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MODELING AGGREGATE EXPOSURE AND DOSE OF CHILDREN TO A WOOD TREATMENT PRESERVATIVE FROM PLAYSETS AND HOME DECKS
Citation:
Zartarian, V, J Xue, W. Dang, A H. Ozkaynak, N. Cook, D. Aviado, AND S. Mostaghimi. MODELING AGGREGATE EXPOSURE AND DOSE OF CHILDREN TO A WOOD TREATMENT PRESERVATIVE FROM PLAYSETS AND HOME DECKS. Presented at International Society of Exposure Analysis 2002 Conference, Vancouver, Canada, August 11-15, 2002.
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:
Pressure- or non-pressure- treated lumber may pose a potential health hazard to children if the children contact certain chemicals in soils around leaching wood structures and/or in dislodgeable residues that may form on the wood surfaces of the structures. A physically-based, Monte Carlo probabilistic model (SHEDS: Stochastic Human Exposure and Dose Simulation model) has been applied to assess the exposure and dose of 1 to 6 year-old children to a wood treatment preservative from contact with playsets and home decks. Three exposure time periods were considered: short-term (one day to one month), intermediate-term (one month to six months), and lifetime (6 years over a 75 year lifetime). Dermal contact with and ingestion of the chemical in both soil and wood residues were considered for a population of children simulated using time-location-activity diaries from EPA's Consolidated Human Activity Database (CHAD). Model outputs for both warm weather and cold weather scenarios include graphical and tabular displays of individuals' route-specific and aggregate exposure and absorbed dose time profiles, route-specific and aggregate population distributions, contributions to population absorbed dose by exposure pathway, and a sensitivity analysis reporting model inputs contributing most to variability. The findings from this case study include: (1) predicted total absorbed doses from decks and playsets are similar in magnitude; (2) predicted total absorbed doses are greater in warm weather than in cold weather; and (3) ingestion of and dermal contact with wood residues contribute more to predicted dose than from contact and incidental ingestion of soil for all of the averaging times analyzed. Despite current data limitations and model assumptions, the case study provides insights to the relative importance of exposure routes and model inputs for the wood treatment exposure scenario for children.
This work has been funded wholly by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication.