Scientists investigate risks posed by brake dust – Munich area

Imagine an average car trip across Europe. There are lots of highways, little city traffic – and always hard braking. It is easy to imagine that this creates a large amount of brake dust. You can barely see the particles because they are called ultrafine dust. The particles are about a thousand times smaller than the diameter of a human hair. However, brake dust is unhealthy for humans and the environment, but this has not yet been studied in more detail. Scientists at the German Army University in Neuberg are now involved in a research project.

The brake disc and brake caliper are mounted in a metal housing. Clean air is provided through a very fine filter. The selected driving profile is operated via the computer, which simulates the corresponding braking process. The measurement system at the Institute of Mechanical Engineering at the German Army University measures small particles created when braking. Researchers led by Thomas Adam, a professor at the Institute of Environmental Chemistry and Technology, are taking a closer look at ultrafine dust in the Ultrhas project. “There is little knowledge about this topic, and its impact may be underestimated,” says Adam.

Other institutions in Germany, Norway, Finland and Switzerland are also conducting research on the impact of ultrafine dust generated by traffic on human health and the environment. The EU-funded project, which is scheduled to last for four years, is scheduled to run until the summer of 2025. “The smaller the particles, the more dangerous they are,” says Adam. “We know from animal experiments that ultrafine dust particles can enter the bloodstream through the lungs.” The smaller it is, the deeper you breathe into it.

Until now, particles have not been a major problem in public spaces; At official roadside measuring stations, the focus has been on larger particles. In the project, the researchers are now investigating the biological and physicochemical properties of particles that originate in different transport zones. In other words, exhaust gases from diesel, gasoline and gas engines in road traffic, from ship engines and aircraft engines, as well as corrosion from brakes and overhead railway lines. Scientists in Newberg are focusing on brake dust.

Measurement campaigns were carried out by other project participants in Rostock and Kuopio in Finland. Adam and his team conducted brake tests on a high-tech brake test stand at the Institute of Mechanical Engineering in Neuberg in cooperation with the More Mobility project, which is funded by the German Army's Center for Digitization and Technology Research. The big plus point about the system: It already meets future law-compliant brake dust measurement requirements. And with Emissions Standard 7 for road traffic due to be introduced in the next few years, limits should also apply to brake dust. So far this has not been the case.

The test seat simulates an average car trip in Europe with ten different stages, explains Michael Mader, who operates the test seat. The temperature in the brake discs, which arises depending on the speed, is crucial for particle formation. It is absorbed and collected using a filter and then weighed using a particularly sensitive balance. In Adam's lab, molecules are screened for their chemical components using complex methods. Brake dust consists mainly of iron and other metals. Partners at the Helmholtz Center in Munich and at the University of Rostock are studying the biological effects of ultrafine dust. In experiments, scientists used brake dust on cultured human lung cells. They then analyzed whether cells were dying, DNA strands were breaking, or whether something was changing in metabolism. “Ultrafine dust particles are suspected to contaminate the organism and possibly cause diseases such as lung cancer,” says Adam.

Open detailed view

Investigations into the effects of brake dust are not yet complete: “The evidence is clear – you don't want to inhale metal particles,” Adam says. Ultimately, the results of all project participants must be related to each other in order to create a risk analysis regarding the most dangerous ultrafine dusts. With the results in hand, scientists then want to advise policymakers.

More stringent requirements for brake dust may be appropriate. At least Adam sees a positive development through electric mobility. Thanks to the recuperation function, in which the electric car recovers energy and brakes by taking your foot off the pedal, the brakes are used less often. But Adam also sees a need to catch up in other areas: apart from the requirement for sulfur content in fuel, there are currently no emissions limits for freight traffic.