© by aha! Swiss Allergy Centre - Info on allergies - Pollen and air pollutants - car, exhaust gases,  green meadow

In Switzerland a good 40 per cent of the population, so around three million people, regularly breathe in too much particulate matter that is detrimental to their health. They live in densely populated areas or along busy roads, where the exposure limits set out in clean air legislation are often and sometimes hugely exceeded. Apart from cardiovascular conditions, diseases of the airways are among the most common health consequences.

The most dangerous component

Particulate matter is today the most dangerous component of air pollution. Some of the tiniest dust particles are discharged directly into the atmosphere (e.g. soot) while the remainder are only formed in the air by means of chemical processes with other substances. The term PM10 denotes the smallest particles with a diameter of less than one hundredth of a millimetre. They can get deep into the lungs and from there into the bloodstream. Forty-four per cent of the annual PM10 emissions arise during combustion processes. These particles mainly originate from diesel engines and wood fires. In summer ozone is an added health hazard.

Repercussions for allergy sufferers

Nowadays the scientific and medical community believe that the constant increase in allergic diseases in the last few decades can be attributed to a combination of factors. Genetic predisposition and presumably the "western lifestyle" play a role. There is growing evidence that certain pollutants at least increase the likelihood of allergic reactions. "Studies have shown that pollution is an added irritant factor in childhood asthma and that the symptoms are worsening", confirms Prof. Charlotte Braun-Fahrländer from the Institute of Social and Preventive Medicine of Basel University. However, the far-reaching SCARPOL studies which she has led have so far yielded no proof that air pollutants are causally responsible for the development of childhood asthma. "For hay fever and allergic sensitisation, no statements about causal connections with air pollutants can be made from an epidemiological point of view."

Pollen and particles – an aggressive mixture

Nevertheless, an interaction between airborne particulates and pollen has been demonstrated in recent laboratory studies: pollen from polluted areas are covered with pollutant particles and their allergen content is altered, which may intensify their effect. Researchers from the Technical University of Munich have proved in experiments that pollen grains and other protein-containing particles in the air are altered by nitrogen oxides and ozone (nitration) in such a way that they are able to cause allergies more easily. Nitrogen oxides and ozone are components of the summer smog caused by traffic. If there are increased concentrations of these substances, sufferers from pollen allergy usually find their symptoms get worse. The detrimental health effect, the reaction known as nitration, has not yet been conclusively explained.

Facts and figures

In Switzerland around 1.2 million people, roughly 20% of the population, are affected. The flower of a single blade of grass contains around 4 million flower pollen grains. Conifers are among the flower pollens that do not trigger any allergy. Visible as a yellow dust-fall in springtime, at most they cause irritation of the conjunctiva.

Literature and links on the subject of air pollution and health

  • www.umwelt-schweiz.ch (website of the Swiss Federal Office for the Environment BAFU containing lots of information and publications which can be ordered or downloaded)

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.

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