Particulate matter and microplastics are much-discussed risks to the environment and health. A new study by the Center for Earth System Research and Sustainability at the University of Hamburg and the Helmholtz-Zentrum Hereon has now investigated the role of tire and brake wear in the formation of urban particulate matter for the first time. The result: this abrasion alone causes 12 percent of particulate matter in Hamburg - and is the largest source of microplastics in the environment.
Anyone who lives or walks along a busy road breathes in a considerable amount of microplastics. "In Hamburg, an average of 12 percent of the particulate matter on the main roads consists of tire and brake abrasion, most of which is microplastics," explains Mailin Samland, lead author of the study and meteorology doctoral student at the Center for Earth System Research and Sustainability (CEN) at the University of Hamburg. Abrupt braking and acceleration are the main causes of microplastics entering the air - and therefore the airways. Anticipatory driving, on the other hand, reduces abrasion. Samland has now published the results in a team with the Helmholtz Center Hereon in the journal Atmospheric Environment: X.
It is well known that microplastics and particulate matter are harmful to health. But so far, discussions have focused on emissions from the exhaust - tire abrasion has been ignored. Yet dense traffic and densely built-up streets in Hamburg lead to high levels, especially on busy roads such as Max-Brauer-Allee or Stresemannstraße in Hamburg-Altona. This shows that the concentration of particulate matter in the city has so far only been recorded at certain points. The researchers were able to close the gaps with the help of a digital air quality model. The calculation model takes into account local emissions as well as emissions from the surrounding area and simulates how pollutants are distributed in the city. It also draws on weather data and calculates the mix of different vehicle types.
"This allows us to say for the entire urban area where the particulate matter and thus the microplastics are concentrated in the air," explains environmental scientist Dr. Ronny Badeke from Hereon, who believes that "the results can be transferred to other large cities. There are similar numbers of plastic particles floating in the air."
Lower EU particulate matter limits were recently adopted. This means that the air in cities must become significantly cleaner. Even these stricter values will probably not be enough for healthy air," says Mailin Samland from CEN. A fifth of this limit value is reached by microplastics alone, plus traffic exhaust fumes and other sources.
Technical article: Mailin Samland, Ronny Badeke, David Grawe, Volker Matthias (2024): Variability of aerosol particle concentrations from tire and brake wear emissions in an urban area. Atmospheric Environment X, DOI: 10.1016/j.aeaoa.2024.100304.
