Environmental Causes of Breast Cancer: Research and Evidence

A growing body of scientific evidence links exposure to environmental factors, like radiation and synthetic chemicals, to an increased risk of breast cancer. An estimated 80,000 synthetic chemicals are in use today in the United States, 2 yet only 7 percent of these chemicals have been fully tested for their effects on human health. 3 Evidence shows they can contribute to the development of breast cancer, either by altering hormone function or gene expression. Many of these chemicals persist in the environment, accumulate in body fat and remain in breast tissue for decades.

Key Facts

• Environmental exposures—in combination with genetic predisposition, age at exposure and hormonal factors—have a cumulative impact and put women at greater risk for breast cancer according to two new articles. 4,5
• Women who move from countries with low breast cancer rates to countries with higher rates soon acquire the higher risk of their new country.
• A major study by Tufts University scientists demonstrated the profound effects of low-dose exposure to chemicals early in life. The scientists found that exposing pregnant mice to extremely low levels of bisphenol A altered the development of the mammary glands in their offspring at puberty. 6
• Triazine herbicides, the most heavily used agricultural chemicals in the United States, have been shown to cause mammary cancer in animals.
• Synthetic agents that mimic the actions of estrogens, known as xenoestrogens, are present in many pesticides, fuels, plastics, detergents and prescription drugs. 7 Chronic exposure to them may explain the increase in breast cancer in industrialized countries around the world.
• Phthalates are a group of hormone-disrupting compounds commonly used to render plastics soft and flexible. They are found in some varieties of nail polish, perfumes, skin moisturizers, flavorings and solvents, and have been shown to significantly increase cell proliferation in human breast cancer cells. 8

Learn More

Click here to read State of the Evidence 2008: The Connection Between Breast Cancer and the Environment, the Breast Cancer Fund’s landmark report that summarizes the evidence from more than 400 scientific studies, discusses major themes that are changing the state of the evidence and outlines the Breast Cancer Fund's public policy and research recommendations to reduce toxic environmental exposures linked to the disease.

Endnotes

1. Jatoi I, Anderson WF, Rao SR, Devesa SS (2005). Breast cancer trends among black and white women in the United States. Journal of Clinical Oncology 23: 7836-7841.
2. Carpenter DO, Arcaro K Bush B, Niemi WD, Pang S, Vakharia DD (1998). Human health and chemical mixtures: An overview. Environmental Health Perspectives 106(S6):1263-1270.
3. Bennett M, Davis BJ (2002). The identification of mammary carcinogens in rodent bioassays. Environmental and Molecular Mutagenesis. 39(2-3): 150-157.
4. Coyle YM (2004). The effect of environment on breast cancer risk. Breast Cancer Research and Treatment 84:273-288.
5. Mitra AK, Faruque FS, Avis AL (2004). Breast cancer and environmental risks: Where is the link? Journal of Environmental Health 66:24-32.
6. Munoz de Toro M, Markey C, Perinaaz R W, Luque EH, Rubin BS, Sonnenschein C, Soto A (2005). Perinatal exposure to bisphenol A alters peripubertal mammary gland development in mice. Endocrinology online doi:10.1210/en.2005-0340.
7. National Academy Press (1999). Hormonally active agents in the environment. ISBN-0309-06419-8.
8. Kim IY, Han SY, Moon A (2004). Phthalates inhibit tamoxifen-induced apoptosis in MCF-7 human breast cancer cells. Journal of Toxicology and Environmental Health 67:2025-2035.