Some emissions from tires and brakes can be much worse than exhaust

Sven Gustafson

Governments in China, Europe and the U.S. have focused for years on limiting emissions from vehicles, but a new report from across the pond finds that airborne particulate pollution from tire wear and tear can be more than 1,000 times worse than what comes out of a tailpipe, depending on what substances are being measured.

The findings come courtesy of British emissions and fuel-economy testing outfit Emissions Analytics, and it also accounts for harmful particulate matter generated by worn brakes. The organization says the problem is being exacerbated by the increasing popularity of large trucks and SUVs and growing demand for heavier electric vehicles, and pollution from worn tires and brakes is completely unregulated, unlike tailpipe emissions.

Emissions Analytics said it performed “initial tire wear testing” on a popular family hatchback — it didn’t say which one — equipped with brand-new and properly inflated tires. It found the car emitted 5.8 grams of what it calls non-exhaust emissions, or NEE, per kilometer traveled. That’s almost 1,289 times as high as the exhaust limit of 4.5 milligrams per km driven under European regulation.

The amount of NEE emissions would likely be even higher, the researchers note, if the tires were under-inflated, if the car was wearing budget tires or the car was traveling on rough roads, like the potholed moonscapes found in certain states here in the U.S. (cough cough, Michigan).

“It’s time to consider not just what comes out of a car’s exhaust pipe but particle pollution from tire and brake wear,” said Richard Lofthouse, Emission Analytics’ senior researcher. He added, “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 are a very serious problem.”

The findings follow a similar recent study out of England, which found that metal particles from worn brake pads comprised up to 20% of traffic-related particle pollution and had similar effects to diesel exhaust particulates in causing inflammation and airway infections and other respiratory complications. In 2017, researchers at the Georgia Institute of Technology found that fine metals emitted from brakes and tires combine with acidic sulfate in the atmosphere to produce a toxic, soluble aerosol. As the lead researcher in the former study said, “There is no such thing as a zero-emissions vehicle.”

Emissions Analytics CEO Nick Molden said the results point to “an almost complete black hole of consumer information” and out-of-date regulations that limit themselves to exhaust emissions. In the meantime, he suggests fitting vehicles with higher-quality tires and inflating them properly as a way to keep non-exhaust emissions limited. Longer-term, he said the auto industry may need to find ways to lower the weight of vehicles.

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