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Guidelines for Drinking-Water Quality, Fourth Edition

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Guidelines for Drinking-Water Quality, Fourth Edition 12 Chemical fact sheets A conceptual framework for Introduction implementing the Guidelines (Chapter 1) (Chapter 2) he background docu- FRAMEWORK FOR SAFE DRINKING-WATER SUPPORTING Tments referred to in INFORMATION this chapter (as the princi- Health-based targets Public health context Microbial aspects pal reference for each fact (Chapter 3) and health outcome (Chapters 7 and 11) sheet) may be found on Water safety plans Chemical aspects (Chapter 4) (Chapters 8 and 12) the Water, Sanitation, Hy- System Management and Radiological Monitoring giene and Health web site assessment communication aspects at http://www.who.int/ (Chapter 9) Acceptability Surveillance water_sanitation_health/ aspects (Chapter 5) dwq/chemicals/en/index. (Chapter 10) html. A complete list of r eferences cited in this Application of the Guidelines in specic circumstances chapter, including the (Chapter 6) background documents Climate change, Emergencies, Rainwater harvesting, Desalination for each c hemical, is pro- systems, Travellers, Planes and vided in Annex 2. ships, etc. 12.1 Chemical contaminants in drinking-water Acrylamide Residual acrylamide monomer occurs in polyacrylamide coagulants used in the treat- ment of drinking-water. In general, the maximum authorized dose of polymer is 1 mg/l. At a monomer content of 0.05%, this corresponds to a maximum theoretical concen- tration of 0.5 µg/l of the monomer in water. Practical concentrations may be lower by a factor of 2–3. This applies to the anionic and non-ionic polyacrylamides, but residual levels from cationic polyacrylamides may be higher. Polyacrylamides are also used as grouting agents in the construction of drinking-water reservoirs and wells. Human ex- posure is much greater from food than from drinking-water, owing to the formation of acrylamide in foods (e.g. breads, fried and roasted foods) cooked at high temperatures. 307 GUIDELINES FOR DRINKING-WATER QUALITY Guideline value 0.0005 mg/l (0.5 µg/l) Occurrence Concentrations up to a few micrograms per litre occasionally detected in tap water Basis of guideline value Combined mammary, thyroid and uterine tumours observed in female rats derivation in a drinking-water study, and using the linearized multistage model Limit of detection 0.032 µg/l by gas chromatography (GC); 0.2 µg/l by high-performance liquid chromatography (HPLC); 10 µg/l by HPLC with ultraviolet (UV) detection Treatment performance Conventional treatment processes do not remove acrylamide. Acrylamide concentrations in drinking-water are usually controlled by limiting either the acrylamide content of polyacrylamide flocculants or the dose used, or both. Advances in analytical techniques are also beginning to allow control by direct measurement (see background document). Additional comments Every effort should be made to limit free acrylamide monomer in polyacrylamide used for water treatment, and water suppliers should also make every effort to ensure that residual acrylamide in drinking- water is kept as low as is technically feasible. In particular, if acrylamide is controlled by limiting the amount dosed, overdosing should always be avoided. Assessment date 2011 Principal references FAO/WHO (2011) Evaluation of certain contaminants in food WHO (2011) Acrylamide in drinking-water Following ingestion, acrylamide is readily absorbed from the gastrointestinal tract and widely distributed in body fluids. Acrylamide can cross the placenta. It is neuro- toxic, affects germ cells and impairs reproductive function. In mutagenicity assays, acrylamide was negative in the Ames test but induced gene mutations in mammalian cells and chromosomal aberrations in vitro and in vivo. In a long-term carcinogenicity study in rats exposed via drinking-water, acrylamide induced scrotal, thyroid and adrenal tumours in males and mammary, thyroid and uterine tumours in females. The International Agency for Research on Cancer (IARC) has placed acrylamide in Group 2A (probably carcinogenic to humans). The Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) has recently noted concerns regarding the carcinogenicity and neurotoxicity of acrylamide and concluded that dietary exposure should be re- duced to as low a level as technically achievable. Recent data have shown that expos- ure to acrylamide from cooked food is much higher than previously thought. As it is difficult to control the intake of acrylamide from food, it is very important that the acrylamide content of polyacrylamide used as a coagulant aid in water treatment, the most important source of drinking-water contamination by acrylamide, be as low as possible and that polyacrylamide not be overdosed in