that, respectively, 96% and 69% of samples analyzed had arsenic concentrations greater than 50 µg L-1. Concentrations were generally much higher in groundwater from tubewells (depth range 15–30 m) than from open dug wells (3-5 m depth) and the highest concentration recorded was 1,350 µg L-1.

The area of Ba Men with high-arsenic groundwater appears to be around 300 x 20 km in extent and the sediments are Quaternary lacustrine deposits. Wells were mostly installed in the late 1970s and well depths are typically 10–35 m. Arsenic concentrations have been found in the range 50-1,800 µg L-1 (Ma and others 1999) and around 30% of wells sampled had arsenic concentrations >50 µg L-1. The groundwaters are reducing with arsenic being dominantly present as arsenic(III). Some contain high fluoride concentrations (average 1.8 mg L-1) (Ma and others 1999).

The Huhhot basin (area around 80 x 60 km) lies to the east of the Ba Men area (figure 8). The basin is surrounded on three sides by high mountains of the Da Qing and Man Han ranges and is itself infilled with a thick sequence (up to 1,500 m) of poorly consolidated sediments, largely of Quaternary age (Smedley and others 2003). Groundwater has been used for several Figure 8. Regional Distribution of Arsenic in decades for domestic supply and agriculture. Groundwaters from the Shallow and Deep Traditional sources of water were shallow dug Aquifers of the Huhhot Basin wells that were typically 10 m or less deep and tapped the shallowest groundwater. These have now generally been abandoned in favor of tubewells that abstract at shallow levels (typically <30 m) by handpumps or in some cases by motorized pumps. Groundwater is also present within a distinct, deeper aquifer (typically >100 m depth). Tubewells tapping this deeper aquifer are often artesian in the central parts of the basin.

Arsenic concentrations in the Huhhot basin groundwaters range between <1 and 1,480 µg L-1 in the shallow aquifer (£100 m) and between <1 and 308 µg L-1 in the deep aquifer (>100 m). Of a total of 73 samples, summarized by Smedley and others (2003), 25% of shallow sources and 57% of deep sources have arsenic concentrations in -1 Source: Smedley and others 2003. excess of 50 µg L (table 5 see page 48). The

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 5. Frequency Distribution of Arsenic Concentrations in Groundwater from the Huhhot Basin, Inner Mongolia

Well depth Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

<100 m 35 (59) 9 (15) 15 (25) 59 >100 m 6 (43) 0 (0) 8 (57) 14

Source: Smedley and others 2003.

Table 6. Summary Arsenic Data for Groundwater from Dug Wells in the High-Arsenic Groundwater Region of the Huhhot Basin

Sample Water level Well depth DOC Arsenic m m mg L-1 µg L-1

HB2 1.5 3.5 9.3 560 HB18 2.0 6 - 49 HB58 4.0 8 2.5 <1 HB4 2.0 9 11.4 200

- Not available.

regional distributions of arsenic in the groundwaters from the shallow and deep aquifers are shown in figure 8. Concentrations in the aerobic groundwaters from the basin margins are universally low. High concentrations are generally restricted to the low-lying part of the basin where groundwaters are strongly reducing (table 6) (Smedley and others 2001, 2003). The redox characteristics of the Huhhot basin groundwaters have many similarities with those of Bangladesh and it is logical to conclude that the main geochemical processes controlling 48 49 arsenic mobilization are similar in the two areas.

Of a limited number of samples of dug well water investigated, some are observed to have arsenic concentrations in excess of 50 µg L-1 (Smedley and others 2003). The affected wells are from the part of the aquifer with high concentrations in tubewell waters. This observation contrasts with the situation observed in other reducing groundwater environments such as Taiwan (Guo, Chen, and Greene 1994) and the Bengal basin (Smedley and others 2003). The dug well waters of the Huhhot basin appear to be reducing, with high concentrations of dissolved organic carbon (DOC, up to 11.4 mg L-1). This, together with the fact that low-lying parts of the basin are zones of groundwater discharge, rates of groundwater recharge are low, and groundwater movement is sluggish, are likely reasons for the reducing conditions and stabilization of arsenic in solution (Smedley and others 2003). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Red River Plain, Vietnam Arsenic problems have emerged only recently in the aquifers of the Red River plain of northern Vietnam. Recent suggestions are that arsenic-related health problems are beginning to be identified among the exposed populations of Vietnam, although this is as yet unsubstantiated. The total area of the plain is around 17,000 km2. Groundwater is abstracted from unconsolidated Quaternary alluvial sediments which comprise up to 150 m thickness of sand, silts, clay, and some conglomerates. A superficial aquifer of Holocene sediments is around 10–40 m thick in the centre of the plain but thins to just 1–3 m on the margins (Tong 2002). Underlying Pleistocene sediments form the main aquifer of the region and are around 100 m thick in the centre and southeast of the plain (Berg and others 2001; Tong 2002).

Private tubewells have generally been installed over the last decade and these abstract water via handpumps from shallow levels in the aquifer (<45 m depth). Public supply tubewells in the city of Hanoi abstract from the deeper Pleistocene aquifer (wells around 30–70 m deep). The lower aquifer is heavily pumped and has resulted in a seasonal drawdown of around 30 m around the centre of Hanoi (Trafford and others 1996). Water level drawdown of up to 1 m per year has been observed in some wells in Hanoi (Tong 2002). Drawdown of the shallow aquifer has also occurred but a significant head difference exists between the two aquifers, suggesting that the two are not hydraulically connected (Tong 2002). This appears not to be the case northeast of Hanoi, between the Red River and its tributary the Duong River, where poorly permeable intervening layers between the Holocene and Pleistocene aquifers are thin or absent (Nguyen and Nguyen 2002). Whether hydraulic separation between the aquifers occurs more widely in the plain is not known.

Groundwater is fresh in the upper parts of the plain but becomes more saline as a result of seawater intrusion in the lower reaches. Recent overpumping of the aquifers in the urban areas has also been linked to increasing saline intrusion (Tong 2002). Many of the groundwaters of the region have high iron and manganese concentrations and some also contain high ammonium concentrations (Trafford and others 1996).

Arsenic concentrations in the range 1-3,050 µg L-1 (average 159 µg L-1) were reported by Berg and others (2001) for groundwater from the Hanoi area and surrounding rural areas. In a surveyed area of some 1,000 km2 around Hanoi, they found that the arsenic concentrations were spatially variable, but generally higher to the south of the city on the southern margins of the Red River. Concentrations were found to be high in groundwaters from both the shallow and deeper aquifers, but the extremely high values were found in the shallow groundwater from private tubewells. Groundwater from deeper tubewells had arsenic concentrations up to 440 µg L-1. Subsequent studies by Tong (2002) confirmed the high concentrations south of the city but also found some high concentrations to the west and east of the city. Concentrations were generally lower north of the Red River. Tong reported that from a survey carried out by the Geological Survey of Vietnam together with UNICEF in 1999, 153 samples out of 1,228 (12.5%) in seven provinces had arsenic concentrations greater than 50 µg L-1. An earlier report (Tong 2001) indicated that arsenic

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concentrations are often high in groundwaters from both the Holocene and the underlying Pleistocene aquifers (table 7).

The causes of the spatial variations are not fully clear, but factors may include differences in sediment thickness, composition, and age, and hydraulic connection between layers. In particular, sediments to the north of Hanoi with typically low groundwater arsenic concentrations are predominantly of Pleistocene age and are relatively thin (Berg and others 2001). One uncertainty in the distribution of the arsenic concentrations in the groundwaters of the region is the impact that anthropogenic activity may have had on the mobilization of arsenic. Since some high concentrations have been found close to the city of Hanoi, it is possible that urban wastewater recharge to the aquifer may have had some impact on the arsenic distributions. This remains speculation and requires further investigation.

Berg and others (2001) and Tong (2002) have suggested that significant seasonal variations exist in arsenic concentrations in given wells in relation to strong water level fluctuations. Berg and others (2001) found some very large temporal variations, with often higher concentrations in wells sampled in September (rainy season) than when sampled in December (dry season) or May (early rainy season). By contrast, Tong (2002) reported that more samples tended to exceed the national standard of 50 µg L-1 in the dry season than the rainy season. As the data in the case of Berg and others (2001) were not reported in relation to other parameters (for example rainfall, water level), and in the case of Tong (2002) were presented just as ranges and percentage exceedances, the variations are difficult to interpret and to verify. Subsequent monitoring by the Swiss Federal Institute for Environmental Science and Technology (EAWAG) and others (with more stringent sampling and analytical procedures) has revealed much less temporal variation, the greatest being found in wells close to the river bank (M. Berg, pers. comm., 2004). Results have not yet been documented.

Maps have been produced showing the distribution of arsenic in groundwater in the Hanoi area 50 51 (Berg and others 2001; Tong 2002) but so far mapping of the groundwater quality in the plain as a whole has not been carried out.

Table 7. Summary Arsenic Data for Groundwater from Tubewells in the Red River Plain, Vietnam, Divided into Those from the Holocene and Pleistocene Aquifers

Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Tong (2001) Holocene 117 (45) 62 (24) 81 (31) 260 Tong (2001) Pleistocene 84 (40) 70 (33) 56 (27) 210 Tong (2002) undivided 740 (60.2) 335 (27.3) 153 (12.5) 1,228

Sources: Tong 2001, 2002. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Mekong Valley: Cambodia, Laos, Thailand, and Vietnam The Mekong River system is another large delta with potential for development of groundwater arsenic problems. So far few investigations have been carried out in the valley as a whole. Most investigation to date appears to have been carried out in Cambodia. The Mekong has a substantial proportion of its length within Cambodia and tubewells provide a significant source of potable supply in the country. Water testing for arsenic is ongoing and little information has so far been properly documented. A reconnaissance screening of around 100 tubewells from 13 provinces carried out by Partners for Development in 1999 included analysis of arsenic, fluoride, some trace metals, and some pesticides. Approximately 9% of the samples analyzed had arsenic concentrations >10 µg L-1, with observed concentrations in the range 10-500 µg L-1. Exceedances above 10 µg L-1 were found in 5 out of the 13 provinces investigated. The highest concentrations observed were from Kandal Province, close to Phnom Penh. Several districts in this province have a high percentage of wells with water containing arsenic in excess of the WHO guideline value (Feldman and Rosenboom 2000). Since this initial screening, field testing using portable kits has identified groundwater sources with concentrations above 10 µg L-1 in two additional provinces. High iron and manganese concentrations and anaerobic conditions are common features of the groundwaters throughout the lowland areas of Cambodia.

More recently, UNICEF has been carrying out groundwater arsenic screening in the Mekong aquifers. A map of perceived "arsenic risk" in groundwater has been produced based on geology (figure 9). Areas of greatest perceived risk are those with Holocene sediments forming the main aquifer. Groundwater arsenic data produced by UNICEF and JICA for the region so far (June 2003) are summarized in table 8 (see page 52). Around 19% of samples from the Holocene aquifer were found to contain arsenic at concentrations >50 µg L-1. UNICEF and other

Figure 9. Geological Map of Cambodia Showing Distribution of Potentially High-Arsenic Aquifers

Note: Areas of perceived “increased risk” are those with aquifers of Holocene age; areas of perceived “low risk” are Pleistocene aquifers; areas of “very low risk” are crystalline basement rocks. Geological units are provisional and accuracy of national boundaries is not guaranteed. Sources: UNICEF, Cambodia; D. Fredericks, pers. comm. 2003.

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Table 8. Summary Arsenic Data for Groundwater from Tubewells in the Mekong Valley of Cambodia

Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Holocene aquifer 301 (50) 185 (31) 113 (19) 599 Pleistocene aquifer 1,184 (95) 59 (5) 3 (0.2) 1,246 Crystalline rocks 708 (96) 24 (3) 2 (0.3) 734

Sources: Data from UNICEF and JICA; D. Fredericks, pers. comm., 2003.

organizations continue to support and carry out field testing using portable kits with supplementary laboratory analysis in Cambodia. A plan to blanket-test wells in 1,500 villages that abstract groundwater from Holocene sediments is currently being drawn up for the southern part of the country.

One noteworthy feature of the Cambodian Mekong results is that some of the highest arsenic concentrations have been found in urban areas, around Phnom Penh. Whether this reflects an impact of urbanization (increased groundwater pumping or increased inputs of pollutants such as organic carbon to the aquifers) is not known and is in need of further investigation.

As the Mekong valley also covers parts of Laos, Thailand, and Vietnam, arsenic problems are also possible in the alluvial and deltaic parts of these countries. However, few data are so far available from these regions to assess the scale of the problem there. Doan (n.d.) provided some arsenic data measured by spectrometry for groundwater samples from the Holocene, Pleistocene, and Pliocene aquifers of the Mekong delta area of Vietnam. Concentrations were found to be mostly low, with only one sample exceeding 50 µg L-1. Concentrations were in the range <1–5 µg L-1 for groundwaters from Holocene deposits (9 samples, depth range 4–19 m), <1–32 µg L-1 for those from Middle and Upper Pleistocene deposits (39 samples, depth range 5–120 m), <1–7 µg L-1 for groundwater from Lower Pleistocene deposits (12 samples, 52 53 depth range 113–191 m), and <1–57 µg L-1 for groundwater from Pliocene deposits (39 samples, depth range 85–330 m). Highest concentrations in this Pliocene aquifer were in the Ben Tre area of the central Mekong delta. The Pleistocene and Pliocene sediments are the most exploited aquifers in the region. The Holocene sediments appear to be largely low-yielding aquitards and are not heavily used. Doan (n.d.) reported that UNICEF carried out some qualitative arsenic testing of Mekong groundwaters in Vietnam but did not detect arsenic.

UNICEF have also carried out some preliminary testing of groundwater from wells in the Attapeu, Savannakhet, Champassak, Saravan, Sekong, Khammuane, and Bolikamxay areas of Lao PDR. Results from 200 samples reported by Fengthong, Dethoudom, and Keosavanh (2002) suggested that some samples had arsenic concentrations greater than 10 µg L-1 but only one exceeded 50 µg L-1. The highest concentration observed in the region was 112 µg L-1 (Attapeu Province). To date, UNICEF, in collaboration with the government and the Adventist Development and Relief Agency, have tested some 680 samples from drinking water sources and found 1% of sources having arsenic concentrations >50 µg L-1 (table 9, unpublished data). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 9. Summary Arsenic Data for Groundwater from Tubewells in the Mekong Valley of Lao PDR

Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Holocene aquifer 531 (78) 143 (21) 6 (1) 680

Source: Data from UNICEF, 2004.

Indus Plain, Pakistan Quaternary sediments, mainly of alluvial and deltaic origin, occur over large parts of the Indus plain of Pakistan (predominantly in Punjab and Sindh Provinces) and reach several hundred meters thickness in some parts (WAPDA-EUAD 1989). Aquifers in these sediments are potentially susceptible to high groundwater arsenic concentrations. The Indus sediments have some similarities with the arsenic-affected aquifers of Bangladesh and West Bengal, being Quaternary alluvial-deltaic sediments derived from Himalayan source rocks. However, the region differs in having a more arid climate, greater prevalence of older Quaternary (Pleistocene) deposits, and dominance of unconfined and aerobic aquifer conditions, with greater apparent connectivity between the river systems and the aquifers. Aerobic conditions are demonstrated by the presence of nitrate (Mahmood and others 1998; Tasneem 1999) and dissolved oxygen (Cook 1987) in many Indus groundwaters. Hence, the aquifers appear to have different redox characteristics from those of the lower parts of the Bengal basin. Under the more aerobic conditions (and near-neutral pH), arsenic mobilization in groundwater should be less favorable.

To date, only a limited amount of groundwater testing for arsenic has been carried out in Pakistan. However, the Provincial Government of Punjab together with UNICEF began a testing program in northern Punjab in 2000. Districts to be tested were selected on the basis of geology and available water quality information. These included areas affected by coal mining and geothermal springs (Jhelum and Chakwal Districts), areas draining crystalline rock (Attock and Rawalpindi), areas with high-iron groundwaters (Sargodha), and one district from the main Indus alluvial aquifer (Gujarat). A total of 364 samples were analyzed. The majority (90%) of samples had arsenic concentrations less than 10 µg L-1, although 6 samples (2%) had concentrations above 50 µg L-1 (table 10 see page 54) (Iqbal 2001). Further well testing for arsenic is ongoing. No confirmed cases of arsenic-related disease have been found in Pakistan, although epidemiological investigations are also being undertaken in some areas. From the available data, the scale of arsenic contamination of Indus groundwaters appears to be relatively small, although further results are needed to verify the region affected. Quaternary aeolian sand deposits occur to the east of the Indus plain (Thar and Cholistan desert areas) as well as over large parts of the Baluchistan basin of western Pakistan. Testing of abstraction tubewells in these areas is also required. Under the arid conditions in Pakistan, high fluoride concentrations and high salinity appear to be more widespread water-related problems than arsenic.

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Table 10. Frequency Distribution of Arsenic Concentrations in Groundwater Samples from Northern Punjab

District Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Gujarat 33 (87) 3 (8) 2 (5) 38 Jhelum 32 (86) 4 (11) 1 (3) 37 Chakwal 63 (88) 9 (12) 0 (0) 72 Sargodha 49 (83) 7 (12) 3 (5) 59 Attock 68 (92) 6 (8) 0 (0) 74 Rawalpindi 81 (96) 3 (4) 0 (0) 84 Total 326 (90) 30 (8) 6 (2) 364

Source: Iqbal 2001.

Mining and Mineralized Areas

Ron Phibun, Thailand Health problems related to arsenic have been well documented in Thailand, in this case related to mineralization and mining activity rather than alluvial and deltaic aquifers. In terms of documented health problems from drinking water, Ron Phibun District in Nakhon Si Thammarat Province in peninsular Thailand represents the worst-known case of arsenic poisoning related to mining activity (figure 1). Health problems were first recognized in the area in 1987 and over 1,000 people have been diagnosed with arsenic-related skin disorders, particularly in and close to Ron Phibun town (Williams 1997). At the time of first recognition of the problems, some 15,000 people are thought to have been drinking water with >50 µg L-1 arsenic (Fordyce and others 1995). The affected area lies within the Southeast Asian tin belt. Primary tin-tungsten- 54 55 arsenic mineralization and alluvial placer tin deposits have been mined in the district for over 100 years, although mining activities have now ceased. Legacies of the mine operations include arsenopyrite-rich waste piles, waste from ore-dressing plants and disseminated waste from small-scale panning by villagers. Remediation measures include transportation of waste to local landfill. Waste piles from former bedrock mining are found to contain up to 30% arsenic (Williams and others 1996). Alluvial soils also contain high concentrations of arsenic, up to 0.5% (Fordyce and others 1995).

High arsenic concentrations found in both surface and shallow groundwaters from the area around the mining activity are thought to be caused by oxidation of arsenopyrite, made worse by the former mining activities and subsequent mobilization during the postmining rise in groundwater levels (Williams 1997).

Surface waters draining the bedrock and alluvial mining areas are commonly acidic (pH <6) with -1 SO4 as the dominant anion (up to 142 mg L ) and with high concentrations of some trace Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

metals, including aluminum (up to 10,500 µg L-1), cadmium (up to 250 µg L-1), and zinc (up to -1 4,200 µg L ) (Williams and others 1996). Strong positive correlations are observed between SO4 and cadmium, aluminium, beryllium, zinc, and copper. Also, SO4 correlates negatively with pH (Fordyce and others 1995). These associations suggest strongly that arsenic and the associated trace metals are derived by oxidation of sulfide minerals. Concentrations of the trace metals diminish downstream of the mining area. Highest arsenic concentrations (up to 580 µg L-1) were found some 2–7 km downstream of the bedrock mining area (Williams and others 1996).

Shallow groundwaters (<15 m) are from alluvial and colluvial deposits and deeper groundwaters (>15 m) are from an older carbonate aquifer. The shallow aquifer shows the greatest contamination with arsenic, with concentrations up to 5,100 µg L-1 (figure 10). In the shallow aquifer, 39% of samples collected randomly had arsenic concentrations >50 µg L-1, while in the deeper aquifer, 15% exceeded 50 µg L-1 (table 11 see page 56) (Williams and others 1996).

The high-arsenic groundwaters of the Ron Phibun area clearly differ from many other high- arsenic groundwater provinces in Asia. In the shallow aquifer, conditions are more oxidizing than those prevalent in, for instance, the worst-affected areas of Bangladesh and West Bengal. The differences reflect the distinct geochemical reactions that are controlling the groundwater arsenic concentrations (section 3.3). In the groundwaters from the deeper aquifer of Ron Phibun conditions appear more similar to those from other high-arsenic aquifers in Asia and the

Figure 10. Simplified Geology of the Ron Phibun Area, Thailand, Showing the Distribution of Arsenic in Analyzed Groundwaters

Note: The distributions are (a) arsenic in groundwater from shallow tubewells (<15 m depth); (b) arsenic in groundwater from deeper tubewells (>15 m). Numbers refer to samples given in Williams and others 1996. Source: Williams and others 1996.

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Table 11. Frequency Distribution of Arsenic Concentrations in Water from Phibun Area

Aquifer Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Surface water 1 (4) 2 (8) 20 (83) 24 Groundwater from 7 (30) 7 (30) 9 (39) 23 shallow aquifer (<15 m) Groundwater from 9 (69) 2 (15) 2 (15) 13 deeper aquifer (>15 m)

Source: Williams and others 1996.

maintenance of arsenic in solution appears to be more of a function of the presence of reducing conditions, although leakage of high-arsenic water from the overlying shallow aquifer is also a possibility.

Rajnandgaon District, Madhya Pradesh, India Water-related arsenic problems first became recognized in Rajnandgaon District, Madhya Pradesh, in 1999. Concentrations in groundwater samples from the worst-affected village, Kondikasa, in Chowki block, have been found to range between <10 µg L-1 and 880 µg L-1 (Chakraborti and others 1999). Out of 146 samples analyzed, 8% were found to contain more than 50 µg L-1 arsenic (table 12). Three of these exceeding samples were from dug wells, one containing a concentration of 520 µg L-1. Most were from tubewells, which were usually less than 50 m deep (range 10–75 m). Arsenic-related skin disorders have been recognized in a number of the villagers. Gold-mining activity has taken place in the local area, though the extent of mining and of mineralization is not documented. To date, no maps have been produced of 56 57 Chowki block to indicate the distribution and scale of the problem.

Table 12. Frequency Distribution of Arsenic Concentrations in Groundwater from Chowki Block, Madhya Pradesh, India

Blocks Number of samples (%) Total samples <10 µg L-1 10–50 µg L-1 >50 µg L-1

Chowki 109 (75) 25 (17) 12 (8) 146

Source: Chakraborti and others 1999. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Other Areas Although many areas of mining and mineralization exist in South and East Asia, few have been documented and the distribution of groundwater arsenic concentrations related to them is unknown. High concentrations were noted in some surface waters and groundwaters close to the Bau mining area of Sarawak, Malaysia (Breward and Williams 1994), although there is no evidence that affected waters are used for drinking water. Arsenic is a well-known risk in sulfide mineralized areas and hence the locations of such problems can be reasonably well predicted. Despite many mining-related problems, modern mining practices are designed to minimize environmental impacts. Environmental protection measures include criteria for siting and management of waste piles, control of effluents, and treatment of acid mine drainage.

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3. Hydrogeochemistry of Arsenic

Overview here has been a considerable increase in the amount of research carried out on arsenic in Tgroundwater and the environment over the last few years and understanding of the processes involved has improved as a result of studies carried out in Asia and elsewhere. However, many aspects of the mechanisms of release are still poorly understood. Our ability to predict the variations with time is limited, yet temporal variations in arsenic concentration are a central issue to mitigation. Below are outlined what we know of the principal causes of arsenic mobilization in water and the environment and the information that is available concerning spatial and temporal variability in the arsenic-affected aquifers of Asia.

The highest concentrations of arsenic tend to occur in sulfide minerals and metal oxides, especially iron oxides. It therefore follows that where these occur in abundance, arsenic problems can result if the release from the minerals is favored. Under most circumstances, the mobilization of arsenic in surface waters and groundwaters is low because of retention in these mineral sinks. However, the toxicity of arsenic is such that it only takes a very small proportion of the solid-phase arsenic to be released to produce a groundwater arsenic problem. There are a number of drivers that can result in the release of arsenic from minerals and the build-up of detrimental concentrations in water. These are outlined in broad terms below.

Arsenic Sources Arsenic occurs naturally in all minerals and rocks, although its distribution within them varies widely. Arsenic occurs as a major constituent in more than 200 minerals, including elemental arsenic, arsenides, sulfides, oxides, arsenates, and arsenites. Most are ore minerals or their alteration products. However, these minerals are relatively rare in the natural environment. The greatest concentrations of them occur in mineral veins. The most abundant arsenic ore mineral is arsenopyrite (FeAsS). This is often present in ore deposits, but is much less abundant than arsenian pyrite (Fe(S,As) ), which is probably the most important source of arsenic in ore zones. 58 59 2 Other arsenic sulfides found in mineralized areas are realgar (AsS) and orpiment (As2S3).

Though not a major component, arsenic is also present in varying concentrations in common rock-forming minerals. As the chemistry of arsenic follows closely that of sulfur, the other, more abundant, sulfide minerals also tend to have high concentrations of arsenic. The most abundant

of these is pyrite (FeS2). Concentrations of arsenic in pyrite, chalcopyrite, galena, and marcasite can be very variable but in some cases can exceed 10 weight percentage (table 13). Besides being an important component of ore bodies, pyrite is also formed in low-temperature sedimentary environments under reducing conditions. It is present in the sediments of many rivers, lakes, and oceans, as well as in a number of aquifers. Pyrite is not stable in aerobic systems and oxidizes to iron oxides with the release of sulfate, acidity, arsenic, and other trace elements. The presence of pyrite as a minor constituent in sulfide-rich coals is ultimately responsible for the production of acid rain and acid mine drainage, and for the presence of arsenic problems around coal mines and areas of intensive coal burning. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 13. Typical Arsenic Concentrations in Rock-Forming Minerals

Mineral Arsenic concentration range (mg kg-1)

Sulfide minerals Pyrite 100–77,000 Pyrrhotite 5–100 Marcasite 20–126,000 Galena 5–10,000 Sphalerite 5–17,000 Chalcopyrite 10–5,000 Oxide minerals Hematite up to 160 Fe oxide (undifferentiated) up to 2,000 Fe(III) oxyhydroxide up to 76,000 Magnetite 2.7–41 Ilmenite <1 Silicate minerals Quartz 0.4–1.3 Feldspar <0.1–2.1 Biotite 1.4 Amphibole 1.1–2.3 Olivine 0.08–0.17 Pyroxene 0.05–0.8 Carbonate minerals Calcite 1–8

Dolomite <3

Siderite <3

Sulfate minerals Gypsum/anhydrite <1–6 Barite <1–12 Jarosite 34–1,000 Other minerals Apatite <1–1,000 Halite <3–30 Fluorite <2

Source: Smedley and Kinniburgh 2002 and references therein.

Paper 1 Arsenic Occurence in Groundwater in South and East Asia – Scale, Causes, and Mitigation Volume II Technical Report Towards a More Effective Operational Response

High concentrations of arsenic are also found in many oxide minerals and hydrous metal oxides, either as part of the mineral structure or adsorbed to surfaces. Concentrations in iron oxides can also reach weight percentage values (table 13), particularly where they form as the oxidation products of primary iron sulfides. Adsorption of arsenate to hydrous iron oxides is known to be particularly strong. Adsorption to hydrous aluminum and manganese oxides may also be important if these oxides are present in quantity (for example Peterson and Carpenter 1983; Brannon and Patrick 1987). Arsenic may also be adsorbed to the edges of clays and on the surface of calcite. However, the loadings involved are much smaller on a weight basis than for the iron oxides. Adsorption reactions are responsible for the low concentrations of arsenic found in most natural waters.

Arsenic is also present in many other rock-forming minerals, albeit at comparatively low concentrations. Most common silicate minerals contain around 1 mg kg-1 or less. Carbonate minerals usually contain less than 10 mg kg-1 arsenic (table 13).

Rocks, sediments, and soils contain variable concentrations of arsenic but, not surprisingly, the highest concentrations tend to be found in materials with abundant sulfide and oxide minerals. Fine-grained sediments such as shales, mudstones, and their unconsolidated equivalents tend to contain the highest concentrations of arsenic. A summary of typical concentration ranges in common rocks, sediments, and soils is given in table 14.

Arsenic is also introduced to the environment through a number of human activities. Apart from mining activity and the combustion of fossil fuels, which involve redistribution of naturally occurring arsenic, concentrations in the environment can increase through the manufacture and use of arsenical compounds such as pesticides, herbicides, crop desiccants, and additives in livestock feed, particularly for poultry. The use of arsenical pesticides and herbicides has decreased significantly in the last few decades, but their use for wood preservation and feed additives is still common. The use of chromated copper arsonate (CCA) as a wood preservative 60 61 may be banned in Europe in the coming years. The environmental impact of using arsenical compounds can be major and long lasting, although the effects of most are relatively localized. Most environmental arsenic problems recognized today are the result of mobilization under natural conditions.

Processes Involved in Mobilization

Oxidation of Sulfide Minerals Many mining areas with an abundance of sulfide minerals demonstrate the environmental effects of sulfide mineral oxidation. Acid mine drainage is one notable consequence. Oxidation of pyrite by atmospheric oxygen can be described by the reaction:

-2 + FeS2 + 15/4O2 + 7/2H2O ® Fe(OH)3 + 2SO4 + 4H Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 14. Typical Arsenic Concentration Ranges in Rocks, Sediments, and Soils

Classification Rock/sediment type Arsenic range (mg kg-1)

Igneous rocks Ultrabasic rocks 0.03–16 Basic rocks 1.5–110 Intermediate 0.09–13 Acidic rocks 0.2–15 Metamorphic rocks Quartzite 2.2–7.6 Hornfels 0.7–11 Phyllite/slate 0.5–140 Schist/gneiss <0.1–19 Amphibolite/greenstone 0.4–45 Sedimentary rocks Shale/mudstone 3–490 Sandstone 0.6–120 Limestone 0.1–20 Phosphorite 0.4–190 Iron formations and iron-rich sediment 1–2,900 Evaporite deposits 0.1–10 Coal 0.3–35,000 Bituminous shale 100–900 Unconsolidated Sediments 0.5–50 sediments and soils Soils 0.1–55 Soils near sulfide deposits 2–8,000

Source: Smedley and Kinniburgh 2002 and references therein.

The overall oxidation reaction leads to the generation of iron oxide (Fe(OH)3) and dissolved + sulfate (SO4) as well as the production of acid (H ). The oxidation can also lead to the release of trace metals and arsenic into solution. Even larger quantities of arsenic can be released from arsenic sulfide minerals such as arsenopyrite (FeAsS). However, the strong adsorption capacity of iron oxides (especially the freshly formed, poorly crystalline oxides), together with the tendency for acidic conditions, normally mean that dissolved arsenic concentrations diminish at some distance downstream. Although a significant source of arsenic exists locally to produce an aqueous arsenic problem in such areas, the local geochemical conditions are usually unsuitable to maintain it.

The effects of sulfide mineral oxidation have also been seen in mineralized aquifers as a result of lowering the water table and introducing atmospheric oxygen to the aquifer. Probably the best example to demonstrate this is the mineralized sedimentary aquifers of Wisconsin, United States. Here, historical abstraction of groundwater has led to aquifer dewatering and the accumulation of concentrations of arsenic up to 12,000 µg L-1 in the groundwater at the levels of

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the mineralized veins (Schreiber, Simo, and Freiberg 2000). Oxidation of sulfide minerals has been advocated strongly by many workers in West Bengal (for example Das and others 1994) as the cause of groundwater arsenic problems in the Bengal basin. It is well known that authigenic sulfide minerals can form under strongly reducing conditions in sediments in aquifers, lakes, and marine settings. Generation of groundwater arsenic problems if these are allowed to oxidize is a reasonable hypothesis. However, the evidence for this mode of occurrence in the aquifers of the Bengal basin is lacking. It is possible that such oxidation processes could be involved in some parts of the aquifers, particularly at the shallowest levels, for instance the depths penetrated by dug wells. However, it is not considered to be the main cause of the groundwater arsenic problems in the Bengal basin or other sedimentary aquifers in Asia where the major arsenic problems exist. Indeed, groundwater in most dug wells from the Bengal basin has low arsenic concentrations.

Release from Iron Oxides

Release under Reducing Conditions One of the main conclusions from recent research studies has been that desorption or dissolution of arsenic from iron oxides is an important or even dominant control on the regional distributions of arsenic in water. The onset of reducing conditions in aquifers can lead to a series of changes in the water and sediment chemistry as well as in the structure of the iron oxides. Many of these changes are poorly understood on a molecular scale. Some critical reactions in the change to reducing conditions and to subsequent arsenic release are likely to be the reduction of arsenic from its oxidized (As(V)) form to its reduced (As(III)) form. Under many conditions, As(III) is less strongly adsorbed to iron oxides than As(V) and reduction should therefore involve a net release from adsorption sites. Dissolution of the iron oxides themselves under reducing conditions is another potentially important process. Additional influences such as competition from other anionic solutes (for example phosphate) for adsorption sites may also be important. It is notable, for example, that reducing aquifers such as those of Bangladesh, 62 63 West Bengal, and China have relatively high concentrations of dissolved phosphate. These are sometimes in excess of 1 mg L-1 and almost always in excess of the concentrations of dissolved arsenic.

The onset of reducing conditions in aquifers may result from rapid burial, particularly evident in areas of rapidly accumulating sediment (for example deltas). Burial of organic matter along with the sediments facilitates microbial activity, which plays an important role in the generation of the reducing conditions (BGS and DPHE 2001; McArthur and others 2001). The role of microbes in the reduction and mobilization process has been increasingly recognised in recent years (Oremland and others 2002; Islam and others 2004). The rates of the arsenic release reactions under such conditions are likely to be dependent on a number of factors, including rates of sedimentation, diffusion of gases, and microbial reactions, but they are likely to be relatively rapid on a geological timescale. The onset of reducing conditions and release from iron oxides is believed to be the main process controlling the high arsenic concentrations in the sedimentary aquifers of Asia. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The nature of the organic matter involved in the generation of reducing conditions in arsenic- affected aquifers has been disputed in recent years. Some have cited disseminated fine-grained solid and dissolved organic matter as the key redox driver (for example BGS and DPHE 2001), others cite occurrences of peat (McArthur and others 2001), while some have suggested that recent anthropogenic organic carbon is responsible (Harvey and others 2002). Whatever the origin, the importance of organic matter in controlling the redox conditions in reducing aquifers such as those of the Bengal basin is widely acknowledged.

In the groundwaters from the shallow aquifer of Bangladesh, the highest and most variable concentrations of arsenic occur in strongly reducing groundwaters below the redox boundary (zone over which the groundwater changes from oxidizing to reducing conditions, usually just a few meters below the piezometric surface) (figure 11). Dug wells typically penetrate the shallowest levels of aquifers where conditions are relatively oxidized. Tubewells usually

Figure 11. Schematic Diagram of the Aquifers in Southern Bangladesh Showing the Distribution of Arsenic and the Configuration of Wells

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penetrate to deeper levels than dug wells in order to obtain better groundwater yields (although depths are usually the minimum required to achieve this). Entry of air to the open large-diameter wells also helps to maintain their relatively oxidized status in most circumstances (except in stagnant groundwater conditions with excess organic matter). Under most conditions, therefore, groundwater in dug wells is likely to have relatively low arsenic concentrations as a combined function of shallow depth and the nature of the well construction.

Release at High pH Under aerobic and acidic to neutral conditions characteristic of many natural environments, adsorption of arsenic (as As(V)) to iron oxides is normally strong and aqueous concentrations are therefore usually low. However, the sorption is less strong at high pH. Increases in pH (especially above pH 8.5 or so) will therefore result in desorption of arsenic from oxide surfaces and a resultant increase in dissolved concentrations. Such processes are considered to have been responsible for the release of arsenic in oxidizing Quaternary sedimentary aquifers in, for example, the arid inland basins of Argentina (Smedley and others 2002) and southwest United States (Robertson 1989). Similar conditions have not been found to date in Asian sedimentary aquifers but the process may take place in some areas (for example arid regions of China or Pakistan).

Release from Other Metal Oxides Although more research has been done on arsenic and its association with iron oxides, aluminum and manganese oxides can also adsorb arsenic and may be additional sources or sinks for arsenic if present in quantity in any given aquifer. They are likely to be less significant than iron oxides in controlling arsenic concentrations in groundwater, but cannot be ignored, and have been cited as potential sources of arsenic in some aquifers, including those in Bangladesh and Argentina.

Groundwater Flow and Transport 64 65 Geochemical conditions suitable for arsenic release are important in generating groundwater arsenic problems but the problems will only remain if the arsenic is not flushed away by moving groundwater over time. Another feature of many of the high-arsenic groundwater provinces of Asia is slow groundwater movement. A combination of young sediments (often <10,000 years old) and slow rates of aquifer flushing (for example low rates of recharge, poor sediment permeability, low hydraulic gradients) mean that arsenic accumulated through geochemical processes has not been flushed from the aquifer during its evolutionary history. This argument has been used in part to explain why the deep (Pleistocene) aquifers of Bangladesh and other near-coastal aquifers have low arsenic concentrations. During pre-Holocene times, it is known that glacial conditions were associated with long-term low relative sea level (up to 120 m below those of the present day; figure 12). This would have resulted in greater head gradients in the past and more active groundwater movement (box 4 see page 66). It has been suggested that the deep aquifer had a longer history of flushing during the pre-Holocene past and that solute arsenic accumulated in the past has been flushed from the aquifer over time (BGS and DPHE Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Figure 12. Sea Level Changes during the Last 140,000 Years

Source: After Pirazzoli 1996.

2001). Interestingly, such steep head gradients would not have affected inland basins such as those of northern China and so deep aquifers in such areas would not have been subject to such active groundwater flow during past ice ages.

It is also likely that sediments of the older deeper aquifers are mineralogically and texturally distinct from the younger Holocene deposits, a factor that may have a bearing on the groundwater arsenic concentrations. Certainly in Bangladesh, evidence suggests that the deeper Pleistocene sediments are dominantly more brown in color than the Holocene deposits and therefore appear to be more oxidized. More work on the sediment chemistry of the deep aquifers of the Bengal basin is required to investigate this further.

Impact of Human Activities A relevant question that has not been fully answered by the various studies of arsenic occurrence in South and East Asia is the extent to which human activities have contributed to the arsenic problems in different situations. It is clear that in sulfide mining areas such activities as excavating ore minerals, redistributing waste piles, and pumping mine effluent have exacerbated the problem. However, in sedimentary aquifers, the relationships are much less clear cut. Scientists working in West Bengal in the 1990s were of the opinion that the arsenic problem was of recent origin and related to the dewatering and oxidation of sedimentary aquifers containing pyrite (or arsenopyrite) through overabstraction of groundwater for irrigation of rice crops. Convincing evidence for this has never been produced, and subsequent studies in the Bengal basin have related the occurrence of arsenic to the presence of natural strongly reducing conditions coupled with slow groundwater movement. From this conclusion, it follows that the arsenic phenomenon is not recent but originated from the time of sediment burial and

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Box 4. Frequently Asked Questions

Why are arsenic concentrations often high in the shallow aquifers of Bangladesh but usually low in the deep aquifer?

This question is difficult to answer for certain because little information currently exists on the geology and hydrogeology of the deep aquifer. Limited data available so far suggest that the older (deeper) sediments are lithologically different. They are often brown in contrast to the overlying sediments, which are variable but commonly grey. The color changes suggest changes in redox conditions, the deeper sediments being relatively oxic. Differences in hydrogeological history are also likely to be significant. Older sediments at depth have undergone longer periods of groundwater flushing. During the last glacial maximum around 12,000 years ago relative sea level would have been much lower than its present level, resulting in steeper groundwater gradients and more active groundwater flow. Young (Holocene) sediments overlying these deposits have been deposited in postglacial times, have not had such a long history of flushing, and have not been subject to such large relative sea level fluctuations. They also contain freshly formed minerals which may be highly prone to reaction under reducing aquifer conditions.

Why are concentrations in groundwater from deep aquifers in other areas not always low?

In contrast to Bangladesh, deep aquifer sediments of unknown but probable Pleistocene age in Inner Mongolia (China) contain groundwater with sometimes high arsenic concentrations. In these, the sediment lithology is poorly defined as few geological studies have been carried out. It is likely that these have not been well flushed since deposition as the area is an internal drainage basin that would not have been so greatly influenced by past sea level fluctuations. The deep aquifers of Inner Mongolia are thought to be occupied by very slow-moving groundwater.

Are the arsenic concentrations in wells going to improve or deteriorate with time?

At present, there are insufficient data to define the nature of variability in individual wells over periods of days to weeks to years and more monitoring data are needed to define the temporal trends. Mixing of waters with different compositions will necessarily involve changes in arsenic concentration but on 66 67 what scale and over what period are uncertain. Such changes will involve decreases as well as increases. Variations are likely to be greater at shallow depths than at deeper levels because groundwater flow is more active near the water table and inputs greater. In the first instance, it is reasonable to assume that an initial arsenic concentration (provided it is analytically reliable) will be representative for a given well and that it will not change significantly in the short term.

the onset of reduction. The arsenic in Bangladesh groundwaters may therefore have been present for hundreds to thousands of years (BGS and DPHE 2001).

That is not to say that no impact can be expected from human activities. The impacts of pumping on groundwater flow mean that some changes to the aquifer systems are likely in the medium to long term. Quantifying those impacts is difficult. There are various dimensions to the potential human influences, including the impacts of pumping-induced flow on transport of Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

arsenic both within and between aquifers, impact of pollutants such as organic carbon and phosphate on aquifer redox and sorption/desorption reactions, and impact of seasonal waterlogging of soils for rice production on subsurface redox conditions.

It is interesting that arsenic problems in the Red River delta of Vietnam are close to southern Hanoi and those of Cambodia close to Phnomh Penh. Whether this reflects a bias in regional testing or real highs in urban areas compared to rural areas is still open to question. Disposal of urban wastewater including sewage along open drains has been documented for Hanoi for example (Trafford and others 1996). Harvey and others (2002) concluded that groundwater arsenic problems in part of Bangladesh were related to the introduction of organic carbon to the aquifer from surface pollutants. However, the evidence presented for this was unconvincing and the conclusion has sparked much subsequent debate. The impacts on groundwater quality of the human influences described above have received insufficient attention in past studies and require further investigation in order to ensure that groundwater resources will be sustainable and protected.

At-Risk Aquifers

The previous sections indicate that many uncertainties exist over the spatial distribution of arsenic problems in groundwaters of Asia and elsewhere. However, sufficient information is available on the recognized high-arsenic groundwater provinces to allow them to be broadly categorized in terms of geology, hydrogeology, and the processes likely to be controlling arsenic mobilization. A number of risk factors for the development of high-arsenic groundwaters were identified and summarized by Smedley and Kinniburgh (2002). These are highlighted in figure 13. While no single factor is likely to be sufficient to identify likely at-risk aquifers, combinations of factors can be of value in pinpointing areas deserving increased priority for groundwater chemical analysis.

In arsenic-affected aquifers of Asia, some notable parallels in geology and hydrogeology are identifiable. Apart from areas related to bedrock mineralization and mining activity (Ron Phibun, Thailand; Madhya Pradesh, India), and localized areas of geothermal activity, the documented cases included in chapter 2 are from young (Quaternary) sedimentary aquifers of alluvial, deltaic, or lacustrine origin. Sediments rich in iron oxides may be particularly susceptible. In such aquifers, the presence of reducing conditions appears to be a key factor in determining on a regional scale where high groundwater arsenic concentrations will occur. Groundwaters with, for example, high concentrations of iron, manganese, and ammonium will therefore be more likely to have high concentrations of arsenic than those with low concentrations. Where data for these are available they can act as warning signs of potential arsenic problems, although, as noted above, they cannot be taken as direct indicators of arsenic concentrations. Ancillary information such as low or no dissolved oxygen, low concentrations of sulfate, and high concentrations of dissolved organic carbon can also be of use in defining reducing aquifers (figure 13).

