Which fine dust is particularly harmful

Berlin

The fine dust produced in metropolitan areas causes more oxidative stress in our cells. (Image: ArminStautBerlin / iStock)

Certain types of particulate matter can be more harmful than others. As researchers show in a current study, not only the amount and particle size of the fine dust are decisive, but also the oxidative potential – a measure of how strongly the respective fine dust particles trigger oxidative stress and inflammatory reactions in the body. In addition, the team modeled the fine dust distribution in Europe. Accordingly, although a lot of fine dust is produced in rural areas, it is less harmful than fine dust in urban areas because of its lower oxidative potential.

Air pollution with fine dust is estimated to be responsible for several million deaths each year and is one of the top five health risk factors worldwide. Particle size is one of the deciding factors for the dangerousness of fine dust: the smaller the particles, the deeper they can penetrate the tissues of the body. For particulate matter measurements and for statutory regulations, the particle size and the amount of particulate matter have thus far been taken into account. How exactly fine dust causes damage in the body is not yet fully understood. A likely mechanism is that fine dust particles in the cells of the human respiratory system cause oxidative stress and cause inflammation, which increases the risk of cardiovascular and lung diseases.

Health risk from oxidative stress

Researchers working with Kaspar Dällenbach from the Paul Scherrer Institute in Switzerland have now analyzed this so-called oxidative potential of different types of fine dust. “We were interested in two main points in the study,” says Dällenbach. “Firstly, which sources in Europe are responsible for the so-called oxidative potential of fine dust, and secondly, whether the health risk of fine dust is caused by its oxidative potential.” In order to assess the possible health risk from the oxidative potential of fine dust, the researchers placed cells took fine dust samples from the human respiratory tract and checked their biological reaction. When the cells are under stress, they emit a signal substance for the immune system, which sets off inflammatory reactions in the body.

The analyzes confirmed that fine dust with an increased oxidative potential intensifies the inflammatory reaction of the cells. The causal connection between the oxidative potential and a general health hazard has still not been clearly established, according to Dällenbach. “But the study is another clear indication that this connection actually exists.”

Anthropogenic fine dust is particularly harmful

Using air samples from Switzerland, the researchers analyzed which fine dust sources cause emissions with a particularly high oxidative potential. In addition, they modeled for all of Europe, where the highest particulate matter pollution in terms of mass and oxidative potential is. There were considerable differences: The largest mass fraction of fine dust is made up of mineral dust and so-called secondary inorganic aerosols such as ammonium nitrate and sulfate. These arise, for example, in agriculture. Both types of fine dust are mainly released in rural areas.

The fine dust types with the highest oxidative potential, on the other hand, are, on the one hand, what are known as secondary organic aerosols, which are released when biomass is burned, for example, and, on the other hand, metal emissions that arise in road traffic, for example through brake wear. These particularly harmful emissions occur primarily in densely populated areas. “Our results show that the oxidative potential of fine dust and the amount of fine dust are not determined by the same sources,” emphasizes Dällenbach.

Possible impact on political decisions

This finding could have implications for future policy measures to reduce particulate matter. In a comment on the study published in “Nature”, Rodney Weber from the Georgia Institute of Technology in Atlanta writes that, if the particulate matter is considered, it would be natural to focus on agricultural emissions. “Dällenbach and colleagues show, however, that these inorganic salts have a low oxidative potential and are therefore less of a concern for human health. Any measures to protect people from aerosols will be very different, depending on which property of the particles – mass concentration or oxidative potential – is used as a basis for development. “

Before the new findings can actually provide a basis for political decisions, however, it must be clarified more precisely whether the oxidative potential is actually a main factor for the harmful effects. Stefan Reis from the Center for Ecology and Hydrology in Edinburgh comments: “If further toxicological studies confirm the oxidation potential as an effective environmental medical indicator, the current study can make an important contribution to this, especially fine dust sources such as tire and brake abrasion, and to move the relevance of organic particulate matter components into the research focus. The results presented could thus lead to the development of more efficient reduction strategies and initiate an important discussion on the re-evaluation of the established indicators for the health effects of fine dust pollution. “

Source: Kaspar Dällenbach (Paul Scherrer Institute, Villingen, Switzerland) et al., Nature, doi: 10.1038 / s41586-020-2902-8

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