Arsenic, As(III), and tungsten in Nevada County's private water supplies.

In parts of the western United States groundwater used for drinking water contains high concentrations of metals, including arsenic. In a rural county in Nevada, USA, we measured concentrations of arsenic and tungsten and the proportion of arsenic occurring in trivalent form (As(^III)) in tap water samples from private domestic wells in 307 households. The proportion of arsenic occurring as As(^III) ranged from 0 to 100% (ave. 21%, median 1%). Tungsten concentrations ranged from 0 to 610 μmg l^-1 (ave. 26 μmg l^-1, median 2 μmg l^-1). Among 253 respondents who consumed water: (a) 177/253 (70%) of tap water samples contained more than 10 μmg l^-1 total inorganic arsenic (ave. 66 μmg l^-1, median 20 μmg l^-1); (b) As(^III) occurred as a small proportion of total arsenic in most samples (ave. 22%, median 3%); and (c) tungsten occurred in concentrations ranging from below the detection limit (3 μmg l^-1) to a maximum of 610 μmg l^-1 (ave. 30 μmg l^-1, median 3 μmg l^-1). Log¹⁰ concentrations of tungsten and total arsenic in consumed water were positively correlated (log¹⁰[W] = 20.400 + 0.703(log₁₀[As^T]), p = 0.000+, adj. r² = 0.53). This suggests that householders in this area were likely to be exposed to both metals simultaneously, given that 253/307 of the respondents (82%) reported consuming tap water. [ABSTRACT FROM AUTHOR]