Bioavailability of Lead to Juvenile Swine Dosed with Soil from the Smuggler Mountain NPL Site of Aspen, Colorado

Bioavailability of lead (Pb) has become an issue in quantifyingexposure of sensitive populations and, where necessary, establishingcleanup levels for contaminated soil. Immature swine were usedas a model for young children to estimate the degree to whichPb from two fully characterized composite samples from the SmugglerMountain Superfund Site in Aspen, Colorado may be bioavailableto resident children. The composite soils contained 14,200 and3870 µg Pb/g of soil. Relative and absolute enteric bioavailabilitiesof Pb in soil (oral dose groups of 75,225, and 675 µgPb/kg body wt/day) were estimated by comparison with an orallyadministered soluble Pb salt (lead acetate = PbAc₂·3H₂O)(dose groups of 0, 75, and 225 µg Pb/kg body wt/day) andan intravenously administered aqueous solution of Pb (100 µgPb/kg/day) from the same trihydrate salt administered dailyfor 15 days to 50 juvenile swine. The biological responses (areaunder the blood Pb concentration-time curve, and the terminalliver-, kidney-, and bone-lead concentrations) produced by Pbfrom PbAc₂·3H₂O and lead-contaminated soils were determined.This study revealed Pb from soil containing 14,200 µgPb/g of soil had a bioavailability relative to Pb from PbAc(RBA), ranging from 56% based on the area under the blood leadconcentration-time curve (AUC) versus dose, to 86% based oncalculations from liver- Pb loading versus dose. Similarly,Pb from soil containing 3870 µg Pb/g of soil had an RBAranging from 58% based on the AUC versus dose, to 74% basedon calculations from liver- and kidney- Pb loading versus dose.Bioavailability of Pb in soils may be more or less than EPA'sdefault RBA of 60%, therefore, measuring site- specific RBAsprovides a basis for improved exposure and risk assessment.