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Modeling Inhalation and Multimedia Multipathway Human Exposures to Environmental Pollutants

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Abstract: Estimation of exposures of children and adults to air toxics or multimedia pollutants require careful consideration of sources and concentrations of pollutants that may be present in different media, as well as various routes and pathways of exposures associated with age-specific activities of individuals. In recent years, a number of probabilistic inhalation or aggregate exposure models have been developed by various researchers for estimating exposures to selected chemicals from different routes and pathways. Cumulative exposure models, dealing with aggregate exposures from more than one chemical are, however, still mostly in the developmental stage. The EPA's Office of Research and Development (ORD), National Exposure Research Laboratory (NERL) has developed a probabilistic model (Stochastic Human Exposure and Dose Simulation Model, or SHEDS) that predicts the variability in the distribution of personal exposures and doses within a population cohort, as well as the uncertainty in the model estimates. The SHEDS model framework has initially been developed to study general population exposures to fine Particulate Matter (PM2.5) and children's exposure to pesticides. At the present, the SHEDS-Pesticides models include the inhalation and dietary ingestion routes in addition to dermal contact and non-dietary ingestion. SHEDS-PM (i.e., particulate matter and its associated constituents) and SHEDS-ATOX (i.e., air toxics) models, which are currently either being refined or developed, use the same modeling approach as the SHEDS-Pesticides model, however the primary focus is on inhalation exposure and dose. A user-friendly interface has been developed for the aggregate SHEDS-Pesticides and SHEDS-PM model with both exposure researchers and regulators in mind as potential users. SHEDS and other aggregate or cumulative pesticide exposure models still need rigorous evaluation and independent verification against carefully designed field studies. All of the exposure models suffer from limitations of available input information on critical exposure factors, especially for children. In general, models need to identify which inputs or parameters are of special concern for future model refinements or further sensitivity analysis. This information will in turn assist the design of future field exposure and biomonitoring studies that will be used in refining or evaluating the current exposure models. In order to develop more robust models with more complete input data, repeated or longitudinal concentration or residue measurements, time-activity data, and frequency of chemical-specific product use information in homes, day care centers/schools, commuting and other important microenvironments are also needed. Finally, the form of model outputs that are most useful to regulatory and scientific agencies and to the public also needs to be identified.

This work has been wholly funded by the United States Environmental Protection. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
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Citation:Ozkaynak, A. H. Modeling Inhalation and Multimedia Multipathway Human Exposures to Environmental Pollutants. Presented at The American Chemistry Council Long Range Research Initiative Annual Science Meeting, Herndon, VA, June 24-25, 2003.
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Immediate Office
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Product Type: Abstrct/Oral
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Presented: 06/24/2003
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Related Entries:
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Bullet Item Population Exposure and Dose Modeling for PM and Its Components
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