Breast Cancer Risk and DDT: No Verdict Yet
Fackelmann, Kathy A., Science News
Results of a new study challenge the theory that DDT increases the risk of breast cancer. However, many scientists, including the study's authors, warn that it's premature to discount the link between this pesticide and the malignancy.
In a related report, investigators at the New York State Department of Health discovered an association between industrial pollution and breast cancer.
The DDT-breast cancer hypothesis gained ground last year when Mary S. Wolff of Mount Sinai School of Medicine in New York City published a study showing that women who suffer from the disease tend to exhibit more traces of DDT and its dangerous breakdown product, DDE, in their bloodstream (SN: 4/24/93, p.262). Some researchers believe that DDT and DDE mimic the action of the hormone estrogen and thus fuel the growth of certain breast tumors.
In the new study, epidemiologist Nancy Krieger of the Kaiser Foundation Research Institute in Oakland, Calif., and her colleagues homed in on 300 women who had taken a comprehensive physical examination during the late 1960s, when DDT was commonly used in the United States. The researchers studied 150 women who developed breast cancer an average of 14 years after that examination and 150 women who did not develop cancer and thus served as controls.
Krieger's group analyzed the concentrations of DDE in blood samples that had been obtained at the time of each exam and frozen for later use. In addition, they looked at concentrations of another chemical suspected of playing a rile in breast cancer: polychlorinated biphenyls, or PCBs.
In the April 20 JOURNAL OF THE NATIONAL CANCER INSTITUTE, the researchers describe their surprising results. Unlike the earlier study, this one found no overall association between such pesticide residues and breast cancer.
When the researchers sorted the data by race, however, a more complicated picture emerged. Black women with high concentrations of DDE showed an increased risk of breast cancer, a finding that did not quite reach statistical significance. White women showed a hint of heightened risk at high concentrations of this pesticide. Yet among the Asian women in the study, increased concentrations of DDE actually signaled a decreased risk of breast cancer, a finding that did not reach statistical significance. …