TACOMA, Wash. (AP) — The 13 largest U.S. tire manufacturers are facing a lawsuit from a pair of California commercial fishing organizations that could force the companies to stop using a chemical added to almost every tire because it kills migrating salmon.

Also found in footwear, synthetic turf, and playground equipment, the rubber preservative 6PPD has been used in tires for 60 years. As tires wear, tiny particles of rubber are left behind on roads and parking lots, breaking down into a byproduct, 6PPD-quinone, that is deadly to salmon, steelhead trout, and other aquatic wildlife when rains wash it into rivers.

“This is the biggest environmental disaster that the world doesn’t quite know about yet,” said Elizabeth Forsyth, an attorney with the environmental law firm Earthjustice, which is representing the fishing groups. “It’s causing devastating impacts to threatened and endangered species.”

The Institute for Fisheries Resources and the Pacific Coast Federation of Fishermen’s Associations filed the lawsuit in U.S. District Court in San Francisco on Wednesday against Goodyear, Bridgestone, Continental, and others.

In an emailed statement, Bridgestone spokesman Steve Kinkade said the company would not comment on the lawsuit, but that it “remains committed to safety, quality, and the environment and continues to invest in researching alternative and sustainably sourced materials in our products.”

Several of the other tire makers did not immediately return emails seeking comment. The U.S. Tire Manufacturers Association, which is not named as a defendant, said in a statement last week that work is already underway to identify a chemical to replace 6PPD while still meeting federal safety standards. Forcing the companies to change too quickly would be bad for public safety and the economy, it said.

“Our members continue to research and develop alternative tire materials that ensure tire performance and do not compromise safety, consistent with our industry’s commitment to sustainability and respect for the environment,” the association said in another statement Wednesday.

The fishing organizations filed the lawsuit a week after U.S. regulators said they would review the use of 6PPD in tires in response to a petition from three West Coast Native American tribes. Coho salmon appear to be especially sensitive to the preservative; it can kill them within hours, the tribes argued.

The tribes — the Yurok in California and the Port Gamble S’Klallam and Puyallup tribes in Washington — asked the Environmental Protection Agency to prohibit 6PPD earlier this year.

The agency’s decision to grant the petition is the start of a long regulatory process that could see it banned — one of several efforts on different fronts to recover salmon populations as well as the endangered killer whales in the Pacific Northwest that depend on them.

The chemical’s effect on human health is unknown, the EPA noted.

Forsyth said that as long as 6PPD remains in tires, the companies need a federal permit allowing them to harm species that are protected under the Endangered Species Act. To do so, they would have to show that they’ve mitigated the harm to salmon to the fullest extent possible, which could mean funding stormwater improvements to keep the chemical from entering aquatic habitats.

No tire company has such a permit, the lawsuit said.

“This has been a problem that has been identified by the industry itself for more than a decade,” said Glenn Spain, the northwest regional director at the Institute for Fisheries Resources. “You can’t just sit on your thumbs and hope it will go away. It will not go away.”

The commercial fishers represented by the groups depend on the fish for their livelihood, he said.

Replacing the chemical with another that will make rubber durable without killing fish is a tall task, but one the industry can tackle, Forsyth said: “We’re the nation that figured out how to get lead out of gasoline and still have our cars run. It would shock and surprise me if we cannot make a tire that does not kill up to 100% of coho returning to their native streams.”

Salmon spend their early months or years growing and feeding in freshwater streams and estuaries, before entering the ocean to spend the next few years foraging. They then return to the streams where they were born to spawn.

The chemical’s effect on coho was noted in 2020 by scientists in Washington state, who were studying why fish populations that had been restored in the Puget Sound years earlier were struggling.

“This chemical is ubiquitous in stormwater runoff,” Forsyth said. “It’s ubiquitous in aquatic habitats and is ubiquitous at levels that can kill coho salmon and harm salmon and steelhead at very minute levels.”

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