Endocrine Disruptors

Overview

Endocrine-disrupting chemicals are chemicals that mimic, block, or interfere with the body’s hormones. These chemicals are associated with a wide array of health issues in both wildlife and people. People are exposed to endocrine disruptors such as plasticizers and pesticides through food and beverages, drinking water, air pollution, building materials, furniture, and personal care products.

The endocrine system is one of the body’s main communication networks. Every organ is in some way a part of the endocrine system, which makes the entire body vulnerable to endocrine-disrupting chemicals. For example, hormones produced by the ovaries, testes, brain, and adrenal glands travel through the bloodstream to impact numerous target organs including uterus, mammary gland, muscle, bone, heart, kidney, and lungs. Hormones primarily act by binding to hormone receptors, like a key in a lock, in target organs.

Endocrine glands throughout the body produce hormones that control many biological processes, including normal growth, fertility, and reproduction. Minor disruptions in hormone levels may cause significant developmental and biological effects. Even low doses of endocrine-disrupting chemicals may be unsafe.

The following are among the most common endocrine-disrupting chemicals:

• Atrazine is one of the most applied herbicides in the world, often used to control weeds in corn, sorghum, and sugarcane crops.
• Bisphenol A (BPA) is used to make polycarbonate plastics and epoxy resins. It is used in manufacturing, food packaging, toys, and other applications. BPA resins may be found in the lining of some canned foods and beverages
• Dioxins are a byproduct of certain manufacturing processes, such as herbicide production and paper bleaching. They can be released into the air from waste burning and wildfires.
• Organophosphates and organochlorines are compounds used in many insecticides, herbicides, and nerve gases.
• Perchlorate is a colorless salt manufactured and used as an industrial chemical to make rocket fuel, explosives, and fireworks, but also as an anti-static in food packaging such as cereal bags. It is also a common groundwater contaminant.
• Per- and polyfluoroalkyl substances (PFAS) are a large group of chemicals used widely in industrial applications, such as firefighting foam, nonstick pans, paper, personal care products, cosmetics, and textile coatings.
• Phthalates are a large group of compounds used as liquid plasticizers. They are found in hundreds of products, including some food packaging, cosmetics, fragrances, children’s toys, and medical device tubing. Cosmetics that may contain phthalates include nail polish, hair spray, aftershave lotion, cleanser, and shampoo.
• Phytoestrogens are naturally occurring hormonally active substances found in some plants, particularly legumes. They act similarly to estrogen produced by the body. Soy foods and infant formulas, for example, contain phytoestrogens.
• Polybrominated diphenyl ethers (PBDE) are used as flame retardants for products such as furniture foam and carpet. Many are in the process of being phased out but remain environmentally pervasive.
• Polychlorinated biphenyls (PCBs) were used to make electrical equipment, such as transformers, and are found in hydraulic fluids, heat transfer fluids, lubricants, and plasticizers. PCBs were mass-produced globally until they were banned in 1979 but remain environmentally pervasive
• Tributyltin and tin compounds are chemicals used in fungicides to combat mold.
• Triclosan is an ingredient that was previously added to some antimicrobial and personal care products, like liquid body wash and soaps.
• Dichlorodiphenyltrichloroethane (DDT) is a pesticide banned in most countries in 1972 that is still found in the environment today.

Endocrine-disrupting chemicals are found in many everyday products. Some cosmetics, food and beverage packaging, medical equipment, toys, carpet, furniture, cookware, and pesticides contain endocrine-disrupting chemicals. Exposure to these chemicals may increase risk for cancer, male and female reproductive system problems, obesity, diabetes, learning and memory problems, and various other diseases and dysfunctions. Exposure during development is most concerning because hormones affect how the body forms and functions, so disruption can lead to permanent changes. Endocrine-disrupting chemicals cannot be completely avoided, but you can take steps to reduce your exposure.

Related Health Effects

Researchers have learned how these chemicals influence the endocrine system and change hormonal functions. These are called “Key Characteristics” and help researchers identify chemicals with endocrine-disrupting properties. For example, researchers have discovered that endocrine disruptors can:

• Mimic, or partly mimic, naturally occurring hormones in the body like estrogens (female sex hormones), androgens (male sex hormones), and thyroid hormones. Examples of hormone mimics are phytoestrogens (estrogen).
• Bind to hormone receptors within a cell and block the naturally occurring hormone from performing its normal function. Examples of chemicals that block hormones are anti-estrogens and anti-androgens such as DDT.
• Interfere with or block the way natural hormones, or their receptors, are made or handled in the body. This could alter hormone metabolism in the liver or where and when hormone receptors are expressed during development. Examples include BPA, which alters estrogen receptor levels, and atrazine, which alters testosterone production.

