Study Suggests Tires Create More Pollution Than Exhaust Emissions

Anyone who’s laid a substantial amount of rubber in a local parking lot will tell you that the scent emitted doesn’t smell particularly healthy for the environment (burnt clutch smell is even less appealing — don’t ask how I know). And while the typical driver doesn’t burn through tires via successive smoke shows, regular road use effectively does the same thing over a much longer timeline — and a new study claims it’s up to 1,000 times worse than what actually comes out of a vehicle’s exhaust system.

The report, penned by UK-based independent research firm Emissions Analytics, has circulated within the media for a few days and claims that pollution stemming from tire and brake wear is a growing problem. With European lawmakers clamping down on tailpipe emissions, the firm suggests “non-exhaust emissions” will be the next big regulatory challenge.

From Emissions Analytics:

Non-exhaust emissions (NEE) are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage. No legislation is in place to limit or reduce NEE, but they cause a great deal of concern for air quality.

NEEs are currently believed to constitute the majority of primary particulate matter from road transport, 60 percent of PM2.5 and 73 percent of PM10 — and in its 2019 report ‘Non-Exhaust Emissions from Road Traffic’ by the UK Government’s Air Quality Expert Group (AQEG), it recommended that NEE are immediately recognised as a source of ambient concentrations of airborne particulate matter, even for vehicles with zero exhaust emissions of particles — such as EVs.

While the data seems legitimate, it should be said that the particulate matter that’s causing alarm likely doesn’t contribute to climate change. The Environmental Protection Agency (EPA), however, has faulted PM2.5 and PM10 for posing health risks, as both are easily inhaled.

As for the role of electric vehicles, Emissions Analytics cites them as part of the problem. Despite shifting their emissions to the nearest power station, added battery weight means EVs tend to be heavier than a similarly sized internal combustion vehicles. Weight turns out to be one of the best predictors of how much non-exhaust emissions an automobile will emit. That led analysts to similarly point to the crossover trend, which has also pushed consumers into heavier vehicles.

For testing purposes, Emissions Analytics used a “popular family hatchback running on brand new, correctly inflated tyres.” It found the car emitted 5.8 grams per kilometer of particulate matter vs the regulated exhaust emission limit of 4.5 milligrams per kilometer. It plans on doing additional testing moving forward, claiming that it has uncovered a serious oversight in the market’s regulatory activities.

“It’s time to consider not just what comes out of a car’s exhaust pipe but particle pollution from tyre and brake wear. Our initial tests reveal that there can be a shocking amount of particle pollution from tyres — 1,000 times worse than emissions from a car’s exhaust,” Richard Lofthouse, Senior Researcher at Emissions Analytics, stated. “What is even more frightening is that while exhaust emissions have been tightly regulated for many years, tyre 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.”

Another issue was the prevalence of cheap rubber, which have a tendency to create more airborne particles than something with a little more grip. However, much of this can be mitigated by where and how you drive. Putting more heat into the tires and brakes translates into worsened emissions, but there are more ways to do that than simply treating nearby roads as your own personal racetrack. Heavier vehicles with larger tires will emit more NEE by default and EVs with aggressive regenerative braking settings could nudge up the parts per million over something with a little less rolling resistance.

Previous studies would seem to indicate that non-exhaust emissions are a larger issue in an urban environment. In addition to there being more people to inhale said particulate matter, higher density traffic has a tendency to kick it up into the air and channel it into residential areas. Meanwhile, rural settings will see more particulate settling by the roadside, far from the places people actually live.

We’ve reached out to Emissions Analytics to gain some insight into the methodology used for testing and will update this article accordingly.

[Image: FCA]