ENDOCRINE DISRUPTORS
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.
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.
What is the Endocrine System?
Endocrine systems, also referred to as hormone systems, are found in all mammals, birds, fish, and many other types of living organisms. They are made up of:
Why are Hormones Important?
Hormones act as chemical messengers that are released into the blood stream to act on an organ in another part of the body. Although hormones reach all parts of the body, only target cells with compatible receptors are equipped to respond. Over 50 hormones have been identified in humans and other vertebrates.
Hormones control or regulate many biological processes and are often produced in exceptionally low amounts within the body. Examples of such processes include:
Much like a lock and key, many hormones act by binding to receptors that are produced within cells. When a hormone binds to a receptor, the receptor carries out the hormone's instructions, either by altering the cell's existing proteins or turning on genes that will build a new protein. The hormone-receptor complex switches on or switches off specific biological processes in cells, tissues, and organs.
Some examples of hormones include:
Endocrine systems, also referred to as hormone systems, are found in all mammals, birds, fish, and many other types of living organisms. They are made up of:
- Glands located throughout the body;
- Hormones that are made by the glands and released into the bloodstream or the fluid surrounding cells; and
- Receptors in various organs and tissues that recognize and respond to the hormones.
Why are Hormones Important?
Hormones act as chemical messengers that are released into the blood stream to act on an organ in another part of the body. Although hormones reach all parts of the body, only target cells with compatible receptors are equipped to respond. Over 50 hormones have been identified in humans and other vertebrates.
Hormones control or regulate many biological processes and are often produced in exceptionally low amounts within the body. Examples of such processes include:
- blood sugar control (insulin);
- differentiation, growth, and function of reproductive organs (testosterone (T) and estradiol); and
- body growth and energy production (growth hormone and thyroid hormone).
Much like a lock and key, many hormones act by binding to receptors that are produced within cells. When a hormone binds to a receptor, the receptor carries out the hormone's instructions, either by altering the cell's existing proteins or turning on genes that will build a new protein. The hormone-receptor complex switches on or switches off specific biological processes in cells, tissues, and organs.
Some examples of hormones include:
- Estrogens are the group of hormones responsible for female sexual development. They are produced primarily by the ovaries and in small amounts by the adrenal glands.
- Androgens are responsible for male sex characteristics. Testosterone, the sex hormone produced by the testicles, is an androgen.
- The thyroid gland secretes two main hormones, thyroxine and triiodothyronine, into the bloodstream. These thyroid hormones stimulate all the cells in the body and control biological processes such as growth, reproduction, development, and metabolism.
Where are Endocrine Glands Located in the Human Body?
Hypothalamus - The hypothalamus links our endocrine and nervous systems together. The hypothalamus drives the endocrine system.
Pituitary gland - The pituitary gland receives signals from the hypothalamus. This gland has two lobes, the posterior and anterior lobes. The posterior lobe secretes hormones that are made by the hypothalamus. The anterior lobe produces its own hormones, several of which act on other endocrine glands. Thyroid gland - The thyroid gland is critical to the healthy development and maturation of vertebrates and regulates metabolism. Adrenal glands - The adrenal gland is made up of two glands: the cortex and medulla. These glands produce hormones in response to stress and regulate blood pressure, glucose metabolism, and the body's salt and water balance. |
Pancreas - The pancreas is responsible for producing glucagon and insulin. Both hormones help regulate the concentration of glucose (sugar) in the blood.
Gonads - The male reproductive gonads, or testes, and female reproductive gonads, or ovaries, produce steroids that affect growth and development and also regulate reproductive cycles and behaviors. The major categories of gonadal steroids are androgens, estrogens, and progestins, all of which are found in both males and females but at different levels.
How Can Chemicals Affect the Endocrine System?
