Peace and Environment News * September 1994

Breast Cancer and the Chlorine Connection

by Mei-Lin Stichbury

Breast cancer and reproduction are probably two of the most important medical issues concerning women today. Breast cancer is presently the most common type of cancer occurring among North American women. Increasing evidence shows that environmental contamination may contribute to the incidence of breast cancer and also to birth defects. Organochlorines, a class of industrial chemical produced from chlorine, are especially suspect.

Organochlorines are a class of chemicals in which chlorine is bonded to organic matter. They were first produced around the turn of the century after industry began making mass quantities of chlorine. At present, industry produces about 40 million tons of chlorine per year. Most of this chlorine is used to make organochlorine products such as plastic, solvents, pesticides and refrigerants. Many more organochlorine by-products are created as a result of bleaching pulp for paper or killing bacteria in the process of disinfecting wastewater. These by-products include chlorinated dioxins, furans and related compounds.

What is unique, yet dangerous about many organochlorines is that they are extremely stable and can persist in the environment for long periods of time. They can also be easily transported throughout the environment. Once released, these chemicals can be distributed around the world on air currents and in water. Furthermore, many organochlorines accumulate in living tissue, especially fatty tissue of animals and humans. Humans, being at the top of the food chain, are at greatest risk of accumulating high concentrations of these chemicals. Greenpeace says that humans now have organochlorine concentration levels thousands or millions of times greater than that of the surrounding environment. Some 177 different organochlorines have been found in fat, breast milk, blood, semen and breath in people of the U.S and Canada.

Experimental and empirical data along these lines have led researchers to think the chemicals in animal fat may be contributing to the high incidence of breast cancer in North American women. North American women, and similarly women in other industrialized countries, have a higher percentage of their diet coming from animal fat than women in less industrialized countries. Nations with high per capita fat intake also have high breast cancer rates. Since many environmental pollutants, including organochlorines, tend to accumulate in animal fat, researchers believe that organochlorines may be a significant contributor to breast cancer in addition to hereditary and hormonal factors.

Many organochlorines have, in fact, been found to cause cancer in humans and laboratory animals. It has been suggested that because organochlorines are human-created and foreign to nature, humans have not evolved effective means to metabolize them or rid them from their bodies. A recent report from Greenpeace summarizes several ways by which organochlorines can promote breast cancer:

• Some organochlorines (vinyl chloride and dichloroethane) cause mutations in genetic material, which can then give the wrong instructions to the rest of the cell for cell division, differentiation and proliferation;
• Some organochlorines (dioxin, chlorobenzenes, chlorinated pesticides, and chlorinated solvents) strengthen the ability of other chemicals to cause cancer by inducing enzymes that transform them into a more carcinogenic form;
• Organochlorines such as dioxin and PCBs interfere with the body's natural controls on cell growth and differentiation;
• Some organochlorines mimic or interfere with natural hormones like estrogen;
• Organochlorines, namely the dioxins and the solvent trichloroethane, may suppress the immune system's mechanisms for defending against tumorous cells.

Interference with or mimicking of hormones like estrogen is a particularly important cancer-promoting mechanism. Organochlorines such as DDT, methoxychlor, mirex and others can bind directly to the estrogen receptor of the cell. And laboratory experiments suggest that estrogen seems to be essential for the initiation of mammary gland tumors in animals and humans. In fact, the types of breast cancer that are increasing most rapidly, especially among older women, are those that respond to estrogen. Some breast cancers contain large amounts of the estrogen receptor, a protein to which estrogen must bind in order to trigger associated biochemical events. Some breast cancers, on the other hand, do not. The incidence of estrogen-receptor positive cancers, where there is a larger than normal amount of estrogen receptor, increased by 131 percent from the mid-1970s to the mid-1980s. On the other hand, estrogen-receptor negative cancers increased by 27 percent or less.

At the same time that some organochlorines mimic estrogen, the dioxin family is capable of interfering with natural feedback systems by which the body regulates the metabolism and synthesis of estrogen. Dioxins are found in pesticides and herbicides and are also produced when chlorinated compounds are burned. Exposure to organochlorines that function in this manner early in life can result in permanent alteration of systems that control estrogen and other sex hormones. Studies have found increased risk of breast cancer among women born to mothers with indications of high estrogen levels during pregnancy. This may further support the hypothesis that transfer of accumulated organochlorines from generation to generation may contribute to breast cancer.

Apart from cancer risks, dioxins also pose problems in the form of birth defects and infertility. Exposure to dioxin begins as the fetus receives it from foods ingested by the mother. Dioxin can also accumulate in a mother's breast milk, leading to additional exposure. An article by Greenpeace called "Whitewash: The Dioxin Cover-up" documented several cases of birth defects and unusually high numbers of miscarriages in places where pesticides containing dioxins were being sprayed. In one valley where Agent Orange was sprayed, one woman had fourteen miscarriages and another woman had two miscarriages. The one son she did have was born with defective lungs and liver. Many say these incidences are evidence there is a link between herbicide and pesticide spraying and birth defects.

What We Can Do

There is no evidence that organochlorines directly cause breast cancer or reproductive problems in women, but there is enough evidence to show there may be a strong association. There are many things that we can do to reduce the amount of chlorine being used in industry and to reduce the risks organochlorines present.

• Choose natural cleaners such as baking soda and white vinegar rather than commercial ones, which often contain chlorine bleach.
• Remove chlorine from drinking water by running it through an attached filtration system.
• Try to avoid drycleaning, because the main chemical used in the process is a carcinogenic organochlorine. If you have to dryclean, air out items afterwards.
• Limit the amount of meat in your diet, since organochlorines accumulate in animal fat. Eat your greens instead!
• Use 100% recycled, chlorine-free paper or use paper alternatives like hemp paper. The process of making paper white includes the use of chlorine bleach which contains dioxins. Wastewater discharged from pulp mills also contains hundreds of other organochlorines. 100% recycled paper and some hemp paper can be purchased from Arbour Recycled Products at 800 Bank Street.
• Reduce paper consumption in general.
• Avoid using pesticides in caring for your lawns and gardens.
• Avoid synthetic carpets, as the compounds in a lot of new carpeting include pesticides.
• Use chlorine-free diapers and sanitary products. If possible use cloth reusable products and use a diaper service.
• Write to the company that produces your usual brand of hygiene product and tell them you would prefer non-chlorine-treated products.
• Write to your federal MP and ask for zero discharge regulations that would reduce or eliminate chlorine compounds in the pulp bleaching process.

Mei-Lin Stichbury is a student in Environmental Sciences and a regular contributor to the PEN.

Converted December 3, 2000 - Lg

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