an attempt to take a shortcut to improving coagulation. Alachlor Alachlor (Chemical Abstracts Service [CAS] No. 15972-60-8) is a pre-emergence and post-emergence herbicide used to control annual grasses and many broad-leaved weeds 308 12. CHEMICAL FACT SHEETS in maize and a number of other crops. It is lost from soil mainly through v olatilization, photodegradation and biodegradation. Many alachlor degradation products have been identified in soil. Alachlor was included in the Prior Informed Consent proced- ure of the Rotterdam Convention on the basis of the final regulatory actions taken by the European Community and by Canada to ban alachlor as a p esticide. Guideline value 0.02 mg/l (20 µg/l) Occurrence Has been detected in groundwater and surface water; has also been detected in drinking-water at levels below 0.002 mg/l Basis of guideline value Calculated by applying the linearized multistage model to data on the derivation incidence of nasal tumours in rats Limit of detection 0.1 µg/l by gas–liquid chromatography with electrolytic conductivity detection in the nitrogen mode or by capillary column GC with a nitrogen– phosphorus detector Treatment performance 0.001 mg/l should be achievable using granular activated carbon (GAC) Assessment date 1993 Principal reference WHO (2003) Alachlor in drinking-water On the basis of available experimental data, evidence for the genotoxicity of ala- chlor is considered to be equivocal. However, a metabolite of alachlor, 2,6-diethylanil- ine, has been shown to be mutagenic. Available data from two studies in rats clearly indicate that alachlor is carcinogenic, causing benign and malignant tumours of the nasal turbinate, malignant stomach tumours and benign thyroid tumours. Aldicarb Aldicarb (CAS No. 116-06-3) is a systemic pesticide used to control nematodes in soil and insects and mites on a variety of crops. It is very soluble in water and highly mo- bile in soil. It degrades mainly by biodegradation and hydrolysis, persisting for weeks to months. Guideline value 0.01 mg/l (10 µg/l) Occurrence Frequently found as a contaminant in groundwater in the vicinity of application areas, particularly when associated with sandy soil; concen- trations in well water as high as 500 µg/l have been measured; aldicarb sulfoxide and aldicarb sulfone residues are found in an approximately 1:1 ratio in groundwater Acceptable daily intake (ADI) 0–0.003 mg/kg body weight based on cholinesterase depression in a single oral dose study in human volunteers Limit of detection 0.001 mg/l by reversed-phase HPLC with fluorescence detection Treatment performance 0.001 mg/l should be achievable using GAC or ozonation Guideline value derivation • allocation to water 10% of upper limit of ADI • weight 60 kg adult • consumption 2 litres/day 309 GUIDELINES FOR DRINKING-WATER QUALITY Additional comments The guideline value derived from the 1992 assessment of the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) was very similar to the guideline value derived in the second edition, which was therefore retained. Assessment date 2003 Principal references FAO/WHO (1993) Pesticide residues in food—1992 evaluations WHO (2003) Aldicarb in drinking-water Aldicarb is one of the most acutely toxic pesticides in use, although the only con- sistently observed toxic effect with both long-term and single-dose administration is acetylcholinesterase inhibition. It is converted to the sulfoxide and sulfone. Aldicarb sulfoxide is a more potent inhibitor of acetylcholinesterase than aldicarb itself, where- as aldicarb sulfone is considerably less toxic than either aldicarb or the sulfoxide. The weight of evidence indicates that aldicarb, aldicarb sulfoxide and aldicarb sulfone are not genotoxic or carcinogenic. IARC has concluded that aldicarb is not classifiable as to its carcinogenicity (Group 3). Aldrin and dieldrin Aldrin (CAS No. 309-00-2) and dieldrin (CAS No. 60-57-1) are chlorinated pesti- cides that are used against soil-dwelling pests, for wood protection and, in the case of dieldrin, against insects of public health importance. Since the early 1970s, many countries have either severely restricted or banned the use of both compounds, par- ticularly in agriculture. The two compounds are closely related with respect to their toxicology and mode of action. Aldrin is rapidly converted to dieldrin under most environmental conditions and in the body. Dieldrin is a highly persistent organo- chlorine compound that has low mobility in soil, can be lost to the atmosphere and bioaccumulates. D ietary exposure to aldrin/dieldrin is very low and decreasing. Guideline value Aldrin and dieldrin (combined): 0.000 03 mg/l (0.03 µg/l) Occurrence Seldom detected in drinking-water; concentrations of aldrin and dieldrin in drinking-water normally less than 0.01 µg/l;
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