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Duft- og kemikalieoverfølsomhed

Summary and conclusions

Chemicals are present in our daily environment in ever-increasing quantity, which causes some public concern. The occurrence of a new health disorder, where some people suddenly cannot tolerate any more the odour of chemicals at doses far below those known to cause harmful effects, has caused even more concern among citizens. The condition referred to above is called Multiple Chemical Sensitivity (MCS), where a previously healthy individual presents with multiple, non-specific symptoms when exposed to chemical odours at very low concentrations.

MCS has received much attention abroad, especially in North America. In DK only little is known about MCS and the medical establishment has not shown major interest in the condition. In order to fulfil the responsibility of proper environmental administration of chemicals several uncertainties about MCS need to be answered. Can chemicals cause illness at low concentrations? What mechanisms make people to become extremely sensitive to chemicals? What kinds of chemicals are involved?

This report gives a comprehensive review of the present state of knowledge and administrative practise regarding MCS in DK and abroad and hereby hopefully contributes to a better understanding of the problems regarding MCS.

The report is based on a study of the scientific literature, meetings, workshops and reviews, most of which are from the USA. Besides, practise by environmental administrations in European countries and North America has been registered.

MCS is a diffusely defined condition that can easily be confounded with other diffuse conditions because the symptoms of several conditions are very similar. Other conditions are fibromyalgia, chronic fatigue syndrome, sick building syndrome, Gulf War Syndrome and many more so-called environmental diseases.

The definition and tentative diagnosis of MCS is based on seven criteria (Cullen’s criteria) which also help to distinguish MCS from other environmental diseases.

Typical cases of MCS have been observed in Denmark among people who have been exposed to organic solvents or pesticides at work. Only a few domestic cases are known, e.g. from indoor use of different products for surface treatment of woods.

In the USA the majority of cases of MCS occurs in private homes and is due to exposure to indoor chemicals (VOC) and the extensive use of pesticides. There are several reports on MCS among workers from the USA, Sweden and France. These are comparable to the Danish cases.

Prevalence studies from the USA show figures between 0.2-6% in the general population. There are no prevalence figures for general populations in Europe. In a study of Swedish housepainters 30% had MCS.

So far there is no final proof of the causal mechanism of MCS. Some evidence on nasal inflammatory and neurosensory dysfunction, on neural sensitisation of the midbrain limbic system and on psychological mechanisms seems more convincing than the other proposed mechanisms, such as immunological, toxic loss of tolerance, somatisation and conditioned response.

At this stage it seems most likely that MCS occurs more often in persons who are more sensitive to environmental stressors than others.

There is clear evidence from the epidemiological literature that MCS exists, even though the exact mechanism is not known and there are no demonstrable organic or functional changes.

The condition MCS is assumed to pass on in two steps: the initial phase with exposure often to a high concentration of a chemical substance, and the trigger phase – the subsequent set off of a number of symptoms by exposure to low concentrations of chemicals.

The administrative and preventive action regarding MCS in most countries is that of expectation for the final proof of the causal mechanism of MCS. In Denmark a joint action for preventing chemical gases in building materials may have contributed to a reduction of indoor air pollution in Danish buildings which indirectly might have contributed to prevent some MCS cases. In Canada decentralised activities by the authorities with public participation for "no scent-policy" have been partly successful. The Swedish and German environmental and public health authorities are undertaking epidemiological studies on MCS at the present time.

A limitation of the risk for exposure to chemicals, both at high and low concentrations, seems to be the primary objective for preventing new cases of MCS. Avoidance of the initial exposure seems especially important, e.g. exposure to high concentrations of solvents after painting of big surfaces or to high concentrations of aerosols (e.g. hairspray) in closed rooms.

The consumers should always know when and to what kinds of chemicals they are exposed to. Consumers can contribute to prevent the break out of MCS-symptoms by avoiding indoor exposure to high concentration of volatile chemicals and by avoiding use of strongly smelling products, including use of perfume and scented products.