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Your Environment. Your Health.

Breast Cancer

Introduction

Smiling senior woman sitting in couch at home

You Can't Change Your Genes, but You Can Change Your Environment

Identifying which environmental factors may increase the chance of developing breast cancer is the first step in figuring out how to avoid them.

About 12%, or 1 in 8, women in the U.S. will develop breast cancer during their lifetime. It is the second most common cancer among U.S. women, behind skin cancer.1 Breast cancer occurs mostly in women who are 50 years old or older. But men can also develop the disease. Each year in the U.S., about 245,000 cases of breast cancer are diagnosed in women and about 2,200 in men.2

Breast cancer is a disease in which cells in the breast grow out of control and may form a tumor. There are different kinds of breast cancer. If the cancerous cells spread to other parts of the body, the disease is called metastatic breast cancer.

Although scientists have identified many risk factors that increase a woman’s chance of developing breast cancer, they do not yet know what causes normal cells to become cancerous. Experts tend to agree that breast cancer is caused by a combination of genetic, hormonal, and environmental factors.

Most women who develop breast cancer have no family history of the disease, suggesting an environmental link. NIEHS scientists and other experts believe prevention strategies are the best way to try to stop breast cancer before it starts.

What is NIEHS Doing?

NIEHS plays a leadership role in funding and conducting studies on the ways in which environmental exposures increase breast cancer risk. This research seeks to understand the role of environmental agents, such as toxic chemicals, in the initiation and progression of cancer, as well as genetic susceptibility. Identifying and reducing contact with environmental factors linked to breast cancer presents tremendous opportunity to prevent this disease.

Sister Study– The NIEHS Sister Study has recruited more than 50,000 sisters of women with breast cancer from the U.S. and Puerto Rico. This landmark observational study is looking at lifestyle and environmental exposures, as well as genetic and biological factors that may increase breast cancer risk. Important findings from this study follow.

biological age and environmental exposures graphic
  • Biologic age, a DNA-based estimate of a person’s age, is associated with future development of breast cancer. For every five years a woman’s biologic age was older than her chronologic or actual age, known as age acceleration, she had a 15% increase in her chance of developing breast cancer.3
  • Women who lived in areas with higher levels of lead, mercury, and cadmium in air pollution had a greater chance of developing postmenopausal breast cancer.4
  • Postmenopausal women who had higher levels of vitamin D in their blood or who reported taking vitamin D supplements at least four times a week had lower rates of breast cancer.5
  • Burning wood or natural gas indoors, at least once a week, was associated with a modestly higher risk of breast cancer.6
  • Women who developed diabetes during two or more pregnancies had a higher incidence of breast cancer.7
  • Women who exercised or played sports more than seven hours a week during ages 5-19 had lower risk of breast cancer as adults.8
  • An association was found between having trouble sleeping four or more nights per week and increased breast cancer risk.9

Two Sister Study – An offshoot of the Sister Study, this study focuses on breast cancer in women younger than 50, who may have different breast cancer risk factors than older women. Approximately 1,300 women with young-onset breast cancer are participating, along with their sisters from the Sister Study and their biological parents. Some results from the study include the following.

  • Women who took estrogen-only hormone therapy had a 42% decrease in their risk of young-onset breast cancer, compared to their sisters who never had hormone therapy.10
  • Three novel single nucleotide polymorphisms, or genetic variation, were associated with the disease in younger women.11

Breast Cancer and the Environment Program (BCERP) – Jointly funded by NIEHS and the National Cancer Institute, grant-funded researchers and community organizations work together through BCERP to discover environmental factors that may contribute to breast cancer. They also share lessons learned with the broader community. Some hallmark findings from BCERP follow.