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Figure 13. Classification of Groundwater Environments Susceptible to Arsenic Problems from Natural Sources

High-arsenic groundwater province

Geothermally influenced groundwater Low-temperature groundwater

Nonmining areas Sulfide mining and mineralized areas

Low rate of flushing:a Young aquifer (Quaternary) Low hydraulic gradient (deltas, closed basin) Slow groundwater flow Poor drainage Arid/semiarid environment Old groundwaters High chemical spatial variability Large volume of young sediments: Large deltas and inland basin

Reducing: Environment Process Indicators Process Environment Oxidizing: Mineral dissolution Mixing/ Reductive desorption and dilution Desorption (Fe oxides) e.g. pyrite oxidation dissolution Evaporation Oxidizing or mildly reducing (Fe oxides) Confined aquifers

Low Eh (<50 mV) High Fe, SO Increased temperature No dissolved oxygen High pH (>8) 4 Increased salinity (Na, Cl) High alkalinity (>500 mg L-1) Possibly low pH High Fe, Mn, NH4 -1 Possibly high F, U, B, Se, Mo Presence of other trace High B, Li, F, Si02 Low SO (<5 mg L ) 4 metals (Cu, Ni, Pb, Zn, High pH >7 High alkalinity (>500 mg L-1) Increased salinity Al, Co, Cd) Possibly high DOC (>10 mg L-1) High Eh, DOC

E.g. Bangladesh; China (Inner Mongolia); Taiwan; West Bengal in India; Nepal E.g. Pakistan Possibly: Cambodia; some parts of northern Possibly: Some parts of northern China China; Lao PDR; Vietnam

68 69 Note: Not all indicators of low flushing rates necessarily apply to all environments. Source: Smedley and Kinniburgh 2002.

Slow groundwater movement is also a common feature of the identified high-arsenic groundwater provinces of Asia and elsewhere. Aquifers with limited recharge or low hydraulic gradients are likely to have slow groundwater flow.

Aquifer size and sedimentation rate may also be relevant criteria in determining groundwater quality. The Bengal basin is one of the largest and most rapidly accreting sediment basins in the world and the rapid burial of organic matter along with sediments (restriction of air access) may accelerate the onset of reducing conditions.

Arsenic problems have also been found in oxidizing conditions in some arid and semiarid inland (closed) basins. As noted above, these groundwaters are typically characterized by high pH (>8) Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

and are accompanied by high salinity. High concentrations of trace elements such as fluoride, molybdenum, and boron are also characteristic. While none of the oxidizing, high-pH groundwater provinces recognized so far is from Asia, this is not to say that such conditions will not occur. Major deposits of Quaternary sediments (including loess) cover large parts of northern China, for example. Quaternary aeolian deposits of Pakistan, including the Baluchistan basin, also contain high-pH groundwater. It is believed that the groundwaters in these areas have not been tested for arsenic.

One of the key findings of the last few years has been that the affected sedimentary aquifers of Asia (for example Bangladesh, China) do not have anomalously high concentrations of arsenic in the sediments. This is important because it implies that potentially any young sediments could develop groundwater arsenic problems, given a combination of geochemical conditions conducive to the release of arsenic (reducing conditions or oxidizing, high-pH conditions) and hydrogeological conditions that prevent it from being flushed from the aquifer. Other alluvial and deltaic plains, such as the lower reaches of the Yellow River plain and Yangtze River of China and the Chao Phraya River of Thailand, deserve further investigation.

Variability in Arsenic Concentrations

Spatial Variability A high degree of spatial variability in arsenic concentrations both areally and with depth has been noted in many of the recognized problem aquifers. Such variability is a natural consequence of sediment heterogeneity and poor mixing brought about by sluggish groundwater movement. Notable vertical variations in sediment texture, composition, and grain size have been observed from sediments in Bangladesh on a scale of centimeters. This can have large impacts on groundwater movement between layers, on water-rock interactions, and on local redox conditions. Small differences in depth of closely spaced wells can result in the tapping of different horizons (figure 11). Lack of homogenization of groundwaters and poor hydraulic connection between layers can maintain chemical differences on local scales. Besides, it should be borne in mind that in terms of thresholds of acceptability the difference between concentrations of 10 µg L-1 and 50 µg L-1 is critical, yet geochemically the differences are very small.

Many high-arsenic groundwaters appear to be associated with occurrence of finer-grained and iron oxide-rich deposits, such as accumulate preferentially in low-lying distal parts of deltas or in low-flow zones of river flood plains. The occurrence of local arsenic hotspots observed in, for instance, Bangladesh aquifers may be explained by the localized occurrence of fine-grained sediments in inside meanders and oxbow lakes. Together with locally slow groundwater movement in these areas, this may be responsible for the build-up (and lack of flushing) of arsenic.

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Temporal Variability

High-Arsenic Aquifers The timescales over which temporal variations in arsenic concentrations may exist range from hours (diurnal changes) through seasons to years or decades. The potential causes of such changes are also variable: changes in groundwater pumping rate over the course of a day; seasonal variations in recharge, irrigation abstraction, and head gradients; long-term changes in pumping regimes and climate. During the seasonal or annual cycle of a major abstraction source such as an irrigation well or municipal supply well, the chemical composition of abstracted groundwater may be affected by the variable contribution from different depths, which changes with time. Initial discharge tends to be dominated by flow from the shallowest horizons with deeper flow becoming more important with time as the cone of groundwater depression deepens. This influence is likely to be less important for small handpumped tubewells which individually involve much smaller abstractions. Changes in chemical compositions over longer timescales may result from long-term changes in groundwater level. To date, there has been very little investigation of the temporal variations in groundwater chemistry in high-arsenic aquifers from Asia and much more needs to be done to assess whether variations are significant in a practical sense.

In Bangladesh, BGS and DPHE (2001) did not find evidence of significant temporal variation during fortnightly monitoring of groundwater from specially drilled piezometers over the course of a year. An example of this monitoring is given for Faridpur in central Bangladesh in figure 14. Little variation was found either at shallow (tens of meters) or deep (150 m) levels. Continued monitoring of these piezometers after the completion of the BGS and DPHE project could have revealed useful information on the temporal variations over longer timescales, but unfortunately this was not carried out. As with the BGS and DPHE (2001) results, Tareq and others (2003) did not find significant seasonal variation in groundwater arsenic concentrations in 10 shallow tubewells from Bangladesh. Variations in arsenic concentration monitored premonsoon, syn-monsoon and postmonsoon were in the range 10-16% and largely within analytical error. 70 71 Few time series data are documented for the groundwaters of West Bengal and, as with Bangladesh, there remains uncertainty over whether significant temporal variations in arsenic concentration occur. They may occur in some places and not others. CGWB (1999) concluded from West Bengal groundwaters that groundwater arsenic concentrations vary seasonally, with minima during the postmonsoon period, considered to be due to dilution of groundwater by monsoon recharge. However, the conclusion is apparently based on small sample sets (4–6 samples at any given location) collected over a short time interval (less than one year). Chatterjee and others (1995) noted a variation of around 30% in time series data from monitoring of groundwaters over the period of a year in their study of parts of 24 Parganas North and South, but detected no significant seasonal changes in the variation.

Deep (Older) Aquifers It has often been said in relation to the deep aquifers of the Bengal basin that some wells that Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Figure 14. Monitoring Data for Groundwater from Selected Wells and Specially Drilled Piezometers in Faridpur Area, Central Bangladesh

Source: BGS and DPHE 2001.

were once arsenic free have become contaminated with time (for example Mandal and others 1996). However, documentation and data in support of this conclusion are difficult to find. Since the long-term trends in groundwater arsenic concentrations are a critical issue for the sustainability of the deep aquifers, the data that indicate such variations need to be documented properly and be open to peer review. If temporal trends are apparent in groundwater from deep aquifers, there are a number of reasons why this may be the case. These include inadequate sealing of tubewells, multiple screening of tubewells at different depths to improve yields, as well as natural hydraulic connectivity between aquifers (as stated above). They also may represent analytical problems. A statistical approach is needed in interpreting time series data.

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Dug Wells Few time series data exist for dug wells in arsenic-affected areas. Arsenic concentrations in dug wells may be susceptible to temporal change as the groundwaters abstracted from them are from the shallowest levels and therefore subject to the largest changes in recharge inputs, pollutant inputs, and redox conditions. They may also vary if particulate contents vary with time and water samples taken from them are not filtered. Despite these possibilities, groundwater in three dug wells from northwest Bangladesh monitored by BGS and DPHE (2001) over the course of a year showed little statistically significant variation. Concentrations were low and in the range 0.5–2 µg L-1, with only two individual measurements from the wells exceeding 10 µg L-1. More data are clearly needed to determine whether significant temporal changes occur in other areas, particularly where local groundwater arsenic concentrations are high. The relative contributions of particulate and dissolved fractions should also be investigated by measurement of other parameters (notably iron) as well as arsenic.

Arsenic in Surface Water Little information is available on the arsenic concentrations of surface waters in regions with high groundwater arsenic concentrations. Even less is available on temporal variations. The greater likelihood of high suspended loads in surface waters means that the concentrations are potentially more variable than in most groundwaters as the arsenic associated with particles can be significant. Concentrations in particles are likely to be in the range 5–10 mg kg-1, in line with the concentrations of average sediments, but may be higher in iron-rich particles. There is also potential that river waters will vary seasonally as a result of the variations in the proportion of baseflow compared to runoff. This has not been studied in detail. However, most of the evidence points to surface waters generally having low arsenic concentrations, even where groundwater arsenic concentrations are high.

72 73 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

4. Groundwater Management for Drinking Water and Irrigation

Overview he previous sections highlight the extreme variability in arsenic concentrations both within Tand between aquifers and have shown some of the issues associated with identifying safe sources of water and determining suitable alternatives. One of the key developments of the past few years has been the realization that the mode of occurrence of arsenic in water can vary substantially. The mechanisms of arsenic occurrence in water in mining and mineralized areas can be very different from those in young sedimentary aquifers and their distribution and scale can also differ considerably. Some of the options for water supply are detailed further in this section, along with the risks associated with them and potential strategies for dealing with those risks. The choice of water supply in any given area must depend on many technical and social factors that need to be assessed locally. The options, risks, and potential mitigation strategies are summarized in table 15, at the end of this chapter.

Mining and Mineralized Areas

In areas with rich deposits of sulfide minerals, both surface waters and groundwaters are potentially vulnerable to high arsenic concentrations. Other toxic trace elements may also be present in excessive concentrations (for example copper, lead, zinc, cobalt, cadmium, nickel). In these areas, surface waters, groundwaters, and soils are all potentially affected by high arsenic concentrations. However, the scale of contamination is likely to be localized, on the scale of a few kilometers around the site of mineralization. Mitigation of the problem therefore centers on identifying contaminated water sources and finding alternative supplies locally. Both identification of at-risk sources and mitigation should be less of a problem than in arsenic- affected sedimentary aquifers. Environmental problems are usually exacerbated by mining activity and are therefore largely predictable.

Sedimentary Aquifers

Shallow Groundwater

Shallow Tubewells Of the sedimentary aquifers in South and East Asia with recognized arsenic problems, the majority are composed of young sediments at shallow depths of less than 50-100 m or so. In Bangladesh the highest concentrations and largest range of concentrations are found in the shallow aquifers, which are dominantly of Holocene (<12,000 years) age. The extreme variability indicates that on a local scale, the scale relevant to mitigation, no reliable method can be used to predict their concentrations accurately and no substitute therefore exists for testing each well for arsenic if it is to be used for drinking water. This is not to say that on a regional scale some sort of prioritization would not be possible given some knowledge of the distribution of sediment textures, hydrogeology, and water chemistry. Bangladesh groundwaters tend to have

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highest arsenic concentrations in the low-lying parts of the delta. This is also evident in other aquifers of Asia (for example Huhhot basin, China) (Smedley and others 2003). However, our understanding of the distribution of arsenic in groundwater at present does not allow prediction of such trends with confidence, even on a regional scale, and hence major testing programs in such susceptible aquifers are needed regardless of local geological variations.

The distributions of arsenic in different districts of Bangladesh vary widely (BGS and PDHE 2001). The worst-affected districts identified from the BGS and DPHE (2001) study were (percentage of samples with arsenic concentrations greater than 50 µg L-1 in parentheses): Chandpur (90%), Munshiganj (83%), Gopalganj (79%), Madaripur (69%), Noakhali (69%), Satkira (67%), Comilla (65%), Faridpur (65%), Shariatpur (65%), Meherpur (60%), Bagerhat (60%), and Lakshmipur (56%). In the worst-affected areas it would probably be appropriate to abandon use of the shallow aquifer in the long term in favor of alternative sources of drinking water.

On the other hand, on a national scale, the BGS and DPHE (2001) survey showed that for tubewells <150 m deep, 27% exceeded 50 µg L-1 and 46% exceeded 10 µg L-1. This means that 73% and 54% of wells had concentrations below these limits respectively. Also, 24% of samples analyzed had concentrations below the analytical detection limit, usually 0.25 µg L-1 or 0.5 µg L-1. The districts of Thakurgaon, Barguna, Jaipurhat, Lalmonirhat, Natore, Nilphamari, Panchagarh, and Patuakhali all had no samples with arsenic >50 µg L-1 in the survey. This means that large-scale abandonment of tubewells in many parts of Bangladesh is unnecessary. The same holds for most other sedimentary aquifers of Asia where arsenic problems have been encountered. Major investments have been made in shallow tubewells across Asia and in many places these still constitute a reliable source of safe drinking water. There is also the potential for segregation of wells for different uses. High-arsenic wells could be used, for example, for washing and other domestic purposes, provided the wells are labeled adequately.

In many areas with high-arsenic groundwater domestic-scale treatment is being carried out in 74 75 order to remove or reduce the arsenic in drinking water supplies. These usually involve either aeration and sedimentation, coagulation and filtration, adsorption, ion exchange, or membrane filtration (Edwards 1994; Hering and others 1996; Ahmed 2003). While many of these techniques have been adapted for domestic use in affected areas and the technologies have improved significantly in recent years, issues remain over their sustainability and the disposal of high- arsenic waste products. They can provide a useful short-term solution in affected areas but are unlikely to form the basis of long-term mitigation strategies.

It should be borne in mind that the shallow high-arsenic groundwaters of the Bengal basin and other areas of South and East Asia also often have problems with a number of other trace elements that can be detrimental to health (for example high manganese, uranium, boron concentrations) or can cause problems with acceptability (high salinity, iron, ammonium concentrations). In arid areas (for example northern China) the shallow aquifers can also have problems with high fluoride concentrations. These other elements rarely correlate well with Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

arsenic and so shallow groundwaters of good quality in respect of arsenic concentrations may not necessarily be of good quality in other respects. Defining acceptability criteria for potable water supplies should therefore involve consideration of other potentially detrimental constituents and not just arsenic.

Dug Wells It has been traditionally accepted that shallow groundwater from open dug wells usually has low concentrations of arsenic. Evidence from Bangladesh (BGS and DPHE 2001), West Bengal (Chakraborti 2001), Myanmar (WRUD 2001), and Taiwan (Guo, Chen, and Greene 1994) indicates that many dug wells contain water complying with the WHO guideline value of 10 µg L-1 and most comply with the national standard of 50 µg L-1.

Despite this tendency, a rather different situation is apparent for groundwater from dug wells in Inner Mongolia. As shown in earlier section, dug wells in the Huhhot basin were found to contain groundwater with arsenic concentrations up to 560 µg L-1 in the area where tubewell arsenic concentrations were also high (Smedley and others 2003). Some recent studies in Bangladesh and Myanmar also appear to be finding higher arsenic concentrations in dug wells than previously appreciated, although supporting evidence has not yet been published to verify this. Some of the higher concentrations observed may be due to particulate rather than dissolved arsenic and concentrations may therefore vary depending on the turbidity of the groundwaters. Particulate matter could presumably be removed by some simple filtration or settling.

The findings suggest that in any given aquifer, concentrations of arsenic in dug wells cannot be assumed to have acceptably low arsenic concentrations without a testing program to confirm the concentration ranges. Care should also be taken in analyzing for arsenic that the relative contributions of dissolved and particulate arsenic are determined.

Since traditional large-diameter dug wells are normally open to the atmosphere and tap the shallowest levels of the aquifer, they are also potentially vulnerable to contamination from bacteria and other surface pollutants. Well siting and construction are therefore important criteria for well protection. Locating wells at some distance from latrines and other contaminant sources is important, as is installation of adequate sanitary seals. Installation of handpumps removes potential contamination from introduced buckets and disinfection of water can give protection against waterborne diseases. Periodic cleaning of the well can help to reduce suspended material.

One of the major constraints on the use of dug wells is likely to be well yields. This is especially the case in areas with relatively large water level fluctuations, where dug wells can dry up in the dry season. Poor water quality is linked to this to some extent, as particle settling becomes more difficult when wells dry up. Poor well yields may be the ultimate limit of the sustainability of dug wells in some areas. They are also not suitable in areas with thick layers of superficial clay.

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Evidence from the BGS and DPHE (2001) study of Bangladesh suggests that dug wells also contain potentially detrimental concentrations of uranium (up to 47 µg L-1). Dug wells had the highest concentrations of uranium identified in groundwaters from Bangladesh. Few epidemiological data exist to set a safe limit for uranium in drinking water, but new WHO guidelines include a provisional value for uranium of 9 µg L-1. Concentrations of nitrate also exceeded the WHO guideline value in some wells, presumably as a result of surface pollution.

Hence, for the reasons outlined above, dug wells may offer a suitable short-term solution to arsenic problems in some affected areas of Asia. However, they are unlikely to form a major component of long-term mitigation strategies for most areas.

Groundwater from Deep (Older) Aquifers Although analyses of groundwater from deep aquifers in the Bengal basin are still relatively limited, there appears sufficient information available to indicate that deep (older) aquifers in the region have much lower arsenic concentrations than many of the shallow aquifers above. The BGS and DPHE (2001) results suggested this for areas of south and east Bangladesh. CGWB (1999) found comparatively low concentrations in the deep aquifers of West Bengal. Van Geen, Ahmed, and others (2003) found similar results east of Dhaka. Data for other elements are also sparse, but where available they suggest that concentrations of manganese, uranium, and most other trace elements are also low in these deep aquifers. The older sediments therefore offer potentially good prospects as alternative sources of safe water for the Bengal basin. Van Geen, Ahmed, and others (2003) reported successes with take-up of groundwater supplied by six newly installed "deep" (60–140 m, but pre-Holocene) community wells in a badly affected part of Bangladesh. In the short time since the wells have been installed they are said to have proved popular with the local communities and women have been willing to walk up to hundreds of meters for their drinking water. The authors reported that such wells could provide drinking water for up to 500 people living within 150 m of the well in densely populated villages. Whether willingness to walk for supplies of drinking water would be a widespread phenomenon 76 77 in arsenic-affected areas is untested and deserves further investigation.

Considerable uncertainties remain over the deep aquifers, particularly with respect to (a) their lateral extent; (b) their depth ranges (as demonstrated by the van Geen, Ahmed, and others 2003 example); and (c) the variation in their hydraulic separation from the shallow aquifers. In many places these will not have been assessed if adequate supplies of water have been available at shallower depths.

An important risk with development of such deep (low-arsenic) aquifers is from potential drawdown of high-arsenic groundwater from shallower levels and contamination in the long term (decades or longer). This can occur if intervening layers of clay are thin or absent, or if seals on wells penetrating the deep aquifer are inadequate. Flow modeling of the Bangladesh aquifers (BGS and DPHE 2001) suggested that flow down to deep levels (100 m or more) is likely to be slow even under active pumping conditions. Modeling of aquifers in the Faridpur Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

area of central Bangladesh suggested that rates of groundwater movement to a well screened at 110–135 m depth from the water table at a lateral distance of 500 m would be of the order of 200 years. The rate was found to be highly dependent on local lithology.

Detailed hydrogeological investigations are therefore an essential prerequisite to the development of such aquifers on a regional scale. The quality of well construction also needs to be high. Subsequent groundwater quality monitoring for arsenic and a number of associated parameters also needs to be carried out. The greatest threat is from abstraction of large volumes of water for irrigation. Regulation of water abstraction should therefore be an integral part of water management policy to protect the deep aquifers. Introduction of abstraction licensing would be a logical step in policy development. Recording of well log information in a systematic way for newly drilled deep tubewells would also improve the knowledge base on the aquifers.

It is clear from investigations in other regions of South and East Asia that deep aquifers are not always low-arsenic aquifers. The Huhhot basin of Inner Mongolia is a case in point. Here, groundwater from (probably) Pleistocene aquifers at 100-400 m depth contains arsenic concentrations in the range <1–308 µg L-1. The variations reiterate the fact that aquifer depth is not an indicator of groundwater arsenic status. They also stress the need for detailed hydrogeological investigations in young sedimentary aquifers to identify sources and model their responses to groundwater development before any development takes place.

Surface Water

Rainwater Of all the sources of drinking water available for communities, rainwater is the least likely to face problems with arsenic contamination. Concentrations of dissolved solids will usually also be very low (perhaps too low). Rainwater harvesting offers a potential source of drinking water for individual households in areas where other sources are unsuitable. The method requires a suitable roof for collection and storage tank with adequate sealing to protect it from bacterial and algal contamination. It has been estimated that about half of households in Bangladesh have roofs suitable for collection of rainwater (for example galvanized iron, tiled surfaces) but that many of the poorer families would not be suitably equipped (Ahmed and Ahmed 2002). Rainwater harvesting can provide a seasonal supply of water for drinking but its period of use will be more limited in arid areas. Even so, provision of rainwater can still be beneficial even if available for only a few months of the year.

Rivers, Ponds Surface water usually has very low arsenic concentrations (typically <5 µg L-1). Exceptions include waters affected by mining activity and some geothermal areas. These are generally easily identified. As noted above, mining-contaminated waters are also usually localized to within a few kilometers of the mining activity (Smedley and Kinniburgh 2002), although those affected by geothermal inputs can be more widespread.

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Surface waters in the arsenic-affected regions of South and East Asia usually have low concentrations. Indeed, this is why there are many proponents of treated surface water as an option for safe water supply in Bangladesh and elsewhere. BGS and DPHE (2001) found concentrations of <2 µg L-1 in five river samples from the affected areas of Bangladesh. A sixth sample, from the Mahananda River flowing through the Chapai Nawabganj arsenic hotspot area of western Bangladesh, had a concentration of 29 µg L-1 (in March 1999) although repeat sampling (in December 1999) gave a value of 2.7 µg L-1, an order of magnitude lower. Whether this difference represents real seasonal changes is difficult to assess on the basis of such limited data. It does highlight the possibility that dry season groundwater discharge to the river systems could raise the surface water arsenic concentrations, especially in the worst-affected areas. Small rivers may be more affected than large rivers with greater volumes of water. However, oxidation of the reduced arsenic and consequent adsorption will lower the dissolved concentration being discharged to a large extent. The extent will depend upon, for example, the initial concentration and the river baseflow index (proportion of groundwater present).

A worse problem associated with the use of surface water is the potential risk from bacterial and other waterborne diseases arising from pollution. This problem means that surface water will probably always require adequate treatment to remove such hazards before use. At the village level this has been achieved through the use of pond sand filters. At a municipal level water treatment works can be installed for treatment of larger volumes. It is likely that any arsenic present in the initial waters will be removed by both of these treatment systems to concentrations below the drinking water thresholds. Other potential problems with the quality of surface water sources include inputs of nitrate and possibly organic compounds (pesticides, solvents) in some areas as a result of pollution. Concentrations of these will vary depending on local conditions and are difficult to remove by low-technology treatment methods.

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Table 15. Risks Associated with the Use of Drinking Water from Various Sources at Various Scales and Potential Mitigation Strategies

Source Risk for supply Mitigation strategy Household scale Village scale Urban scale

Shallow tubewells High arsenic Water testing; Water testing; Alternative (Holocene concentration alternative source alternative source source/municipal aquirfers) if concentration if concentration treatment plant if high high concentration high High concentrations Water testing; Water testing; Water testing; of other inorganic treatment difficult treatment difficult treatment plant constituents

(e.g. Mn, U, NH4, B) Deep tubewells Drawdown of n.a. Carry out prior site Carry out prior site (older sedimentary high-arsenic water investigations; investigations; aquifers) from shallow aquifers restrict use to restrict use to drinking water; drinking water; regulate regulate abstraction abstraction Dug wells Poor yields if wells Occasional use; Relocate/deepen n.a. dry up seasonally alternative source; wells walk to other wells Bacterial and other Disinfection, Well protection: n.a. waterborne diseases, filtration sanitary seals, high particulate loads handpump installation, water disinfection, periodic cleaning. Relocate wells away from pollution sources Other inorganic Difficult Water treatment n.a. water quality difficult. Relocate problems (e.g. nitrate, wells away from uranium, manganese) pollution sources (nitrate) Arsenic may exceed Water testing Water testing n.a. prescribed limits necessary. necessary. Treatment difficult Treatment difficult Surface water Potential bacterial Small-scale water Small-scale water Urban water problems, high treatment (e.g. pond treatment (pond treatment plants particulate loads sand filters) sand filters) Other pollutants (e.g. Difficult Difficult Urban water nitrate, pesticides) treatment plants Rainwater Seasonal, difficult in Partial supply n.a. n.a. arid areas Bacterial Storage protection, n.a. n.a. contamination disinfection n.a. Not applicable.

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5. Recommendations for Surveying and Monitoring

Overview lthough our ability to predict arsenic concentrations in groundwater from a given area or Aaquifer is still rather limited, knowledge of its occurrence and distribution has improved greatly over the last few years. We therefore probably know enough about where high concentrations tend to occur to make reasonable estimates of likely at-risk aquifers on a regional scale. Young sediments in alluvial and deltaic plains and inland basins as well as areas of mining activity and mineralization are obvious target areas for further evaluation. The guidelines for improving understanding of the arsenic problem and how to go about dealing with it are broadly the same in any region at increased risk from arsenic contamination. First, the scale of the problem needs to be assessed. Second, where problems exist, it is necessary to find out whether or not the situation is becoming worse with time. Third, where problems exist, it is necessary to identify the potential strategies or alternatives that are most appropriate for supplying safe (low-arsenic) water.

Central to these issues is arsenic testing. In any testing program it is important to distinguish between reconnaissance testing: that necessary for establishing the scale of a groundwater arsenic problem; and blanket testing: that required for compliance and health protection. Blanket testing involves the analysis of a sample of water from every well used for drinking water. For reconnaissance testing the numbers of samples need not be large; they should however be collected on a randomized basis. Monitoring is the repeat sampling of a given water source in order to assess temporal changes over a given timescale (as distinct from repeat testing to cross-check analytical results).

The quality of analytical results is also paramount; analysis of arsenic in water is by no means a trivial task, yet reliable analytical data are key to understanding the nature and scale of groundwater arsenic problems as well as dealing with them. Instigation of any new arsenic testing or monitoring program requires consideration of the analytical capability of the local 80 81 laboratories. In some cases, development of laboratory capability (for example quality assurance procedures, training, equipment upgrades, increased throughput) may be required and should be built into the testing program.

Appropriate mitigation responses for arsenic-affected regions will necessarily vary according to local geological and hydrogeological conditions, climate, population affected, and infrastructural factors. Surface water may or may not be available as an alternative. Other groundwater aquifers at different depths or in different locations may be available for use and need additional assessment. Decisions about what action to take in respect of the arsenic- affected aquifer depend on factors such as percentage of wells of unacceptable quality and range in concentrations (degree by which such standards such as 50 µg L-1 or 10 µg L-1 are exceeded). Below are outlined strategies for assessing the scale and distribution of arsenic problems in South and East Asian aquifers and for providing the necessary information as a basis for mitigation. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Aquifer Development and Well Testing

Aquifers of Low Potential Risk It follows from earlier section that our ability to define with accuracy where low-arsenic aquifers are likely to be is limited. Broadly, they are likely to include carbonate rocks, crystalline basement rocks, and other old (pre-Quaternary) sediments that have not been affected by mineralization or geothermal inputs. However, given the potential health risks associated with arsenic in drinking water, there is an argument for some randomized reconnaissance-scale testing of existing wells for arsenic in areas with little or no information, regardless of their perceived risk status (based on our current understanding). Provided the testing is random, survey results will provide information on the concentration ranges of arsenic to be expected in a given aquifer or region. Testing for arsenic alone may be sufficient in this case but other constituents of health concern could be included, depending on available budgets (for example iron, manganese, fluoride, nitrate; electrical conductance would also be useful).

Newly drilled boreholes should also include analysis of arsenic, at least on a subset of samples. Identification of significant numbers of samples with unacceptably high arsenic concentrations (say >10 µg L-1) should trigger a program for more extensive chemical analysis and geochemical investigation. This should involve analysis of a wider suite of analytes aimed at identifying the causes as well as the scale of the arsenic problem. Until a more detailed understanding of the arsenic concentrations in groundwaters of different aquifers in the developing world (and elsewhere) is available, including arsenic as a chemical analyte is a logical cautious approach. Although correlations between arsenic and other elements (such as iron) have often been noted in groundwaters, the correlations are usually insufficiently good to rely on proxy analytes.

Potentially High-Arsenic Aquifers As with any other area, aquifers at greater potential risk from high arsenic concentrations require the scale of any groundwater arsenic problem to be defined and the likelihood of future changes assessed. In undeveloped areas where little previous information is available and new groundwater supply projects are planned, merely testing for arsenic will determine the scale of the problem but will not define the processes involved. These need to be established to understand the aquifer better and ensure that groundwater use will be sustainable and that subsequent investment is appropriate. There is therefore a need for a detailed hydrogeological and geochemical investigation before any project implementation. This may involve collation of all available hydrogeological data (for example well depths, water levels, aquifer physical characteristics, pumping rates, groundwater yields), collection of new water samples for more detailed chemical analysis (a more comprehensive range of analytes), and assessment of sediment chemistry and mineralogy (table 16 see page 82). Such studies can be time consuming and may have large cost implications. In some countries local institutions may be equipped to carry out these investigations. In others, expertise from external organizations may be required. The size of the prior investigation work should be commensurate with the size of the intended water supply program, amounting to say 5-10% of the projected implementation cost.

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Table 16. Arsenic Testing Strategies in Potential High-Arsenic Groundwater Provinces

Area Existing drinking water wells New drinking water wells

Untested areas Randomized reconnaissance Initial hydrogeological and groundwater arsenic survey. Scale of geochemical site/regional survey dependent on number of wells, investigation. Test drilling; areal extent of aquifer, number of analysis of groundwater for arsenic people served. Stratified random during drilling and on completion. approach (stratification based on geology, well depth). Blanket arsenic testing of wells used for public supply, schools, hospitals. Established Blanket testing for arsenic. Decision to drill new wells based groundwater on previous results. Alternatives arsenic problem necessary in badly affected areas aquifers. In marginal cases, selection of well location, depth, etc., based on previous information. Analysis for arsenic on completion.

In areas where groundwater is already in use but water quality data are limited or absent, reconnaissance testing is necessary in the first instance to define the scale of any arsenic problem.

Defining the concentration ranges and spatial distributions of arsenic in groundwater is best achieved by some sort of randomized groundwater survey (most importantly, not based on previous knowledge of groundwater arsenic concentrations). The scale of groundwater testing should be commensurate with the numbers of people dependent on the water supply and 82 83 potentially affected by it. In Bangladesh the density of wells sampled in the BGS and DPHE (2001) national survey was 1 per 37 km2. The number of samples tested represented only around 0.05% of the tubewells believed to be present in Bangladesh. The survey proved inadequate to pick out many of the localized arsenic hotspots that occur in some areas but did serve to identify the worst-affected parts of the country and the depth ranges of the tubewells with the worst problems. It therefore highlighted priority areas for mitigation. These were seen to be the southeastern part of Bangladesh. Subsequent surveys by various organizations may have refined the data distributions, but do not appear to have changed the overall conclusions concerning the worst-affected areas and hence the priority areas for mitigation.

The BGS and DPHE (2001) survey statistics indicated that 27% of shallow tubewells in Bangladesh had arsenic concentrations >50 µg L-1. This figure compares well with an earlier estimate of exceedances above 50 µg L-1 for the whole country (26%) based on data from BGS, DPHE, and other organizations (DPHE-BGS-MML 1999). Of course, these data just provide summary statistics and define regional distributions and do not define concentrations in Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

individual wells. This latter is needed for compliance testing. The BGS and DPHE (2001) survey showed the high degree of spatial variability in groundwater arsenic concentrations and, as with many other surveys, demonstrated the need for testing of individual wells used for drinking water.

Wells used for irrigation should also be tested ultimately as these represent a potential, though less direct and as yet unquantified, threat to health. They are, however, of a lower priority.

Survey samples need to be georeferenced (latitude and longitude data or other national grid) and notes made of aquifer type, well depth, well age, well owner, well number if available, and location. Other aquifers present in the region (for example the deep (Pleistocene) aquifer in Bangladesh) should also be tested on a randomized basis to assess their potential as alternatives. The data need to be analyzed to assess whether statistically significant variations exist in variables such as well depth, well age, and sediment type. The data should be incorporated into a database for ready storage and manipulation. The data should also be mapped.

In areas where some initial surveys have been carried out and where arsenic problems have been recognized, spatial patterns may be discernible. If these are significant, they should highlight where mitigation needs to be targeted and where not. Past experience shows that many arsenic-affected aquifers have highly variable groundwater arsenic concentrations on a local scale. In this case and where concentrations are high, blanket testing of wells will most probably be required. This is best achieved by laboratory analysis using reliable local facilities equipped for rapid throughput of samples. Where these are absent, facilities should be set up and equipped for analysis of arsenic and a range of other diagnostic elements. Where setting up of laboratories is not possible or where the scale of testing is very large and facilities inadequate to cope with the scale of testing required (for example Bangladesh), field test kits can be an alternative. The technology for these has improved in the last few years and while older kits were barely able to determine concentrations of arsenic at less than 100 µg L-1, the sensitivity of newer designs is better. Wherever possible, capability to test reliably at 10 µg L-1 should be aimed for. Wherever possible, a subset of samples analyzed by field test kits (say 10%) should be cross-checked by a reliable laboratory analysis. A premium should be placed on reliability of analytical results and quality assurance should be a critical and ongoing undertaking with any groundwater testing or monitoring program (box 1 see page 31).

Past hydrogeochemical investigations of high-arsenic aquifers have shown correlations with other elements (for example iron, manganese) but these are rarely sufficiently significant to be useful in a practical sense. Results indicate that there are no suitable reliable proxy indicators for arsenic concentration in groundwater.

Deep Aquifers below High-Arsenic Aquifers As the deep (Pleistocene) aquifers of Bangladesh, West Bengal, and Nepal are identified as being potentially suitable sources for drinking water supply and also being vulnerable to contamination from above, it is important that future development of such sources on a major

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scale is preceded by detailed hydrogeological and hydrochemical investigations. These should include sedimentological studies to assess physical aquifer dimensions; pumping tests and groundwater flow modeling to determine flow mechanisms and assess the likelihood of drawdown from shallow levels; and testing of a wide range of chemical parameters to determine controlling processes and assess other elements of potential health concern.

During development of such deep aquifers, it is of importance to collate and document as much hydrogeological information as possible. In the case of Bangladesh, for instance, collection of information such as sediment texture (sand, silt, clay) and sediment color would be helpful and would demand little extra cost. Texture gives information on water storage capacity and sediment history. In the Bengal basin, experience has shown that reddish-colored sediments at depth are most likely to contain groundwater with low concentrations of arsenic and iron. Color gives information on redox conditions and stratigraphy and can help date the aquifers. The redox conditions and aquifer age have both proven critical to the quality of water with respect to many other elements of health concern as well as arsenic. Databasing of such information is also important.

Collection of such information on these potentially valuable aquifers is of great importance, but should not serve to delay mitigation efforts in areas with recognized arsenic problems.

Monitoring Monitoring can be a major and expensive task. Production of good analytical data is paramount and, as stated above, analysis of arsenic is difficult (box 1 see page 31). Analytical problems should therefore be expected and variations viewed with skepticism until found to be statistically significant. As a first approximation, it is reasonable to assume that temporal changes will not be major in the short term and that an initial analysis is likely to be representative for a given groundwater source (unless, as stated above, the analysis is suspect). 84 85 Hence, single analyses can give an indication of fitness for drinking water in the absence of time series information. In general, larger fluctuations in chemical composition can be expected at shallower levels where groundwater throughputs are higher and compositions more strongly influenced by changing groundwater head gradients. Chemical compositions in deeper aquifers can be expected to be more stable and changes are likely to be dampened and over longer timescales, unless affected directly by flow (leakage) from other neighboring aquifers.

Shallow Sedimentary Aquifers with Recognized Arsenic Problems On the scale of arsenic problems recognized in countries such as Bangladesh, even initial testing for arsenic is a major logistical and analytical undertaking. Compliance monitoring of tubewells and dug wells defined to be initially "safe" is an even more demanding, and in many cases impossible, task. The scale of monitoring possible in any given region will depend on the numbers of operating drinking water wells and the resources (funds, analytical capabilities) available. Monitoring should be of secondary priority to initial testing but is a necessary Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

undertaking given the current uncertainty in temporal variations in arsenic concentrations. Monitoring is required not only for raw groundwater from shallow tubewells but also for water from dug wells (especially those with concentrations >50 µg L-1, which should be retested to verify the concentration) and for treated water that has been through an arsenic removal plant. Recent investigations have shown that not all treated groundwaters have acceptably low concentrations of arsenic (Mahmud and Nuruzzaman, 2003).

The concentration ranges chosen for monitoring wells vary according to the reason for monitoring. For compliance monitoring, priority would be appropriate for wells with concentrations of the order to 10-50 µg L-1 and wells used for major public supply. For research purposes, monitoring of groundwater sources with concentrations outside this range (both low and high) would be of value.

The frequency of monitoring also depends on the objective of the monitoring exercise. Assessment of short-term (diurnal) changes requires frequent monitoring over periods of hours. Observation of seasonal changes requires weekly or fortnightly monitoring. Longer-term changes require monitoring annually or biannually.

Deep (Older) Aquifers in Arsenic-Prone Areas The deep aquifers of the Bengal basin represent a special case in that they appear to be largely free of arsenic and are a potentially important alternative source of drinking water, yet their vulnerability to contamination from the high-arsenic shallower aquifer is in large part untested. An important component of a groundwater protection policy for the deep aquifers of the Bengal basin (and other aquifers vulnerable to such leakage from contaminated aquifers) is the regular monitoring of groundwater quality in order to detect any deterioration in the medium or long term and to take mitigating action if necessary. Annual or biannual monitoring of such tubewells used for public water supply would be appropriate. Arsenic would be the most important analyte but a range of other parameters (water level, electrical conductance, iron, manganese) would also be useful. Monitoring for these selected parameters should be conducted for several years (five and preferably longer). That is not to say that the tubewells should not be used until a suitable run of time series data have been collected. A subset of samples should also be tested for all health-related parameters. Such monitoring can be a large task, but the number of deep wells installed is likely to be much smaller than shallow handpumped tubewells.

Further Research Needed to Assess Temporal Variations Sufficient uncertainty remains over the temporal variations in arsenic concentrations in groundwaters in affected aquifers that research programs need to be undertaken in specific areas to obtain further monitoring data. On a research scale, this is a relatively easy program to set up and could have been instigated in many of the affected areas shortly after their discovery. Accumulated data from the regular monitoring of selected wells over periods of months or a few years would have helped to identify the periodicity, scale, and causes of any observed temporal variations and resolve many of the uncertainties that persist.

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Ideally, a program involving monthly monitoring of selected tubewells in affected areas (monitoring for arsenic as well as water level, electrical conductance, iron, manganese) should be undertaken in some areas in order to identify seasonal trends. Such monitoring should be over the course of several years (two minimum). Monitoring of groundwater quality at different depths in recognized high-arsenic aquifers is also required. Such programs have been started in Bangladesh and elsewhere but more monitoring is needed to collect a larger body of time series data. Studies of diurnal variations in heavily used tubewells are also required to establish water quality variations over the course of days.

Little information is so far available on the temporal variation in arsenic concentration in dug wells. Specific monitoring programs in a few shallow wells, sampled approximately monthly, can be carried out to establish temporal variations, especially in relation to water level changes.

Seasonal monitoring of surface waters in areas with badly affected aquifers would help to establish whether temporal variations exist and whether they are sufficiently significant to cause consistent exceedances above national standards and the WHO guideline value. Monthly sampling of filtered (0.45 µm pore size or less) river water over the period of a year would provide information on whether variations are significant in an operational sense. It is stressed that analysis of unfiltered water is likely to produce highly variable results depending on the turbidity of the water since arsenic analysis usually involves acidification, and at any given time the result will include suspended as well as dissolved arsenic.

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6. Concluding Remarks

igh arsenic concentrations recognized in many parts of Asia and elsewhere are dominantly Hfound in groundwater, and many of the health consequences encountered have emerged in relatively recent years as a result of the increased use of groundwater from tubewells for drinking and irrigation. In terms of numbers of groundwater sources affected and populations at risk problems are greatest in Bangladesh, but major problems have also been identified in India (West Bengal, and more recently Assam, Arunachal Pradesh, Bihar, Manipur, Meghalaya, Nagaland, Uttar Pradesh and Tripura), northern China, Vietnam, Taiwan, Thailand, Cambodia, Myanmar, and Nepal. Occasional high-arsenic groundwaters have also been found in Pakistan, although the occurrences there appear to be less widespread. High-arsenic groundwaters in affected areas tend to be found in alluvial or deltaic aquifers or in inland basins. Hence, much of the distribution is linked to the occurrence of young (Quaternary) sediments in the region's large alluvial and deltaic plains (Bengal basin, Irrawaddy delta, Mekong valley, Red River delta, Indus plain, Yellow River plain). Although groundwater arsenic problems have been detected in some middle sections of the Indus and Mekong valleys, such problems have apparently not emerged in the lower reaches (deltaic areas). Whether this represents lack of testing or whether arsenic problems do not occur there is as yet uncertain. However, the young Quaternary aquifers most susceptible to developing groundwater arsenic problems appear to be less used in these areas as a result of poor well yields or high groundwater salinity. Other Quaternary sedimentary aquifers in Asia have not been investigated and so their arsenic status is unknown. Some localized groundwater arsenic problems relate to ore mineralization and mining activity (for example peninsular Thailand; Madhya Pradesh, India).

One of the key hydrogeochemical advances of the last few years has been in the better understanding of the diverse mechanisms of arsenic mobilization in groundwater, as well its derivation from different mineral sources. The most important mineral sources in aquifers are metal oxides (especially iron oxides) and sulfide minerals (especially pyrite, FeS2). Release of arsenic from sediments to groundwater can be initiated as a result of the development of reducing (anaerobic) conditions, leading to the desorption of arsenic from iron oxides and breakdown of the oxides themselves. Such reducing conditions are commonly found in fine-grained deltaic, alluvial, and lacustrine sediments.

Release of arsenic can also occur in groundwaters with high pH (>8) in oxidizing (aerobic) conditions. These tend to occur in arid and semiarid settings with pH increases resulting from extensive mineral reaction and evaporation. High-arsenic groundwaters with this type of association have not been reported in Quaternary aquifers in South and East Asia but are found in some arid inland basins in the Americas (western United States, Mexico, Argentina). Analogous conditions could occur in some arid parts of the region, such as northern China or western Pakistan, but there is as yet no evidence for this.

Mobilization of arsenic in mineralized and mining areas is linked to the oxidation of sulfide minerals. Here, occurrences can affect both surface waters and groundwaters but the affected areas are typically localized (a few kilometers around the mineralized zone) as a result of the normally strong capacity of soils and aerobic sediments to adsorb arsenic.

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Despite this improved understanding of the occurrences and distribution of arsenic in groundwater, there remains much uncertainty regarding the nature of the source, mobilization, and transport of the element in aquifers. It is only in the last few years that detailed hydrogeochemical investigations have been carried out in affected regions. Earlier responses to water-related arsenic problems typically involved engineering solutions or finding alternative water sources, with little emphasis on research. It is worthy of note that, despite the major epidemiological investigations that have been carried out in Taiwan since the discovery of arsenic-related problems there in the 1960s, there has been little hydrogeochemical research carried out in the region. Even today, the aquifers of Taiwan are poorly documented and the arsenic occurrence little understood.

One of the important findings of recent detailed aquifer surveys has been the large degree of spatial variability in arsenic concentrations, even over distances of a few hundred meters. This means that predictability of arsenic concentrations on a local scale is poor (and probably will always be so). Hence, blanket testing of individual wells in affected areas is necessary. This can be a major task in countries like Bangladesh where the scale of contamination is large. There is also uncertainty in the temporal variability of arsenic concentrations in groundwater as very little groundwater monitoring has been carried out. Some studies have noted unexpectedly large temporal variations over various timescales but the supporting data are often sparse and inaccessible and so these reports cannot be relied upon. More controlled monitoring of affected groundwaters is required to determine the variability in the short term (daily), the medium term (seasonally), and the long term (years, decades).

