Environmental Monitoring and Biomonitoring of Human Arsenic Exposure
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ENVIRONMENTAL MONITORING AND BIOMONITORING OF HUMAN ARSENIC EXPOSURE A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences 2016 DANIEL RICHARD SIMON MIDDLETON BSc (Hons) SCHOOL OF EARTH, ATMOSPHERIC AND ENVIRONMENTAL SCIENCES 1 LIST OF CONTENTS LIST OF TABLES ..................................................................................................... 6 LIST OF FIGURES ................................................................................................... 8 LIST OF ABBREVIATIONS ................................................................................. 11 ABSTRACT .............................................................................................................. 14 DECLARATION ...................................................................................................... 15 COPYRIGHT STATEMENT ................................................................................. 16 DEDICATION .......................................................................................................... 17 ACKNOWLEDGMENTS ....................................................................................... 17 FUNDING ................................................................................................................. 18 RATIONALE FOR SUBMISSION OF ALTERNATIVE FORMAT ................ 19 RESEARCH CONTEXT AND AUTHORSHIP CONTRIBUTIONS ................ 19 CHAPTER 1: INTRODUCTION ........................................................................... 23 1.1. Background and rationale ............................................................................ 23 1.1.1. Environmental geochemistry of arsenic ................................................... 23 1.1.2. Arsenic exposure: pathways and guidance values ................................... 24 1.1.3. Arsenic speciation and biotransformation ................................................ 25 1.1.4. Toxicity and health implications of chronic exposure to arsenic ............. 27 1.1.5. Global arsenic exposure ........................................................................... 28 1.1.6. Study area: south west England ............................................................... 30 1.1.7. Biomonitoring of arsenic exposure ........................................................... 30 1.2. Work previously conducted .......................................................................... 32 1.2.1. Arsenic biomonitoring: exposure assessment and interpretation............. 32 1.2.2. Arsenic biomonitoring: technical considerations ..................................... 36 1.2.3. Arsenic in south west England: environmental monitoring...................... 38 1.2.4. Arsenic in south west England: human exposure biomonitoring ............. 45 1.2.5. Arsenic in south west England: public health implications ...................... 47 1.3. Aims and objectives ....................................................................................... 50 CHAPTER 2: METHODOLOGY .......................................................................... 51 2.1. Chapter overview .......................................................................................... 51 2.2. Ethical approval ............................................................................................ 51 2.3. Volunteer recruitment................................................................................... 52 2.3.1. Sampling design ........................................................................................ 52 2.3.2. Recruitment logistics................................................................................. 54 2 2.3.3. Response rates .......................................................................................... 55 2.3.4. Invitation letter, FAQ leaflet and GP letter .............................................. 55 2.4. Field work and sample collection ................................................................. 65 2.4.1. Sample collection guide, consent and withdrawal forms ......................... 65 2.4.2. Fieldwork .................................................................................................. 73 2.4.3. Urine, toenail and hair collection............................................................. 75 2.4.4. Drinking water collection ......................................................................... 75 2.4.5. Residential soil collection ......................................................................... 76 2.4.6. Indoor dust collection ............................................................................... 76 2.4.7. Rice collection........................................................................................... 76 2.4.8. Exposure assessment questionnaire.......................................................... 77 2.5. Chemical analysis .......................................................................................... 87 2.5.1. Storage considerations ............................................................................. 87 2.5.2. Analytical measurements and techniques ................................................. 88 2.5.3. Quality assurance and quality control ..................................................... 90 2.6. Data management and statistical analysis ................................................... 90 2.6.1. Software .................................................................................................... 90 2.6.2. Safe handling ............................................................................................ 90 2.6.3. Data preparation: reduction and censoring ............................................. 91 2.6.4. Exploratory data analysis ......................................................................... 91 2.7. Reporting of results to volunteers ................................................................ 91 CHAPTER 3 ............................................................................................................. 92 CHAPTER 4 ............................................................................................................. 93 CHAPTER 5 ............................................................................................................. 94 CHAPTER 6 ............................................................................................................. 95 CHAPTER 7: SUMMARY AND CONCLUSIONS ............................................. 96 7.1. Key findings and further work ..................................................................... 96 7.1.1. Arsenic exposure from private water supplies .......................................... 96 7.1.2. The performance of urinary hydration adjustments ................................. 97 7.1.3. Prolonged arsenic exposure from private water supplies ........................ 99 7.1.4. Toenails and hair as viable biomarkers of arsenic exposure ................... 99 7.1.5. Potential arsenic exposure from residential soil and dust ..................... 100 7.1.6. Ongoing analysis .................................................................................... 101 7.2. Conclusions .................................................................................................. 102 REFERENCES ....................................................................................................... 103 3 APPENDIX A: ETHICAL APPROVAL LETTER ............................................ 132 APPENDIX B: RESULTS LETTERS ................................................................. 135 APPENDIX C: LIST OF CONFERENCE PRESENTATIONS AND OUTREACH ACTIVITIES .................................................................................. 152 APPENDIX D: EXTENDED ABSTRACT .......................................................... 155 4 Final word count: 75,490 5 LIST OF TABLES Page numbering of individual publication chapters is not in sequence with the main thesis. For tables in these chapters, both thesis page numbers that mark the start of the chapters and the chapter-specific page numbers are provided. Chapter 1 Thesis p. (publication p.) Table 1 35 Published reference values for total arsenic and toxicologically relevant arsenic species in urine from nationally representative population-based surveys and smaller studies. Chapter 2 Table 2 53 An example of the data layout using the adopted coding system. Table 3 73 Study group characteristics and details of environmental and biological samples collected during the field work campaign. Table 4 87 Storage considerations and measures employed for certain environmental and biological samples. Table 5 89 A summary of the analytical measurements, techniques and instrumentation for all environmental and biological samples collected. Chapter 3 Table 1 92 (4) Descriptive statistics for drinking water and urinary arsenic concentrations. Table 2 92 (5) Correlation analysis of exposure and outcome variables for all volunteers. Table 3 92 (6) Correlation analysis of exposure and outcome variables for single volunteers per household. Table S1 92 (12) Households categorised by ONS rural-urban classification. Chapter 4 Table 1 93 (6) Suggested criteria for assessing performance of urinary biomonitoring adjustment methods. Table 2 93 (13) Demographic characteristics and unadjusted analyte geometric means and ranges for training and testing datasets. Table 3 93 (15) Araki’s b values derived