Pollutants: The air is getting cleaner, but the risk of death remains unchanged

Decreasing concentrations of pollutants in the air do not automatically lead to a lower risk of death. This is the result of an international study led by the Helmholtz Center Munich. Data from 380 cities around the world were evaluated. Air pollution not only endangers millions of people. It also affects agriculture, as the World Meteorological Organization (WMO) emphasizes in a recent report.

For the city study, which was published in the journal “The Lancet – Planetary Health”, values ​​of fine dust and nitrogen dioxide (NO₂). Numerous studies have shown the harmful effects of air pollutants. Fine dust is absorbed in the lungs and can trigger inflammatory reactions in the body. This promotes, among other things, arteriosclerosis and thus a precursor to heart attacks and strokes.

Not all air pollution is caused directly by humans – desert dust and emissions from forest fires, for example. Pollutants caused by humans are mainly due to the use of fossil fuels, and fine dust from tire and brake wear also poses a health risk.

According to the researchers, the concentration of these pollutants in the air in the cities studied decreased between 1995 and 2016. The risk of fatal cardiovascular and respiratory diseases associated with particulate matter and NO₂ However, it was said that the figure had not fallen significantly.

There could be various reasons for this. On the one hand, the population in many regions is getting older and older people have more pre-existing health problems than younger people, said the study's lead author, Maximilian Schwarz. On the other hand, changes in the origin and composition of pollutants could play a role.

More than 4.5 million dead

According to WMO, air pollution causes More than 4.5 million premature deaths every year and high economic and ecological costs. “The chemicals that cause air quality problems are usually emitted together with greenhouse gases,” reports the WMO. Pollutants such as nitrogen and sulphur compounds or ozone can settle on the earth's surface and pollute the environment.

Reports from China and India suggest that particulate matter can be reduced by 15 percent during harvesting in particularly polluted areas. Among other things, particulate matter deposits result in less sunlight on plant leaves.

Agriculture contributes to air pollution because fine dust is produced when fields are burned, fertilizers are used, and manure is stored and used.

In Europe and China, the air quality was better last year than the long-term average, the WMO reported. In contrast, forest fires in North America caused particularly bad air quality there.

Among other things, the WMO compared results from fine dust measurements by the European Earth observation program Copernicus and the US space agency NASA with the average for the years 2003 to 2023.

It refers to fine dust with an aerodynamic diameter of less than 2.5 micrometers (PM2.5). This is dangerous because the fine particles penetrate deep into the respiratory tract, remain there longer and can cause lasting damage to the lungs.

The city analysis is an epidemiological study: it determines the statistical connection between risk factors such as particulate matter pollution and health effects such as cardiovascular disease. By comparing groups that are exposed to the suspected cause to different degrees, well-founded assumptions about such connections can be derived.

Epidemiological studies indicate correlations – not necessarily causalities, so they do not say anything about causal relationships. The result is a statistical estimate, not an exact figure for clinically identified deaths. The actual value can be higher or lower.