Children’s Dermal Exposure and Dose: Using an Event-Based Model to Evaluate Measurement Approaches. M. L. Rigas, V. G. Zartarian, E. C. Hubal, and H. Ozkaynak, National Exposure Research Laboratory, US EPA, Research Triangle Park, NC
Dermal exposure to contaminants may be determined by summing a series of discrete transfers resulting from individual contact events with contaminated surfaces. In the case of small children, these events may occur every few seconds. This approach has the potential to lead to accurate assessments of dermal loading for individuals, because it is mechanistically-based. However, for extensions to larger populations where there is greater variability in the contact events, a lumped-parameter approach in which dermal transfer is associated with major activities, or macroactivities (i.e. playing, washing, etc.) may be more applicable. The goal of this work is to examine how the time periods and dermal wipe methods associated with macroactivity measurements affect the estimation of exposure and absorbed dermal dose. We used a simulated event-based dermal loading and associated absorbed dose profile for chlorpyrifos, an organophosphate pesticide, as a surrogate for actual dermal loading measurements. We then mimicked a periodic dermal wipe measurement by sampling from the dermal loading profile at pre-determined time intervals. We were able to determine the error in exposure estimates by comparing these sampled values to the "actual" amount added to the skin as given by the event-base simulation model. We examined the effect of sampling time interval on dose estimation. For example, we determined that if dermal exposure estimates were made at the end of macroactivities that were 30 minutes in length, the relative error in the estimate of body burden of chlorpyrifos did not exceed 20%.
The U.S. EPA funded this research. This abstract has been reviewed and approved for presentation.
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