The emerging arsenic problems have revealed the dangers of groundwater development without consideration of water quality in tandem with water quantity. Understanding of the risk factors involved in development of high-arsenic groundwaters has allowed targeting those aquifers perceived to be most susceptible to developing groundwater arsenic problems in recent years (for example Quaternary sediments in Cambodia, Myanmar, Nepal). However, the toxicity of arsenic is such that it should also be given greater attention in other aquifers used for drinking 88 89 water supply. There is an argument for routine testing for arsenic in all new wells provided in major groundwater development projects, regardless of aquifer type. Randomized reconnaissance-scale sampling for arsenic is also recommended for existing public supply wells in all aquifer types where no arsenic data currently exist in order to obtain basic statistics on the distribution of arsenic concentrations. Groundwater development in previously unexploited but potentially vulnerable young sedimentary aquifers needs to be preceded by detailed hydrogeological and hydrochemical investigations to ensure that groundwater will be of sufficiently high and sustainable quality. The scale of investigations should be commensurate with the scale of proposed development. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Glossary

Adsorption. Adherence of a chemical or compound to a solid surface.

Alluvial. Deposited by rivers.

Aquifer. Water-bearing rock formation.

Desorption. Release of a chemical or compound from a solid surface (opposite of adsorption).

Distal. Remote from the origin (for example sediments in lower reaches of a delta).

Geothermal. Pertaining to the internal heat of the earth. Geothermal zones are areas of high heat flow, where hot water or steam issue at the earth's surface. They are found close to tectonic plate boundaries or associated with volcanic systems within plates. Heat sources for geothermal systems may be from magmatism, metamorphism, or tectonic movements.

Pyrite. Iron sulfide (FeS2), also known as fool's gold. Occurs commonly in zones of ore mineralization and in sediments in reducing conditions.

Quaternary. Period of geological time extending from about 2 million years ago to the present day. Divided into the earliest period, the Pleistocene, and the subsequent Holocene (the last 13,000 years). Strata of Quaternary age are very young on a geological timescale.

Mineralization. The presence of ore or non-ore minerals in host rocks, concentrated as veins, or as replacements of existing minerals or disseminated occurrences; typically gives rise to rocks with high concentrations of some of the rarer elements.

Redox reactions. Coupled chemical oxidation and reduction reactions involving the exchange of electrons. Many elements have changeable redox states; in groundwater the most important redox reactions involve the oxidation or reduction of iron and manganese, introduction or consumption of nitrogen compounds (including nitrate), introduction or consumption of oxygen (including dissolved oxygen), and consumption of organic carbon.

Reducing conditions. Anaerobic conditions, formed where nearly all of the oxygen has been consumed by reactions such as oxidation of organic matter or of sulfide; reducing conditions commonly occur in confined aquifers.

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This paper was prepared by Amal Talbi (World Bank) with contributions from Karin Kemper (World Bank), Khawaja Minnatullah (World Bank/WSP), and Stephen #oster and Albert Tuinhof (World Bank Groundwater Management Advisory Team – GWMATE). VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Summary

1. This paper focuses on the operational responses to natural groundwater contamination in affected countries of South and East Asia. The paper first outlines the health effects of arsenic ingested through water and the different recommended permissible values of maximum concentration of arsenic in drinking water, and presents a critical analysis of the current status of epidemiological knowledge.

2. This is followed by a comprehensive presentation of the operational responses implemented to mitigate arsenic contamination in the study countries, and an assessment of such operational responses in the overall context of the water supply sector. Finally, an attempt is made to highlight the political economy of arsenic mitigation and to assess the options for addressing arsenic from this perspective.

3. The paper also extracts the major lessons learned when implementing short-term and long-term mitigation measures in South and East Asian countries. These are divided into technical, financial and economic, social and cultural, and institutional issues, and are summarized in overview matrices in annex 2.

4. The outcome of the paper is a tool that aims to help decisionmakers in government, multilateral and bilateral institutions, nongovernmental organizations, academics, and water practitioners in general address arsenic contamination of groundwater. By bringing together information from a variety of sources, including published and unpublished literature, results of a specially administered survey, and outcomes of a regional workshop held in Kathmandu in 2004, the paper collates, synthesizes, and makes accessible the vast range of arsenic-related information currently available in order to inform and facilitate concrete operational responses to the arsenic issue. 98 99 VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

1. Introduction

atural arsenic contamination of groundwater affects a number of countries worldwide, and Nspecifically in South and East Asia. This paper first reviews the operational responses to natural arsenic contamination of groundwater in Asian countries that have hitherto been developed and carried out; second, it analyzes the success and failure of these responses; and third, it presents practical guidance for stakeholders, at either the country or project level, to better address the arsenic issue. This is critical since governments, the World Bank, and other development partners implement water projects in this region and are responsible for providing safe drinking water. Stakeholders need to be aware of this contamination, have tools to identify it, and have practical information to provide a proactive response or, where the contamination has been identified at a later stage, a reactive response.

The countries in South and East Asia so far identified as affected by natural arsenic contamination of groundwater are Bangladesh, Cambodia, China (including Taiwan), India, Lao People's Democratic Republic (PDR), Myanmar, Nepal, Pakistan, and Vietnam.

This paper deals with natural arsenic contamination rather than contamination of mining and geothermal origins, and with rural rather than urban areas. The focus on natural contamination, which is due to the release of arsenic from sediment to water, stems from the fact that this contamination is still unpredictable, and is thus far more difficult to address than contamination of mining and geothermal origin. Similarly, contamination in rural areas presents a greater challenge than that faced in more compact urban areas.

The operational responses to deal with arsenic that have been implemented to date include screening of tubewells, identification and treatment of those affected by contamination, sharing of arsenic-safe wells, awareness raising, and development of alternative water provision through, for instance, dug wells, pond sand filters, rainwater harvesting, arsenic removal plants, and tapping deep groundwater.

The paper is structured in four chapters. Chapter 1 presents the health effects and the recommended maximum permissible values of arsenic in water. A critical analysis is provided regarding the lack of epidemiological studies on the health effects of arsenic and the current 100 101 uncertainty regarding safe levels of arsenic in drinking water.

Chapter 2 presents the operational responses implemented in South and East Asian countries. An assessment is made of the lessons learned and the remaining issues on which no conclusions can yet been drawn.

Chapter 3 discusses arsenic mitigation in the overall context of water supply, including an analysis of the priority accorded to arsenic contamination.

Chapter 4 analyzes incentives for stakeholders to be active (or inactive) in implementing operational responses to arsenic contamination. These incentives influence the political economy and are drawn from the lessons learned and other issues analyzed in chapter 2. Due to the large number of countries affected, and recognizing that the political economy varies from country to country, this paper does not address political economy in depth for each individual country but rather discusses incentives generally.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

2. Arsenic: Health Effects, Recommended Values, and National Standards

rsenic is a substance that is carcinogenic – capable of causing cancer. Organic arsenic Acompounds are less toxic than inorganic compounds, the latter being more commonly found in natural arsenic water contamination. The recommended standards for the maximum acceptable dose of arsenic are based on health risks, but the lack of epidemiological data on low doses of exposure makes the health risks difficult to assess with certainty.

This chapter presents international and national standards for arsenic intake in drinking and irrigation water; the major assumptions regarding the interpretation of epidemiological data used to assess the recommended maximum permissible values and standards; the major health effects of arsenic; the status of the debate on arsenic intake from the food chain; and the effects of trace elements on reducing or increasing arsenic toxicity.

International and National Standards for Arsenic Intake Regarding arsenic concentration in irrigation water, neither international agencies nor individual countries propose any recommended maximum permissible values. For drinking water, however, due to the carcinogenic nature of the substance, the World Health Organization (WHO) has issued a provisional guideline recommending a maximum permissible arsenic concentration of 10 µg L-1 (micrograms per liter). WHO guidelines are meant to be used as a basis for setting national standards to ensure the safety of public water supplies and the guideline values recommended are not mandatory limits. Such limits are meant to be set by national authorities, considering local environmental, social, economic, and cultural conditions.

Most developed countries have adopted the provisional guideline value as a national standard for arsenic in drinking water. On the other hand, most developing countries still use the former WHO-recommended concentration of 50 µg L-1 as their national standard. Table 1 uses a sample of countries to illustrate the range of values adopted (7 µg L-1 to 50 µg L-1).

102 103 Table 1. Currently Accepted National Standards of Selected Countries for Arsenic in Drinking Water

Country/region Standard: µg L-1 Country Standard: µg L-1

Australia (1997) 7 Bangladesh (1997) 50 European Union (1998) 10 Cambodia 50 Japan (1993) 10 China 50 USA (2002) 10 India 50 Vietnam 10 Lao PDR (1999) 50 Canada 25 Myanmar 50 Nepal 50 Pakistan 50

Source: Ahmed 2003. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The fact that some countries have adopted the recommended maximum permissible value of 10 µg L-1 while others still use a value of 50 µg L-1 is related to the chronology of recommended maximum permissible values proposed by the WHO (table 2). In 1993 the WHO recommended lowering the maximum permissible value from 50 µg L-1 to 10 µg L-1 as a precautionary measure because of the carcinogenic effects of arsenic, especially regarding internal cancers. So far most developed countries have adopted this new recommended value as a national standard (table 1).

Most developing countries, however, have not lowered their national standards because they feel they could not afford the associated economic costs, including treatment and monitoring costs. For further discussion of this issue see Paper 4.

Table 2. Chronology of Recommended WHO Values for Arsenic in Drinking Water

1958 First WHO International Drinking Water Standard: 200 µg L-1 1963 WHO recommend lowering guide value to 50 µg L-1 1974, 1984 Affirmation of 50 µg L-1 as guide value 1984 WHO Guidelines replace International Drinking Water Standard, providing a basis for national standards by individual countries 1993 WHO provisional guideline recommends lowering guide value to 10 µg L-1

The United States Environmental Protection Agency (EPA) conducted an economic study with concentrations of 3, 5, 10, and 20 µg L-1 and found that, given the conditions prevailing in the United States of America, the recommended maximum permissible value of 10 µg L-1 represented the best trade-off among health risks, the ability of people to pay for safe water, and the availability of water treatment technology. The standard of 10 µg L-1 will be further lowered as treatment technology becomes more affordable. The WHO-recommended maximum permissible value for carcinogenic substances is usually related to acceptable health risk, defined as that occurring when the excess lifetime risk for cancer equals 10-5 (that is, 1 person in 100,000). However, in the case of arsenic, the EPA estimates that this risk would mean a standard as low as 0.17 µg L-1 (Ahmed 2003), which is considered far too expensive even for industrial countries to achieve.

The health risks used in the EPA estimate were based on data from an epidemiological study conducted in Taiwan. Since the study only considered the risk of skin cancer and lacked data on internal cancers, and because of several conservative assumptions in the EPA model, the health risks may have been underestimated. On the other hand, the actual rate of skin cancer may be overestimated because of possible simultaneous exposure to other carcinogenic compounds (Ahmed 2003).

Even though the exact health effects of an arsenic concentration of 50 µg L-1 have not been quantified, many correlations between internal cancer and low concentration of arsenic have been

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

found. Therefore it is important that localized epidemiological studies are carried out in a strategic manner, to more clearly inform decisionmakers.

Major Limitations of Existing Epidemiological Studies Humans are exposed to different forms of arsenic from the atmosphere, food, and water. An important distinction needs to be made between inorganic and organic arsenic, inorganic arsenic being the carcinogenic form, though organic arsenic also has adverse health effects. Inorganic arsenic is the only form that occurs in water, and is therefore the focus of this study.1 The study of kinetics and metabolisms of arsenicals in humans is complex due to the following issues (ATSDR 2002):

• Physicochemical properties and bioavailability vary with form of arsenic. • There are many routes of exposure (inhalation, ingestion, and dermal). • The intake of arsenic can be either acute or chronic. • Length of exposure can be short, medium, or long term. • The differing susceptibility to arsenic between humans and animals makes the quantitative dose response data from animals unreliable for determining levels of significant human exposure.

This paper focuses on the human health effects of chronic exposure to arsenic by ingestion. This focus has been chosen as the main source of arsenic poisoning is through contaminated groundwater, and the secondary source is through the food chain.

In the literature, the health effects of arsenic have been estimated from data from various regions (for example Australia, Argentina, Chile, Taiwan). Nevertheless, clear linkages between a given concentration of arsenic in drinking water and its health effects are difficult because of the following issues:

104 105 • In most cases of ingestion, the chemical forms of arsenic are unknown. • Most studies do not consider the volume of drinking water consumed. • Most studies do not report the temporal variations of the concentration of arsenic in the source over a long period. • There is a lack of data about the relative importance of arsenic intake from sources other than drinking water, in particular from the food chain.

Because of these issues, it is difficult to assess the exact health effects for a particular concentration of arsenic in groundwater. The available epidemiological studies present the health effects based on the exposure dose of arsenic, which is defined as the quantity of arsenic that is ingested per kg of weight per day and can be calculated according to equation 1.

1 See Paper 1 regarding organic and inorganic arsenic and the oxidation state of inorganic arsenic. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Equation 1. Health Effects of Arsenic Exposure Dose

ED = C * DI BW

Where: ED = exposure dose (mg kg-1 day-1) C = exposure concentration (mg L-1) DI = daily intake of water (L day-1) BW = body weight (kg)

When estimating exposure dose one of the usual assumptions is that daily water intake is 2 liters (Ahmed 2003; ATSDR 2002; WHO 2001b). However, based on the literature reviewed, daily intake in rural areas tends to be higher, and varies from 3 to 5 liters (Ahmed 2003; Masud 2000). Importantly, health risk estimations increase as daily intake increases.

It appears that improved nutrition increases tolerance to arsenic contamination. For example, in some arsenic-affected villages of West Bengal in India, families with access to nutritious food show almost no arsenical skin lesions compared with undernourished families, despite the fact that both are consuming the same arsenic-contaminated water. Hence the poor, who are more likely to be malnourished, tend to be most affected by arsenic contamination.

In summary, existing epidemiological studies are still often based on simplifying assumptions that introduce a number of uncertainties when quantifying the relationship between the concentration of arsenic and health effects.

Major Health Effects This section focuses on the major health effects of arsenic, which include skin lesions, blackfoot disease, diabetes, hypertension, skin cancers, and internal cancers. In annex 5 a detailed matrix of the health effects is provided with (when available) the exposure dose and the concentration of arsenic based on equation 1 with sensitivity analysis of the daily water intake (2, 3, and 5 liters).

Arsenic has various health effects ranging from arsenicosis to skin cancers and internal cancers. However, so far there is still no widely accepted definition of what constitutes arsenicosis, the term used for the pattern of skin changes that occurs after chronic ingestion of arsenic. These skin changes are usually the first symptoms to appear in the presence of high concentrations of arsenic in drinking water. However, two epidemiological studies of chronic ingestion suggest that these lesions could appear for concentrations lower than 100 µg L-1. Another primary noncancer health effect is blackfoot disease, which was first observed in Taiwan. This peripheral vascular disease leads, eventually, to a dry gangrene and the spontaneous amputation of affected extremities (Kaufmann and others 2001).

The cancer effects of chronic exposure to arsenic through drinking water include skin cancers and internal cancers (lung, bladder, and kidney). In 1988 the EPA estimated that in the United

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

States chronic ingestion of 50 µg L-1 results in a skin cancer rate of 1 in 400; in 1992, the EPA estimated that the internal cancer mortality risk is about 1.3 in 100 at 50 µg L-1. In 1999 the United States National Research Council (NRC) estimated the overall cancer mortality risk to be about 1 in 100 at 50 µg L-1 (NRC 1999; Smith and others 2002).

Internal cancers are of primary concern since they account for most fatalities resulting from chronic ingestion of arsenic through drinking water. Skin cancers are not usually fatal if they are identified at an early stage, and their external symptoms make diagnosis more likely than with internal cancers.

Arsenic Ingested through the Food Chain

The proportion of inorganic arsenic ingested through food may be significant, even when the arsenic concentration of drinking water is higher than 50 µg L-1. For example, a recent study conducted in Mexico (Del Razo and others 2002), where the concentration of arsenic in drinking water was as high as 400 µg L-1, found that even so 30% of inorganic arsenic intake came from food.

The quantities of organic and inorganic arsenic in food should always be quantified, since the form of arsenic affects its bioavailability and thus its toxicity to humans. Unlike water, where arsenic is always inorganic, food can contain either organic or inorganic arsenic. Different studies have found different proportions of organic and inorganic arsenic in food. For example, an EPA study found the percentages of inorganic arsenic in rice, vegetables, and fruit to be 35%, 5%, and 10% respectively (EPA 1988); a study conducted in West Bengal found the percentages of inorganic arsenic in rice and vegetables to be 95% and 5% respectively (Roychowdhury, Tokunaga, and Ando 2003); and another Bengali study found the percentage of inorganic arsenic in rice to be 43.8% (Roychowdhury and others 2002). This wide range of values shows that the total amount of arsenic (both organic and inorganic) in a food sample cannot be taken as an accurate indication of the toxicity of the sample. 106 107 In soil irrigated with water having significant arsenic concentrations, higher concentrations of arsenic were found in the peel or skin of the crops, while lower arsenic concentration were found in the edible part of the raw crops. A study by Das and others (2004) found the arsenic content of some vegetables to be greater than the recommended limit of 1 mg kg-1 set in the United Kingdom and Australia. Another concern regarding the use of contaminated water for irrigation is the effect of arsenic on the yield, though this has as yet received little study. There is no current precise definition of what concentration of arsenic in irrigation water would have a quantifiable impact on agriculture yield or on human health.

The amount of arsenic in food seems to be related to both the amount of arsenic in the water used for cooking and the cooking process used. For example, a study (Roychowdhury and others 2002) showed that the concentration of arsenic in cooked rice was higher than that in raw rice and absorbed water combined, suggesting a chelating effect by rice grains. Due to water evaporation Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

during the cooking process, the quantity of water used is important and this also affects the amount of arsenic in food. In addition, another study (Devesa and others 2001) reported no transformation of arsenic at temperatures up to 120°C. Thus, the boiling process used to cook the food probably does not alter the chemical form of arsenic nor the amount of inorganic arsenic in the food at the end of the cooking process (Del Razo and others 2002).

There is no standard maximum level of arsenic in food in South and East Asian countries. In the United Kingdom and Australia the maximum food hygiene standard for the arsenic level in food is 1 mg of arsenic per kg (Warren and others 2003).

Studies related to the interaction of arsenic with other elements are limited. So far, most studies have focused on fluoride, selenium, and zinc. The main findings are that (a) fluoride neither increases nor decreases arsenic toxicity; (b) selenium and arsenic might reduce each other's effects in the body; and (c) a deficit of zinc might increase the toxicity of arsenic. Thus it seems that other elements may play a role in the effective toxicity of arsenic in drinking water.

So far, the intake of arsenic from food seems to depend more on the amount of arsenic in the cooking water than in the water used for watering crops. However, research is still needed to fully confirm that cooking water is more detrimental than irrigation water in the accumulation of arsenic in the food chain.

Operational Responses of Countries in South and East Asia

The operational responses implemented thus far in South and East Asian countries are difficult to compare because most of the information available is for South Asia, particularly Bangladesh, Nepal, and West Bengal in India. Information related to East Asian countries is much more difficult to find in international literature. Therefore, in order to collect more information on operational responses in South and East Asian countries, the study team sent a questionnaire to major stakeholders. The summary of the questionnaire responses is provided in annex 3. In addition, in the context of the study, the World Bank/WSP Regional Operational Responses to Arsenic Workshop was held in Nepal, 26–27 April 2004. The preliminary results of the study were shared with 50 participants representing 7 out of the 11 countries facing arsenic contamination, as well as international organizations, donors, and researchers. The major information and data collected are included in this report.

A summary of operational responses implemented in South and East Asian countries is presented in annex 1.

Initial Responses towards Suspected Arsenic Contamination Initial responses towards suspected arsenic contamination include well screening and identification of water contamination in tubewells, switching from contaminated to arsenic-safe

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

wells, painting of tubewells, awareness raising, and identification and treatment of arsenicosis patients. These responses are presented in more detail below. Each section outlines the steps that can be taken and, where available, the lessons learned from these mitigation measures. Most of the lessons learned are from Bangladesh, Nepal, and West Bengal (India), since these are the cases for which most information is available.

Screening and Identification of Contamination Levels in Water Sources

Background Regardless of the scale of arsenic contamination in water, there are two methods of measurement: the field test kit, and laboratory chemical analysis.2 The field test measures are more qualitative than quantitative. The choice of method for analysis depends on several criteria, including the precision of measurement required.

Choice of Screening Methodology There are two kinds of field test: those that provide a Yes or No answer and those that provide a range of concentration.3 The Yes/No field test does not provide useful information for further analysis or for the implementation of mitigation measures. The field test that does provide a range of concentration is only appropriate in certain circumstances. Box 1 outlines parameters that help to determine which test is appropriate, assuming that the laboratory test is efficient and subject to quality assurance.

Quality assurance is necessary to ensure reliability of analysis within a particular laboratory, and consistency of measurement between laboratories. Box 2 (see page 110) provides parameters to assess the capacity of a laboratory to perform analyses in order to facilitate quality assurance implementation and, ultimately, to provide accurate and usable data.

West Bengal in India is the only location where the screening of arsenic is conducted exclusively using laboratory spectrometer analysis, thereby reducing the risk of a well being misclassified as 108 109 contaminated and thereby lost as a source of water.

Other Asian countries employ a mix of field testing and laboratory testing, or field testing only. With field tests there is a higher risk of well misclassification; this risk can be reduced through, for example, retesting contaminated wells or using multiple testing. For example, in Pakistan 10% of field tests are cross-checked using laboratory analysis; while in West Bengal 3% of the samples analyzed with spectrometer are cross-checked with referenced laboratories using the atomic absorption spectrometer (AAS) (reported at Regional Workshop, Nepal, April 2004).

The only country that is planning large-scale monitoring of screened tubewells is Bangladesh, as stipulated in its National Arsenic Policy approved in March 2004. The National Arsenic Policy

2 A detailed description of field tests and laboratory analysis techniques is provided in Paper 3. 3 The Yes/No field test kits do not provide any information on the range of concentration. The only information provided is whether the concentration is higher or lower than the national standard of most Asian countries (50 µg L-1). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Box 1. Comparison of Field Testing and Laboratory Analysis

Whether to use a field test kit or laboratory analysis is not always a clear-cut decision and must take into account a range of trade-offs related to the cost of the analysis, accuracy of the analysis, time constraints, logistical requirements, and training.

Cost of analysis. In Bangladesh, for example, the reported cost of laboratory chemical analysis is approximately US$8.60 per analysis, while the price of a field test is approximately $0.50. However, in West Bengal, the price of laboratory analysis is approximately $1.60. Thus the difference in cost between the field test kit and laboratory analysis varies in significance from country to country.

Capacity of laboratories (samples/month). Given that there are approximately 11 million tubewells in Bangladesh, there are insufficient laboratories to analyze all samples. Regional laboratories in Bangladesh have a capacity of about 300 samples per month, so additional screening has to be done using the field test kit.

Time needed to process the analysis. The field test provides an immediate answer and, depending on the brand, waiting time varies from 5 to 30 minutes (Kinniburgh and Kosmus 2002). The time required to conduct the chemical analysis will depend on the availability of laboratories near the sampling point and the time needed for actual analysis. This can take months, in contrast to the immediate feedback to well owners provided by the field test kit.

Logistics. It is essential that samples are labeled properly and that the information on whether the well is safe or unsafe is communicated to the communities in a short time and in a reliable manner.

Training. Field test kits are easy to use, so related training is far easier to conduct than that needed to ensure good-quality laboratory analysis. However, the number of people to be trained is higher for field test kits than for laboratory analysis.

Opportunity for decentralization. The field test kit has considerable potential for decentralization and community involvement in the identification of safe or contaminated wells. This community involvement might be lost if only laboratory analysis is used. makes provision for monitoring of 2% of the safe (green) tubewells every six months. However, there is no specification as to whether field or laboratory testing is to be used, or regarding the procedures to ensure the reliability of water quality analyses.

Another issue to take into account in interpreting test results is seasonal variability. In Cambodia, for example, the major risk aquifer is connected to a river and arsenic levels recorded in tubewells vary seasonally, with lower levels resulting from a wet-season influx of low-arsenic river water into the aquifer (reported at Regional Workshop, Nepal, April 2004).

Choice of Scale of Screening The screening of water sources can be conducted on a large scale (national, state level) or on a more localized scale (project level). In Bangladesh, West Bengal, and Nepal screening has so far been conducted on a large scale. In other countries where arsenic has been identified, for example Cambodia, Lao PDR, Myanmar, and Pakistan, screening has been

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Box 2. Parameters to Assess the Capacity of Laboratory Analysis

The main argument for the use of laboratory analysis rather than a field test kit is the reliability of the results. However, if a given country has weak capacity for conducting chemical analysis, the value added from laboratory analysis could be negated. Therefore it is important to assess the capacity of laboratory analysis, taking into account the following:

• The current availability of the equipment to conduct analyses. • The current status of the suppliers of this equipment. • The regular availability of equipment and materials, for example distilled water. • Whether the financing of equipment and supplies is from a central institution or is done at the laboratory level. This could affect the length of time it takes for supplies to reach the laboratories; in the worst case supply shortages could interrupt work. • The current training program for laboratory staff, which should take into account available posts in laboratories and staff turnover. • Sampling and conservation of samples should follow accepted, standard procedures. • The procedures to ensure quality checks and laboratory certification have to be assessed. This process of certification does not need to be nationwide; it could be carried out among smaller units such as departments. An internal track record of these processes and all analyses performed should be kept at each laboratory. When there is a procedure of certification the level of transparency must be assessed.

conducted on a small scale in some parts of the countries. So what are the criteria that help assess whether the screening should be conducted on a national or local level?

When contamination is identified hydrogeologists and geochemists can, from the first results of screening, make certain assumptions about the potential scale of contamination based on the size and level of use of the aquifer. This will enable them to give advice on the scale of further screening (national, subnational, local) and on the design of the screening grid used to check these assumptions.

110 111 In Bangladesh the decision to adopt blanket screening was based on the heterogeneity of the aquifers, which meant that a base sample screening would not accurately represent the level of arsenic contamination of tubewells used for drinking water. In Pakistan the screening is divided into three steps: (a) a sample base screening based on a grid of 10 km x 10 km; (b) further screening using a smaller grid of 2.5 km x 2.5 km; and (c) a blanket screening of the hotspot (reported at Regional Workshop, Nepal, April 2004).

When an aquifer is discovered to be contaminated it is important to identify other vulnerable aquifers in the same area. Vulnerable aquifers are those that are naturally connected to the contaminated aquifer, or are not separated and protected from contamination by an impermeable layer. Similarly, when an aquifer is separated from the contaminated aquifer by an impermeable layer it is not naturally vulnerable unless a connection is created, for example through poor well construction. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

It is difficult to predict contamination rates when there is water flow from a contaminated to a safe aquifer. The first step is to assess the exact impact of the dilution effect, which affects the rate at which arsenic concentration will increase and therefore reach the maximum permissible level. It is difficult, however, to determine to what extent arsenic will react with the environment; it may be adsorbed, or it may interfere in biological processes. As a result of these interactions increase in arsenic concentration may be delayed, although there is currently insufficient knowledge and data to correctly model these interactions and to accurately predict this delay. Therefore only the dilution effect is usually taken into account in such models, even though this may result in an underestimation of the period of delay.

Among the factors deciding the scale of the screening is the level of priority accorded by government to the issue of arsenic contamination. The incentives that lead stakeholders, including government, to be active or inactive are addressed in chapter 4. When an agency finds arsenic contamination during the course of a project it is important to define who is responsible for screening beyond the scope of the agency's own project and for implementing the mitigation measures.

Institutional Arrangements for Arsenic Screening in Different Countries If the government decides to conduct a large-scale screening an institutional model needs to be chosen. So far in most countries two approaches have been applied. The first is to treat the screening as a public good and the second is to consider the screening the responsibility of the tubewell owners. The first model is by far the most common. In this case government, usually assisted by nongovernmental organizations (NGOs) and international agencies, conducts the screening. For example, in Bangladesh and Nepal the government is taking the lead, while in Cambodia, Vietnam, Lao PDR, and China the United Nations Children's Fund (UNICEF) is the main international agency leading the screening. The second model, where screening is demand based, has been applied in India, specifically in West Bengal. UNICEF and the state authorities of West Bengal screen all public tubewells, but private tubewell testing is the responsibility of the owner. Information on the availability of laboratories is provided and widely disseminated. So far, there is not enough information to determine whether one model is more efficient or effective than the other.

Remaining Issues and Lessons Learned Technical issues: • Regarding the choice between the field test kit and laboratory analysis, one option proposed in the literature is to use the field test kit for large-scale screening and cross-check using laboratory analysis when the capacity assessment is satisfactory. • The best way to reduce the risk of misclassification, for both the field test kit and the laboratory, is to provide adequate training to ensure precise measurements, and to maximize, when possible, the number of repetitive analyses. • Although there is a high degree of heterogeneity in arsenic concentration within a given area, correlation among neighboring wells can help identify some misclassification.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

• It is important to consider the scale of screening (large scale, project scale) in relation to other factors. • Test for possible interference of field test kit results by other constituents of the water, which may account for some of the false positives and negatives.4 • The frequency of the screening is significant where there is high seasonal variability of arsenic in tubewells, as in Cambodia. • Screening should be conducted because arsenic is flavorless and odorless; the only way to identify it is to test for it. In addition, if the measurement is wrong there is no simple way to become aware of the mistake.

Social and cultural issues: • The use of the field test kit tends to create curiosity and thus constitutes a tool for awareness raising.

Economic issues: • The monitoring of screened wells is still an issue in many countries. After the initial screening, should the priority be to screen all tubewells or only the safe ones? The rationale of retesting a contaminated well is to identify any misclassification, knowing that in some hotspots a safe tubewell could be the only source of arsenic-safe and bacteriologically safe water. Costs, however, are a significant factor, and the benefits of rescreening schemes need to be assessed. • For longer-term decision-making, universal sampling has certain benefits compared to sample-based screening. However, it is worth noting that one of the lessons learned in Bangladesh is that if a well is not tested in a contaminated area and if people do not have convenient alternative solutions, they will use this well assuming that if it has not been tested then it should be safe.

Institutional issues: • The choice of screening model (the public-good approach or demand-based screening). 112 113 • The dissemination of data, both for screening conducted by government agencies and by NGOs, is critical to ensure the transparency of information.

Summary Remarks The following guidelines are applicable when deciding on the method of testing (field test or laboratory analysis):

• If the field test kit is the method of screening then 3% to 10% of the samples should be cross-checked with laboratory analysis. • The capacity of laboratory analysis should be assessed to ensure that quality assurance is implemented.

4 False positives have an actual concentration lower than 50 µg L-1, but are falsely labeled unsafe as the field test shows a concentration higher than 50 µg L-1. False negatives have an actual concentration higher than 50 µg L-1, but are falsely labeled safe as the field test shows a concentration lower than 50 µg L-1. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

• If using large-scale screening, the first screening could use a large grid with a few samples, but with adequate regional distribution to enable hydrogeologists and geochemists to identify contaminated and vulnerable aquifers. These results would provide a first approximation of where the hotspots are situated and which zones should be prioritized to conduct a more precise screening and to implement mitigation measures. • Although not operationalized in the sample of countries that are the subject of this study, a monitoring plan is of utmost importance.

Well Switching, Painting of Tube Wells, and Awareness

Background When screening is conducted and arsenic-contaminated wells (those with levels above the accepted standard) are identified, the first step to mitigate the local population's exposure might be sharing of safe tubewells. Therefore, awareness campaigns need to make clear how to recognize safe tubewells. So far arsenic screening accompanied by the physical marking of safe or contaminated tubewells takes place in Bangladesh, Cambodia, Nepal, Pakistan, and West Bengal in India. A tubewell is considered unsafe if its concentration of arsenic is higher than the national standard.

So far, all the countries that have marked tubewells have done so in different ways. In Bangladesh, Cambodia, and Pakistan, the spouts of the contaminated tubewells are painted in red if the concentration of arsenic is higher than 50 µg L-1 (the national standard) and in green if the concentration of arsenic is lower than 50 µg L-1. In Nepal, a cross (X) is painted on the tubewell if the concentration is higher than 50 µg L-1 and a check (v) is painted if the concentration of arsenic is lower than 50 µg L-1. In West Bengal, it was decided that confusion could best be avoided by marking only the safe tubewells; those with a concentration of arsenic lower than 50 µg L-1 (the national standard) are painted in blue.

Widening Awareness of Water Quality There is a need to make sure that communities use only safe tubewells. Many countries have increasingly developed groundwater supplies because of the poor bacteriological quality of surface water, a common problem in the surveyed countries. The use of groundwater reduces the risk of waterborne disease, but has brought with it the need to explain clearly that the clean water from some tubewells contains poison that can neither be seen nor tasted.

In order to avoid confusion among communities, people should be informed that clear and clean water might be contaminated with arsenic. In Bangladesh and in West Bengal in India UNICEF has developed a well-researched information package. Other materials have also been developed by the Bangladesh Arsenic Mitigation Water Supply Project (BAMWSP) and NGOs. All materials are used widely. In Nepal the National Arsenic Steering Committee (NASC) has developed a standard information package to help clarify the sometimes contradictory messages related to bacteriological and arsenic contamination of water. However, there is still further need for the development of awareness campaigns on poor water quality.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Participants at the Regional Arsenic Workshop emphasized the need to ensure that awareness campaigns use community-specific communication methods. In Cambodia, for example, awareness campaigns use puppets, a popular form of entertainment in the country.

Remaining Issues and Lessons Learned Social and cultural issues: • It has been widely disseminated that dug wells are less arsenic-contaminated than tubewells; therefore some people think that the problem is associated with the technology being used. As a result, there is a possibility that some people may conclude that the problem is not in the groundwater quality per se but that it is associated with their tubewell and the way to fix it would be to purchase another handpump. • Since most wells are privately owned, neighbors may be reluctant to share. In addition, most tubewells are situated in the courtyard of houses so there is a privacy issue. Sharing of arsenic-safe wells as a solution can therefore not be taken for granted. • If the density of users at each well increases, some people are afraid that their tubewells will become arsenic contaminated as well. • The complaints related to sharing safe tubewells include excessive wear on equipment; new users do not clean up after themselves; and people come at late hours. In some hotspots there are simply not enough safe tubewells to meet demand for drinking water. • When people say they have no other water source, they may actually mean that they have no other tolerable source. Sharing is perceived as a reduction in the quality of life. • Women, who traditionally collect water, might not be allowed in some places to leave their immediate household unaccompanied. • In Bangladesh the choice of red to indicate arsenic contamination seems, in some cases, to be confused with iron precipitation, which leaves an orange-red color. • Awareness campaigns must explain clearly that arsenic is not a germ that can be killed by boiling water. 114 115 • In some places people are having difficulty distinguishing arsenic-related skin discoloration from other skin diseases or infections. • Color and sign interpretation of marked tubewells is a new concept for some people. • Repetition is important, because experience shows that memory and motivation fade in time. • In many countries the identification of arsenic implies an increase of collection distance and time due to the change in water source; therefore women's work load increases substantially. This also needs to be factored into the provision of arsenic-safe water. • Awareness campaigns should be carried out regularly and not only at the time of screening. • For years groundwater has been presented as the "safe" source of water; thus the arsenic- related message contradicts conventional wisdom about safe water. However, the awareness campaign related to poor surface water quality should not stop because of the more recent problem of arsenic contamination. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Technical issues: • Tubewells should be retested and repainted regularly, since painting can be altered during the rainy season.

Summary Remarks When arsenic is identified, ensure that safe tubewells are marked and that the choice of color or marks is understandable to communities. Whether unsafe tubewells should be marked or not is still an open question; the consensus seems to be that in the case of blanket screening the preferable approach is to mark the unsafe tubewells, while in the case of sample base screening it may be preferable not to mark unsafe tubewells.5

Awareness campaigns should address arsenic contamination, but also maintain awareness about poor surface water quality. There is a need to address both quality problems and not substitute awareness of the health risks due to arsenic for awareness of the risks related to poor surface water quality. In addition, the awareness campaign should use community-specific communication methods in order to reach the maximum of people in the community.

Patient Identification

Background Patient identification, also called case finding, may be passive or active. Passive patient identification is simply allowing individuals to present themselves for treatment, while active patient identification involves going out to the field to examine individuals for signs of arsenic- related disease.

In Bangladesh and Nepal patient identification is often carried out during tubewell screening. Although arsenic can cause a variety of health conditions, most patient identification has been based on skin lesion-related symptoms.

In West Bengal patient identification is mainly passive, although the Joint Plan of Action, between the state and UNICEF, has initiated an epidemiology survey. The first step is the training of doctors and NGOs to properly identify patients and to suggest appropriate mitigation measures; active identification has also been suggested.

Training of Testers in Patient Identification When patient identification is carried out alongside tubewell testing, the testers must be provided with sufficient training to distinguish between skin lesions related to arsenic ingestion and other skin lesions, bearing in mind that (a) there is still no universally agreed case definition of arsenicosis disease; and (b) the actual extent to which exposed persons will develop skin lesions and other arsenic-related conditions is difficult to predict. Therefore the capacity building of testers and health workers is critical to ensure reliable patient identification.

5 Blanket screening means that 100% of the tubewells in a given region are tested. Sample base screening means that a selection of tubewells is screened and from that data conclusions are drawn as to the levels of contamination in the other tubewells.

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Identification Based on Skin Lesions and on Laboratory Analysis Some people are subclinically affected by arsenic even though they do not show skin lesions. For example, in contaminated areas in Bangladesh, some studies have shown that children and adults without skin lesions at present may have high concentration of arsenic in their hair, nail, and urine samples. Therefore, patient identification based solely on the presence of skin lesions may underestimate actual numbers affected by arsenic.

However, identification of arsenic-affected patients using laboratory analysis of nail, blood, and hair samples is very expensive and requires strong laboratory capacity, and implementation on a large scale is not generally feasible.

Current Estimate and Projections of Number of Arsenicosis Patients The current estimates of the number of patients with arsenicosis in South and East Asian countries is summarized in table 3. A review of studies conducted in parts of the world other than Asia projects that, if the at-risk population continues to drink arsenic-contaminated water, between 16% and 21% of the population will be affected (WHO 2001a). This projection is based on the assumption that the estimation of the population at risk is accurate, the clinical case

Table 3. Current Population at Risk in Asian Countries

Region/country Present estimation Number of arsenicosis Year of first of number at risk in patients identified discovery millions (% of total so far population)

East Asia Cambodia Max. 0.3 (2.7%) - 2000 China 3 (0.2%) 522,566 1980s Lao PDR - - - 116 117 Myanmar 5 (10%) - 1999 Taiwan 0.2 - 1960s Vietnam 11 (13.7%) - 1998 South Asia Bangladesh 35 (28%) 10,000 (partial results) 1993 India (West Bengal) 5 (6.25%) 200,000 1978 Nepal 0.3 (3.4%) 8,600 1999 Pakistan - 242 cases per 2000 100,000 people based on the results of 10 districts

- Not available. Sources: Bhattacharya 2002; Ng, Wang, and Shraim 2003; Kinniburgh and Kosmus 2002; WHO 2001a; Smith, Lingas, and Rahman 2000; Berg and others 2001; information reported at Regional Workshop, Nepal, April 2004. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

recognition is accurate, and survey results of other regions can be generalized. However, the 16–21% estimate has no reliable statistical confidence intervals. For example, in Bangladesh a study conducted by the Massachusetts Institute of Technology estimated the arsenic health burden through a model of dose-response function (Yu, Harvey, and Harvey 2003). The study predicted that long-term exposure will result in approximately 1.2 million cases of hyperpigmentation, 600,000 cases of keratosis, 125,000 cases of skin cancer, and 3,000 fatalities per year from internal cancer. Another estimate of the arsenic-related health burden in Bangladesh concluded that the total risk of cancer would be equal to 375,000 affected people (Ahmed 2003). So far, these two figures are the only quantification of the potential arsenic-related health burden. They depend heavily on epidemiological assumptions and demonstrate how the lack of reliable epidemiological information adds uncertainties to the projected number of people at risk.

Lessons Learned and Remaining Issues Social issues: • Gender sensitivity: In Bangladesh, for example, each team engaged in tubewell screening and patient identification surveys includes at least two females. • Actively include information that arsenicosis is not contagious to ensure that the community will not stigmatize arsenicosis patients due to misinformation.

Economic issues: • Patient identification and medical referrals, along with public education, should be integrated into all tubewell testing efforts. This seems to be the most cost-effective way to actively identify arsenicosis sufferers. • Identification of arsenic-affected patients is generally based on the skin effects, which are not necessarily the first symptoms. However, identification based on laboratory analyses is too expensive to be implemented at large scale. • Arsenic can cause a variety of health conditions, thus there is still the issue of identification of those patients who do not develop skin lesions. The cost of the epidemiological survey required to identify all such patients would be prohibitive. However, such studies could be conducted on a small scale in order to allow estimates of the scope of the arsenic problem in a country or region within a country. • The most efficient way to conduct a nationwide survey is in conjunction with an existing population program.

Technical issues: • There is a need to ensure proper training of tubewell testers and health workers so that they can distinguish between the skin lesions resulting from arsenic exposure and other skin lesions. • Standardized criteria for diagnosing and grading skin lesions must be developed and carefully followed. The WHO is leading an effort to develop such criteria. When finalized they should be widely used by government institutions and by all organizations engaged in case finding, treatment, and surveillance.

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Summary Remarks There is a clear need to improve information about the epidemiology in arsenic-affected populations. This needs to happen in a strategic manner, and can be achieved by combining patient identification with well screening. At the same time, targeted epidemiological studies need to be carried out in order to supply data to assist arsenic mitigation activities in Asian countries.

Treatment Management of Arsenicosis Patients

Background Although a number of clinical treatments have been advocated, there is no universal medical treatment for chronic arsenicosis. The only measure that will prevent future damage is to supply the patient with drinking water that is free from arsenic and, if it is administered at an early stage, it seems to remedy past damage caused by arsenic. The first priority should be to remove people from the source of exposure and then follow up with symptomatic management. To date, there are no well-designed studies to show whether cessation of exposure leads to improvement in skin keratoses. However, anecdotal interviews of patients suggest that mild to moderate keratosis improves with cessation of exposure.

Chelation, which is often presented as a treatment of arsenicosis, has been proven effective mainly in cases of acute poisoning. The principle of chelation therapy is to provide the patient with a chemical to which arsenic binds strongly, and which is then excreted in urine. The provision of such treatment could remove large stores of arsenic (from acute exposure) from the body in a matter of hours. However, although chelation might have a positive result in some patients with chronic poisoning, so far there is no complete study that assesses its effectiveness for chronic exposure. In addition, it is difficult to ascertain to what extent improvement in skin lesions after chelation therapy is attributable to the therapy, and to what extent it is attributable to cessation of exposure. Therefore, patient improvement after chelation therapy does not provide sufficient evidence of its effectiveness (Kaufmann and 118 119 others 2001; NRC 1999).

Evidence from Taiwan suggests that some nutritional factors may reduce cancer risks associated with arsenic. It has been proposed that providing vitamins and improving diet may be of benefit to patients. In particular, vitamin A is known to be beneficial in the differentiation of various tissues, particularly the skin. If the doses given are not excessive, there are other nutritional benefits to be gained. Thus, it is recommended that all patients with skin lesions be given multivitamin tablets and that research projects be undertaken to establish whether or not they are effective for patients with arsenicosis (NRC 1999).

Arsenic is a probable contributor to causation of diabetes mellitus and hypertension. For this reason, urinary or blood glucose and blood pressure should be tested in all patients with arsenicosis and appropriate treatment and monitoring should be started if necessary (Kaufmann and others 2001). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

In Bangladesh people identified with skin lesions are given vitamins and ointment. In West Bengal (India), under the Joint Plan of Action, a network of clinics will be set up at the district, subdivision, and block level. At the same time, in both countries, studies are being conducted to provide a better estimation of the arsenic impact on human health.

Remaining Issues and Lessons Learned Social issues: • The fact that arsenicosis is not treatable with folk remedies should be emphasized in awareness campaigns (Some of the scarce literature on social issues regarding arsenic suggests that some people may spend a considerable portion of their income trying to find a homemade cure). • The fact that the only way to prevent arsenic contamination is not to drink contaminated water should be emphasized in awareness programs. • Ensure that treatment protocols are easy to follow. • Ensure that people are informed about the fact that arsenicosis is not contagious.

Technical issues: • Awareness campaigns should stress that chelation cannot be viewed as a successful treatment while exposure to arsenic-contaminated water continues. • Advanced keratoses are extremely debilitating and complications such as superimposed fungal infections may cause serious problems. Providing moisturizing lotions and treatment for infections may be beneficial and should be part of routine care in advanced cases. • Arsenic has adverse health effects other than skin lesions, such as diabetes, and these diseases have to be treated as well. • In remote rural areas clinics, equipment, and expertise are generally unavailable, so training of health workers should be conducted to help patients in the absence of effective treatment. However, in some countries health and population sector programs might not have the capacity to conduct the required nationwide training for all clinical workers within a short period of time.

