Regulations to protect workers from on-the-job hazards—and to compensate them for occupational harms—have a strong and storied history in the United States and Canada. But those protections are lacking for women who are at increased risk of breast cancer due to their occupation, says the author of a new study on breast cancer risk.
Previous research has hinted that some types of occupational exposures can raise the risk of breast cancer. Chemicals used in plastics manufacturing jobs, like polybrominated diphenyl esters—or PBDEs—are known carcinogens, as is secondhand tobacco smoke. Yet too little attention has been paid to women's exposures to these chemicals and cancer risk, says Dr. James Brophy, adjunct faculty at the University of Windsor in Ontario, and a co-author of the new research.
The study, published in the journal Environmental Health, looked at women who were diagnosed with breast cancer in Essex or Kent Counties in Southern Ontario. Researchers surveyed 1,006 women with breast cancer and a control group of 1,147 women without the disease regarding factors known to influence breast cancer risk—such as family history, use of hormone therapy, smoking, number of children and other factors. The women also described where they worked and their job activities.
The study showed that women who worked for 10 years in jobs that involved exposure to chemicals had a 42 percent increased risk of breast cancer compared to women who worked in occupations without chemical exposures.
The findings should help shine a light on the link between breast cancer and occupational exposures, Brophy told TakePart.
"In cancer causality, there has been a real turning away from involuntary exposures since the late 1970s," he says. "Cancer causality has been considered lifestyle choices, such as smoking, drinking, diet. Attention to other causes of cancer has been considered marginal. But the majority of women who get the disease don't have the known or suspected risk factors. The disease is occurring among many healthy women. That's opening up a major public health question about why. "
Breast cancer likely arises due to a combination of factors, such as genetics and outside influences, like chemical exposures or diet. But in the study, researchers found a clear link to some occupations even when controlling for many of the other risk factors for the disease.
Women who work in farming had a 36 percent increased risk of breast cancer, Brophy says. In Canada, he notes, employment in farming often begins early in a woman's life. Early exposure to pesticides may account for the excessive risk.
The study also showed that the breast cancer type was linked to some occupations. For example, women in agricultural occupations with breast cancer were more likely to have a type known as estrogen receptor negative.
"That is the most difficult breast cancer to treat," Brophy notes. "What we showed was these different occupational exposures were influencing the predominant type of tumor status in these women. That is a significant thing. It added weight that occupation was influencing the disease and the development of the disease."
Breast cancer risk was almost double for women working in the Canadian car industry's plastics manufacturing sector. The study showed that breast cancer risk was nearly five times higher in premenopausal women working in plastics and food canning. Breast cancer typically occurs after menopause.
"The elevated risk for premenopausal women in auto plastics and canning was really very shocking," he says. "These diseases are occurring among young women, which is normally a low-risk group."
Overall, breast cancer risk was doubled for women working in food canning or tinning. Women in metalworking had a 73 percent increased risk of breast cancer.
Perhaps not as surprising, women employed in bars, casinos and at race tracks had double the risk of developing breast cancer, most likely due to secondhand tobacco smoke exposure.
More attention has been paid to the health effects of chemical exposures to males in particular industries, Brophy notes, such as the risk of lung cancer linked to mining. However, the theory that certain chemicals, called endocrine disruptors, can cause cellular changes during critical periods of breast development is well known in the medical world.
"In occupational health, in general, there has been an ongoing tension about the lack of focus and concern about issues for women," he says. There is a lack of attention to blue-collar occupations, but even less attention paid to the working conditions of women."
Even in occupations where men and women hold the same position, women are affected differently and may require a different set of workplace protections, he says.
"A woman janitor in a hospital is assumed to have the same exposure as a male janitor in a hospital ," he says. "The accepted idea is that their exposures are the same as men. But what we discovered in our study is often in these workplaces there is a division of labor in which men have certain tasks and women certain tasks and their exposures can be entirely different...Women have a different vulnerability. On the whole issue of hormonal disruption, what that means for a woman would differ than for a man."
The concept that workers should be protected from occupational harm has been expanding in recent years in some areas. For example, some countries now recognize that working irregular shifts or night shifts can increase the risk of obesity and obesity-related diseases, like diabetes.
But there is still no workplace standard that accounts for exposure to chemicals that are known endocrine disruptors, Brophy says.
"There is very little being done to protect women from these exposures," he says. "I think there is an awareness among workers. The problem has been what you can do about it."
Emerging scientific evidence may give workers an avenue to seek compensation for harms through the courts, Brophy adds.
"It's only after you establish compensation that there is a real incentive for employers to do something about it," he says.
Question: Should employers act now to protect female workers from an increased risk of breast cancer linked to particular occupations? Tell us what you think in the comments.
Shari Roan is an award-winning health writer based in Southern California. She is the author of three books on health and science subjects.