Breast Cancer: Industrial Byproduct?

Breast cancer is the leading cause of death by cancer among women between the ages of 18 and 54 and the second highest for older women, and its incidence is rising. It now strikes one in eight American women, killing 44,000 every year. Yet its causes and the reasons behind its rise remain largely a mystery.

"The rate of breast cancer has been going up steadily every year by 1% since the 1940s, and can't be explained by early detection, changes in the gene pool or the general aging of the population," says Rachel Morello-Frosch, president of the board of San Francisco-based Breast Cancer Action, and survivor of breast cancer diagnosed at age 28. Of the 180,000 cases of breast cancer diagnosed every year, up to 70% cannot be explained by traditional risk factors, such as family history, age at menarche and menopause, whether one has borne and breastfed children, and lifestyle risks such as diet, alcohol consumption and exercise.

Many researchers and activists are asking whether exposure to carcinogens in the environment -- including some of the 75,000 synthetic chemicals released since World War II -- could be responsible. "But say that to people, and they think you are a conspiracy theorist," Morello-Frosch says.

Indeed, articles about environmental causes of cancer in the mainstream press, such as those by Gina Kolata, a science reporter at The New York Times, tend to be dismissive. For example, in her review of "Rachel's Daughters: Searching for the Causes of Breast Cancer," a documentary aired on HBO in October 1997, Kolata says that the film, which interviews nearly two dozen scientists on the possible role of environmental pollutants in cancer, has "little or no basis in fact."

In fact, breast cancer rates were higher in the 339 U.S. counties with hazardous waste sites and groundwater contamination than in counties without such sites, according to a 1989 EPA study published in Archives of Environmental Health. Suffolk County on Long Island, New York, has one of the highest breast cancer rates in the country. There, radiation from four nuclear reactors and contaminants from 22 Superfund hazardous waste clean-up sites seep into soil, water and air. A 1985 study in Preventive Medicine found that breast cancer rates in New Jersey -- where 21 counties have hazardous waste disposal sites -- were the highest in the country.

Around the country, women are advised that a healthy diet, regular exercise, and drugs like tamoxifen are the ways to reduce breast cancer risk. Multi-million-dollar campaigns advocate yearly mammograms for women as young as 40. While early detection can save lives, this places the burden of risk reduction on the individual rather than the industries that release toxins and profit off the drugs and mammograms (see "Profiting Off of Breast Cancer" in The Green Guide #60).

Estrogen & Its Impostors

Ever since the Italian physician Bernardino Ramazzini discovered higher rates of breast cancer among nuns in the 18th century, the medical community has known that reproductive factors play a role in breast cancer. But it was not until about 20 years ago that breast cancer researchers began focusing on the female sex hormone estrogen, which, when elevated, causes breast cells to grow. More than two-thirds of all breast cancers in the U.S. are influenced by estrogen.

Natural estrogen, produced by the body, regulates the reproductive cycle, prevents bone loss and reduces the risk of heart disease. Most estrogen that circulates in the blood is taken up by estrogen-binding proteins and diverted to the liver to be excreted.

But women with higher levels of circulating unbound estrogen have greater risks of developing breast cancer than women with lower levels, researchers at New York University and the National Cancer Institute have discovered. Early puberty and late menopause increase risk by prolonging a woman's exposure to unbound estrogen. Not having children, delaying pregnancy, and not breastfeeding are other risk factors. Xenoestrogens, such as synthetic hormones and estrogen-mimicking chemicals, may also encourage cancerous cells to grow.

About 30% of American women between the ages of 50 and 65 take estrogen replacement therapy (ERT) to combat the risk of osteoporosis and heart disease. However, epidemiological evidence shows that extended use of ERT can increase breast cancer risk from 30% to 70%. A 1991 study published in the American Journal of Epidemiology found that 8% of all postmenopausal breast cancers in the U.S are caused by ERT.

Organochlorines

Some of the most-studied hormone disrupting chemicals, known as organochlorines, include PCBs and the pesticides DDT, kepone, chlordane, lindane and benzene hexachloride (BCH) -- all of which are now banned in the U.S. But other chlorinated pesticides like endosulfan, methoxychlor, and triazine herbicides continue to be used. Some organochlorines remain in human fat for up to 30 years, unlike natural hormones which are excreted from the body within a few hours, according to Mary Wolff, Ph.D., a breast cancer researcher and professor at Mount Sinai Medical Center.

Several studies have shown higher blood levels of organochlorines in women who had breast cancer than in those who did not. But one study conducted at Harvard University in 1997 found no correlation between blood levels of DDT, DDE or PCBs and breast cancer risk. Gina Kolata and one of her favorite scientific experts, Dr. Stephen Safe of Texas A&M University, have concluded in The New York Times and the New England Journal of Medicine, respectively, that the Harvard study proves that DDT, DDE and PCBs can now be ruled out as causes of breast cancer. (Dr. Safe also contracts with chemical manufacturers to test their products and is listed as an "expert" on promotional materials for the Chemical Manufacturers Association and the American Plastics Council.)

