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ESTIMATING CHILDREN'S DERMAL AND NON-DIETARY INGESTION EXPOSURE AND DOSE WITH EPA'S SHEDS MODEL
Citation:
Zartarian, V. ESTIMATING CHILDREN'S DERMAL AND NON-DIETARY INGESTION EXPOSURE AND DOSE WITH EPA'S SHEDS MODEL. Presented at Society for Risk Analysis, Atlanta, GA, December 5-8, 1999.
Description:
A physically-based stochastic model (SHEDS) has been developed to estimate pesticide exposure and dose to children via dermal residue contact and non-dietary ingestion. Time-location-activity data are sampled from national survey results to generate a population of simulated children. For each child, a sequence of 5 second object contact events is generated probabilistically for every location-activity combination, yielding sequential micro-level activity profiles. These profiles are combined with probability distributions for surface concentrations and exposure factors (e.g., pesticide transfer and removal efficiency, skin surface area contacted) to yield daily time profiles for dermal loading, body burden, and eliminated pesticide metabolite. Population estimates are then generated via Monte Carlo sampling. The SHEDS model has been applied for children aged 0-4 and 5-9 years for six chlorpyrifos application scenarios: broadcast and crack and crevice methods; <1 day, 1-7 day, and 8-30 days post-application. Diary data for 1096 children from the National Human Activity Pattern Survey were combined with videotaped activity data and probability distributions for measured concentrations and exposure factors (based on a literature review). For each application scenario and age group, population estimates of daily eliminated 3,5,6-trichloro-2-pyridinol (TCP), the urinary metabolite of chlorpyrifos, were generated. These modeled results are comparable to measured results from EPA's National Human Exposure Assessment Survey and other studies following broadcast and crack and crevice applications of chlorpyrifos.
This work has been funded wholly or in part by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication.