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STUDY QUESTIONS LINK OF CHEMICALS, CANCER.

Byline: Marie McCullough Knight-Ridder Tribune News Wire

A new study led by Harvard University researchers offers the strongest evidence yet that the risk of breast cancer does not increase with exposure to the banned chemicals DDT and PCBs.

The study, published in today's New England Journal of Medicine, found that 230 women with breast cancer had lower levels of these toxic chemicals in their blood than a comparable group of women without cancer.

The findings come as worldwide attention is being increasingly focused on the theory that industrial chemicals are triggering higher cancer and infertility rates by disrupting human hormones.

In an editorial accompanying today's study, Stephen H. Safe, a professor of toxicology at Texas A&M University, said the latest research should reassure the public, and discourage ``chemophobia'' - an unreasonable fear of chemicals.

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

Others immediately minimized the significance of the new study.

Fred von Saal, a biologist at the University of Missouri-Columbia, said research should focus on chemical exposures early in life when the body may be more vulnerable, and long before cancer is detected.

Von Saal cited research linking children's mental deficits to fetal exposure to PCBs. These polychlorinated biphenyls were once widely used in industry.

``This,'' he said of the Harvard study, ``is `lamppost science:' You lose your keys and you look under the lamp post because that's where the light is.''

In the body, many chemicals and foods become weak mimics of estrogen, the primary female hormone. Lifetime exposure to estrogen affects breast cancer risk; that's why factors such as early puberty, late menopause and no children increase a woman's risk of developing the disease.

Studies have shown that chemical ``pseudo-estrogens,'' including PCBs and the pesticide DDT, play havoc with the sexual development of laboratory animals and wildlife. For example, DDT caused thinning of eagles' eggs.

But in humans, the effects are unclear. A Tulane University study last year attracted wide attention after it said small amounts of some ordinary, relatively harmless pesticides may cause a devastating rise in estrogen levels when mixed together. The study was withdrawn recently after the results could not be reproduced.

PCBs and DDT, which persist in the environment and in human tissues, have been leading candidates for carcinogens of the breast, but studies are contradictory.

At least three small studies have supported the link. Two previous studies found no link.

The latest investigation, led by Harvard epidemiologist David Hunter, is part of the mammoth, continuing Nurses' Health Study, which has been following 121,700 registered nurses since 1976.

About 33,000 of them submitted blood samples seven years ago. About 230 developed cancer within two years of their submission. Their stored blood samples were then analyzed for PCBs and DDT and compared with stored samples from a matched group of cancer-free nurses.

The outcome ``does not rule out the possibility that other pesticides and environmental contaminants may be associated with breast cancer,'' Hunter wrote. ``But on the basis of our results the use of (DDT and PCBs) does not explain the high and increasing rates of breast cancer.''
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Publication:Daily News (Los Angeles, CA)
Date:Oct 30, 1997
Words:536
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