Migrant farmworkers in northwestern Mexico, a vulnerable population lacking in surveillance and resources, are subjected to strenuous working conditions including extreme heat and high pesticide exposures.The objective of this pilot study was to assess if there are differences in pesticide exposure as a function of heat stress and hydration levels in summer versus winter seasons. The specific goals of this project were to: 1)determine the association between internal and external permethrin exposure by
exposure route during winter and summer; 2) determine the difference in heat stress and hydration levels in winter and summer; and 3) compare the relationship between heat stress and hydration levels with permethrin exposure in summer versus winter season. Samples were collected from 10 individuals working on a large grape farm; ten working during the winter season and the same ten individuals during the summer season. Personal air and dermal wipe samples from farmworkers conducting similar tasks during winter and summer were collected and analyzed for permethrin. Urine samples were analyzed for a permethrin metabolite, creatinine and specific gravity. Skin and core temperatures were administered to determine hydration levels, and standardized observational assessments were conducted to record: water intake, clothing, personal protective equipment, and job tasks for determining metabolic rate. This project resulted in a better understanding of the interaction between heat stress and pesticide exposure. This data will be used to conduct a larger study and design interventions for reducing pesticide exposure under extreme heat conditions.