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BACKGROUND: Private wells throughout Florida have been found to have levels of arsenic above the Maximum Contaminant Level (MCL) of 10µg/L. As part of the Florida Safe Water Restoration Program, these households are provided point-of-use (POU) filters and/or bottled water to reduce their health risk from arsenic consumption. A biomonitoring project was conducted in 2013 to determine if any differences exist in urinary arsenic levels between individuals with well water arsenic above and below the MCL. A secondary objective, and the focus of this analysis, was to determine the relative importance of dietary and water sources of arsenic in this study population.
METHODS: The biomonitoring study included residents with private wells above the MCL of 10µg/L for arsenic in drinking water (cases) and those with wells below 8µg/L (controls). There were 350 participants: 180 (51%) cases and 170 (49%) controls. Participants provided a urine sample and completed a survey on home water use, dietary and other exposures to arsenic, pesticide and herbicide use, tobacco and alcohol use, and occupational risk. Responses were weighted to account for sampling design and within-household participation rates. Analysis of covariance models were used to compare mean creatinine-adjusted arsenic levels by various demographic characteristics and exposures of interest.
RESULTS: Average urinary arsenic levels were not significantly different between cases and controls, and the overall creatinine-adjusted urinary arsenic level geometric mean was 7.99μg/L (95% confidence interval [CI]: 7.35, 8.69). Cases and controls used different sources of water for various activities; cases were more likely to use bottled or filtered well water for drinking, cooking, and brushing teeth (p-values<0.01) compared to controls. Few other significant differences were noted. In adjusted models, higher household income (≥$75,000; p=0.03) and owning the home (vs. renting/other; p<0.01) were significantly associated with higher creatinine-adjusted urinary arsenic levels. Urinary arsenic levels increased as servings of fish, seafood, white rice, and wine increased (p-values<0.01). Similar relationships were seen in a sensitivity analysis excluding individuals who consumed fish or seafood within 3 days of sampling. Again, higher household income, owning the home, and consumption of white rice and wine were associated with higher creatinine-adjusted urinary arsenic levels.
CONCLUSIONS: Provision of POU filters and bottled water to case households seems to provide adequate protection from arsenic exposure through well water. However, other non-water related risk factors were found to significantly contribute to higher urinary arsenic levels among participants, regardless of household case status.