Tire Particle Microplastic Pollution Threatens Water SuppliesTire Particle Microplastic Pollution Threatens Water Supplies

As combustion pollution diminishes, there is new focus on the rubber particles from tires.

Dan Carney, Senior Editor

September 9, 2022

3 Min Read
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Image courtesy of Goodyear Tire & Rubber Co.

“Pollution,” in an automotive context, is normally associated with the smog-forming emissions from combustion engines that the Environmental Protection Agency terms “criteria emissions.” Another sort of pollution is particulate matter, the partially burned chunks of carbon that sweep out of the combustion chamber before they can be completely oxidized.

Particulate matter is barely a concern from modern gasoline engines, but it remains a significant hurdle for diesels, which is why compression-ignition vehicles employ particulate traps to prevent the release of this kind of pollution.

Researchers are finding that in an environment where combustion engines now release very little particulate matter, another source becomes prominent: tires. The friction between soft tire rubber and abrasive road surfaces creates Tire and Road Wear Particles (TRWP), which are a 50/50 mixture of tire tread fragments and road surface elements, according to the European Tyre & Rubber Manufacturers’ Association (ETRMA).

Considering the near-total elimination of particulate emissions from combustion engines, it is no surprise to learn that tires now contribute 1,850 times more particle pollution than engines do, according to research by the British firm Emission Analytics. The company’s report finds:

Related:Earth Day-Friendly Tires Made Using Recycled Water Bottles

“The fundamental trends that drive this ratio are: tailpipe particulate emissions are much lower on new cars, and tire wear emissions increase with vehicle mass and aggressiveness of driving style.  Tailpipe emissions are falling over time, as exhaust filters become more efficient and with the prospect of extending the measurement of particulates under the potential future Euro 7 regulation, while tire wear emissions are rising as vehicles become heavier and added power and torque is placed at the driver’s disposal.  On current trends, the ratio may well continue to increase.”

It is important to minimize or contain TRWP pollution, because some of these microplastics find their way into waterways, according to the ERTMA. “The study indicates that up to 5 percent of TRWP released may reach the estuaries and that the most important factors affecting the transportation of the TRWP to the estuary are their diameter and density,” the association said in a release on the topic. “The generation of TRWP is influenced by a variety of external factors including, but not limited to tire design. These include vehicle characteristics, road surface, weather, road topology and driving behavior.” 

At least this pollution doesn’t seem to get in the air as well as the water. The Tire Industry Project found that TRWP is a minor contributor to airborne particulate matter in three different cities studied. According to University of Applied Sciences and Arts Northwestern Switzerland physics professor Martin Fierz, tire particles are too big to hang in the air persistently or to be inhaled deeply into people’s lungs.

Related:Sensata Tire Tread Depth Sensor Automatically Warns of Worn Tires

In a Twitter thread commenting on this issue, Fierz explained that “Particles are not all identical. They have different sizes, different shapes, different chemical compositions - so some particles behave very differently than others."

The large chunks pose less risk of being inhaled, he continued. “Very large particles, bigger than about 10 micrometers, won't be inhaled deeply in our body, so they don't do much harm,” he said. “They are basically cleared out the next time you wipe your nose.”

“By far most of the tire wear particles are very large, so irrelevant for human health - we don't inhale them,” said Fierz. Because of this, it is the matter of tire microplastics getting into the water supply that is the more serious concern, he said.

About the Author

Dan Carney

Senior Editor, Design News

Dan’s coverage of the auto industry over three decades has taken him to the racetracks, automotive engineering centers, vehicle simulators, wind tunnels, and crash-test labs of the world.

A member of the North American Car, Truck, and Utility of the Year jury, Dan also contributes car reviews to Popular Science magazine, serves on the International Engine of the Year jury, and has judged the collegiate Formula SAE competition.

Dan is a winner of the International Motor Press Association's Ken Purdy Award for automotive writing, as well as the National Motorsports Press Association's award for magazine writing and the Washington Automotive Press Association's Golden Quill award.

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He has held a Sports Car Club of America racing license since 1991, is an SCCA National race winner, two-time SCCA Runoffs competitor in Formula F, and an Old Dominion Region Driver of the Year award winner. Co-drove a Ford Focus 1.0-liter EcoBoost to 16 Federation Internationale de l’Automobile-accredited world speed records over distances from just under 1km to over 4,104km at the CERAM test circuit in Mortefontaine, France.

He was also a longtime contributor to the Society of Automotive Engineers' Automotive Engineering International magazine.

He specializes in analyzing technical developments, particularly in the areas of motorsports, efficiency, and safety.

He has been published in The New York Times, NBC News, Motor Trend, Popular Mechanics, The Washington Post, Hagerty, AutoTrader.com, Maxim, RaceCar Engineering, AutoWeek, Virginia Living, and others.

Dan has authored books on the Honda S2000 and Dodge Viper sports cars and contributed automotive content to the consumer finance book, Fight For Your Money.

He is a member and past president of the Washington Automotive Press Association and is a member of the Society of Automotive Engineers

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