Scientific research on human epidemiology, laboratory animals, and fish and wildlife suggests that environmental contaminants can disrupt the endocrine system leading to adverse-health consequences. It is important to gain a better understanding of what concentrations of chemicals found in the environment may cause an adverse effect. Various types of scientific studies (epidemiology, mammalian toxicology, and ecological toxicology) are necessary to resolve many of the scientific questions and uncertainty surrounding the endocrine disruptor issue. Many such studies are currently underway by government agencies, industry, and academia
What are Concerns Regarding Endocrine Disruptors?
In the last two decades there has been a growing awareness of the possible adverse effects in humans and wildlife from exposure to chemicals that can interfere with the endocrine system. These effects can include:
Clear evidence exists that some chemicals cause these effects in wildlife, but limited evidence exists for the potential of chemicals to cause these effects in humans at environmental exposure levels. Very few chemicals have been tested for their potential to interfere with the endocrine system. Current standard test methods do not provide adequate data to identify potential endocrine disruptors (EDs) or to assess their risks to humans and wildlife.
In recent years, some scientists have proposed that chemicals might inadvertently be disrupting the endocrine system of humans and wildlife. A variety of chemicals have been found to disrupt the endocrine systems of animals in laboratory studies, and there is strong evidence that chemical exposure has been associated with adverse developmental and reproductive effects on fish and wildlife in particular locations. The relationship of human diseases of the endocrine system and exposure to environmental contaminants, however, is poorly understood and scientifically controversial (Kavlock et al., 1996, EPA, 1997).
How Can Chemicals Disrupt the Endocrine System?
Disruption of the endocrine system can occur in various ways. Some chemicals mimic a natural hormone, fooling the body into over-responding to the stimulus (e.g., a growth hormone that results in increased muscle mass), or responding at inappropriate times (e.g., producing insulin when it is not needed). Other endocrine disruptors block the effects of a hormone from certain receptors (e.g. growth hormones required for normal development). Still others directly stimulate or inhibit the endocrine system and cause overproduction or underproduction of hormones (e.g. an over or underactive thyroid).
Certain drugs are used to intentionally cause some of these effects, such as birth control pills. In many situations involving environmental chemicals, however, an endocrine effect is not desirable.
What are Examples of Endocrine Disruption?
One example of the devastating consequences of the exposure of developing animals, including humans, to endocrine disruptors is the case of the potent drug diethylstilbestrol (DES), a synthetic estrogen. Prior to its ban in the early 1970's, doctors mistakenly prescribed DES to as many as five million pregnant women to block spontaneous abortion and promote fetal growth. It was discovered after the children went through puberty that DES affected the development of the reproductive system and caused vaginal cancer.
Since then, Congress has improved the evaluation and regulation process of drugs and other chemicals. The statutory requirement to establish an endocrine disruptor screening program is a highly significant step.
Growing scientific evidence shows that humans, domestic animals, and fish and wildlife species have exhibited adverse health consequences from exposure to environmental chemicals that interact with the endocrine system. To date, such problems have been detected in domestic or wildlife species with relatively high exposure to:
Several conflicting reports have been published concerning declines in the quality and quantity of sperm production in humans over the last 4 decades, and there are reported increases in certain cancers (e.g., breast, prostate, testicular). Such effects may have an endocrine-related basis, which has led to speculation about the possibility that these endocrine effects may have environmental causes. However, considerable scientific uncertainty remains regarding the actual causes of such effects.
Nevertheless, there is little doubt that small disturbances in endocrine function, particularly during certain highly sensitive stages of the life cycle (e.g., development, pregnancy, lactation) can lead to profound and lasting effects (Kavlock et al., 1996. EPA, 1997).
Gonads - The male reproductive gonads, or testes, and female reproductive gonads, or ovaries, produce steroids that affect growth and development and also regulate reproductive cycles and behaviors. The major categories of gonadal steroids are androgens, estrogens, and progestins, all of which are found in both males and females but at different levels.
How Can Chemicals Affect the Endocrine System?
Scientific research on human epidemiology, laboratory animals, and fish and wildlife suggests that environmental contaminants can disrupt the endocrine system leading to adverse-health consequences. It is important to gain a better understanding of what concentrations of chemicals found in the environment may cause an adverse effect. Various types of scientific studies (epidemiology, mammalian toxicology, and ecological toxicology) are necessary to resolve many of the scientific questions and uncertainty surrounding the endocrine disruptor issue. Many such studies are currently underway by government agencies, industry, and academia
What are Concerns Regarding Endocrine Disruptors?
In the last two decades there has been a growing awareness of the possible adverse effects in humans and wildlife from exposure to chemicals that can interfere with the endocrine system. These effects can include:
- developmental malformations,
- interference with reproduction,
- increased cancer risk; and
- disturbances in the immune and nervous system function.
Clear evidence exists that some chemicals cause these effects in wildlife, but limited evidence exists for the potential of chemicals to cause these effects in humans at environmental exposure levels. Very few chemicals have been tested for their potential to interfere with the endocrine system. Current standard test methods do not provide adequate data to identify potential endocrine disruptors (EDs) or to assess their risks to humans and wildlife.
In recent years, some scientists have proposed that chemicals might inadvertently be disrupting the endocrine system of humans and wildlife. A variety of chemicals have been found to disrupt the endocrine systems of animals in laboratory studies, and there is strong evidence that chemical exposure has been associated with adverse developmental and reproductive effects on fish and wildlife in particular locations. The relationship of human diseases of the endocrine system and exposure to environmental contaminants, however, is poorly understood and scientifically controversial (Kavlock et al., 1996, EPA, 1997).
How Can Chemicals Disrupt the Endocrine System?
Disruption of the endocrine system can occur in various ways. Some chemicals mimic a natural hormone, fooling the body into over-responding to the stimulus (e.g., a growth hormone that results in increased muscle mass), or responding at inappropriate times (e.g., producing insulin when it is not needed). Other endocrine disruptors block the effects of a hormone from certain receptors (e.g. growth hormones required for normal development). Still others directly stimulate or inhibit the endocrine system and cause overproduction or underproduction of hormones (e.g. an over or underactive thyroid).
Certain drugs are used to intentionally cause some of these effects, such as birth control pills. In many situations involving environmental chemicals, however, an endocrine effect is not desirable.
What are Examples of Endocrine Disruption?
One example of the devastating consequences of the exposure of developing animals, including humans, to endocrine disruptors is the case of the potent drug diethylstilbestrol (DES), a synthetic estrogen. Prior to its ban in the early 1970's, doctors mistakenly prescribed DES to as many as five million pregnant women to block spontaneous abortion and promote fetal growth. It was discovered after the children went through puberty that DES affected the development of the reproductive system and caused vaginal cancer.
Since then, Congress has improved the evaluation and regulation process of drugs and other chemicals. The statutory requirement to establish an endocrine disruptor screening program is a highly significant step.
Growing scientific evidence shows that humans, domestic animals, and fish and wildlife species have exhibited adverse health consequences from exposure to environmental chemicals that interact with the endocrine system. To date, such problems have been detected in domestic or wildlife species with relatively high exposure to:
- organochlorine compounds (e.g., 1,1,1- trichloro-2,2-bis(p-chlorophenyl);
- ethane (DDT) and its metabolite dichorodiphenyldichloroethylene (DDE);
- polychlorinated biphenyls (PCBs), and dioxins); and
- some naturally occurring plant estrogens.
Several conflicting reports have been published concerning declines in the quality and quantity of sperm production in humans over the last 4 decades, and there are reported increases in certain cancers (e.g., breast, prostate, testicular). Such effects may have an endocrine-related basis, which has led to speculation about the possibility that these endocrine effects may have environmental causes. However, considerable scientific uncertainty remains regarding the actual causes of such effects.
Nevertheless, there is little doubt that small disturbances in endocrine function, particularly during certain highly sensitive stages of the life cycle (e.g., development, pregnancy, lactation) can lead to profound and lasting effects (Kavlock et al., 1996. EPA, 1997).
https://www.epa.gov/endocrine-disruption/what-endocrine-disruption
https://www.niehs.nih.gov/health/topics/agents/endocrine/index.cfm