Integrating exposure measurements into epidemiologic studies in agriculture

Agricultural epidemiology studies frequently rely on questionnaires to assess pesticide exposure. Farmers can provide accurate information regarding their pesticide use history. However, pesticide exposure is influenced not only by the pesticide, but also by factors related to pesticide application and behavior; estimates of exposure can be improved by incorporating data on these factors. Exposure measurement studies help to elucidate influential factors with regard to pesticide dose. These factors can be incorporated into exposure estimates to reduce measurement error and allow for better resolution of the exposure distribution. In the Agricultural Health Study, two exposure algorithms were developed to evaluate exposure intensity; this exposure intensity score was used to modify the lifetime days of pesticide application. This metric, along with additional refinement as a result of on-going field studies, will allow better assignment of exposure levels in the cohort. Future work to develop exposure metrics that incorporate both chemical and behavior characteristics for all farmworkers and farm residents will further improve epidemiologic studies in agriculture.