Institutional issues: • Health and water supply institutions need to work together since the major treatment for arsenic is an alternative safe water source. • Doctor absenteeism might be another important factor in some countries. For example, a recent study conducted in Bangladesh estimated doctor absenteeism to be around 75% in rural areas (Chaudhury and Hammer 2003). This is a critical issue, especially if health workers do not have adequate training to help patients affected by arsenic contamination.

Summary Remarks The preferable approach is to ensure that identified patients have follow-up treatment in the local health institution. The capacity building of health workers in remote rural areas is critical and

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health and water sector professionals need to work together to make sure that people have access to information and to medicines.

Longer-Term Responses Longer-term responses are institutional and technical. The institutional aspects are mainly related to the country's arsenic policy and strategies. Technical longer-term responses can be divided into two types based on the source of water: surface water and groundwater. Surface water responses include pond sand filters, rainwater harvesting, and piped water supply. Groundwater responses include dug wells, deep tubewells, piped water supply, and arsenic removal treatment plants.

Institutional Longer-Term Responses (Arsenic Country Policy)

Background A country can respond to arsenic contamination by establishing an arsenic policy and/or strategy. The objective is to provide overall direction and guidance for dealing with arsenic and to set priorities for operational responses in the short, medium, and long terms.

So far, Bangladesh is the only country to have adopted a national arsenic policy (March 2004) and to have developed a detailed plan of action. The policy seeks to identify the nature and extent of the problem through screening and patient identification and to provide guidelines for mitigation of arsenic contamination through (a) public awareness; (b) provision of arsenic-safe water supply with a preference for surface water over groundwater, and the promotion of piped water supply when feasible; (c) diagnosis and management of patients; and (d) capacity building at all levels (from government to local communities). The arsenic policy also recommends mapping of the country's deep aquifer to ensure that deep wells will be built in regions where deep groundwater is separated from the shallow aquifers by a substantial impervious layer.

120 121 In Nepal the National Arsenic Steering Committee (NASC) is chiefly responsible for arsenic strategy. It has formulated national guidelines, which detail the steps to be taken to address arsenic contamination of groundwater and stipulate how safe and unsafe tubewells are to be marked. The NASC has also produced a standard set of information, education, and communication materials for awareness promotion within the community.

In Cambodia a recently established arsenic committee is working closely with UNICEF and a number of NGOs. The committee organizes screening of tubewells and provides different stakeholders with field test kits. In Pakistan, UNICEF is also working closely with the provinces in the screening of tubewells and other water sources.

In India, in 1999, UNICEF entered into a strategic alliance with the government of West Bengal through a Joint Plan of Action, which incorporates the following: (a) a community-based water monitoring system; (b) alternative technologies for supply of arsenic-free water (including arsenic Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

removal at the household level and piped water supply); (c) health surveillance, patient identification, and early treatment programs; (d) awareness campaigns; (e) research on arsenic health effects in women and children; (f) networking and information sharing among stakeholders; and (g) monitoring mechanisms at all levels. The Joint Plan of Action effectively constitutes a strategy to deal with arsenic contamination in the short and long term.

Summary Remarks It is important for relevant institutions to have short-term and long-term strategies for dealing with arsenic contamination. As is apparent in South Asia, no single strategy is applicable to all countries or localities. In Bangladesh and Nepal the government, in collaboration with a variety of stakeholders, is the focus of strategy, while in West Bengal the choice has been made to elaborate a plan in conjunction with an international agency, in this case UNICEF. These experiences show that (a) there is now a body of information — as evidenced in this paper — that permits the design of such policies and strategies, despite continuing uncertainty about many features of arsenic contamination; (b) more information is still needed to enable governments and other stakeholders to be more specific in defining proposed actions; and (c) policies and strategies need to be flexible enough to incorporate any further information that will become available over time. The final challenge is to ensure that such policies or strategies are enforced.

Technical Longer-Term Responses Based on Surface Water

Background Longer-term responses based on surface water include pond sand filters, rainwater harvesting, and piped water supply. Technical details for each of these operational responses are provided in Paper 3. This section focuses on the lessons learned and their implementation.

The pond sand filter technique is based on a filtration process by which water is purified by passing it through a porous medium. Slow sand filtration uses a bed of fine sand through which the water slowly percolates downward.

In Bangladesh pond sand filter technology has been used for arsenic mitigation but the level of acceptance has been low, due in part to doubts about the bacteriological quality of water. One pond sand filter can supply the daily drinking and cooking water requirements for 40 to 60 families. In the literature, Myanmar is the only other country in the study region using ponds as a mitigation option for arsenic contamination.

Rainwater is used in many parts of the world to meet demand for fresh water. The principle is to collect rainwater, either via a sheet material rooftop or a plastic sheet, and then divert it to a storage container. In the study region there have been reports of use of this technique from Bangladesh, Cambodia, and Taiwan.

Piped water supply can use surface water after simple water treatment. Generally, treatment is needed to reduce turbidity and includes chlorination to protect against bacteriological contamination of surface water. Bangladesh and India are employing the piped water option as a

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major component of their mitigation strategies, and Cambodia is also using this technique. Bangladesh is now embarking on a large pilot operation to implement piped village water supply. In India, in particular in West Bengal, this response has also been recommended on a larger scale for multiple villages. In general, the level of acceptance for the piped water supply option is high because of its convenience.

Remaining Issues and Lessons Learned Pond sand filters – social and cultural issues: • The community should pledge involvement in operation and maintenance of the pond sand filter. • Increasingly, in Bangladesh, ponds have become important sources of income because of fish culture, so farmers are reluctant to give up their ponds for pond sand filter construction. • Some users have complained about the taste of water from this source. • Pond sand water is generally contaminated with pathogens. The bacteriological quality of water fluctuates between a little over the WHO/Bangladesh standard to hundreds of times higher than that.

Pond sand filters – economic issues: • The initial capital cost of construction is high – about US$430-690, depending on the size of the pond sand filter.

Pond sand filters – technical issues: • The selected pond should not be used for fish culture, watering and washing livestock, or other domestic purposes, and should be protected from such activities. • The selected pond should be perennial. • The quality of water varies seasonally and is improved with the addition of bleaching powder solution.

Rainwater harvesting – social issues: 122 123 • Some users complain about the taste of the water. • It has been reported from Bangladesh that the return to rainwater harvesting may be viewed as a step backwards to several decades ago when it was quite widely used. • In Cambodia rainwater harvesting has been practiced for a long time and is reported to be well accepted.

Rainwater harvesting – economic issues: • In Bangladesh the cost of a rainwater harvesting system is an issue. • In addition, this solution does not cover the dry season, when another mitigation measure must be used, adding to the cost.

Rainwater harvesting – technical issues: • Rainwater harvesting is a useful alternative to other sources, but in areas with a prolonged dry season it can only be a partial solution. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

• Water quality is a concern: the first rain may flush impurities, including animal feces, off the roof. Not storing the first rain and cleaning the roof reduces the risk of inadequate water quality.

Piped water supply – social issues: • This option functions best in larger villages where density is high enough to ensure viability. • It is important to ensure that all people are connected, in particular the poorest segment of the population. • Appropriate institutional arrangements for operation and maintenance of the system should be in place.

Piped water supply – economic issues: • Affordability by different income groups within the community needs to be considered. • Operation and maintenance needs to be covered by the price of the service.

Piped water supply – technical issues: • A high level of skill is necessary for design and construction, and capacity building among local artisans is an important consideration. • A high level of skill is also needed for operation and maintenance. • Permits monitoring of one single source for water quality rather than multiple sources in one village.

Summary Remarks This section has examined some of the advantages and disadvantages of the operational responses using surface water. Taking into account such factors, certain solutions may present themselves as the best trade-off between the range of options that may be applicable in a given situation. However, care must be taken to devise solutions that address fully the goal of providing drinkable water, rather than addressing only the problems related to arsenic contamination. Table 4 (see page 124) summarizes the options.

Technical Longer-Term Responses Based on Groundwater Background The longer-term responses based on groundwater include dug wells, deep tubewells, piped water supply, and arsenic removal filters or plants. The technical details of each of these operational responses are provided in Paper 3. This section focuses on lessons learned from their implementation.

Dug wells are excavated below the water table until the incoming water exceeds the digger's bailing rate. They are typically lined with stones, bricks, tiles, or other material to prevent collapse, and are covered with a cap of wood, stone, or concrete to prevent contamination from the surface. This option has been used in Bangladesh and Nepal. The UNICEF Plan of Action proposes dug wells as a mitigation option in Myanmar.

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Table 4. Summary of Responses to Arsenic Contamination Based on Surface Water

Operational Advantages Disadvantages responses

Pond sand filter Technically easy to Poor bacteriological water quality implement Low service level

Complaints about the taste of water Selected pond sand filter should be used only for drinking water Rainwater harvesting Technically easy to Poor bacteriological water quality when not implement adequately maintained

Low service level

In some regions, cannot provide water for the entire year

Complaints about the taste of the water

Can only be a partial solution in areas with prolonged dry season Piped water supply Adequate water quality High level of skill necessary for design when treatment is carried and construction out correctly Issues of operation and maintenance and Sustainable source of management must be considered supply Other issues include affordability and system coverage

One major concern related to dug wells is that recent investigations show that some dug wells are also contaminated with arsenic (APSU 2004). Indeed, some dug wells in Bangladesh, China, 124 125 Myanmar, and Nepal have been found to have arsenic contamination.

The deep aquifers in Bangladesh, West Bengal in India, and Nepal have been found free of arsenic thus far. However, in other places, including China, deep groundwater has been found to be even more contaminated with arsenic than shallow groundwater. This means that measurement of the contamination level must be conducted before any exploitation of deep groundwater. In the case of Bangladesh, the assumption is that the pre-Holocene aquifer has been flushed and therefore all mobile arsenic has been leached from this aquifer, while in China this process might not have taken place. A more detailed explanation is presented in Paper 1.

In Pakistan the preliminary findings of UNICEF screening showed no arsenic in the deep groundwater, though the number of samples was limited (reported at Regional Workshop, Nepal, April 2004). In Cambodia the main issue related to use of the deep groundwater is the poor yield of deep tubewells, which adds significantly to the unit cost of the investment. In Cambodia the general acceptance of rainwater harvesting makes it a viable alternative to use of deep groundwater. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

In Bangladesh and Nepal mapping of groundwater is being conducted to identify at which depth arsenic-safe groundwater is located and to identify where the shallow groundwater (Holocene plain) is separated from the deep groundwater (Pleistocene terrace) by a clay layer. The existence of this clay protects deep groundwater from potential contamination by shallow groundwater. So far, there is still no wide consensus on whether groundwater mapping should be conducted through geophysical investigations or on a case-by-case basis when drilling wells. In India the Central Groundwater Board has conducted research on the deep aquifer in West Bengal. Bangladesh, Nepal, and West Bengal already use deep groundwater as a mitigation option for arsenic contamination. UNICEF proposes use of deep groundwater in its Plan of Action for Myanmar.

In Bangladesh, as in several other countries, the debate centers on the following issues: whether deep groundwater should be used or not; the risk of arsenic-contaminated water leaking from the shallow to the deep aquifer; and what assurances there are that the deep aquifer sediments will not also release arsenic into the water at some future point. One important way to handle all these uncertainties is to strengthen groundwater management, which includes a monitoring process, regulation of deep groundwater exploitation, and a process of collecting and storing data that would be helpful for further research on potential chemical contamination.

A detailed explanation of the different arsenic removal technologies is provided in Paper 3. Arsenic removal plants can be located at the household level or community level. At the household level, the arsenic removal unit could be located in the house or attached to the tubewell. This mitigation measure has been implemented in Bangladesh, Nepal, Vietnam, and West Bengal in India. UNICEF also proposes its implementation in Myanmar. However, concern has been expressed in Cambodia that the unit may be difficult to maintain at the household level (reported at Regional Workshop, Nepal, April 2004). A pilot is currently being developed in Bangladesh to investigate this concern.

Community arsenic removal plants can be useful for small villages and have been implemented in Bangladesh, India, Vietnam, and Taiwan. In general, the main issue on the technical side is how to ensure the effectiveness of arsenic removal technologies in the field, and, on the institutional side, how to ensure large-scale implementation and sustainability.

Lessons Learned and Remaining Issues Dug wells – social and cultural issues: • In a number of areas issues of taste and odor, and the possibility of bacteriological contamination, are hindering acceptance of dug well water for drinking. • Use of handpump technology can aid acceptance of the dug well but there have been complaints about the smell associated with chlorination.

Dug wells – technical issues: • Bacteriological contamination levels of dug well water are often unacceptable. • Monitoring of arsenic contamination is needed, especially during the dry season. • Use of dug well handpumps enables bacteriological quality to be improved and maintained at an acceptable level by regular chlorination.

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• Proper lining and a well-designed apron are crucial for prevention of surface water contamination. • The community should ensure that dug wells are kept in sanitary condition. • Yield is reduced when the water table drops in the dry season or if abstraction is greater than recharge.

Deep tubewells – social and cultural issues: • Due to the cost of installation, deep tubewells are usually shared by several (or many) households. This may mean that people have to walk long distances to collect safe water. • The shortage of deep wells means that people have to wait a long time to get water.

Deep tubewells – economic issues: • Initial capital cost is high, around US$700-800.

Deep tubewells – technical issues: • Since there is no clear understanding so far of the processes by which arsenic is released into water, there is still discussion as to whether deep groundwater will remain arsenic safe after medium-term or long-term exploitation.6 • There is also the need to ensure that the correct technique for drilling deep tubewells is used and that it taps the deep groundwater (not the shallow).

Deep tubewells – institutional issues: • Groundwater management must be implemented to ensure that deep tubewells are used only for drinking and cooking purposes.

Piped water supply: • Issues are the same as those for piped water supply using surface water except that treatment for bacteriological contamination is usually not necessary; however, arsenic removal treatment may be necessary.

126 127 Arsenic removal filters at the household level – social and cultural issues: • The process is time consuming, and the smell and taste are not always good. • Water becomes warm after standing for the recommended time, and cold water is preferred for drinking. • Too many water storage containers are required. • People are not in the habit of filtering their water. • The unit is not always easy to operate and maintain. • The advantage is that it allows rural households to continue using their handpumps. • There may be difficulties in obtaining the necessary chemicals.

Arsenic removal filters at the household level – economic issues: • The technology is expensive, and operation and maintenance costs may be high.

6 This is in the case of countries where deep groundwater is not contaminated, such as Bangladesh and Nepal. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Arsenic removal filters at the household level – technical issues: • The concentration of remaining arsenic in some cases remains higher than the standard. • When using alum treatment, the health risk of alum remaining in water is a concern. • Monitoring is more difficult to conduct at the household level.

Arsenic removal filters at the community level – social and cultural issues: • There is a need to organize responsibility for maintenance to ensure the sustainability of the water treatment unit.

Arsenic removal filters at the community level – technical issues: • Monitoring is easier to conduct at the community level than at the household level.

Arsenic removal filters at the community level – institutional issues: • There needs to be a routine for checking that water is arsenic safe. • If the source is surface water there should also be a process for checking its bacteriological quality. • Effective supply chains need to be developed for large-scale and sustainable solutions. Local government should be involved in ensuring effective supply chains.

Table 5. Summary of Responses to Arsenic Contamination Based on Groundwater

Operational Advantages Disadvantages responses

Dug wells Technically easy to Poor bacteriological water quality implement contamination Some dug wells might also have arsenic

Possible low level of acceptance Low service level Switch to safe Can provide potentially Difficult to predict whether the alternative aquifer good water quality, but aquifer will become contaminated needs to be monitored Potential low level of service Arsenic removal Good chance of Proven and sustainable option not yet technology sustainability at the generally available at household level community level Difficult to monitor at household level People do not always like the taste of the water

Operation and maintenance may be complicated

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Summary Remarks Table 5 summarizes the advantages and disadvantages of each of the described operational responses, enabling an assessment of the trade-off most applicable to a given situation. However, some operational responses, while addressing the problems related to arsenic contamination, may give rise to water quality problems, and therefore do not address fully the target of providing drinkable water. Such partial solutions should be avoided whenever possible.

Dissemination of Information

Regional Arsenic Networks and National Databases The development of a database provides stakeholders with access to information. Institutionally, it is useful to ensure that data are stored following a specific process and are checked and cleaned. Dissemination, accessibility, and transparency of data are critical for an issue as sensitive as water contamination. Scientifically, a database provides a baseline that can aid identification of a long-term trend. For example, the lack of a historical baseline in Bangladesh means that it cannot be ascertained whether arsenic has always been present in the groundwater or appeared only after exploitation of the aquifer.

In Bangladesh the National Arsenic Mitigation Information Center (NAMIC), a component of the BAMWSP, is responsible for collecting data related to arsenic. NAMIC collects its own data under the auspices of the BAMWSP and additional data from other stakeholders according to an agreed format. Some of the data are provided online (www.bamwsp.org). In addition, NGO-Forum provides a list of the major governmental agencies, international agencies, and NGOs that work in arsenic contamination (www.naisu.info).

In Nepal, with the support of the United States Geological Survey, the Environmental and Public Health Organization has prepared a national database for arsenic, which currently contains 128 129 18,000 arsenic level readings. Pakistan and Cambodia (annex 3) also have databases to centralize all the information from arsenic screening. In the three countries the contribution to the database is on a voluntary basis; however, in Cambodia, the Ministry of Rural Development and UNICEF make receipt of testing kits dependent upon contribution to the database. In India the Central Groundwater Board also has a web page with some arsenic-related data (www.cgwaindia.com/arsenic.htm).

Regional information can be exchanged through the Asian Arsenic Network (AAN) (www.asia-arsenic.net/index-e.htm).

The Global Positioning System (GPS) can be used to locate tubewells on a database, though differentiating individual wells may be difficult where the density of tubewells is greater than the resolution of the GPS, as may occur in Cambodia and Bangladesh (reported at Regional Workshop, Nepal, April 2004). Whatever method is used to differentiate wells in such Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

circumstances should be practical enough to be used by all stakeholders, allowing levels of arsenic in individual wells to be monitored over time.

Summary Remarks Once established, a database should be sustainable. In some cases a database is developed within a project and the collection of data is dependent on project financing. The institutional process to ensure the sustainability of data is usually not given priority at this time. However, during such projects the technical process of data collection, including where to measure and at what frequency, should be developed in parallel with the institutional process to make sure that cost recovery of the data collection takes place after project closure. This raises the issue of whether or not access to data should be free of charge; and, in the event of a charge, whether usage would be sufficient to ensure cost recovery.

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3. Arsenic Mitigation in the Context of the Overall Water Supply Sector

Background ost South and East Asian countries where groundwater arsenic contamination has been Midentified have inadequate surface water quality, mainly due to microbial contamination. In these countries solutions to water supply problems may require a trade-off between the long- term health effects of a contaminant such as arsenic and the short-term health effects of microbial contamination.

Access to Improved Water Sources in Asian Countries Until recently, most sectoral programs concentrated on the lack of access to improved water supply. Table 6 shows the increase in access to improved water sources in South and East Asian countries during the 1990s. However, other problems, such as inadequate sanitation, are still present in the region (table 7) and, despite improvements, child mortality remains high (table 8).

Table 6. Access to Improved Water Sources in Selected Asian Countries

Population with access to improved water source (%) 1990 2000 Country Urban Rural Total Urban Rural Total population population

Bangladesh 99 93 94 99 97 97 Cambodia - - - 54 26 30 China - - 71 - - 75 India886168957984 Lao PDR - - - 61 29 37 130 131 Nepal 93 64 67 94 87 88 Pakistan 96 77 83 95 87 90 Vietnam 86 48 55 95 72 77

- Not available. Sources: World Bank 2003a: www.wsp.org/07_eastasia.asp; www.wsp.org/07_southasia.asp.

Arsenic Priority Compared to Bacteriological Water Quality Priority Available data indicate that the rate of mortality due to waterborne diseases is greater than that resulting from arsenic contamination. Based on information in the literature, the best estimate of mortality due to diarrhea in Bangladesh is 120,000–200,000 people per year, of which possibly half can be attributed to drinking of pathogen-contaminated water (Alaerts and Khouri 2004). Similarly, the best estimates put mortality due to arsenicosis at 20,000–40,000 people per year. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 7. Percentage of Population in Selected Asian Countries with Sanitation

Population with access to sanitation (%) 1990 2000 Country Urban Rural Total Urban Rural Total population population

Bangladesh 81 31 41 71 41 48 Cambodia - - - 56 10 17 China - - 29 - - 38 India 44 6 16 61 15 28 Lao PDR - - - 67 19 30 Nepal - - 20 - - 28 Pakistan 52 23 36 82 38 62 Vietnam - - 29 - - 47

- Not available. Sources: World Bank 2003a: www.wsp.org/07_eastasia.asp; www.wsp.org/07_southasia.asp.

Table 8. Child Mortality Rates in Selected South and East Asian Countries

Infant mortality rate (per 1,000) Under-five mortality rate (per 1,000) Country 1980 2001 1980 2001

Bangladesh 129 51 205 77 Cambodia 110 97 190 138 China 42 31 64 39 India 113 67 173 93 Lao PDR 135 87 200 100 Nepal 133 66 195 91 Pakistan 105 84 157 109 Thailand 45 24 58 28 Vietnam 50 30 70 38

Source: World Bank 2003a.

However, it is not known whether arsenic morbidity is higher than waterborne disease morbidity. Thus, there are insufficient data to resolve the issue of how to prioritize between short-term contamination of surface water and long-term contamination by arsenic.

As regards contamination with arsenic, certain criteria can help assess the level of priority that should be given to the problem: (a) the concentration of arsenic in drinking and cooking

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water; (b) the spatial distribution of the contaminated tubewells; and (c) the proximity of other water sources that are safe.

There is a positive correlation between the concentration of arsenic and its health effects. If the only available sources have high arsenic concentrations (more than a few hundred µg L-1) and most of the tubewells are contaminated, there is practically no access to safe water. In this case the morbidity of arsenic is very high, and the shift to surface water might be considered, providing adequate chlorination is carried out or that people are advised to boil water for drinking purposes. If the average concentration of arsenic is less than 100 µg L-1, there is a longer timeframe for planning action. Solutions such as either providing surface water safe from arsenic and bacteria, or piped water either from surface water or another aquifer, can be properly planned to ensure that people get access to safe water. Another scenario could be that some tubewells have high concentrations of arsenic but the percentage of contaminated wells is low, which means that people will still have access to safe water within a reasonable walking distance. This kind of case-by-case or village-by-village analysis can provide insight into suitable steps to be taken.

The financial sustainability of any water supply technology is necessary to ensure long-term sustainability of the supply, and must include operation and maintenance of the system, be it wells, pond sand filters, or piped water supply. Such recurrent costs and responsibilities for incurring them will vary according to such factors as whether the water supply is private (for example individually installed household wells) or operated by the community.

In the shift to arsenic-safe options governments will have to involve communities in cost sharing, both for capital costs and for long-term operation and maintenance. With water supply provision still free in a number of countries, this relatively new concept may not be widely accepted by government or by users. Indeed, moving from surface water to groundwater allowed people to have clean clear water almost free of charge in terms of operation and maintenance costs. Now that some tubewells can no longer be used, alternative safe sources of water may have high 132 133 operation and maintenance costs. Users would have to pay for water on a regular basis and receive a quality of service equal to or less than that available with tubewells. Therefore, as applicable in a given country, willingness to pay studies will be crucial in deciding what mitigation options are not only technologically appropriate but also socially accepted in the long run. Such studies have been carried out by the Water and Sanitation Program in, for example, Bangladesh (WSP 2003) and have played an important role in informing policy decisions regarding the introduction of piped water supply.

Definition and Identification of Arsenic Contamination Hotspots Color coding of tubewells has been used to signify which wells are arsenic safe and which are not (see section above). There is no record in the literature of more than two colors being used to Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

identify degrees of contamination; for example, one color could indicate an arsenic concentration less than 10 µg L-1, another could indicate the range 10–50 µg L-1, another the range 50–200 µg L-1, and another a concentration higher that 200 µg L-1. Such levels of precision would be possible in countries where laboratory testing was the norm, but not in countries that rely on field test kits. Also, use of additional colors would add complexity to any awareness campaign. However, an advantage would be that users could tell which of the contaminated tubewells were less harmful and which more harmful. A long-term advantage could be that if the national standard in some countries was lowered to, for example, the present recommended maximum permissible value of the WHO (10 µg L-1) tubewells would not have to be rescreened and reclassified, and sufficient data would be available to enable costing of the measures associated with adjustment of the national standard.

The problem of prioritizing mitigation measures for arsenic contamination is illustrated by Bangladesh, where emergency villages are defined as those with more than 80% of tubewells contaminated. However, this does not always provide a full enough picture on which to base operational responses; for example, 80% of tubewells contaminated with, say, 60 µg L-1 may be less harmful than 70% of wells contaminated at an arsenic level of 200 µg L-1. Therefore, when definition of hotspots is based only on the percentage of tubewells with a concentration of arsenic higher than WHO guidelines or national standards, there is insufficient information to develop a plan of action.

Remaining Issues and Recommendations Institutional setting of water quality monitoring is a concern. Which institution should be responsible for the first screening and the monitoring? Should the operator or an independent organization such as an NGO or the community conduct them? What about sustainability and transparency and access to the related data?

Since some countries such as Bangladesh, Nepal, and India also have the option of using deep groundwater, the legal aspects of groundwater management will have to be taken into account. Especially where exploitation of deep groundwater is concerned, should permits be introduced to ensure that the deep groundwater will be used exclusively for drinking and cooking purposes or is it assumed that, because of the cost, people will not use the deep groundwater for irrigation purposes? Hence, for long-term planning, there is a need to develop and strengthen the legal framework for groundwater management.

Although arsenic contamination is covered far more in the international media than waterborne diseases, this should not imply that the bacteriological quality problem faced by South and East Asian countries should be put aside. The decision regarding the setting of priorities has to be taken based on criteria such as the level of contamination of arsenic, and the access to safe water based on bacteriological and chemical parameters.

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4. Incentives for Different Stakeholders to Address Arsenic Contamination

he major stakeholders in natural arsenic contamination are water users, government, NGOs, Tdonors, and international agencies. The incentives for each stakeholder to be active in addressing the issue are different. While a government would be expected to be more influenced by public pressure, for example in the run-up to elections, an international agency might be more concerned with the reputational risk associated with its choices. The incentives for an NGO may stem less from public pressure or reputational risk (although this could also be possible) than from the wish to influence decisions in a given sector. When no other stakeholder is addressing the issue, there is an incentive for the users themselves to act to remedy the situation. Incentives discussed here are the number of people at risk, number of arsenicosis patients, rural and urban areas affected, national and international media coverage, cross-sector responses needed, water service pricing, short-term versus long-term solutions, reputational risk, and transparency of the mitigation measures.

Number of People at Risk The number of people at risk from arsenic contamination does not seem in itself to be an incentive for stakeholders to become active. Those at risk are those drinking contaminated water; only a certain proportion will develop the clinical symptoms of arsenic poisoning. Ahmed (2003) estimated the percentage of the total population at risk to be about 25% in Bangladesh, 6% in West Bengal (India), and 2.4% in Nepal. Fewer data are available for East Asian countries than for South Asian countries, perhaps due to lack of identification of the problem, though in Vietnam the percentage of the population at risk has been estimated at 13%, or 11 million people (Berg and others 2001). Lack of information, however, prevents an accurate current assessment of arsenic contamination in East Asian countries.

Number of Arsenicosis Patients 134 135 The number of actual arsenicosis patients might be considered more of an incentive for stakeholders to become active. For example, while the estimate of the percentage of population at risk in Vietnam is double that of West Bengal, the number of (identified) arsenicosis patients is reported to be nil in Vietnam compared to around 200,000 in West Bengal (WSP 2003). There is no indication from the literature that Vietnam is in the process of providing mitigation measures on a large scale for the at-risk population. It is important to note that the use of groundwater in Vietnam is quite recent (less than 10 years). Since the latency of arsenic-related diseases is between 10 and 15 years, Vietnam could register a large number of arsenicosis sufferers in a few years – which would increase the incentive to address the issue, but unfortunately at already a very advanced stage. Hence, the first identification of arsenicosis patients is a greater incentive for government, donors, NGOs, and international agencies to act than the population-at-risk measurement. This is not surprising, given the many other issues that developing countries have to contend with, but investments in patient screening and epidemiology now could prevent costly emergency mitigation interventions later. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Rural and Urban Areas Except in the cases of Vietnam and Cambodia, arsenic-contaminated groundwater has mainly been detected in rural areas. In urban areas it is easier to deal with the arsenic problem when there is a point source water supply. For example, in Hanoi water treatment plants use aeration and sand filtration for iron and manganese removal from the pumped groundwater, which also eliminates some arsenic from the raw groundwater, although in some cases this is not enough to reduce it to levels below the national standard. In such circumstances, established facilities can be upgraded to address the arsenic problem. On the other hand, in rural areas, the problem is far more complicated because water sources are dispersed and difficult to improve on an emergency basis. Provision of mitigation measures by government and donors may take a long time, though NGOs might be more flexible and better suited to act quickly at this decentralized level. Even so, the scale of the problem is significant.

Importantly, rural populations often have less political clout than urban populations, which are typically more informed and politicized. Rural populations also suffer from the organizational problems that tends to afflict large groups with many free riders, weakening their voice as a group. This may in turn weaken the incentive for politicians to address arsenic contamination in rural areas.

National and International Media National media coverage can be an incentive for stakeholder activity since there is reputational risk associated with providing unsafe water. However, this type of media coverage may act as a disincentive to action; if it is alarmist or factually inaccurate then certain stakeholders may prefer to avoid possible controversy.

International media coverage might also create an incentive by raising global awareness, encouraging international agencies to orient their projects to take into account arsenic issues, and governments to commit more money to this purpose. However, care must be taken that this shift will not cause governments to reallocate resources from other equally important but less publicized problems.

For the media themselves, there is an incentive to cover such controversial issues as arsenic contamination because they increase circulation. However, the short-term coverage is often in contrast to the long-term, chronic nature of the problem.

Institutional Aspects Arsenic is a cross-sectoral issue in that it involves water supply, water resources management, health, and (rural) development institutions. This can create difficulties if the institutions do not coordinate with one another. Transparency in the choice of mitigation measures can be an incentive encouraging stakeholders to be active and to work together.

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The pricing of water supply services provides users with an incentive to hold providers accountable for water quality. This is not always an incentive for government to implement charges for water supply services since they then become accountable. Tubewells in rural areas provide clean water that is almost free in terms of operation and maintenance costs. However, most of the solutions to address arsenic contamination will be less convenient and some mitigation measures will involve a charge for water supply service, which can be a difficult reform to introduce in some countries.

Short-Term versus Long-Term Solutions Government, international agencies, and NGOs might feel greater incentive to implement short- term solutions rather than long-term solutions that are less immediately rewarding. The development of arsenic policies and strategies can be a means of increasing the likelihood that long-term solutions will be implemented as well.

Reputational Risk Reputational risk can act as an incentive to make government and international agencies active. However, as in Bangladesh, the controversy surrounding arsenic contamination may discourage certain stakeholders from risking their reputations by becoming involved in the issue. This has delayed decision-making on such mitigation measures as the use of arsenic-free deep groundwater, which could provide safe water in the short and medium term.

Table 9 provides a conceptual summary of the political economy of arsenic contamination of groundwater. It provides an indication why — up to now — mainly donors and international agencies and some country governments have been responding to arsenic contamination. Clearly, as more arsenic-affected areas are being identified and as the number of arsenicosis patients is going to rise, it can be expected that stakeholders will become more active. It is, 136 137 however, important that in the meantime a more rational basis for dealing with arsenic contamination is created in order to avoid delayed — or exaggerated — responses. An important aspect in this regard is investment in epidemiological studies and economic analyses, as outlined in Paper 4. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 9. Conceptualized Incentive Matrix: Stakeholder Incentives for Action on Arsenic Issues

Incentive factors Government Donors/international NGOs agencies

Number of people at risk Number of arsenicosis patients Rural areas Urban areas National media coverage International media coverage Water pricing and accountability Transparency in choice of mitigation measures Availability of short-term solutions Availability of long-term solutions Perception of reputational risk

Low incentive Medium incentive Great incentive

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5. Conclusions

n certain areas, natural arsenic contamination of groundwater has made effective access to Isafe drinking water difficult to achieve. If the concentration in water of a chemical parameter, such as arsenic, is higher than the maximum permissible national drinking water standards, the water is considered contaminated and no longer potable. In Bangladesh, for example, arsenic contamination has reduced the amount of safe drinking water by about 20% in the last decade.

Two main issues generate substantial uncertainties in accurately predicting the impact of specific short-term or long-term mitigation measures. The first is the lack of understanding of how arsenic is released from sediment to water, and the second is the lack of epidemiological data on the health impact of low concentrations of arsenic in drinking water. Indeed, since the arsenic release process is not fully understood, it becomes difficult to be certain that a given mitigation measure will always provide arsenic-safe water. Also, since the epidemiology of arsenic is not fully understood, estimation of the real health outcome for lower arsenic concentrations provided by a given mitigation measure is difficult. For example, regarding the exploitation of the deep (Pleistocene) aquifer, so far no arsenic has been found in deep tubewell water in Nepal, West Bengal, or Bangladesh. However, due to these uncertainties, whether deep groundwater will remain arsenic safe in the long term, and what the real health outcome of using deep groundwater compared to other mitigation measures will be, are difficult to determine.

Practically speaking, mitigation measures should be implemented as soon as arsenic has been identified. While the success of implementation depends mainly on socioeconomic factors such as people's acceptance of an option and its capital cost, scientific understanding of arsenic has value added on the quantification of impacts, but not on the implementation of mitigation measures per se. Therefore, instead of delaying implementation until arsenic contamination is fully understood, both implementation and scientific investigation should be conducted in parallel.

At the policy level (that is, action the government needs to take), when arsenic contamination is 138 139 identified in groundwater there is a need to assess:

• The scale of contamination: As the first screening results become available hydrogeologists and geochemists should recommend whether the screening needs to be implemented at the project level or if national screening needs to be conducted. • The emergency level based on the population at risk, the number of arsenicosis patients, the time of exposure, and the concentration of arsenic in water.

Based on the contamination scale and the emergency level, government should implement a regional emergency plan of action with short-term and long-term components to mitigate arsenic contamination. Potential emergency and short-term responses include dug wells, pond sand filters, rainwater harvesting, arsenic removal filters at the household level, and use of a safe aquifer. Potential long-term operational responses are arsenic removal plants at the community level, piped water supply, and use of a safe aquifer. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

At the implementation level (that is, action that needs to be taken at the project level), when arsenic is identified, there is a need to conduct the following actions:

• Ensure that the appropriate government institution is informed about the contamination. • Ensure that the data are available and properly stored for further scientific research on the contamination, and are also available to different stakeholders that either use the water or implement water projects in or beyond the project area. • Ensure that in the project area the government requires the operator to check arsenic on a regular basis and makes the results available to stakeholders.

Whether the project should be continued is a decision for both the institution or international agency and the government. There is a need to ensure that arsenic mitigation occurs in an integrated manner with ongoing projects.

One of the questions for donors and international agencies is whether a water project where arsenic is identified should be pursued or not. Knowing that arsenic has long-term health effects and that poor surface water quality has short-term effects, the question is how to address both issues in a balanced way. If the project is to continue, government should provide assurances that appropriate measures will be taken to mitigate the arsenic contamination.

Finally, arsenic contamination has changed people's minds about the generally accepted rule that "groundwater equals safe drinking water". Although such water may be bacteriologically safe recent events have cast increasing doubts on its chemical safety. There are still other sources of water contamination in South and East Asian countries that need to be addressed, such as fluoride, manganese, sodium, iron, and uranium, in addition to bacteriological contamination. A development agency's target should be to ensure that all the mechanisms for water quality monitoring are set and implemented now, either for surface water or groundwater, to reduce the risk of providing unsafe drinking water.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response Pakistan ✔ d South Asia c ✔ ✔ The Joint Program of Action (JPOA) with UNICEF. d. angladesh India Nepal Incipient. c. b ✔✔✔✔✔ ✔✔ ✔ Vietnam B (China) Only for piped water supply. Only for piped water supply. b. ✔✔✔✔✔ ✔✔✔✔✔

140 141 Lao PDR Myanmar Taiwan ✔✔✔✔✔ a b ✔✔ ✔✔ ✔✔✔ ✔ ✔✔✔✔ ✔ ✔✔✔ ✔✔✔✔✔ ✔✔✔✔✔✔✔ ✔✔✔✔✔ ✔ ✔ indicates Household water Arsenic committees/ programs Screening (field test) Screening (laboratory) Water sharing Dug well Rainwater harvesting Pond sand filter Deep tubewell treatment treatment program Database Arsenic policy Community water Arsenic monitoring ✔ ( presence of activity)Assessment of the arsenic situation Cambodia China Activities Asia East Mitigation activities Dealing with arsenic at the national or state policy level Long-term collection and dissemination of information The water treatment is based on blend of safe and potentially contaminated water. The water treatment is based on blend of safe and potentially contaminated water. a. Annex 1. Operational Responses Undertaken by South and East Asian Countries Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Contd. on next page following the mitigation requirements made available after the closure of project conducted responses onitored for contaminants Recommendations Expected outcomes retained and sustained Sampling strategy — whether to screen all tubewells or just a small percentage — must be decided by the responsible agency Issues Screening methodselection (field test If field tests are chosen, then a percentage of samples shouldversus laboratory be cross-checked with laboratory analysis. If analysis) standard operating procedures to Establish analysis is chosen, ensure capacity sufficient and acapacity Technical for measuring Adequate training must be provided and refresher courses ensure reliability and consistency of arsenic arsenic quality assurance mechanism is implemented data concentration people should be required, otherwise technical assistance needs tofor a first Train screening, but ensure that they will be available for monitoring be chemical parameters m Ensuring thatmitigation measures of the minimum quality requiredandspecify delineate acceptable Each mitigation measure must include clear specifications are Ensure a functional process is in place to verify contractors Increased sustainability of mitigation used equipment of quality enhanced through measures concentrations capacity is courses to ensure training-for-trainer Provide materials and quality standards to be used Assessing extentarsenicof Determination of whether to screen a large or local areacontamination inthe shortest timepossible using a large grid to acquire critical information on the location of the hotspots where precise screening should should be left to a hydrogeologist. Conduct first screening Information on the extent of arsenic development the in critical is contamination an and plan action pragmatic a of operational appropriate of assessment Ensuring that be wateralternative presentsources safe levels of and maintenance of different operational responses (dug Ensure the community is properly trained in operationotherand bacteria rainwater harvesting, water treatment, well, pond sand filter, Ensure alternative potable water sources are also regularly a preventing by quality water Improve water)safe pollutant piped shift to the water quality problem, say from arsenic to bacteria or some chemical other Table 1. Technical Issues 1. Technical Table Annex 2. Matrices for Implementation of Operational Responses to Arsenic Contamination

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response Expected outcomes to drink contaminated water tubewell safety information listing which tubewells are safe or unsafe

142 143 by planning treatment for other diseases, such as diabetes Issues Recommendations stakeholders Ensuring thatalternative water – Avoids a water shortage that forces people Providing patientsadequatewith Provide arsenicosis patients with vitamins, moisturizingtreatment lotions, and treatment for infectionsreduce least, at or, effect arsenic Reverse Maximize patient contact with a preventive health approachdiseases arsenic-related from people's suffering and the morbidity rate sources have the capacity to meet demand Marking tubewellsregularly Retest tubewells once or twice a yearto access easy have people that sure Make Cross-checkingdata collected among different For example, NAMIC data in Bangladesh have been cross- checked with data collected by Columbia University Preserves reliability of collected data in a way cost-effective Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Expected outcomes the poor segment of population screening and monitoring is not identified dentification identification Issuesbenefits and costs Recommendations Assessing pricingaffordability for Conduct a willingness to pay study determine the rangethe poor affordcan people fees water of and operation of recovery cost Ensures campaigns coststhe Reducing associated with testing should be done in concert with patient Tubewell screening and maintenance costs with minimal burden on patient identification i Finding mechanisms Allows for cost-effective patient a public-private fund to compensate those most Create compensateto losemay that people use their pond for fishing purposes, people who experience ofbecause income impacted by economic loss, for example people who cannotmitigation measures Sustainability a lack of privacy because they share safe tubewells of these emergency or short- term solutions Choosing amitigation optionbased on the options Assess both expected benefits and costs of mitigation Create basis for rational decision-making on Deciding whichstakeholder(s) should pay for the –theand screening monitoring of tubewells, patient identification, and awareness mitigation options and programs If a progressive financial mechanism for from the beginning, when donors leave collection of data is likely to stop Table 2. Financial and Economic Issues Table

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response Expected outcomes

144 145 ork with the community to create a feasibleork with the community to create the goodwill of the (same) few people who sting always the same villages and families within have who people of coverage the Increases unity plan that maps out which family should go to willingly offered their help charge or with clear steps on how the data can be purchased.Provide, at minimum, the following information: the extent of arsenic contamination (a) geographical distribution of affected areas; (b) location of arsenic-contaminated tubewells; and (c ) number of affected persons or identified patients with potable drinking water and turbid surface asunsafe to drink There will always be some uncertainties and therefore many contaminants are not always visible Avoids confusing people on the origin and Issues Recommendations public is consistent Publicly state assumption made, if applicable Coordinatingoperational actionsamong stakeholders affected area by different stakeholders, but instead try to cover the largest geographical areas te Avoid Finding incentives to Limit the number of people who have to share sameincrease people'swater safe to access tubewell. W share safe wells Spreads the social burden and avoids taxing Making sure that for issues at the time of gender-related creating Avoid patient identification examination by including a male and female examiner in Avoids underestimating the number of issues gender sensitive Addresses Dissemination ofdata Create a website where data might either be available free of of Transparency the information related to willingness withincommunities to comm other the Paradigm shifting"clearfrom away it clear through public announcements that while Make safeequals water water" surface water is unsafe, some clear groundwater can also be contaminated. Indeed for many years people in Asian water monitored Increasing people's willingness to have their Coordination between scientistsand donors countries have immediately associated clear groundwaterto possible answers. However: (a) scientific community andensure informationtheto disseminated (b) qualify statements by clearly explaining what facts are scientists must agree on one (simple) story to tell the public; known with certainty and what information is still debatable. Increasing public awareness that water potential extent of the arsenic contamination problem Table 3. Social and Cultural Issues Table Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Expected outcomes Issuesthere are women oneach team each team (case study: Bangladesh)Creating legible Recommendations and understoodmarks on mark culturally sensitive a design or color-coded Create locatedtubewells to people in the rural areain rural Place design or mark in an easily recognized and visible communities awareness the of effectiveness Enhances Ensuring healthandworkers thetake female doctors arsenicosis patients Promoting the use of vitamins is not sufficient as a location near the tubewell explainto time preventive arsenicosis contraction; the only option that exists preventive or treatment measure at early stages ofmeasures that Stress is to stop drinking arsenic-contaminated water. Maintaining publicadvanced- people: to home message aboutawareness Drives Ensure continued production of messages to the public that there is no cure for advanced-stage arsenicosis arsenic and other explain surface water is unsafe and contaminatedwater-related Avoids a simple problem shift of the risk stage arsenicosis is not treatable diseases associated campaign by easily reaching a wide audience with poor microbiological quality of surface water and bacteria to arsenic from sources, such as dug well, ponds, etc.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response Expected outcomes preventing finger pointing of responsibility on important social issues

146 147 economically based incentive, such as higher Improver the health sector service in remote ose projects where institutions of both sectors are the Improves institutional efficiency by avoiding ween the sectors and institutions for general announcements, workshops, meetings, etc. Increases institutional accountability by Ensuring poorbewill people equally served Provide a subsidy to ensure that poor communities canin the provision of afford cost of serviceseach to water for price fair a Applies segment of the population Issues Recommendations mitigation measures Coordinating Prop areasrural remote aImplementing training free of charge to health workers policydecentralized generate a multiplier effectstrategy implies a Create multilevel and multidiscipline training sessions tolarge number of trainers and trainees in people of number maximum the Reaches way cost-effective a activities betweenactivities healthand water agencies implementing theirand sectors, corresponding Develop workshops coving topics relevant to both sectors institutions Create a transparent information dissemination system bet interinstitutional conflicts of interest wasteful spending on similar action items forum to address potential Creates Identifyingincentives tostrengthen the weak ofsector health an Create wages or increased promotion probability Develop alternative solutions, such as providing additional areas rural Table 4. Institutional Issues Table Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Expected outcomes cooking purposes only Increases the sustainability of groundwater usage stablish an archive systemarchive an stablish Increases information availability for further and licensesand groundwater uses, such as for drinking and Ensure data are properly cleaned and stored research or other general purposes groundwater database management IssuesEffectivelyintroducing legislation, Recommendations especially in the Introduce water rights and well exploitation permitscase when an alternate aquifer is safe to use Identifying the Creates incentive for reasonable or reduced responsibleforstakeholder(s) Ensure that each stakeholder has a clear understandingthe screening and monitoring of water of their responsibilityquality Providing external Clearly defines which institution is elements such as –chain supplies for water treatment Introducing E accountable if the screening or monitoring is not conducted Ensures the sustainability of chosen option

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Annex 3. Operational Responses to Arsenic Contamination: Questionnaire Results

Country Four countries responded to the survey: Bangladesh, Cambodia, Nepal, and Pakistan State/Province (if applicable) Country national standard for arsenic 50 µg L-1 for all respondent countries (µg L-1 or ppb) Answer provided by: BRAC, AusAID, FAO, UNICEF, Partners for (Name/institution/address/email) Development, Irrigation Ministry of Nepal

The questionnaire was in two parts. The first part focused on general issues regarding the operational responses towards arsenic contamination, and the second focused on implementation aspects of these operational responses. The tables below indicate the questions in the left column, and summarize country responses in the right column.

