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DIETARY EXPOSURES OF YOUNG CHILDREN, PART 3: MODELLING
Citation:
Hu, Y., G G. Akland, E. D. Pellizzari, C. A. Clayton, L J. Melnyk, AND M R. Berry Jr. DIETARY EXPOSURES OF YOUNG CHILDREN, PART 3: MODELLING. Presented at ISEA Annual Meeting, Monterey, CA, October 24-27, 2000.
Impact/Purpose:
The purpose of this research is to reduce uncertainties in exposure assessments of young children by improving EPA's ability to measure exposures in the context of aggregate and cumulative exposure assessments. The general objective of this research is to support FQPA children's exposure assessment efforts by improving procedures and reducing uncertainty in measurements for dietary exposure of young children, a critically needed area for improved risk assessment. Specifically, this research will evaluate a protocol and companion model for measuring or otherwise assessing the combined dietary intake of a young child as influenced by pesticides, or other environmental contaminants, which contaminate their foods during the eating process (indirect ingestion exposure). This research will continue to develop the important factors which are needed to characterize excess intake of pesticides by young children. Specifically, the research will measure pesticide surface transfer efficiencies for food contacts with surfaces and eating activity patterns of young children that define the frequency of contacts with contaminated surfaces. A series of reports/products are anticipated by the end of FY05.
Description:
A deterministic model was used to model dietary exposure of young children. Parameters included pesticide residue on food before handling, surface pesticide loading, transfer efficiencies and children's activity patterns. Three components of dietary pesticide exposure were included: the amount of pesticide in foods before handling, amount transferred from contaminated surface to foods, and amount transferred from contaminated hands to foods. Monte Carlo sensitivity analysis was performed to identify the most sensitive parameters and to guide laboratory studies and a field study of 3 children from homes that recently applied diazinon. Sensitivity analysis indicated the most sensitive parameter was surface pesticide loading, followed by surface-to-hand transfer and pesticide residue on food consumed. Transfer efficiencies estimated in laboratory experiments were in range of 0-80% for various tested surfaces and foods. These estimates were applied in the model to provide a preliminary assessment of dietary pesticide exposure. The modeling results indicated that pesticide transfer to food caused by contact with surfaces and handling could increase the pesticide intake significantly. Depending on a child's behavior pattern while eatring, food type and surface type, a child's handling of food can contribute >40% of excess pesticide intake. These results were evaluated in a field study in which environmental and biologcial measuement samples were collected. The validity of the model prediction was examined n two ways: by comparison of pesticide in leftover handled foods as predicted by the model and actual field measurements; and by comparison of overnight urinary diazinon metabolite after exposed and unexposed days. also included analysis of the model uncertainty using Monte Carlo method, and limitations associated with the pilot field study for model validation.