TPS 633: Health effects of pesticides, Johan Friso Foyer, Floor 1, August 27, 2019, 3:00 PM - 4:30 PM
Background: Some epidemiologic and laboratory studies suggest that pesticides are related to increased breast cancer risk, but evidence is inconsistent. Women engaged in agricultural work or residing in agricultural areas may experience appreciable exposures to a wide range of pesticides, including herbicides, fungicides, and fumigants.
Methods: We examined associations of herbicide, fungicide, and fumigant use with breast cancer incidence among wives of farmers in the prospective Agricultural Health Study. Farmers and their wives provided information on pesticide use, demographics, and reproductive history at enrollment in 1993-1997 and in 5-year follow-up interviews. Cancer incidence was determined via cancer registries. Among 30,594 wives with no history of breast cancer before enrollment, we examined breast cancer risk in relation to the women’s and their husband’s pesticide use, using Cox proportional hazards regression to estimate adjusted hazard ratios (HR) and 95% confidence intervals (CI).
Results: 56% of the women reported ever using pesticides and 1,081 were diagnosed with breast cancer during an average 14.7 years follow-up. We found evidence of elevated risk in relation to ever use of the fungicide benomyl by the women (HR=1.6; 95% CI: 0.9, 2.7) and by their husbands (HR=1.5; 95% CI: 0.9,2.5). There were also suggestive increases in risk in relation to ever use of the herbicide 2,4,5-T by the women (HR=1.6; 95% CI: 0.8,3.1) and of the structurally similar herbicide 2,4,5-TP by their husbands (HR=1.5; 95% CI: 0.9,2.7). We observed little evidence of differential risk by tumor estrogen receptor status.
Conclusions: Increased breast cancer risk was associated with use by both the women and their husbands of the fungicide benomyl and the related herbicides 2,4,5-T and 2,4,5-TP. Ongoing cohort follow-up may help clarify the relationship, if any, between individual pesticide exposures and breast cancer risk.