Part 1. General Issues Survey

Water resources availability and use in the country

Questions Results How much groundwater and surface water In Bangladesh, Nepal, and Pakistan groundwater is respectively is used countrywide for drinking used first and foremost for irrigation (by a large water supply, irrigation and industry? margin), then for drinking water supply, and finally for industrial purposes. What is the percentage of groundwater and Not enough answers to provide any regionwide surface water used in the rural and in the urban conclusion. areas respectively for drinking water, industry and irrigation? a) When and by what institution/person was the Except for Bangladesh, where the first screening first discovery of arsenic in groundwater made? was conducted in 1993, the first screenings in 148 149 b) What are the areas, so far, identified and what Cambodia, Nepal, and Pakistan were conducted percentage of the country consists of these between 1999 and 2000. contaminated areas? Distribution of contaminated areas within the four countries was as follows: in Bangladesh, contamination occurred in the deltaic areas; in Cambodia, in the areas close to the Mekong River; in Nepal, in the southern Terai plain; in Pakistan, in the provinces of Punjab and Sind. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Regulatory framework

Is there a specific national policy, law (or Bangladesh is ahead of the other countries with protocols) regarding arsenic? If not, why not? respect to its national arsenic policy. If yes, which institution is responsible to implement these? (Please provide a summary/ copy of the policy/law/protocol/decree.) Is there a groundwater law in the country? So far there is no groundwater law in the four When was it instituted? If not, is one under countries. However, Nepal is in the process of development (law already initiated, law under reviewing a draft groundwater law, and in Pakistan development, or no law)? UNICEF and the Ministry of Environment are planning to initiate one during 2004. Is there a surface water or general water law Cambodia, Pakistan, and Nepal each have a surface in the country? When was it instituted? If not, water law. In Nepal the surface water law was is it under development (law already initiated, instituted in 1992. law under development, or no law)? Is there a national database on arsenic All four countries have a database. contamination? If not, why? Is contribution to the database enforced by It is voluntary in Bangladesh, Nepal, and Pakistan, law or is it voluntary? and mandatory in Cambodia as the contribution to the database is a condition for receiving a testing kit from UNICEF and MRD.

Mitigation measures

When was the first regionwide screening All four countries mark tubewells in the screening conducted? And when was the first nationwide process. In Bangladesh, Cambodia, and Pakistan the screening conducted? marking is based on colors, specifically green and Was a systematic marking of the contaminated/ red. In Nepal, markings take the form of either a safe tubewells/other sources done? How was cross or a check (√). the marking done? If no screening conducted either regionwide or nationwide, why? Which arsenic-related activities are being Patient care has not been implemented so far in undertaken in your country? Nepal or Pakistan. To your knowledge, which governmental UNICEF is involved in the four countries, in institution/NGO/development partner is particular in Cambodia and Pakistan. In Bangladesh carrying out these activities? the number of stakeholders is much higher than in other countries. The major NGOs in Cambodia are RDI and PDF.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Mitigation measures

Are the different actors coordinating these Regarding the coordinating agencies: there was no activities? If yes, by whom and how is it done? consensus in Bangladesh; in Cambodia, UNICEF is Is the coordination effective? Why? If not, seen as taking this role; and in Nepal the National why not? Steering Committee for Arsenic is the coordinating agency. Pakistan has not yet begun a nationwide coordination effort. How many tubewells/other water supply The only country for which the number of tubewells sources are there in the country? is reported is Bangladesh, with about 10 million How many tubewells/other sources are there tubewells. The number of tubewells is not reported in the arsenic-affected areas? in Cambodia, Nepal, or Pakistan. How many tubewells/other sources have been screened? Will all the tubewells/other sources be screened in the long term? If not, why not? What is the tone of the national media coverage The tone of the national coverage of arsenic regarding arsenic contamination? contamination has been reported as: alarmist in Bangladesh and Nepal; fact based in Pakistan; and nonexistent in Cambodia. How would you rate, on a scale from 1 to 3, The arsenic problem is rated as very important in the arsenic problem compared with other Bangladesh and Pakistan; and of medium problems faced by your country? importance in Cambodia and Nepal. Which institution/NGO/international UNICEF is seen as the main driver in addressing organization is the main driver in addressing arsenic issues in both Cambodia and Pakistan; in the arsenic issue? How did this institution come Nepal it is the Department of Water Supply and to take the lead? Sewerage; and in Bangladesh several agencies have been reported as being the main drivers: DPHE, DANIDA, UNICEF, and the World Bank. When exploring a new source of water, are there Bangladesh and Cambodia have a standard standard protocols about the chemical protocol for drinking water supply. 150 151 parameters to check water quality for drinking None of the four countries seems to have a water supply, or irrigation? standard protocol for irrigation. Is arsenic one of the parameters of these Although arsenic is a parameter of the protocol in protocols? Bangladesh and Cambodia and should be a factor If yes, is arsenic occurrence a factor in the in the decision as to whether to use the water decision about the choice of using the water source, it does not seem to be implemented. source? And if it is detected, what are the actions conducted regarding this contamination? Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Part 2. Specific Implementation of Mitigation Measures

Implementation aspects of mitigation measures

Is there any monitoring for the screened In all four countries limited or no monitoring is tubewells/other water supply sources? reported. If yes what frequency and how is it done? If not, why? What method is used for the screening? Field test kits are used for screening in all four (e.g. field test kit, laboratory or both). Is cross- countries. Cross-checking with laboratories is checking of field test and laboratory analysis reported in all countries. applied? If yes, how is it done? What are the main problems encountered in the Ensuring the effectiveness of the field test. process of screening, both on the technical and Limited capacity of government staff. on the institutional side? The transport of samples from the field to laboratory. Describe the present awareness campaign TV, radio, and distribution of printed material are the (TV, radio, newspaper, etc.) What are the lessons media used for the awareness campaign. learned on the best way to communicate Lessons learned: information about arsenic? Use community-specific communication methods, e.g. karaoke (when applicable), video. Verbal communication with the community is one of the most effective means of communication. Mitigation should accompany awareness campaigns as providing an alarmist message without providing a solution is counterproductive. What mitigation measures are already applied Screening is the mitigation measure that has been and tested (e.g. dug well/surface water/rainwater conducted in the four countries. So far, all the harvesting/water treatment/deep groundwater/ mitigation options have been tested in Bangladesh. others)? In Cambodia dug wells, rainwater harvesting, community water treatment, and ceramic filters for surface water treatment have been implemented. In Nepal water treatment at the household level has been tested on an experimental basis. In Pakistan dug wells are used and household-level treatment is being promoted. How are mitigation measures (dug well/surface In Bangladesh and Cambodia all the implemented water/rainwater harvesting/water treatment/ mitigation options are selected at the community deep groundwater/others) selected level. In Nepal screening is selected by the central (e.g. feasibility study, community decision, agency and donors, while household water central agency)? treatment is only selected by donors. In Pakistan the implementation of mitigation options is based on feasibility studies. What are the major problems encountered in It is difficult to operate the pond sand filter. implementation of the mitigation measures and It is difficult to make people change behavior and what has functioned well? switch from tubewells to other water sources. The capital cost of the initial infrastructure for alternative water supply is a problem.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Health aspects of the mitigation measures

a) Which agencies are responsible for patient In Bangladesh many agencies are responsible for identification? arsenic identification, namely: Dhaka Community b) Do they coordinate their work? Hospital, upazila health complex at upazila level, c) If yes how is it done? If the coordination is and the Ministry of Health and Family Welfare. In not effective what are the reasons? Cambodia and Nepal it is the Ministry of Health. In d) Is the screening based on skin lesions or are Pakistan patient identification has not started yet. there measurements (arsenic in hair, nail, In Bangladesh the reported information is that and blood)? there is no coordination among the agencies, while in Cambodia it seems to be coordinated. In Cambodia the coordination is through the Arsenic Interministerial Subcommittee and via UNICEF/ WHO assistance. The screening is mainly based on skin lesions in Bangladesh, Cambodia, and Nepal. In Pakistan measurement is also based on arsenic in the nail. How is medical management of arsenicosis In Bangladesh it is organized mainly through patients organized? government hospitals, DCH, and UNICEF. In What is the procedure for monitoring patients? addition, through the financial assistance of BAMWSP, DCH trained doctors in the identification and management of arsenicosis patients. None of the countries reported any procedure for monitoring patients. What is the current estimate of the number of For Bangladesh the range is from 13,000 to more patients with arsenicosis? What is the current than 19,000 arsenicosis patients. In Pakistan, there estimate of the population at risk? are approximately 140 arsenicosis cases per 100,000 people in Punjab. It is reported that no patients have been identified as yet in Cambodia.

Research aspects of arsenic contamination

152 153 Is there any research done in your country/state/ There seems to be a lot of research in both province on the origin of the arsenic in the Bangladesh and Cambodia involving both local sediment, its release to the groundwater, and and foreign research institutions. Small-scale the migration with the groundwater flow? research in Nepal has been reported with involvement of the USGS. No research has been reported in Pakistan. If yes, what institutions are involved: local universities, local research institutes, government agencies, foreign universities, foreign research institutes, NGOs, etc.? Is there any outcome of research on arsenic While Bangladesh is the only country where research accumulation in the food chain? on arsenic accumulation has been reported, no conclusions as yet are available. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Research aspects of arsenic contamination

Is there national quality control of laboratories? Nepal is the only country where there is national If yes, how is it conducted (frequency, control of laboratories. methodology, responsible institution, etc.)? In Nepal, the Department of Meteorology and Standards accredits the private laboratories; however, this is not mandatory and is done on a voluntary basis.

Economic aspects of the mitigation measures

What is the cost of each mitigation measure? Bangladesh is the only country where most of the How many people were served? costs are available. These costs are summarized in the table at the end of this annex. In the case of Pakistan the following lump sum was provided: (Pitcher + awareness raising + testing & marking)/HH = Rs 1,500. In general, in your opinion, what are the main lessons learned on the operational responses that have been conducted?

Social It is possible to train female village volunteers to test the tubewells for arsenic. Local women with limited educational background can also be trained on preliminary identification of arsenicosis patients, awareness education, alternative water supply, and monitoring of these options. Community needs to be mobilized in arsenic mitigation. There is no unique solution because of technical limitations and cultural acceptance of mitigation options. Communication of arsenic issues to private individuals installing tubewells is a challenge.

Technical Local mason can be trained in the construction and manufacture of different mitigation options. Monitoring of safe water options for arsenic and bacteria (when applied, e.g. for surface water) as well as for other potential contaminants. Since there is so far no treatment for arsenicosis, there is a need to provide arsenic patients with safe water for drinking and cooking purposes. Much research is needed to find out effective treatment regimens for patients in different stages of arsenicosis. Many treatment units, either home based or community based, produce sludge that contains a high concentration of arsenic. A countrywide proper management system for this sludge should be set up so that rural people can manage this sludge in a convenient way.

Economic Need low-cost solutions. Need for fee collection to cover ongoing maintenance issues.

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Institutional Set a priority to implement mitigation options in the most-affected villages. There should be more coordination among different governmental and nongovernmental agencies working in the country. The longer-term solutions must be based on a long-term vision. This may include the provision of piped water supply to its population and the optimum use of its surface water. The potential role that the local governments can play in this longer vision must be fully explored; towards this, experimentation and pilot projects should not wait. Standardized field testing and data management are needed. Government needs to be in the driver's seat in screening and implementing mitigation options.

Bangladesh: Costs of Mitigation Measures (Response to Questionnaire Item 32)

Cost per unit (taka) Number of people served

Screening with field test Tk 30 (total cost Tk 3,000) 100 households Screening with laboratory Tk 500 by AAS analysis Tk 300 by spectrometer Awareness campaign Tk 1,500 per village meeting 100 households Dug well New: Tk 40,000–50,000 40–50 households (Renovation: Tk 10,000 average) Tk 35,000–40,000 20–30 families comprising 5 members Pond sand filter Tk 50,000–60,000 50–70 households Tk 30,000–40,000 20–30 families comprising 5 members Rainwater harvesting Tk 10,000–12,000 (3,200 liters) 1 household Tk 8,000 (3,200 liters) 1 family comprising 5 members 154 155 Deep groundwater Tk 40,000 average 50–60 households Tk 35,000–40,000 20–30 families comprising 5 members Household treatment Depends on the water treatment Community treatment Depends on the water treatment Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries onal/ arvard/MIT NGO-Forum BUET-ITN NAMIC country network/ database Contd. on next page APSU arsenic ICEF (DFID) (BAMWSP) ater Country Regi CDDR H International oval treatment ICEF WVB ameen I valuating W BRAC DANID DANIDA BRAC technologies policy arsenic DPHE WHO UN International JICA Rotary DANIDA CIDA SIDA ACIC tubewell of rem ameen AAN Bank IDE Project NGO-Forum NGO-Forum WB ameen Bank WaterAid OCETA Proshika International International sand water well filter supply CDDR ICDDR WaterAid CARE BankInternational WVB Rotary UN DANIDA Gr DPHE DPHE WB DPHE UNIICEF harvesting Rainwater Pond Piped Dug Deep E anagement OHFW CDDR SDC AAN Gr een Bank PSOM SIDA OHFW UNICEF UNICEF DANIDA DANIDA International NGO-Forum DGHS DCH SIDA SDC SDC JICA West Bengal West state NRCS ng/ identification M shika DCH OHFW (BAMWSP) WB (BAMWSP) WB UNDP Rotary DANIDA International awareness BRACWBDANIDA UNICEFSDC BRAC JICAAANIDE DGHSGrameenBank SDC UNICEFVERC AAN Bank NI Grameen BRACWaterAidUNDP IDE I Pro BRACRotary SIDA SDC DOEHInternational JICA SIDA WVB WaterAid AAN AAN Grameen VERC Bank SDC CARE Rotary UNDP WaterAid IDE DOEH BRAC Rotary WVB AAN Rotary SDC Gr Rotary WVB VERC Gram UNICEFNIPSOMNGO-Forum NGO-Forum WB M JICASIDA WB AUSAID SIDA WHO WHO DANIDA JICA JICA SDC UNICEF I UNICEF UNICEF WB DFID AAN AAN BUET M DFIDExpertComitéGOW Bengal West UNICEF state DFID Expert Bengal West Comité GOW state UNICEF Bengal West Bengal West state Bengal West state state DPHE DPHE DPHE M UNICEFUSGSDWSSNRCSJRCS FINNIDA DWSS/ UNICEF RWSSSP/ DIDC India CIDA UNICEF CIDA UNICEF UNICEF UNICEF UNICEF (field test)Bangladesh switchi Screening Screening Well Patient Patient Nepal WHO Annex 4. Government, NGOs, International Organizations Involved in Operational Responses

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response arsenic network/ database country arsenic ater Country Regional/ Hanoi RDI PFD UNICEF WB UNICEF/MRD oval treatment valuating W CEETIA CECEAWAG UNICEF- tubewell of rem Central government supply technologies policy sand water well filter nwater Pond Piped Dug Deep E t harvesting anagemen

156 157 ng/ identification M awareness UNICEF MRD RDI NEWAH WBPFD ADRA UNICEF Save The Children Fund (UK) SDC HUS HUCE UNICEF PFD ENPHO RWSSSP/ DIDC (field test) switchi Myanmar WRUD Screening Screening Well Patient PatientPakistanCambodia UNICEF Rai WHOChinaLao PDR UNICEF UNICEF Taiwan Vietnam EAWAG RDI Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Contd. on next page Nonreversible Reversible Reversible within short time after exposure ceases – – ) -1 ); Reversibility of effects -1 -1 -1 -1 -1 -1 -1 -1 /180 µg L /120 µg L /72 µg L -1 -1 -1 -1 -1 -1 -1 -1 120/480 µg L 1,000 µg L 600 µg L 200/800 µg L -1 -1 -1 -1 -1 -1 -1 -1 –1 -1 -1 -1 200 µg L 1,500 µg L 3 L day Quantity of water drunk in 1 day (L arsenic concentration in drinking water (µg L 600–1,000 µg L 5 L day 360–600 µg L 5 L day 5 L day 200–2,000 µg L 5 L day 120–1,200 µg L 900–1,500 µg L 3 L day 3 L day a -1 day -1 03–0.05 day L 2 01/0.04 day L 2 Exposure dose 0.050.01–0.1/0.06 day L 2 day L 2 mg kg ved 300/1, , rhinorrhea, and gn of gastrointestinal 0. examination often reveals that symptoms such as sore 0. ptoms and gangrene Cardiovascular arteries, arterioles,and capillarthe concentration – – – throat Cerebrovascular disease –analysis of blood sometimes shows –elevated levels of hepatic enzymesday L 3 – irritation are obser the liver is swollen and tender L µg 300–3,000 Health effects Sym effectsVascular Blackfoot disease: progressive loss –effectsHematological 2002) (ATSDR – Anemia and leukopenia Hepatic effects Clinical (ATSDR 2002; (ATSDR InVS 2002;Engel and Smith 1994; of circulation in the hands and feet Chiou and others 1997) leading ultimately to necrosis Gastrointestinal effectssi Clinical Respiratory effects Minor (ATSDR 2002)(ATSDR sputum cough, 2002; InVS 2002) (ATSDR 2002) (ATSDR Annex 5. Health Effects of Chronic Exposure to Arsenic in Drinking Water

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response Nonreversible Nonreversible Nonreversible - ) -1 ); Reversibility of effects -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1,500 µg L 5 L day 480 µg L 5 L day 120 µg L 5 L day 600 µg L Quantity of water drunk in 1 day (L arsenic concentration in drinking water (µg L a years 1,200 µg L -1 day years 300 µg L -1 0.04 day L 2 2–3 weeks 0.05 day L 2 0.01 day L 2 Exposure dose mg kg

158 159 relatively less n.a. n.a. n.a. was prominent feature of ptoms abetes – – Nonreversible kin changes that include hyperpigmentation interspersed with small areas of hypopigmentationday L 3 organ systems on the face, neck, and backSkin changes that include hyperpigmentation interspersed with small areas of hypopigmentationon the face, neck, and backSkin changes that includeL µg 800 on the face, neck, and back –day L 3 arsenic poisoning among 220 cases associated with an episode of arsenicL µg 200 contamination of soy sauce in JapanL µg <100 day L 3 L µg 1,000 sensitive to arsenic than most other generalized hyperkeratosis and 15 to 5 generalized hyperkeratosis and hyperpigmentation interspersed with small areas of hypopigmentation generalized hyperkeratosis and 3 to months 6 (noncancer S (ATSDR 2002) (ATSDR Dermal effects InVS 2002) 2002)(ATSDR eyelids, Endocrinal effects Di Ocular effects Facial edema, generally involving the Renal effects 2002) (ATSDR The kidney is effects) (ATSDR 2002; (ATSDR effects) Health effects Sym Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries Contd. on next page Nonreversible – – Some recovery may occur following cessation of exposure, but this is a slow process and recovery is usually incomplete – ) -1 ); Reversibility of effects -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 3 L day 4,000 µg L 5 L day 2,400 µg L 1,200 µg L 5 L day 720 µg L 360–1,200 µg L 900–3,000 µg L 5 L day Quantity of water drunk in 1 day (L arsenic concentration in drinking water (µg L a -1 day -1 months 1,800 µg L 0.06 day L 2 0.005 day L 2 Exposure dose mg kg zziness, for 1 week 3 L day on 600–2,000 µg L -1 ogical examination of nerves ptoms Symmetrical peripheral neuropathy. 0.03-0.1day L 2 Periorbital swelling was reported in 0.2water at an approximate dose of 0.2 mg kg Corneal ulceration from arsenickeratosis day L 2 –losing 40 pounds (18 kg) – Fatigue, headache, di numbness of the extremities people drinking contaminated well 1 weekL µg 6,000 from affected individuals reveals a dying-back axonopathy withdemelinati insomnia, nightmare, andday L 3 L µg 150 (ATSDR 2002)(ATSDR exposure reported for one person 4 Immunological andlymphoreticular effects 2002) (ATSDR No study available on this issueNeurological effects – – – Body weight effects loss: dose and time Weight (ATSDR 2002)(ATSDR Histol Health effects Sym

Paper 2 An Overview of Current Operational Responses to the Arsenic Issue in South and East Asia Volume II Technical Report Towards a More Effective Operational Response ncer however, they may develop however, be fatal if untreated and in Chile Long latency, an increase in mortality continued for 40 years after the highest exposure began ) -1 ); Reversibility of effects -1 -1 locations Both types of skin ca wan: 500wan: can be removed surgically; -1 -1 -1 -1 -1 for 10–20 years (Smith, Lingas, -1 Quantity of water drunk in 1 day (L arsenic concentration in drinking water (µg L that induced skin cancer: in Tai 5 L day 60 µg L and Rahman 2000) may that lesions painful into for 10–20 years (Smith, Lingas, and Rahman 2000);in Cordoba: 178 µg L cancer internal to due a r anr Observed exposure in different -1 day -1 Exposure dose mg kg exposure of less

160 161 udy available on this issue – – – ptoms kin cancer: multiple squamousfo cases Some cell carcinoma as well multiple basal cell carcinoma than 1 yearL µg reported 100 µg L Internal cancer: bladder, kidney,Internal cancer: bladder, lung, liver, and prostate Observed exposure in different locations that induced internal cancer: in Chile: 500 µg L were among the symptomsday L 3 ) -1 ) ) -1 -1 day -1 BW C x DI

Health effects Sym Reproductive effects 200) (ATSDR st No Genooxic effects 2002) (ATSDR 2002)Cancer (ATSDR Chromosomal effects S – – – Development effects Spontaneous abortion – – – Exposure dose: ED = Where: ED = exposure dose (mg kg BW = body weight (kg) DI = daily intake of water (L day - Not available. n.a. Not applicable. a. C = exposure concentration (mg L Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

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This paper was prepared by Professor eroze Ahmed (Bangladesh University of Engineering and Technology) with contributions from Khawaja Minnatullah (World Bank/WSP) and Amal Talbi (World Bank). VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Summary

1. This paper presents the technologies for treatment of arsenic-contaminated water, arsenic detection and measurement technologies, and alternative safe water options. After a brief introduction (chapter 1), chapter 2 examines the principles of arsenic removal from drinking water and explores the major technologies associated with each. Chapter 3 describes the laboratory and field methods of arsenic detection and measurement. Chapter 4 presents alternative options for arsenic-safe water supplies. Chapter 5 analyzes some operational issues related to the mitigation options presented in the paper.

2. The objective of the paper is to provide technical staff in governments, development organizations, nongovernmental organizations and other interested stakeholders with up-to-date information on the technical aspects of arsenic mitigation in order to familiarize them with the most commonly used mitigation methods. For treatment of arsenic-contaminated water, there are four basic processes: (a) oxidation-sedimentation; (b) coagulation-sedimentation-filtration; (c) sorptive filtration; and (d) membrane techniques. For alternative water supply options, there are four main options: (a) use of an alternative safe aquifer, accessed by a deep tubewell or dug well; (b) use of surface water employing, for example, a pond sand filter or multistage filters; (c) use of rainwater; and (d) piped water supply based on either ground or surface water.

3. The paper is designed as a tool to inform the decision-making process when deciding which arsenic mitigation option is best suited to a particular project. It lays out the advantages and disadvantages of each mitigation method, and the related operational issues.

166 167

Paper 3 Arsenic Mitigation Technologies in South and East Asia VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

1. Introduction

rsenic is present in the environment and humans all over the world are exposed to small A amounts, mostly through food, water, and air. But the presence of high levels of arsenic in groundwater, the main source of drinking water in many countries around the world, has drawn the attention of the scientific community. Groundwater, free from pathogenic microorganisms and available in adequate quantity via tubewells sunk in shallow aquifers in the flood plains, provides low-cost drinking water to scattered rural populations. Unfortunately, millions are exposed to high levels of inorganic arsenic through drinking this water. It has become a major public health problem in many countries in South and East Asia and a great burden on water supply authorities. Treatment of arsenic contamination of water, in contrast to that of many other impurities, is difficult, particularly for rural households supplied with scattered handpump tubewells. In developing countries like Bangladesh and India the high prevalence of contamination, the isolation and poverty of the rural population, and the high cost and complexity of arsenic removal systems have imposed a programmatic and policy challenge on an unprecedented scale.

Source substitution is often considered more feasible than arsenic removal. The use of alternative sources requires a major technological shift in water supply. Treatment of arsenic-contaminated water for the removal of arsenic to an acceptable level is one of the options for safe water supply. Since the detection of arsenic in groundwater, a lot of effort has been mobilized for treatment of arsenic-contaminated water to make it safe for drinking. During the last few years many arsenic detection and test methods and small-scale arsenic removal technologies have been developed, field-tested, and used under different programs in developing countries. This short review of these technologies is intended as an update of the technological developments in arsenic testing, arsenic removal, and alternative water supplies. It is hoped that the review will be of assistance to those involved in arsenic mitigation in South and East Asian countries.

168 169 Volume II Technical Report Towards a More Effective Operational Response

2. Treatment of Arsenic-Contaminated Water

rsenic in groundwater is present mainly in nonionic trivalent (As(III)) and ionic pentavalent A(As(V)) inorganic forms in different proportions depending on the environmental conditions of the aquifer. The solubility of arsenic in water is usually controlled by redox conditions, pH, biological activity, and adsorption reactions. The reducing condition at low Eh value converts arsenic into a more mobile As(III) form, whereas at high Eh value As(V) is the major arsenic species. As(III) is more toxic than As(V) and difficult to remove from water by most techniques.

There are several methods available for removal of arsenic from water in large conventional treatment plants. The most commonly used processes of arsenic removal from water have been described by Cheng and others (1994), Hering and others (1996), Hering and others (1997), Kartinen and Martin (1995), Shen (1973), and Joshi and Chaudhuri (1996). A detailed review of arsenic removal technologies has been presented by Sorg and Logsdon (1978). Jekel (1994) has documented several advances in arsenic removal technologies. In view of the lowering of the standard of the United States Environmental Protection Agency (EPA) for the maximum permissible levels of arsenic in drinking water, a review of arsenic removal technologies was carried out to consider the economic factors involved in implementing more stringent drinking water standards for arsenic (Chen and others 1999). Many of the arsenic removal technologies have been discussed in details in the AWWA (American Water Works Association) reference book (Pontius 1990). A review of low-cost well water treatment technologies for arsenic removal, with a list of companies and organizations involved in arsenic removal technologies, has been compiled by Murcott (2000). Comprehensive reviews of arsenic removal processes have been documented by Ahmed, Ali, and Adeel (2001), Johnston, Heijnen, and Wurzel (2000), and Ahmed (2003). The AWWA conducted a comprehensive study on arsenic treatability options and evaluation of residuals management issues (AWWA 1999).

The basic principles of arsenic removal from water are based on conventional techniques of oxidation, coprecipitation and adsorption on coagulated flocs, adsorption onto sorptive media, ion exchange, and membrane filtration. Oxidation of As(III) to As(V) is needed for effective removal of arsenic from groundwater by most treatment methods. The most common arsenic removal 170 171 technologies can be grouped into the following four categories:

• Oxidation and sedimentation • Coagulation and filtration • Sorptive filtration • Membrane filtration

The principal mechanisms and technologies for arsenic removal using the above technological options are described in detail in the following sections.

Oxidation-Sedimentation Processes

Most treatment methods are effective in removing arsenic in pentavalent form and hence include an oxidation step as pretreatment to convert arsenite to arsenate. Arsenite can be oxidized by Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

oxygen, ozone, free chlorine, hypochlorite, permanganate, hydrogen peroxide, and Fulton’s reagent, but atmospheric oxygen, hypochloride, and permanganate are commonly used for oxidation in developing countries. The oxidation processes convert predominantly noncharged arsenite to charged arsenate, which can be easily removed from water.

Atmospheric oxygen is the most readily available oxidizing agent and many treatment presses prefer oxidation by air. But air oxidation of arsenic is a very slow process and it can take weeks for oxidation to occur (Pierce and Moore 1982). Air oxidation of arsenite can be catalyzed by bacteria, strong acidic or alkali solutions, copper, powdered activated carbon, and high temperature (Edwards 1994). Chemicals such as chlorine and permanganate can rapidly oxidize arsenite to arsenate under a wide range of conditions. Hypochloride is readily available in rural areas but the potency (available chlorine) of the hypochloride decreases when it is poorly stored. Potassium permanganate is also readily available in developing countries. It is more stable than bleaching powder and has a long shelf life. Ozone and hydrogen peroxide are very effective oxidants but their use in developing countries is limited. Filtration of water through a bed containing solid manganese oxides can rapidly oxidize arsenic without releasing excessive manganese into the filtered water.

In situ oxidation of arsenic and iron in the aquifer has been tried in Bangladesh under the Arsenic Mitigation Pilot Project of the Department of Public Health Engineering (DPHE) and the Danish Agency for International Development (Danida). The aerated tubewell water is stored in feed water tanks and released back into the aquifers through the tubewell by opening a valve in a pipe connecting the water tank to the tubewell pipe under the pump head. The dissolved oxygen in water oxidizes arsenite to less-mobile arsenate and the ferrous iron in the aquifer to ferric iron, resulting in a reduction of the arsenic content in tubewell water. Experimental results show that arsenic in the tubewell water following in situ oxidation is reduced to about half due to underground precipitation and adsorption on ferric iron. The method is chemical free and simple and is likely to be accepted by the people but the method is unable to reduce arsenic content to an acceptable level when arsenic content in groundwater is high.

Chlorine and potassium permanganate are used for oxidation of As(III) to As(V) in many treatment processes in Bangladesh and India. SORAS (solar oxidation and removal of arsenic) is a simple method of solar oxidation of arsenic in transparent bottles to reduce arsenic content of drinking water (Wegelin and others 2000). Ultraviolet radiation can catalyze the process of oxidation of arsenite in the presence of other oxidants such as oxygen (Young 1996). Experiments in Bangladesh show that the process on average can reduce the arsenic content of water to about one-third of the original concentration.

As a process, passive sedimentation has received considerable attention because of rural people’s habit of drinking stored water from pitchers. Oxidation of water during collection and subsequent storage in houses may cause a reduction in arsenic concentration in stored water. Experiments conducted in Bangladesh showed zero to high reductions in arsenic from drinking water by passive sedimentation. Arsenic reduction by plain sedimentation appears to be

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

dependent on water quality and in particular the presence of alkalinity and precipitating iron in water. Passive sedimentation, in most cases, failed to reduce arsenic to the desired level of 50 µg L-1 in a rapid assessment of technologies conducted in Bangladesh (BAMWSP-DFID- WaterAid 2001).

Coagulation-Sedimentation-Filtration Processes In the process of coagulation and flocculation, arsenic is removed from solution through three mechanisms:

• Precipitation: The formation of insoluble compounds • Coprecipitation: The incorporation of soluble arsenic species into a growing metal hydroxide phase • Adsorption: The electrostatic binding of soluble arsenic to external surfaces of the insoluble metal hydroxide (Edwards 1994)

Precipitation, coprecipitation, and adsorption by coagulation with metal salts and lime followed by filtration is a well-documented method of arsenic removal from water. This method can effectively remove arsenic and many other suspended and dissolved solids from water, including iron, manganese, phosphate, fluoride, and microorganisms, reducing turbidity, color, and odor and resulting in a significant improvement in water quality. Thus removal of arsenic from water using this method is associated with other ancillary health and aesthetic benefits.

Water treatment with coagulants such as aluminium alum (Al2(SO4)3.18H2O), ferric chloride (FeCl3),

and ferric sulfate (Fe2(SO4)3.7H2O) is effective in removing arsenic from water. Oxidation of As(III) to As(V) is required as a pretreatment for efficient removal. It has been suggested that preformed hydroxides of iron and aluminium remove arsenic through adsorption, while in situ formation leads to coprecipitation as well (Edwards 1994). In alum coagulation the removal is most effective 172 173 in the pH range 7.2–7.5, and in iron coagulation efficient removal is achieved in a wider pH range, usually between 6.0 and 8.5 (Ahmed and Rahaman 2000). The effects of cations and anions are very important in arsenic removal by coagulation. Anions compete with arsenic for sorptive sites and lower the removal rates. Manning and Goldberg (1996) indicated the theoretical affinity at neutral pH for anion sorption on metal oxides as:

PO4 > SeO3 > AsO4 > AsO3 >> SiO4 > SO2 > F > B(OH)3

The presence of more than one anion can have a synergistic effect on arsenic removal. Addition of either silicate or phosphate has some effects on arsenic removal but presence of both can reduce arsenate removal by 39% and arsenite removal by 69% (Meng, Bang, and Korfiatis 2000). Based on arsenic removal studies in Bangladesh, Meng and Korfiatis (2001) concluded that elevated levels of phosphate and silicate in Bangladesh well water dramatically decreased adsorption of arsenic by ferric hydroxides. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The technologies developed based on the coagulation-sedimentation-filtration process include:

• Bucket treatment unit • Stevens Institute technology • Fill and draw treatment unit • Tubewell-attached arsenic treatment unit • Iron-arsenic treatment unit

The bucket treatment unit, developed by the DPHE-Danida Project and improved by the Bangladesh University of Engineering and Technology (BUET), is based on coagulation, coprecipitation, and adsorption processes. It consists of two buckets, each with a capacity of 20 liters, placed one above the other. Chemicals are mixed manually with arsenic-contaminated water in the upper red bucket by vigorous stirring with a wooden stick and then flocculated by gentle stirring for about 90 seconds. The mixed water is allowed to settle and then flow into the lower green bucket and water is collected through a sand filter installed in the lower bucket. The modified bucket treatment unit shown in figure 1 has been found to be very effective in removing iron, manganese, phosphate, and silica along with arsenic.

The Stevens Institute technology also uses two buckets, one to mix chemicals (iron coagulant and hypochloride) supplied in packets and the other to separate flocs using the processes of sedimentation and filtration (figure 2 see page 174). The second bucket has an inner bucket with slits on the sides to help sedimentation and keep the filter sand bed in place. The chemicals form visible large flocs when mixed (by stirring with a stick). Clean water is collected through a plastic pipe fitted with an outlet covered with a cloth filter to prevent the entry of sand. The efficiency of the system has been described by Meng and Korfitis (2001).

Figure 1. Double Bucket Household Arsenic Treatment Unit (Ali and Others, 2001)

Top bucket

Flexible plastic pipe

Bottom Cloth screen bucket

Sand filter PVC slotted screen

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Figure 2. Stevens Institute Technology (Drawn by Ahmed, 2003)

Transfer of chemical Chemicals mixed water

Mixing stick Main bucket Interior bucket Slits Outlet with cloth filter Filter sand Plastic pipe to deliver treated water

The fill and draw system is a community-level treatment unit designed and installed under the DPHE-Danida Project. It has a 600 liter capacity (effective) tank with a slightly tapered bottom for collection and withdrawal of settled sludge (figure 3). The tank is fitted with a manually operated mixer with flat blade impellers. The tank is filled with arsenic-contaminated water and the required quantity of oxidant and coagulant are added to the water. The water is then mixed for 30 seconds by rotating the mixing device at the rate of 60 revolutions per minute (rpm) and left overnight for sedimentation. The settled water is then drawn through a pipe fitted at a level a few inches above the bottom of the tank and passed through a sand bed, and is finally collected through a tap for drinking. The mixing and flocculation processes in this unit are better controlled to effect higher removal of arsenic. The experimental units installed by the DPHE-Danida project are serving clusters of families and educational institutions.

The tubewell-attached arsenic removal unit was designed and installed by the All India Institute of Hygiene and Public Health (AIIH&PH) (figure 4). The principles of arsenic removal by alum

174 175 Figure 3. DPHE-Danida Fill and Draw Arsenic Removal Unit (Drawn by Ahmed, 2003)

Gear System

Cover

Impeller Handle

Tank Filtration unit

Treated water Sludge withdrawal pipe Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

coagulation, sedimentation, and filtration have been employed in this compact unit for water treatment at the village level in West Bengal, India. The arsenic removal plant, attached to a handpump-operated tubewell, has been found effective in removing 90% of the arsenic from tubewell water. The treatment process involves the addition of sodium hypochloride (Cl2) and aluminium alum in diluted form, mixing, flocculation, sedimentation, and upflow filtration in a compact unit.

Figure 4. Tubewell-Attached Arsenic Removal Unit designed by All India Institute of Hygiene and Public Health (Ahmed and Rahman, 2000)

A B

C D

A - Mixing; B - Flocculation; C - Sedimentation; D - Filtration (upflow)

Iron-arsenic removal plants use naturally occurring iron, which precipitates on oxidation and removes arsenic by adsorption. Several models of iron-arsenic removal plants have been designed and installed in Bangladesh. A study suggests that As(III) is oxidized to As(V) in the plants, facilitating arsenic removal (Dahi and Liang, 1998). The iron-arsenic removal relationship with good correlation in some operating iron-arsenic removal plants has been plotted in figure 5. Results shows that most iron removal plants can lower arsenic content of tubewell water to half to one-fifth of the original concentration. The main problem is to keep the community system operational through regular washing of the filter bed.

Figure 5. Correlation between Iron and Arsenic Removal in Treatment Plants (Dhai and Liang, 1998)

100

90 y = 0.8718x + 0.4547

80 R2 = 0.6911 , % 70

60

50

40 Arsenic Removal

30

20 20 30 40 50 60 70 80 90 100 Iron Removal, %

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Some medium-scale iron-arsenic removal plants with capacities of 2,000–3,000 m3 day-1 have been constructed for water supplies in district towns in Bangladesh. The main treatment processes involve aeration, sedimentation, and rapid sand filtration with provision for addition of chemicals if required. The units operating on natural iron content of water have efficiencies varying between 40% and 80%. These plants are working well except that the water requirement for washing the filter beds is very high. Operations of small and medium-sized iron-arsenic removal plants in Bangladesh suggest that arsenic removal by coprecipitation and adsorption on natural iron flocs has good potential for arsenic content up to about 100 µg L-1.

Water treatment by the addition of quick lime (CaO) or hydrated lime (Ca(OH)2) also removes arsenic. Lime treatment is a process similar to coagulation with metal salts. The precipitated

calcium hydroxide (Ca(OH)2) acts as a sorbing flocculent for arsenic. Excess lime will not dissolve but remains as a thickener and coagulant aid that has to be removed along with precipitates through sedimentation and filtration processes. It has generally been observed that arsenic removal by lime is relatively low, usually between 40% and 70%. The highest removal is achieved at pH 10.6 to 11.4. McNeill and Edward (1997) studied arsenic removal by softening and found that the main mechanism of arsenic removal was sorption of arsenic onto magnesium hydroxide solids that form during softening. Trace levels of phosphate were found to slightly reduce arsenic removal below pH 12 while arsenic removal efficiency at lower pH can be increased by the addition of a small amount of iron. The disadvantage of arsenic removal by lime is that it requires large lime doses, in the order of 800–1,200 mg L-1, and consequently a large volume of sludge is produced. Water treated by lime would require secondary treatment in order to adjust pH to an acceptable level. Lime softening may be used as a pretreatment to be followed by alum or iron coagulation.

Sorptive Filtration Several sorptive media have been reported to remove arsenic from water. These are activated alumina, activated carbon, iron- and manganese-coated sand, kaolinite clay, hydrated ferric 176 177 oxide, activated bauxite, titanium oxide, cerium oxide, silicium oxide, and many natural and synthetic media. The efficiency of sorptive media depends on the use of an oxidizing agent as an aid to sorption of arsenic. Saturation of media by different contaminants and components of water takes place at different stages of the operation, depending on the specific sorption affinity of the medium to the given component. Saturation means that the sorptive sites of the medium have been exhausted and the medium is no longer able to remove the impurities. The most commonly used media for arsenic removal in small treatment plants include:

• Activated alumina • Granulated ferric oxide and hydroxide • Metallic iron • Iron-coated sand or brick dust • Cerium oxide • Ion exchange media Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Arsenic removal by activated alumina is controlled by the pH and arsenic content of water. Arsenic removal is optimum in the narrow pH range from 5.5 to 6.0 when the surface is positively charged. The efficiency drops as the point of zero charge is approached and at pH 8.2, where the surface is negatively charged, the removal capacities are only 2–5% of the capacity at optimal pH (Clifford 1999). The number of bed volumes that can be treated at optimum pH before breakthrough is dependent on the influent arsenic concentration. The bed volume can be estimated using the following equation, where As is the initial arsenic concentration in water in micrograms per liter (Ghurye, Clifford, and Tripp 1999):

Bed volume = 210,000 (As)-0.57

The actual bed volume is much lower due to the presence of other competing ions in natural water. Arsenic removal capacities of activated alumina have been reported to vary from 1 mg g-1 to 4 mg g-1 (Fox 1989; Gupta and Chen 1978). Clifford (1999) reported the selectivity of activated alumina as:

-1 -1 -1 -1 -2 -2 -1 -1 -1 -1 -1 OH >H2AsO4 >Si(OH)3O >HSeO3 >F>SO4 >CrO4 >>HCO3 >Cl >NO3 >Br >I

Regeneration of saturated alumina is carried out by exposing the medium to 4% caustic soda (NaOH), either in batch or by flow through the column resulting in high-arsenic-contaminated caustic waste water. The residual caustic soda is then washed out and the medium is neutralized with a 2% solution of sulfuric acid rinse. During the process about 5–10% of the alumina is lost and the capacity of the regenerated medium is reduced by 30–40%. The activated alumina needs replacement after 3–4 regenerations. As with the coagulation process, prechlorination improves the column capacity dramatically. The activated alumina-based sorptive media used in Bangladesh and India include:

• BUET activated alumina • Alcan enhanced activated alumina • Apyron arsenic treatment unit • Oxide (India) Pvt. Ltd. • RPM Marketing Pvt. Ltd.

Arsenic is removed by sorptive filtration through activated alumina. Some units use pretreatment (for example oxidation, sand filtration) to increase efficiency. The Alcan enhanced activated alumina arrangement is shown attached to a tubewell in figure 6 (see page 178). The unit is simple and robust in design. No chemicals are added during treatment and the process wholly relies on the active surface of the media for adsorption of arsenic from water. Other ions present in natural water, such as iron and phosphate, may compete for active sites on alumina and reduce the arsenic removal capacity of the unit. Iron present in shallow tubewell water at elevated levels will eventually accumulate in an activated alumina bed and interfere with flow of water through the bed. The unit can produce more than 3,600 liters of arsenic-safe drinking water per day for 100 families. Apyron Technologies Inc. (United States of America) has developed an

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Figure 6. Alcan Enhanced Activated Alumina Unit (Drawn by Ahmed, 2003)

Inlet (water from tubewell)

Oulet (treated water) Tubewell

arsenic treatment unit in which its Aqua-Bind™ medium is used for arsenic removal from groundwater. Aqua-Bind contains activated alumina and manganese oxides that can selectively remove As(III) and As(V). The BUET activated alumina units have oxidation and prefiltration provisions prior to filtration through activated alumina.

Granular ferric hydroxide (AdsorpAs®) is a highly effective adsorbent used for the adsorptive removal of arsenate, arsenite, and phosphate from natural water. It has an adsorption capacity of 45g kg-1 for arsenic and 16 g kg-1 for phosphorus on a dry weight basis (Pal 2001). M/S Pal Trockner (P) Ltd, India, and Sidko Limited, Bangladesh, have installed several granular ferric hydroxide-based arsenic removal units in India and Bangladesh. The proponents of the unit claim that AdsorpAs® has very high arsenic removal capacity, and produces relatively small amounts of residual spent media. The typical residual mass of spent AdsorpAs® is in the range of 5–25 g/m3 of treated water. The typical arrangement of the Sidko/Pal Trockner unit (figure 7) requires aeration for oxidation of water and prefiltration for removal of iron flocs before filtration through active media. Chemicon and Associates has developed and marketed an arsenic removal plant based on adsorption technology in which crystalline ferric oxide is used as an adsorbent. The unit has a prefiltration unit containing 178 179 manganese oxide for oxidation of As(III) to As(V) and retention of iron precipitates.

