Chemical of the Month: Endocrine Disrupting Chemicals (EDC’s)

By Kristina Vile, AllergyCertified

Hormones play a central role in your body and in communicating between different parts of your body – they constitute a communication system without direct contact between recipient and sender. The endocrine system controls both growth and development in children, regulate body functions in adults and play a central role in reproduction. Hormones communicate to cells in the body with messages on what to do and are delivered via the blood stream. They are carefully tuned to maintain a fine balance in the body and they play a particularly important role during the development of the fetus, where complicated processes are to be started and stopped within a tight program for proper development and growth.

What is it?

Endocrine disrupting chemicals (EDC’s) are chemicals who can disrupt the endocrine system in humans and other animals. All systems in the body, controlled by hormones, can potentially be affected by these. The consequences can be difficult to map and demonstrate. When talking about hormone disruptions, there are some basic mechanisms in the endocrine system that can be affected:

Sorry, we are disturbing:

  1. Disrupting the hormone production: Substances who can up regulate, down regulate or stop production of natural hormones.
  2. Disrupting the hormone transport: Most hormones are produced distant from the recipient cell and rely on transport molecules to get to the right places in your body. The transport molecules can be disturbed so that the hormones do not end up in the right places. Thus, the effect of the hormone does not reach the recipient cell.
  3. Occupation of site: A substance can occupy the site of the recipient cell receptor, where natural hormones normally bind to send signals to the cell. This can either cause amplified, reduced or blocked signal to the recipient cells.
  4. Influence on hormone degradation: A substance may affect the breakdown of hormones in the body, which usually break down after delivery of the signal. They can both down regulate, stop or increase the breakdown of the hormone, which affects the concentration of the hormone in the body.

Who can interfere with your hormones?

EDC’s may come from different places. In general, four types of endocrine disrupting chemicals can be mentioned:

  1. Natural hormones, which is formed in animals, but may be potentially harmful to other species.
  2. Natural chemicals, which covers various substances formed in plants or fungi, including the so-called phytoestrogens.
  3. Synthetic hormones made for medical use such as birth control pills.
  4. Synthetic chemicals made for use in agriculture, industry and consumer products.

Children are the most vulnerable humans

The consequence of endocrine disruptions can affect all of us, but particularly vulnerable are children and especially unborn children. The window for disrupting the hormones is much greater in fetuses and children for the simple reason that this is where the body’s organs and systems are developed; orchestrated by hormones. Hormones are crucial for development and growth in fetuses and children and disturbances can lead to direct developmental defects but can also lead to more hidden effects and delayed changes that may have consequences later in life, for example by affecting sperm quality.

The exact mechanisms whereby EDC’s affect tissue during development and cause disease later in life is missing insight. It is clear, however, that hormones play a role in the differentiation of cells in the development of tissues and organs. When these are fully developed, the hormones have a different role, namely communication between tissues and organs. Therefore, during the development of tissues and organs there is a particularly vulnerable period to permanent changes that may show as disease later in life.

Under suspicion or convicted?

In order to regulate EDC’s it is important to have criteria to decide when a substance is considered endocrine disrupting or in other words; what results from test methods is needed to suspect or convict a chemical. To do this it is important to have test methods to detect endocrine disruptions and to have an international standard of test methods. The EU Commission have been working on such criteria and the scientific criteria to identify endocrine disruptors will apply from medio 2018.

When testing for endocrine disrupting probabilities of chemicals there are several challenges. One challenge is that EDC’s are expected to have effects even in low doses and as cocktails and this makes it very difficult to determine if a safe concentration limit exist. Also, EDC’s may not follow a rising dose response curve. Another challenge is that in animal studies, the risk assessment is not always assessed during development, which is the most sensitive window for EDC action, and are often not followed for their lifetime, which would be most appropriate to assess resulting diseases.

Previously there has not been a widely agreed system for evaluating the strength of evidence of associations between exposures to chemicals (including EDC’s) and adverse health outcomes and up until now chemicals have been evaluated case-by-case under REACH.

In 2010 the EU commission initiated working on criteria for EDC identification. The Danish proposal for EU criteria on EDC’s is founded on the WHO/IPCS definition of endocrine disruption and proposes three categories:

Category 1- Confirmed ED: Substances are placed in category 1 when they are known to have caused ED mediated adverse effects in humans or animal species living in the environment or when there is evidence from animal studies, to provide a strong presumption that the substance has the capacity to cause adverse ED effects in humans or animals living in the environment.

Category 2a – Suspected ED: Substances are placed in category 2a when there is some evidence for ED effects from humans or experimental animals, and where the evidence is not sufficiently convincing to place the substance in category 1.

Category 2b – Substances with indication of ED properties (Indicated ED): Substances are placed in Category 2b when there is some in vitro/in silico evidence indicating a potential for endocrine disruption in intact organisms.

Another complication when looking at exposure to possible EDC’s, is the fact that some chemicals are used in a wide variety of products. An example is UV-filters where some have shown to be ED. UV-filters are used in sunscreen to protect the skin against sun damage. But they are also used in a range of other products such as washing powder, plastic, clothes, in printing, paint etc. where they protect against e.g. bleaching of color. This is an extremely important piece of information since we often see that cosmetic products – both sunscreen, but also other cosmetic categories, are given much attention as the bad guys when it comes to chemicals in our daily lives. In a resent published PhD thesis by Marianna Krause from Department of Growth and Reproduction, Rigshospitalet, a study on urine samples from kindergarten children during both summer, where sunscreen application was expected, and winter showed a presence of UV-filters – also during winter where Danish children are not expected to be applied with sunscreen. Furthermore, the measured UV-filters was among those shown to be allergenic and/or to have endocrine disrupting properties. The conclusion was that an unintended exposure exist which can be potentially harmful. This shows that when thinking of harmful chemicals there are other routes of exposure than the obvious one. For example, it is likely that Danish children get exposed to UV-filters from their toys, play dough, finger paints or clothes – all these products can contain UV filters because the producers want to see the products last as long as possible without bleaching or getting fragile from sun exposure. This calls for great attention on EDC’s to avoid exposure causing health risks, from all possible sources.


Even though we are an allergy certification, we also investigate whether the ingredients used have endocrine disrupting properties. In products with the AllergyCertified logo we do not allow substances which have been shown to be endocrine disrupting.