Breast Cancer Suspects

bhaktajan · March 10, 2008

Breast Cancer Suspects

By Francesca Lyman for MSN Health & Fitness

Breast cancer clearly has a genetic component, but "routine environmental exposures and lifestyle may play a major role," according to a recent ground-breaking study by the Silent Spring Institute and Susan G. Komen for the Cure. The study, published in Cancer, a journal of the American Cancer Society, uncovers 216 common chemicals that cause breast tumors in animals and reviews medical literature, including some studies that reveal environmental factors to be influential "in the vast majority of cancers."

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Tailpipe Toxins

At the top of the list of common, potent mammary carcinogens are components of car and truck exhaust. Included on this list are PAHs (polycyclic aromatic hydrocarbons)—products of combustion—which have been linked to breast cancer in men as well as women.

Tobacco Smoke

Like car and truck exhaust, tobacco smoke is a source of many PAHs. Among these are dibenz[a,h]anthracene, considered by EPA to be “probably carcinogenic to humans” as well as mutagenic—meaning that it can cause genes to mutate. It’s laced with many other cancer-causing substances as well, such as dibenzo[def,p]chrysene.

Industrial Combustion Sources

Just as components of car exhaust have been linked to breast cancer and a long list of other illnesses, air pollution from refineries and coal plants also compounds the load. Researchers studying air pollution in <st1>:PNew York </st1>:PState found a higher risk of breast cancer among post-menopausal women whose birth addresses were near locations recording higher levels of PAHs. The researchers, who used historic air pollution data dating back to the 1960s to measure these trends, thus suggest that exposure in early life to high levels of PAHs may increase one's risk of postmenopausal breast cancer.

Drinking Alcohol

Most everyone agrees that limiting alcohol consumption can reduce the risk of breast cancer, but the connections get stronger with each new study. Natural cancer-causing substances—primarily urethanes—are found in alcohol, including wine and ale beers. In a recent analysis of six studies that examined 322,647 women, each additional 10 g of alcohol consumed equated to an added 9 percent risk of breast cancer.

Toxicants in Food

Food can be tainted by pesticides sprayed on crops, antibiotics used on poultry and other meats, and hormones injected into cattle, sheep and hogs. Some foods may increase the risk of breast cancer by increasing circulating levels of estrogen, so Silent Spring researchers advocate additional research in this area. They point to the fact that milk sold in the <st1:city w:st="Erie</st1:City"> and Niagara counties in <st1:place w:st=" /><st1:country-region w:st=" on="">United States</st1:place> (banned in <st1:country-region w:st="on">Canada</st1:country-region> and <st1:place w:st="on">Europe</st1:place>) containing insulin-like growth factor 1 may put women at increased risk. Also, grilled or charred meat and fish contain various mutagenic agents that occur naturally in the grilling process. </st1:city>

Acrylamides—found in French fries, breads and cereals cooked at very high temperatures—pose problems, as do foods contaminated by styrene from polystyrene (Styrofoam) containers. Fish can also be contaminated with a variety of long-banned chemicals like PCBs, which have been linked to breast cancer, as well as by dioxin, a product of incineration.

Ionizing Radiation

In 2005, the National Toxicology Program classified x-rays and gamma radiation as causing cancer in humans, but ionizing radiation has long been regarded as the most established environmental risk factor for breast cancer.

We're exposed to x-radiation from medical x-rays, mammograms and other radiopharmaceutical treatments. Though these technologies offer great benefits, unnecessary exposure should be avoided.

Our greatest exposure to radiation is from the gamma rays in natural sunlight, which also provides us with beneficial Vitamin D. We get increased radiation from plane travel, as a result of greater proximity to the sun's rays and because the radiation is less filtered by clouds and particulates. If you live or work close to nuclear power plants or lived in the era of atmospheric testing of nuclear weapons (1945-1980) you will also have accumulated higher doses of this radiation. According to the National Toxicology Program, those radioactive doses are on the wane.

