Arsenic tissue concentration of immature mice one hour after oral exposureto gold mine tailings

A potentially high bioavailability of arsenic in gold mine tailings from a site in northern California has been suggested by solubility studies. To he lp address this issue, an in vivo dosing study was conducted using 12-day-o ld Swiss Webster mouse pups (n=8/group). A sample of size-fractionated mine tailings from the site (< 20 mu m particle size, 691 mu g g(-1) arsenic) w as prepared as an aqueous suspension and administered by gavage in a volume that provided 4 mg As/kg body weight. The control group received the same volume of a commercial soil (1 mu g g(-1) As) of similar particle size (< 6 0 mu m). No mortality or toxic signs were noted in either group. Tissue sam ples were collected 1 h after gavage, freeze-dried, microwave-digested and analysed for arsenic by ICP/MS (detection limit 2 ng As g(-1) dry weight). Arsenic concentrations (ng As g(-1) dry weight) in tissues from the pups wh o received mine tailings were significantly higher than in control tissues. The mean elevation in arsenic concentration was highest in the liver (3364 % of control, p < 0.0001), followed by blood (818 of control, p < 0.0001), skin (207% of control, p=0.07), and brain (143% of control, p < 0.0001). Th e carcass arsenic concentration (excluding the GI tract, liver, brain and s kin) was 138 of control (p=0.02). The data indicate uptake of arsenic from weathered mine tailings by the immature mouse pups after oral exposure.