"EVERYTHING BUT THE KITCHEN SINK": EXPOSURE TO ARSENIC FROM BATHING AND OTHER INDIRECT WATER PATHWAYS
Andrew E. Smith
Environmental Toxicology Program, Bureau of Health, Department of Human Services, State of Maine, Augusta, ME, 04333.

An estimated 10 percent of Maine households have arsenic levels in well water above the recommended guideline of 10 ug/L. The most commonly selected technology to reduce exposure to arsenic from household well water is point-of-use treatment. These treatment systems are typically installed at the kitchen sink, leaving water elsewhere in the house untreated. This approach is predicated on the assumption that bathing and other indirect exposures are negligible. The purpose of this talk is to review the available studies that can be used to place bounds on the magnitude of exposures from bathing and other indirect pathways. In-vivo studies with monkeys and rats, and -in-vitro studies with human and mouse skin have demonstrated that arsenic can be dermally absorbed. Dutkiewicz (1973) using an in-vivo rat tail exposure model and Rahman et al. (1994) using an in-vitro mouse skin diffusional-cell model reported estimates of dermal absorption of arsenic from water that can be used to estimate dermal permeability coefficients ranging from 0.0015 to 0.0021 cm/hr. These values are similar to those reported for other inorganics. Use of these permeability coefficients with a USEPA (2001) model for estimating dermal uptake of inorganics from water predicts exposures ranging from 1 to 7 ug As for a child from a half-hour bath in water with 100 to 1000 ppb, respectively. Harrington et al. (1978) reported data on urine arsenic levels from a survey of populations exposed to high and low concentrations of arsenic in well water. Average urinary arsenic levels were nearly identical for a group who had high arsenic water (mean of ca. 500 ppb) and used bottled water, as compared to a group who drank well water containing on average 11 ppb. Though limited, these data from studies of dermal absorption and community surveys indicate that indirect water exposures are small relative to direct ingestion from drinking and beverage preparation. These studies do not however, demonstrate that these secondary exposures are always negligible. Nor do these studies specifically evaluate children as a population that may have increased exposure due to play-related behavior during bathing. For these reasons, the Bureau of Health, in conjunction with the U.S. CDC, has undertaken a study of to measure the extent of arsenic intake among adults and children who live in homes with high-arsenic well water, but use low-arsenic alternatives for drinking. This study is ongoing and in the middle of its data collection phase. hese aquifer materials, geochemical conditions generally are not favorable for dissolution of HFO and other iron oxides.