edited by Nancy Evans
© 2003 by The Breast Cancer Fund and Breast Cancer Action

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B reast cancer rates have been climbing steadily in the United States and other industrialized countries since the 1940's. In 2002 in the United States alone, breast cancer struck an estimated 205,000 women and killed nearly 40,000. Billions of dollars have been spent in an effort to stem this unrelenting tide; yet as many as 50 percent of breast cancer cases remain unexplained by the characteristics and risk factors associated with the disease.

Ionizing radiation is the best established environmental cause of human breast cancer. Yet powerful scientific evidence points to some of the 85,000 synthetic chemicals in use today as responsible for many of the unexplained cases of cancer in general and potentially also of breast cancer. While scientists have not yet developed an ideal method for linking chemical exposures to breast cancer, several types of research -- experimental, body burden and ecological studies -- provide strong evidence of the connection between chemicals and breast cancer.

Because the types of evidence vary, the strength of the evidence linking chemicals and breast cancer also varies. The strongest evidence linking chemicals to breast cancer is based on the fact that lifetime exposure to naturally produced (endogenous) estrogens increases the risk of breast cancer. New evidence strengthens the association between compounds that mimic these natural estrogens, such as hormone replacement therapy and oral contraceptives, and increased risk of breast cancer. The National Toxicology Program now lists steroidal estrogens as known human carcinogens.1 Other compounds with estrogenic activity such as drugs like diethylstilbestrol (DES), plastic additives like bisphenol-A (BPA), polyvinyl chloride (PVC) (found in many consumer products), fuels such as benzene, and some pesticides like dieldrin have all been found to increase the risk of breast cancer. Synthetic chemicals strongly linked to breast cancer through experimental evidence include: organic solvents (used in many manufacturing processes, including the manufacture of computer components), polycyclic aromatic hydrocarbons (PAHs) (produced from combustion of fuels, including gasoline, diesel, and heating oil, cigarettes and other tobacco products, or by grilling meats and fish at high temperature) and 1,3 butadiene (a by-product of internal combustion engines and certain industrial processes).

There are also chemicals for which the evidence indicates a probable but less direct link to breast cancer. These chemicals include dioxin (created when plastics or other materials containing chlorine are burned), the pesticide DDT (dichloro-diphenyl-trichloroethane) and its metabolite and environmental breakdown product, DDE, and PCBs (polychlorinated biphenyls), previously used in the manufacture of electrical equipment and other industrial and consumer products.

Finally, there is evidence of chemicals that affect how the body functions in ways that suggest a possible link between these substances and breast cancer. These chemicals include the insecticide heptachlor, the herbicide atrazine, sunscreens, and phthalates, compounds used to make plastic soft and flexible.

We clearly have major gaps in our current knowledge about the links between breast cancer and the environment. Therefore, we need to focus our research efforts in areas that are most likely to provide useful information for framing public policies related to chemical exposures and our health. The types of research most likely to produce useful evidence will be those examining: (1) workplace exposures, (2) household exposures (3) evidence of human contamination through biomonitoring and (4) carefully conducted studies in areas where breast cancer incidence is greatly increasing and the use of chemicals has exploded.

We must pursue research that will lead to more definitive answers, including new recommendations from the first International Summit on Breast Cancer and the Environment sponsored by the U.S. Centers for Disease Control and Prevention, which was convened May 22-25, 2002. At the same time, the existing evidence linking chemicals to breast cancer demands that we act now as a society to begin removing many of these substances from our environment. Considerable resources are spent encouraging women to make changes in their personal lives in an effort to reduce their risk of breast cancer. But breast cancer is not just a personal tragedy; it is a public health crisis that requires political will to change the status quo.

This crisis must be addressed by beginning now to implement the precautionary principle as a matter of public policy. Under this principle, evidence of harm, rather than definitive proof of harm, is the trigger for policy action. In addition, the precautionary principle mandates that the burden of proof with regard to chemicals rests with the manufacturers to demonstrate that the substances are safe, rather than with the public to show that they are harmful. Finally, the precautionary principle rests on the democratic principle that government officials are obligated to serve the public's interest in human health and environmental protection.

THE FOLLOWING 5-POINT PLAN WILL HELP US REDUCE THE RISK OF BREAST CANCER AND ULTIMATELY END THE EPIDEMIC:

 

1. Phase out toxic chemicals that persist and accumulate in our bodies and in the larger environment.
   
    
2. Enact "sunshine" laws and enforce existing environmental protection laws to reduce the use of toxics by requiring companies to report how many tons of chemicals they use.
   
    
3. Practice healthy purchasing, with local, state and federal governments leading the way in purchasing environmentally preferable products, thereby creating an example for corporations and individuals to follow.
   
    
4. Hold corporations accountable for releasing cancer-causing chemicals into the environment and offer corporate incentives that encourage businesses to institute environmentally preferable policies and processes.
   
    
5. Monitor the chemical body burden in humans, using biospecimens (blood, urine, fat and breast milk) through a comprehensive community program that identifies the synthetic chemicals as well as their metabolic products in our bodies, establishes links to geographic areas and health outcomes, and initiates a plan to eliminate these contaminants.

We ignore at our peril the increasing evidence that chemicals are contributing to the rising tide of breast cancer. The obligation to understand this evidence, and begin to address it through the implementation of public policies that put health first, rests with all of us. It is in our power to change the course we are on. Now is the time.
 

Introduction - Purpose of This Paper - History of This Paper - New Research Highlights   What Do We Mean By Environment?   Why Chemicals?   Types of Research: A Primer - Laboratory Research - Body Burden Research (Biomonitoring) and Epidemiologic Research - Ecological Research   Evidence that Chemicals Cause Breast Cancer - Estrogens, Progestins and Breast Cancer - Synthetic Estrogens (Xenoestrogens) - The Phytoestrogens (plant estrogens) Hypothesis - Solvents - 1,3-butadiene - Aromatic Amines   Evidence Indicating a Probable Link Between Chemicals and Breast Cancer - DDT/DDE and PCBs - Polycyclic Aromatic Hydrocarbons (PAHs) - Dioxin   Evidence Indicating a Possible Link Between Chemicals and Breast Cancer - Heptachlor - Atrazine - Sunscreens (UV screens) - Phthalates (endocrine disrupting chemicals in plastics) and precocious thelarche

Moving Forward: Getting from Here to There in the Research Agenda - Workplace Exposures - Biomonitoring   Stop Fiddling While Rome Burns: Activists Call for Change   Appendix: Chemicals Shown to Induce Mammary Tumors in Animals   Glossary   Endnotes