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13. May 2019

Most air pollution does not come from exhaust

The fine dust pollution values ​​have been rising for years. To blame: the abrasion of brakes, tires and the road. And caused by all vehicles - whether diesel, gasoline or electric cars.


Thanks to an emissions scandal, tightened EU sanctions, and imminent driving bans, the automotive industry, politics and motorists are forced to rethink. Suddenly they are there, the massive investments in electromobility. Whether Volkswagen, BMW or Mercedes: The companies outdo each other with new models, which should come on the market in the next few years. Even Porsche wants to build a sports car with an electric motor..

Nevertheless, none of it will make the air in our cities cleaner. Because it's not the nitrogen oxide or carbon dioxide emissions of diesel and gasoline engines that are the most pressing problem, but fine dust. It is blamed for diseases of the cardiovascular system, lung cancer and diabetes. Jos Lelieveld, Director at the Max Planck Institute for Chemistry even estimates that the lifetime of each individual in Germany will be shortened by 2.4 years. All vehicles produce particulate matter: gasoline, diesel and electric cars - albeit in different quantities.

Fine dust - the facts

Fine dust is subdivided into PM10 and PM2.5 according to the size of the particles, with the figure for the maximum size of the particles being in microns. The rule of thumb is: the smaller the particles are, the more harmful they are. The body can no longer excrete them via the respiratory tract, in the worst case they get into the blood. The National Academy of Sciences Leopoldina recently recommended to the Federal Government to reduce the burden of particulate matter.

Tires, brakes and road wear now produce the most fine dust

According to the Federal Environment Agency, traffic accounts for up to 19 percent (PM2.5) of particulate matter. The remainder includes industrial, waste, agriculture and household chimneys. 30 years ago, exhaust emissions were the main source of particulate matter in traffic. Up to 40 kilotons of harmful substances were produced in 1990 by trucks, cars and motorcycles. Thanks to better technology and particle filters, this number has been falling for years. The truth in spite of Dieselgate is also: When it comes to fine dust, the engines of cars have never been as clean as they are today. According to the Federal Environment Agency, only eight kilotons of particulate matter were released into our atmosphere by exhaust fumes in 2016.

The abrasion of brakes, tires and roads meanwhile amounts to almost 60 percent of the particulate matter emissions (PM2.5). For the larger PM10 particles, it is over 70 percent. This dust is created when a vehicle of any kind rolls across the road. The driving style, the width of the tires and the road condition also have an influence on this. If you brake constantly and lay too heavily on the gas, it causes more fine dust. Wide tires have more contact surface and therefore a higher abrasion. This is likely to be reinforced by the boom of SUVs. If the road is in poor condition, it also means more particles. Improve to the air quality in our cities must start at these points.

  

Technical solutions are still being tested

It's not that easy. Ralf Bertling of the Fraunhofer Institute Umsicht in Oberhausen estimates that a tire loses 1.5 kilograms in a period of three to four years. This could be prevented only by abrasion-resistant tires. According to Lars Mönch of the Federal Environmental Agency, they would be louder - too loud. "There is no metrological monitoring or limit values ​​for the abrasion of tires," says the fine dust expert.

Next is the research of the automotive industry on the brakes. A few years ago, Bosch introduced the "iDisc", a "brake disk 2.0", as the manufacturer calls it. It should cause up to 90 percent less abrasion. So far, however, it is only in the Porsche Cayenne, which is on the market since 2017. The supplier Mann + Hummel takes a completely different approach. It has developed a filter that attaches directly to the brakes and is conceivable for every vehicle, be it cars or commercial vehicles. It captures 80 percent of the particles directly during the braking process. Some manufacturers and suppliers have expressed interest, but at the moment only trials are running. "It takes two to three years to get ready for series production", estimates Patrick Löffel from Mann + Hummel.

Even electric cars do not solve the fine dust problem

But motorists themselves can reduce their particulate emissions. Lars Mönch of the Federal Environmental Agency advises driving more defensively and with as narrow tires as allowed to reduce the abrasion, but admits: "These are all measures that are manageable in the effect." There had to be a general rethinking.

He is referring to the real cause of why the proportion of brake, tire and road wear increases: The number of vehicles on German roads is steadily increasing. That's why alternative propulsion systems are not the panacea for air quality: "Electric vehicles are already significantly lower in emissions - but they do not solve the problem," says Mönch. "Only things that are not particularly popular or attractive today can really help." What he means by that is obvious: to form carpools, use public transport and travel short distances by bicycle. And the most effective method of all to avoid particulate matter: leave the car standing as often as possible.

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