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University of Plymouth PEARL https://pearl.plymouth.ac.uk The Plymouth Student Scientist - Volume 03 - 2010 The Plymouth Student Scientist - Volume 3, No. 2 - 2010 2010 An investigation of the risks for human health from bio-available and bio-accessible arsenic in the Tamar catchment using human hair bio-markers and geochemical data Cattan, R. Cattan, R. (2010) 'An investigation of the risks for human health from bio-available and bio-accessible arsenic in the Tamar catchment using human hair bio-markers and geochemical data', The Plymouth Student Scientist, p.181-232. http://hdl.handle.net/10026.1/13919 The Plymouth Student Scientist University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. The Plymouth Student Scientist, 2010, 3, (2), 181-232 An investigation of the risks for human health from bio-available and bio-accessible arsenic in the Tamar catchment using human hair bio- markers and geochemical data Richard Cattan Project Advisor: Charlotte Braungardt, School of Geography, Earth & Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA Abstract Geologic mineralisation and anthropogenic exploitation in the Tamar catchment of south-west England have resulted in an environment enriched with arsenic, a recognised carcinogen and systemic toxicant that can target many organs in the human body. This study examined geochemical data from the catchment and found particularly high arsenic contamination around the historic mining districts of Callington and Gunnislake, where maximum concentrations of 39 µg L-1 in stream waters, 11000 mg kg-1 in stream sediments, and 15000 mg kg-1 in topsoils were found in certain areas. Hair samples from 91 catchment residents were analysed using inductively-coupled plasma mass spectrometry. The arsenic levels found in their hair ranged from 4.87 to 1150 µg kg-1, with a geometric mean of 43.1 µg kg-1 and 95% confidence interval of 33.7 to 55.2 µg kg-1. Most samples (59.3%) were within the typical range found in hair from people unexposed to arsenic, but three samples exceeded the expected value of 1000 µg kg-1 of arsenic in hair based on accepted dietary intake. Statistical tests indicated the main influences on arsenic bio-availability were living within 5 km of an arsenic- contaminated area, or growing and/ or consuming locally-grown food. The hair arsenic concentrations were significantly correlated with copper, phosphorus and zirconium in topsoils, and pH and conductivity in stream waters. A multiple regression equation was derived to relate bio-availability with bio-accessibility and indicate parts of the catchment where humans may have high arsenic levels in their hair, highlighting the arsenic bio- availability risks of areas in the south of the catchment. This study contributes to the limited available data on human bio-markers of arsenic exposure in the catchment. The incorporation of geochemical and bio-marker data in a combined bio-accessible and bio-available multiple regression model offers a robust alternative for human health risk assessment, and the fitted model could guide land use planning and remediation of areas at risk from arsenic-related health problems. It could also be used with epidemiological studies of disease incidence in the catchment. [181] The Plymouth Student Scientist, 2010, 3, (2), 181-232 Table of Contents Abstract..................................................................................................................................................... 181 Acknowledgements .................................................................................................................................. 183 1. Introduction ..................................................................................................... 184 2. Arsenic in the environment ............................................................................ 187 2.1. Sources of arsenic .................................................................................................. 187 2.2. Speciation and mobility ........................................................................................... 189 2.3. Human exposure pathways ..................................................................................... 190 2.4. Arsenic toxicology ................................................................................................... 192 2.5. Measuring human exposure .................................................................................... 193 3. The Tamar catchment ..................................................................................... 195 3.1. Physical characteristics ........................................................................................... 195 3.2. Land use and population ......................................................................................... 197 3.3. Legacy of mining activities ...................................................................................... 197 3.4. Arsenic in the Tamar environment ........................................................................... 200 4. Methodology ................................................................................................... 206 4.1. Sample collection .................................................................................................... 206 4.2. Sample preparation and analysis ............................................................................ 206 4.3. Statistical and spatial analyses ................................................................................ 207 5. Results and discussion .................................................................................. 209 5.1. Accuracy and precision ........................................................................................... 209 5.2. Arsenic levels in catchment residents ..................................................................... 210 5.3. Physical and lifestyle influences .............................................................................. 211 5.4. Spatial distribution ................................................................................................... 216 5.5. Bio-available and bio-accessible arsenic ................................................................. 219 6. Conclusions .................................................................................................... 226 References ............................................................................................................................................... 228 [182] The Plymouth Student Scientist, 2010, 3, (2), 181-232 List of Figures Figure 1: Melanoma, prostate cancer and kidney cancer incidence for all persons in England ................................................................................................................. 185 Figure 2: Eh-pH diagram for As at 25 °C and 1 atmosphere ....................................... 189 Figure 3: Schematic of the ICP-MS technique ............................................................. 194 Figure 4: Bedrock geology and former As mining sites in the Tamar catchment .......... 196 Figure 5: Land use categories in the Tamar catchment ............................................... 198 Figure 6: Resident population in the Tamar catchment ................................................ 199 Figure 7: G-BASE As concentrations in stream waters and soil drainage types .......... 201 Figure 8: G-BASE As concentrations in stream sediments of the catchment .............. 202 Figure 9: G-BASE As concentrations in surface soils and soil types ........................... 203 Figure 10: Assessment of laboratory precision showing mean replicate measurements .............................................................................................................................. 209 Figure 11: Box and whisker plot of hair As levels and use of local food ....................... 213 Figure 12: Spatial representation of total As concentrations in hair samples ............... 216 Figure 13: Hair As levels aggregated to participants‘ postcodes .................................. 217 Figure 14: Box and whisker plot of hair As levels and the sources of hair samples. .... 218 Figure 15: Multiple regression equation for hair As ...................................................... 220 Figure 16: Ratios between soil As and soil Cu in the G-BASE survey area and hair As concentrations ....................................................................................................... 222 Figure 17: Ratios of soil As and soil P in the G-BASE survey area ............................. 223 Figure 18: Spatial representation of As bio-availability risk for the Tamar catchment ... 225 List of Tables Table 1: Common As concentrations in major rock types ............................................ 187 Table 2: Typical As content of surface soils in different countries ................................ 188 Table 3: Total As concentrations in samples from various food groups ........................ 191 Table 4: Summary of G-BASE results for As in the Tamar catchment.......................... 200 Table 5: ICP-MS operational settings