Roughly 1 in 8 U.S. women will develop invasive breast cancer sometime during her life. (American Cancer Society, 2019)
Roughly 1 in 8 U.S. women will develop invasive breast cancer sometime during her life. (American Cancer Society, 2019)
  • The chance of developing breast cancer is increased with exposure to endocrine disrupting chemicals during these periods in a woman's life: her prenatal development, puberty, pregnancy, and menopausal transition.12
  • Exposures to common contaminants in the environment may change the timing of puberty. For example, girls exposed to high levels of triclosan, a chemical used in antimicrobial soaps and hand sanitizers, experienced early breast development. Also, girls exposed to high levels of benzophenone-3, found in some sunscreens, experienced later breast development.13
  • Proteins produced by developing mammary tissue may change after exposure to pollutants in the environment, including bisphenol A, a chemical found in many plastic products. These exposures may alter cells in ways that contribute to breast cancer.

National Toxicology Program (NTP) – Headquartered at NIEHS, NTP is an interagency program known for expertise in conducting studies into the environmental origins of disease, including breast cancer. For example, researchers in the Reproductive Endocrinology Group are establishing new methods to study mammary glands. Sharing these methods with other labs will help scientists accurately identify environmental factors that may lead to problems in mammary gland development or function.

The Interagency Breast Cancer and Environmental Research Coordinating Committee (IBCERCC)Supported by NIEHS and the National Cancer Institute, IBCERCC was authorized by the Breast Cancer and Environmental Research Act of 2008 (Public Law 110-354) to examine the state of research on breast cancer and the environment. The committee included federal and non-federal representatives. IBCERCC issued a comprehensive report in 2013 that stated prevention is the key to reducing the emotional, physical, and financial burden of breast cancer. It also recommended intensifying the study of chemical and physical risk factors, transforming research to include collaborations across scientific disciplines and with community organizations, and communicating the science to the public.

