Breast Cancer Risk and the Air We Breathe
Posted May 5, 2009
Last week, the American Lung Association came out with its annual State of the Air report, and concluded that six out of every ten Americans live in communities with unhealthy air. I read these results not only as the head of environmental organization, but also as a breast cancer survivor.
What does breast cancer have to do with air pollution? Most of us are familiar with the connection between smog-covered skies and asthma attacks. (See my colleague David Pettit's recent post about what Southern California's pollution does to its residents.)
But there are also over 200 chemicals in air pollution--called polycyclic aromatic hydrocarbons (PAHs)--that may also lead to cancer, including cancer of the breast. PAHs are the chief component of soot, and enter the air via burning of coal, oil, diesel, gasoline, wood, garbage, tobacco, and even charbroiled meat.
I also read the study's results as a mother. My three daughters--who already have an elevated risk of breast cancer because of my diagnosis--have recently lived in the heavily polluted cities of Johannesburg, Amman, and New York. The United States has taken some steps to reduce air pollution--it still needs to do much more--but tens of millions of women and girls around the globe are exposed to alarmingly high levels of carcinogenic pollutants.
What Air Pollution Can Do to Breast Tissue
Scientists are just beginning to understand the connections between PAHs and breast cancer, but here is what they have discovered so far.
PAHs have caused mammary tumors in rats, and they appear to increase breast cancer risk in a variety of ways. Common PAHs mimic estrogen, and elevated levels of the hormone are known to contribute to tumor growth.
But there is another, more insidious way that PAHs threaten our health. Once in the body, PAHs can bind to genetic material (DNA) and form something with the ungainly name of PAH-DNA adducts. These adducts jumpstart a series of cell changes that can short circuit cell signals, interfere with DNA repair within cells, and ultimately lead to DNA mutations.
I know from my experience being tested for the so-called breast cancer genes that genetic mutations can lead your cells down paths you don't want them to go.
Several studies have connected high levels of PAH-DNA adducts and breast cancer. One study, from the Long Island Breast Cancer Study Project, discovered that women with the highest levels of PAH-DAN adducts had a 50 percent increased risk of breast cancer. Another compared breast tissue from women who had breast cancer with women who had benign breast diseases and found that the cancerous samples were two times as likely to have PAH-DNA adducts.
PAHs, Cigarette Smoke, and Breast Cancer Risk
PAHs don't just come from diesel trucks and industrial smoke stacks. They also come from cigarette butts. PAHs in tobacco smoke have been linked to breast cancer, but there is a window when women are particularly vulnerable: the teen years.
If a girl is exposed to secondhand smoke during the time when her breasts are developing through puberty, she is more at risk for getting breast cancer later than a woman who breathes in secondhand smoke after she gives birth to her first child.
A study sponsored by the California Air Resources Board found that women exposed to secondhand smoke have up to 90 percent greater risk of developing breast cancer. And in 2006, the California EPA concluded: "overall, the weight of evidence...is consistent with a causal association between [environmental tobacco smoke] exposure and breast cancer in younger, primarily pre-menopausal women."
Now We Need Prevention
There is a lot more we need to learn about the way PAHs interfere with human cell function, but we know enough to start protecting ourselves from this hazard.
Here are NRDC's recommendations for reducing breast cancer risk for women and their daughters:
- Pass tougher standards for diesel-burning vehicles, a leading source of PAHs. Thanks in part to NRDC, pollution from diesel trucks and even off-road vehicles has declined, but diesel fleets could still become cleaner.
- Enforce the Clean Air Act provisions that protect the public against cancer risks greater than 1 in 1 million caused by toxic air pollution from industrial polluters. The Bush administration refused to achieve this level of protection and instead adopted policies accepting cancer risks as high as 250 in 1-million and even 400 in 1 million. The Obama administration can and should do better.
- Forbid the use of federal funds in connection with any project--such as an expansion of diesel-heavy shipping terminal--that can be shown to increase cancer risk by more than 1 in a million.
- Require that all existing coal-fired power plants adopt modern pollution controls.
- Ban the incineration of industrial waste.
- Extend nonsmoking bans in the workplace and public spaces to reduce the risks from secondhand smoke.
Here are a few ways you can protect yourself from PAH exposure:
- Stop smoking, urge those you love to stop smoking, and limit your time in the presence of smokers.
- Avoid spending significant time in the freeway traffic, where in-vehicle exposure can run high.
- Avoid living, working, or attending school directly adjacent to freeways, where pollution levels spike (for instance, within 500 feet).