EarthTalk: What's the Connection Between Breast Cancer and Chemicals in the Environment?

Dear EarthTalk: Is there any proof linking human breast cancer to exposure to chemicals in the environment? Or do researchers think most cases of breast cancers are genetically inherited? -- Bettine Carroll, New York, NY

A groundbreaking research study coordinated by the non-profit Silent Spring Institute and recently published by the American Cancer Society found that synthetic chemicals have likely played a large role in the rising incidence of breast cancer throughout the world over the last half-century. The study identified 216 man-made chemicals-including those found in everyday products like pesticides, cosmetics, dyes, drugs and gasoline (and diesel exhaust)-that have been shown to cause breast cancer in animals. Researchers believe these substances, many of which "mimic" naturally occurring hormones once inside the body, are also to blame for the increasing prevalence of human breast cancer.

According to epidemiologist Devra Lee Davis of the University of Pittsburgh's Graduate School of Public Health and one of the lead researchers on the new study, the more hormones cycling through a woman's body during her lifetime, the more likely she is to develop breast cancer. Synthetic chemicals that mimic hormones magnify the risk, as the body doesn't know the difference between its own real hormones and other introduced chemicals. Only one in 10 women who develop breast cancer inherits a defective gene from their parents, Davis adds, meaning that in 90 percent of breast cancer cases studied, external non-genetic agents (e.g. synthetic chemicals) contributed to the development of the cancer.

Another telling clue is the fact that the breast cancer risk of adopted children parallels the risk of the family they grew up in, not that of their biological family, as proven by analyzing medical records from Scandinavian countries that keep detailed registries following people from birth to death. "What we understand is that if cancer runs in your family it could be because your family had similar eating patterns, similar lifestyle patterns as well as lived in the same area," says Davis. "It's really important that we take another look at...the kinds of chemicals that we are using everyday," she adds. "We think that there are alternatives that can be used."

The U.S. government has been reluctant to institute new restrictions on the production of highly profitable synthetic chemicals, but European regulators are taking the issue very seriously. The European Commission's new Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Program calls on chemical manufacturers selling anywhere in Europe to re-register and re-evaluate the potential health hazards-including cancer risks-of their products. Environmental and public health advocates hope that American chemical companies will follow that lead with chemicals sold here.

In the meantime, consumers can help prevent cancer by buying and eating organic foods, avoiding pesticides and other synthetic chemicals whenever possible, using non-plastic containers to reheat and store foods (some plastics are thoughts to leach cancer-causing chemicals into food when heated), and supporting government regulation and more research on synthetic chemicals and their effects.

CONTACTS: Silent Spring Institute, www.silentspring.org; European Commission's REACH Program, ec.europa.eu/environment/chemicals/reach/reach_intro.htm.

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