Tiny tire particles discharge into the environment every time a vehicle brakes, accelerates, or rounds a curve. In a UN brief, geochemist Reto Gieré and colleagues aim to educate the world about this lesser-known environmental obstacle.
By now, it’s hard to overstate the link between cars and their emissions from fossil fuel combustion. But beyond the exhaust coming out of vehicle tailpipes, there’s another source from these machines that pollutes the environment every time we drive: miniscule particles from brakes and tires.
Reto Gieré, a professor in the Department of Earth and Environmental Science, and fifth-year Ph.D. candidate Jaydee Edwards.
(Images: Courtesy Reno Gieré and Jayden Edwards)
“Each time you hit the brake pedal, you remove tiny amounts of the car’s braking system because of the friction between the wheels and the brake pads. We need to do that to stop the car, but every time we do, we lose materials,” says Reto Gieré, a professor in the School of Arts & Sciences’ Earth and Environmental Science department. “The same is true for tires.”
Gieré, a geochemist, has studied road dust for the past eight years. He recently began focusing on the microplastics from tires, which are “virtually everywhere,” he says, especially prominent at stoplights or other places cars frequently stop and accelerate, as well as around curves. Once the particles mix with the overall road dust, they typically don’t stay in one place, he adds. “They are flushed off the road surface in a big rainstorm, for example, and from there, they are distributed into the environment. Once they’re in the environment, there’s practically nothing we can do to remove them.”
With this research as the backdrop, the United Nations Environment Programme (UNEP) asked Gieré and colleagues—a team that included Penn doctoral candidate Jaydee Edwards and collaborators from the German Meteorological Service, the Czech Republic’s Tomas Bata University in Zlín, and Dresden University of Technology—to write a brief about vehicle tire particles in the environment.
Among many findings, the researchers showed that typically, these tire-wear particles are no larger than 0.15 centimeters, have an elongated shape, and are covered by even smaller particles; that heavier vehicles discharge considerably more of these microplastics; and that chemical components added to tires to increase durability and maximize performance are leached into the environment.
The researchers say such outreach would be most effective if it came from a range of stakeholders, from tire manufacturers and the auto industry to research institutions, environmental organizations, educators, and the media. Tire manufacturers could go a step further, too, Gieré says. “Two of our collaborators are tire engineers. They’re working on tires that, when they get damaged, will heal again; it’s called self-healing. This will prolong the life of a tire and emit fewer particles.”
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