Student Research: Golan Kedan

Comparison of Estimated Aggregate Exposure to Organophosphorous Pesticides with Biomonitoring for Urinary Diakylphosphate Metabolites Among Children
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Children are potentially exposed to pesticides through multiple pathways which are not currently well understood. For this study, 13 homes with children between the ages of 2-5 years old were monitored for organophosphate pesticides (OPs) in soil, indoor air, household dust, and on toy surfaces. Hand wipes, a diet sample and multiple urine samples were also collected from one child within each of these homes. Urine samples were analyzed for dialkylphosphate (DAP) metabolites of OPs. The children in this study, representing two different locations in Washington State (rural and suburban), were targeted for having potentially elevated OP exposures. The initial sampling took place in the summer of 1998 with repeat sampling in the fall to measure possible seasonal effects. Urine samples were collected over a 24 hour period following the collection of a 24 hour diet to sample to reflect the relatively rapid metabolism of OPs. Organophosphorous pesticides were found in all of the homes sampled, most commonly in the indoor air (92%) and household dust (82%). For the children's diets, OPs were determined in 18% of the samples. Multiple OPs were found in 29% of the environmental samples. All of the children also had detectable urinary DAP levels. Some differences were found in the specific OPs detected among the two populations including a higher frequency of agricultural use OPs in the rural homes. The environmental and dietary samples, however, were not found to correlate with the observed urine metabolite levels among the children. Further, an attempt to model DAP excretion based on OP levels in the environmental and dietary samples resulted in an under-prediction of exposure levels by approximately two orders of magnitude. This finding suggests either a missing pathway not considered in this exposure assessment (e.g. dermal absorption), or a misrepresentation of OP exposure inherent in either the environmental, dietary or biological monitoring methods.