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

Fact Sheets

Breast Cancer Risk and Environmental Factors

Additional Resources

Related Health Topics


  1. American Cancer Society. 2018. Breast Cancer [accessed December 3, 2018]. [Available American Cancer Society. 2018. Breast Cancer [accessed December 3, 2018].]
  2. Centers for Disease Control and Prevention - Breast Cancer Basic Information [Available Centers for Disease Control and Prevention - Breast Cancer Basic Information]
  3. Kresovich JK, Xu Z, O’Brien KM, Weinberg CR, Sandler DP, Taylor JA. 2019. Methylation-based biological age and breast cancer risk. J Natl Cancer Inst; doi:10.1093/jnci/djz020 [Online 22 February 2019]. [Abstract Kresovich JK, Xu Z, O’Brien KM, Weinberg CR, Sandler DP, Taylor JA. 2019. Methylation-based biological age and breast cancer risk. J Natl Cancer Inst; doi:10.1093/jnci/djz020 [Online 22 February 2019].]
  4. White AJ, O'Brien KM, Niehoff NM, Carroll R, Sandler DP 2018. Metallic Air Pollutants and Breast Cancer Risk in a Nationwide Cohort Study. Epidemiology; doi:10.1097/EDE.0000000000000917 [Online December 2018]. [Abstract White AJ, O'Brien KM, Niehoff NM, Carroll R, Sandler DP 2018. Metallic Air Pollutants and Breast Cancer Risk in a Nationwide Cohort Study. Epidemiology; doi:10.1097/EDE.0000000000000917 [Online December 2018].]
  5. O’Brien KM, Sandler DP, Taylor JA, Weinberg CR. 2017. Serum Vitamin D and Risk of Breast Cancer within Five Years. Environ Health Perspect 125(7):077004. [Abstract O’Brien KM, Sandler DP, Taylor JA, Weinberg CR. 2017. Serum Vitamin D and Risk of Breast Cancer within Five Years. Environ Health Perspect 125(7):077004.]
  6. White AJ, Sandler DP. 2017. Indoor Wood-Burning Stove and Fireplace Use and Breast Cancer in a Prospective Cohort Study. Environ Health Perspect 125(7):077011. [Abstract White AJ, Sandler DP. 2017. Indoor Wood-Burning Stove and Fireplace Use and Breast Cancer in a Prospective Cohort Study. Environ Health Perspect 125(7):077011.]
  7. Park YM, O’Brien KM, Zhaos S, Weinberg CR, Baird DD, Sandler DP. 2017. Gestational diabetes mellitus may be associated with increased risk of breast cancer. Br J Cancer 116(7):960-963. [Abstract Park YM, O’Brien KM, Zhaos S, Weinberg CR, Baird DD, Sandler DP. 2017. Gestational diabetes mellitus may be associated with increased risk of breast cancer. Br J Cancer 116(7):960-963.]
  8. Neihoff NM, White AJ, Sandler DP. 2017. Childhood and teenage physical activity and breast cancer risk. Breast Cancer Res Treat 164(3):697-705. [Abstract Neihoff NM, White AJ, Sandler DP. 2017. Childhood and teenage physical activity and breast cancer risk. Breast Cancer Res Treat 164(3):697-705.]
  9. White AJ, Weinberg CR, Park YM, D’Aloisio AA, Vogtmann E, Nichols HB, Sandler DP. 2017. Sleep characteristics, light at night and breast cancer risk in a prospective cohort. Int J Cancer 141(11):2204-2214. [Abstract White AJ, Weinberg CR, Park YM, D’Aloisio AA, Vogtmann E, Nichols HB, Sandler DP. 2017. Sleep characteristics, light at night and breast cancer risk in a prospective cohort. Int J Cancer 141(11):2204-2214.]
  10. O’Brien KM, Fei C, Sandler DP, Nichols HB, DeRoo LA, Weinberg CR. 2015. Hormone therapy and young-onset breast cancer. Am J Epidemiol 181(10):799-807. [Abstract O’Brien KM, Fei C, Sandler DP, Nichols HB, DeRoo LA, Weinberg CR. 2015. Hormone therapy and young-onset breast cancer. Am J Epidemiol 181(10):799-807.]
  11. O’Brien KM, Shi M, Sandler DP, Taylor JA, Zavkin DV, Keller J, Wise AS, Weinberg CR. 2016. A family-based, genome-wide association study of young-onset breast cancer: inherited variants and maternally mediated effects. Eur J Hum Genet 24(9):1316-1323. [Abstract O’Brien KM, Shi M, Sandler DP, Taylor JA, Zavkin DV, Keller J, Wise AS, Weinberg CR. 2016. A family-based, genome-wide association study of young-onset breast cancer: inherited variants and maternally mediated effects. Eur J Hum Genet 24(9):1316-1323.]
  12. Terry MB, et al. 2019. Environmental exposures during windows of susceptibility for breast cancer: a framework for prevention research. Breast Cancer Research; doi: 10.1186/s13058-019-1168-2 [Online 20 August 2019]. [Abstract Terry MB, et al. 2019. Environmental exposures during windows of susceptibility for breast cancer: a framework for prevention research. Breast Cancer Research; doi: 10.1186/s13058-019-1168-2 [Online 20 August 2019].]
  13. Wolff MS, Teitelbaum SL, McGovern K, Pinney SM, Windham GC, Galvez M, Pajak A, Rybak M, Calafat AM, Kushi LH, Biro FM, Breast Cancer and Environment Research Program. 2016. Environmental phenols and pubertal development in girls. Environ Int 84:174-180. [Abstract Wolff MS, Teitelbaum SL, McGovern K, Pinney SM, Windham GC, Galvez M, Pajak A, Rybak M, Calafat AM, Kushi LH, Biro FM, Breast Cancer and Environment Research Program. 2016. Environmental phenols and pubertal development in girls. Environ Int 84:174-180.]
  14. Williams KE, Lemieux GA, Hassis ME, Olshen AB, Fisher SJ, Werb Z. 2016. Quantitative proteomic analyses of mammary organoids reveals distinct signatures after exposure to environmental chemicals. Proc Natl Acad Sci USA 113(10):E1343-E1351. [Abstract Williams KE, Lemieux GA, Hassis ME, Olshen AB, Fisher SJ, Werb Z. 2016. Quantitative proteomic analyses of mammary organoids reveals distinct signatures after exposure to environmental chemicals. Proc Natl Acad Sci USA 113(10):E1343-E1351.]

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