Both the Endocrine Society and the European Society of Endocrinology have highlighted “widespread scientific evidence” that exposure to endocrine-disrupting chemicals is harmful to human, animal, and ecological health. Understanding the health effects of endocrine-disrupting chemicals is important for preventing disease because:

• People are typically exposed to multiple endocrine disruptors at the same time.
• Early-life exposures to these chemicals may result in health effects much later in life.
• In some cases, these effects can be passed down for multiple generations.

Cancer

NIH researchers found that women who regularly used hair dye were more likely to develop breast cancer than women who did not, especially among Black women.

During puberty, frequent use of personal care products that contain endocrine disruptors is linked with an increased chance of developing breast cancer later in life.

Immunity

Children exposed to high levels of PFAS had a diminished immune response to vaccines. Other research found some indication of increased risks of childhood infections, particularly following exposures to PFAS.

Liver Disease

A large-scale study on exposure to PFAS in humans and rodents showed consistent evidence of chemical-driven liver damage. Other research indicated that exposure to triclosan worsened fatty liver disease in mice that ate a high-fat diet.

Metabolism and Diabetes

Long-term exposure to arsenic can disrupt metabolism, increasing the risk of diabetes and other metabolic disorders. Endocrine-disrupting chemicals that promote adiposity, or the accumulation of body fat, are termed “obesogens.” Examples of obesogens include many pesticides and other agrochemicals, plasticizers, and bisphenols.

Neurodevelopment

Exposure to a mixture of suspected endocrine-disrupting chemicals early in pregnancy was shown to reduce IQ in children. Neurodevelopmental disorders — such as attention deficit hyperactivity disorder (ADHD), problems with fine motor coordination, and lower cognition — were found to be more common in children exposed to high levels of flame retardants and PBDEs. Exposure to certain phthalates has been associated with behaviors characteristic of ADHD. Other endocrine-disrupting chemicals shown to alter brain organization and behavior include BPA, PCBs, many pesticides including atrazine, certain flame retardants, and perchlorate.

Preterm Birth

Researchers analyzing a large, diverse data sample of births in the United States found that exposure to certain phthalates was linked with shorter-length pregnancies and increased risk of preterm birth.

Puberty

Chemicals in lavender oil and tea tree oil were associated with premature breast development in girls and abnormal breast development in boys. Girls in the United States appear to be getting their first menstrual periods earlier — about six months sooner on average than decades ago. Early onset puberty is a concern because of links to diabetes, heart issues, breast and endometrial cancers, fertility issues, and mental health, according to the Endocrine Society. It is thought that a combination of greater obesity and exposure to estrogen-mimicking endocrine-disrupting chemicals may be contributing to early female puberty.

Fertility

NIH research shows that exposure to persistent organic pollutants and endocrine-disrupting chemicals in the environment can affect male and female fertility. A study found that the EDC methyl paraben affects fertility in women, while phthalates and the UV filter benzophenone-2 affect fertility in men. PFAS substances have been linked to lower testosterone levels and reduced semen quality in males and decreased fertility in women. Atrazine also lowers testosterone, reduces fertility, and compromises sperm quality, and developmental exposure can result in reproductive abnormalities.

Women’s Health

Higher levels of BPA in urine were associated with an increased risk of pelvic endometriosis. Women fed soy formula as infants had more than twice the level of endometriosis when they reached adulthood than women who did not. Exposure to high levels of flame retardants and plasticizers may have a negative impact on the outcomes of in vitro fertilization (IVF). PFAS chemicals have been linked with increased risks of prostate and endometrial cancer.

Causes and Risk Factors

People may be exposed to endocrine disruptors through food and beverages consumed, pesticides applied, and cosmetics used. They are found in many everyday products, including some plastic bottles and containers, food-can liners, detergents, toys, cosmetics, and pesticides. Contact with these chemicals may occur through diet, air, skin, and water.

Exposure During Sensitive Life Stages

Endocrine-disrupting chemicals can act on the body throughout life, but the period of fetal and child development may be an especially sensitive time. During this developmental window, endocrine-disrupting chemicals may interfere with processes that determine how tissues are programmed. This may increase susceptibility to adverse health outcomes later in life. Adolescence is likely another, but less well researched, window of sensitivity.

Children face risks from EDC exposure for several reasons:

• Hormones at very low levels, released at precise times, shape how cells and organs develop and function, including the brain and reproductive system. Disruption can result in permanent dysfunction.
• Across development through puberty, hormones organize and activate sex differences in physical and physiological systems, most notably the reproductive system.
• Endocrine-disrupting chemicals can cross the placenta.
• Before and after birth, during periods of rapid growth and development, normal biological processes may be disrupted by environmental chemicals.
• Children eat, drink, and breathe more than adults relative to their size.
• Children frequently put objects in their mouths and play on the floor and ground.
• Protective bodily systems, such as the blood brain barrier, the immune system, and systems that help filter pollutants from inhaled air or process chemicals out of the body, are not yet fully developed.

Prevention Guidance

Endocrine-disrupting chemicals cannot be completely avoided or removed, but you can make informed choices to reduce exposure and risk of any potential health effects. It is important to minimize exposures and be aware of new endocrine-disrupting chemicals as they emerge. It is also important to understand that while some endocrine-disrupting chemicals, such as most PFAS, can stay in the body a long time and thus accumulate, others, such as bisphenols and phthalates, break down and are rapidly excreted. So, lifestyle changes will affect body levels of some chemicals more than others.

• NIH researchers are developing tools, tests, and strategies that regulators may one day use to identify potential endocrine-disrupting chemicals.
• NIH researchers are working to understand how other endocrine functions such as lactation, bone development, and placental function may be vulnerable to endocrine-disrupting chemicals.

Families can make the personal choice to reduce exposures to endocrine-disrupting chemicals by taking these steps:

• When possible, opt for glass, porcelain, or stainless-steel containers, particularly for hot food or liquids.
• Do not microwave plastic food containers. Some, like polycarbonate, are strong and durable, but over time, all break down from overuse, particularly at high temperatures, and leach endocrine-disrupting chemicals.
• To the degree possible, avoid kitchen plastics including storage containers, utensils, cutting boards, bags, and food wrap to reduce exposure to endocrine-disrupting chemicals that leach from plastic.
• Check the recycling codes on the bottom of plastic containers. Some, but not all, plastics marked with recycle codes 3 or 7 may be made with BPA.
• Reduce your use of canned foods.
• Use baby bottles that are BPA free.
• Choose fragrance-free when possible.
• Use PFAS-free cookware.
• Look for labels on personal care products and cosmetics to help find products free of parabens, PFAS, phthalates, and other endocrine-disrupting chemicals.

Emerging research suggests that certain nutritional approaches may help reduce the harmful health effects of some environmental exposures:

• Choosing organic foods and avoiding canned foods, particularly acidic foods like tomatoes, reduces exposure to endocrine-disrupting pesticides and bisphenols.
• NIH researchers reported that when pregnant women improved their nutrition and reduced exposure to hazardous chemicals, they were more likely to have healthy babies. And their children were better able to cope with environmental stressors later in life.
• Certain nutrients like vitamin E and omega-3 fatty acids may reduce cell damage from PCB exposure. And a type of fiber found in vegetables can potentially protect against cardiovascular problems related to PCB exposure.
• Dietary fiber may help protect against metabolic and fatty liver diseases related to PFOS exposure.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on endocrine disruptors.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.  

For more than three decades, NIH has pioneered research examining the health effects of endocrine disruptors. This work began with studies on the endocrine-disrupting effects of diethylstilbestrol. From the 1940s through the 1970s, diethylstilbestrol was used to treat women with high-risk pregnancies, with the mistaken belief that it prevented miscarriage. In 1972, prenatal exposure to diethylstilbestrol was linked to the development of a rare form of vaginal cancer in daughters whose mothers took the drug. Numerous noncancerous changes in both sons and daughters also were observed.

NIH leads cutting-edge research projects to understand endocrine-disrupting chemicals and their role in health and disease. Research areas in progress include:

• Developing new models and tools to better understand how endocrine disruptors work
• Developing and applying high-throughput assays to identify substances with endocrine-disrupting activity
• Conducting animal and human health research to define linkages between exposure to endocrine disruptors and health effects
• Developing new assessments and biomarkers of exposure and toxicity
• Identifying and developing new intervention and prevention strategies
• Identifying diseases and dysfunctions not previously known to be linked with endocrine disruptors
• Understanding when during life exposure to endocrine-disrupting chemicals may cause health problems

NIH collaborations continue to shed light on the health effects of endocrine-disrupting chemicals. Examples include the following.

• Key characteristics framework: NIH was involved in developing a consensus statement in 2019 on the key characteristics of endocrine-disrupting chemicals. The framework helps scientists evaluate potential endocrine disruptors.
• Robotics and high-throughput testing: The multi-agency Tox21 program developed and applied new models and tools using robotics to predict endocrine-disrupting activity for environmental substances.
• BPA research. The Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA) program was developed to study the full range of potential health effects from exposure to BPA.
• Chemical mixtures research: In human health studies, real-world environmental exposures occur in mixtures that are too complex for traditional statistical models. NIH and National Toxicity Program (NTP) are developing methods to study environmental exposures in ways that more closely represent the mixture of exposures that people experience in real life.
• The NIH Sister Study is one of the nation’s largest studies on how environmental and genetic factors influence risk of breast cancer and other diseases. More than 50,000 women from across the United States participate. More than 300 scientific papers have been published from this study.
• LIFE Study: NIH’s Longitudinal Investigation of Fertility and the Environment (LIFE) Study is examining whether exposure to persistent organic pollutants affects the length of time it takes for couples to become pregnant, a measure of fecundity. It is the only study to measure chemicals in both partners and to follow couples trying to become pregnant for 1 year. So far, the study found that the EDC methyl paraben affects fertility in women, while phthalates and the UV filter benzophenone-2 affect fertility in men.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.