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 quantifying exposu re of sensitive populations and, where necessary, establishing cleanup levels for contaminated soil. Immature swine were used as a model for young children to estimate the degree to which Pb from two fully char acterized composite samples from the Smuggler Mountain Superfund Site in Aspen, Colorado may be bioavailable to resident children. The compo site soils contained 14,200 and 3870 mu g Pb/g of soil. Relative and a bsolute enteric bioavailabilities of Pb in soil (oral dose groups of 7 5, 225, and 675 mu g Pb/kg body wtlday) were estimated by comparison w ith an orally administered soluble Pb salt (lead acetate = PbAc2 . 3H( 2)O) (dose groups of 0, 75, and 225 mu g Pb/kg body wtlday) and an int ravenously administered aqueous solution of Pb (100 mu g Pb/kg/ day) f rom the same trihydrate salt administered daily for 15 days to 50 juve nile swine. The biological responses (area under the blood Pb concentr ation-time curve, and the terminal liver-, kidney-, and bone-lead conc entrations) produced by Pb from PbAc2 . 3H(2)O and lead-contaminated s oils were determined. This study revealed Pb from soil containing 14,2 00 mu g Pb/g of soil had a bioavailability relative to Pb from PbAc (R BA), ranging from 56% based on the area under the blood lead concentra tion-time curve (AUG) versus dose, to 86% based on calculations from l iver-Pb loading versus dose. Similarly, Pb from soil containing 3870 m u g Pb/g of soil had an RBA ranging from 58% based on the AUC versus d ose, to 74% based on calculations from liver- and kidney-Pb loading ve rsus dose. Bioavailability of Pb in soils may be more or less than EPA 's default RBA of 60%, therefore, measuring site-specific RBAs provide s a basis for improved exposure and risk assessment. (C) 1997 Society of Toxicology.