There is increasing interest in the question of whether chemicals and carcinogens in our environment may be one cause of breast cancer. To date, most of the research has focused on animal models and cell lines. There has been some intriguing data, particularly regarding exposures to low doses of potential carcinogens and/or exposures in prenatal or early life. But it is difficult to say whether these findings hold true for real life exposures. The studies that have been done in women are few and far between, and most have not been able to account for the chemical exposures women may have had, at certain points in their lives.
That is why the article published by a Canadian research group on November 19 in Environmental Health attracted so much attention. The research was conducted in two counties in Southern Ontario, where there is extensive manufacturing and agriculture, and involved 1006 women with breast cancer and 1146 without the disease. (This is called a case-control study.) All of the participants provided detailed occupational histories so that the researchers could assess their potential exposure to carcinogens and endocrine disruptors (synthetic chemicals that either mimic or block hormones and disrupt the body’s normal functions). The participants also provided information about their reproductive risk factors (like age at first pregnancy), physical activity, smoking, and alcohol use.
The study showed that women who had worked at a job with potentially high exposures to chemicals and endocrine disruptors for 10 years had a breast cancer risk that was 42 percent higher than women who had a different type of job. More specifically, women working in farming were found to have a 36 percent higher risk while metal workers had a 73 percent higher risk. Women working in plastics, food canning, bars, casinos, or racetracks had a two-fold increase in risk.
It is important to note that the researchers could only identify the women who had the potential to be exposed to carcinogens, since they had no way of documenting if they were exposed or what they were exposed to. This means that the risk may well be higher or lower than predicted. Also, the actual number of women in some of these specific jobs was small.
Even so, this study highlights how important it is to look at occupational exposures that may increase breast cancer risk. This study gives us a good place to start. The next steps should include documenting actual exposures to occupational carcinogens in women and their incidence of breast cancer. And, of course, non-occupational exposures to carcinogens will also need to be studied. In fact, European researchers are launching a study that will use smartphones to monitor volunteers and record the chemicals they are exposed to throughout their day. By studying what they call the “exposome”— the effect of environmental exposures on health—these scientists hope to add to what has been learned from genome studies to make connections between genes and the environment and cancer risk.
If Europe can do it, we can do it too! And our Health of Women Study offers researchers the perfect place to ask questions about chemical exposures. Sign up now and help us learn what causes breast cancer.