Multiple Chemical Sensitivity, MCS

9 Summary, conclusions and recommendations

9.1 Summary
     9.1.1 Aim
     9.1.2 Description and definition of MCS
     9.1.3 International activities and research
     9.1.4 Examples of MCS
     9.1.5 Prevalence
     9.1.6 Possible mechanisms
     9.1.7 Methods of examination and diagnosis
     9.1.8 The handling of MCS by the authorities in the US and Europe
     9.1.9 Conditions in Denmark
9.2 Conclusions
9.3 Recommendations

9.1 Summary

9.1.1 Aim

During the last two decades physicians all over the World, but especially in North America, have described a new illness called Multiple Chemical Sensitivity (MCS). Persons with this illness experience various symptoms when exposed to odours/scents in very low concentrations, which do not bother most people. People with MCS demonstrate no objective physical bodily changes.

The knowledge of MCS is limited in Denmark, and just how many suffer from MCS is uncertain. In connection with the planning of a focused effort against chemicals in the environment it is important to get a clearer picture of the possible causal relationships and of the incidence of MCS in Denmark.

This report gives an overview of the knowledge of and the experience with MCS by systematically going through the available literature, expert opinions, and experience in other countries and from other authorities.

The report attempts to answer the following questions:

  1. Does objective documentation for MCS being caused by low concentrations of chemicals exist?
  2. Are the mechanisms behind MCS documented?
  3. Which chemicals and circumstances of exposure are particularly relevant for Denmark in relation to MCS?
  4. What are the possibilities for prevention?

9.1.2 Description and definition of MCS

MCS has many names, it is not a well-defined illness, and other conditions present symptoms quite similar to those of MCS. These can be indoor climate symptoms, the Gulf War Syndrome, chronic fatigue syndrome, fibromyalgia, etc. All these conditions are collectively called environmental illnesses. The characteristics described below, consistent with the definitions of several scientific associations and researchers, are used to separate MCS from other environmental illnesses.

MCS is usually provoked by an initial exposure to a chemical, usually in a high concentration. Then symptoms arise from several organs, in connection with exposure to chemicals in low concentration. The symptoms are often connected to an odour. Odours from several non-related chemicals can give symptoms, which disappear when exposure ceases. The symptoms can be provoked by re-exposure. If the illness is to be diagnosed as MCS, the patients must not suffer from another disease, which might be the cause of the symptoms.

Traumatic incidents (physical and psychogenic traumas or serious infections) have also been reported to elicit MCS.

During initial exposure, phase 1, exposure to a chemical changes the pattern of reaction towards chemicals. Phase 2, the “trigger” phase starts a few months later, when odours in low concentrations provoke an “attack”. In time, the number of odours provoking attacks are gradually increased to include usual ”every-day odours” such as perfumes, car exhaust, etc. With time, the symptoms also increase in number. The course of events is usually chronic (a spontaneous recovery is, however, possible).

Some patients experience health complaints a few times a week and can continue working. Others experience them daily, and are forced to stop working or to cut down on their daily activities.

9.1.3 International activities and research

With support from institutions and experts in medical research, the American authorities arranged numerous expert meetings dealing with all aspects of MCS during the period 1990-1998. Several hundred scientific papers and reports from meetings on illness mechanisms and research strategies have been published. All of the medical science organisations have put forward their official opinions in the discussion on MCS.

9.1.4 Examples of MCS

In North America most of the MCS cases are referred to exposure to pesticides and other chemicals in the home. Based on the patterns of use of chemicals in the US compared to Europe/Denmark, it can be assumed that exposure of people in general to chemicals and degassing from building materials and home furnishings is greater in the US than in Europe and especially in Scandinavia. In Europe and Scandinavia, most MCS cases are caused by exposure at work, typically where different types of organic solvents, pesticides or other chemicals are used.

Few investigations from Denmark, Sweden, and France describe MCS in persons who have been exposed to solvents. Cases of MCS due to indoor use of wood preservatives are reported from several European countries, including Denmark (Rentolin). A number of persons who complain about the indoor climate may have MCS. These are primarily persons who are bothered by odours almost everywhere, and not only in certain buildings.

