Chemical predictors of wheeze among farmer pesticide applicators in the Agricultural Health Study.

Pesticides may contribute to respiratory symptoms among farmers. Using the Agricultural Health Study, a large cohort of certified pesticide applicators in Iowa and North Carolina, we explored the association between wheeze and pesticide use in the past year. Self-administered questionnaires contained items on 40 currently used pesticides and pesticide application practices.

Potential for selection bias with tumor tissue retrieval in molecular epidemiology studies.

Molecular epidemiological studies of cancer generally require tumor tissue to evaluate somatic genetic alterations. Frequently this requires retrieval of fixed tissue blocks from hospital pathology archives. The availability of this material may be associated with disease severity, diagnostic practices, hospitals, or risk factors for disease.