For several decades, many coho salmon returning to waterways around Seattle to spawn have died mysteriously following heavy rains. In some urban streams, nearly all of the coho returning from the ocean died.
It wasn’t until 2021 that scientists figured out what was behind what they called “urban runoff mortality syndrome,” and it was not until this month that federal regulators at the Environmental Protection Agency moved to do something about it.
The EPA on Nov. 2 said it would consider an August petition from the California-based Yurok Tribe and the Washington-based Port Gamble S’Klallam and Puyallup tribes, calling for a ban of the chemical 6PPD-q. It’s used in car tires to keep them from cracking and degrading, but as tires wear down, they shed particles containing the chemical into stormwater and streams. Even small amounts of 6PPD-q in a stream can cause salmon to become disoriented and die within hours, scientists have found.
The chemical has not been as big of an issue elsewhere, but officials worry it could become a problem. Oregon Attorney General Ellen Rosenblum and the attorneys general of Connecticut, Rhode Island, Vermont and Washington also submitted comments to the EPA in October supporting the petition. They said the tire-related pollution risks billions of dollars of state and federal money and decades of work spent on fish habitat and passage in the Northwest.
“The restored aquatic habitat is only as good as the water flowing through it,” they wrote.
EPA officials will spend the next year gathering information that could shape new regulations or a ban on the chemical, according to a news release. Agency officials acknowledged data showing 6PPD-q is toxic to fish, but they said there still uncertainty about how much harm the chemical is causing – to fish and potentially people, the new release said.
In Oregon, there have not been large fish die-offs attributable to the chemical, according to Shaun Clements, deputy director of the Oregon Department of Fish and Wildlife. The state’s Department of Environmental Quality will begin testing for 6PPD-q in waterways following EPA guidance, Clements said.
Any watershed receiving significant runoff from roads and highways is at risk from 6PPD-q pollution, the state attorneys general said.
The National Oceanic and Atmospheric Administration's Northwest Fisheries Science Center has determined that within a few decades, coho salmon in urban watersheds could become extinct. Coho have been the species the most sensitive to the chemical, but steelhead and trout are also susceptible, according to scientists.
On Nov. 8, two San Francisco-based nonprofit fishing groups, along with the environmental legal advocacy group Earthjustice, sued major U.S. tire manufacturers. They claim the continued use of the chemical is killing already imperiled salmon and steelhead in violation of the federal Endangered Species Act.
Chinook and steelhead runs in the Puget Sound are currently listed as threatened, as are coho runs in the lower Columbia River, Oregon Coast, southern Oregon and northern California.
Washington State University scientists successfully isolated and identified 6PPD-q in 2021 from more than 2,000 other chemicals found in Puget Sound waters during three years of testing. It is the second-most toxic chemical to aquatic species ever evaluated by EPA, according to the petition from the tribes.
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