An Updated Evaluation of Atrazine-Cancer Incidence Associations among Pesticide Applicators in the Agricultural Health Study Cohort.

BACKGROUND: Atrazine is a common agricultural herbicide in the United States. Few epidemiologic studies have evaluated cancer risks. Previous analyses within the Agricultural Health Study (AHS) have found some evidence of associations with cancer at some sites.

OBJECTIVE: We updated exposure information, incident cases, and follow-up time to assess the associations between atrazine use and cancer at specific sites in the AHS.

METHODS: Information about lifetime pesticide use was reported at enrollment (1993-1997) and follow-up (1999-2005). Among 53,562 pesticide applicators in North Carolina and Iowa, we identified 8,915 incident cases through cancer registry linkages through 2014 (North Carolina)/2017 (Iowa). We used Poisson regression to evaluate the association between ever/never and intensity-weighted lifetime days of atrazine use and incident cancer risk controlling for several confounders. We also evaluated lagged exposures and age-stratified risk.

RESULTS: Approximately 71.2% of applicators reported ever using atrazine, which was associated with lung cancer [rate ratios (RR)=1.24; 95% confidence interval (CI): 1.04, 1.46]. Aggressive prostate cancer risk was increased in the highest quartile (RRQ4=1.20; 95% CI: 0.95, 1.52; p-trend=0.19), particularly among those <60 years old (RRQ4=3.04; 95% CI: 1.61, 5.75; p-trend<0.001; p-interaction=0.04). Among applicators <50 years of age, ever-atrazine use was associated with non-Hodgkin lymphoma (NHL) (RR=2.43; 95% CI: 1.10, 5.38; p-interaction=0.60). For soft tissue sarcoma, there was an elevated risk in the highest tertile of exposure (RRT3: 2.54; 95% CI: 0.97, 6.62; p-trend=0.31). In analyses with exposure lagged by 25 years, there was an elevated risk of pharyngeal (RRT3=3.04; 95% CI: 1.45, 6.36; p-trend=0.07) and kidney (RRQ4=1.62; 95% CI: 1.15, 2.29; p-trend<0.005) cancers.

DISCUSSION: We observed suggestive associations with some malignancies in overall, age-specific, and lagged analyses. Associations with aggressive prostate cancer and NHL were apparent among those diagnosed at younger ages and with cancers of the pharynx and kidney, and soft tissue sarcomas were observed in lagged analyses. Further work is needed to confirm these observed associations and elucidate potential underlying mechanisms. https://doi.org/10.1289/EHP13684.