Breast Cancer and the Environment

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Breast cancer is the most common form of cancer among women, and the second most prevalent cause of death among women after heart disease. While cancer deaths have declined in recent years, the incidence of breast cancer has risen one percent a year since 1950. An estimated 43 thousand American women will die from breast cancer this year.

A great deal of research has been reported and more is under way, in the field of environmental influences on breast cancer risk. The goal is to determine their possible relationships to breast cancer. Fewer than 10% of breast cancers develop because of inherited genetic defects, and known risk factors do not explain most sporadic cases. Excepting radiation, most established breast cancer risk factors are linked with total lifetime exposure to estrogen. Experimental work and wildlife studies reveal that environmental chemicals can disrupt hormone production and metabolism, directly or indirectly.

Exposure to Estrogen-like Chemicals. Chemicals with estrogen-like effects -- called xenoestrogens -- that are found in pesticides and other common industrial products have been suspects for the increased risk of breast cancer found in specific regions. Many women who took diethylstilbestrol (DES) to prevent miscarriage produced children with abnormal reproductive systems, and there is some indication that it increased the risk for breast cancer in their offspring.

Radiation and Electromagnetic Fields. Heavy exposure to radiation is a significant risk factor for breast cancer. Women who were treated with high doses of radiation for childhood cancers face a high risk for breast cancer in adulthood.

Reduced Melatonin. Reduced levels of melatonin -- a powerful hormone that affects sleep and other vital functions -- has been associated with breast cancer. This might account for the higher incidence observed in flight attendants.

Although we know some of the risk factors that increase a woman's chance of developing breast cancer, we do not yet know what causes most breast cancers. Research is under way to learn more. Most DNA mutations related to breast cancer, however, occur during a woman's life rather than having been inherited. Acquired mutations of oncogenes and/or tumor suppressor genes may result from radiation or cancer-causing chemicals. Currently there are no proven links between breast cancer, and environmental pollutants.

LINKS AND RESOURCES

The Breast Cancer Fund

Carnegie Mellon University