SOIL PB BIOAVAILABILITY AND DISTRIBUTION IN BURLINGTON, VERMONT: TESTING AND ASSESSMENT OF A GEOSPATIAL PREDICTIVE MODEL

Exposure to Pb causes neurological and behavioral problems in children and triggers kidney and reproductive problems in adults. Lead has limited mobility and historic use of lead paint and gasoline has resulted in high concentrations in urban soils. Old housing stock makes this issue prevalent in Burlington, VT. Based on residential soil data, a predictive geospatial distribution model for Pb in soil was developed for Burlington. It suggested that the EPA guidance limit of 400 ppm for soil lead in residential play areas is too high to prevent dangerous blood lead levels (BLL) for children. Because of these implications, this research aims to test and refine this model.

Focusing on undersampled areas in Burlington, 75 soil samples were acquired and analyzed for total and bioaccessible Pb by XRF and the EPA bioaccessible assay respectively. Integrated Exposure Uptake and Biokinetic (IEUBK) modeling was used to determine the amount of lead that can potentially enter a child’s bloodstream.

New data revealed an important aspect of the relationship between total and bioaccessible Pb in Burlington. Unlike previously accepted, it appears this relationship is nonlinear with a higher proportion of bioaccessible Pb in soils with lower total Pb (62% vs 47%, cutoff at 1,500 mg kg^-1 total Pb). Because BLL estimated by the IEUBK is based on this relationship, it implies that guidance limit values are even lower than previously estimated and should be reassessed locally. Testing of the model is underway and preliminary results suggest that an increase in sampling resolution improves predictive capacity of the model.