Abstract Purpose We examined the associations between county-level endocrine-disrupting pesticide usage and breast cancer incidence, overall and by metropolitan status. Methods This ecological study used publicly available data from the United States Geological Survey on county-level agricultural pesticide usage (in kilograms). We focused on 38 pesticides with endocrine-disrupting properties relevant in breast cancer etiology, which were categorized by chemical class as follows: carbamates, neonicotinoids, organochlorines, organophosphates, phosphonates, pyrethroids, triazines, and other miscellaneous compounds. The analysis included 2,457 U.S. counties with data on pesticide usage (2001–2015) and age-adjusted breast cancer incidence rates (2016–2020), accounting for a latency period. Metropolitan status was assessed using the 2013 Rural–Urban Continuum Codes. Gamma regression models with a log-link function were used to estimate rate ratios (RR) and 95% confidence intervals (CI) between pesticides (per interquartile range increase) and age-adjusted breast cancer incidence rates, adjusting for county-level covariates including % smoking, % poverty, % unemployed, % no high school diploma, % uninsured, and residential mobility. Results Total median pesticide use was higher in rural vs. urban counties (17,523 kg vs. 14,743 kg; p < 0.05), with some variation by pesticide class. Pesticide use was associated with slightly higher breast cancer incidence in rural counties (RR = 1.02 (95% CI 1.01, 1.03)), but not in urban counties (RR = 1.00 (95% CI 1.00, 1.00)) ( p int < 0.001). Associations differed by pesticide type. Conclusion Results suggest modest positive associations between county-level endocrine-disrupting pesticide use and breast cancer incidence in rural U.S. counties, with variation by pesticide type. These findings highlight the need for further research to inform targeted prevention efforts.
Neelam et al. (Mon,) studied this question.