Estimation of Childhood Soil Ingestion Rates Using a Probabilistic Toxicokinetic Lead Model. S. M. Bartell, University of Washington Institute for Risk Analysis and Risk Communication, Seattle, WA; J. H. Shirai, C. H. Pierce, and J. C. Kissel, University of Washington Department of Environmental Health, Seattle, WA
One of the most controversial parameters in childhood exposure models is the soil ingestion rate. Experimental estimates are usually determined from tracer studies, in which aluminum, silicon, titanium, and other rare earth elements are measured in the diet, urine, and feces. Steady state conditions are assumed, and mass balance approaches are used to estimate the rate of soil ingestion. Soil ingestion rate estimates derived in these studies vary by several orders of magnitude, appear to fluctuate daily for each monitored individual, and are highly dependent on the tracer and statistical model selected. An alternative to the tracer study is the use of pollutant biomonitoring studies which include environmental measurements. We have obtained data from one such study, the Urban Soil Lead Abatement Demonstration Project (USLADP), in which children’s blood lead concentrations were monitored for two years following the replacement of contaminated yard soil with soil with lower lead content. A perturbation analysis is presented using a simplified toxicokinetic lead model to estimate a soil ingestion rate for each child in the USLADP study. The model includes a probabilistic uncertainty analysis component which assesses the impacts of toxicokinetic parameter uncertainty on each child’s estimated soil ingestion rate.
Sponsored by the National Research Center for Statistics and the Environment by Environmental Protection Agency Cooperative Agreement CR-825173-01-4 and by the Consortium for Risk Evaluation with Stakeholder Participation by Department of Energy Cooperative Agreement DE-FCO1-95EW55084.
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