Endocrine Disruptors

Introduction

Many chemicals, both natural and man-made, may mimic or interfere with the body’s hormones, known as the endocrine system. Called endocrine disruptors, these chemicals are linked with developmental, reproductive, brain, immune, and other problems.

Endocrine disruptors are found in many everyday products, including some plastic bottles and containers, liners of metal food cans, detergents, flame retardants, food, toys, cosmetics, and pesticides.

Some endocrine-disrupting chemicals are slow to break-down in the environment. That characteristic makes them potentially hazardous over time.

Endocrine disrupting chemicals cause adverse effects in animals. But limited scientific information exists on potential health problems in humans. Because people are typically exposed to multiple endocrine disruptors at the same time, assessing public health effects is difficult.

What are some common endocrine disruptors?

• Bisphenol A (BPA) — used to make polycarbonate plastics and epoxy resins, which are found in many plastic products including food storage containers
• Dioxins — produced as a byproduct in herbicide production and paper bleaching, they are also released into the environment during waste burning and wildfires
• Perchlorate — a by-product of aerospace, weapon, and pharmaceutical industries found in drinking water and fireworks
• Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) — used widely in industrial applications, such as firefighting foams and non-stick pan, paper, and textile coatings
• Phthalates — used to make plastics more flexible, they are also found in some food packaging, cosmetics, children’s toys, and medical devices
• Phytoestrogens — naturally occurring substances in plants that have hormone-like activity, such as genistein and daidzein that are in soy products, like tofu or soy milk
• Polybrominated diphenyl ethers (PBDE) — used to make flame retardants for household products such as furniture foam and carpets
• Polychlorinated biphenyls (PCB) — used to make electrical equipment like transformers, and in hydraulic fluids, heat transfer fluids, lubricants, and plasticizers
• Triclosan — may be found in some anti-microbial and personal care products, like liquid body wash

How do people encounter endocrine-disrupting chemicals?

People may be exposed to endocrine disruptors through food and beverages consumed, pesticides applied, and cosmetics used. In essence, your contact with these chemicals may occur through diet, air, skin, and water.

Even low doses of endocrine-disrupting chemicals may be unsafe. The body’s normal endocrine functioning involves very small changes in hormone levels, yet we know even these small changes can cause significant developmental and biological effects. This observation leads scientists to think that endocrine-disrupting chemical exposures, even at low amounts, can alter the body’s sensitive systems and lead to health problems.

When absorbed in the body, an endocrine disruptor can decrease or increase normal hormone levels (left), mimic the body's natural hormones (middle), or alter the natural production of hormones (right).

Fact Sheets

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Endocrine Disruptors and Your Health

What is NIEHS Doing?

For more than three decades, NIEHS has been a pioneer in conducting research on the health effects of endocrine disruptors. NIEHS-supported research leads to a greater understanding of how endocrine-disrupting chemicals may harm our health and cause disease.

This work began with studies on the endocrine-disrupting effects of the drug diethylstilbestrol (DES). From 1940s through 1970s, DES was used to treat women with high-risk pregnancies, with the mistaken belief that it prevented miscarriage. In 1972, prenatal exposure to DES was linked to the development of a rare form of vaginal cancer in daughters whose mothers took DES, and with numerous noncancerous changes in both sons and daughters. NIEHS experiments on DES successfully replicated and predicted health problems, which was useful in discovering how DES may harm wellbeing.

NIEHS was involved in developing a consensus statement in 2019 on the key characteristics of endocrine-disrupting chemicals, which provides a framework to help scientists evaluate potential endocrine disruptors.

NIEHS leads cutting-edge research projects on endocrine disrupting chemicals to understand how they work and define their role in health and disease. Research areas in progress include:

• Developing new models and tools to better understand how endocrine disrupters work
• Developing and applying high throughout assays to identify substances with endocrine disrupting activity
• Conducting animal and human health research to define linkages between exposure to endocrine disrupters and health effects
• Developing new assessments and biomarkers of exposure and toxicity
• Identifying and developing new intervention and prevention strategies

Related work of the National Toxicology Program

In 2000, an independent panel of experts convened by NIEHS and the National Toxicology Program (NTP), which is housed at NIEHS, concluded there was credible evidence that very low doses of some hormone-like chemicals can adversely affect bodily functions in test animals.

NTP is evaluating endocrine disrupters including pesticides, perfluorinated chemicals, compounds that may replace BPA in the marketplace, and components of flame-retardants for how they may affect body tissues such as breast, uterus, fat cells, male reproductive tract, and liver. In addition, they conduct laboratory studies that help them prioritize endocrine disrupting chemicals for further toxicity testing.

NTP scientists collaborate with researchers from the U.S. Environmental Protection Agency (EPA) to develop and validate integrated, high throughput testing strategies to detect substances that could disrupt endocrine functions by interacting with the hormones estrogen and androgen. In addition, they created a comprehensive database from thousands of scientific studies on how different substances interact with hormones.

The multi-agency Tox 21 program, in which NIEHS participates, is developing and applying new models and tools using robotics to predict endocrine disrupting activity for environmental substances.

What has NIEHS discovered?

NIEHS-supported research has discovered links between endocrine-disrupting chemicals and the ways in which wellbeing may be harmed, as shown by the following examples:

• Attention. Attention-deficit/hyperactivity disorder (ADHD) is one of the most common childhood disorders, which can continue through adolescence and into adulthood. ADHD symptoms include difficulty staying focused, paying attention, and controlling behavior. Researchers reported in JAMA that ordinary exposure to certain phthalates, as found in urine samples, was associated with ADHD-related behaviors in adolescence. The drug DES may be linked to an increased chance of developing ADHD in the grandchildren of women who used it during pregnancy.
• Immunity. Children exposed to high levels of PFAS had a diminished immune response to vaccines.
• Metabolism. Long-term exposure to arsenic can disrupt metabolism, increasing the risk of diabetes and other metabolic disorders.
• Puberty. Chemicals in lavender oil and tea tree oil are potential endocrine disruptors. Researchers found that persistent exposure to lavender oil products is associated with premature breast development in girls, and abnormal breast development in boys.
• Reproduction. DES can cause epigenetic changes, altering the way genes are turned on and off, in reproductive organs of mice. The findings provide a possible explanation for how endocrine disruptors affect fertility and reproduction.

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

• The Environment Influences Brain Development, Experts Say (March 2020)
• Endocrine Disruptor Identification Begins with Biology (December 2019)
• Endocrine Disruptors and Male Vulnerability to Behavioral Disorders (November 2019)
• Lavender oil linked to early breast growth in girls (September 2019)
• NC researchers circle on chemicals that disrupt hormones (May 2019)
• Earlier puberty linked with personal care products (January 2019)
• New North Carolina endocrine disruptor group meets at NIEHS (April 2018)

Podcasts

• All About Phthalates, a podcast by NIEHS
• EDCs and Health, a video with NIEHS special volunteer Linda Birnbaum, Ph.D.
• Endocrine Disrupting Chemicals, a video by the Endocrine Society and the Hormone Health Network
• Obesity and the Environment, a podcast by NIEHS

Additional Resources

• Endocrine Disrupting Chemicals, a resource page by the World Health Organization contains educational material and documents for decision makers
• What is Endocrine Disruption?, an informational website for consumers created by the U.S. Environmental Protection Agency

Related Health Topics

• Bisphenol A (BPA)
• Cosmetics and Your Health
• Reproductive Health and the Environment
• Women's Health