Multiple Chemical Sensitivity, MCS

Chemicals are present in our daily environment in ever-increasing quantities,
which cause some public concern. The occurrence of a new health disorder, where
some people suddenly can no longer tolerate the odour of chemicals at doses far
below those known to cause harmful effects, has caused even more concern. The
condition referred to above is called Multiple Chemical Sensitivity (MCS),
where a previously healthy individual experiences multiple, non-specific
symptoms when exposed to chemical odours at very low concentrations.

A newly published Denish report covers these issues. MCS has received much
attention, especially in North America. In order to be able 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 cause 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 Denmark and abroad, and contributes
hereby, hopefully, to a better understanding of the MCS problems.

The report is based on a study of the scientific literature, meetings,
workshops and reviews, most of which are from the US. The practises of
environmental administrations in European countries and in North America have
also 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

In the US 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 US, Sweden and France. These
are comparable to the Danish cases.

Prevalence studies from the US 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, somatization 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.

Based on the information of this report the following attempts are indicated
for reducing exposure to chemicals:

  • Generally, limited use of chemicals in everyday life
  • Limited use of volatile chemicals (e.g. scents) and chemicals in the form of
    aerosols for personal and household use.
  • Limited use of pesticides and biocides.

Special attention might be directed towards:

  • Cosmetics, cleaning products and products for surface treatment regarding
    their use and content, and
  • In-door air pollution from building materials and furniture as well as
    tobacco smoke and exhausts from traffic.

Preventive action for MCS could contribute to a better protection of all those
exposed to chemicals, especially the most vulnerable groups. Recognition of the
illness MCS would lead to a better understanding of MCS patients and their

Further information

AplusA-online.de - Source: European Agency for Safety and Health at Work