Figure 7. Granular Ferric Hydroxide-Based Arsenic Removal Unit (Pal, 2001)

Gravel filter bed Adsorption bed

Treated Contaminated water outflow water inflow Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The Sono 3-Kolshi filter shown in figure 8 uses zero valent iron filings (cast-iron turnings), sand, brick chips, and wood coke to remove arsenic and other trace metals from groundwater in Bangladesh (Munir and others 2001; Khan and others, 2000). The filtration system consists of three kalshi (burned clay pitchers), widely used in Bangladesh for storage of drinking and cooking water. The top kalshi contains 3 kg cast-iron turnings from a local machine shop or iron works and 2 kg sand on top of the iron turnings. The middle kalshi contains 2 kg sand, 1 kg charcoal, and 2 kg brick chips. Brick chips are also placed around the holes to prevent leakage of finer materials. Tubewell water is poured in the top kalshi and filtered water is collected from the bottom kalshi.

Figure 8. Three Kalshi Filter for Arsenic Removal (Drawn by Ahmed, 2003 based on Khan and Others, 2000)

Raw water

Filter medium 1: sand, iron fillings & brick chips

Filter medium 2: sand, charcoal & brick chips

Filtered water

Nikolaidis and Lackovic (1998) showed that 97% of arsenic can be removed by adsorption on a mixture of zero valent iron filings and sand through formation of coprecipitates, mixed precipitates, and adsorption onto the ferric hydroxide solids. Thousands of units using this technology were distributed in arsenic-affected areas but the feedback from the users was not very encouraging. If groundwater contains excess iron the one-time use unit quickly becomes clogged. Field observations indicated that the iron filings bond together into solid mass over time, making cleaning and replacement of materials difficult. The unit has been renamed Sono 45-25 arsenic removal technology and the materials of the upper two units have been put into two buckets to overcome some of the problems mentioned above.

The BUET iron-coated sand filter was constructed and tested on an experimental basis and found to be very effective in removing arsenic from groundwater. The unit needs pretreatment for the removal of excess iron to avoid clogging of the active filter bed. Iron-coated sand is prepared following a procedure similar to that adopted by Joshi and Chaudhuri (1996). The Shapla arsenic filter (figure 9 see page 180), a household-level arsenic removal unit, has been developed and is

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

Figure 9. Shapla Filter for Arsenic Removal at Household Level by IDE (Ahmed, 2003)

Lid

Flexible water delivery pipe Iron-coated crushed brick particles Cloth filter on perforated plate Treated Support water in a bucket

being promoted by International Development Enterprises (IDE) , Bangladesh. The adsorption medium is iron-coated brick chips manufactured by treating brick chips with a ferrous sulfate solution. It works on the same principle as iron-coated sand. The water collected from contaminated tubewells is allowed to pass through the filter medium, which is placed in an earthen container with a drainage system underneath.

The READ-F arsenic filter is promoted by Shin Nihon Salt Co. Ltd., Japan, and Brota Services International, Bangladesh, for arsenic removal in Bangladesh. READ-F displays high selectivity for arsenic ions under a broad range of conditions and effectively adsorbs both arsenite and arsenate. Oxidation of arsenite to arsenate is not needed for arsenic removal, nor is adjustment of pH required before or after treatment. The READ-F is ethylene-vinyl alcohol copolymer-borne

hydrous cerium oxide in which hydrous cerium oxide (CeO2.nH2O) is the adsorbent. Laboratory tests at the BUET and field testing of the materials at several sites under the supervision of the BAMWSP showed that the adsorbent is highly efficient in removing arsenic from groundwater (Shin Nihon Salt Co. Ltd. 2000). One household treatment unit and one community treatment unit 180 181 based on the READ-F adsorbent are being promoted in Bangladesh. The units need iron removal by sand filtration to avoid clogging of the resin bed by iron flocs. In the household unit both the sand and resin beds have been arranged in one container while in the community unit sand and resin beds are placed in separate containers. READ-F can be regenerated by adding sodium hydroxide and then sodium hypochloride and finally washing with water. The regenerated READ-F needs neutralization by hydrochloric acid and washing with water for reuse.

The SAFI filter is a household-level candle filter developed and used in Bangladesh. The candle is made of composite porous materials such as kaolinite and iron oxide on which hydrated ferric oxide is deposited by sequential chemical and heat treatment. The filter works on the principle of adsorption filtration on the chemically treated active porous composite materials of the candle.

The ion exchange process is similar to that of activated alumina; however, the medium is a synthetic resin of relatively well defined ion exchange capacity. The synthetic resin is based on a cross-linked polymer skeleton called the matrix. The charged functional groups are attached to Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

the matrix through covalent bonding and fall into strongly acidic, weakly acidic, strongly basic, and weakly basic groups (Clifford 1999). The resins are normally used for removal of specific undesirable cations or anions from water. The strongly basic resins can be pretreated with anions such as Cl-1 and used for the removal of a wide range of negatively charged species, including arsenate. Clifford (1999) reports the relative affinities of some anions for strong-base anion resins as:

-2 -2 -2 -1 -1 -1 -2 -2 -3 -1 -1 CrO4 >>SeO4 >>SO4 >>HSO4 >NO3 >Br >HAsO4 >SeO3 >HSO3 >NO2 >Cl

The arsenic removal capacity is dependent on sulfate and nitrate contents of raw water, as sulfate and nitrate are exchanged before arsenic. The ion exchange process is less dependent on the pH of water. Arsenite, being uncharged, is not removed by ion exchange. Hence, preoxidation of As(III) to As(V) is required for removal of arsenite using the ion exchange process. The excess oxidant often needs to be removed before the ion exchange in order to avoid damage of the sensitive resins. Development of ion-specific resin for exclusive removal of arsenic can make the process very attractive.

Tetrahedron (United States) promoted ion exchange-based arsenic removal technology in Bangladesh (figure 10). About 150 units were installed at various locations in Bangladesh under the supervision of the BAMWSP. The technology proved its arsenic removal efficiency even at high flow rates. It consists of a stabilizer and an ion exchanger (resin column) with facilities for chlorination using chlorine tablets. Tubewell water is pumped or poured into the stabilizer through a sieve containing the chlorine tablet. The water mixed with chlorine is stored in the stabilizer and subsequently flows through the resin column when the tap is opened for collection of water. Chlorine from the tablet dissolved in the water kills bacteria and oxidizes arsenic and iron.

Water System International (WSI) India has developed and patented an ion exchange process for arsenic removal from tubewell water. The so-called bucket of resin unit is encased in a rectangular container placed adjacent to the tubewell. There are three cylinders

Figure 10. Tetrahedron Arsenic Removal Technology (Drawn by Ahmed, 2003)

Chlorine source

Sieve stabilizer Column head tap Stone chips

Stand

Resin column (ion exchanger)

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

inside the container. Water in the first cylinder is mixed with an oxidizing agent to oxidize As(III) to As(V) while As(V) is removed in the second cylinder, which is filled with WSI- patented processed resin. The treated water is then allowed to flow through a bed of activated alumina to further reduce residual arsenic from water. Ion Exchange (India) Ltd. has also developed and marketed an arsenic removal community-level plant based on ion exchange resin.

Membrane Techniques Synthetic membranes can remove many contaminants from water including bacteria, viruses, salts, and various metal ions. They are of two main types: low-pressure membranes, used in microfiltration and ultrafiltration; and high-pressure membranes, used in nonofiltration and reverse osmosis. The latter have pore sizes appropriate to the removal of arsenic.

In recent years, new-generation membranes for nonofiltration and reverse osmosis have been developed that operate at lower pressure and are less expensive. Arsenic removal by membrane filtration is independent of pH and the presence of other solutes but is adversely affected by the presence of colloidal matters. Iron and manganese can also lead to scaling and membrane fouling. Once fouled by impurities in water, the membrane cannot be backwashed. Water containing high levels of suspended solids requires pretreatment for arsenic removal using membrane techniques. Most membranes, however, cannot withstand oxidizing agents. EPA (2002) reported that nonofiltration was capable of over 90% removal of arsenic, while reverse osmosis provided removal efficiencies of greater that 95% when at ideal pressure. Water rejection (about 20–25% of the influent) may be an issue in water- scarce regions (EPA 2002). A few reverse osmosis and nonofiltration units have been successfully used in Bangladesh on an experimental basis.

Comparison of Arsenic Removal Technologies 182 183 Remarkable technological developments in arsenic removal from rural water supply based on conventional arsenic removal processes have taken place during the last five years. The relative advantages and disadvantages of different arsenic removal processes are compared in table 1.

Competition between arsenic removal technologies is based on a number of factors. Cost appears to be a major determinant in the selection of treatment option by users. The available costs of some of the arsenic removal technologies have been summarized in table 2. The costs of similar technologies in India are also compared in table 3. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 1. Comparison of Main Arsenic Removal Technologies

Technology Advantages Disadvantages

Oxidation and • Relatively simple, low cost, but • Processes remove only some of sedimentation: air slow process (air) the arsenic oxidation, chemical • Relatively simple and rapid • Used as pretreatment for oxidation process (chemical) other processes • Oxidizes other impurities and kills microbes Coagulation and filtration: • Relatively low capital cost • Not ideal for anion-rich water alum coagulation, iron • Relatively simple in operation treatment (e.g. containing coagulation • Common chemicals available phosphates) • Produces toxic sludge • Low removal of As(III) • Preoxidation is required • Efficiencies may be inadequate to meet strict standards Sorption techniques: • Relatively well known and • Not ideal for anion-rich water activated alumina, iron- commercially available treatment (e.g. containing coated sand, ion exchange • Well-defined technique phosphates) resin, other sorbents • Many possibilities and scope • Produces arsenic-rich liquid and for development solid wastes • Replacement/regeneration is required • High-tech operation and maintenance • Relatively high cost Membrane techniques: • Well-defined and high removal • High capital and running costs nanofiltration, reverse efficiency • High-tech operation and osmosis • No toxic solid wastes produced maintenance • Capable of removal of other • Arsenic-rich rejected water is contaminants produced

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Table 2. Comparison of Arsenic Removal Mechanisms and Costs in Bangladesh

Type of unit Removal Type Capital cost/ Operation and mechanism unit(US$) maintenance costs/ family/year (US$)

Sono 45-25 Adsorption by oxidized Household 13 0.5–1.5 iron chips and sand Shapla filter Adsorption of iron- Household 4 11 coated brick chips SAFI filter Adsorption Household 40 6 Bucket Oxidation and Household 6–8 25 treatment unit coagulation- sedimentation-filtration Fill and draw Oxidation and Community 250 15 coagulation- (15 households) sedimentation-filtration Arsenic Aeration, sedimentation, Urban water 240,000 1–1.5 removal unit rapid filtration supply(6,000 for urban water households) supply Sidko Adsorption by granular Community 4,250 10

Fe(OH)3 (75 households) Apyron Adsorption by Al-Mn Community Taka 0.01/L/100ppb arsenic oxides (Aqua-BindTM) (65 households) concentration in water Iron-arsenic Aeration, sedimentation, Community 200 1 removal plant rapid filtration (10 households)

184 185 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 3. Comparison of Costs of Different Arsenic Treatment Technologies in India

Technology Treatment process Type Capacity Cost (US$) (manufacturer)

AMAL (Oxide Adsorption by activated Household 7,000–8,000 L 50 India Catalyst alumina Community 1,500,000 L/cycle 1,250; 400/charge Pvt. Ltd., WB) RPM Marketing Activated alumina + Community 200,000/cycle 1,200; 500/charge Pvt. Ltd. AAFS-50 (patented) All India Institute Oxidation followed Household 30 L/d 5 of Hygiene & by coprecipitation- Community 12,000 L/d 1,000 Public Health filtration Public Health Adsorption on red Community 600–1,000 L/h 1,000 Engineering hematite, sand, and Department, India activated alumina Pal Trockner Ltd., Adsorption by ferric Household 20 L/d 8 India hydroxide Community 900,000 L/cycle 2,000; 625/charge Chemicon & Adsorption by ferric Community 2,000,000 L/cycle 4,500; 400/charge Associates oxide Ion Exchange Adsorption by ion Community 30,000 L/cycle 2,000 (India) Ltd. exchange resin

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3. Laboratory and ield Methods of Arsenic Analysis

nalysis of groundwater for arsenic has become a routine procedure in the assessment of the Aquality of water for the development of groundwater-based water supply. The need for stringent water quality standards and guidelines has given rise to demand for analysis of arsenic at trace levels. Laboratory analytical methods are relatively more accurate than field testing but involve considerable measurement skills and costs. The extent and nature of contamination in many countries demands large-scale measurements of arsenic for screening as well as monitoring and surveillance of water points. Developing countries with limited laboratory capacity have adopted low-cost semiquantitative arsenic measurement by field test kits to accomplish the huge task of screening and monitoring. This section provides a short overview of laboratory and field methods of analysis of arsenic in water.

Laboratory Methods A variety of analytical methods for laboratory determination of arsenic has been described in has literature but many of them essentially employ similar principles. The most common methods prescribed for use after proper validation by international and national standard methods include atomic absorption spectrometry (AAS), inductively coupled plasma (ICP), anodic stripping voltammetry (ASV), and silver diethyldithiocarbamate (SDDC) spectrometric method. AAS is a sensitive single-element technique with known and controllable interference. Both hydride generation (HG) and graphite furnace (GF) AAS methods are widely used for analysis of arsenic in water. ICP atomic emission spectrometry (AES) and mass spectrometry (MS) are multielement techniques, also with known and controllable interference. ASV is a useful technique for analysis of dissolved arsenic and arsenic speciation but needs special precautions for accuracy. The SDDC spectrometric method has been widely used for its simplicity and low cost but suffers from interference and reproducibility. A summary of laboratory analytical techniques, with important features, is presented in table 4 (Rasmussen and Anderson 2002; Khaliquzzaman and Khan 2003). 186 187

Field Test Kit Laboratory methods of arsenic measurement are costly and the number of laboratories with arsenic measurement capabilities is too few in the developing countries to meet present needs. Field test kits have been developed for detection and measurement of arsenic by different institutions and agencies in Bangladesh and in other countries. The detection and semiquantative measurement of arsenic by all field test kits is based on the Gutzeit procedure, which involves the conversion of all arsenic in water into As(III) by reduction, and then formation of arsine gas by further reduction using nascent hydrogen in an acid solution in a Gutzeit generator. The technique is also known as the mercuric bromide stain method (APHA-AWWA-WEA 1985). Presently available arsenic test kits have been developed adopting various modifications of the method. The arsine, thus liberated, produces a yellow to brown stain on a vertical paper strip impregnated Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 4. Laboratory Analysis Methods for Arsenic

Techniquesa Method Sample size System cost Comments Methodsb detection (ml) (thousands US$) limit (mg L-1)

HG-AAS 0.05–2 50 20–100 Single element ISO 11969 (1990) SM 3114BC (1998) EPA 1632 (1996) ASTM 2972-93B (1998) GF-AAS 1–5 1–2 30–100 Single element ISO/CD 15586 (2000) SM 3113B(1998) EPA 200.9 (1994) ASTM 2972-93C (1998) ICP-AES 35–50 10–20 60–200 Multielement SM 3120B(1998) EPA 200.7 (1994) ICP-MS 0.02–1 10–20 150–400 Multielement SM 3125B (1998) EPA 200.8 (1994) ASV 0.1–2 25–50 5–20 Only free EPA 7063 (1996) dissolved arsenic SDDC 1–10 100 2–10 Single element ISO 6595 (1982) SM 3500 (1998) a Abbreviations used: ASV anodic stripping voltammetry GF-AAS graphite furnace-atomic absorption spectrometry HG-AAS hydride generation-atomic absorption spectrometry ICP-AES inductively coupled plasma-atomic emission spectrometry ICP-MS inductively coupled plasma-mass spectrometry SDDC silver diethyldithiocarbamate b Abbreviations used/references: ASTM American Society for Testing and Materials (ASTM 1998) CD Committee Draft EPA Environmental Protection Agency, United States ISO International Organization for Standardization (ISO 1982, 1996, 2000) SM Standard Method with mercuric bromide. The amount of arsenic present in the water is directly related to the intensity of the color. The color developed on mercuric bromide-soaked paper is compared either with a standard color chart or measured by a photometer to determine the arsenic concentration of the water sample. In some field test kits the generated arsine is passed through a column containing a roll of cotton moistened with lead acetate solution to absorb hydrogen sulfide gas, if any is present in the gas stream. The important features of some arsenic field test kits are summarized in table 5 (see page 188).

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Table 5. Comparison of Arsenic Field Test Kits

Kit type Manufacturer Range (µg L-1) Cost (US$) Comments

E-Mark kit M/S E-Mark, Germany 100–3,000 (old) 50–100 Colors match with ranges 5–500 (new) of arsenic concentration. HACH kit HACH Company, USA 10–500 (50 ml One-time use for 100– sample) 300 tests 350–4,000 (9.6 ml sample) Econo QuickTM Industrial Test Systems 10–1,000 Inc., USA AIIH&PH kit All India Institute of Yes/No type 40–60 Produces color if Hygiene and Public at 50 µg L-1 concentration exceeds Health (AIIH&PH) 50 µg L-1. One-time use Aqua kit Aqua Consortium (India) Yes/No type at 50 µg L-1 AAN-Hironaka Dr. Hironaka, Fukuoka 20–700 Not on sale Colors match with range kit City Inst. For Hygiene & of arsenic concentration. Environment, Japan One-time use for 100 tests NIPSOM kit NIPSOM, with technical 10–700 40–80 assistance from AAN- Hironaka GPL kit General Pharmaceuticals 10–2,500 Ltd., Dhaka BUET kit BUET, Dhaka 10–700 Not on sale Digital Wagtech International <10–500 1,250 Quantitative values Arsenator obtained

188 189 A number of researchers and organizations have evaluated the performance of arsenic field test kits. The National Environmental Engineering Research Institute, Nagpur, India, evaluated the Asian Arsenic Network (AAN) kit (0.02–0.70 mg L-1), the National Institute of Preventive and Social Medicine (NIPSOM) kit, the Merck kit (0.10–3.0 mg L-1), the Aqua kit, and the AIIH&PH kit (NEERI- WHO 1998). The Shriram Institute for Industrial Research, India, studied the performance of five different arsenic field test kits used in India (SIIR 1998). NGO Forum for Drinking Water Supply and Sanitation, Bangladesh, in collaboration with the School of Environmental Studies, Jadavpur University, Calcutta, West Bengal, India, evaluated the NIPSOM kit, the General Pharmaceutical Ltd. (GPL) kit, the Merck kit (0.025–3.0 mg L-1), and the Arsenator (NGO Forum-JU 1999). In Bangladesh the performance of some arsenic test kits was evaluated as a requirement for the procurement of field test kits by the Bangladesh Arsenic Mitigation Water Supply Project (BAMWSP 2001). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Recently, several arsenic field test kits were tested for their efficacy under the EPA’s Environmental Technology Verification Program. The performances of the field test kits were evaluated for accuracy, precision, linearity, method detection limit, matrix interference effects, operator bias, and rate of false positives or false negatives. The EPA issued verification reports and verification statements for these arsenic field test kits (Abbgy and others 2002; EPA 2003)

The accuracy of arsenic measurement using the mercuric bromide stain method depends on many factors. The first consideration is the method’s ability to eliminate the effects of interfering substances such as sulfide. The second consideration is the generation of arsine gas, which can be achieved in several ways. Most kits use zinc, which may contain arsenic as an impurity and interfere with the process. The advantage of using the chemicals in tablet form can be availed in the case of arsine generation using sodium tetrahydroborate (NaBH4) and aminosulfonic acid. An excess amount of the reducing agent is required in this case to produce sufficient hydrogen gas to strip the arsine gas out of the solution and transfer it to mercuric bromide paper. The passing of arsine gas through mercuric bromide paper gives more reliable results at low concentrations than passing it over the surface of a small strip of mercuric bromide paper inserted into the reactor. The third consideration is that quantification of the arsenic concentration by visual comparison is subjective and varies from person to person. The faint yellow color is not discernible to the average human eye. Again, for better results, the color comparison should be made as soon as possible as the light-sensitive stain changes color rapidly. The results obtained by arsenic field test kits are, therefore, very much dependent on the type and quality of chemicals, preparation, the preservation and age of the chemicals, the quality of water, the quality of equipment, the operator’s skill, and the procedure of measurement (Jalil and Ahmed 2003).

The costs of equipment for arsenic measurement are shown in tables 4 and 5. The equipment costs of most laboratory methods are very high. Operation and maintenance costs are also very high. Further, the service facilities of laboratory equipment manufacturers are not always available in developing countries. Semiquantitative measurement using arsenic field test kits can be done at low cost, making them affordable in developing countries, though the level of accuracy is lower than with laboratory tests.

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4. Alternative Water Supply Options

he shallow tubewell technology in alluvial aquifers of recent origin in the South Asia Region, Twhich provided drinking water at low cost, has been found to be contaminated with arsenic in many places. This unexpected calamity has exposed millions of people in contaminated areas to unsafe water. The risk has been magnified by the existence of very high levels of arsenic in tubewell water in areas where the percentage of contaminated tubewells is also very high. In the absence of an alternative source, people in such hotspots often have an unfortunate choice between continuing to drink arsenic-contaminated water or using unprotected surface water and exposing themselves to the risk of waterborne diseases. Arsenic toxicity has no known effective treatment, but drinking arsenic-free water can greatly reduce the symptoms. Apart from treatment of arsenic-contaminated water, potential alternative water sources for arsenic-safe water supplies include:

• Deep tubewell • Dug or ring well • Rainwater harvesting • Treatment of surface water • Piped water supply

Deep Tubewell Aquifers are water-containing rocks that have been laid down during different geological time periods. Deeper aquifers are often separated from those above by relatively impermeable strata that keep them free of the arsenic contamination of shallower aquifers1. A study in Bangladesh by the British Geological Survey (BGS) and the DPHE has shown that of tubewells with a depth greater than 150 m, only about 1% have levels of arsenic above 50 µg L-1, and 5% have arsenic levels above 10 µg L-1 (BGS-DPHE 2001). As such, deep aquifers separated from shallow contaminated aquifers by impermeable layers can be a dependable source of arsenic-safe water.

The presence of a relatively impermeable layer separating a deep uncontaminated aquifer from a 190 191 shallow contaminated aquifer is a prerequisite for installation of a deep tubewell for arsenic-safe water. The annular spaces of the boreholes of the deep tubewells must be sealed, at least at the level of the impermeable strata, to avoid percolation of arsenic-contaminated water (figure 11). It is very difficult to seal a small-bore tubewell but technological refinement using clay as a sealant is ongoing. A protocol for the installation of deep tubewells for arsenic mitigation has been developed in Bangladesh (Government of Bangladesh 2004).

In the coastal area of Bangladesh proven arsenic-safe deep aquifers protected by overlying thick clay layers are available for the development of safe water supplies. In other areas, arsenic-safe aquifers separated from arsenic-contaminated shallow aquifers are available but extensive and very costly hydrogeological investigations are required to delineate those

1 In some areas, e.g. China, the deeper aquifers may be arsenic-affected. See paper 1. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Figure 11. Deep Tubewell with Clay Seal (Ahmed, 2004)

Manually operated deep tubewell

Slity Clay

Arsenic-contaminated Water table shallow aquifer (sandy silt) Clay seal

Relatively impermeable Clayey layer

Arsenic-safer deep aquifer (fine to medium Strainer sand)

Sand trap

aquifers. In the meantime, installation of deep tubewells following a deep tubewell protocol will continue through examination of water quality and soil strata in test boreholes in the prospective deep tubewell areas.

However, there are many areas where separating impermeable layers are absent and aquifers are formed by stratified layers of silt and medium sand. The deep tubewells in those areas may yield arsenic-safe water initially but are likely to experience an increase in the arsenic content of water over time due to mixing of contaminated and uncontaminated waters. However, recharge of deep aquifers by infiltration through coarse media and replenishment by the horizontal movement of water are likely to keep such aquifers arsenic free even after prolonged water abstraction. Information about the configuration of an aquifer and its recharge mechanism is critical for the installation of deep tubewells.

Experience in the design and installation of tubewells shows that reddish sand produces the best-quality water in terms of dissolved iron and arsenic. The reddish color of sand is produced by oxidation of iron on sand grains in a ferric form that will not release arsenic or iron in groundwater. On the contrary, ferric iron-coated sand will adsorb arsenic from groundwater. This mechanism is probably responsible for the relative freedom from arsenic of the Dhaka water supply, in contrast to the arsenic contamination that occurs in surrounding areas. Hence, installation of tubewells in reddish sand, if available, should be safe from arsenic contamination.

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Dug or Ring Well

Dug wells are the oldest method of groundwater withdrawal for water supply. The water from dug wells has been found to be relatively free from dissolved arsenic and iron, even in locations where tubewells are contaminated. The reasons for this are not fully known, but possible explanations include:

• The oxidation of dug well water due to its exposure to open air and agitation during water withdrawal can cause precipitation of dissolved arsenic and iron. • Dug wells accumulate groundwater from the top layer of a water table, which is replenished each year by arsenic-safe rain and percolation of surface waters through the aerated zone of the soil. The fresh recharges also dilute contaminated groundwater.

A study in an acute arsenic problem area shows that frequent withdrawal of water initiates ingress of arsenic-contaminated water into dug wells and reduces the subsequent in situ oxidation that, under normal operating conditions, increases the oxygen content of water and the reduction of arsenic. Since the upper layer of soil contains organic debris, dug well water is often characterized by bad odor, high turbidity and color, and high ammonia content. Dug wells are also susceptible to bacterial contamination. Percolation of contaminated surface water is the most common cause of well water pollution. Satisfactory protection against bacteriological contamination is possible by sealing the well top with a watertight concrete slab, lining the well, and constructing a proper apron around the well. Water may be withdrawn through the installation of a manually operated handpump. Completely closed dug wells have good sanitary protection but the absence of oxygen can adversely affect the quality of the water.

Construction and operational difficulties have been encountered in silty and loose to medium- dense sandy soils. Sand boiling interferes with the digging, and sometimes leads to collapse of 192 193 dug wells. Constructed dug wells are also gradually filled up during operation by sand boiling.

Water in the well needs chlorination for disinfection after construction. Application of lime also improves the quality of dug well water. Disinfection of well water should be continued for open dug wells during operation by pot chlorination, but controlling the chlorine dose in dug well water is difficult.

Surface Water Treatment A prospective option for the development of a surface water-based water supply system is the construction of community slow sand filters, commonly known as pond sand filters in Bangladesh, where they were originally designed for the filtration of pond water. This is a package-type slow sand filter unit developed to treat surface waters, usually low-saline pond water, for domestic water supply in coastal areas. The water from the pond or river is pumped by Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

a manually operated tubewell to feed the filter bed, which is raised from the ground (figure 12). The treated water is collected through a tap. Tests have found that treated water from a pond sand filter is normally bacteriologically safe or within tolerable limits. The sand in the filter bed usually needs to be cleaned and replaced every two months. The operating conditions for slow sand filters include:

• Low turbidity, not exceeding 30 nephelometric turbidity units (NTU) • Low bacterial count • No algal bloom, absence of cynobacter • Free from bad smell and color

Figure 12. Pond Sand Filter for Treatment of Surface Water (Ahmed and Others, 2002)

Handpump for water supply to filter

Surface water

Clear Filter sand water

Coarse aggregate

Under drainage system Raw water from pond

A protected surface water source is ideal for slow sand filtration. The problems encountered when the above operating conditions are not maintained include low discharge, the need for frequent washing, and poor effluent quality. Since these are small units, community involvement in their operation and maintenance is absolutely essential in order to keep the system operational. By June 2000, the DPHE had installed 3,710 pond sand filter units, a significant proportion of which remain out of operation due to poor maintenance, drying of the source, or excessive contamination of the water source.

The package-type slow sand filter is a low-cost technology with very high efficiency in turbidity and bacterial removal. It has received preference as an alternative water supply system for medium-size settlements in arsenic-affected areas. Although pond sand filters have a very high bacterial removal efficiency they may not reduce bacterial count to acceptable levels in cases of

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heavily contaminated surface water. In such cases, the treated water may require chlorination to meet drinking water standards.

A combined filter consisting of roughing filters and a slow sand filter is needed when the turbidity of water exceeds 30 NTU. The roughing filters remove turbidity and color to levels acceptable for efficient operation of the slow sand filter. Small-scale conventional surface water treatment plants involving coagulation-sedimentation-filtration and disinfection can be constructed to cope with variable raw water quality for community water supplies but the cost will be relatively high.

Rainwater Harvesting Rainwater harvesting can be an alternative source of drinking water in arsenic-contaminated South Asian countries. The relative advantages and disadvantages of rainwater harvesting are shown in table 6. A rainwater-based water supply system requires a determination of the storage tank capacity and the catchment area for rainwater collection in relation to the water requirement, rainfall intensity, and distribution. The availability of rainwater is limited by the rainfall intensity and availability of a suitable catchment area. The unequal distribution of rainwater over the year in Asian countries requires a larger storage tank for uninterrupted water supply throughout the year. This storage tank constitutes the main cost of the system.

The catchment area for rainwater collection is usually the roof, which is connected to the storage tank by a gutter system. Rainwater can be collected from any type of roof but concrete, tiles, and metal roofs give clean water. The corrugated iron sheet roofs commonly used in Bangladesh and India perform well as catchment areas. The poorer segments of the population are in a

Table 6. Advantages and Disadvantages of Rainwater Collection System

Advantages Disadvantages 194 195 • The quality of rainwater is comparatively good • The initial cost may prevent a family from installing a rainwater harvesting system • The system is independent and therefore • Water availability is limited by the rainfall suitable for scattered settlements intensity and available roof area • Local materials and craftsmanship can be used • Mineral-free rainwater has a flat taste, which in construction of rainwater system may not be liked by many • No energy costs are incurred in running the • Mineral-free water may cause nutrition system deficiencies in people who are on mineral- deficient diets • Ease of maintenance by the owner/user • The poorer segment of the population may not have a roof suitable for rainwater harvesting • The system can be located very close to the • May not last through the entire dry season. consumption point Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Figure 13. Plastic Sheet Catchment (Ahmed disadvantageous position in respect to the and others, 2002) utilization of rainwater as a source of water supply. These people have smaller thatched roofs or no roof at all to be used as a catchment for rainwater collection. A thatched roof can be used as a catchment area by covering it with polyethylene but it requires good skills to guide water to the storage tank. In coastal areas of Bangladesh, cloths fixed at four corners with a pitcher underneath are used during rainfall for rainwater collection. A plastic sheet, as shown in figure 13, has been tried as a catchment for rainwater harvesting for people who do not have a roof suitable for rainwater collection. The use of land surface as a catchment area and underground gravel or sand-packed reservoirs as storage tanks can be an alternative system of rainwater collection and storage. In this case, the water has to be channeled towards the reservoir and allowed to pass through a sand bed before entering underground reservoirs. This process is analogous to recharge of underground aquifers by rainwater during the rainy season for utilization in the dry season.

The quality of rainwater is relatively good but it is not free of all impurities. Analysis of stored rainwater has shown some bacteriological contamination. Cleanliness of the roof and storage tank is critical to maintaining the good quality of rainwater. The first runoff from the roof should be discarded to prevent entry of impurities from the roof. If the storage tank is clean, the bacteria or parasites carried with the flowing rainwater will tend to die off. Some devices and good practices have been suggested to store or divert the first foul flush away from the storage tank. In case of difficulties in the rejection of first flow, cleaning of the roof and gutter at the beginning of the rainy season and their regular maintenance are very important to ensure better quality of the rainwater. The storage tank requires cleaning and disinfection when the tank is empty or at least once in a year. Rainwater is essentially lacking in minerals, the presence of which is considered essential in appropriate proportions. The mineral salts in natural ground and surface waters sometimes impart a pleasing taste to water.

Piped Water Supply Piped water supply is the ultimate goal of safe water supply to the consumer because:

• Water can be delivered to close proximity of the consumers. • Piped water is protected from external contamination.

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• Better quality control through monitoring is possible. • Institutional arrangements for operation and maintenance are feasible. • Water of required quantity can be collected with ease.

In terms of convenience in collection and use, only piped water can compete with the existing system of tubewells for water supply. It can be a feasible option for clustered rural settlements and urban fringes. Water can be made available through house connection, yard connection, or standpost, depending on the affordability of each option to the consumer. The water can be produced, according to demand, by sinking deep tubewells into an arsenic-safe aquifer or by treatment of surface water or even arsenic-contaminated tubewell water by community-level treatment plants. Rural piped water supply has received priority for arsenic mitigation in Bangladesh and a large number of pilot schemes by different organizations are under implementation. It appears that piped water supply will be a suitable option for populations living in clustered settlements, but it will be a difficult and costly option for scattered populations.

Cost Comparison of Alternative Water Supply Options As has been discussed in this chapter, a variety of alternative technological options is available for water supply in arsenic-affected areas. The cost of arsenic mitigation will depend on the type of technology adopted. The costs of installation and operation of some major technological options available from various organizations involved in arsenic mitigation are summarized in table 7.

The quality and quantity of water, reliability, cost, and convenience of collection of water vary widely for the various options. Deep tubewells can provide water at nominal operation and maintenance costs but they are not feasible, nor able to provide arsenic-free water, at all locations. Dug or ring wells can provide water at moderate installation and nominal operation and maintenance costs. It is not yet fully known whether the quality of water can be maintained at desired levels. Bacteriological quality is likely to remain at safe levels under conditions of proper 196 197 sanitary protection. Piped water supply can be provided at a higher cost and with relatively higher operation and maintenance costs but the convenience and health benefits are much greater because water of adequate quantity and relatively superior quality for all domestic purposes, including sanitation, becomes available at or near residences. Increasing the number of households connected reduces average costs. Available data suggest that the average cost of piped water supply becomes lower than other options when the number of households exceeds 500 (see paper 4). The relative cost of installation for a rainwater harvesting system at household level with only about 50% reliability is very high. Installation of community rainwater harvesting systems may be cheaper, but management of such systems may be difficult. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 7. Costs of Alternative Technological Options in Arsenic-Affected Areas

Alternative No. of Unit cost Operation and Comments Technological households (US$) maintenance options per unit costs/year (US$)

Rainwater harvesting 1 200 5 Low reliability Dug or ring well 25 800 3 Depth about 8 m Deep tubewell 50 900 4 Depth about 300 m Pond sand filters 50 800 10–20 Slow sand filter process Surface water treatment 1,000 15,000 3,000 Conventional process Piped water supply 1,000 40,000 800 Systems are based on arsenic-safe groundwater

Source: Government of Bangladesh 2002.

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5. Operational Issues

he presence of arsenic in low concentration and the need to reduce it to levels associated Twith desired health benefits have given rise to many operational difficulties. Measurement of arsenic at low concentration is difficult, as is the monitoring of treatment system performance. Validation of the claims of proponents concerning the performance of treatment technologies and arsenic measurement devices is an important requirement. Safe disposal of toxic sludge and spent media is an environmental concern. The technologies based on patented media or processes and imported components may face operational difficulties due to lack of availability and supply of materials and components.

Operational issues are very important for small-scale water treatment facilities at the household and community levels. It is not possible to make an institutional arrangement for operation, repair, and maintenance of small water supply systems. People’s participation and capacity building at the local level are considered vital for keeping the system operational. There are many examples of failure of small water supply systems in the absence of initiatives, commitment, and ownership of the system. In many cases, the small system may be more costly due to scaling down of a conventional system for water treatment.

Technology Verification and Validation Quite a lot of development of arsenic treatment and measurement technologies has taken place over the last five years in response to demand. Verification and validation of the claims of these technologies are needed to help buyers select the right technology. The EPA has developed protocols for validation of arsenic treatment technologies and arsenic field test kits under its Environmental Technology Verification Program. The protocols have been developed in collaboration with the Environmental Technology Verification Program in Canada and Bettle Laboratories, United States (EPA 2003). The WHO has developed generic protocols for adoption in South-East Asia Region countries (WHO 2003).

A systematic evaluation of arsenic mitigation technologies is being conducted under the 198 199 Environmental Technology Verification–Arsenic Mitigation Program by the Bangladesh Council of Scientific and Industrial Research in collaboration with the Ontario Centre for Environmental Technology Advancement, Canada. Generic and technology-specific test protocols consistent with environmental and operative conditions in Bangladesh have been developed for this verification program. The program has thus far completed verification of five arsenic removal technologies in Phase I (BCSIR 2003). An additional 14 technologies are pending for verification in Phase II of the program.

Verification of some technologies in Bangladesh shows that their performance is very much dependent on pH, and the presence of phosphate and silica in natural groundwater. Most of the technologies do not meet the claims of the proponents concerning treatment capacity. A reduction in the rated capacity will further increase the cost of treatment per unit volume of water. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Sludge Disposal Since arsenic cannot be destroyed all arsenic treatment technologies ultimately concentrate arsenic in sorption media, sludge, or liquid media. A variety of arsenic-rich solids and semisolids, such as arsenic-saturated hydrous ferric or aluminium oxides and other filter media, are generated from arsenic removal processes. Regeneration of activated alumina and ion exchange resins results in various liquid wastes that may be acidic, caustic, saline, and too arsenic rich for simple disposal. Hence, environmentally safe disposal of sludge, saturated media, and liquid wastes rich in arsenic is a concern.

The EPA has developed a toxic characteristic leaching procedure (TCLP) test to identify wastes likely to leach toxic chemicals into groundwater. The permissible level for TCLP leachate is generally 100 times higher than the maximum contaminant level in drinking water, for example 5,000 µg L for leached arsenic when the acceptable level in drinking water is 50 µg L. Sludge leaching more that 5,000 µg L of arsenic would be considered hazardous and would require disposal in a special hazardous waste landfill. The TCLP test was conducted on different types of wastes collected from arsenic treatment units and materials in Bangladesh (Eriksen-Hamel and Zinia 2001; Ali and others 2003). It has been observed that in almost all cases arsenic leaching was very minor. Arsenic leaching tests were conducted at the BUET using different extraction fluids. For all extractants arsenic concentration in the column effluents was initially very high, but then dropped sharply (Ali and others 2003). Several researchers also conducted TCLP tests on sludge resulting from arsenic removal with aluminium and ferric salts and found arsenic in leachate in the range of 9–1,500 µg L (Brewster 1992; Chen and others 1999). These arsenic levels in leachate are well below the level required for classification as hazardous wastes. It appears that most sludge would not be considered hazardous even if the WHO guideline value of 10 µg L-1 for arsenic in drinking water were considered.

Hazardous wastes are often blended into stable waste or engineering materials such as glass, brick, concrete, or cement block. There is a possibility of air pollution or water pollution downstream of kilns burning brick containing arsenic-contaminated sludge due to volatilization of arsenic during burning at high temperatures. In Hungary experiments showed that some 30% of arsenic in the coagulated sludge was lost to atmosphere in this way (Johnston, Heijnen, and Wurzel 2000). Sludge or spent filter media with low arsenic content can be disposed of on land or in landfills without significant increase in the background concentration of arsenic. Wastes with high concentration of arsenic may need solidification or confinement before final disposal.

Costs The cost of arsenic removal technology is an important factor for its adoption and sustainable use in rural areas. The cost of the technologies depends on many factors such as the materials used for fabrication of components, quantity of media or chemicals used, and quality of groundwater.

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Most of the technologies have been installed and are being operated under field testing and pilot- scale operations. Hence the costs of installation, operation, and maintenance of all the arsenic removal systems are not known or are yet to be standardized based on modifications to suit the local conditions. The available costs and system capacities of some arsenic removal technologies are presented in tables 2 and 3. The costs of alternative water supply systems are presented in table 7.

The unit costs of water produced by different water supply systems to meet present service levels have been calculated on the basis of annualized capital recovery using an annual interest rate of 12% (table 8). It has been assumed that the arsenic-safe water required per family for drinking and cooking is 45 L/day. However, the water production capacity of most alternative water supply systems is much higher than this and can serve additional users, or provide existing users with more water for all household purposes. If the full water production capacities of these systems are utilized the cost per unit volume of water is greatly reduced.

200 201 Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 8. Cost of Water Supply Options for Arsenic Mitigation

Technology Tech life Annualized Operation & Water output Unit cost (years) capital maintenance (m3) (US$/m3) recovery (US$)a cost/year (US$)

Alternative water supply: Rainwater harvesting 15 30 5 16.4 2.134 Deep tubewell 20 120 4 820 0.151 4,500 0.028b Pond sand filter 15 117 15 820 0.161 2,000 0.066b Dug or ring well 25 102 3 410 0.256 1,456 0.072b Conventional 20 2,008 3,000 16,400 0.305 treatment Piped water 20 5,872 800 16,400 0.375 73,000 0.084b Arsenic treatment (households) based on: Coagulation-filtration 3 3 25 16.4 1.70 Iron-coated sand/ 6 0.9 11 16.4 0.73 brick dust Iron filings 5 3 1 16.4 0.24 Synthetic media 5 1.2 29 16.4 1.84 Activated alumina 4 3.2 36 16.4 2.39 Arsenic treatment (community) based on: Coagulation-filtration 10 44 250 246 1.21 Granulated ferric 10–15 500–600 450–500 820–900 1.20 hydroxide/oxide Activated alumina 10–15 30–125 500–520 164–200 3.20 Ion exchange 10 50 35 25 3.40 Reverse osmosis 10 440 780 328 3.72 As-Fe removal (air 20 32,000 7,500 730,000 0.054 oxidation-filtration) a The capital recovery/amortization factor has been calculated using the formula: (1 + i)N where i = interest rate and N = number of years. ((1 + i)N -1) / i b Development of full potential of the system.

Paper 3 Arsenic Mitigation Technologies in South and East Asia Volume II Technical Report Towards a More Effective Operational Response

6. Conclusions

he problem of treatment of arsenic-contaminated water arises from the requirement for its Tremoval to very low levels to meet the stringent drinking water quality standards and guideline values for arsenic. Arsenic removal technologies have improved significantly over the last few years but many of the technologies do not work satisfactorily for natural groundwater. Reliable, cost-effective, and sustainable treatment technologies are yet to be identified and further developed. All the technologies have their strengths and weaknesses and are being refined to accommodate rural conditions. Modifications based on pilot-scale implementation of the technologies are in progress with the objectives of:

• Improving efficiency of arsenic removal • Reducing capital and operation cost of the systems • Making the technology user friendly • Overcoming maintenance problems • Resolving sludge and arsenic concentrates management problems.

Because of the cost and operational complexity of arsenic removal technologies, alternative water supply options are often given preference in arsenic mitigation. Surface water of desirable quality is not always available for low-cost water supply, while the cost of treatment of surface water using conventional coagulation-sedimentation-filtration and disinfection processes is very high. Rainwater harvesting as a household option is also costly. Dug wells do not produce or maintain water of desirable quality in all locations and are difficult to construct in some areas.

The technologies are site specific and there are various considerations for selection of a particular technology in any given locality. Some of the important considerations for the development of sustainable water supply options for purposes of arsenic mitigation are:

• The profile of the beneficiaries and settlement pattern • Present water supply system and level of arsenic in the drinking water • Possible alternative sources of water for water supply 202 203 • Relative risk and cost of development of water supply system • The level of technical and managerial capacity building needed • Affordability and willingness to pay.

A lot of effort has been spent developing the performance of arsenic field test kits. Although the accuracy of arsenic detection and measurement by field test kits is not fully satisfactory, it is a convenient tool for testing water in rural areas. Field test kits are being widely used and will continue to be used in the near future until a network of in-country laboratories is established for testing arsenic at a reasonable cost. It is therefore essential to improve the performance of the field test kits and implement quality assurance programs for field-based measurement with back-up support from available in-country laboratories to meet the present need. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

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Paper 3 Arsenic Mitigation Technologies in South and East Asia VOL II TECHNICAL REPORT Paper 4 The Economics of Arsenic Mitigation

This paper was prepared by Dr. Phoebe Koundouri of Reading University and University College London, acting in her capacity as a private consultant. University of Reading and University College London are not responsible for the contents of this document. Additional contributions were made by Karin Kemper, Amal Talbi, and Mona Sur. VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Summary

1. This paper introduces an approach that provides a quick and readily applicable method for performing a cost-benefit analysis of different arsenic mitigation policies. In particular, our suggested approach estimates benefits of mitigation activities as the sum of forgone medical costs and saved output productivity achieved by reducing arsenic exposure. The present value of these benefits is then compared with the present value of costs of various mitigation measures in order to investigate when and which mitigation policies pass a cost- benefit analysis (that is, produce a positive change in social welfare).

