Hormone (Endocrine) Disrupting Substances in the Environment
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Introduction
In recent years there have been growing concerns about chemicals in the environment interfering with hormone (or endocrine) systems. There is speculation that these could be causing effects on reproduction and development in man and wildlife.
There are still considerable uncertainties about the effects and possible role that chemicals in the environment might play. The issue of endocrine disrupting chemicals in the environment is of concern as there could be far-reaching effects on reproduction and development in current and future generations.
This material provides some background information on hormone disrupting substances in the environment. It also provides details of some of the things Government is doing to address the issue.
- The endocrine system
- Endocrine disruption
- Effects of endocrine disruption
- Endocrine disrupting substances
- Government Activities
Endocrine Systems
Endocrine systems are present in humans and all higher animal species. They are highly complex and coordinate and regulate internal communication between cells in our bodies so that a constant internal environment is maintained. They also play an important role in growth and development. The endocrine system releases hormones that act as chemical messengers. These messengers interact with specific receptors in cells to trigger responses and prompt normal biological functions such as growth, reproduction and development. The endocrine system can respond to external stimuli, for example, stress. We do not have a detailed understanding of the functioning of endocrine systems.
Endocrine Disruption
Scientific studies have shown that some chemicals can interfere with the normal functioning of the endocrine system. In some cases this interference is enough to cause harmful effects in the organism itself or in the next generation (i.e. in their offspring). There are a variety of ways that this interference might occur including mimicking the behaviour of hormones, interfering with the hormone receptors in cells or interfering with production and removal of hormones. Many of the scientific studies carried out so far have focussed on feminisation and interference with the functions of the natural female hormone 17ß-oestradiol however studies are now being carried out looking at interference with the functions of the male sex hormone, testosterone, and other endocrine systems that influence growth, development and behaviour.
Part of the function of the endocrine system is to maintain a constant internal environment in response to external stimuli. This makes it difficult to decide what are acceptable changes and what is disruption. Common substances like water, salt and alcohol even in moderate quantities cause changes in endocrine activity but we would not necessarily consider these changes to be harmful.
Effects of Endocrine Disruption
Humans
Most of the concerns to date have been about effects on reproductive function and development. We know that children whose mothers took diethylstilboestrol (a potent oestrogen used to prevent miscarriage) during pregnancy in the 1950's and 60's suffered from abnormalities of their reproductive organs. Use of diethylstilboestrol was stopped in the early 1970's. We also know that the reproductive performance of certain farm and wild animals has been affected by their consumption of plants containing high levels of hormonally-active chemicals in situations where these plants from a major part of the animal's diet. We do not however know much about the effects of exposure to hormonally active chemicals in our environment. Generally, the chemicals so far suspected of being endocrine disrupters are much weaker than natural hormones such as those found in humans and we do not know enough to predict their effects if any.
Some scientists have reported decreases in human sperm count and quality, other scientists have not been able to detect these decreases. However there is general agreement that sperm counts vary in different parts of the world. Measurements of sperm counts in the UK suggest they fall in the middle range of the values found elsewhere. Scientists have also reported increases in certain cancers such as testicular cancer and some birth defects. Some scientists believe that they are caused by exposure to endocrine disrupting chemicals during pregnancy, other scientists disagree and we do not know at the moment whether this hypothesis true. We know that some aspects of lifestyle, e.g. diet, type of occupation, choice of underwear, can have profound effects. A lot of scientific research is going on find out whether the effects reported by some scientists are actually occurring and if so, what the causes might be.
Wildlife
Effects of concern have also been reported from studies in wildlife. In the UK, research on wild fish in rivers has shown that some male fish are suffering from effects related to exposure to chemicals that mimic female hormones (oestrogens). These effects include have been linked to exposure to chemicals in sewage effluent particularly natural female hormones and synthetic hormones from the contraceptive pill excreted by women. We don't know yet whether this is having an impact on fish populations. Effects in other animals including birds, reptiles and sea mammals possibly caused through hormone disruption have been reported from other countries particularly from areas where there has been a high level of chemical pollution in the past.
Endocrine Disrupting Substances
A wide range of chemicals have been suspected of having endocrine disrupting activity including some pesticides, industrial chemicals, by-products of industrial processes and components of sewage effluent. There are also natural hormonally active chemicals such as phytoestrogens present in certain foods such as soya. Much of the evidence for the activity of these chemicals comes from laboratory studies using isolated cells that react to exposure to hormonally active chemicals. It is very difficult to predict from these studies whether exposure to the chemicals can cause adverse effects in animals or people. At the moment we do not have a means of accurately identifying which chemicals are actually harmful through endocrine disrupting mechanisms.