Triggering factors:

Phase 1: Chemicals (primarily in high concentrations) such as organic solvents and other volatile substances (VOC substances), pesticides, hair-care products, chlorine fumes, etc.

Phase 2: All types of chemicals in low concentrations (the ones mentioned under phase 1, typically gasoline, exhaust gasses, cleaning materials, perfumes, detergents, personal care product, tobacco smoke, asphalt fumes, and fumes from household articles).

9.1.5 Prevalence

The frequency of MCS among the general public in the US is 0.2-6%, according to figures based on medical diagnoses. The frequency of self-reported (subjective) symptoms due to a selection of odours is considerably higher.

The frequency of MCS among the general public in Europe has not been investigated. It is expected to be lower (at about 1%) than in the US due to less indoor use of chemicals.

Among people in the US and Europe, who have previously been exposed to solvents, a larger percentage has been diagnosed to have MCS than in the public in general. It is presumably between 1% and 12% according to figures from the US.

The prevalence in Denmark is not known, but it is assumed to be about 0.1-1%, presumably due to a pattern of use involving less exposure than in the US.

9.1.6 Possible mechanisms

Many suggestions for causal mechanisms of MCS have been put forward. Research has not yet established certain knowledge of and documentation for the causes and mechanisms of the illness. So, none of the proposed mechanisms can be excluded in advance.

The most cited mechanism of illness is the immunological one. During the first years, when MCS was described as a hypersensitivity illness, many sought an MCS-specific biomarker. There is, however, still no proof of the existence of an immunological mechanism.

Mechanisms in the mucous membrane of the nose are considered by many to be the final explanation of MCS. The terminal fibres of the olfactory nerve (nervus olfactorius) in the mucous membrane of the nose sense chemical stimulations such as smells, while chemicals act as irritants to the terminal fibres of another nerve (nervus trigeminus).

Both brain nerves transport the impulses received to brain centres along different routes, where they create different responses. It is still unclear whether both nerves are involved in the illness mechanism.

Nerve fibres from the olfactory nerve go directly to nerve centres in the brainstem. Chemical odours can create a so-called neural sensitisation of one of these nerve centres, which are directly connected to the other centres, and which influence behaviour and organs via the autonomous nervous system as well as the overriding regulation of the hormonal balance of the body.

Experiments have shown that external physical and chemical stimuli can cause sensitisation by way of a so-called “kindling”[*] manoeuvre. Certain cognitive and behavioural changes, which can fit the mechanism mentioned above, have been observed in patients with MCS. But it has not been proven directly that this mechanism causes MCS.

Another hypothesis points at psychological mechanisms as the cause of MCS. People with MCS are no doubt under psychological pressure, but whether this pressure causes or is caused by MCS is unclear. Many are of the opinion that a conditioned reflex mechanism founded on a previous trauma can explain MCS. Others point at stress and inability to “cope” as causal factors. It seems that people who are generally more sensitive to external environmental stress are at greater risk than others of developing MCS in connection with a given chemical impact. MCS is described as a process of somatization in connection under psychosocial and environmental stress.

A more recent hypothesis speaks of an initial toxic impact reducing the tolerance of organs (toxic-induced loss of tolerance), after which chemical odours can create abnormal responses from several organs. This hypothesis corresponds well to the actual course of events in MCS. But it has not yet been demonstrated how tolerance is lost nor how this creates MCS symptoms.

Finally, experts in holistic, ecological medicine are of the opinion that MCS is caused by a weakening of or a defect in the defence and detoxification capacity of the body towards external chemicals, which creates imbalances in the internal functions of the body. The evidence for this hypothesis, presented by the clinical ecologists, cannot be approved according to the requirements for objectivity, standardisation and quality control established by the medical sciences.

9.1.7 Methods of examination and diagnosis

Just as there is no certain diagnosis for MCS, there is no certain test to confirm or disconfirm the diagnosis. Medical experts from the US have set up scientific guidelines aimed at attaining a diagnosis of the illness and at following up on MCS patients.

