Hazardous Conditions

Can Certain Jobs Cause Breast Cancer? A New Study Suggests Yes

Plastic chemicals at work linked to breast cancer. Florence Williams reports on which industries to watch.

Bill Pugliano / Getty Images

“Women’s work” can be just about anything these days, but research is now showing some jobs can be decidedly bad for their breasts. Women who work closely with plastic chemicals have a higher rate of breast cancer, according to a new Canadian study published this week. The study, published by the journal Environmental Health, found that women working in the automotive and food-canning industries have nearly a fivefold increase in risk for premenopausal breast cancer.

The study authors gave workplace questionnaires to 1,006 women with breast cancer and 1,147 women without the disease in Southern Ontario, a manufacturing region that, among other things, supplies parts to U.S. automakers. Based on answers, researchers then coded the jobs with the highest exposures to carcinogens and hormone-disrupting chemicals. The link to breast cancer was strongest in women who worked for more than 10 years in the highest exposed industries.

Both the automotive and canning industries are known to use chemicals that affect hormone systems in lab animals, such as BPA, phthalates, and flame- retardants. Phthalates, which are used to make plastic malleable for molding car interiors, have been associated with lower sperm counts in men. BPA, used in the lining of food cans, has been banned from some products in Canada.

The effects of these chemicals in humans has been hotly debated because it’s hard to tease out conflicting variables like class, education, smoking, and stress. At the same time, at-risk populations are typically too small to provide statistical power. The chemicals industry argues that current regulations are adequate to protect worker health, but critics say the standards in both Canada and the U.S.—particularly for hormonally active substances—are old and out-dated.

This study is notable for looking at a group that is both relatively large and under-studied—women workers. “It’s helpful to look at highly exposed populations if you want to learn more about the health effects of these chemicals,” said lead author James Brophy, an occupational and environmental health specialist affiliated with the University of Windsor in Canada and the University of Stirling in Scotland. “These could be highly preventable cancers.” The study, however, was not able to link specific chemicals to cancer because the researchers did not test subjects’ blood for the presence of chemicals.

The researchers also found smaller associations between breast cancer and women who work in agriculture and metals manufacturing, and at bars and racetracks, where secondhand smoke exposure is common. Women employed in tooling, foundries, or metal-parts production had a 73 percent increase in breast cancer rates and women who worked in agriculture with possible exposure to pesticides had a 36 percent increased risk. Whether those increases are because of environmental exposures or from other confounding variables is difficult to determine.

Few previous studies have looked at breast cancer in women employed in manufacturing although other studies have found associations between industrial environments and male breast cancer. In 2001, a Scandinavian study found an increase in male breast cancers among workers in the rubber and plastics industries, but the numbers of men with the illness was small.

“The detailed examination of occupations and occupational exposures in this study is pathbreaking,” said Richard W. Clapp, a founder of the Massachusetts Cancer Registry and professor emeritus of epidemiology at Boston University. “This study adds to the growing body of knowledge about occupational risks of breast cancer in women,” he said.

“The U.S. has not conducted this kind of workplace study,” said Jeanne Rizzo, president of the Breast Cancer Fund, a California-based nonprofit. “Federal agencies should immediately look into similar occupations in this country and take this seriously.” Is that likely to happen anytime soon? With a recent federally sponsored report from the Institute of Medicine calling for more study of the environmental causes of breast cancer, it just might. Stay tuned.