A population based case-control study of farming and breast cancer in North Carolina

We examined the role of farming and pesticide exposure among 862 cases and 790 controls in a population-based, case control study of breast cancer con ducted in North Carolina between 1993 and 1996. We obtained exposure inform ation through personal interview. Increasing duration of farming was invers ely associated with breast cancer risk; odds ratios (95% confidence interva ls) were 1.2 (0.8-1.7), 0.8 (0.5-1.2), 0.7 (0.5-1.1), and 0.6 (0.4-0.9) for 1-10, 11-17, 18-23, and >23 years of farming, respectively, relative to no nfarmers. Inverse associations persisted when farming was restricted to cal endar time periods of 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) u se or to farming at ages 9-16. Among women who farmed, odds ratios (ORs) we re elevated for those who reported being present in fields during or shortl y after pesticide application (OR = 1.8, 95% CI = 1.1-2.8) and for those wh o reported not using protective clothing while applying pesticides (OR = 2. 0; 95% CI = 1.0-4.3), but not among those who reported using protective clo thing (OR = 0.8; 95% CI = 0.4-1.8). We conclude that residence or work on f arms may be associated with a reduced risk of breast cancer. Nevertheless, our results suggest a possible increased risk of breast cancer among a subg roup of farming women who were most likely to be exposed to pesticides.