9.1.8 The handling of MCS by the authorities in the US and Europe

After a decade with much research and many meetings in the US, the authorities' activities concerning MCS have slowed during recent years. The EPA and NIOSH are currently not taking any prophylactic action concerning MCS.

The health authorities in Canada were prepared to recognize MCS in spite of the lack of diagnostic certainty. But they had to give up the plan because of lack of support. The interest in MCS has also been dwindling in Canada. But decentralized activities are going on between local environmental and health authorities and the public involving voluntary reductions in the use of personal scents and scent-containing products in public places (schools, hospitals, town halls, public transport, some workplaces).

In most European countries, MCS is not so well known, and certainly not recognized as an disease. None of the environmental authorities approached were in the process of completing prophylactic activities concerning MCS. Sweden and Germany, where clinical-ecological centres for diagnosing and treating environmental illnesses are found and where the media regularly deal with these illnesses, are conducting research activities connected with MCS (frequency, illness mechanisms, and criteria for diagnosis). At present, Germany has the most active research and development program concerning environmental illnesses in general and MCS in particular.

9.1.9 Conditions in Denmark

In Denmark the expressions odour hypersensitivity and solvent intolerance are commonly used instead of MCS. The condition is not recognised as a disease in itself and is not registered. Except for occupational and environmental physicians, specialists in psychosomatic (functional) illnesses, and a few oto-rhino-laryngologisty physicians, only a few Danish physicians know anything about MCS. Mostly occupational and environmental physicians have examined patients with MCS-like symptoms. Some patients in Copenhagen, including some who have previously been exposed to solvents, have been examined at the Department of Oto-rhino-laryngology of the National Hospital of DenmarkCopenhagen University Hospital (Risgshospitalet), using a special open provocation test. This test confirms physiological reactions to odours in MCS patients.

The Danish MCS Organisation has approached the Danish EPA concerning the reduction of scents in the environment.

The Danish authorities have not dealt comprehensively with MCS, except when approached directly.

It seems possible to direct a possible prophylactic effort from the authorities towards reducing the risk of chemical exposure (relevant for the initial phase and the trigger phase) and – as far as possible – reducing the incidence of chemical odours in low concentrations (relevant for the trigger phase). This could include regulation in certain areas, and increased dissemination of information aimed at eliminating situations, where the use of chemical products and materials leads to high exposure. It could also include more initiatives directed towards reducing the use of “unnecessary chemicals”, especially pheromones.

The health authorities need to improve examination, diagnosis, treatment, guidance, and follow-up of MCS patients.

A preventive effort is also needed in the working environment. Based on the relatively few data on MCS cases in Denmark, it can be assumed that exposure at work is of special significance for the development of MCS.

Before a preventive effort is planned, a detailed mapping of several aspects concerning the use of and exposure to chemicals, their effects on health, and the extent of the MCS problem should be carried out.

9.2 Conclusions

Multiple Chemical Sensitivity (MCS), which is called odour hypersensitivity in Denmark, is a condition with many health complaints from different organs, which occurs in certain people, when they are exposed to low concentrations of chemicals. Most international experts within the field agree, on the basis of epidemiological data, that MCS is a reality.

MCS or odour hypersensitivity is not a recognized disease and is, therefore, not listed in the WHO's International Classification of Diseases, version 10 (ICD-10).

Relatively few people get MCS, which is assumed to have two phases. The first phase usually involves exposure to a chemical, most often in high concentrations. During the second phase, exposure to chemicals in low concentrations creates symptoms. These occur in various organs (the central nervous system, parts of the airways and lungs, skin, digestive system, joints, muscles, etc.).

In Denmark, some of the patients at the clinics of occupational medicine fit the MCS criteria mentioned in this report. Most of these patients have probably been exposed to solvents. People, who have been exposed to considerable concentrations of other toxic chemicals at work or in their homes (pesticides, hair-care products, wood preservatives, chlorine fumes), can develop MCS. It is uncertain whether this is due to solvents in many of these products.

