While this may lower a woman’s risk for breast cancer, the long-term consequences for children exposed to higher levels of such contaminants in breast milk is of concern (20).

How might harmful xenoestrogens get into the body to act on breast cells or the developing brain? One highly likely route is through animal fat in the diet. Harmful synthetic xenoestrogens tend to accumulate in fatty tissue and move up the food chain. Some synthetic xenoestrogens wind up in food because once they enter the environment, they can persist and accumulate for more than 50 years. People who live in polluted areas might be directly exposed to harmful xenoestrogens simply by breathing the air or drinking contaminated water. Occupational exposures to xenoestrogens can also occur, such as in chemical laboratories and industrial plant.

Some investigators, such as Stephen Safe of Texas A&M University, question whether synthetic xenoestrogens can play any role in breast cancer. They point out that people are exposed to minute quantities of individual chemicals in the environment that are far less potent than natural estrogen, such as those produced in the body itself or derived from plant products. In addition, dietary plant estrogens like soy appear to diminish harmful estrogenic effects, canceling out the influences of the bad estrogens. These observations are correct, but incomplete. It is true that any given synthetic xenoestrogen may enter the body in very small amounts, compared with the body’s own natural hormones. However, once in the body, many fat-seeking synthetic xenoestrogens tend to persist for decades in tissues and are not readily excreted. In contrast, plant estrogens are usually degraded rapidly in the body. Thus, it is unlikely that natural estrogens consumed in most people’s diets can completely negate the activity of persistent, cumulative synthetic compounds.

We realize that xenoestrogens cannot account for all breast cancer cases that occur. Recent findings of low levels of some organochlorines in blood and fat are welcome indications of the success of past environmental control efforts to reduce or ban the use of many such compounds. But the variety of materials that can alter hormone metabolism appears extensive and not well characterized at this time. The combined effect on human and ecological health remains a matter of serious concern. In contrast to many established risk factors for breast cancer, such as early onset of menstruation and late menopause, exposure to synthetic xenoestrogens can be reduced or controlled through public policies. In addition, beneficial xenoestrogens, such as those in broccoli, soy, and fish, may prove useful in preventing the disease from occurring or recurring.. If reducing avoidable exposures to harmful xenoestrogens and encouraging the use of beneficial materials made it possible to avert only one fifth of breast cancers every year, millions of women—and those who care about them—would be spared the burden of this difficult disease, and the public would be spared the burgeoning costs of treatment and care. Such prospects are too tantalizing to ignore.

References and notes

20. Joseph L. Jacobson and Sandra W. Jacobson, "Intellectual Impairment in Children Exposed to Polychlorinated Biphenyls in Utero," New England Journal of Medicine, Vol. 335, No. 11 (1996), pp. 783-789.