Breast cancer is a malignant tumor that starts from cells of the breast. A malignant tumor is a group of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of the body. Breast cancer occurs almost entirely in women, but can occur rarely in men. Breast cancer is the most commonly diagnosed cancer in women (excluding skin cancer) in the United States, developing in approximately one in eight women during their lifetime. The incidence of this disease is decreasing, primarily among women older than 50 years.

Breast Cancer (Female) and the Environment
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 yet been established. Exposure to chemicals, such as poly aromatic hydrocarbons (PAH), benzene, and organic solvents, and passive smoking have been suspected of causing breast cancer, but the evidence is inconclusive. 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, existing studies do not support an association between pesticides and industrial products and breast cancer.

Exposure and Risk
The exact causes of breast cancer are unknown; however, women who are in certain categories are at increased risk for breast cancer. Risk factors may include:

• Older age
• White ethnicity
• Obesity (after menopause)
• Dense breast tissue (after menopause)
• High estrogen levels
• Early onset of menstruation (before age 12)
• Later age of first pregnancy
  
• Having no or few children
• Late onset of menopause (after age 55)
• Family history of breast cancer
• Certain genetic mutations
• Certain types of benign breast disease
• Personal 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

Reduce Your Risk
Most women in whom breast cancer develops have few or 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.

Tracking Breast Cancer
NH EPHT is tracking the incidence and morbidity of breast cancer. Data about breast cancer in New Hampshire will soon be available on the Environmental Health Data Integration Network (EHDIN).