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ASSESSING RESIDENTIAL EXPOSURE USING THE STOCHASTIC HUMAN EXPOSURE AND DOSE SIMULATION (SHEDS) MODEL
Citation:
Zartarian, V, A H. Ozkaynak, AND J. Xue. ASSESSING RESIDENTIAL EXPOSURE USING THE STOCHASTIC HUMAN EXPOSURE AND DOSE SIMULATION (SHEDS) MODEL. Presented at 11th Annual Meeting of the International Society of Exposure Analysis, Charleston, SC, November 4-8, 2001.
Impact/Purpose:
The primary objective of this research is to produce a documented version of the aggregate SHEDS-Pesticides model for conducting reliable probabilistic population assessments of human exposure and dose to environmental pollutants. SHEDS is being developed to help answer the following questions:
(1) What is the population distribution of exposure for a given cohort for existing scenarios or for proposed exposure reduction scenarios?
(2) What is the intensity, duration, frequency, and timing of exposures from different routes?
(3) What are the most critical media, routes, pathways, and factors contributing to exposures?
(4) What is the uncertainty associated with predictions of exposure for a population?
(5) How do modeled estimates compare to real-world data?
(6) What additional human exposure measurements are needed to reduce uncertainty in population estimates?
Description:
As part of a workshop sponsored by the Environmental Protection Agency's Office of Research and Development and Office of Pesticide Programs, the Aggregate Stochastic Human Exposure and Dose Simulation (SHEDS) Model was used to assess potential aggregate residential pesticide exposures for pesticide products that could be used indoors (crack and crevice scenarios) and outdoors (lawn and vegetable garden scenarios). The scenarios simulated for the workshop address applicator and post-application exposures and absorbed doses, via the inhalation, dermal and oral routes, for adults and children to two anonymous pesticides over various toxicologically relevant time frames (e.g., acute, short-term, and intermediate post-application times; and seasonal and annual averages). Using a 2-stage Monte Carlo simulation approach, SHEDS predicts distributions of both variability and uncertainty for the entire US population and for the sub-population living in homes where pesticides are used. Model outputs include: individuals' route-specific and aggregate exposure and dose profiles (daily and annual) of exposure, absorbed dose, and eliminated dose; route-specific and aggregate population boxplots and cumulative density functions (cdfs); pie charts indicating contributions to population absorbed dose by route and pathway; uncertainty analyses for the modeled populations; and sensitivity analyses reporting significant model inputs. This case study allows for prioritization of data needs to improve and apply aggregate exposure models, comparison of route- and pathway- specific doses, and identification of strengths and limitations of the SHEDS model for predicting adults' and childrens' exposures to pesticides.
This work has been funded wholly by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication.