Airborne outdoor allergens and air pollutants

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Introduction
01 Cancer
02 Ozone
03 Urban air
04 Air pollutants
05 Blue-green algae
06 Water mutagens
07 Contamination
08 Chernobyl
09 Radon
10 Medical geology
11 Renal hazards
12 Organohalogens
13 Estrogens
14 Food hazards
15 Mycotoxins
16 Poisoning
17 Genetics
18 Risk

Ordering

(Excerpt from Chapter 4)

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Allergy

In the beginning of May each year many schoolchildren in Nordic countries suffers from a stuffy nose with sneezing, itching eyes and often tiredness. Their ability to concentrate on school work may be reduced for several weeks. The same symptoms are seen among the adult population, which may affect their work and leisure time. The reason is that the birch trees, numerous in Nordic countries, are blossoming. The trees send pollen grains into the air, and the pollens can be carried long distances by the winds and affect allergic people even far away. Some people even get symptoms of asthma, which can result in visits to emergency rooms.

Allergic rhinitis is known from the medical literature since the beginning of the 19th century, but for a century and a half it has been a disease restricted to a very small portion of the population. Nowadays, and this is a new trend during the last three decades or so, an increasing number of people are being affected by allergy to pollens as well as to other allergens. The increase has occurred during a relatively short period of time, which tells us that factors in our environment must be mainly responsible. It has been proposed that the concentration of the population to big cities, with increased exposure to air pollutants, is a risk factor for induction of allergy. There is indeed evidence supporting the view that exposure to air pollutants involves a significant risk of developing allergy, but there are also conflicting findings. Further studies are needed to provide an answer to the question of whether exposure to air pollutants is a major risk factor for sensitization and induction of allergy, i.e. that normal individuals turn allergic.

But on the other hand, once people have acquired asthma or other airway diseases, it is quite clear that exposure to air pollutants affects their respiratory health. These negative health effects are seen even upon exposure to moderate levels of air pollutants and have turned out to be a serious threat to public health in urban environments. Furthermore, recent human studies in exposure chambers suggest that air pollutants, such as nitrogen dioxide and ozone, besides exerting direct irritating effects on the airways, can also amplify the allergic reactions in the nose and bronchi.

The ongoing increase of prevalence and morbidity in allergic diseases constitutes a challenge for environmental medicine. There are good reasons to assume that the trend can be changed with a better knowledge of how allergic sensitization occurs and how environmental factors may influence the allergic reaction. And this task can only be fulfilled trough joint efforts by scientists in different fields, i.e. allergists, epidemiologists, immunologists, palynologists and chemists.

This chapter will hopefully contribute to a discussion of how the trend involving an ongoing increase of allergies can be changed, with the focus on two environmental factors, namely airborne outdoor allergens and air pollution.

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Gunnar Bylin qualified as a physician at Karolinska Institutet, Stockholm, in 1969. He gained his doctor's degree in 1987 on a thesis entitled "On lung function in asthma - variability, and effects of an air pollutant" and was promoted to assistant professor at Karolinska Institutet in 1995. His research focuses on the effects of air pollutants on the respiratory system, which are studied in controlled human exposure experiments. He has worked at the Department of Respiratory and Allergic Diseases, Huddinge University Hospital, since 1978.