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QUANTIFYING AGGREGATE CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN USING A PHYSICALLY-BASED TWO-STAGE MONTE CARLO PROBABILISTIC MODEL
Citation:
Zartarian, V, A H. Ozkaynak, AND J. Xue. QUANTIFYING AGGREGATE CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN USING A PHYSICALLY-BASED TWO-STAGE MONTE CARLO PROBABILISTIC 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:
To help address the Food Quality Protection Act of 1996, a physically-based, two-stage Monte Carlo probabilistic model has been developed to quantify and analyze aggregate exposure and dose to pesticides via multiple routes and pathways. To illustrate model capabilities and identify data needs, a case study for young children and chlorpyrifos was conducted. Three post-application time periods (<1,1-7, 8-30 days) were considered for indoor residential crack and crevice applications and outdoor liquid and granular turf applications. Inhalation, dietary ingestion, dermal contact, and non-dietary ingestion routes were considered for a population of children simulated using time-location-activity diaries from the National Human Activity Pattern survey. Model outputs include graphical and tabular displays of: individuals' route-specific and aggregate daily exposure and dose profiles of exposure, absorbed dose, and eliminated dose; route-specific and aggregate population distributions; contributions to population absorbed dose by route and pathway; uncertainty analyses for the modeled populations; and sensitivity analyses reporting model inputs contributing most to variability. The case study results indicate that dermal contact and non-dietary ingestion are the most important routes for shorter post-application time periods (<7 days), while inhalation and dietary ingestion are important for longer time periods post-application (>7 days). Despite current data limitations and model assumptions, the case study predicts exposure and dose estimates that compare well to measurement studies, and provides insights to the relative importance of exposure routes and model inputs.
This work has been funded wholly by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication.