Dichlorodiphenyldichloroethene, polychlorinated biphenyls, and breast cancer among African-American and white women in North Carolina

We examined plasma dichlorodiphenyldichloroethene (DDE) and total polychlor inated biphenyl (PCB) levels in relation to breast cancer in a population-b ased, case-control study of African-American women (292 cases and 270 contr ols) and white women (456 cases and 389 controls) in North Carolina. Adjust ed odds ratios (ORs) for breast cancer comparing the highest to lowest thir d of DDE were 1.41 [95% confidence interval (CI), 0.87-2.29] in African-Ame rican women and 0.98 (95% CI, 0.67-1.43) in white women, ORs comparing the highest to lowest third of total PCBs were 1.74 (95% CI, 1.00-3.01) in Afri can-American women and 1.03 (95% CI, 0.68-1.56) in white women. Among Afric an-Americans, the OR for total PCBs was highest for obese women (body mass index greater than or equal to 34.2; OR, 4.92; 95% CI, 1.63-14.83). In cont rast, the OR for DDE was highest for the leanest African-American women (bo dy mass index, <25; OR, 3.84; 95% CI, 0.98-15.08), ORs for DDE were not ele vated among women who lived or worked on farms or elevated among farming wo men who reported exposure to pesticides. Our results suggest absence of a s trong effect for DDE or total PCBs in breast cancer but lend support for as sociations among subgroups of women. In our study, factors such as income, parity, breastfeeding, race/ethnicity, and body mass index influenced the r elationship of organochlorines and breast cancer, Differing distributions o f such factors may explain some of the inconsistencies across previous stud ies.