| The objectives of this thesis were: 1) to determine which factors and biological samples were associated with the estimated amount of total arsenic (As) consumed from water and food; 2) to determine which factors were associated with the concentration of total and speciated As ([As]) in urine; 3) to determine which factors were associated with the total [As] in nails and hair; and 4) to evaluate a novel method of quantifying As in human nails via x-ray fluorescence (XRF).;In 2010, a questionnaire was administered to 179 people from two locations in Nova Scotia, Canada. The questionnaire collected information on participants' eating and drinking habits, and key social and demographic information such as: cigarette and alcohol consumption, length of time in home, household income, etc. Water and biological samples, collected from each participant, were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to quantify the total concentration of As ([As]) and selenium (Se) in each. Total water [As] ranged from <0.02 -- 309.2 mug/L. Total [As] of urine (adjusted by specific gravity, SG), fingernails, toenails, and hair ranged from <0.71 -- 661.11 mu/L from <0.07 -- 2.3 mug/g, from <0.15 -- 4.1 mug/g, and from <0.15 --13.2 mug/g, respectively.;Total urinary [As] was associated with estimated total amounts of As consumed from water and food in the last 3 days. Total fingernail [As] and water pH were also associated with the amount of As consumed from water, and income was associated with food As consumption. The depth of the well used to draw drinking water was associated with water As consumption and total As consumption, especially between the depths of 22 -- 55 m.;High Performance Liquid Chromatography was used to measure arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA(V)), dimethylarsinic acid (DMA(V)), arsenobetaine (AsB), and total urinary arsenic metabolites minus arsenobetaine (TMA), in urine. Total water [As] was a strong positive predictor of all urinary As metabolite concentrations, with the exception of AsB. Consumption of seafood was positively associated with urinary concentrations of total As and AsB, but also As(III), DMA(V), and TMA, suggesting that seafood-derived As may be metabolized in the body to other As metabolites. Both total [As] and [AsB] in urine were found to be slightly higher in older participants. Participants who reported recent consumption of chicken also had slightly increased concentrations of urinary As(V). Finally, a strong positive relationship was found between water pH and MMA(V), DMA(V), and TMA concentrations in urine.;Multiple linear and logistic regression analyses found that water [As] and sample [Se] were predictors of [As] in hair and nails. This finding supports previous research which has found a high degree of interaction between As and Se in humans, which is important to consider when performing an As biomonitoring study.;Evaluation of the XRF found the concordance correlation coefficient and kappa value were highest for fingernail samples of at least 20 mg in mass, but overall, XRF did not compare well to ICP-MS. Using a clinically relevant concentration of 1.0 mug/g on ICP-MS as a cut-off for indicating test positive and test negative samples, the XRF, also using a cut-off of 1.0 mug/g, was found to have 100% sensitivity (95% CI: 48 -- 100%) and negative predictive value (95% CI: 63 -- 100%), however its specificity and positive predictive values were low, at 29% (95% CI: 17 -- 43%) and 19% (95% CI: 8 -- 33%), respectively.;Further research involving urine as a biological marker of exposure to As should take specific urinary As metabolites into consideration and pay special attention to seafood consumption, which can strongly affect urinary [As], and can potentially lead to an increase in toxic inorganic As metabolites. Studies of As in hair or nails should consider the total and relative concentrations of Se in respective samples. More work is needed before the XRF can be considered a suitable replacement for ICP-MS. |
