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DDT may foster breast cancer, study finds.

A new study finds that women who develop breast cancer tend to carry higher residues of DDT in their blood than do women free of the disease. Like certain other chlorinated organic chemicals, DDT - and its persistent breakdown product, DDE - can mimic the effects of estrogen, a hormone that many breast cancers need for growth. Exposure to low levels of DDE and other widespread organochlorines may help explain the rising breast cancer rates in recent decades (SN: 4/21/90, p.245), conclude the study's authors.

Once stored in body fat, DDE tends to remain there for years, in some cases a lifetime. The United States banned DDT in 1972, but trace levels of the pesticide persist in food to this day. U.S. adults with DDT in their tissues and blood probably were exposed to the pesticide in its heyday, says epidemiologist Walter J. Rogan of the National Institute of Environmental Health Sciences in Research Triangle Park, N.C. DDT was "ubiquitous in the 60's," he recalls. Some kids "were dusted with it."

The women were part of the New York University Women's Health Study, which enrolled 14,290 area women between 1985 and 1991 in a prospective investigation of breast cancer's possible link to hormones, diet, and the environment. Fifty-eight women were diagnosed with breast cancer within six months of entering the study, They were matched with 171 cancer-free participants on the basis of such factors as menopausal status, age, and education.

Researchers found that DDE concentrations were approximately 35 percent higher in women with cancer than in those without. Indeed, report Mary S. Wolff of Mount Sinai School of Medicine in New York City and her co-workers in the April 21 JOURNAL OF THE NATIONAL CANCER INSTITUTE, women with just 19 parts per billion (ppb) of DDE faced four times the cancer risk as women with 2 ppb.

Though cancer patients also tended to have higher concentrations of polychlorinated biphenyls (PCBs), a trace contaminant in some foods, the increase proved statistically insignificant. PCBs' possible link to cancer weakened even further when the researchers accounted for a woman's DDE levels.

These preliminary data "should serve as a wake-up call for further research," according to David J. Hunter and Karl T. Kelsey of Harvard School of Public Health in Boston. In an accompanying editorial, they say that although the study looked at a relatively small number of women, it "is important because it included adjustment for known risk factors and mutual adjustment for DDE and PCB levels."

The new findings are plausible scientifically, Hunter and Kelsey say, Another chlorinated compound, dioxin, exhibits hormone-like effects in animals by binding to the Ah receptor in cells (SN: 1/11/92, p.26) and triggering everything from immune suppression and tumors to cleft palates. DDT and PCBs can activate enzyme production in people through a mechanism "similar to that of dioxins [by binding] to an Ah-like receptor," the Harvard team notes.

In humans, DDE and certain other chlorinated organics may act as surrogates for steroid hormones. "We have some evidence that at the levels found in the body, [DDE and PCBs] might be acting as estrogens," says Rogan. A 1987 study by his group showed that residues of these compounds apparently decrease a woman's ability to produce milk, much as estrogen does. Moreover, he notes, if organochlorine-fostered cancers "were an estrogen-mediated effect, I would expect PCBs to be less effective [than DDE]," as they were in the new study

However, he cautions, because so little is known about human effects of DDE and PCBs, such compounds might just as easily trigger tumors by nonestrogenic means.
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Title Annotation:insecticide
Author:Raloff, Janet
Publication:Science News
Date:Apr 24, 1993
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