A remarkable new report from the Institute of Medicine(IOM) identifies steps women can take to reduce the risk of breast cancer associated with the environment. And it’s not just avoiding toxic chemicals. In fact the report recommends avoiding unnecessary medical radiation, forgoing use of combination estrogen-progestin menopausal hormone therapy if possible, limiting alcohol consumption, maintaining a healthy weight, exercising regularly, and avoiding tobacco use, calling those environmental risk factors for which there is consistent scientific evidence of an association with breast cancer. The report says the evidence indicates a possible, though currently less clear, link to increased risk for breast cancer from exposure to certain chemicals, including benzene, 1,3-butadiene, and ethylene oxide, which are chemicals found in some workplace settings and in gasoline fumes, vehicle exhaust, and tobacco smoke. Further it says avoiding personal use of hair dyes and non-ionizing radiation emitted by mobile devices and other technologies likely will not impact a woman’s risk for breast cancer, and that because of insufficient or contradictory evidence, the scientific jury is still out on whether many chemicals of concern, including bisphenol A (BPA), pesticides, ingredients in cosmetics and dietary supplements, and other substances alter the risk for breast cancer.
We asked Michael J. Thun, M.D., vice president emeritus of Epidemiology and Surveillance Research what he thought of the report.
“This is an important report that carefully reviews the evidence of how women can reduce their risk of breast cancer. The ‘environmental’ causes of breast cancer are defined broadly to include all factors not directly inherited on DNA. Some of the well established environmental risk factors are modifiable (for example excessive weight gain, physical inactivity, and use of menopausal hormone therapy). Others cannot practically be modified (for example reproductive factors such as age at menarche and age at first birth). The established modifiable risk factors identified in this report are consistent with those identified in Cancer Facts and Figures 2011. They include excessive adult weight gain, (for post-menopausal breast cancer), use of combined estrogen and progestin hormone therapy, physical inactivity, consumption of one or more alcoholic beverages per day and high doses of ionizing radiation (typically for cancer treatment) to the chest. There is accumulating evidence that active smoking in childhood and adolescence also increases breast cancer risk.
“The report also considers other exposures that are very much in the minds of the general public, but for which the evidence is more limited, contradictory or absent. These include exposures to chemicals such as benzene, ethylene oxide, 1,3- butadiene, and bisphenol A in industrial settings and consumer products, and to other factors such as shiftwork, active smoking and secondhand smoke. The report proposes research and chemical testing approaches to evaluate the potential risk from these exposures more effectively.
“The main contribution of the report is to characterize the strength of the scientific evidence regarding various proposed risk factors for breast cancer and to identify areas of uncertainty in which further research is needed.”