Cars Now Release More Pollution From Their Tires Than Their Tailpipes, Analysis Shows

Tire change for the summer
A new study found tire wear now emits nearly 2,000 times more particulate matter than vehicle tailpipes. Wolfgang Kumm / Picture Alliance / Getty Images

The particulate pollution from car tires is nearly 2,000 times worse than that from vehicle exhaust pipes. 

That’s the surprising finding from the second analysis of the topic conducted by the independent emissions-testing group Emissions Analytics, which assessed the emissions from both tailpipes and tire wear under “normal” driving conditions. 

“Tyres are rapidly eclipsing the tailpipe as a major source of emissions from vehicles,” Nick Molden of Emissions Analytics told The Guardian. “Tailpipes are now so clean for pollutants that, if you were starting out afresh, you wouldn’t even bother regulating them.”

The new tests built on a 2020 report from the company finding that tire wear emissions were more than 1,000 times greater than tailpipe emissions under “worst case scenario” aggressive but legal driving. The first tests used a 2011 Volkswagen Golf, driving it 320 kilometers (approximately 199 miles) at high road speeds and carrying a maximum load. The latest tests looked at 14 tire brands applied to a Mercedes C-Class driven at normal speeds with only a driver in the car, in order to simulate “normal” conditions. The company found that under these normal conditions, the tires actually emitted around 1,850 times more pollution than the tailpipes. 

The reason for this discrepancy is partly a sign of progress. Tailpipe emissions have declined due to regulations and more effective filters. At the same time, vehicles are getting heavier and more powerful. Further, tire emissions are entirely unregulated, and this is a growing cause for concern. Two recent studies found that microplastic and nanoplastic particles from tire pollution were likely harming freshwater and estuary ecosystems. An earlier study calculated that tires released 1.5 million metric tons of particles into the U.S. environment annually and estimated that tire particles accounted for five to 10 percent of ocean plastic pollution. 

The Emissions Analytics studies indicate that particulate matter from tires could be contributing to air pollution as well. They revealed that tires release more than one trillion ultrafine particles per kilometer, The Guardian reported. These are particles that are smaller than 23 nanometers and represent a potential health hazard. 

“Growing scientific evidence suggests that these ultrafine particles more easily enter the human bloodstream and lungs, and cross into the brain,” Emissions Analytics wrote. 

Further tests also revealed the hundreds of chemicals in 250 tire brands, according to The Guardian. Molden said many of the chemicals were carcinogenic. All of this provides an opportunity for greater regulation. 

“You could do a lot by eliminating the most toxic tyres,” Molden told The Guardian. “It’s not about stopping people driving, or having to invent completely different new tyres. If you could eliminate the worst half, and maybe bring them in line with the best in class, you can make a massive difference. But at the moment, there’s no regulatory tool, there’s no surveillance.”

One concern is that battery electric vehicles (BEVs) could be responsible for more tire tread pollution because of their greater weight. However, Dr. James Tate of the University of Leeds’ Institute for Transport Studies in the UK told The Guardian that this was changing. 

“[I]t is very important to note that BEVs are becoming lighter very fast,” he said. “By 2024-25 we expect BEVs and [fossil-fuelled] city cars will have comparable weights. Only high-end, large BEVs with high capacity batteries will weigh more.”

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