By now you're probably aware that the world is inundated by microplastics — defined as plastic particles that measure smaller than 5 millimeters — with the tiny bits showing up everywhere, including the world's lakes, oceans, tap water and even in fish and shellfish. Scientists from all across the globe are studying the causes and effects of the proliferation these tiny plastic bits, and a recent study led by the San Francisco Estuary Institute and the 5 Gyres Institute identified an automotive-related link: tire dust.
Among other sources, the researchers measured microparticles and microplastics in stormwater from 12 small tributaries in the San Francisco area. "Nearly half of the particles from field samples were black fragments that had a distinctive rubbery texture when handled with tweezers," according to the study's executive summary, adding that "one potential source of these particles is vehicle tire wear."
Tires are made up of a lot of different compounds, including both natural and synthetic rubber, but also, according to the Los Angeles Times, flame retardants and plasticizers. The little worn-off tire fragments are also likely to pick up "fossil-fuel-associated compounds", according to the Times, before washing away off of the roads and into our water supply.
"That makes all that driving we do something to think about, not just in the Bay Area, but any setting where there are cars," said Rebecca Sutton, an estuary scientist and the study’s lead author.