Engineers working to tackle carcinogenic pollution from cars have developed cheap and simple devices to test the effectiveness of particle filters, which could help take toxic vehicles off roads without resorting to blanket bans. Municipalities across Europe are struggling to find ways to meet new clean air rules without having to invest billions in electric vehicle infrastructure or banning diesel vehicles altogether. Regulators also need to find inexpensive ways to measure real-world emissions without installing costly equipment. Engineers have now come up with simple, hand-held, battery-powered tools to check within minutes whether cars at low idle speeds have particle filters that work. The devices cost around 8,000 euros ($9,060), making them affordable for police and garages that do emissions inspections. The new measuring devices will start rolling out in Europe this year for mandatory tests and could help improve diesel engines' reputation after scandals over carmakers' use of illegal defeat devices to manipulate exhaust emission tests. Some German cities have banned diesel cars, primarily to limit harmful nitrogen oxide (NOx) emissions. However particulates also kill 5 million people a year globally, Andreas Mayer, director of engineering group VERT's scientific committee, told Reuters on the sidelines of the group's annual meeting. "There is a lot of toxic stuff emitted from cars, and the most toxic are particulates," Mayer said. The more than 100 million particle filters in use on European roads can, if they work properly, make vehicles' exhaust less toxic than the ambient air cars burn. "These diesel cars, if they are running through cities, are even cleaning the air because the filters are so efficient, so we must do everything in order to keep that quality during the life of the vehicle," Mayer said. The problem comes when ceramic filters crack or get plugged with soot, sometimes prompting mechanics to remove or alter them in an improper fix to boost engine power Made by a dozen European companies, the new testing devices will initially be rolled out in the Netherlands and Belgium and eventually spread to all of Europe, Mayer said. The harmful impact of NOx emissions and fine particulate matter were for years ignored by European regulators until Volkswagen was caught masking excessive pollution levels in cars it sold in the United States. The US Securities and Exchange Commission is suing Volkswagen and its former chief executive Martin Winterkorn over the scandal, accusing the company of perpetrating a "massive fraud" on US investors. The fraud caught the eye of European regulators, who had focused mainly on carbon dioxide emissions. The disparity between on-road emissions and test bench results came to light after Marc Besch, a Swiss student at West Virginia University, decided to study Volkswagen emissions for an academic paper in 2013. He noticed other carmakers used more sophisticated emissions filters. Together with colleagues he rented a VW Jetta station wagon without knowing that their findings would change the auto industry forever. Besch needed to measure the VW's pollution levels under laboratory conditions, so he turned to California's Air Resources Board (CARB), which would later help blow the whistle on the "Dieselgate" scandal. The rented Volkswagen passed the laboratory test at CARB's facility, but behaved very differently on the road, Besch said. "The Volkswagen did not show a characteristic reduction of nitrogen oxide pollution levels during highway driving," Besch told Reuters. NOx pollution drops once catalytic converters warm up, but the VW's levels were more than 30 times the legal limit, Besch's data showed. — Reuters