U.S. regulators say they will review the use of a chemical used to produce nearly all tires after a petition from three West Coast Native American tribes called for a ban because it kills salmon returning from the ocean to their natal streams to spawn.

The Yurok tribe in California, the Port Gamble S’Klallam and Puyallup tribes in Washington asked the Environmental Protection Agency in August to prohibit the use of rubber preservative 6PPD in the manufacturing, use, and distribution of tires. Representatives of the tribes said it kills fish populations, contaminating the waters through storm runoff.

Washington, Oregon, Vermont, Rhode Island, and Connecticut also wrote the EPA, citing the chemical’s “unreasonable threat” to their waters and fisheries. The agency’s decision to grant the petition is the first step to banning the chemical, with tire manufacturers already looking for alternatives to 6PPD.

"We could not sit idle while 6PPD kills the fish that sustain us," Joseph L. James, chairperson of the Yurok Tribe, told The Associated Press. "This lethal toxin has no business in any salmon-bearing watershed."

Rubber preservative deadly to salmon and trout

6PPD has been used as a rubber preservative in tires for about 60 years, and is also found in footwear, synthetic turf, and playground equipment, according to the EPA. As tires wear down on roads, particles of rubber are left behind and washed into bodies of water when it rains.

The chemical has been found to be deadly to steelhead trout and salmon, which are central to the ecosystems, tribal cultures, and diets of the West Coast, the tribes wrote in the letter. For decades, the communities have fought to protect the dwindling fish population from climate change, pollution, and development that impede the fish from getting back to their spawning grounds. 

"This is a significant first step in regulating what has been a devastating chemical in the environment for decades," Elizabeth Forsyth, an attorney for Earthjustice, an environmental law firm that represents the tribes, told the AP.

The tribes said 6PPD in tires poses "unreasonable risks" to the environment and asked the agency to regulate the chemical under the Toxic Substances Control Act. The chemical impacts coho salmon, rainbow trout, steelhead trout, Chinook salmon, brook trout, and white spotted char, the tribes said. 

"These salmon and other fish have suffered dramatic decreases in population over the years," said Assistant Administrator for the Office of Chemical Safety and Pollution Prevention Michal Freedhoff in a statement. "Addressing 6PPD-quinone in the environment, and the use of its parent, 6PPD, is one way we can work to reverse this trend."

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Many salmon species are endangered or threatened

According to the tribes’ letter, many populations of salmon and steelhead trout are listed as endangered or threatened with extinction under the Endangered Species Act.

“To see 6PPD-q kill the salmon that are reared in the [tribe’s] own streams and from its own hatchery is an unconscionable slap in the face to a people who rely on salmon for their wellbeing,” said Josh Carter, the Port Gamble S’Klallam Tribe’s environmental scientist, in the letter.

The U.S. Tire Manufacturers Association said in a statement that an analysis is underway to identify alternatives to 6PPD.  The association said changing the composition of tires is "not a simple process" and could impact durability, fuel economy and other safety-related components.

“Any premature prohibition on the use of 6PPD in tires would be detrimental to public safety and the national economy,” the association said in a statement.

According to an EPA-funded study in 2020, 6PPD was found to be toxic to fish, with coho salmon appearing to be the most vulnerable to the chemical. It is unclear how the chemical impacts human health, the agency said.

Contributing: The Associated Press