Noticing pesticide spray drift from agricultural pesticide application areas and breast cancer: a case-control study

Abstract

Objectives: To examine the relationship between self-reported noticing of pesticide spray drift from agricultural areas and breast cancer.

Methods: A case-control study of breast cancer was conducted in Western Australia from 2009 to 2011. Awareness of pesticide spray drift from agricultural areas was assessed by a self-report of whether the participant had noticed spray drift. To evaluate recall bias, we stratified the analysis by participants' belief about whether pesticides increase the risk of breast cancer. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). This analysis included 1,743 controls and 1,169 cases. Sensitivity analysis for potential selection and misclassification bias was also conducted.

Results: Among women who reported 'ever noticed' pesticide spray drift from agricultural areas, an increased risk of breast cancer was also observed (OR=1.43; 95% CI 1.15, 1.78). A dose response relationship between lifetime exposure to noticing pesticide spray drift and risk of breast cancer was observed (p<0.001). An increased risk of breast cancer was observed among women who noticed pesticide spray drift: initially at the age of 20 or younger (OR=1.61; 95% CI 1.19, 2.16); at least 20 years before diagnosis (OR=1.51; 95% CI 1.19, 1.92); and for 10 years or more (OR=1.51; 95% CI 1.18, 1.94).

Conclusion: These findings support the hypothesis that women who ever noticed spray drift or who first noticed spray drift at a younger age had increased risk of breast cancer.