Chemical in car tires found to kill salmon

Researchers have identified a chemical found in car tires they say is causing the deaths of salmon in urban streams in Washington state.

In a study published in the journal Science last week, University of Washington researchers said they found 6PPD-quinone, an antioxidant used to slow degradation in car tires, is lethal to coho salmon.

The mortality baffled researchers for years until testing finally turned up chemicals related to tire particles in the streams where fish were dying. Edward Kolodziej, a co-senior author of the study, said scientists were then faced with the daunting task of pinpointing the deadly chemical out of hundreds identified in road runoff, according to the university’s news service.

“Most people think that we know what chemicals are toxic and all we have to do is control the amount of those chemicals to make sure water quality is fine. But, in fact, animals are exposed to this giant chemical soup and we don’t know what many of the chemicals in it even are,” said Kolodziej, an associate professor at the University of Washington.

Even after researchers found that runoff from car tires was the cause of mortality, they were still far from identifying the offending chemical.

“Here we started with a mix of 2,000 chemicals and were able to get all the way down to this one highly toxic chemical, something that kills large fish quickly and we think is probably found on every single busy road in the world,” Kolodziej said.

They finally did find what the chemical they thought was killing the fish, but then could not match it up to any existing chemical they knew about, research scientist Zhenyu Tian told The New York Times.

“It’s almost like you have a fingerprint,” Tian said. “But you really don’t know who this is, because in your database, this fingerprint doesn’t exist.”

Tian eventually matched it to 6PPD after finding the chemical in an EPA report on human exposure to tire crumb rubber on synthetic turf fields. Finally able to isolate 6PPD-quinone, the University of Washington team found it was in fact deadly to salmon.

In a statement released Friday, 4 December, the U.S. Tire Manufacturers Association (USTMA) said it has invested tens of millions of dollars to assess the impact of tire materials on the environment. However, USTMA said 6PPD-quinone is a new chemical and that organization hopes to work with university researchers to learn more about its environmental impacts.

“The tire industry uses 6PPD because it helps tires resist degradation and cracking, which is vital for passenger safety. 6PPD has been studied, but not enough is yet known about the newly discovered degradation product, 6PPD-quinone. We are committed to collaborating with researchers at the University of Washington and other scientists to better understand this product, fill knowledge gaps, and determine next steps,” the USTMA statement read.

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