Female Breast Cancer and the Environment

Breast cancer is the most commonly diagnosed cancer in women in the United States. Breast cancer will develop in approximately one in eight women during their lifetime. The incidence of this disease is decreasing, primarily among women older than 50 years. The disease usually occurs in women but men can have breast cancer too.

Only about 47% of breast cancers that occur in the United States can be attributed to established risk factors. While animal studies indicate that environmental contaminants can cause breast tumors, clear links between environmental exposures (other than ionizing radiation) and human breast cancer have not been established.

Exposure to chemicals such as poly aromatic hydrocarbons (PAH), benzene, and organic solvents and passive smoking have been suspect in causing breast cancer, but the evidence is weak and more research is needed.

Pesticides and industrial products concern researchers because of their presence in the environment, their ability to be absorbed by fat, and their potential to act as endocrine disruptors. An endocrine disruptor is a synthetic chemical that, when absorbed into the body, either mimics or blocks hormones and disrupts the body's normal functions. Overall, previous studies do not support an association between these chemicals and breast cancer.

Exposure and Risk

The exact causes of breast cancer are unknown; however, women that are in certain categories are at increased risk for breast cancer. Known risk factors include:

• Older age
• White ethnicity
• Obesity (after menopause)
• Dense breast tissue (after menopause)
• High estrogen levels
• Unusually tall
• Early onset of menstruation
• Later age pregnancy
• Having no or few children
• Late onset of menopause
• Family history of breast cancer
• Certain genetic mutations
• Certain types of benign breast disease
• History of breast cancer
• Post-menopausal hormone use
• Heavy alcohol consumption
• Cigarette smoking
• Exposure to secondhand cigarette smoke
• Current or recent use of birth control pills
• Low levels of physical activity
• Never breast feeding or short duration of breast feeding

Prevention

Most women in whom breast cancer develops have no risk factors. Breast self-examinations and breast examinations and mammograms conducted by healthcare professionals increase the chances that breast cancer will be diagnosed early. Among women who have higher than average risk, certain drugs may help prevent breast cancer. All women should discuss their risk and screening or prevention options with their healthcare provider.