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MODELED RESIDENTIAL CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN VIA DERMAL SURFACE RESIDUE CONTACT AND NON-DIETARY INGESTION
Citation:
Zartarian, V, A H. Ozkaynak, J M. Burke, M J. Zufall, E J. Furtaw Jr., E A. CohenHubal, AND L S. Sheldon. MODELED RESIDENTIAL CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN VIA DERMAL SURFACE RESIDUE CONTACT AND NON-DIETARY INGESTION. Presented at ISEE/ISEA '99 Conference, Athens, Greece, September 5-8, 1999.
Description:
A physically-based stochastic model has been applied to estimate residential chlorpyrifos exposure and dace to children via the non-dietary ingestion and dermal residue contact pathways. Time-location-activity data for 2825 children were sampled from national surveys to generate a population of simulated children. For each individual, a sequence of objects contacted was generated probabilistically for every location-activity combination, based on available microlevel) videotape data of children, yielding daily sequential activity profiles in 5 second increments. Based on a literature review, probability distributions were assigned to residue concentrations for each object, surface-to-skin residue transfer efficiency, saliva and water removal efficiency, and skin surface area contacted. The daily activity time profiles were combined with concentrations and exposure factors to yield daily profiles of dermal loading versus time, which were entered into a new dermal uptake model. Monte Carlo sampling was applied to produce estimates of dermal and non-dietary ingestion exposure and dose distributions for young children.
Exposure and dose by age-gender category are presented. Resulting daily averages of intake dose are compared to concentrations in urine of 3,5,6-trichioro-2-pyridinol (TCP), a metabolite of chlorpyrifos, measured in children in EPA's NHEXAS. A sensitivity analysis reveals that more data are needed on transfer and removal efficiencies, surface area contacted, and duration and frequency of objects contacted. This first generation residential exposure modeling approach will soon be extended to aggregate exposure and rinse over all routes and pathways.