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Study: No link between breast cancer, banned chemicals

Breast cancer graphic October 29, 1997
Web posted at: 9:34 p.m. EST (0234 GMT)

BOSTON (CNN) -- Two banned chemical compounds suspected of increasing a woman's risk of developing breast cancer do not appear to have any direct correlation to the disease, according to the results of a new study.

In the study, published in Thursday's edition of the New England Journal of Medicine, researchers from the Harvard School of Medicine and Brigham and Women's Hospital tested the blood of two groups of women, looking for evidence of exposure to the pesticide DDT and PCBs, a class of industrial chemicals.

Both substances were banned two decades ago but were so widely used that traces remain in the environment.

One group of 240 women had developed breast cancer; a second control group of 236 had not.

"We did not find that these chemicals were associated with increased risk of breast cancer," said Dr. David Hunter, who led the study. "We found that the levels of these chemicals were actually somewhat lower in the women who went on to get breast cancer versus the women who did not."

Several previous studies had indicated that there might be a link between these two compounds and breast cancer because the chemicals mimic the female hormone estrogen, which has been linked to the disease.


However, Barbara Brenner, a breast cancer survivor and advocate for increased awareness and research, says this study does not let the environment off the hook.

"I have no doubt that there are things in the environment to blame," Brenner said. "I don't know what they are, and nobody else does either."

Breast cancer affects more women than any other type of cancer, and the rate of occurrence has increased by an average of 1 percent a year over the past 57 years. Yet no one knows for sure what causes it or why it seems to be increasing.

In an editorial accompanying the study, Dr. Stephen H. Safe of Texas A&M University said the results should reassure the public that these chemicals don't cause breast cancer. He noted that the disease has increased over the past 20 years, at the same time that the chemicals have been banned.

"It is incumbent on scientists, the media, legislators and regulators to distinguish between scientific evidence and hypotheses and not to allow a 'paparazzi science' approach to these problems," Safe said.

Medical Correspondent Al Hinman and Reuters contributed to this report.

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