Car tires and brake pads produce harmful microplastics

There’s a big problem where the rubber meets the road: microplastics.

Scientists analyzed more than 500 small particles pulled from the air around three busy German highways, and found that the vast majority — 89 percent — came from vehicle tires, brake systems and roads themselves. All together, these particles are classified by the researchers as microplastics, though they include materials other than plastic.

Those particles get blown by wind and washed by rain into waterways that lead to the ocean, where the debris can harm aquatic animals and fragile ecosystems, says environmental scientist Reto Gieré of the University of Pennsylvania. He presented the findings on November 6 at the annual meeting of the Geological Society of America in Indianapolis. Previous research has estimated that about 30 percent of the volume of microplastics polluting oceans, lakes and rivers come from tire wear.

“We all want to reduce CO₂ emissions” from vehicle exhaust, Gieré says. “But you can’t stop tire abrasion.” Traffic congestion makes the problem worse. Vehicles traveling at constant speeds, without so much brake use, produced fewer particles, the researchers found.

Because some materials, including synthetic rubber, become coated in dust and other tinier bits of debris, they’re not always easy to identify. The researchers figured out what each particle was by examining each of them under a scanning electron microscope and running chemical analyses. 

“These [tire] particles are stealthy,” says John Weinstein, an environmental toxicologist at the Citadel in Charleston, S.C., who was not involved in the study.