What Are the Risk Factors for Breast Cancer (VI)?

Antiperspirants: Internet e-mail rumors have suggested that chemicals in underarm antiperspirants are absorbed through the skin, interfere with lymph circulation and cause toxins to build up in the breast, and eventually lead to breast cancer. There is very little experimental or epidemiological evidence to support this rumor. Chemicals in products such as antiperspirants are tested thoroughly to ensure their safety. One small study recently found trace levels of parabens (used as preservatives in antiperspirants), which have weak estrogen-like properties, in a small sample of breast cancer tumors. However, the study did not look at whether parabens caused the tumors. This was a preliminary finding, and more research is needed to determine what effect, if any, parabens may have on breast cancer risk. On the other hand, a recent large epidemiological study found no increase in breast cancer in women who used underarm antiperspirants or shaved their underarms.

Underwire bras: Internet e-mail rumors and at least one book have suggested that bras cause breast cancer by obstructing lymph flow. There is no scientific or clinical basis for that claim.

Environmental pollution: A great deal of research has been reported and more is being done to understand environmental influences on breast cancer risk. The goal is to determine their possible relationships to breast cancer.
Currently, research does not show a clear link between breast cancer risk and exposure to environmental pollutants, such as the pesticide DDE (chemically related to DDT), and PCBs (polychlorinated biphenyls).

Smoking: Most studies have found no link between active cigarette smoking and breast cancer. Though both active smoking and secondhand smoke have been suggested to increase the risk of breast cancer in some studies, the issue remains controversial. The California Environmental Protection Agency recently concluded that secondhand smoke causes breast cancer in younger, mainly premenopausal women. The US Surgeon General is currently reviewing the evidence on this link, and a report is expected in late 2006. Regardless of the possible link between tobacco and breast cancer, not smoking cigarettes and limiting exposure to secondhand smoke is beneficial for a number of health reasons, including a reduced risk of other cancers and heart disease.

Night work: A few recent studies have suggested that women who work at night, for example, nurses on a night shift, have an increased risk of developing breast cancer. However, this increased risk has not yet been proven, and when further studies are conducted, this factor may be found to be unimportant.