Women's Health and the Environment

Introduction

Health is influenced throughout the lifespan by many factors, including sex, gender, racial ethnicity, culture, socioeconomic status, and the environment. Women's health is an essential part of the NIEHS research agenda. Researchers investigate environmental, lifestyle, and behavioral factors to prevent or reduce the chance of women developing health problems.

Certain health conditions and diseases are specific to women, two of which are endometriosis and uterine fibroids.

What is NIEHS Doing?

NIEHS-supported research seeks to understand the how endometriosis and uterine fibroids develop and how the conditions may be affected by the environment.

Endometriosis research efforts include the following:

• In the Pregnancy & Female Reproduction Group, uncovering a link between the transcription factor Gata2 and a hormone receptor that may aid in the development of endometriosis treatment.¹
• Examining the role of inflammation and environmental exposures in the development of endometriosis with the goal of detecting disease and identifying preventative measures to reduce the risk of endometriosis.
• Finding a potential connection between dioxins and endometriosis. Scientists at NIEHS found evidence for single exposures to a dioxin during pregnancy can disrupt the offspring’s adult uterine response to hormones.²
• Discovering exposure to low levels of bisphenol A (BPA) during fetal development permanently altered the uterine genome in mice. Some of the changes emerged only after sexual maturity and were not present in birth or early life. The genes affected are implicated in endometriosis, as well as infertility, osteoporosis, obesity, and some cancers.³
• Using cell-based models to better understand how endocrine disrupting chemicals may impact endometriosis.
• Studying effects of environmental chemicals on the reproductive tract, including the uterus.

The Women’s Risk of Endometriosis (WREN) study found:

• Persistent environmental chemicals, such as some pesticides, may affect endometriosis risk.⁴
• Higher levels of bisphenol A (BPA) in urine are associated with increased risk of endometriosis in women’s pelvic areas.⁵
• Women fed soy formula as infants had more than twice the level of endometriosis when they reached adulthood than women who did not.⁶

Study of Environment, Lifestyle & Fibroids (SELF) – More than 80% of African American women are likely to develop fibroids. Of these women, as a result, 1 in 5 will have a hysterectomy, as compared to 1 in 15 white women. To learn why there is a difference, SELF enrolled more than 1,600 African American women, ages 23 to 34, without a prior clinical diagnosis of fibroids. SELF uses ultrasound screening to detect new fibroids and follow fibroid growth over a five-year period. Researchers are looking at vitamin D deficiency, reproductive tract infections, ancestry, and other possible risk factors for fibroid development.

In one project, the SELF study found that fibroid growth varied by initial size. Small fibroids, less than 2 centimeters in diameter, can have rapid growth but also a high chance of shrinking or disappearing. Larger fibroids grow more slowly. For example, a 2-centimeter fibroid is likely to take 4-5 years to double in diameter. SELF is the first study to measure fibroid growth in a large, high-risk group of African American women, 23-35 years old. This fibroid-growth information may be useful for developing treatment strategies.

Fibroid Growth Study – Understanding how fibroids grow is important because large fibroids are more likely to cause health problems than smaller ones. NIEHS researchers examined differences between fibroids that are likely to grow versus those that do not. They studied 116 women for up to one year, some of whom underwent myomectomies (fibroid-removal surgery). They found:

• Fibroid growth rates were similar in black and white women younger than age 35.⁷ However, the growth rates were higher in older black than in older white women, with different patterns of gene expression in the tumors.⁸
• Short growth spurts are common for fibroids, suggesting that tumor biology may change rapidly.⁹
• Among women who already have large fibroids (greater than 2 inches in diameter), the severity of symptoms—rather than the size of the fibroids or other factors—lead women to opt for treatment. Aggressive management of pain and bleeding may be effective in reducing the need for surgical intervention.¹⁰

Postpartum Uterine Regression Study – To investigate pregnancy-related changes in fibroids, NIEHS Women’s Health Group researchers collaborated with a University of North Carolina at Chapel Hill study using ultrasound examinations. Women whose ultrasounds showed they had fibroids in early pregnancy had another ultrasound a few months after the end of their pregnancy. Among 171 women with one initial fibroid, 36% had no identifiable fibroid in the follow-up ultrasound; fibroids that did not disappear tended to decrease in size.¹¹ Understanding the reasons behind these changes may lead to new research or strategies for non-surgical fibroid treatment.

