What are Endocrine Disrupting Chemicals (EDCs)?

The human body is an amazing organism that is delicately balanced.  Slight imbalances can cause long term and often life altering affects.  Endocrine Disrupting Chemicals (EDCs) disrupt hormone production and are pervasive in many everyday products like soaps, cosmetics, plastics, cleaning products and many more.  The following section explains what the endocrine system is, how it works and how EDCs wreck havoc on this finely tuned system.

Check out our Guide section on the FACT website for practical ways to decrease your family's exposure to EDCs.

The Endocrine System

The endocrine system consists of a series of glands that are distributed throughout the body. 

The human endocrine system.

Each gland produces one or more hormones. Hormones are natural chemicals that are produced in cells within a gland and released into the circulatory system, where they travel through the bloodstream until they reach a target tissue or organ. There, they bind to specific receptors, triggering a response such as production of another hormone, a change in metabolism, a behavioral response, depending upon the specific hormone and its target.  Some of these hormones and glands are detailed below.

·      The pituitary gland makes eight or more hormones, including prolactin and growth hormone. Prolactin is involved in making breast milk, and it is only synthesized and released from the pituitary glands of women who are breast feeding their infants.

·      Growth hormone is synthesized throughout life.  It is important for growth and development in childhood and for building and maintaining muscles and the skeleton in adulthood.

·      The pancreas produces the hormone insulin, which circulates in the blood and is necessary for normal regulation of    blood sugar levels.

Each organ require hormones to be present in precise amounts at particular times.  The needs of each organ and tissue change through the life cycle.  Circulating in very low concentrations, hormones regulate the body’s response to different nutritional demands (e.g. hunger, starvation, obesity, etc.); they are critical to reproductive function; and they are essential to normal development of the body and brain.

Hormones have unique three-dimensional shapes that have corresponding receptors localized on target cells.  A receptor’s shape is complementary to its hormone, similar to the way in which one key (hormone) is specific to a lock (receptor).  The ability of a hormone to activate its receptor depends upon several factors, including how much hormone is synthesized and released by the endocrine gland, how it is transported through the circulation, how much reaches the target organ, and how potently and for how long the hormone can activate its receptor. These properties are fundamental to normal hormonal signalling. EDCs can interfere with any – and all – of these steps.

Illustration of EDCs disrupting hormones.

EDC Dangers

EDCs are defined, as: “an exogenous [non-natural] chemical, or mixture of chemicals, that interferes with any aspect of hormone action”.

The incidence of endocrine-associated pediatric disorders, including male reproductive problems (cryptorchidism, hypospadias, testicular cancer), early female puberty, leukemia, brain cancer, and neurobehavioral disorders have all risen rapidly over the past 20 years. The prevalence of developmental disability in US children increased from 12.84% to 15.04% between 1997-2008.

The preterm birth rate in the US, UK and Scandinavia has increased by more than 30% since 1981, an outcome associated with increased rates of neurological disorders, respiratory conditions and childhood mortality, as well as obesity, type 2 diabetes, and cardiovascular disease in adulthood. 

Data from human, animal, and cell-based studies have generated considerable evidence linking EDC exposure to these and other human health disorders.

The increased endocrine disease rates parallels increased production of manufactured chemicals. Global production of plastics grew from 50 million tons in the mid-1970s to nearly 300 million tons today. Similar trends hold for other chemical sources including pesticides, fire retardants, solvents, and surfactants (detergents, foaming agents). Sales for the global chemical industry have sharply increased from USD$171 billion in 1970 to over USD$4 trillion in 2013. These and other chemicals such as PCBs, BPA, and phthalates, are detectable in human serum, fat, and umbilical cord blood.


Matrix showing products that contain certain EDCs.

While associations between increased human chemical exposures and increased disease rates are suggestive they do not ‘prove’ that the two are linked. Data from cell-based studies, animal studies, and other experimental systems over the past few decades, however, have provided a wealth of evidence supporting this direct link. Proving a chemical contributes to a human disease would require exposinga group of humans and then observing the resulting disorder. Though this type of testing is done for pharmaceuticals, it would be unethical and impossible for testing the impact of toxicants on humans. Conclusions about EDC-related health effects, therefore, have to be made using data from epidemiology (study of incident, distribution, and control of diseases) studies, which can only reveal associations, and by making inferences about human risk from experimental data obtained from animals or cell-based models. An additional challenge is that humans are exposed to a complex mixture of chemicals across the lifespan, making it difficult to establish if health effects result from exposure to a few problematic chemicals or a collective combination of chemicals. Therefore, linking any specific EDC to any specific disease is difficult.


Matrix showing disorders linked to EDC exposure.

EDC Exposure Dangers for Fetuses and Infants

Early life, especially the fetus and infant, is a period of vulnerability, when any disruption to natural processes may change, sometimes irreversibly, the structure and/or function of a physiological system.  Since EDCs interfere with hormone actions, their exposures during a sensitive developmental period can have both immediate as well as more latent consequences. For instance, in rodents, first trimester exposure of a fetus to the pesticide chlorpyrifos, a known EDC, can alter thyroid structure and function in the offspring when they become adults, while second trimester exposure to chlorpyrifos can increase insulin levels in the adult offspring.  An organ that is developing during the time of the harmful exposure is more likely to be affected than an organ that has already completed development.  In particular, the nervous system, the development of which begins in early gestation and continues well into childhood, has been found to be very sensitive to EDC exposures.

Children are also at greater risk of exposures than adults for a number of reasons including that:

1) they are exposed to many fat-soluble contaminants in breast milk or in formula;

2) they put their hands and objects in their mouth far more often than adults;

3) they live and play close to the ground; and

4) they have greater skin area relative to their body weight than adults allowing for more absorption of chemicals.


The harm of exposures to children is thus due to differences in the ways they may be exposed, their developmental vulnerability, and a longer life expectancy with a much longer horizon for exposure to manifest as disease.  New scientific insights of EDCs suggests that “the timing makes the poison” in considering the vulnerability of the developing organism.  Therefore, the concept of “safe exposure threshold” does not apply to EDCs. 

Ways we are Exposed to EDCs

EDCs are a global and ubiquitous problem. Exposure occurs at home, in the office, on the farm, in the air we breathe, the food we eat, and the water we drink. Of the hundreds of thousands of manufactured chemicals, it is estimated that about 1000 may have endocrine-acting properties.

Exposure to EDCs commonly occur in the following ways:

·      In the form of pesticides, algicides, and other chemicals designed to kill unwanted organisms. Spraying of homes, agricultural crops, and ponds releases airborne and sedimented chemicals that are inhaled, get on skin, and are ingested from sprayed food. 

·      Food and water containers that contain chemicals that may leach into foodstuffs and beverages such as bisphenol A (BPA) and there is growing evidence that BPA substitutes such as BPS and BPF are also EDCs.

·      Intravenous and other medical tubing contains some classes of known EDCs such as phthalates, allowing direct contact between chemicals and the bloodstream.

·      Inorganic lead in children’s products

·      Brominated flame retardants in electronics

·      Personal care products (phthalates, triclosan, mercury, alkylphenol polyethoxylates)

·      Textiles and clothing (perfluorochemicals), and

·      Building products (high-volume use of brominated flame retardants and chemicals in insulation).

For more information on each type of exposure and recommendations to decrease exposures see Introduction to Endocrine Disrupting Chemicals (EDCs): A Guide for Public Interest Organizations and Policy-Makers.

Check out our Guide section on the FACT website for practical ways to decrease your family's exposure to EDCs.