The parts of your tires that get left on the road as you drive your car are a huge source of microplastic pollution, and some of it is toxic.
Now researchers at San Diego State University (SDSU) have identified 60 chemical compounds in tires that end up in tire waste. And half of them had never been associated with tires before.
“We did find that some of the compounds that previously weren’t associated with tires may be toxic,” said Maggie Stack, a research specialist at SDSU.
Stack is the lead author of a paper, based on the research, that appeared in the journal Environmental Pollution.
Tire waste is generated constantly as tiny particles get worn off the tires where the rubber meets the road. Those particles, typically measured in microns, are swept into the watershed where they enter streams and ultimately the ocean.
Three years ago, researchers in the state of Washington identified a chemical, derived from a common preservative used in tires. They found it was being washed into fresh water streams, with other tire waste, and it was killing salmon before they could spawn.
The SDSU researchers also found that one, called 6PPD. They point out that some of these chemicals become more dangerous when they are exposed to the elements. The 6PPD example became toxic to salmon when the environment converted it to 6PPD-quinone.
“Under natural conditions sunlight can convert those compounds that leach out of the particles into new compounds, or transformation products, and those can be even more toxic than the originals,” said Natalie Mladenov, a professor of environmental engineering at SDSU who is involved with the research.
The researchers said there is a growing awareness of tire wear as a source of microplastics. It’s something that didn’t used to occur to many people because this tire waste comes in pieces that are barely visible to the naked eye.
“Tires can be as little as 20% natural rubber and then the rest is synthetic materials – synthetic rubber and other plastic polymers. So it is truly a source of microplastics to the environment,” Mladenov said.
The research also showed that the micro size of these tire particles makes them even better at leaching chemicals once they’re in water.
“So we were finding that smaller particles are potentially more toxic and more dangerous than larger particles,” Stack said.
Mladenov and Stack said particles from tire wear is a source of pollution that is not regulated by the government. At least not yet.
The SDSU study was funded by the CSU Council on Ocean Affairs, Science and Technology.
