New Approaches to Temporal Issues in Human Health Risk Assessment. E. M. Faustman, S. M. Bartell, R. A. Ponce, G. van Belle, and W. C. Griffith, Department of Environmental Health, University of Washington, Seattle, WA
As a factor affecting both exposure and potency, considerations of time are often some of the most difficult to evaluate in risk assessments. Such considerations include time of life, latency, and duration of exposure. Often, the use of the biomarker data to predict historic exposures relies on assumptions regarding exposure patterns over time. One assumption that is commonly made is the assumption of steady-state. To explore the impact of time considerations in exposure estimation, we examine how variability in non-steady state exposures may alter the interpretation of biomarker information using dietary mercury as an example. Blood mercury analysis can be considered to be a pooled sample most highly reflecting recent exposure. Hair Hg analysis, however, can be considered to be an integrator reflecting blood Hg concentrations at the time of hair growth. Using a physiologically-based pharmacokinetic model accounting for variability in model parameters, we demonstrate that considerations of changing dietary patterns have substantial implications for improving the design of sampling strategies for estimating historical exposure. We discuss the role of model variability and dietary pattern in the interpretation of biomarkers.
Supported by CRESP through Department of Energy cooperative agreement #DE-FC01-95EW55084.
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