An assessment of lead absorption from soil affected by smelter emissions

The purpose of this study was to assess the oral bioavailability of lead in soil collected from a former smelter site in Sandy, Utah, USA. Sprague-Dawley rats (approximately 4 weeks of age, 5 of each sex in group) were given either soil lead or lead acetate mixed in a purified diet (AIN-93G ™) at four different concentrations for 31 consecutive days. Food consumption measurements were used to compute mean daily lead exposures for the soil lead and lead acetate groups. The lead acetate treatment yielded higher concentrations of lead in the blood and bone than the soil lead treatment. Mean blood lead values ranged from below the detection limit (3 μg dL(-1)) to 27.25 μg lead dL(-1) for the lead acetate groups at dose levels of 0.10-2.91 mg lead kg body weight(-1) and from below the detection limit to 8.8 μg lead dL(-1) for the soil lead groups at doses of 0.11-3.43 mg lead kg body weight(-1). At these same doses, mean bone values ranged from 0.52 to 26.92 μg lead g(-1) for the lead acetate groups and from 0.64 to 13.1 μg lead g(-1) for the soil lead groups. Relative per cent bioavailability was estimated by modelling the dose-blood concentration curves for the lead acetate treatment and the dosed soil lead treatment, and then comparing doses that produce an equivalent blood lead concentration. The ratio of the doses of lead acetate and soil lead that produced the same tissue response (i.e., concentration) provided an index of relative bioavailability. For lead, the bioavailability of soil lead relative to lead acetate was 41% at a blood concentration of 6 μg lead dL(-1).