Women who work in certain manufacturing environments face an increased risk of breast cancer of nearly 50 per cent due to years of exposure to carcinogens and hormone-disrupting chemicals, a new landmark Canadian study shows.

Research released Monday focused on “work-related breast cancer” and looked at women who worked in plastic manufacturing, canning, farming and metalworking, as well as those who worked in a bar/casino setting. The study showed an average 42-per-cent increase in breast cancer risk for these women after 10 years of working in certain environments.

“What it showed was that (breast cancer) wasn’t random,” lead study author Dr. James Brophy told CTV News. “This is one of the key issues at the heart of this study. These exposures at certain moments of a woman’s life can have a profound effect on her breast cancer risk later in life.”

Brophy said while breast cancer is the most prevalent cancer among Canadian women -- with one in nine women developing the disease in their lifetime -- less than half the cases can be explained by known cancer risk factors.

The multi-year project looked at 2,000 women in Essex and Kent counties in southern Ontario, where there are extensive manufacturing and agriculture industries. The research showed that women who worked in farming face a 36-per-cent increase in breast cancer risk, which is linked to a high rate of pesticides exposure, often at an early age.

Women who work in the automotive plastics and food-canning sectors saw their rate of breast cancer risk double, while those who were pre-menopausal and worked in those industries saw an almost five-fold increase in risk.

Researchers say ongoing exposure to plastics that have been found to release estrogenic and carcinogenic chemicals are a significant concern.

Exposures to chemicals in the food-canning industry may include pesticide residues and emissions from the polymer linings of cans, according to the report.

In the metalworking industry, researchers found a 73-per-cent increase in breast cancer risk following long-term exposure to potentially hazardous metals and chemicals, while higher exposure to second-hand smoke in bars and casinos is linked a two-fold increase in risk.

Brophy said what links many of these diverse industries is the use of chemicals that have been shown to cause breast cancer in animal studies.


The University of Windsor professor added that many of the chemicals that can disrupt a woman’s hormone system can do so at levels that are well below legal limits in Canada.

Breast cancer survivor Sandy Knight said when she was diagnosed with the breast cancer she attributed it to stress, drinking and smoking.

“It was a guilty thought, not what could have caused this, I just put it on myself,” she said.

It wasn’t until Knight was given a questionnaire from Dr. Brophy’s research team while in hospital did she link her disease to years of work at a Windsor, Ont.-area plastic factory.

“When I first started working with plastics there wasn’t really concerns because we didn’t know anything about the plastics,” said Knight. “So you just went to work and you did your job. Unless something happened, unless you were exposed to something or felt something, there were no concerns of working in that industry because back then it was a good-paying job.”

While she’ll never be 100 per cent sure of the exact cause of her cancer, she believes her extensive exposure to plastics played a role.

“This has to be really looked at and it has to be done today,” she said. “There’s no reason these workers should be exposed to these kinds of chemicals any longer.”

Brophy added that the time for researching possible cancer-causing chemicals has passed.

“I think that there are literally hundreds of studies on chemicals associated with elevated breast cancer risk,” he said. “We need to take action on these substances.”

The study was funded by the Canadian Breast Cancer Foundation, the Breast Cancer Society of Canada, the Windsor-Essex County Cancer Centre Foundation and the Green Shield Foundation

With a report from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip