Pesticide use and incident hyperthyroidism in farmers in the Agricultural Health Study.

BACKGROUND: Few studies have evaluated associations between pesticides and hyperthyroidism.
OBJECTIVE: We evaluated associations between specific pesticides and incident hyperthyroidism in private pesticide applicators in the Agricultural Health Study.
METHODS: We used Cox proportional hazards models to estimate HRs and 95% CIs for associations between pesticide use at enrolment and hyperthyroidism (n=271) in 35 150 applicators (mostly men), adjusting for potential confounders.
RESULTS: Ever use of several pesticides (organophosphate insecticide malathion, fungicide maneb/mancozeb, herbicides dicamba, metolachlor, and atrazine in overall sample and chlorimuron ethyl among those ≤62 years) was associated with reduced hyperthyroidism risk, with HRs ranging from 0.50 (95% CI 0.30 to 0.83) for maneb/mancozeb to 0.77 (95% CI 0.59 to 1.00) for atrazine. Hyperthyroidism risk was lowest among those with higher intensity-weighted lifetime days of using carbofuran and chlorpyrifos (ptrend ≤0.05).
CONCLUSIONS: Observed associations between pesticides and decreased risk of hyperthyroidism warrant further investigation. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.