Malignant Mimicry; September 1993; Scientific American Magazine; by John Rennie; 2 Page(s)

Pollutants resembling crucial human hormones may be short-circuiting some of the body's most important control mechanisms. The substances that worry researchers most are the usual suspects fingered in pollution reports: polychlorinated biphenyls (PCBs), dioxins, DDT and some petroleum by-products, among others. To varying degrees, all these chemicals can mimic the effects of estrogens on cells. Some recent work has turned up hints that a lifetime's subtle overexposure to such potent physiological signals could be responsible for cancers, birth defects and reproductive problems.

In a report scheduled to appear in Environmental Health Perspectives, for example, Devra Lee Davis of the Department of Health and Human Services and her colleagues conjecture that PCBs and similar compounds might be causing many cases of breast cancer. Davis, who has previously made controversial assertions about rising cancer rates, notes that most of the known genetic risk factors for breast cancer influence the body's estrogen metabolism. Many of the suspect compounds have that same effect or have an affnity for the receptors on cells that normally bind to estrogens. The chemicals might therefore increase a woman's lifetime exposure to estrogens. Because some cells in the breast respond to estrogens by multiplying, the chemicals could trigger rapid, inappropriate cell divisions like those in tumors.