With returns from tightening tailpipe emissions laws diminishing by the year, it may be time to look elsewhere for ways to reduce transportation-generated air pollution. We may already have some idea of where to look, too, as a Britain-based emissions testing group has identified a previously unsuspected culprit for modern air quality woes: Tires.
This past Friday, Emissions Analytics released the results of an experiment wherein it tested "a popular family hatchback running on brand new, correctly inflated tires" to see how much "non-exhaust [particulate] emissions," abbreviated NEEs, the car generated. It concluded that wear on the vehicle's tires, brakes, and the road surface produced 5.8 grams of NEE particulates per kilometer driven, which is 1,289 times the 0.0045 grams-per-kilometer limit for passenger vehicle exhaust particulates under current Euro 6d emissions standards. This test's results may yet be conservative compared to real-world driving conditions, as cheap or under-inflated tires, rough road surfaces, and heavy vehicles are thought to increase NEE production.
The British government's Air Quality Expert Group attributes up to 73 percent of PM10 emissions—particles smaller than 10 microns—generated by transportation to NEEs, and that proportion may only increase with the popularity of heavy vehicles such as trucks, SUVs, and electric cars. Decaying infrastructure in some parts of the western world, especially the United States, serve only to highlight how severe the presently unregulated NEE pollution problem may be.
"It's time to consider not just what comes out of a car's exhaust pipe but particle pollution from tire and brake wear," declared Richard Lofthouse, a senior researcher at Emissions Analytics. "Our initial tests reveal that there can be a shocking amount of particle pollution from tires—1,000 times worse than emissions from a car's exhaust. What is even more frightening is that while exhaust emissions have been tightly regulated for many years, tire wear is totally unregulated—and with the increasing growth in sales of heavier SUVs and battery-powered electric cars, non-exhaust emissions (NEE) are a very serious problem."