2. The paper applies this approach in order to provide some estimate of costs and benefits of arsenic mitigation in one case study country: Bangladesh. This case study serves as an applied example of such rapid socioeconomic evaluation and is also used as a basis for discussing trade-offs in decisionmaking with respect to the allocation of financial resources. Our approach is applicable to both cases: (a) the risk that arsenic might be found in an area where a project is planned; and (b) approaches in regard to risk mitigation options where a project aims at arsenic mitigation per se.

3. Our case study showed that for the case of Bangladesh the cost-benefit ratios for many relevant mitigation techniques and policies are positive under varying levels of success in terms of their effectiveness. These results indicate the imminent need for facing the arsenic crisis in Bangladesh, but also the clarity with which our approach can answer the difficult question on the balance of relevant costs and benefits of various mitigation options and policies.

210 211

Paper 4 The Economics of Arsenic Mitigation VOL II TECHNICAL REPORT Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

1. The Issue

Aims of This Paper his paper reviews existing studies and data on arsenic mitigation in those countries where it Thas been undertaken, and the costs of achieving such mitigation. Then these costs are compared with relevant benefits, while taking into consideration the limited knowledge base regarding the epidemiology of arsenic in the region. Discussion of the different limits for arsenic in drinking water in different countries and simulation of cost implications from implementing each limit, as well as the trade-offs between different water sources (ground or surface water, for example) in a range of socioeconomic circumstances, is central to the paper.

All decisions imply a money value of benefits, while policies can only be accepted or rejected. If a policy costs $X, accepting and implementing it implies that benefits exceed $X. Rejecting the policy implies that benefits are less than $X. Hence, there is no escape from monetary valuation. This paper provides a general introduction to the way of thinking about costs and benefits of mitigating (natural) pollutants, including considerations of trade-offs in decisionmaking with respect to the allocation of financial resources in a budget-constrained environment.

In particular, a methodology is suggested for analyzing options in order to choose between different approaches in dealing with (a) the risk that arsenic might be found in an area where a project is planned; and (b) approaches to risk mitigation options where a project’s goal is arsenic mitigation per se.

The paper also provides decisionmakers and project managers with an efficient and readily applicable methodology for rapid assessment of the socioeconomic desirability of different arsenic mitigation policies under various scenarios. The proper way of deciding whether to implement a particular mitigation policy involves conducting a cost-benefit analysis (CBA), which in turn involves (a) consideration of several different policy options to test costs and benefits of each; (b) a general equilibrium approach to the costs of a policy; (c) behavioral studies of water user responses to different levels of mitigation; and (d) behavioral studies of user responses to 212 213 nonavailability of contaminated water, especially substitution with other sources of water. The true compliance cost of any arsenic mitigation policy is unknown but some estimated figures can be used. However, we do not know the full behavioral reactions to different possible mitigation policies.

An alternative, equally ideal model on which decisionmaking could be based involves (a) estimation of changes in levels of exposure; (b) exposure-response functions linking levels to human mortality, human morbidity, and ecosystems and species; (c) willingness to pay for measures that avoid impacts identified in exposure-response relationships; and (d) allocation of benefits and costs to time periods (years). Such a procedure for estimating health benefits is more tractable than a CBA, but remains very difficult due to the absence of (a) a behavioral model of the economic sectors that use arsenic-contaminated water; (b) knowledge of change in exposure; (c) knowledge of exposure-response functions; and (d) internalization assumptions for occupational effects.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

In the absence of a full study (because of missing information and prevailing uncertainties) and given the millions of people around the world who are currently menaced by arsenic poisoning, health policymakers need to devise policies capable of counteracting this threat based on an "nth best" approach. One method of analysis would be a cohort study, selecting control (no intervention) and intervention villages (with implementation of mitigation methods) and tracking the effects of the disease on people’s health and livelihood, including coping mechanisms, over some period of time. Any study method using real populations would, however, only provide results after long periods, which limits this method’s applicability to the immediate public health concern. In addition, it is questionable whether long-term cohort follow-up would be achieved in a country where tracking of individuals is limited. Finally, ethical considerations would preclude such studies as soon as it becomes apparent that mitigation methods do work and provide relief.

Our suggested approach attempts to estimate the medical costs and forgone productivity from specific diseases or health end states. The paper applies this approach in order to provide some estimate of costs and benefits of arsenic mitigation in one case study country, namely Bangladesh. Of the regions of the world with groundwater arsenic problems Bangladesh is the worst case that has been identified, with some 35 million people thought to be drinking groundwater containing arsenic at concentrations greater than 50 µg L-1 and around 57 million drinking water with more than 10 µg L-1 (see, Paper 1 of this report). The large scale of the problem reflects the large area of affected aquifers, the high dependence of Bangladeshis on groundwater for potable supply, and the large population accumulated in the fertile lowlands of the Bengal Basin. Today, there are an estimated 11 million tubewells in Bangladesh serving a population of around 130 million people. The scale of arsenic contamination in Bangladesh means that it has received by far the greatest attention in terms of groundwater testing and more is known about the arsenic distribution in the aquifers than in any other country in Asia (as well as most of the developed world). However, much more testing is still required. Our Bangladeshi case study serves as an applied example of such a rapid socioeconomic evaluation and will also be used as a basis for discussing trade-offs in decisionmaking with respect to the allocation of financial resources. 214 215

Situational Analysis Groundwater is a significant source of drinking water in many parts of the world. Well-protected groundwater is safer in terms of microbiological quality than water from open dug wells and ponds. However, groundwater is notoriously prone to chemical and other types of contamination from natural sources or anthropogenic activities. One of these is contamination caused by high concentration levels of arsenic in water. Arsenic is a chemical that is widely distributed in nature and principally occurs in the form of inorganic or organic compounds.

The available treatment technologies for arsenic removal provide varying results depending on the concentration of arsenic in the water, the chemical composition of the water (including interfering particles), and the amount of water to be treated. Another important consideration is the feasibility and cost of the treatment process. The most commonly used biophysical methods Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

are coagulation, softening, iron and manganese oxidation, anion exchange, activated alumina membrane processes, and electrodialysis. The frequently prohibitive cost of these technologies in rural contexts has prompted the search for alternative sources of arsenic-free water, such as rainwater harvesting.

Reliable data on exposure and health effects are rarely available, but it is clear that there are many countries in the world where arsenic in drinking water has been detected at concentrations greater than the WHO guideline value of 10 µg L-1, or the prevailing national standard. These include Argentina, Chile, Japan, Mexico, New Zealand, the Philippines, the United States of America, and some countries in South and East Asia, as described in detail in Paper 1.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

2. An Ideal Approach to Evaluation of Arsenic Mitigation Measures

n order to show what is necessary for a proper evaluation of arsenic mitigation measures this Ichapter lays out an "ideal" approach – one based on a conceptually sound model, but which as a function of its assumptions has certain limitations. This permits us to judge the gap between what should be done and what can be done in practice.

Uncertainty and the Ideal Approach One misconception needs to be dispelled at the outset. One of the criticisms of economic (cost-benefit) approaches to policy evaluation is that they add to the uncertainty associated with evaluation. As such, it is argued, the approaches are best not adopted in the first place. There are indeed uncertainties, and often significant uncertainties, in cost-benefit appraisal. The problem is that the uncertainty is not reduced through nonadoption of cost-benefit analysis (CBA). Invariably, uncertainty is actually increased when CBA is not used. There are many reasons for this conclusion, but two will suffice.

First, what CBA does is to compare benefits and costs in the same units (money).1 This permits a decision of whether or not to adopt the policy at all. Adoption follows if benefits exceed costs and not otherwise. Failure to monetize benefits means that the choice context is one of cost- effectiveness in which costs are in money units but effectiveness is in a different unit, for example some notion of risk reduction (such as lives saved). However, cost-effectiveness can only rank alternative policies; it cannot say whether anything should be done. We may, for example, choose policy A over B because A secures more risk reduction per dollar than B. Nevertheless, both A and B could still fail cost-benefit tests, indicating that neither should be undertaken. Thus, a failure to adopt CBA increases risk because a new risk emerges, namely that incorrect policies are adopted.

Second, the risk reduction in question will show up in various ways. On the simplest level it may 216 217 manifest itself in reduced mortality and reduced morbidity. Cost-effectiveness analysis cannot now be conducted unless we have some idea of the relative importance of reducing one form of risk over another form of risk. Relative importance is measured by a set of weights, such that the ratio of the weights on any two forms of risk reduction reflects the relative importance of reducing one risk compared to another. If weights are not adopted, it is not possible to make any comparison between options, and rational decisionmaking is not possible. All decision analysis involves one means or another of selecting weights: by implied political preference, overt expert judgments, or, in the case of CBA, individuals’ willingness to pay for one change compared to

1 This simple observation also explains why one cannot logically avoid monetization. First, all policies have costs. If they did not have costs, there would be no need to consider whether or not they are “good” policies. Hence the acceptance of a policy implies that benefits must exceed costs, which sets a lower bound on the scale of monetary benefits. If the policy is rejected, the reverse applies. Second, costs are measured in monetary terms and few people have difficulty in agreeing that this is the correct way to measure costs. But costs are simply negative benefits, since all costs are properly measured by the forgone benefits of spending money on the chosen project rather than on something else. So, positive money costs are the same thing as negative money benefits. It follows that benefits must also be expressible in monetary units. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

another. In short, CBA’s weights are prices. Compared to a situation in which there is no knowledge of weights at all, CBA reduces uncertainty and does not increase it. It then becomes an issue of which set of weights is preferable. One advantage of CBA weights (prices) is that they reflect the preferences of those exposed to risk, and are hence more democratic than expert weights.2

An Ideal Model

The ideal approach to measuring the social benefits and costs of arsenic mitigation would be as follows.

First, some assessment would need to be made of the extent to which the selected mitigation strategy will reduce human and environmental exposure to arsenic contamination. Refer to this change as ∆X where X refers to exposure. This stage of the analysis would therefore produce the policy effect on exposure.

Second, we need an exposure-response relationship. Two effects can be identified. The first is the effect on human health, call this ∆H. Again, there will be many different health effects, ranging from reduced premature mortality to changes in, for example, hospital admissions and days away from work. Therefore, ∆H is a vector. It is helpful to divide human health effects into ∆ ∆ reduced occupational risks ( HO) and reduced public health risks ( HP). This is because there may be differences in the way the two effects are to be valued in monetary terms. The second effect is the environmental impact on ecosystems and biodiversity. Call this ∆E. Then, the sum of ∆ ∆ ∆ ∆ the effects is HO + HP + E = I where I is overall impact.

Third, we need economic values for each impact since it is implicit in the equation for ∆I that the effects are expressed in the same units. We refer to these as the shadow prices because they are the prices that would be attached to the reduced risk if there were an overt market for risk reduction. These shadow prices reflect individuals’ willingness to pay for avoiding the ill health or negative environmental impact associated with arsenic. Again there will be a whole set of shadow prices covering all of the impacts. We refer to these shadow prices as P and they are formally equivalent to the weights discussed in next section.

Fourth, we need to know when in time the changes in exposure will occur. This is because future changes in exposure will be valued less than near-term changes in exposure. The economic

2 It could be argued that political weights are best of all since politicians are elected to make such decisions. Unfortunately, the political model underlying this view is naïve, and assumes politicians always act in the best interests of voters. Moreover, techniques such as CBA are designed as checks on political decisionmaking; this is the purpose of policy analysis.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

concept that reflects the different weights attached to time is known as a discount factor. The process of attaching weights to time is known as discounting. The discount factor (DF) is linked to the discount rate(s) (expressed as an interest rate; that is, in percentage terms) as shown in equation 1:

Equation 1. Discount Factor 1 DF = (1 + s)t Where t = time (years from the present).3

Timing is important, however; not all mitigation measures can predict the exact timing of exposure reduction. For example the regulator or policymaker, in a situation where a village’s groundwater resources are contaminated, can decide to introduce piped arsenic-free water supply. Exposure to arsenic will be reduced at the moment piped water supply is introduced, if the regulator can effectively monitor that the inhabitants of the village do not continue to use other contaminated groundwater sources. Monitoring of abstraction activities is difficult, time consuming, and hence expensive, especially when areas are heavily populated. As a result monitoring will have to be coupled with an attempt to increase social awareness of the adverse effects of using contaminated water (for example through an educational campaign). An educational campaign, however, will be costly and a medium-term measure. Overall, even for mitigation measures as drastic as introducing another source of water, the timing of reduction exposure is not as evident as might be imagined.

Moreover, if a regulator is interested in restricting groundwater abstraction in order to reduce the possible anthropogenic impacts of pumping on groundwater contamination, then the exact timing of the contribution of this measure to exposure reduction (and possibly the timing of reintroducing groundwater as a water source) becomes even more difficult to identify. The significant impacts of pumping on groundwater flow may result in medium-term or long-term changes in the aquifer 218 219 systems (see Paper 1 of this report). Not only is it difficult to quantify these impacts, both with regards to their time and space dimension, but it is also necessary to be aware of the various dimensions of the potential human influences. These include the impacts of pumping-induced flow on transport of arsenic both within and between aquifers, impact of pollutants such as organic carbon and phosphate on aquifer redox and sorption or desorption, and impact of seasonal waterlogging of soils for rice production on subsurface redox conditions.

Fifth, we need to know where the exposure changes occur. For example, if they occur in heavily populated areas the benefits of risk reductions will be higher. Environmental effects are even more location specific.

3 Space precludes further discussion of discounting. It should be noted that it is not possible to avoid discounting. Not discounting is formally equivalent to discounting at 0%. Unfortunately, zero discounting has logical implications that make it undesirable, however reasonable it may at first appear (Koundouri and others 2002). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The ideal model can now be summarized as follows. The benefits that ensue from arsenic mitigation are given by equation 2.4

Equation 2. Ideal Model of Benefits Ensuing from Arsenic Mitigation ∆ ∆ Σ Ii,t( Xt ) PV (B) = i,t (1 + s)t Where: i = the individual impacts PV(B) = the present value of benefits from arsenic mitigation and is the value that would be compared to the present value of costs.

A particular mitigation option would pass a cost-benefit test if PV(B) > PV(C) (present value of costs), as shown in equation 3.

Equation 3. Mitigation Option Passing a Cost-Benefit Test ∆ ∆ Σ Ii,t( Xt ) PV (B – C) = i,t PV (Costs) > 0 (1 + s)t

Notice that the situation in equation 3 could be met overall in a country but a particular mitigation option could fail in any one region of the country. Similarly, a mitigation policy could fail a cost- benefit test at the country level, but pass it in a given region.

Problems with the Ideal Model Models of the kind shown in equation 3 have been used fairly extensively for such air pollutants as sulfur and nitrogen oxides, particulate matter, and volatile organic compounds (Olsthoorn and others 1999; Krewitt and others 1999). These models make use of long-established emission- diffusion-deposition models (such as RAINS Europe), which also contain measurable ecosystem impacts based on notions of critical loads.5 They also have established exposure-response relationships for human health. The policies that are simulated also have known, or reasonably known, time schedules over which the pollutants are reduced. Finally, they utilize economic values per effect based on longstanding work under the ExternE program of DGXII in the European Commission.

The contrast with what is known about arsenic pollution is a stark one. In order to be able to provide an overall policy-level model that will be able to measure the social benefits and costs of

4 Equation 2 ignores location for convenience of exposition, but it will be appreciated that benefits and costs vary by location. 5 A critical load is the maximum level of deposition of airborne pollutants that produces no discernible change in the receiving ecosystem. Above this level, some form of ecological damage occurs. Note that critical loads relate solely to ecosystems and not to health effects. A critical level would be that ambient concentration that produced no discernible change in, for example, human health, materials corrosion, or crop loss.

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arsenic mitigation one would need to know the following (and unfortunately we do not):

• The effects of mitigation activities on exposure (∆X), since this is dependent on the behavioral reaction of producers, users, and regulators to (a) the changes in information generated by arsenic mitigation efforts and relevant educational campaigns; and (b) the costs of regulation. Put another way, we have no economic model of the relevant economy – including all users – with which to simulate the effects of any policy change.

• The health and environmental exposure-response functions (∆I(∆X)) for arsenic pollution, of which, in any event, there are many thousands.

• The locations at which risks will change.

• The split between occupational and public health effects.

• The time schedule of ∆X, although some assumption could be made about this.

We do have some economic values for health end states, but valuation of environmental effects would not be possible since we have no idea of the end states of the changes in, for example, groundwater flows (both in terms of quantity and quality).

We conclude that it is not possible to approximate the ideal model in the case of arsenic mitigation. The information is simply not available. After recognizing that we have to move away from the first-best world of full information and certainty, in the next section we develop a so- called nth best model, which allows approximation of the costs and benefits of arsenic mitigation, but does not claim to be an exact representation (model) of the actual situation. The reasons for the need to have an approximate rather than an accurate model have been explained in this section and need to be taken very seriously by any policymaker who would choose to make use of this paper. This paper should be thought of as providing guidance on the methodological approach that one should use when contemplating the economic costs and 220 221 benefits of different arsenic mitigation policies. However, the empirical application of the suggested methodological approach should be treated with great caution and results should be read as case study specific, derived under conditions of severe information scarcity and pervasive uncertainty, with regards both to the human and physical reactions to implementable mitigation policies.

The merit of our methodological approach compared to an approach attempting to implement the first-best (ideal) model, is that it explicitly accepts, identifies, and characterizes the heroic assumptions made in the evaluation process. We hope that this feature of the proposed nth best model will act as a constant reminder of the pervasive uncertainties and incomplete information that prevail in arsenic mitigation policies. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

The Nth Best Model Given the circumstances, we have to proceed in a far more ad hoc way.

The first thing to do is to invert equation 3 and find out just how large the benefits need to be for a particular arsenic mitigation policy to pass a cost-benefit test. We do this for health effects only since we cannot estimate environmental effects. This procedure gives us a benchmark. If health benefits exceed this level then we know that the particular policy comfortably passes a cost- benefit test. We also have a minimum estimate of benefits since environmental effects are not calculated and these unknown benefits would need to be added.

Second, we need some crude ways in which benefits can be estimated given certain assumptions. Water intended for human consumption should be both safe and wholesome. This has been defined as water that is free from pathogenic agents, free from harmful chemical substances, pleasant to taste, free from color and odor, and usable for domestic purposes (Park 1997). Without ample safe drinking water, communities cannot be healthy.

Cvjetanovic (1986) reviews the various mechanisms by which the provision of safe water supply is transformed into health benefits. His conceptual framework shows that an investment in water supply and sanitation results in an improvement in the quantity and/or quality of water available to the household. This yields direct health benefits resulting from improved nutrition, personal hygiene, and the interruption of water-related disease. Moreover, the health benefits from reducing water-related disease can in some circumstances translate into greater work capacity, which may contribute to increased production and hence to overall economic development. According to Becker (1971, 1981), the household uses time, labor, and purchased goods to create commodities for the household. The household attempts to produce safe water for consumption, which is dependent on time and resource constraints. Safe water for household use is dependent on the time and labor used in the collection of water, the time and resources used to boil or sterilize the water, and managing water within the household. Households may not have access to safe water supplies because the financial, labor, or time and energy costs of collection and management are too high, either at a given point in time or perpetually.

The provision of a local safe water supply source is likely to considerably reduce the burden of producing safe water for the household. The labor cost of collecting water is borne largely by women and girls, who are responsible for domestic chores in most developing countries. It has been found in Kenya that carrying water may account for up to 85% of total daily energy intake of females (Dufaut 1990). While this is not currently the case everywhere in South and East Asia, if arsenic mitigation activities imply switching wells to a safe well, which might be located at a significant distance from the house, then it may mean that even in these countries women have to walk long distances for water. A number of physical ailments may result from carrying heavy loads, including head, neck, and spinal problems (Dufaut 1990). Clearly there is considerable

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health benefit to be gained from decreasing women’s weight-bearing responsibilities. In addition, Krishna (1990) points to the indirect health benefits that may be gained from mothers having greater time to spend on childcare. The extent of benefit is related to service level (proximity to point of use) and to reliability.

All of these health benefits should be seriously considered in a CBA of various potential mitigation measures, especially when mitigation measures are likely to deprive women of these health benefits. That is, due consideration should be paid to the incentives that various mitigation measures create for the people, which will to a large extent define the acceptability and effectiveness of the measures. If a mitigation measure is too costly in terms of time and adverse health effects then implementation will be difficult and monitoring very expensive, if it is possible at all.

Access to safe water will also depend on nonmaterial factors, such as basic hygiene knowledge, social position, and water quality. Basic hygiene knowledge and high water quality facilitate access to safe water. It is said that these factors alter the efficiency of the household as a safe water producer. Social factors affecting access to water supply sources will also determine the ability of the household to produce safe water. Lower-caste households may not have access to high-quality water supply sources due to cultural norms, which embrace principles of social exclusion. Conversely, higher-caste households may be unwilling to share high-quality water supply sources with lower-caste households, which instead may choose alternative sources of lower-quality water. In other social contexts, the effects on higher castes may be adverse, for example if they are socially excluded from water sources used by lower castes.

A model for calculating these benefits is developed in chapter 4. Our model, however, takes into account only some of the identified health benefits and occupational benefits. Other social benefits, such as those outlined in the last three paragraphs of this section, are not included in the application of our model due to the lack of relevant information. In the case that such relevant estimates exist, our model is flexible enough to accommodate such benefits. 222 223 Is Passing a Cost-Benefit Test Sufficient? The requirement that benefits be greater than costs is not sufficient for a policymaker to sanction investment in a particular project. We can say that a cost-benefit ratio >1 is a necessary condition for approval of a project, but is not a sufficient condition for its approval. This is because every government invariably faces a limited budget and cannot undertake all projects where social benefits exceed social costs. We therefore require a procedure to rank different projects. It is tempting simply to rank them using the net present value of benefits, but this is actually a mistake. This is easily demonstrated by table 1. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 1. Ranking of Projects

Project PV PV NPV PV (benefits)/ (costs)a (benefits) (benefits)b PV (costs)

X 100 200 100 2.0 Y 50 110 60 2.2 Z 50 120 70 2.4 a. PV = present value. b. NPV = net present value.

This shows three projects, X, Y, and Z, with the present value (PV) of their benefits, costs, and net benefits. Suppose the budget constraint is 100 units. Then a ranking by NPV (benefits) would suggest X, Z, Y and we would undertake X only with a cost of 100. The gain to society would be NPV(X) = 100. But casual inspection shows that we could afford Y and Z, and the NPV would be NPV(Y) + NPV(Z) = 60 + 70 = 130. Clearly, ranking by NPV does not give us the right answer. This is given by a ranking of PV (benefits) divided by PV (costs), or the so-called benefit-cost ratio.

The above discussion points to an additional consideration: that one should try to develop a clear picture of how arsenic mitigation interventions figure in the overall water and sanitation sector and in the broader economy of a country. For example, interventions in sanitation that would drastically reduce diarrhea and infant mortality rates might be another way of achieving significant social benefits in a developing country such as Bangladesh. Alternatively, perhaps investing in education and transport infrastructure or investing in other sectors of the economy would produce higher social net present value. Given the different potential social welfare- increasing projects, the policymaker should rank them according to the cost-benefit ratios associated with each one, as discussed above.

It should be noted, however, that the ability to perform such a ranking exercise depends on the availability of CBAs for all potential investments, which is an expensive endeavor. Developing countries will not have the means to accommodate such an expensive and holistic exercise; however, they should implement this exercise for policies when possible to prioritize projects. Prioritization will reflect ethical judgments within the country, or binding constraints imposed by the national or international political and policy arena.

Another point to note, and one which was touched upon in this section of this paper, is that when embarking on such CBA one should be aware of the long-run effects of proposed projects and mitigation measures. In the calculation of present values of costs and benefits of public sector projects and policies, future values are multiplied by a discount factor that is calculated from the

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social discount rate (social time preference rate). However, at even a modest rate, the practice of discounting reduces the value of costs or benefits for long periods of time (many years) and hence almost to zero. This disenfranchizes future generations from consideration in today’s decisions. Recent work on discounting over the long term has now made it clear that constant rate discounting has only a limited justification, and that it is possible to make recommendations for better practice (Koundouri and others 2002; Pearce and others 2003). The recent literature argues that discount rates vary with time and that, in general, they decline as the time horizon increases.6 The effects of declining discount rates on the appraisal of relatively long-term government policies, programs, and projects can be summarized as follows:

• Is small over a short (for example 30-year) period, but large over a very long period

• Can influence the choice of a policy or project

• Does not always support the option perceived as best for the environment

• Can affect financial planning, in both public and private sectors

• May result in reevaluation of hurdle cost-benefit ratios or budgets in the public sector

Finally, one should keep in mind that economic policy is about making comparisons of the economic situation, which requires knowledge about the desirability of the change that an action seeks to bring about. In the real world, choices lead to gains by some and losses by others. To avoid making value judgments in this context, a number of compensation tests have been devised in an effort to find a basis to compare states that is founded on efficiency.7 However, attempts to devise a criterion based solely on efficiency, and without resort to ethical judgments, are simply not available and economists’ policy recommendations are controversial.

224 225

6 There are several strands to the arguments in favor of declining long-run interest rates. The first set of arguments derives from empirical observations of how people actually discount the future. There is some evidence that individuals’ time preference rates are not constant over time, but decrease with time. Individuals are observed to discount values in the near future at a higher rate than values in the distant future. While some evidence still supports time-constant discount rates, the balance of the empirical literature suggests that discount rates decline in a hyperbolic fashion with time. The second set of arguments in favor of time-varying discount rates derives from uncertainty about economic magnitudes. Two parameters have been selected for the main focus of this approach. The first is the discount rate itself. The argument is that uncertainty about the social weight to be attached to future costs and benefits – the discount factor – produces a certainty-equivalent discount rate, which will generally decline over time. The second uncertain parameter is the future state of the economy as embodied in uncertainty about future consumption levels. Under certain assumptions, this form of uncertainty also produces a time-declining discount rate. The third set of arguments for time-declining discount rates does not derive from empirical observation or from uncertainty. Instead, this approach – the “social choice” approach – directly addresses the concerns of many that constant-rate discounting shifts unfair burdens of social cost onto future generations. It adopts specific assumptions (axioms) about what a reasonable and fair balance of interests would be between current and future generations, and then shows that this balance can be brought about by a time-declining discount rate. Any one, or all, of these three lines of arguments supports the hypothesis that the social time preference rate decline with time. Moreover, there have been a number of attempts to construct models to quantify the shape of this decline and, in some cases, to test them empirically. 7 An excellent discussion of compensation tests can be found in Chipman and Moore 1978. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

3. The Cost of Arsenic Mitigation Measures: Review of Possible Actions

s indicated in chapter 2, the CBA undertaken in this paper will only take into account some Aof the health-related costs of arsenic contamination and resulting occupational hazards. These costs will translate into benefits if avoided through the implementation of effective mitigation measures. Hence, in order to derive the cost-benefit ratio of the different mitigation measures these benefits should be compared with the costs of the relevant mitigation measures. These costs and benefits are described in this chapter.

Health Effects of Arsenic in Drinking Water The World Health Organization (WHO) recommendations on the acceptability and safety of levels of arsenic in drinking water have dropped twentyfold from a concentration of 200 µg L-1 in 1958 to 10 µg L-1 in its 1993 Drinking Water Guidelines. However, some countries are still using the former WHO standard of 50 µg L-1. For example, the Bangladesh Standards for Testing Institution sets the maximum permissible limit for arsenic at this former level.

Differences in standards derive partly from the fact that there is no widely accepted complete definition of what constitutes arsenicosis. Inorganic arsenic is a classified carcinogen (IARC 1980) that also has a multitude of noncancer effects. The widespread effects of arsenic are perhaps responsible in part for the lack of a widely accepted care definition for arsenicosis. Furthermore, some symptoms of arsenicosis (such as shortness of breath) may be observationally indistinguishable from the health effects of other illnesses. A comprehensive review of the health effects of arsenic contamination of drinking water is undertaken in Paper 2 of this report. The purpose of this section is to highlight some of the main findings of the literature on health effects, especially with respect to predictive use of the available information. In addition, arsenic poisoning may be acute or chronic. In the context of community drinking water supply, only chronic exposure is relevant. Acute poisoning is therefore not discussed further.

According to the United States National Research Council report (NRC 1999, p. 89), the most widely noted noncancer effect of chronic arsenic consumption is skin lesions. Over time, arsenic exposure is associated with keratoses on the hands and feet. The time from exposure to manifestation is debated in the literature, while the youngest age reported for patients with hyperpigmentation and keratosis is two years of age (Rosenberg 1974). In Bangladesh, Guha Mazumder and others (1998) suggest a minimum time gap of five years between first exposure and initial manifestations.

Cancer Health Effects8 Hutchinson (1887) identified arsenic as a carcinogen because of the high number of skin cancers

8 Arsenic is also associated with peripheral vascular disease, which is a condition that results in gangrene in the extremities and usually occurs in conjunction with skin lesions. Other cardiovascular problems such as hypertension (Chen and others 1995) and ischemic heart disease have also been found to be associated with arsenic (Tsuda and others 1995). Moreover, Guha Mazumder and others (1998) found evidence of liver enlargement and restrictive lung disease. In terms of hematological effects, anemia is commonly cited (NRC 1999). Another widely suggested health effect is diabetes mellitus.

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occurring in patients treated with arsenicals. The International Agency for Research on Cancer (IARC 1980) classified inorganic arsenic compounds as skin and lung (via inhalation) carcinogens. In the period following this classification, concerns have grown over the possibility of arsenic in drinking water causing a number of other cancers.

An early study by Tseng and others (1968) found evidence of a dose-response relationship between concentration of arsenic in drinking water and prevalence of skin cancer. The International Program on Chemical Safety (IPCS 1981) estimated skin cancer risk from lifetime exposure to arsenic in drinking water at 5% for 200 µg L-1, based on the findings of Tseng (1977). Based on the increased incidence of skin cancer observed in the population in Taiwan, China, the United States Environmental Protection Agency (EPA 1988) has used a multistage model that is both linear and quadratic in dose to estimate the lifetime skin cancer risk associated with the ingestion of arsenic in drinking water. With this model and data on males, the concentrations of arsenic in drinking water associated with estimated excess lifetime skin cancer risks of 10-4, 10-5, and 10-6 are 1.7, 0.17, and 0.017 µg L-1 respectively. Considering other data and the fact that the concentration of arsenic in drinking water at an estimated skin cancer risk of 10-5 is below the practical quantification limit of 10 µg L-1, the provisional guideline value of 10 µg L-1 is recommended (WHO 1996). The guideline value is associated with an excess lifetime risk for skin cancer of 6 x 10-4 (that is, six persons in 10,000).

High levels of arsenic in drinking water are also associated with a number of internal cancers. However, it is difficult to quantitatively establish risk in many of the studies, due to problems in measuring exposure to arsenic. Chen and others (1985) calculated standardized mortality ratios for a number of cancers in 84 villages in Taiwan. Mortality for the period 1968-1986 was compared with age and sex-adjusted expected mortality. Significantly, increased mortality was observed among both males and females for bladder, kidney, lung, liver, and colon cancers. However, the authors were not able to directly estimate arsenic concentrations in well water. Chen and Wang (1990) were able to use data on arsenic concentrations in 83,656 wells in 314 226 227 precincts and townships collected from 1974 to 1976 in Taiwan. The authors used a multiple regression approach to control for socioeconomic confounding factors, and compared age- adjusted mortality rates with average arsenic concentrations in each township. They found a significant relationship between arsenic concentration and mortality from cancers of the liver, nasal cavity, lung, bladder, and kidney for both sexes.

The above-mentioned studies all used an ecological design and are thus susceptible to bias from confounding factors. However, the bladder and lung cancer results of these studies are also confirmed by cohort studies, which may be less susceptible to this form of bias. These studies are also useful in providing data on the latency period of internal cancers. Cuzick, Sasieni, and Evans (1992) studied a cohort of patients treated with Fowler’s solution (potassium arsenite) in England from 1945 to 1969. The authors found evidence that the period between first exposure and death from bladder cancer varied from 10 years to over 20 years. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

To conclude, the results from studies of cancer indicate strong evidence that exposure to arsenic is related to skin, lung, and bladder cancer. It is likely that arsenic causes a number of other cancers, but thus far epidemiological evidence has not been consistent for other sites in the body.

Treatment of Arsenicosis Sufferers Guha Mazumder (1996) suggested that the first stage in treating those with arsenicosis should be the immediate cessation of consumption of arsenic-contaminated water. Once this has been achieved, the emphasis should be on the provision of a diet high in protein and vitamins. The chelating agents DMPS (dimercaptopropane sulphonate) and DMSA (dimercaptosuccinic acid) are recommended as treatment drugs (Angle 1995). However, Guha Mazumder (1996) notes that these drugs are very expensive. Palliative care may be the only affordable treatment in rural areas of developing counties, where expensive drugs and protein-rich diets are unlikely to be available to the vast majority of people. In the case of keratosis, application of ointment containing salicylic acid can help to soften the skin and ease the patient’s pain.

Mitigation of Arsenic in Drinking Water This section will analyze the technologies that can be used to provide safe drinking water in rural Bangladesh, which serves as an example for most relevant mitigation options. The available options for safe water can be classified by source: groundwater, surface water, and rainwater. Recent years have seen increasing acceptance of strategies for incremental improvement in environment and health in general and of demand-driven approaches to water supply and sanitation in particular. It is inappropriate therefore to pursue a single overall technological solution but rather to inform communities and individuals of alternatives and their characteristics in order to facilitate choice of the most appropriate options.

Groundwater The simplest and most immediately achievable option is the sharing of tubewells that are currently either free from arsenic or contain very low levels. Wells containing arsenic may still be used safely for such activities as washing laundry, and a simple color coding (using, for example, "traffic light" colors) may have a significant impact on community arsenic exposure if carefully and continuously backed up by awareness raising and education. However, in the most highly contaminated areas not enough tubewells will contain safe levels of arsenic. Furthermore, color coding would have to be monitored carefully over time, as tubewells with previously safe test results may be later found to contain increased levels of arsenic. The principal costs of such an approach relate to the ongoing testing and labeling of wells and of continuous awareness raising and education. These costs may be borne by the community or by an outside agency. In practice, the household burden of water collection is likely to increase (because a greater average distance will be traveled in order to collect the same volume of water).

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For some countries, such as Bangladesh and Nepal, the other alternative for groundwater supply is the development of deep tubewells. The principal costs of such an approach relate to the costs of developing the deep tubewells. These include the costs of training and equipping drilling teams as well as the direct costs of drilling itself, including a proportion of unsuccessful bores. These costs may be borne by the community or an outside agency. If contaminated wells remain in use for other purposes such as laundering ongoing awareness raising and education will be essential. If new wells are appropriately sited then the household burden of water collection may be constant or even decrease. Deep tubewells have been in use for years in coastal areas because of high salinity in shallow aquifers. However, it is not possible to exploit this technology in all areas because rock formations may make drilling infeasible.

The Danish Agency for International Development (Danida) has conducted research in Noakhali in Bangladesh since November 1998 on the removal of arsenic using a mix of 200 µg L-1 alum and -1 1.5 µg L KMnO4 introduced into a large bucket (18 liters), of which the supernatant is drained off after 1–1.5 hours into a bucket standing beneath it. Cost of chemicals for an average family is Tk 10/US$0.2 a month. Lab tests show a reduction in arsenic levels of 1,100 µg L-1 to 16 µg L-1. In the field tests arsenic ranging from 120–450 µg L-1 was reduced to 20–40 µg L-1 consistently. Though well within the Bangladesh standard, the removal efficiency was considerably less than in the laboratory. Stirring (time, mixing efficiency – paddle stick instead of cane stick) is believed to make a difference and Danida is currently verifying this in a field test. Danida has also designed a two-bucket column (total investment cost for the set is Tk 300/US$6), which circumvents the resuspension of the settled solids. Danida reports that 50–80% of the two- bucket systems deliver water within Bangladesh standards (Danida 2000).

Coprecipitation is a well-known phenomenon and has been the subject of a small study by WaterAid in East Madaripur near Chittagong. Iron ranges from 0 to 10 µg L-1. In the first phase of the study it seemed that removal rates were very good. However, upon further study it was found that some wells showed very low removal rates. It seems that salinity has a detrimental effect on removal. Hardness may possibly have an effect as well. 228 229 The Danida and WaterAid studies also examined the sustainability of methods at the household level. Apart from initial acceptance of a suitable method, households will also have to apply the technique consistently and properly to continue to avail themselves of the benefits of arsenic avoidance.

The Pan American Center for Sanitary Engineering and Environmental Sciences (CEPIS)9 in Peru has developed a technology called ALUFLOC for arsenic removal at the household level and it has been tested in Argentina. ALUFLOC is a sachet containing chemicals that are added to a bucket of arsenic-contaminated tubewell water. After about an hour the treatment process is complete and the water is safe for consumption. Preliminary field test results suggest that ALUFLOC is effective in reducing arsenic content to safe levels. However, it is necessary to

9 CEPIS is part of the Pan American Health Organization (PAHO), the WHO Regional Office for the Americas. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

optimize the product for treating tubewell water with a concentration of arsenic greater than 1,000 µg L-1. The cost of the technology is estimated at US$0.15 per bucket treated, given the assumption of production at an industrial level. The cost of such an approach relates to the ongoing need for awareness raising and education; the cost of treatment materials (including manufacture and distribution); and the costs of additional household expenditure on equipment (such as additional buckets) and in terms of time. It may however be deployed rapidly and costs may be borne by the community or an outside agency, or may be subsidized.

Surface Water Surface water (including rainwater, rivers, lakes) is typically low in arsenic and therefore a potentially attractive source of drinking water in arsenic-rich areas. However, surface waters are frequently contaminated with human and animal fecal matter and other material and are unsafe for this reason. This risk initially led to the preference for groundwater sources in Bangladesh and other developing countries worldwide. The critical issues in arsenic-rich areas therefore concern whether treating surface water for fecal contamination can be reliably achieved at a lower overall cost than securing groundwater from low-arsenic sources or through treatment to remove arsenic from groundwater.

Surface Water Treatment Treatment of surface water can be achieved by several means. Slow sand filtration, for example, is a typical method of treatment for rural areas and small towns. The water passes slowly through a large tank filled with sand and gravel. There is some reservation about the sustainability of this method in Bangladesh. The reasons for this include the need for careful maintenance and the risk of bacteriological infection if the system is not operated properly. However, pond sand filters are still useful as an option in Bangladesh, especially in the coastal belt where there are few alternatives.

The key elements in the decisionmaking process leading to the selection of technology using surface water rather than groundwater concern the costs of capital investment in infrastructure and the cost of maintenance, including supervisory support. If wells containing arsenic remain in use, ongoing awareness raising and education will be required. The household burden of water collection is likely to increase (as the number of available sources is likely to decrease) unless the opportunity is taken to make capital investments to develop piped distribution.

Rainwater Rainwater harvesting is a recognized water technology in use in many developing countries around the world (WHO-IRC 1997). The United Nations Children’s Fund (UNICEF) has promoted dissemination of the technology since 1994 in Bangladesh. The rainwater is collected using either a sheet material rooftop and guttering or a plastic sheet and is then diverted to a storage container.

Rainwater harvesting is capital intensive and the costs (and availability) of suitable roofing, materials for guttering, and storage tanks are important factors. Rainwater use has proven to be successful in Taiwan, Sri Lanka, and Thailand.

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In some circumstances there is the possibility of chemical contamination of the collected water, particularly where air pollution is a major problem and where bacteriological contamination may be caused by bird droppings. There is also the possibility of contamination (for example intrusion of insects), particularly when the water is stored for long periods. Health inspections are needed regularly to ensure that the water is of good quality. However, these reservations might be less problematic as rainwater quality in many circumstances is at least as good as the piped water distributed in many towns in Bangladesh.

The above are only examples of technologies that might be considered as alternatives to groundwater abstraction. Other low-cost technologies that might be considered include use of springs and infiltration galleries.

In our empirical application we consider eight alternative technologies designed to provide arsenic-free water: dug wells, roof rainwater combined with dug wells for the dry season, deep tubewells, arsenic removal in existing shallow tubewells, pond sand filters, deep production wells (piped scheme), impoundment-engineered pond (piped scheme), and surface water infiltration (piped scheme).

Technology Choice The following analysis is based on Bangladesh data and naturally it will vary in different countries, due mainly to the population density, the severity of the arsenic problem, and the geographic distribution of the population. Moreover, we take into account only the rural population of Bangladesh. The technology options considered can all be applied in Bangladesh, but some of them may not be applicable in other countries. For example, in some countries deep tubewells may not be useful because the aquifer structure is such that deep tubewells may also be contaminated (see Paper 1).

The choice between these technologies should take into account their cost-effectiveness in 230 231 providing arsenic-free and microbiologically safe drinking water. Different options may have very different balances of cost between, for example, capital and recurrent costs and may impact differently on the household costs of water management. However, the criteria of sustainability and acceptance by rural users must be incorporated into the calculation of cost-effectiveness in order to aid the decisionmaking process concerning which mitigation method(s) to implement. Table 2 indicates the mitigation options for which cost evaluation is conducted.

The aforementioned technology options are evaluated for three kinds of villages: small (100 households), medium (500 households), and large (1,000 households). We further assume that each household consists of an average 5.5 members and that the distribution of income is as follows: 10% have high income, 20% have medium income, and 70% have low income. The level of service provided to each household depends on the income of the household. The high- income people will be provided water by multiple taps (one for each household), the medium- income people will have a single yard tap per two or three households, while a communal Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 2. Arsenic Mitigation Technology Options

Option no. Technology

A Dug wells B1 Roof rainwater harvesting/household (60 m2) + dug well for dry season B2 Roof rainwater harvesting/household (60 m2) + deep tubewell for dry season C Deep tubewell D Existing shallow tubewell with household arsenic removal E1 Pond sand filter E2 Pond sand filter (30 households/pond sand filter) F Piped scheme deep production well G Piped scheme impoundment-engineered pond H Piped scheme surface water infiltration gallery standpost will be provided per 10 households of low income. The distribution of income as well as the level of service is necessary for the most accurate cost estimation.

Table 3 shows the capital costs and operation and maintenance annual costs applied to a small village of 100 households.10 The most expensive technology in terms of capital costs is option B (both B1 and B2), which combines rainwater harvesting with the construction of dug wells or

Table 3. Small Village: Capital and Operation and Maintenance Costs

Technology Capital costs Operation & (US$)a maintenance costs (US$)a

A Dug wells 17,750 2,968 B1 Rainwater harvesting + dug well 33,913 3,523 B2 Rainwater harvesting + deep tubewell 35,335 2,819 C Deep tubewell 21,561 1,083 D Shallow tubewell with arsenic removal 7,966 4,237 E1 Pond sand filter 25,719 2,242 E2 Pond sand filter (30 households/unit) 3,810 332 F Deep production well, piped 19,432 3,051

G Impoundment, piped 19,432 3,390 H River abstraction, piped 17,653 3,051 a. Costs are for a small village of 100 households.

10 A detailed description of the costs involved in each technology for a village of 500 households is given in annex 1.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

deep tubewells. In terms of operation and maintenance expenses option D is the most expensive, due to the costs of the arsenic removal techniques. The level of service provided for a small village by each of the techniques is summarized in table 4.

Table 4. Small Village: Technology-Specific Level of Service

Technology No. of households per unit Total for 100 by income households High Medium Low (10%)a (20%)b (70%)c

A Dug wells 1 3 10 24 B1/2 Rainwater + dug well/tubewell 1 1 1 100 C Deep tubewell 1 3 10 24 D Shallow tubewell/arsenic removal 1 1 1 100 E1 Pond sand filter 1 2 10 27 E2 Pond sand filter (30 households/unit) 30 30 30 4 F Deep production well, piped 1 2 10 27 G Impoundment, piped 1 2 10 27 H River abstraction, piped 1 2 10 27

Type of service: a. multiple taps; b. single yard tap; c. communal standposts.

In the same mode, for a medium village of 500 households, table 5 shows the capital costs and annual operation and maintenance costs, while table 6 shows the level of service.

Table 5. Medium Village: Capital and Operation and Maintenance Costs

Technology Capital costs Operation & 232 233 (US$)a maintenance costs (US$)a

A Dug wells 88,750 14,842 B1 Rainwater harvesting + dug well 169,566 17,616 B2 Rainwater harvesting + deep tubewell 176,677 14,097 C Deep tubewell 107,803 5,415 D Shallow tubewell with arsenic removal 39,831 21,186 E1 Pond sand filter 128,593 11,212 E2 Pond sand filter (30 households/unit) 16,193 1,412 F Deep production well, piped 47,093 6,780 G Impoundment, piped 48,246 7,627 H River abstraction, piped 44,534 6,780

a. Costs are for a medium village of 500 households. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 6. Medium Village: Technology-Specific Level of Service

Technology No. of households per unit Total for 500 by income households High Medium Low (10%)a (20%)b (70%)c

A Dug wells 1 3 10 118 B1/2 Rainwater + dug well/tubewell 1 3 10 118 C Deep tubewell 1 3 10 118 D Shallow tubewell/arsenic removal 1 1 1 500 E1 Pond sand filter 1 2 10 135 E2 Pond sand filter (30 households/unit) 30 30 30 17 F Deep production well, piped 1 2 10 135 G Impoundment, piped 1 2 10 135 H River abstraction, piped 1 2 10 135

Type of service: a. multiple taps; b. single yard tap; c. communal standposts.

