Atrazine exposure and breast cancer incidence: An ecologic study of Missouri counties

Numerous studies have implicated the triazine herbicide atrazine (6-chloro-N-ethyl-N 0-(1-methylethyl)-1,3,5-triazine-2,4-diamine) as an endocrine disrupting chemical (EDC). An ecologic study of breast cancer incidence and atrazine exposure in Missouri counties was conducted for the years 1996–2002. The objective of this study was to determine if breast cancer incidence rates were associated with atrazine exposure in Missouri counties. Atrazine detections in public drinking water sources and a surrogate measure of combined acres of corn and sorghum planted were used to determine which of Missouri’s 115 counties could be classified as having high versus low atrazine exposure. Overall, 19 counties were classified as high and 25 as low in exposure to atrazine. Linear regression analyses were conducted using covariates of median income, % black race, and incidence of high parity. Models were generated for all stages of breast cancer (localized and invasive) and for invasive cancer alone. Models refinement was conducted by stepwise elimination of the least significant predictor variables. In the final model, the high-parity predictor was statistically significant in the model for all stages of breast cancer, but not for invasive cancer.The atrazine indicator was not statistically significant in either regression equation.