PROJECT SUMMARY Chronic low-dose exposure to agricultural pesticides is widely accepted as a fundamental health threat to farmworkers. Unfortunately, delineating sources of variation in pesticide exposure among farmworkers and the long-term consequences of pesticide exposure is hampered by measurement challenges, particularly the absence of an easy, nonintrusive strategy for pesticide biomonitoring. Sweat patches offer a compelling alternative for assessing exposure to pesticides in field studies. Evidence indicates that pesticide metabolites are found in sweat, and sweat patches are being used routinely now in drug monitoring studies. The goal of this interdisciplinary study is to determine the feasibility of using sweat patches for biomonitoring pesticide exposure among Latino farmworkers. We will test the hypothesis that sweat patch sampling will allow for sensitive and consistent measurements with a high rate of compliance. The aims of this feasibility study are to: 1) develop and assess the accuracy and precision of laboratory techniques used to measure pesticides and their metabolites extracted from sweat patches and 2) determine the levels and variance in concentrations of pesticides and metabolites obtained from sweat to those obtained from urine. A secondary aim is to document challenges and problems experienced by farmworkers in using (e.g., opening, applying, wearing removing, and storing) the sweat patches. Advantages of sweat patches to traditional urine screening include the patch being noninvasive, showing increased compliance, and reducing financial cost for future research in this field. Our proposed work involves a combination of both laboratory and field procedures, and the subsequent integration will result in a highly translational project with substantial occupational health impact.