Environmental Chemicals Linked to Breast Cancer Risk

Exposure to many chemicals, including gasoline, can heighten the risk of developing breast cancer.

Early life exposure to environmental chemicals may be a significant contributor to developing breast cancer, according to a meta-analysis published by Environmental Research. These results may help guide novel approaches to reduce breast cancer rates.

In a 2007 study, the research team reviewed the relationship between environmental chemicals and breast cancer. The investigators identified 216 chemicals that caused breast cancer in animals, which were then studied in humans.

“That was a real wakeup call,” said researcher Julia Brody, PhD. “Now, 10 years later, we see the evidence is even stronger.”

The authors focused on epidemiology studies conducted between 2006 and 2016 related to the biology of breast cancer, including the role of genes and hormones.

Results from the analysis suggested that exposure to chemicals in the womb, during puberty, and during pregnancy may increase the risk of developing breast cancer.

Specifically, the authors found that exposure to dichlorodiphenyltrichloroethane, dioxins, highly-fluorinated perfluorooctanesulfonamide, and air pollution increased the risk of breast cancer up to 5-fold, according to the study.

Exposure to organic solvents and gasoline was also found to elevate the risk of breast cancer.

“During these so-called windows of susceptibility, the body is changing, breast cells are dividing quickly, and the breast tissue becomes vulnerable to damage from chemicals,” said lead author Kathryn Rodgers, MPH.

However, the investigators reported that genetic variation can affect the body’s response to environmental chemicals.

Results from the Long Island Breast Cancer Study Project indicated that women with certain gene variants who were exposed to polycyclic aromatic hydrocardbonis—commonly found in vehicle exhausts—had a higher risk of breast cancer, according to the authors. It is also known that air pollution is carcinogenic and can cause breast cancer in animals.

There has been a growing concern regarding everyday products that may cause cancer. Product chemicals, including BPA and phthalates, are endocrine disruptors known to interfere with hormones. Animal studies have indicated that endocrine disruptors may cause breast cancer; however, the link in humans is less clear, according to the study.

“Every day, we come into contact with many different chemicals, and new ones are constantly being introduced to the market,” Rodgers said. “Unfortunately, it’s hard to measure exposures to multiple chemicals at multiple times in a person’s life.”

An additional challenge is that it can take many years for breast cancer to develop after exposure to a chemical.

“It’s not practical, nor is it ethical, to wait decades for women to develop breast cancer in order to find out whether a chemical caused their disease,” said Marion Kavanaugh-Lynch, MD, MPH, director of the California Breast Cancer Research Program. “This comprehensive review of the science confirms that we must take a precautionary approach.”

Breast cancer is the most common cancer among women, but only up to 10% of cases are linked to inherited genes, making it preventable, according to the study.

The authors caution that women can reduce chemical exposure by choosing non-toxic products. Policymakers should also implement more stringent protections against chemical exposure to prevent breast cancer, according to the authors. Additionally, chemical safety tests should be strengthened to ensure that products are safe for human use.

“What many don’t realize is that breast cancer is largely a preventable disease,” Dr Brody said. “Traditionally, pharmaceutical hormones, exercise, and other lifestyle factors have topped the list of preventable risk factors. Now, chemical exposures are rising to the top of that list.”