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ASSESSING CHILDREN'S EXPOSURES: ISSUES, APPROACHES AND PLANS
Citation:
Ozkaynak, A H. ASSESSING CHILDREN'S EXPOSURES: ISSUES, APPROACHES AND PLANS. Presented at 2002 Annual Meeting of the International Life Sciences Institute (ILSI), Cancun, Mexico, January 19-24, 2002.
Impact/Purpose:
The primary objective of this research project is to develop a scientifically-robust, complete multimedia, multi-pathway human exposure source-to-dose modeling system with modules and computational tools that can estimate exposures and doses to the general population, as well as to identifiable susceptible subpopulations, and can predict and diagnose the complex relationships which exist between source and exposure and dose -- and to ensure that this scientifically sound model, with its associated tools and the various modules included within, meets the needs of Program Offices and the scientific community for conducting risk assessments.
Description:
Estimation of exposures of children to pesticides requires careful consideration of sources and concentrations of chemicals that may be present in different environmental media and in foods and beverages consumed by children, as well as the different routes and pathways of exposures specific to daily activities of children of different ages. In order to understand better the processes that may contribute to higher exposures and risks to children from pesticides and other persistent pollutants, the National Exposure Research Laboratory (NERL) at U.S EPA's Office of Research and Development (ORD), began conducting a number of field studies. These studies have now collected substantial data on: indoor (residential and daycare) and outdoor pollutant and residue concentrations; personal exposures and biomarker levels in urine; dermal and ingestion transfer coefficients, and; young children's activities and behaviors that could influence their exposures to pesticides and toxic chemicals. In parallel with the measurement program, NERL has also developed a state-of-the-art probabilistic model (Stochastic Human Exposure and Dose Simulation Model, or SHEDS) that predicts the range and distribution of aggregate personal exposures and doses within a population as well as the uncertainty in the model estimates. The model framework has been developed with an initial case study for an organophosphate pesticide and the population of young children. The SHEDS model can simulate an individual's multimedia multipathway exposures up to a year time frame, accounting for multiple pesticide applications in the residential environment. Future versions of the SHEDS model will include more complete characterization of pesticide dose and metabolite concentrations in the body by coupling SHEDS to NERL's Exposure Related Dose Estimating Model (ERDEM). SHEDS and other models currently suffer from limitations of available input information on critical exposure factors for infants and young children, especially dermal and non-dietary transfer efficiencies or coefficients by activity type, location, surface and contact characteristics. In order to develop more robust models with more complete input data, repeated or longitudinal pesticide and other toxic chemical concentration measurements, time-activity data, and frequency of chemical product usage information in homes, day care centers and schools are also needed. Recently, a large-scale interagency program in the US, called the National Children's Health Study (NCS), has also been initiated to investigate the basic mechanisms of neurodevelopmental disorders and environmental factors that influence health and developmental processes of children. This study will identify about 100,000 children across the United States as early in the Mother's pregnancy as possible, then follow them through birth, childhood, and into adulthood. EPA will be responsible for designing the exposure assessment component of the study, likely to include measurement of indoor and outdoor concentrations, personal exposures and biomarker levels for a variety of pollutants, including combustion products and 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.