For a large village of 1,000 households, table 7 shows the capital costs and annual operation and maintenance costs, while table 8 (see page 234) shows the level of service.

Table 7. Large Village: Capital and Operation and Maintenance Costs

Technology Capital costs Operation & (US$)a maintenance costs (US$)a

A Dug wells 177,500 29,684 B1 Rainwater harvesting + dug well 339,131 35,232 B2 Rainwater harvesting + deep tubewell 353,355 27,178 C Deep tubewell 215,607 10,831 D Shallow tubewell with arsenic removal 79,661 42,373 E1 Pond sand filter 257,186 22,424 E2 Pond sand filter (30 households/unit) 32,386 2,824 F Deep production well, piped 87,075 9,322 G Impoundment, piped 89,075 10,508 H River abstraction, piped 85,024 9,322 a. Costs are for a large village of 1,000 households.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 8. Large Village: Technology-Specific Level of Service

Technology No. of households per unit Total for 1,000 by income households High Medium Low (10%)a (20%)b (70%)c

A Dug wells 1 3 10 237 B1/2 Rainwater + dug well/tubewell 1 3 10 1,000 C Deep tubewell 1 3 10 237 D Shallow tubewell/arsenic removal 1 1 1 1,000 E1 Pond sand filter 1 2 10 270 E2 Pond sand filter (30 households/unit) 30 30 30 34 F Deep production well, piped 1 2 10 270 G Impoundment, piped 1 2 10 270 H River abstraction, piped 1 2 10 270

Type of service: a. multiple taps; b. single yard tap; c. communal standposts.

We further conducted a present value analysis in order to identify the technology option with the lowest cost for each kind of village. Our analysis suggests that the most efficient option for small villages is option C, deep tubewells, while for medium and large villages option H, river abstraction (piped), should be employed. These options guarantee arsenic-free water. However, if we disregard the issue of the level of service, the most efficient technique is pond sand filters (30 households per pond sand filter). Special attention should be paid to avoidance of bacterial contamination of the water, as percolation of contaminated surface water is the most common route of pollution. Disinfection of the water by pot chlorination should be continued during 234 235 operation. As regards option F, the deep aquifers in Bangladesh have been found to be relatively free from arsenic contamination. The study by the British Geological Survey and the Department of Public Health Engineering (BGS and DPHE 2001) has shown that only about 1% of tubewells having a depth greater than 150 m are contaminated with arsenic at concentrations higher than 50 µg L-1 and 5% of tubewells have arsenic content above 10 µg L-1 (See Paper 1 for a more detailed analysis). The combination of deep production wells with piped water supply can ensure the provision of good quality water to people. Details for the present value of the total costs of the various techniques for each of the three sizes of village are given in tables 9, 10, and 11. The numbers in bold indicate the least costly options.

The first column of tables 9, 10, and 11 refers to a discount rate of 10% for a 10-year period, the second column to a discount rate of 10% for a 15-year period, and the third column to a discount rate of 15% for a 20-year period. These figures can be used as the basis for a sensitivity analysis, whose reasoning derives from: (a) 10–15% is the lending rate in Bangladesh; and (b) 10-20 years is a reasonable payout period given the financial market in Bangladesh. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 9. Small Villages: Present Value Analysis of Technology Costs

Technology Costs (millions US$)a DRb 10% for DRb 10% for DRb 15% for 10 years 15 years 20 years

A Dug wells 35,989 43,021 36,330 B1 Rainwater harvesting + dug well 55,561 63,908 55,966 B2 Rainwater harvesting + deep tubewell 52,660 59,339 52,984 C Deep tubewell 28,216 30,781 28,340 D Shallow tubewell with arsenic removal 34,002 44,041 34,489 E1 Pond sand filter 39,497 44,809 39,754 E2 Pond sand filter (30 households/unit) 5,851 6,638 5,890 F Deep production well, piped 38,178 45,406 38,528 G Impoundment, piped 40,261 48,292 40,650 H River abstraction, piped 36,399 43,626 36,749 a. Total costs of serving all small villages of 100 households. Figures in bold indicate least-cost options. b. DR = discount rate.

Table 10. Medium Villages: Present Value Analysis of Technology Costs

Technology Costs (millions US$)a DRb 10% for DRb 10% for DRb 15% for 10 years 15 years 20 years

A Dug wells 179,946 215,107 181,650 B1 Rainwater harvesting + dug well 277,807 319,539 279,829 B2 Rainwater harvesting + deep tubewell 263,300 296,697 264,918 C Deep tubewell 141,078 153,907 141,700 D Shallow tubewell with arsenic removal 170,012 220,203 172,443 E1 Pond sand filter 197,485 224,046 198,772 E2 Pond sand filter (30 households/unit) 24,869 28,213 25,031 F Deep production well, piped 88,751 104,812 89,529 G Impoundment, piped 95,111 113,180 95,986 H River abstraction, piped 86,192 102,253 86,970 a. Total costs of serving all medium villages of 500 households. Figures in bold indicate least-cost options. b. DR = discount rate.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 11. Large Villages: Present Value Analysis of Technology Costs

Technology Costs (millions US$)a DRb 10% for DRb 10% for DRb 15% for 10 years 15 years 20 years

A Dug wells 359,893 430,213 363,300 B1 Rainwater harvesting + dug well 555,615 639,078 559,658 B2 Rainwater harvesting + deep tubewell 520,351 584,736 523,470 C Deep tubewell 282,156 307,814 283,399 D Shallow tubewell with arsenic removal 340,024 440,405 344,887 E1 Pond sand filter 394,971 448,092 397,544 E2 Pond sand filter (30 households/unit) 49,737 56,426 50,061 F Deep production well, piped 144,354 166,438 145,424 G Impoundment, piped 153,645 178,539 154,851 H River abstraction, piped 142,304 164,387 143,373

a. Total costs of serving all large villages of 1,000 households. Figures in bold indicate least-cost options. b. DR = discount rate.

In order to assess the total cost of providing the Bangladesh people with arsenic-free water, we need to make some further assumptions. These assumptions, which are listed below, are adopted solely for demonstration purposes and they do not reflect in any way the policy priorities of the World Bank.

• Technology is chosen according to the geographic population distribution.

• Deep tubewells are the optimal choice for small villages up to 100 households, while river 236 237 abstraction (piped) is the optimal choice for medium and large villages of 500 and 1,000 households.

• 40% of the population is assumed to inhabit small villages, while the remainder of the population is equally divided between medium and large villages.

• Out of the total population (129 million), roughly 29 million people live in arsenic-affected areas. Moreover, we concern ourselves here with the rural population, which is approximately 99 million.11

11 There are very wide differences in the levels of exposure to arsenic throughout this rural population. Using data in Maddison, Luque, and Pearce 2004 we calculated an average exposure level for the entire rural population of 57 mg L-1, which forms the basis of the analysis undertaken here. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

• The methodology outlined can be implemented in a range of cases: for example, for one village, for a specific region, or for the whole region.

The rural population, approximately 99 million people, consists of around 18 million households. Given the geographic distribution of the population, we will assume for analytical purposes that 7,200,000 households live in small villages (72,000 villages of 100 households), 5,400,000 households live in medium villages (10,800 villages of 500 households), and 5,400,000 households live in large villages (5,400 villages of 1,000 households). Tables 12, 13, and 14 indicate the costs applicable to each of the three categories of village. Table 15 indicates total capital and operation and maintenance costs for the entire rural population. In this mode, total capital costs for the selected technology options range from US$0.6 to $6.4 billion, and total operation and maintenance costs range from $0.05 to $0.8 billion per year (table 15 see page 239).

Table 12. Small Villages: Total Costs of Mitigation Technology Options

Technology Capital costs Operation & (million US$)a maintenance costs (US$)a

A Dug wells 1,278.00 213.72 B1 Rainwater harvesting + dug well 2,441.75 253.67 B2 Rainwater harvesting + deep tubewell 2,544.15 203.00 C Deep tubewell 1,552.37 77.98 D Shallow tubewell with arsenic removal 573.56 305.08 E1 Pond sand filter 1,851.74 161.45 E2 Pond sand filter (30 households/unit) 274.33 23.92 F Deep production well, piped 1,399.12 219.66 G Impoundment, piped 1,399.12 244.07 H River abstraction, piped 1,270.98 219.66

a. Costs are for an estimated 72,000 small villages of 100 households each = 7,200,000 households.

Contd. on next page

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 13. Medium Villages: Total Costs of Mitigation Technology Options

Technology Capital costs Operation & (million US$)a maintenance costs (US$)a

A Dug wells 958.50 160.29 B1 Rainwater harvesting + dug well 1,831.31 190.25 B2 Rainwater harvesting + deep tubewell 1,908.11 152.25 C Deep tubewell 1,164.28 58.48 D Shallow tubewell with arsenic removal 430.17 228.81 E1 Pond sand filter 1,388.81 121.09 E2 Pond sand filter (30 households/unit) 174.89 15.25 F Deep production well, piped 508.61 73.22 G Impoundment, piped 521.05 82.37 H River abstraction, piped 480.97 73.22

a. Costs are for an estimated 10,800 medium villages of 500 households each = 5,400,000 households.

Table 14. Large Villages: Total Costs of Mitigation Technology Options

Technology Capital costs Operation & (million US$)a maintenance costs (US$)a

A Dug wells 958.50 160.29 B1 Rainwater harvesting + dug well 1,831.31 190.25 B2 Rainwater harvesting + deep tubewell 1,908.11 146.76 C Deep tubewell 1,164.28 58.48 238 239 D Shallow tubewell with arsenic removal 430.17 228.81 E1 Pond sand filter 1,388.81 121.09 E2 Pond sand filter (30 households/unit) 174.89 15.25 F Deep production well, piped 470.20 50.34 G Impoundment, piped 481.00 56.75 H River abstraction, piped 459.13 50.34

a. Costs are for an estimated 5,400 large villages of 1,000 households each = 5,400,000 households. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 15. All Villages: Total Costs of Mitigation Technology Options

Technology Capital costs Operation & (million US$)a maintenance costs (US$)a

A Dug wells 3,195.00 534.31 B1 Rainwater harvesting + dug well 6,104.36 634.17 B2 Rainwater harvesting + deep tubewell 6,360.38 502.02 C Deep tubewell 3,880.93 194.95 D Shallow tubewell with arsenic removal 1,433.90 762.71 E1 Pond sand filter 4,629.36 403.63 E2 Pond sand filter (30 households/unit) 624.11 54.41 F Deep production well, piped 2,377.93 343.22 G Impoundment, piped 2,401.18 383.19 H River abstraction, piped 2,211.08 343.22 a. Aggregate costs for all small, medium, and large villages (tables 12, 13, and 14).

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

4. Applying the Model

Methodology for the Model The model developed in this chapter is a CBA model described by the following equation:

∆ ∆ Σ Ii,t ( Xt ) PV (B – C) = i,t PV (Costs) > 0 (1 + s)t

We proceed by calculating the present value of costs and then estimating the relevant benefits.

Data and Estimates for the Model Given our analysis of capital costs and operation and maintenance expenses in the previous chapter, we translate these figures into present values by using a 50-year horizon and a 5%, 10%, and 15% discount rate.12 Moreover, we disaggregate these costs into costs paid by individuals and costs paid by the government based on the assumption that 20% of capital costs are paid by the individuals who bear the operation and maintenance expenses as well. This disaggregation is directly related to health benefits, as health expenditure is both private and public. As table 16 suggests, the present value of total costs is in the range US$1.6 billion to $15.4 billion for the 5% discount rate. Using the optimal choice, however, this cost drops to $0.5 billion for the government and to $1.1billion for individuals (total $1.7 billion). The respective figures for the 10% and 15% discount rates are $1.1 billion and $0.9 billion.

For a mitigation policy to result in a positive present value, the present value of benefits needs to exceed the present value of relevant costs, as these costs are calculated in table 16. In what follows we state the technique and basic assumptions made for the calculation of the relevant benefits.

Due to data nonavailability, we take into account only two sources of arsenic mitigation benefits. The first amounts to direct medical expense savings as reduced arsenic exposure dramatically 240 241 improves people’s health. The second amounts to indirect benefits of improved productivity and elevated output growth. Due to the lack of estimates on other social benefits, these are not included in our model. Our exact technique for calculating these benefits is defined negatively; that is, we estimate the costs the government would bear if no mitigation policy were undertaken. Hence, benefits are implicitly calculated as reduced costs and their present value is equal to the discounted cash flow of benefits for a 50-year horizon.

12 In this chapter both costs and benefits are discounted at 5%, 10%, and 15%. Since health benefits should be discounted for a period of at least 50 years as they spread over a lifetime, we do the same with the costs. The relevant discount rate for benefits spread over the long run (more than 30 years) should be much lower than the one used on short-run projects. This is the reason the 5% discount rate is used in addition to the 10% and 15% discount rates. In the previous chapter only 10–15% was used as the focus was only on costs, and (a) 10–15% is the lending rate in Bangladesh; and (b) 10–20 years is a reasonable payout period given the financial market in Bangladesh. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 16. Present Value of Costs of Arsenic Mitigation Options for Whole Population

Technology Govt Present value of Present value of cost private cost total cost 5% 10% 15% 5% 10% 15%

A Dug wells 2,556 10,393 5,937 4,198 12,949 8,493 6,754 B1 Rainwater + dug well 4,883 12,798 7,509 5,445 17,682 12,392 10,328 B2 Rainwater + deep tubewell 5,088 10, 437 6,249 4,616 15,525 11,338 9,704 C Deep tubewell 3,105 4,335 2,709 2,075 7,440 5,814 5,179 D Shallow tubewell/ 1,147 14,211 7,849 5,367 15, 358 8,996 6,514 arsenic removal E1 Pond sand filter 3,703 8,294 4,928 3,614 11,998 8,631 7,318 E2 Pond sand filter 499 1,118 664 487 1,618 1,164 987 (30 households/unit) F Deep production well, piped 1,902 6,741 3,879 2,762 8,664 5,781 4,664 G Impoundment, piped 1,921 7,476 4,279 3,032 9,397 6,200 4,953 H River abstraction, piped 1,769 6,708 3,845 2,728 8,477 5,614 4,497 Combined option 1,994 4,178 2,497 1,841 6,172 4,491 3,835

First, output benefits are calculated as foregone output for each person that becomes affected by arsenic-related diseases. In order to project the number of people who develop fatal cancer due to arsenic, we associate the level of arsenic in water with the risk of cancer. Specifically, the WHO (1993) set a provisional guideline value of 10 µg L-1 for arsenic in drinking water, which is associated with a lifetime excess skin cancer of about 6 per 10,000 persons. The Bangladesh standard of 50 µg L-1 is associated with a higher risk: 30 per 10,000 persons. Using the model developed by the United States Environmental Protection Agency and the distribution of population exposed to different levels of arsenic, the estimated total number of excess skin cancer victims is 375,000 if the present arsenic contamination level is maintained. If the Bangladesh standard is met, this figure drops to 55,000 and, if the WHO standard is met, it further drops to 15,000 (Ahmed 2003). However, skin cancer is not the only disease related to arsenic. Yu, Harvey, and Harvey (2003) estimate the number of people developing hyperpigmentation to be 1,200,000 and those developing keratosis to be 600,000. We project the number of people who die or become unable to work in the next 10 years to be approximately 50,000 per year (increasing by that number each year). This figure is derived by dividing the estimated 2.5 million people that are expected to develop arsenic-related diseases in the next 50 years, by 50 years (in order to get a per year estimate of affected people).

From a more detailed survey of the data currently available in the literature, Maddison, Luque, and Pearce (2004) estimate the annual impact on health from arsenic in Bangladesh as shown in table 17 (see page 242).

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 17. Bangladesh: Estimated Health Impact of Arsenic Contamination of Tubewells

Impact on health/ Males Females Combined type of illness

Cancer cases: Fatal cancers/year 3,809 2,718 6,528 Nonfatal cancers/year 1,071 1,024 2,095

Total cancer fatalities accumulated over 50 years 190,450 135,900 326,400

Arsenicosis casesa: Keratoses 277,759 74,473 352,233 Hyperpigmentation 654,718 316,511 971,230 Cough 21,823 68,887 90,712 Chest sounds 144,831 67,025 211,858 Breathlessness 93,247 176,874 270,122 Weakness 132,927 240,176 373,104 Glucosuria 67,887 63,551 131,439 High blood pressure 94,396 88,366 182,762

Total arsenicosis cases in each year 1,487,588 1,095,863 2,583,460

a. Figures indicate average number of cases occurring in each year (not number of new cases). Source: Maddison, Luque, and Pearce 2004, p. 32.

Estimates by Maddison, Luque, and Pearce (2004) suggest that 6,500 people die from cancer every year (a total of 326,000 people in a period of 50 years), while a maximum13 of 2.5 million 242 243 people develop some kind of arsenicosis. In our model, we add to the number of fatalities from cancer (6,500 people) an additional 1.7% of the total number of arsenic-affected people. This 1.7% represents the number of people that develop nonfatal diseases and become unable to work and produce.

Annual gross domestic product (GDP) is adjusted for the loss in output due to people becoming unable to work or dying. As a starting value for GDP, we take the 2002 GDP estimated at US$239 billion in purchasing power parity terms. We then assume that GDP increases by 4% each year over the next 50 years. The output lost is then calculated as the fraction of GDP the people

13 Individuals suffering from keratosis can also suffer from cough, weakness, etc. Therefore, it is not possible to translate the sum of the people suffering from different symptoms, as shown in table 17, into a unique figure indicating the total number of people suffering from arsenicosis. The figures in the table, however, can be translated into a range of possible numbers. This range will vary from 971,230 (assuming that every person who develops arsenicosis will have all the symptoms) to 2,592,083 (assuming that each person has a unique symptom, in which case the number of people with arsenicosis is the sum of the number of symptoms). Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

becoming ill would have produced. These output benefits amount to present values of $88.36 billion, $22.89 billion, and $8.77 billion for constant discount rates of 5%, 10%, and 15% respectively over a 50-year period.

Information from the National Institute of Preventive and Social Medicine (NIPSOM) of Bangladesh14 indicates that the medical expenditure for treating mild to moderate arsenicosis is US$4 to $5 per month, and the treatment generally lasts from three to six months. As far as arsenicosis cancers are concerned, the medical expenditure ranges from $300 to $1,000 per patient. Using the information above, we calculate the direct medical cost of treating mild to moderate arsenicosis, as well as arsenicosis cancer. Referring back to table 17, 8,623 people (6,500 fatal cancers plus 2,095 nonfatal cancers) are expected to develop cancer per year, while 971,230 to 2,583,460 people will develop some other arsenic-related disease. In our calculations we use this range (971,230 to 2,583,460) as an approximation of the number of treatments of mild to moderate arsenicosis per year. Then, using the upper bound of the estimates of medical costs provided by NIPSOM, we find that the total cost of treating arsenicosis cancer amounts to US$8,623,00015 and the cost of treating the rest of arsenic-related diseases is a number between $29,136,900 (= 971,230 x $30) and $77,503,800 (= 2,583,460 x $30). Using the average of the cost of treating noncancer arsenic-related diseases, and discounting the sum of medical expenditure on both cancer and mild to moderate arsenic-related diseases for a 50-year period at rates of 5%, 10%, and 15%, we get the present value of medical costs, which amount to $1.14 billion, $0.62 billion, and $0.41 billion respectively.

Before moving to section 4.3, where we calculate the net present value of different mitigation technologies, it is crucial to note that the calculated health expenditures in the previous paragraph represent lower bounds of the relevant magnitudes. That is, while these are the current actual expenditures made, they may not be really sufficient for the treatment of arsenic-related illnesses in Bangladesh. Thus it is likely that these are underestimates of the optimal level of the relevant health expenditure. This possibility is reinforced if one looks at the results of the contingent valuation study conducted by the Water and Sanitation Program, South Asia in December 2002 (Ahmad and others 2002). For rural Bangladesh, this study estimated the willingness to pay for arsenic-free, safe drinking water (that is, it estimated the value of avoiding arsenic-related health risks, which can approximate the value of avoiding the relevant health expenditure attached to these risks) to be equal to 0.2% to 0.3% of the average income of rural households. Although economic theory dictates that in a CBA one should use optimal levels of costs and benefits, we decided to use the lower bounds calculated in the previous paragraph in order to minimize the risk of exaggerating the health expenditure cost. Certainly our analysis shows that productivity losses due to illness are the primary component that drives the numbers, while the health expenditures are a secondary component to the net present value results.

14 Private communication with Dr. Akhtar. 15 This is calculated as ((6,528 + 2,095) x 1,000).

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Results for the Model Taken together both output and medical costs generate a present value that ranges from US$9.18 billion to $23.51 billion to $89.50 billion as the discount rate ranges from 15% to 10% to 5%.16

The resulting net present value ranges from $8.2–1.1 billion to $22.3–11.1 billion to $71.8–87.9 billion as the discount rate ranges from 15% to 10% to 5% (while the variation under the same discount rate reflects varying costs of different technology options). The net present value arising from these calculations can be as large as 11% of current Bangladesh GDP. However, in estimating the benefits of the arsenic mitigation program it is unrealistic to assume that a mitigation policy will be fully (100%) effective in removing arsenic.

For this reason we further proceed in estimating the benefits under two scenarios: (a) effectiveness of mitigation technology amounts to 70% of exposure reduction; and (b) effectiveness of mitigation technology amounts to 50% of exposure reduction. Under scenario (a) the relevant net present value (discounted at 10%) amounts to approximately $9.5 (15–4) billion, which constitutes around 4% of Bangladesh GDP. Under scenario (b) the relevant net present value (discounted at 10%) amounts to approximately US$5 ((–0.6) – 10.6) billion, around 2% of Bangladesh GDP.

Tables 18, 19, and 20 (see page 246, 247 and 248) show analytically our results on the net present value of various arsenic mitigation policies, with different degrees of effectiveness, and discounted at different interest rates. The effect of a lower discount rate on the resulting level of net present value, and consequently the desirability of a project is obvious from these tables.

With the exception of the option of rainwater harvesting (+ dug well) when discounted at a 10% rate, all other considered mitigation technologies are welfare increasing (that is, they pass a CBA) under all three levels of effectiveness at both 5% and 10% discount rates. However, when discounted at a 15% rate many of the mitigation technologies do not pass a CBA at lower than 100% level of effectiveness. Moreover, rainwater harvesting (+ dug well) and rainwater harvesting 244 245 (+ deep tubewell) are not welfare increasing even at 100% level of effectiveness. This result indicates that one needs to carefully evaluate what mitigation measures are implemented and that it is not true that any mitigation technology can be applied. Moreover, these results indicate that at the project level, one may want to carry out a least-cost analysis.

The use of pond sand filters (30 households per unit), taking account of the level of service, turns out to be superior to other technologies. However, even though our analysis concludes that pond sand filters are the most economically efficient option, two real-life caveats make this option less attractive. First, pond sand filters are often very polluted. To take this into account in a CBA one should ideally include in the methodology a risk-weighting factor, which will indicate the increase

16 Using a different methodology, which relies on the estimation of epidemiological dose-response functions, Maddison, Luque, and Pearce (2004, p. 34) estimate the present value of benefits at US$138.7 billion, which is comparable to our total health benefit of $162.2 billion. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

of child morbidity and mortality due to water sources. The second caveat refers to the lack of space in Bangladesh for accommodating so many pond sand filters. In earlier years space was not an issue, but now there is either not enough land in any given village due to the high population density, or people actually use the ponds for fish farming, a significant source of income in rural Bangladesh. This situation makes the shadow price involved in using the pond very high, as it should include the price of the land where the pond will be situated. It can even be the case that the corresponding land has to be purchased through an actual money transaction, which makes the relevant price an explicit one.

Overall, no significant discrepancies among technologies are documented. The more dramatic effect on the desirability of different mitigation technologies emerges by the changes in the choice of discount rate of the future flow of cost and benefits. As expected, as the discount rate increases, the net benefits of mitigation policies are reduced, to the point that, with a 15% discount rate, we encounter negative net present value. This exercise highlights the significance of the choice of the discount rate, as well as the importance of the ability to predict the degree of effectiveness of a proposed policy.

The approach suggested and applied above is applicable to both cases: (a) the risk that arsenic might be found in an area where a project is planned; and (b) approaches regarding risk mitigation options where a project’s stated purpose is arsenic mitigation itself. While the relevance of our approach to case (b) has already been demonstrated in this paper, below we clarify how the methodology can be applied to case (a).

The methodology can be applied in cases in which arsenic contamination is not as widespread as in Bangladesh and decisions have to be made about what needs to be done in advance of a project planned in an area with a high risk of being contaminated. More specifically, in such a case the policymaker should try to collect information (through hydrogeological surveys) on the existence and extent of contamination in the area under consideration. After acquiring this information, the policymaker should apply the suggested methodology in order to perform a rapid CBA, which will help decide whether it is affordable to mitigate arsenic and then complete the project under consideration, or whether arsenic mitigation is too expensive, possibly due to extensive contamination in the area. If the latter is true (that is, mitigation costs are significantly higher than benefits), then the relevant area should not be further developed through the other planned project, as development would attract people to the area, resulting in more people being exposed to arsenic in the future.

At this point it is worth mentioning that in order to establish the extent of contamination it is necessary to have a well-structured screening methodology and knowledge of the hydrogeology of the different areas in a country. This highlights the importance of investment in a screening program, as well as hydrogeological studies of high-risk areas. Both of these are necessary tools for acquiring knowledge about what is going on in a certain country, region, or area before mitigation measures or development plans are implemented. Although both of these tools are quite expensive (for example, the price of arsenic laboratory analysis is US$9, not taking into

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 18. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 5%

100% successful Technology Costs Health Output Benefits NPVb (PV)a benefits benefits (PV)a

A Dug wells 12.9 1.1 88.4 89.5 76.6 B1 Rainwater harvest + dug well 17.7 1.1 88.4 89.5 71.8 B2 Rainwater harvest + deep tubewell 15.5 1.1 88.4 89.5 74.0 C Deep tubewell 7.4 1.1 88.4 89.5 82.1 D Shallow tubewell / arsenic removal 15.4 1.1 88.4 89.5 74.1 E1 Pond sand filter 12.0 1.1 88.4 89.5 77.5 E2 Pond sand filter (30 households/unit) 1.6 1.1 88.4 89.5 87.9 F Deep production well, piped 8.6 1.1 88.4 89.5 80.9 G Impoundment, piped 9.4 1.1 88.4 89.5 80.1 H River abstraction, piped 8.5 1.1 88.4 89.5 81.0 50% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 12.9 0.6 44.2 44.8 31.8 B1 Rainwater harvest + dug well 17.7 0.6 44.2 44.8 27.1 B2 Rainwater harvest + deep tubewell 15.5 0.6 44.2 44.8 29.2 C Deep tubewell 7.4 0.6 44.2 44.8 37.3 D Shallow tubewell / arsenic removal 15.4 0.6 44.2 44.8 29.4 E1 Pond sand filter 12.0 0.6 44.2 44.8 32.8 E2 Pond sand filter (30 households/unit) 1.6 0.6 44.2 44.8 43.1 F Deep production well, piped 8.6 0.6 44.2 44.8 36.1 G Impoundment, piped 9.4 0.6 44.2 44.8 35.4 H River abstraction, piped 8.5 0.6 44.2 44.8 36.3 70% successful 246 247 Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 12.9 0.8 61.9 62.7 49.7 B1 Rainwater harvest + dug well 17.7 0.8 61.9 62.7 45.0 B2 Rainwater harvest + deep tubewell 15.5 0.8 61.9 62.7 47.1 C Deep tubewell 7.4 0.8 61.9 62.7 55.2 D Shallow tubewell / arsenic removal 15.4 0.8 61.9 62.7 47.3 E1 Pond sand filter 12.0 0.8 61.9 62.7 50.7 E2 Pond sand filter (30 households/unit) 1.6 0.8 61.9 62.7 61.0 F Deep production well, piped 8.6 0.8 61.9 62.7 54.0 G Impoundment, piped 9.4 0.8 61.9 62.7 53.3 H River abstraction, piped 8.5 0.8 61.9 62.7 54.2

a. PV = present value. b. NPV = net present value. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Table 19. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 10%

100% successful Technology Costs Health Output Benefits NPVb (PV)a benefits benefits (PV)a

A Dug wells 8.5 0.6 22.9 23.5 15.0 B1 Rainwater harvest + dug well 12.4 0.6 22.9 23.5 11.1 B2 Rainwater harvest + deep tubewell 11.3 0.6 22.9 23.5 12.2 C Deep tubewell 5.8 0.6 22.9 23.5 17.7 D Shallow tubewell / arsenic removal 9.0 0.6 22.9 23.5 14.5 E1 Pond sand filter 8.6 0.6 22.9 23.5 14.9 E2 Pond sand filter (30 households/unit) 1.2 0.6 22.9 23.5 22.3 F Deep production well, piped 5.8 0.6 22.9 23.5 17.7 G Impoundment, piped 6.2 0.6 22.9 23.5 17.3 H River abstraction, piped 5.6 0.6 22.9 23.5 17.9 50% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 8.5 0.3 11.4 11.8 3.3 B1 Rainwater harvest + dug well 12.4 0.3 11.4 11.8 -0.6 B2 Rainwater harvest + deep tubewell 11.3 0.3 11.4 11.8 0.4 C Deep tubewell 5.8 0.3 11.4 11.8 5.9 D Shallow tubewell / arsenic removal 9.0 0.3 11.4 11.8 2.8 E1 Pond sand filter 8.6 0.3 11.4 11.8 3.1 E2 Pond sand filter (30 households/unit) 1.2 0.3 11.4 11.8 10.6 F Deep production well, piped 5.8 0.3 11.4 11.8 6.0 G Impoundment, piped 6.2 0.3 11.4 11.8 5.6 H River abstraction, piped 5.6 0.3 11.4 11.8 6.1 70% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 8.5 0.4 16.0 16.5 8.0 B1 Rainwater harvest + dug well 12.4 0.4 16.0 16.5 4.1 B2 Rainwater harvest + deep tubewell 11.3 0.4 16.0 16.5 5.1 C Deep tubewell 5.8 0.4 16.0 16.5 10.6 D Shallow tubewell / arsenic removal 9.0 0.4 16.0 16.5 7.5 E1 Pond sand filter 8.6 0.4 16.0 16.5 7.8 E2 Pond sand filter (30 households/unit) 1.2 0.4 16.0 16.5 15.3 F Deep production well, piped 5.8 0.4 16.0 16.5 10.7 G Impoundment, piped 6.2 0.4 16.0 16.5 10.3 H River abstraction, piped 5.6 0.4 16.0 16.5 10.8 a. PV = present value. b. NPV = net present value. Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Table 20. NPV (in Billion US$) of Arsenic Mitigation Policies, Discounted at 15%

100% successful Technology Costs Health Output Benefits NPVb (PV)a benefits benefits (PV)a

A Dug wells 6.8 0.4 8.8 9.2 2.4 B1 Rainwater harvest + dug well 10.3 0.4 8.8 9.2 -1.1 B2 Rainwater harvest + deep tubewell 9.7 0.4 8.8 9.2 -0.5 C Deep tubewell 5.2 0.4 8.8 9.2 4.0 D Shallow tubewell / arsenic removal 6.5 0.4 8.8 9.2 2.7 E1 Pond sand filter 7.3 0.4 8.8 9.2 1.9 E2 Pond sand filter (30 households/unit) 1.0 0.4 8.8 9.2 8.2 F Deep production well, piped 4.7 0.4 8.8 9.2 4.5 G Impoundment, piped 5.0 0.4 8.8 9.2 4.2 H River abstraction, piped 4.5 0.4 8.8 9.2 4.7 50% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 6.8 0.2 4.4 4.6 -2.2 B1 Rainwater harvest + dug well 10.3 0.2 4.4 4.6 -5.7 B2 Rainwater harvest + deep tubewell 9.7 0.2 4.4 4.6 -5.1 C Deep tubewell 5.2 0.2 4.4 4.6 -0.6 D Shallow tubewell / arsenic removal 6.5 0.2 4.4 4.6 -1.9 E1 Pond sand filter 7.3 0.2 4.4 4.6 -2.7 E2 Pond sand filter (30 households/unit) 1.0 0.2 4.4 4.6 3.6 F Deep production well, piped 4.7 0.2 4.4 4.6 -0.1 G Impoundment, piped 5.0 0.2 4.4 4.6 -0.4 H River abstraction, piped 4.5 0.2 4.4 4.6 -0.1 70% successful 248 249 Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV)

A Dug wells 6.8 0.3 6.1 6.4 -0.3 B1 Rainwater harvest + dug well 10.3 0.3 6.1 6.4 -3.9 B2 Rainwater harvest + deep tubewell 9.7 0.3 6.1 6.4 -3.3 C Deep tubewell 5.2 0.3 6.1 6.4 1.2 D Shallow tubewell / arsenic removal 6.5 0.3 6.1 6.4 -0.1 E1 Pond sand filter 7.3 0.3 6.1 6.4 -0.9 E2 Pond sand filter (30 households/unit) 1.0 0.3 6.1 6.4 5.4 F Deep production well, piped 4.7 0.3 6.1 6.4 1.8 G Impoundment, piped 5.0 0.3 6.1 6.4 1.5 H River abstraction, piped 4.5 0.3 6.1 6.4 1.9

a. PV = present value. b. NPV = net present value. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

account transportation costs, while the price of a field kit is $0.5 per test) they are a necessary first step of any decision about project implementation.

The logic behind this necessity is the following. The long-run nature of project-specific developments means that initial screening costs will be discounted over a long-run horizon; hence, these costs will be relatively small in net present value terms irrespective of their absolute initial value. On the contrary, the effects of arsenic contamination could be detrimental to both the economy and health of the inhabitants of an area over a much shorter horizon. Moreover, it should be kept in mind that the decision to develop a particular area is irreversible in practical terms. This characteristic of irreversibility necessitates great caution about the decision to develop or not, hence such decisions should be taken under minimum risk conditions. The combined result of these three effects increases the net potential benefit to society that can be achieved through gathering information regarding the existence and extent of arsenic contamination prior to any other project-related appraisal.

This discussion indicates that an option value underlies the development of particular projects in high-risk areas. Option value is a measure of people’s (society’s) risk aversion to factors that might affect future access to use of environmental or biological assets. More precisely, the option value relevant to our discussion is the premium that society is willing to pay to avoid having to face the effects of arsenic contamination in the area where economic and social development is planned. In our case, this premium is the money that the society (the government) will spend on screening and hydrological studies in order to gather enough information to allow the choice of a development area with a minimum risk of arsenic contamination. This allows society to reduce the risk (variance) associated with future welfare.

In conclusion, as long as society is risk averse and the development horizon is long, screening and hydrological studies that enable such risk reductions are likely to be welfare increasing.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

5. Summary and Conclusions

his paper reviews existing studies and data on arsenic contamination, related health effects, Tand the costs of mitigation in those countries where it has been undertaken. Then it introduces an approach which provides a quick and readily applicable method for performing a CBA of different arsenic mitigation policies. In particular, our suggested approach estimates benefits of mitigation activities as the sum of foregone medical costs and saved output productivity achieved through the reduction of arsenic exposure. The present value of these benefits is then compared with the present value of costs of various mitigation measures in order to determine when and which mitigation policies pass a CBA (that is, produce a positive change to social welfare).

The paper applies this approach in order to provide some estimate of costs and benefits of arsenic mitigation in one case study country, Bangladesh. This case study serves as an applied example of a rapid socioeconomic evaluation and is also used as a basis for discussing trade- offs in decisionmaking with respect to the allocation of financial resources. Our approach is applicable to the following cases: (a) where there is risk that arsenic might be found in an area where a project is planned; and (b) in regard to risk mitigation options where a project’s goal is arsenic mitigation per se.

With the exception of the option of rainwater harvesting (+ dug well) when discounted at a 10% rate, all other considered mitigation technologies are welfare increasing (that is, they pass a cost- benefit analysis) under all three levels of effectiveness at both 5% and 10% discount rates. However, when discounted at a 15% rate, many of the mitigation technologies do not pass a CBA at lower than 100% level of effectiveness. Moreover, rainwater harvesting (+ dug well) and rainwater harvesting (+ deep tubewell) are not welfare increasing even at 100% level of effectiveness. This result indicates that one needs to carefully evaluate what mitigation measures are implemented and that it is not true that any mitigation technology can be applied. Moreover, these results indicate that, at the project level, one may want to carry out a least-cost analysis.

It is also worth mentioning that (a) in our calculation we did not take into account the 250 251 environmental benefits of mitigation strategies (mainly due to lack of precise data); and that (b) the health expenditures only represent a lower bound. That is, the calculated net benefits from arsenic mitigation are underestimates of the true benefits and should be used as a very conservative figure of welfare increases to be derived from implementing the various mitigation policies.

Finally, these figures indicate the imminent need for facing the arsenic crisis in Bangladesh, but also the clarity with which our approach can answer the difficult question on the balance of relevant costs and benefits of various mitigation policies. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Annex 1

Detailed Technology Costs The tables below itemize the costs of each technology for a village of 500 households.

Average Village Model: 500 Households Income Categories

Nos. High Medium Low Total

Homesteads (clusters) 50 Proportion 10% 20% 70% 100% Households @ 10 per homestead 500 Households 50 100 350 500 Population @ 5.5 per household 2,750 Population 275 550 1,925 2,750

Option A: Dug Wells

Capital costs Unit Qty Rate (US$) Amt (US$)

Excavation: depth 12.5 m m3 10 10 102 Pipe rings supply m 12.5 20 254 Pipe rings install m 12.5 8 106 Handpump supply & install no. 1 68 68 Transport sum 1 85 85 Contingencies and handover/training sum 1 34 34 Platform + other core components work sum 1 102 102 Total 750 Operation & maintenance Unit Qty Rate (US$) Amt (US$) costs annual

Chemical: disinfection kg 15 2 25 Labour days 24 2 41 Spares/parts sum 1 17 17 Water quality monitoring sum 5 8 42 Total 125 Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/dug well 1 3 10 n.a. No. of dug wells 50 33 35 118 Financial costs

Capital 88,750 Annual operation & maintenance 14,842 n.a. Not applicable.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Option B1: Roof Rainwater Harvest/Household (60 sq m) + Dug Well

Capital costs: roof catchment Unit Qty Rate (US$) Amt (US$)

Roof gutters m 36 3 107 Pipework m 7 5 36 Tank 3.2 m3 on platform/3 month storage no. 1 105 105 Handpump supply and install no. 0 n.a. n.a. Transport sum 1 17 17 Contingencies and handover/training sum 1 8 8 Roof rainwater harvest capital cost Total 273 Dug well capital cost sum 1 750 750

Operation & maintenance costs Unit Qty Rate (US$) Amt (US$) annual (roof catchment)

Chemical: disinfection kg 0.25 2 0 Labour days 7 2 12 Spares/parts sum 1 3 3 Water quality monitoring sum 1 8 8 Total 2 4 Dug well months 12 10.45 125

Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 252 253 Households/rainwater harvest 1 1 1 n.a. No. of rainwater harvest systems 50 100 350 500 Households/dug well 3 10 20 n.a. No. of dug wells 17 10 18 44

Financial costs

Capital 169,566 Annual operation & maintenance 17,616

n.a. Not applicable. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Option B2: Roof Rainwater Harvest/Household (60 sq m) + Deep Tubewell

Capital costs: roof catchment Unit Qty Rate (US$) Amt (US$)

Roof gutters m 36 3 107 Pipework m 7 5 36 Tank 3.2 m3 on platform/3 month storage no. 1 105 105 Handpump supply and install no. 0 n.a. n.a. Transport sum 1 17 17 Contingencies and handover/training sum 1 8 8 Roof rainwater harvest capital cost Total 273 Deep tubewell capital cost sum 1 911 911

Operation & maintenance costs Unit Qty Rate (US$) Amt (US$) annual (roof catchment)

Chemical: disinfection kg 0.25 2 0 Labour days 7 2 12 Spares/parts sum 1 3 3 Water quality monitoring sum 1 8 8 Total 2 4 Deep tubewell months 12 4 46

Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/rainwater harvest 1 1 1 n.a. No. of rainwater harvest systems 50 100 350 500 Households/deep tubewell 3 10 20 n.a. No. of deep tubewells 17 10 18 44

Financial costs

Capital 176,677 Annual operation & maintenance 14,097 n.a. Not applicable.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Option C: Hand Deep Tubewell

Capital costs Unit Qty Rate (US$) Amt (US$)

Sinking m 250 0.3 64 35 mm pipe supply + stainer m 250 1.7 424 Pipe install m 250 0.8 212 Handpump supply & install no. 1 127.1 127 Transport sum 1 33.9 34 Contingencies and handover sum 1 16.9 17 Platform + other core components work sum 1 33.9 34 Total 911

Operation & maintenance Unit Qty Rate (US$) Amt (US$) costs annual

Chemical: disinfection kg 0 n.a. n.a. Labour days 12 1.7 20 Spares/parts sum 1 16.9 17 Water quality monitoring sum 1 8.5 8 Total 4 6

Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/deep tubewell 1 3 10 n.a. 254 255 No. of deep tubewells 50 33 35 118

Financial costs

Capital 107,804 Annual operation & maintenance 5,415

n.a. Not applicable. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Option D: Existing Shallow Tubewell with Household Arsenic Removal

Capital costs Unit Qty Rate (US$) Amt (US$)

Arsenic removal supply & install no. 1 50.8 51 Transport sum 1 3.4 3 Contingencies and handover/training sum 1 25.4 25 Total 8 0

Operation & maintenance Unit Qty Rate (US$) Amt (US$) costs annual

Chemical: disinfection kg 0 n.a. n.a. Labour days 0 n.a. n.a. Media/spares/parts sum 1 25.4 25 Water testing (for arsenic) sum 2 8.5 17 Total 4 2 Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/arsenic removal unit 1 1 1 n.a. No. of arsenic removal 50 100 350 500

Financial costs

Capital 39,831 Annual operation & maintenance 21,186 n.a. Not applicable.

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

Option E: Pond Sand Filter

Capital costs Unit Qty Rate (US$) Amt (US$)

Excavation m3 63.420 Reinforced concrete including formwork m3 41.77 Block wall m2 48 11.9 569 Handpump supply & install no. 1 67.8 68 Transport sum 1 33.9 34 Contingencies and handover/training sum 1 254.2 254 Total 953

Operation & maintenance Unit Qty Rate (US$) Amt (US$) costs annual

Chemical: disinfection kg 15 1.7 25 Labour days 24 1.7 41 Spares/parts sum 1 16.9 17 Total 8 3

Infrastructure required Income High Medium Low Total

Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/pond sand filter 1 2 10 n.a. No. of pond sand filters 50 50 35 135

Financial costs 256 257 Capital 128,593 Annual operation & maintenance 11,212

n.a. Not applicable. Volume II Technical Report Arsenic Contamination of Groundwater in South and East Asian Countries

Option F: Piped Scheme Deep Production Well (Domestic)

Capital costs Unit Qty Rate (US$) Amt (US$)

Production wells sum 3,627 Sinking/drilling and core samples m 300 3.2 966 Pumping facilities sum 6,356 Masonry/concrete storage tanks sum 8,305 Trunk main/transmission main sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 47,093 Operation & maintenance costs annual Total 6,780

Option G: Piped Scheme Impoundment: Engineered Pond

Capital costs Unit Qty Rate (US$) Amt (US$)

Impoundment sum 4,237 Intake/infiltration gallery sum 1,508 Pumping facilities sum 6,356 Masonry/concrete storage tanks sum 8,305 Trunk main/transmission main sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 48,246 Operation & maintenance costs annual Total 7,627

Option H: Piped Scheme Surface Water: River Abstraction/Infiltration Gallery

Capital costs Unit Qty Rate (US$) Amt (US$)

Intake/infiltration gallery sum 2,034 Pumping facilities sum 6,356 Masonry/concrete storage tanks sum 8,305 Trunk main/transmission main sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 44,534 Operation & maintenance costs annual Total 6,780

Paper 4 The Economics of Arsenic Mitigation Volume II Technical Report Towards a More Effective Operational Response

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Paper 4 The Economics of Arsenic Mitigation VOL II TECHNICAL REPORT Notes Notes VOL II TECHNICAL REPORT TECHNICAL II VOL

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