Adipose organochlorine concentrations and risk of breast cancer among postmenopausal Danish women.

OBJECTIVE: Exposure to environmental organochlorines has been examined as a potential risk factor for human breast cancer with mixed results. Our purpose was to examine associations between organochlorines and the development of breast cancer in a large prospective study using stored adipose tissue. METHODS: We conducted a nested case-control study of 409 postmenopausal women who developed breast cancer and 409 controls selected from the 29,875 women enrolled in the Danish Diet, Cancer, and Health cohort between 1993 and 1997. We measured concentrations of 14 pesticides and 18 polychlorinated biphenyls in adipose tissue, collected upon enrollment, and estimated relative risk (RR) of breast cancer using conditional logistic regression. RESULTS: The results showed no higher risk of breast cancer among women with higher levels of any pesticides or polychlorinated biphenyls; the RR associated with the upper quartile of 1,1-dichloro-2, 2-bis(p-chlorophenyl)ethylene concentration was 0.7 [95% confidence interval (95% CI), 0.5-1.2] contrasting the lower quartile, and for the sum of polychlorinated biphenyls the similar risk was 1.1 (95% CI, 0.7-1.7). We observed a pattern of substantially lower risk of estrogen receptor-negative breast cancer in association with higher levels of most of the pesticides and polychlorinated biphenyls; the RR for the higher quartile of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene was 0.1 (95% CI, 0.0-0.5) and for the sum of polychlorinated biphenyls it was 0.3 (95% CI, 0.1-0.9). CONCLUSION: The results do not support that higher organochlorine body levels increase the risk of breast cancer in postmenopausal women. The interpretation of the inverse association for estrogen receptor-negative breast cancer is currently unclear.

Organochlorines in Danish women: predictors of adipose tissue concentrations.

Organochlorines (OCs) are ubiquitously present in the environment, and food of animal origin is currently reported as the major source of exposure. Carcinogenicity in animals raises concern, and OCs may also be a risk factor for both neurological and immunological effects. Our primary objective was to study predictors of adipose tissue levels of dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs) in Danish women. We showed that adipose tissue concentrations of DDE and PCBs were consistently positively associated with age and the consumption of fish with a high fat content, while total lifetime duration of lactation had an inverse relationship. The direction of the association with body mass index (BMI) depended on the OC studied. The consumption of meat, fruit, lean fish, medium-fat-content fish, poultry, and eggs was not associated with OC concentrations in our study. We classified fish according to fat percentage, which seems more relevant than considering only total fish consumption. When PCBs were subdivided according to their chemical structure, similar results were obtained for the mono-, di-, and tri-ortho PCBs, indicating that PCBs can be treated as a homogenous group when studying predictors of concentrations in humans. In conclusion, the present study shows that age, lactation, and BMI are consistent predictors of human adipose tissue concentrations of DDE and PCBs and that dietary factors other than fish with a high fat content are not important predictors of these concentrations.