Breast cancer clearly has a genetic component, but "routine environmental exposures and lifestyle may play a major role," according to a recent groundbreaking 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 have been shown to 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."
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.
A wide variety of prescription drugs have been found to produce mammary tumors in animals-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
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 workers in the electronics industry. Benzene, to which we are exposed from gasoline at the pump and from lawn mowers and other appliances that might be stored in garages and basements, is a potent mammary carcinogen, according to Silent Spring researchers.
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 U.S., 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.
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 U.S. have been found to be contaminated by pesticides and dry-cleaning chemicals.
Researchers broadly agree that women's exposures to natural estrogens over time increases the risk of breast cancer. However, it's been 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.
It wasn't until 2005 that 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 fortunately on the wane.
Toxins in food
Food can be tainted by pesticides sprayed on crops; antibiotics fed to poultry and other meat sources, 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 United States (banned in Canada and Europe) containing insulin-like growth factor 1 may put women at increased risk. Also, grilled or charred meat and fish contain various mutagenic agents that are formed naturally in the grilling process.
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 and the manufacture of products that contain chlorine, like bleached food cartons.
Most everyone agrees that limiting alcohol consumption can reduce the risk of breast cancer, but the connections appear to 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 6 studies that examined 322,647 women, each additional 10 grams of alcohol consumed daily (about one drink) equated to an added 9 percent risk of breast cancer.
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 Erie and Niagara counties in New York state 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, therefore suggest that exposure in early life to high levels of PAHs may increase one's risk of postmenopausal breast cancer.
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.
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.