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Title: Environmental monitoring and biomonitoring of human arsenic exposure
Author: Middleton, Daniel
ISNI:       0000 0004 6496 0756
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2016
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This study investigated human exposure to inorganic arsenic (As), a risk factor for cancer and non-cancerous health effects, in Cornwall, UK - a region of elevated environmental As resulting from naturally occurring mineralisation and historical mining. Recent exposures to As from private water supplies (PWS) were detected by measuring As in drinking water samples (n=127) and urine samples (n=207). Exceedances of the WHO 10 As µg L-1 guidance value were measured in drinking waters from 5 % of households. The Spearman correlation calculated for drinking water versus unadjusted total urinary As concentrations was 0.36. Urinary As speciation was used to distinguish between environmental inorganic As exposure and non-toxic dietary sources. Seafood derived urinary arsenobetaine exclusion and osmolality hydration adjustment yielded an improved correlation of 0.62 between drinking water and urinary As concentrations. Urinary hydration adjustment methods were improved and comparatively assessed using data from the US National Health and Nutrition Examination Survey (NHANES). Correlations of urinary concentrations of As, iodine (I), lead (Pb) and cadmium (Cd) against urinary flow rate (UFR) (low correlations desired) and urinary Pb and Cd against respective blood concentrations (high correlations desired) were used as independent performance criteria. Osmolality adjustment and a modified UFR-based adjustment method using empirically derived coefficients (slopes of analyte concentrations as a function of UFR) generally performed better than creatinine, excretion rate and bodyweight-adjusted excretion rate methods. The findings demonstrated the analyte specific nature of adjustment methods, their misuse in the literature and suggested a pathway to a more robust adjustment framework. Prolonged exposure to As from PWS was identified by the stability of 127 drinking water As concentrations measured up to 31 months apart. Drinking water As concentrations were correlated with those measured in toenails (Pearson's r: 0.53; n=200) and hair (Pearson's r: 0.38; n=104). The successful elimination of external contamination of toenail samples was indicated by low As concentrations in final-stage rinse solutions (geometric mean contribution: 0.4 %). A positive association between seafood consumption and toenail As and a negative association between home-grown vegetable consumption and hair As was observed when As in drinking water was < 1 As μg/L. Elevated As concentrations measured in residential soil (12-992 mg kg-1; n=127) and household dust (3-1079 mg kg-1; n=99), particularly on mineralised geological domains and in the vicinity of former As mining sites, were indicative of additional As exposure routes. Bioaccessibility-adjusted assessment criteria of 190 (13 % bioaccessibility) and 129 (23 % bioaccessibility) As mg kg-1 were derived and 10 and 17 % of residential soils were in exceedance, respectively. The relative importance of different exposure routes in the study region, namely whether As intake from soil and dust is evident in the study population, will form the basis of further work. This will be addressed using multivariate analyses of drinking water, soil and dust in conjunction with urine, toenail and hair As concentrations.
Supervisor: Polya, David ; Pan, Jianxin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: arsenic ; biomonitoring ; exposure ; monitoring