Organochlorine Compounds and Risk of Breast Cancer
Tongzhang Zheng, M.D., Sc.D.
Yale University, New Haven, CT
Dr. Tongzhang Zheng, of Yale University, New Haven, CT, and colleagues conducted a hospital-based case-control study in Connecticut to investigate risk for breast cancer associated with exposure to organochlorine compounds. Levels of organochlorine compounds are being measured in breast adipose (fatty) tissue and blood serum obtained from women who had surgery or biopsies for breast cancer or benign breast disease.
The organochlorine compounds studied were: hexachlorobenzene (HCB);β-benzene hexachloride (β-BHC); polychlorinated biphenyls (PCBs), a family of chemicals used in coolants and lubricants in transformers, capacitators, and other electrical equipment; and DDT and DDE (a metabolite of DDT), which was once widely used in insect control. Study participants also provided medical and diet histories, and information on alcohol use, cigarette smoking, and other environmental exposures.
The study is considered Long Island Breast Cancer Study Project (LIBCSP)-related because of its potential relevance. As an adjunct to the study, the researchers conducted a pilot case-control study focusing on Tolland County, CT, an area that is included in the Congressional mandate in order to investigate possible environmental causes of breast cancer on Long Island. For this analysis, blood serum and the same types of medical, lifestyle, and risk factor information were collected as for the Connecticut study. The number of women diagnosed with breast cancer was too small to permit valid analysis, however.
The findings from the Connecticut study have been published:
In May 1999, Dr. Zheng and colleagues published separate reports on analyses of two organochlorine compounds. In the first report, which appeared in Cancer Epidemiology, Biomarkers & Prevention, the researchers analyzed risk for breast cancer associated with HCB, and found no increased risk for the cancer associated with the agent. HCB is formed as a by-product in the manufacture of chemicals used as solvents, other chlorine-containing compounds, and pesticides. The study included 304 women who had breast cancer (cases), and 186 women who had benign breast disease (controls) who were treated at Yale-New Haven Hospital between 1994 and 1997 and who were ages 40-79. The researchers did not find a significant difference in HCB levels in the adipose tissue of cases and controls. Further, they did not find significant differences in risk for breast cancer when the data were analyzed according to menopausal status, estrogen or progesterone receptor status, breast cancer histology (cell type), stage of disease at diagnosis, type of benign breast disease, or if the women had breast fed their children.
In the second report, which was published in Cancer, the researchers analyzed the adipose tissue of the same study population for β-BHC, and found no association between risk for the cancer and this chemical compound. They did not find significant differences in levels of β-BHC between cases and controls, nor by menopausal status or, among the breast cancer cases, by estrogen and progesterone receptor status. β-BHC is an isomer (form) of the insecticide benzene hexachloride (BHC), which is also known as hexachlorocyclohexane.
In a third analysis of the same study population, Dr. Zheng and colleagues reported on analysis of the relationship between DDE and DDT exposure and breast cancer risk in the American Journal of Epidemiology. The researchers did not find differences in levels of DDE and DDT in the breast adipose tissue of women who had breast cancer and women who did not have the disease. Thus, these findings do not support an association between adipose levels of DDE and DDT and breast cancer risk.