Arsenic tissue concentration of immature mice one hour after oral exposure to 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 help address this issue, an in vivo dosing study was conducted using 12-day-old Swiss Webster mouse pups (n = 8/group). A sample of size-fractionated fractionated mine tailings from the site (<20 μm particle size, 691 μg g^-1 arsenic) was 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 μg g^-1 As) of similar particle size (<60 μm). No mortality or toxic signs were noted in either group. Tissue samples 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 who 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). The carcass arsenic concentration (excluding the GI tract, liver, brain and skin) 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.