Hormone Supplements

Researchers broadly agree that women’s exposures to natural estrogens over time increases the risk of breast cancer. However, it is only recently that synthetic estrogens and progesterones have been linked to a higher risk for breast cancer.

Findings from the ongoing Million Women Study and the Women’s Health Initiative have found that certain kinds of Hormone Replacement Therapy (HRT), used to alleviate menopausal symptoms, put women at increased risk of breast cancer.

The U.S. Food and Drug Administration has advised women to ask their doctors about the benefits of taking estrogen and progestin compared to the risks—and, if they decide to use them, whether hormones should be taken “at the lowest doses for the shortest duration to reach treatment goals.”

Drinking Water Contaminants

Disinfecting products used to clean water help kill bacteria and keep disease in check. However, Silent Spring researchers caution that some disinfection byproducts of chlorinating water cause mammary tumors in rodents. There’s strong evidence for their causing cancer in humans as well. Likewise, many drinking water systems across the <st1:country-region w:st="on"><st1:place w:st="on">U.S.</st1:place></st1:country-region> have been found to be contaminated by pesticides and dry cleaning chemicals.

Household Chemicals

Stain-resistant and flame-retardant chemicals have found their way into our lives—in our carpeting, furniture, clothing, cookware, cosmetics, lubricants, paints, and adhesives. Widely detected in blood samples in the <st1:country-region w:st="on"><st1:place w:st="on">US</st1:place></st1:country-region>, PFOA (perfluorooctanoic acid) has been found to cause breast cancer in animals and is under further investigation.

Silent Spring Institute researchers also point to chlorinated solvents used in paint removers, varnishes, wood sealants, fabric cleaners, dry cleaning chemicals and septic tank cleaners as being suspected human carcinogens.

Gasoline, Benzene, Fuels and Solvents

Occupational studies have mainly focused on men, but a few studies on women workers have turned up elevated levels of breast cancer among those exposed to various petrochemical solvents—particularly women working in chemical factories and dry cleaning shops, hairdressers, nurses in health and science laboratories, and electronics industry workers. Benzene, to which we are exposed in gasoline at the pump and in lawn mowers and other appliances that might be stored in garages and basements, is a potent mammary carcinogen, according to Silent Spring researchers.

Pharmaceuticals

A wide variety of prescription drugs have been found to produce mammary tumors in animals—everything from Reserpine, used for the treatment of mild or moderate hypertension, to Furosemide for pulmonary edema. Many anti-cancer drugs are also known human carcinogens. Check the study's “browse” function under pharmaceuticals.

Miscellaneous Chemicals, Dyes, Whitening Agents

In January 2003, the federal Centers for Disease Control and Prevention reported their findings on human exposure to environmental chemicals, revealing some 116 toxic and cancer-causing chemicals in the blood and tissues of human volunteers chosen to represent our population. Among the compounds they found were multiple pesticides linked to breast cancer, dioxins that are products of incineration, and other chemicals.

Can our “body burdens” be lightened? Silent Spring researchers advocate reducing as many “preventable” exposures from industrial chemical byproducts as possible. Examples abound: 1,4 dioxane, a contaminant in detergents and shampoos, for example, and fluorescent whitening agents, both have been found to cause breast cancer in animals. The researchers argue that most chemicals used in hair dyes and cosmetics have not been tested for their health effects.

Francesca Lyman is the author of several environmental books, including The Greenhouse Trap and Inside the <st1:place w:st="on"><st1>:PDzanga-Sangha Rain Forest</st1></st1:place>. Her work has appeared in The New York Times, The <st1:state w:st="on">Washington</st1:state> Post, Ms. Magazine, <st1:city w:st="on"><st1:place w:st="on">Seattle</st1:place></st1:city> Metropolitan, MSNBC Online, This Old House, and Horizon Air magazines.