Evaluation of biomarkers of arsenic exposure from well water in two rural Nova Scotian communities
LE3 .A278 2011
Bachelor of Science
Well water is one of the most common sources of chronic exposure to inorganic arsenic, a recognized human carcinogen. Rural well waters in Nova Scotia have amongst the highest arsenic concentrations in Canada, in part due to the natural enrichment from the local bedrock and soils. In order to assess whether arsenic concentrations in well water are a principle exposure hazard, the arsenic concentrations of well waters were compared with human urine, hair, fingernail, and toenail biomarkers using a minimum hypergeometric probability (MHP) statistical method. Samples were collected from wells (108) and participants (179) in Waverley and Hubbards, Nova Scotia. Speciation of arsenic by high performance liquid chromatography – inductively coupled plasma – mass spectrometry indicated that As(V) was the dominant species in most well water samples. Arsenobetaine and DMA(V) were the most common species in urine, indicating that the metabolism of arsenic may be more complicated than previously reported. The MHP for each biomarker was identified using a range of well water arsenic concentration thresholds. Elevated concentrations of arsenic in toenails (1.25 μg g-1) and hair (0.437 μg g-1) exhibited the best correspondence with well water samples containing > 60 μg L-1 of arsenic. The prediction errors (false-positives and false-negatives) were 7.0 % and 6.6 % for toenails and hair, respectively. These MHP results reflected the most non-random outcome at each well water arsenic concentration threshold, and thus identified the greatest cause-and-effect relationship amongst these variables whilst minimizing classification errors.
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