By: Stacey Colino
Excerpt: "It's no secret that breast cancer is a mysterious disease, with many different risk factors. Some of these are well-recognized (genetic and reproductive factors, for example), while others are not. Now a new dimension has been added to the blurry picture: In a comprehensive review of 158 epidemiological studies from the last 10 years, published in October in the journal Environmental Research, researchers found that environmental chemicals we're all exposed to daily are a significant risk factor for breast cancer. Besides identifying chemicals that are of particular concern, the researchers found that exposures to these chemicals during key windows of vulnerability – namely, when a baby is in the womb, during puberty and during a woman's first pregnancy – increases a woman's risk of developing breast cancer later in life.
"Those are the times when the breast is growing and developing and reaching its mature state," explains study co-author Julia Brody, executive director and senior scientist at the Silent Spring Institute in Newton, Massachusetts, which conducted the research. "It's like a tree with a lot of buds and branches: As the breast develops, the ducts develop in a tree-like structure. When the breast reaches the final stage [of maturity] at the end of the first pregnancy, the end buds are fully developed and less vulnerable to carcinogens."
In particular, the review found that early exposure to DDT (an insecticide that's no longer used), dioxins (which are released from combustion processes and emissions from waste incineration), the highly fluorinated chemical PFOSA (short for: perfluorooctanesulfonamide, which has been used to repel grease, water and stains in consumer products) and air pollution is associated with a two- to fivefold increased risk of developing breast cancer. Certain environmental chemicals may have a more damaging effect at different points in a woman's breast development. "In utero exposure to dioxins and PFOA [perfluorooctanoic acid] can delay mammary gland development, which can lead to changes in how women lactate," says lead author Kathryn Rodgers, a scientist at the Silent Spring Institute."