Uterine Fibroid Study – This study involved women ages 35-49 who were randomly selected from the membership rolls of a large health care system. Researchers found:

• Adequate vitamin D in premenopausal women is associated with a reduced risk of uterine fibroids in both black and white women.¹²
• An increased fibroid risk in the daughters of women who took prenatal diethylstilbestrol (DES) to prevent pregnancy complications.¹³
• Black women were disproportionately having surgery for fibroids, although race did not influence size, location, or number of fibroids between black and white women once at surgery.¹⁴

Role of Growth Factors in Uterine Leiomyoma Growth – A growth factor is a substance, such as a protein, that may stimulate development of tissue. The Molecular Pathogenesis Group within the National Toxicology Program’s laboratory is looking at growth factors in uterine fibroid development. Growth factors are made by our bodies, but environmental chemicals, such as cadmium, may affect production. This research approach is a new way to determine how fibroids develop and how they may be treated.

Breast Cancer Research

The NIEHS Sister Study examines environmental and familial factors that may affect breast cancer and other diseases. More than 50,000 women across the U.S. and Puerto Rico, between ages 35–74 whose sister had breast cancer, joined this landmark research effort. Because of their shared environment, genes, and experiences, studying sisters provides a greater chance of identifying risk factors and ways to prevent breast cancer. Many research articles from this ongoing study are published.

The Breast Cancer and the Environment Research Program, co-funded by NIEHS and the National Cancer Institute, studies environmental and genetic factors over women's lifespans that may alter the chance of developing breast cancer. The studies seek to understand if environmental exposures during specific periods, such as puberty or pregnancy, may increase breast cancer risk.

Other Research

Research related to cookstoves concerns community-based interventions primarily in Guatemala, Ecuador, Nepal, Pakistan, Ghana, and U.S. Fueled by wood, coal, or dung, traditional cookstoves or open fires produce smoke that contributes to 4.3 million estimated annual deaths, with women and young children affected the most. Cookstove smoke contributes to chronic illnesses and other health effects, especially related to the heart and lungs.

Reproductive System Disorders research concerns how exposure to environmental pollutants can lead to diseases, disorders, and conditions that affect functioning in female and male reproductive systems.

Traffic-related air pollution (TRAP) and pregnancy disorders were reviewed by the National Toxicology Program, housed at NIEHS. Air pollution is an established risk factor for hypertension and cardiovascular disease in adults, and increasing evidence show air pollution may increase hypertensive disorders of pregnancy. NTP concluded that exposure to TRAP is presumed to be a hazard to pregnant women for developing hypertensive disorders of pregnancy (e.g., gestational hypertension, preeclampsia, eclampsia).

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

• Hormone Receptor Implicated in Ovarian Cancer (November 2020)
• Blood Test May Point to Timing of Breast Cancer Diagnosis (February 2020)
• Permanent Hair Dye and Straighteners May Increase Breast Cancer Risk (January 2020)
• Pregnancy Hypertension Risk Increased by Traffic-related Air Pollution (January 2020)
• NIH Researchers Tackle Questions on Air Pollution and Pregnancy (September 2019)
• Arsenic May Interfere With Pregnancy and Children’s Health (July 2019)
• Women’s Health Conference Draws Record Crowd (May 2019)
• Severe Menstrual Pain Linked to Soy Formula Feeding During Infancy (December 2018)
• How Environmental Exposures Impact Women’s Health (May 2018)
• Fibroid Link to Miscarriage Now in Doubt (August 2017)

Fact Sheets

4 pages

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Breast Cancer Risk and Environmental Factors

2 pages

(1MB)

Cosmetics and Hair Dye

2 pages

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Reproductive Health in Females and Males

Press Releases

• Permanent Hair Dye and Straighteners May Increase Breast Cancer Risk (December 2019)
• Pregnancy Hypertension Risk Increased by Traffic-related Air Pollution (December 2019)
• NIH Partners With Apple and Harvard University on Women’s Health Study (September 2019)
• Soy Formula Feeding During Infancy Associated With Severe Menstrual Pain in Adulthood (November 2018)
• NIH Launches Large Study of Pregnant Women in Areas Affected by Zika Virus (June 2016)

Additional Resources

• Information on endometriosis and uterine fibroids from the Office on Women’s Health at Womenshealth.gov.
• The LactMed® database contains information on drugs and other chemicals to which breastfeeding mothers may be exposed.
• Uterine fibroids information from the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Related Health Topics

• Bisphenol A (BPA)
• Breast Cancer
• Endocrine Disruptors
• Reproductive Health