Pesticide use and cancer incidence among spouses of pesticide applicators in the Agricultural Health Study

Laura BEANE FREEMAN, National Cancer Institute, United States
BLAIR A. 1 , ZHANG Y. 5 , LERRO C. 1,5 , ALAVANJA M. 1 , FRIESEN M. 1 , ANDREOTTI G. 1 , KOUTROS S. 1 , LUBIN J. 4 , MA X. 5 , HOPPIN J. 2 , SANDLER D. 3

1 Occupational and Environmenntal Epidemiology Branch, National Cancer Intstitute, Rockville, MD, USA
2 Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
3 Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
4 Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA
5 Yale University School of Public Health, New Haven, CT, USA

Objectives: Pesticides have been linked to cancer risk in some epidemiologic studies; however most evaluations have been conducted in predominantly male populations.  We evaluated personal use of specific pesticides, including organophosphate insecticides (OPs) and cancer incidence among female spouses of pesticide applicators in the prospective Agricultural Health Study cohort.
Methods: At enrollment (1993-1997) spouses provided information about ever use of specific pesticides, demographic information, reproductive health history, and other potential confounders. We used Poisson regression to estimate relative risks (RRs) and 95% confidence intervals (95% CIs) for all cancers diagnosed through 2010 for North Carolina and 2011 for Iowa.  
Results: Among 30,003 women, 60% reported personally using any pesticides.  Among the 25.9% who reported OP use, 718 OP were diagnosed with cancer. Any OP use was associated with an elevated risk of breast cancer (RR = 1.20, 95% CI: 1.01, 1.43). Malathion, the most commonly reported OP, was associated with increased risk of thyroid cancer (RR = 2.04, 95% CI: 1.14, 3.63) and decreased risk of non-Hodgkin lymphoma (RR = 0.64, 95% CI: 0.41, 0.99). Diazinon use was associated with ovarian cancer (RR = 1.87, 95% CI: 1.02, 3.43).
Conclusions: This first comprehensive analysis of OP and other pesticide use in relation to cancer risk among women showed increased risks with OP use and several hormonally-related cancers.  Further work evaluating other routes of exposure among farm women is needed for OPs and other chemicals.