Use of acetochlor and cancer incidence in the Agricultural Health Study

Abstract

Since its registration in 1994 acetochlor has become a commonly used herbicide in the US, yet no epidemiologic study has evaluated its carcinogenicity in humans. We evaluated the use of acetochlor and cancer incidence among licensed pesticide applicators in the Agricultural Health Study. In telephone interviews administered during 1999-2005, participants provided information on acetochlor use, use of other pesticides and additional potential confounders. We used Poisson regression to estimate relative risks (RR) and 95% confidence intervals (95% CI) for cancers that occurred from the time of interview through 2011 in Iowa and 2010 in North Carolina. Among 33,484 men, there were 4,026 applicators who used acetochlor and 3,234 incident cancers, with 304 acetochlor-exposed cases. Increased risk of lung cancer was observed among acetochlor users (RR=1.74; 95% CI: 1.07-2.84) compared to nonusers, and among individuals who reported using acetochlor/atrazine product mixtures (RR=2.33; 95% CI: 1.30-4.17), compared to nonusers of acetochlor. Colorectal cancer risk was significantly elevated among the highest category of acetochlor users (RR=1.75; 95% CI: 1.08-2.83) compared to never users. Additionally, borderline significantly increased risk of melanoma (RR=1.61; 95% CI: 0.98-2.66) and pancreatic cancer (RR=2.36; 95% CI: 0.98-5.65) were observed among acetochlor users. The associations between acetochlor use and lung cancer, colorectal cancer, melanoma and pancreatic cancer are suggestive, however the lack of exposure-response trends, small number of exposed cases and relatively short time between acetochlor use and cancer development prohibit definitive conclusions. What's new? Acetochlor is a commonly used herbicide in the U.S., yet no epidemiologic research has evaluated its carcinogenicity in humans. In this study, the authors examined the relationship between occupational exposure to acetochlor and human cancer risk in a large prospective cohort. Acetochlor use was associated with an increased risk of lung and colorectal cancer, and possibly pancreatic cancer and melanoma. Use of mixtures of acetochlor and atrazine, another widely used herbicide often applied concurrently with acetochlor, was also associated with an increased risk of lung cancer.