There is one proven example of an endocrine disrupting substance causing adverse environmental effects: tributyl tin-based antifouling paint used on ship's hulls. This caused masculinisation of female sea snails so that they were no longer able to breed and populations declined or died out. This use of tributyl tin has been banned on small boats in the UK since 1987 and a recent EC Directive (2002/62) prohibits the application or re-application to all EU ships of tributyltin compounds as biocides in antifouling systems from 1 January 2003. This Directive implements the first part of the recent global ban on tributyltin agreed by the International Maritime Organisation; the second part, requiring the removal or sealing in of tributyltin antifouling paints on all ships by 2008, will be addressed by a European Council Regulation. In areas that were affected by leaching from small boats, populations of sea snails are now recovering.
Some organisations have produced lists of suspected chemicals. We have decided not to do this for the moment because of the lack of a reliable means for identifying which chemicals are actually harmful.
Government Activities
The Government is very concerned about the potential impact of endocrine disrupters and has instituted a large programme of research funded both interdepartmentally and by individual departments. At the same time, where particular chemicals have been strongly implicated we have proposed that these should be subject to a full risk assessment under European Regulations, which will lead to controls on the chemicals if deemed necessary.
Research
The Government is funding a considerable research programme to improve our understanding of the possible effects caused by exposure to endocrine chemicals and what these chemicals might be. This research is coordinated through the Interdepartmental Group on Endocrine Disrupters which is made up of representatives from Government Departments, Agencies and Research Councils and led by Defra. This Group has drawn on the expertise in the scientific community to advise on the research necessary. The Group recently published a report of its first three years' activities.
One of the Group's main tasks is to collate existing research on endocrine disruption being funded by its participating Departments and Agencies. The following tables (last updated May 2003) summarise such ongoing studies and research completed in the last two years:
- Ongoing studies and research (PDF 15kb)
- Completed studies and research (PDF 10kb)
Further information is available on our Help page about downloading or reading PDF documents.
We have established specific programmes of research on male reproductive health and endocrine disruption in the marine environment (EDMAR). A new research programme on endocrine disruption in invertebrates and top predators is currently being established. Research is also underway looking at whether suspected endocrine disrupting chemicals might be getting into our food or our drinking water. Further details can be obtained from the Food Standards Agency at: www.food.gov.uk (which includes details of all research and surveillance funded by the Food Standards Agency) and the Drinking Water Inspectorate at: www.dwi.gov.uk.
Action on chemicals
Where we have strong suspicions about the endocrine disrupting activities of specific chemicals we have already put these forward for a full risk assessment at the European level - this means that where risks are identified, European-wide measures will be taken to control the risks. The UK is leading the risk assessments for two chemicals that have featured prominently in discussions about endocrine disruption; these are nonylphenol and bisphenol A. For nonylphenol, the risk assessment has shown that measures to reduce the risks are necessary, these are currently being finalised. The risk assessment for bisphenol A is the subject of ongoing technical discussion with EU Member States, but there is sufficient indication of risk associated with particular uses to justify the development of a risk reduction strategy, which is being undertaken by the Department for Environment, Food and Rural Affairs in accordance with European Commission Technical Guidance.
Measures have already been taken on antifouling paints based on tributyl tin compounds that were found to affect the endocrine systems of marine organisms especially molluscs - see section 'Endocrine Disrupting Substances' above.
Other chemicals suspected of having endocrine disrupting effects include some of the Persistent Organic Pollutants (POPs). These are pollutants which remain in the environment for a long time and can be transported a long distance away from their original source. Negotiations on an internationally binding legal instrument began in 1998 following a Resolution from the UNEP Governing Council. Negotiations were completed in December 2000 and the Convention text adopted at a Diplomatic Conference in Sweden in May 2001. The UK signed the Convention in December 2001. Preparations for ratification have begun. The Government wants to see the Convention enter into force as soon as possible (after 50 ratifications) and is aiming to ratify as soon as possible without breaching obligations under international law. The UK expects to ratify in 2003.
Within the UK, the Government has published a Strategy for addressing all chemicals in the environment. This aims to ensure safe and sustainable use of chemicals while maintaining the competitiveness of industry, to phase out chemicals when the risks of environment and health are unacceptable and to make full information on risks from chemicals more widely available. Industry worldwide has agreed to examine the hazards from high production volume chemicals. The UK strategy sets out procedures for assessing the information generated by industry, identifying chemicals that are of particular concern and determining when risks are unacceptable and risk management is necessary. The Chemicals Stakeholder Forum has been established to advise the Government on assessment and management needs for individual chemicals was also announced in the Strategy. Chemicals of concern with endocrine disrupting properties can be addressed through these procedures.
In keeping with the precautionary principle, where there are serious concerns about a chemical, the Government will not hesitate to act to reduce risks.
Pesticides
The main group of pesticides that has been associated with endocrine disruption is the organochlorines (OCs). The OCs, methoxychlor, DDT (and its metabolites such as p,p'-DDE) and some of the various isomers of hexachlorocyclohexane (e.g. lindane, also known as gamma-HCH) have been shown to have weak oestrogen-like activity in some test systems.
Also, it has been suggested that there may be a relationship between the incidence of breast cancer in women and the concentration of organochlorines in their body fat. However the evidence is weak and not consistent.
