Polluted air can lead to heavier pollen

Air pollution could make birch pollen more allergenic, i.e. more aggressive. This is now shown by a study by a Polish research team that was published in the specialist journal "Plos One". This could explain why there are more people with allergies in the city than in the country.

Birch trees are among the most aggressive and strongest tree pollen allergens. Most people in Europe with a pollen allergy react to it. For many, their pollen triggers allergic rhinitis and asthma. Historically, they were also commonly planted in urban residential areas for their appearance and tolerance to environmental factors.

The research team from Kraków used birch trees to study how air pollution changes the quality of tree pollen. To do this, they collected the blossoms from several trees in different places in the south-east of the country. These include parts of the city of Kraków, but also small towns and the forest.

The pollen from the birch blossoms was then examined in the laboratory. The main allergen it contains is the protein Bet v 1. Using Raman spectroscopy, the researchers discovered that the structure in the samples was different. They also found higher concentrations of the protein in the samples from the more polluted locations.

The team led by Iwona Stawoska from the Institute of Biology at the Pedagogical University in Kraków concludes that this can lead to an increase in the allergenicity of the proteins. This, in turn, would mean that allergies are also more common in desensitized individuals.

Other experts doubt their study results. “Air pollution is not good for your health. However, the effect of particulate matter on allergies is controversial," says Jeroen Buters from the ZAUM Center for Allergy and the Environment in Munich to the "Scienced Media Center". The toxicologist explains that the Bet v 1 content depends on the ripening of the pollen and the amount of the protein increases during this time.

According to Buters, the timing at which the pollen flowers are picked is crucial. “Sampling three trees per site is not enough. We collected from more than 30 trees and it was still difficult despite the larger number of samples.” Buters complains that it is unclear whether the different Bet v 1 values ​​cannot be explained by the time of sample collection.

The head of the Environmental Immunology department at the University of Augsburg, Stefanie Gilles, adds: "It is undisputed that air pollutants have a direct harmful effect on the airways of allergy sufferers." still.

However, it has been observed that allergic respiratory diseases in people in cities have been increasing for decades. Gilles also criticizes the method of the current study: The pollutant values ​​were not measured by Stawoska's team directly on the trees, but came from measuring stations several kilometers away.

"The conclusion that the differences observed in the pollen actually lead to an increased immune reaction in allergy sufferers is not valid, since no corresponding tests were carried out on patients with the pollen samples," Gilles continues.

Barbara Bohle from the Medical University of Vienna is not convinced either. "It's not new that pollution affects plants, including birch trees, and can also lead to increased production of allergens," she says. Studies on this had already been carried out in the late 1990s. Bohle heads the “Allergy Research” research group.

A connection between air pollution and higher allergenicity is suspected not only with birch pollen. For example, a study on the highly allergenic ragweed plant shows that ozone can increase the allergenicity of ragweed pollen. In addition, data show a direct influence of nitrogen dioxide on the increased allergenicity of ragweed pollen. Accordingly, this is associated with an increased risk to human health.

The Augsburg environmental doctor Stefanie Gilles explains that the average pollutant values ​​​​from the Polish study are sometimes very high. Values ​​of up to 80 micrograms per cubic meter of air would certainly occur in German cities, but would correspond more to a peak load on main traffic arteries. "When planning new green spaces in the future, care could be taken not to plant highly allergenic plants such as hazel, alder or birch in places where air pollution is high," she says. This could be taken into account in the future, especially in residential areas with high levels of air pollution near busy roads.

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