Researchers discover tire-derived chemical is poisonous to Coho salmon

TACOMA, Wash. – For decades, researchers throughout Washington and the West Coast have tried to figure out, what is killing Coho salmon, after they return from the Pacific?

Now, they know. It’s called 6PPD, a chemical compound that’s found in tires, which reacts with the environment to become 6PPD-Quinone, which is toxic to Coho.

Researchers said it’s been a long, but rewarding process for everyone involved.

“It was like relief that we finally figured something out because there’s chemicals out there that we can’t see, but then at the same time it’s also sad to figure out that this was a killer chemical,” Ed Kolodziej, a researcher and engineer with the group said.

Jen McIntyre with WSU Pullman, said the research started decades ago, when the salmon started dying by the masses in streams. She said it would be years before researcher Zhenyu Tian had a thought that would steer research in the right direction.

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“I have that inspiration this is something related to 6PPD, so it’s like you’re chasing a culprit and finally you see like all the evidence line up,” Tian, with UW Tacoma and the Center for Urban Waters said.

Now that they have these findings, where do researchers go from here? They said there is still a lot that is unknown.

“How it really ends up in the water and where it finally goes if it goes into the sediment or decomposes,” Tian said.

“Where this compound is in the environment? What happens to it? How our treatment systems can be most effective with respect to it,” Ed asked.

With the compound in tires, Jen said change won’t come overnight.

“Trying to convince the tire manufacturers that it’s worth finding a safer alternative which we know won’t be easy for them or us but it’s certainly possible,” she said.

In response to the findings, the U.S. Tire Manufacturers Association released this statement:

“The tire industry is science-driven and committed to safety and sustainability. We have invested tens of millions of dollars in peer-reviewed research with the World Business Council for Sustainable Development’s Tire Industry Project to assess the impact of tire materials on the environment, wildlife and human health, including tire and road wear particles (TRWP).

The tire industry believes in collaboration and supports efforts to improve scientific understanding of the potential impacts of TRWP.  We are reviewing the study published in Science (December 3, 2020) that suggests a link between a degradation product of 6PPD from TRWP and Coho salmon mortality. 

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.”

McIntyre said if this is affecting Coho, could it be harming other organisms, or humans?

“Many of the same pollutants can cause the same problem in humans as well and certainly there are areas where humans are exposed to these very same chemicals,” she said.

The researchers all agree, their work is far from over but, they do have a joint goal in mind.

“I’ll be happiest when we have happy Coho in urban near urban and maybe even busy roadway creeks,” Ed said.

The published study can be found here.