Environmental factors may cause many breast cancers, report says

Up to half of all new breast cancers may be caused by environmental factors — including exposure to everyday chemicals — rather than heredity or lifestyle, a new report says. Released this week by the Breast Cancer Fund and Breast Cancer Action, “State of the Evidence” analyzes the findings of more than 350 ecological, epidemiologic, and experimental studies of breast cancer, with an eye to determining why an American woman’s risk for breast cancer has nearly tripled in the past 40 years. The groups’ analysis found persuasive scientific evidence that implicates some of the 100,000 synthetic chemicals in use today, including bovine growth hormone, dioxin, and phthalates. Little is known about how these substances may affect women when they’re combined.