Endocrine systems control development, growth, reproduction, behaviour, metabolism and immunity in humans and animals. The natural hormones in the body (such as testosterone, oestrogen, thyroid hormone, insulin) are chemical substances that form a complex and sensitive system.
Concern has arisen due to suspicions that both industrially manufactured and natural chemical substances could disrupt the functioning of natural endocrine systems in various ways, causing harmful effects on human health or the environment. Such substances are called endocrine disruptors. Substances that affect the endocrine systems without causing negative effects are called hormonally active substances or substances with a hormonal effect.
The International Programme on Chemical Safety (WHO/IPCS, 2002) defines endocrine disruptors as follows: An endocrine disruptor is an exogenous (from outside the body) substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations. Endocrine disruptors are believed to affect the functioning of the endocrine system in at least three different ways: by mimicking the effect of the body’s natural hormones, by inhibiting the effects of natural hormones or by affecting the hormone concentration in the body.
Some of these chemicals have been found to cause adverse effects in several natural species (such as fish, birds and mammals), considered to be due to the substance’s effect on the endocrine system. These adverse effects include harmful reproductive and developmental disorders. Endocrine-disrupting effects have also been observed e.g. in the decomposition products of alkylphenol ethoxylates used in detergents and textile processing, nonylphenols, phthalates and bisphenol-A used as additives in plastics, DDT and certain other pesticides, as well as PCB compounds.
It has been suspected that exposure to endocrine disruptors is connected to the incidence of health hazards in humans at the population level, which has caused concern. Such health hazards include decreased sperm counts and an increase in certain types of cancer. There are also many other contributing factors in the background, but the effects of chemicals have not been excluded. The research is controversial, and the connections have not been conclusively proven yet. Much more research is still needed.
The use of several industrially manufactured substances suspected of having endocrine-disrupting effects has already been limited or, without special licence, prohibited, on the EU market due to their effects on reproduction or other hazardous characteristics. However, many potential endocrine disruptors are still in use, and further research of them is ongoing. It should also be noted that substances may have several different hazardous characteristics, with endocrine disruption being just one among others.
The modes of action of endocrine-disrupting chemicals are complex. Some of these modes of action and the related harmful effects are still rather poorly known. To date, there are no testing methods to enable the identification of all harmful effects caused by endocrine-disrupting substances. The OECD is developing testing methods that would allow the identification of endocrine-disrupting substances. In addition, the instructions ‘Guidance document on standardized test guidelines for evaluating chemicals for endocrine disruption’ (2012) have been developed to aid in their evaluation. You can find more details on the development of test method on OECD’s website.
In the European Union, the risk assessment and management of endocrine-disrupting chemicals is considered important. In 1999, the European Commission released a communication for the new community strategy for endocrine disruptors, including short-term, medium-term and long-term proposals for actions in accordance with the precautionary principle. As a short-term action, the Commission published a priority list of substances suspected to be endocrine disruptors for further study in 2001. In order to compile the list, the scientific evidence of about 500 substances was evaluated for endocrine-disrupting effects. As an overview, the Commission has published the report ‘State of the Art of the Assessment of Endocrine Disruptors’ (2012). The Commission also maintains a website on endocrine disruptors.
Endocrine disruptors are referred to several times in EU legislation, such as the REACH Regulation, the Biocidal Products Regulation, the Cosmetics Regulation and the Plant Protection Products Regulation. At the moment, there is no scientifically or legally uniform method of defining an endocrine disruptor. The European Commission is currently preparing scientific criteria for endocrine disruptors. The aim of the criteria is to define the kind of scientific evidence required for identifying an endocrine disruptor. The intention is to apply the criteria to the legislation on chemicals, so that endocrine disruptors could be taken into account better in the risk assessment of chemicals and when selecting risk management procedures for the use of chemicals. The Joint Research Centre established by the Commission submitted a proposal on the criteria in 2013.
The European Chemicals Agency (ECHA) has established the Endocrine Disruptor Expert Advisory Group that assesses the potential endocrine-disrupting effects of chemicals being evaluated in accordance with the REACH Regulation and the Biocidal Products Regulation of the EU. More information on the group’s activities can be found on ECHA’s website.