The most recent study, published in the December 1998 Lancet, showed a positive association between the pesticide dieldrin and breast cancer. Calling for more research, Dr. Wolff says, "It's important to distinguish between the different forms of the chemical under study, as not all PCBs, for instance, are estrogenic."

Epidemiological studies can provide important clues. A study published in the October 1997 issue of Environmental Health Perspectives (EHP) suggests that high rates of breast cancer in Hawaii may be linked to 40 years of widespread organochlorine pesticide use on pineapple fields that has contaminated groundwater. Between 1970 and 1985, the incidence of breast cancer among Japanese women living in Hawaii increased 42%, whereas rates for that group in other parts of the U.S. did not rise by more than 20%. A statistical analysis of Kentucky residents published in EHP in November 1997 suggests a modest association between exposure to triazine herbicides, such as atrazine, through ground and surface waters and increased incidence of breast cancer.

Potent Plastics

In 1994, British researchers found that trace amounts of alkylphenol ethoxylates (APEs), used in household detergents, hair dyes, spermicides, and plastic, are estrogenic in fish, birds and mammals. Nonylphenol, an alkylphenol which can leach from polystyrene, encourages growth of breast cancer cells in laboratory tests.

Phthalates and vinyl chloride, which may be present in polyvinyl chloride (PVC) products, are suspected carcinogens and hormone disruptors. A 1977 study published in the Journal of Occupational Medicine (JOM) found that female workers breathing vinyl chloride vapors showed a 36% increase in breast cancer fatalities. Lab rats fed PVC dust and exposed to vinyl chloride vapors developed breast cancer, even at low doses, as reported in JOM in 1994. Bisphenol A, an ingredient in the polycarbonate plastic used for some baby bottles and the lining of some food cans, also makes breast cancer cells grow.

Bisphenol A, APEs, phthalates and organochlorine pesticides have been found in wastewater and septic systems in Cape Cod, Massachusetts, which has a breast cancer incidence rate approximately 20% higher than the rest of the state. Researchers at the Silent Spring Institute have been studying drinking water contamination by hormone disruptors as a possible explanation, as Cape Cod has a history of heavy pesticide use, and its sandy soils increase the likelihood of seepage. "Studying places with higher breast cancer incidence is a great opportunity to learn more about what role environmental factors may play in the rise of breast cancer," says Julia Brody, Ph.D., executive director of Silent Spring Institute.

rBGH & Hormone Residues in Food

Even before Monsanto's 1993 market release of rBGH, a synthetic bovine growth hormone that makes cows produce more milk, consumer advocates and scientists warned that inadequate testing put milk drinkers at risk. One major concern: Milk produced from cows injected with rBGH contains more Insulin-like Growth Factor-1 (IGF-1) than milk from untreated cows. Several studies show that this IGF-1, the same as that produced by humans, promotes the proliferation of breast cancer cells. In May 1998, a study published in Lancet revealed that elevated levels of IGF-1 in blood levels of premenopausal women increases their risk for breast cancer up to seven-fold. "Most studies linking dairy products with breast cancer used milk from untreated cows, but rBGH elevates IGF-1 levels to two to four times that in untreated milk," says Neal Barnard, M.D., president of Physicians Committee for Responsible Medicine.

The U.S. Food and Drug Administration (FDA) has maintained that IGF-1 cannot survive digestion in the human gastrointestinal tract. But, in late September 1998, Health Canada, the Canadian counterpart to the FDA, revealed that Monsanto failed to adequately investigate potential health risks from milk with elevated levels of IGF-1. "We [now] know that IGF-1 moves across the digestive tract into the bloodstream," says Dr. Barnard.

Hormones are also used in beef production. From the 1940s to the 1980s, the U.S. cattle industry fed cattle DES, a synthetic hormone once prescribed to prevent miscarriages that increased rates of breast cancer in DES daughters. After DES was banned for use in cattle in 1979, ranchers switched to different synthetics and natural sex hormones.

In general, consumption of meat and fatty foods increase hormone levels in the body. And women who eat very well-done meat regularly may have five times the risk of developing breast cancer, according to a study published in the November 1998 Journal of the National Cancer Institute. Science News reported a study the same month showing that the more well done the meat, the more carcinogenic heterocyclic amines (HCAs) it has.

It may take years before scientists uncover exactly how xenoestrogens cause cancer, but the evidence already suggests that there are reasons to be concerned about these synthetic chemicals. "As we go forward, activists and scientists together, we must debate the question of what constitutes sufficient evidence to advocate public health action even as we advocate for more research," wrote biologist Sandra Steingraber, Ph.D., author of Living Downstream, in the April 1997 issue of Environmental Health Perspectives. We needn't wait, as too many did with tobacco, for conclusive evidence before taking action for our own sake and the health of future generations.