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NEWS | December 8, 2011

Environmental risks for breast cancer report released

UC Davis professor chaired the Institute of Medicine committee that examined the evidence

(SACRAMENTO, Calif.)

A national panel chaired by Irva Hertz-Picciotto of UC Davis has determined that there is consistent scientific evidence that breast cancer risk can be reduced if women avoid unnecessary medical radiation and use of hormone therapy and if they maintain healthy lifestyles.

The findings were delivered in a report Wednesday by the Institute of Medicine (IOM) at the 2011 San Antonio Breast Cancer Symposium. The research, begun in May 2010, was conducted with a grant from Susan G. Komen for the Cure. The independent committee of experts was charged with assessing what is known, as well as what is not conclusive, about environmental risk factors for breast cancer.

Irva Hertz-Picciotto © UC Regents
Irva Hertz-Picciotto

The evidence also indicates a possible, though currently less clear, link to increased risk for breast cancer from exposure to benzene, 1,3-butadiene and ethylene oxide, which are chemicals found in some workplace settings and in gasoline fumes, vehicle exhaust and tobacco smoke.

The committee found that 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, as multiple studies have found no connection between these factors and the disease.

Because of insufficient or contradictory evidence, the committee determined that 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. Women may choose to minimize their exposure to some chemicals, but the committee found the research inadequate to draw conclusions about the potential benefit of such actions. Chemical ingredients in cosmetics, dietary supplements and other products undergo only very limited testing before they are put on the market, and the committee noted the value of efforts to help consumers become more aware of this issue.

According to the IOM, the steps identified in the report have the potential to reduce the risk for breast cancer among women in general, but the committee cautioned that the evidence on how much risk reduction any of these steps offers is inconclusive. Whether it is small or significant, the impact on individuals will vary considerably because women are exposed to a range of substances throughout their lives; in addition, biological, physical and genetic factors influence their individual chances for developing the disease.

"Breast cancer develops over many years, so we need better ways to study exposures throughout women's lives, including when they are very young," said Hertz-Picciotto, professor and chief of the Division of Environmental and Occupational Health with the UC Davis Department of Public Health Sciences. "We also need improved methods to test for agents that may be contributing to breast cancer risk and to explore the effects of combined exposures."

She said, for example, that research is needed on the effects of exposures at specific stages of breast development, and on the cumulative effects of exposures at different life stages or multiple exposures.

An arm of the National Academies of Science, the IOM is an independent, nonprofit organization that works outside government to address pressing questions about health and health care and provide unbiased and authoritative advice to decision makers.

More information on the study is available at http://www.iom.edu/BreastCancerEnvironment.