Many illness mechanisms, both physical and psychogenic, have been proposed. But a direct causal relationship between exposure to chemicals in low concentrations and the symptoms/effects mentioned has yet to be proven scientifically.

Much seems to indicate that MCS is usually found in persons, who are generally sensitive to external environmental stress.

MCS occurs in 0.2-6% of the population in the US. Based on preliminary estimates and on knowledge of differences in the use of chemicals, including pesticides, between Denmark and the US, the prevalence of MCS in the population of Denmark is estimated to be about 1%. Preliminary figures from occupational medicine investigations indicate that the prevalence of MCS is 1-12% among those who have been exposed to chemicals such as organic solvents and pesticides at work.

The term multiple chemical sensitivity is inappropriate, since it puts focus on causes and mechanisms, which have not been finally clarified.

In recent years several people have preferred the name idiopathic (unknown) environmental illness (IEI), which is a more neutral term.

In Europe the environmental and health authorities are aware of the existence of MCS, but interest in registering cases and in research into the causes of MCS has been limited. During the last couple of years, Sweden and Germany have performed large public surveys and MCS research.

9.3 Recommendations

Although great uncertainties and a great need for more knowledge concerning MCS still exist, our present knowledge indicates that MCS is a reality and that some people are particularly sensitive to exposure to low concentrations of chemicals.

It is probably impossible to cure many of the people who already have MCS. But prophylactic measures can be taken in order to avoid that more people get MCS. And the daily lives of those, who already have MCS, can be improved.

The most important overall goal must be to limit the risk of exposure to chemicals in high as well as low concentrations.

In order to prevent MCS altogether, it is important to avoid initial exposure. In this context, special attention should be given to exposure to high concentrations of chemicals, e.g., solvents evaporating from large painted surfaces and spraying in enclosed spaces with, e.g., hairspray.

A general reduction of the chemical load would also be a step in the right direction to prevent new cases of MCS and symptoms in people, who already have MCS.

Finally, it is important that we, as consumers, know when we are being exposed to chemicals, and which chemicals they are. As consumers, we can contribute to preventing ourselves and others from getting MCS by avoiding exposure to high concentrations of volatile chemicals indoors, e.g., when painting large surfaces, and by not using strong-smelling products such as perfumes and highly scented products.

At present it is difficult to focus efforts against MCS, as long as certain knowledge concerning illness mechanisms, causality and diagnosis is lacking. An effort against MCS requires more knowledge of:

  1. Incidence, causality, and effect mechanisms,
  2. use of chemical products containing volatile substances,
  3. exposure indoors, and
  4. use of volatile substances in chemical products and goods.

Based on the present overview, and on considerations of hygiene and the general viewpoint that unnecessary exposure to chemicals and unnecessary chemicals should be avoided, it seems relevant to increase efforts within the following areas:

  • General reduction in the every-day use of chemicals,
  • especially reduction in the use of volatile substances (including pheromones (perfumes)) and aerosols, and
  • reduction in the use of pesticides and biocides.

It seems particularly relevant to focus on the use of additives (especially perfumes) in cosmetics, cleaning materials, and surface treatments, and to focus on indoor climate problems, including evaporation from building materials and indoor furnishings, and on environments/situations involving exposure to tobacco smoke and exhausts from traffic.

By generally focusing on reducing the every-day use of chemicals, the MCS problem can contribute to the general protection of exposed and sensitive groups of people, such as children and expectant mothers, thereby preventing some additional cases of MCS. A general recognition of MCS will, hopefully, also lead to a better understanding of the MCS patients and their problems, and hereby contribute to making their every-day life easier.


Footnotes

[*] Kindling is expressed through an experimental method for determining a change in the reaction of the nervous system to external stimuli. By repeating chemical or electrical stimulation with so low concentrations/doses that they do not provoke any response, a lowering of the dose, which triggers cramps, can be obtained.

 



Version 1.0 March 2005, © Danish Environmental Protection Agency