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The Sneaky Breast Threats Around You

U.S. News & World Report - Health logo U.S. News & World Report - Health 11/1/2017 Stacey Colino

Chemical factory with smoke stack: Early exposure to air pollution is associated with a two- to fivefold increased risk of developing breast cancer. © (Getty Images) Early exposure to air pollution is associated with a two- to fivefold increased risk of developing breast cancer. How and when exposure to certain environmental chemicals can increase a woman’s risk of developing breast cancer.

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."

The Dangers in the Details

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.

PFOA is used in making non-stick coatings such as those for pans and other cookware and stain-resistant carpets, but the greatest exposure to humans comes from contaminated drinking water, according to the Centers for Disease Control and Prevention.

There are three primary mechanisms through which these environmental chemicals may increase the risk of breast cancer, Brody explains: by disrupting the normal growth and development of the breast since these chemicals are endocrine disruptors; by having carcinogenic effects since some of these chemicals damage DNA, which could lead to the start of a tumor; and by making a tumor grow. And some of these chemicals, such as those in air pollution, particulate matter, metals, volatile organic compounds, polycyclic aromatic hydrocarbons and nitro-PAHs, generated largely from diesel-powered vehicles, increase cell proliferation for estrogen-receptor cells, which could have implications for estrogen-receptor-positive breast cancers, Rodgers adds.

"Breast cancer is a complex disease, so these chemicals could have an additive effect in terms of building on each other's mechanisms, and multiple chemicals could act on the same pathway," Brody says. Meanwhile, a woman's genes may affect her vulnerability to certain environmental chemicals – for example, certain genes related to cell repair are important for mitigating the effects of air pollution, Brody says.

Video: Ways To Prevent Breast Cancer After 40 (courtesy Wochit News)

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Take-Home Implications

Many environmental health experts view these findings as a call to action. This review "continues to confirm the importance of considering windows of vulnerability in terms of early life exposures – we can't just be looking at exposures in adult women," says Dr. Ted Schettler, science director of the Science & Environmental Health Network (who was not involved in the study). "We should be acting on this information in terms of reducing exposure in humans rather than waiting for people to be harmed."

"One of the things that's important about this study is to use the evidence as a warning about newer chemicals," Brody says. "DDT has been banned, though it's still present in the environment – but more importantly we should be cautious about the chemicals that are in use and being introduced now. We don't want to wait another 50 years to find out they cause breast cancer. We need to develop new ways to anticipate chemicals that could cause breast cancer based on this model," – and regulate them accordingly.

In the meantime, the onus is on each of us to take steps to minimize our exposure to these hazardous chemicals. If you're in the market for a new car, consider fuel efficiency as a factor. "People don't really think of fuel efficiency as something that's important to breast cancer risk," Brody says. "If we have more fuel-efficient vehicles, we have less air pollution, which could help prevent breast cancer."

At home, a good starting place is to choose stainless steel pans or cast-iron pans instead of nonstick cookware and to opt out of getting stain-resistant coatings on carpets and furniture, Rodgers says.

For more strategies to help you minimize exposure to problematic chemicals, it helps to use the free smartphone app Detox Me. Developed by the Silent Spring Institute, the app provides simple, evidence-based tips on how to reduce exposure to a variety of harmful chemicals in your home. The Environmental Working Group offers tips on how to reduce toxic exposures in your home, and the Centers for Disease Control and Prevention provides advice on how to limit your exposure to chemicals at home, work and play.

Unproven risk for these products: It's true that avoiding certain household chemicals – such as dry-cleaning vapors and some pesticides – may cut your risk of developing cancer. But other ordinary household products and common medications once under scrutiny may actually pose little or no threat. The following slides update past claims about possible cancer causes. <br><br><b>Updated on April 25, 2017:</b> This article was originally published on Oct. 19, 2010. What Causes Cancer? 5 Unlikely Claims Explained

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