The report summarizes relevant information on multi-media lead exposure and presents the modeling methodologies that EPA staff believes should be considered for the review of the national ambient air quality standards for lead. Results of validating one of these methodologies are also presented. The significant downward trends in gasoline lead emissions and lead concentrations in the diet are accounted for in these methodologies. Young children, pregnant women (as exposure surrogates for the fetus), and middle-aged men are identified as particularly susceptible to lead. Three different exposure methodologies, developed from a wide variety of data are described: the uptake/biokinetic and aggregate air lead models, both applicable to young children, and the disaggregate air lead model, which is applicable to both young children and adults. The uptake/biokinetic model allows explicit projections of future lead concentrations in different media and in turn can estimate the impacts of these changes on different age groups of children. It is this flexibility that makes the uptake/biokinetic model adaptable for a wide range of predictive exposure assessments and why it was the focus of the validation exercises described in the paper. Results of these exercises indicate good concordance between predicted and observed blood lead levels in children living near different lead point sources.

"June, 1989." "EPA/450-2-89-011." "OAQPS staff paper."