Most organochlorine pesticides, with the exception of lindane were withdrawn from use. Last year, following advice from the expert Advisory Committee on Pesticides (ACP), lindane was banned for use as a seed treatment in the UK and following agreement at European level all other agricultural uses will be banned very shortly. The Pesticides Safety Directorate and the Health and Safety Executive have also recently reviewed the use of lindane in home and garden products and other non-agricultural uses. Ministers are currently considering the advice of the ACP on these reviews.
Some other pesticides have also been identified as potential hormone disrupters. Most of these are being reviewed under European legislation controlling the use of pesticides. Use of the fungicide, vinclozilin, has been considerable restricted in the UK because of its anti-androgenic activity in some mammalian assays.
Chemicals in food
Food is a source of exposure to potential endocrine disrupters both from naturally occurring chemicals in plants (know as phytoestrogens that can mimic human hormones) and environmental chemicals. In general, exposure to phytoestrogens is much greater than to endocrine disrupters from environmental and other sources. Further research is needed to confirm the effects, if any, in man of such chemicals at concentrations found in food and the environment. The Food Standards Agency has a large programme of research and surveillance devoted to chemicals, including endocrine disrupters, in food, which seeks to ensure that consumers are adequately protected. Details can be found on the Agency's website at: www.food.gov.uk.
Projects funded by the Food Standards Agency focus on exposure from food, test methods and possible effects in man and include surveillance of bisphenol A, dioxins, and other possible endocrine disrupters which might be found in our food.
Limits exist for a number of chemicals believed to have endocrine disrupting potential. These include limits on the content of certain chemicals in materials that may come into contact with food and might migrate into the food.
As part of its research programme, the Food Standards Agency is looking specifically at phytoestrogens. These are naturally occurring compounds with weak oestrogen-like activity that are found in some foods such as soya. Some groups believe that eating these foods may be beneficial. Other groups believe they may be harmful. A Working Group of the independent Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment with particular expertise in the clinical and scientific aspects of phytoestrogens, together with consumer representatives are carrying out a comprehensive review which will be published in late 2001.
Test methods and strategies
We need to know whether chemicals suspected of being endocrine disrupters are actually harmful. The Government is also actively pursuing the development of tests that can be applied to chemicals to determine whether or not they are endocrine disrupters. The tests need to be able to distinguish between those chemicals which are simply endocrine active, i.e. cause changes in the endocrine system, and those which are endocrine disruptive, i.e. cause harmful effects. If we cannot do this we might end up labelling common substances such as salt, alcohol and water as endocrine disrupters as our endocrine systems change when we are exposed to these even in moderate quantities. The Organisation for Economic Cooperation and Development (OECD) coordinates the development of internationally agreed test guidelines which, when performed to agreed standards, are acceptable throughout the world. This process allows resources to be used wisely and reduces the numbers of laboratory animals needed. OECD has established a group specifically to develop the test guidelines necessary to identify endocrine disrupting chemicals. Further details can be found at: www.oecd.org/ehs/endocrin.htm. The UK is actively participating in this work.
International cooperation
As well as participating in the work led by OECD, the UK is playing an active role in other international activities.
European Union
The European Commission published its Community Strategy for Endocrine
Disrupters in December 1999 at: www.europa.eu.int/comm/environment/docum/99706sm.htm.
This consisted of a series of short, medium and long term actions to address
endocrine disrupters. The first major commitment is to develop a European
priority list of endocrine disrupters for further evaluation. UK is contributing
to this process and will continue to cooperate with European partners
on addressing endocrine disrupters. See section on Chemicals above above
for details of European action on specific chemicals.
A series of round table meetings to discuss current scope and future direction of research into endocrine disruption was organised and hosted by the MRC Institute for Environment and Health (IEH), commissioned by Defra Chemicals and GM Policy Division. The fourth such meeting was held on 10 and 11 March 2004 and its report has been published and posted by IEH on the EC website; it can be accessed from http://europa.eu.int/comm/research/endocrine/background_links_en.html
International Programme on Chemical Safety
The International Programme on Chemical Safety has now published its assessment
of the state of the science on endocrine disrupters, which will be used
as the basis for co-ordinating further international cooperation on this
issue. Further details can be found at www.who.int/pcs/emerg_site/edc/global_edc_TOC.htm.
Cooperation with Japan
In 1999, the UK signed an arrangement with Japan to cooperate on research
on endocrine disrupters in the aquatic environment. This will promote
international cooperation and allow Japanese and UK scientists to exchange
ideas, information, techniques and personnel.
Some individual Departments and Agencies also have their own specific activities on endocrine disrupters.
Defra is not responsible for the contents or reliability of the linked web sites and does not necessarily endorse the views expressed within them. Listing should not be taken as endorsement of any kind. We cannot guarantee that these links will work all of the time and we have no control over the availability of the linked pages.
Page last modified 14 October 2004