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Approaches usually available for the assessment of exposures that occur via water, land and/or air are limited by their ability to integrate multiroute scenarios. Additionally, there are indications that these exposures can differentially affect specific subgroups, each having unique sensitivities to chemical insults. Lead is one of the major toxic contaminants of concern found at approximately 47% of the Superfund National Priority List (NPL) Sites. Low level exposure to lead has been shown to produce adverse effects on heme metabolism, serum vitamin D levels, mental and physical development of infants and children, and blood pressure in adults. Experimental and epidemiologic studies have indicated that blood lead levels in the range of 10–15 μg/dl, or possibly lower, are likely to produce subclinical toxicity. Since a threshold has not been established it is prudent to assume that, for regulatory purposes, a threshold for lead toxicity does not exist. As an alternate to the traditional reference dose approach, the U.S. EPA has developed the Uptake/Biokinetic Lead Model that provides a means for evaluating the relative contribution of various media to establishing blood lead levels. The model is flexible and versatile and predicts mean blood lead levels and population distributions associated with multimedia exposure in children. This allows for the identification of site- and situation-specific abatement strategies based on projected blood lead levels in vulnerable human populations. This paper will present examples of NPL site exposure scenarios for lead and how the UBK lead model may be used for characterization of potential health risks as a result of these exposure scenarios.
lead, uptake biokinetic model, Superfund National Priority List, reference dose
Toxicologist, U.S. Environmental Protection Agency, Cincinnati, Ohio
Statistician, Battelle Columbus Laboratories, Arlington, VA