Environmental Links to Breast Cancer

Environmental Links to Breast Cancer: The environmental breast cancer movement is a health social movement that addresses breast cancer by strategically challenging the science on etiology, diagnosis, treatment, and prevention. It engages scientific discourse in arguing that the toxic substances found in air, water, food, products, and our everyday environments at work and at home contribute to the development of breast cancer and other health problems.

Genetics alone cannot explain the rise in breast cancer incidence in the United States. Incidence has been increasing about 1 percent per year for the past sixty years, and rose by more than 40 percent between 1973 and 1998. Only 30 percent of breast cancer cases are attributed to the generally accepted risk factors, and notably, the longer immigrant women live in the U.S. the more likely they are to get breast cancer. Thus, international, national, state, and community-based organizations have been evaluating the role of environmental exposures in cancer.

The U.S. National Toxicology Program (NTP) identified substances and exposures are known or suspected to cause cancer, including:

  • naturally occurring exposures (e.g., ultraviolet light, radon gas, infectious agents)
  • medical treatments (e.g., chemotherapy, radiation, immune system-suppressing drugs)
  • workplace exposures
  • household exposures
  • pollution
  • and lifestyle factors

The Strategy and Implementation Plan for the International Agency for Research on Cancer (IARC) states that,

“The environment (defined in its broadest sense to include lifestyle, nutrition and occupation, in addition to physical, chemical and biological factors), plays a role in the overwhelming majority of cancers and consequently, at least in principle, the majority can be prevented. However, despite advances in identifying a number of major human carcinogens there remain a significant proportion of cancers for which the etiology is unclear.”

In 2003 the Breast Cancer and the Environment Research Program (BCERP), a joint effort funded by National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute began studying the impact of prenatal-to-adult environmental exposures that might predispose a woman to breast cancer.

NIEHS concludes that, “Most experts agree that breast cancer is caused by a combination of genetic, hormonal, and environmental factors.” After seven years of research the NIEHS stated:

“Reports are already pointing to weak relationships between exposure to these endocrine disruptors and the early onset of puberty. This factor may be one of the pieces in the complex puzzle that alters risk of breast cancer. Further studies are under way within the BCERP to understand the impact of indoor pesticides, heavy metals, diet, pregnancy, and hormone-like substances found in cosmetics and sunscreen.” 

The largest state-funded research effort in the nation, the California Breast Cancer Research Program, was established in 1993 also based on the premise that environmental factors play an important role in cancer development.

Community-based organizations such as the Silent Spring Institute founded in 1993 also argue that the rise in breast cancer incidence is not surprising given the amount of synthetic chemicals that entered the marketplace after World War II, which contain chemical carcinogens known to damage DNA, promote tumor growth, and increase the carcinogenic susceptibility of mammary glands.

The Breast Cancer Fund‘s seminal report State of the Evidence continually reviews the body of research about the timing of toxic exposures, low-dose exposures at environmentally significant levels, real-life mixtures of exposures; and the complexity of interactions between environmental and other risk factors for breast cancer. The NIEHS cites the Breast Cancer Fund’s State of the Evidence report as a key resource on the topic.

Indeed, there is a large body of evidence suggesting environmental links to breast cancer. At the same time, toxic exposures do not usually cause disease single-handedly, save for intense acute exposures.

What’s more likely is that there is a delicate balance among exposures over time, accumulated genetic changes resulting from exposures, protective factors, susceptibility, disease heterogeneity, and differing mechanisms of action brought upon by chemical compounds. Together, these set the conditions, or not, for cancer. The mechanisms are not clear cut. What is clear is that the environment matters.


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