Characterization of Organophosphate Pesticides in Urine and Home Environment Dust in an Agricultural Community

Thesis (Master's)--University of Washington, 2016-06

Background: Organophosphorus insecticides (OPs) are used widely on crops to control agricultural pests, but they can have harmful effects on humans. Farmworkers have higher exposure to OP pesticides than non-farmworkers living in the same community, due to their occupational exposure, and there is concern that farmworker children may in turn have higher exposure to OPs than non-farmworker children. Methods: A community-based participatory research strategy was used in the Lower Yakima Valley of Washington state to identify 100 farmworker (FW) and 100 non-farmworker (NFW) adults, each with a referent child between the ages of 2 and 6 years. Farmworker adults worked as thinners or harvesters in apple or pear orchards. Parents and children participated in three data collection periods over the course of a year: three urine samples within five days were provided for each collection period, homes were vacuumed once each collection period, and vehicles were vacuumed once during two of the collection periods. Urine was evaluated for the dialkylphosphate metabolites (DAP) characteristic of OP exposure, and dust was evaluated for intact OP residues. Results: The geometric mean (GM) concentrations in house dust of four commonly used agricultural OPs were higher in farmworker households than in non-farmworker households across all three agricultural seasons. Farmworker households had higher GM concentrations of OPs in vehicle dust than non-farmworker households in thinning season, when OPs are applied most intensively. The GM concentration of urinary DAP was higher for children in farmworker households than non-farmworker households during thinning season. Regression analysis of log-transformed variables found a positive correlation between children’s urinary DAP and OP residues in house dust in thinning season. Conclusions: GM concentrations of OPs in house dust and vehicle dust were higher in farmworker households than non-farmworker households, especially in thinning season. OPs in house dust were a significant factor affecting the children’s urinary DAP levels. This relationship was most significant during thinning season and was not observed during the dormant, non-spray season. These results provide support for the occupational take-home pathway of exposure by which children are exposed to agricultural pesticides used in the workplace.