EcoNews Report Toxic Tires Killing Coho

Adult coho salmon in Scott Creek, Santa Cruz County, California | Morgan Bond, NMFS Southwest Fisheries Science Center

The EcoNews Report talks with guest Warner Chabot, ED of the San Francisco Estuary Institute, who gives us the scoop on breaking research into a toxic chemical from tires that is killing coho salmon at alarming rates. This research further emphasizes the importance of protecting the remaining coho salmon populations that are struggling to survive in tributaries of the South Fork Eel River. Some of these tributaries, like Indian or Hollow Tree Creeks are not adjacent to frequently traveled roads and may be key to protecting this core population of Southern Oregon Northern California Coho.

Decades of efforts to save the dwindling populations of salmon on the Pacific Coast have unfortunately been unsuccessful in many regions, particularly urban settings. It’s as if scientists and activists have been missing a leading cause of salmonid decline, some silent killer in the ecosystem.

New research from the University of Washington and published in the journal Science may have identified the missing piece of the puzzle. This excellent scientific detective work lead to the discovery of a toxic byproduct from tires, 6PPD-quinone, a compound that forms when a tire preservative called 6PPD reacts with ozone gas. The transformed 6PPD-quinone has proven to be extremely toxic to coho salmon in lab tests, and degrades very slowly. This extremely lethal substance has now been identified in Bay Area stormwater, and is believed to be a leading cause of coho salmon mortality.

While this all sounds like very bad news, it is actually quite exciting. This discovery gives us an opportunity to make significant headway in protecting coho (and likely other species affected by this toxic contaminant) by addressing a single source of pollution.

We already knew that tire rubber posed a threat to aquatic life. A 2019 study by the San Francisco Estuary Institute found that nearly half of the seven trillion microplastic particles in urban stormwater flowing through the S.F. Bay could be linked to tire wear. And in 2018 the California Stormwater Quality Association began petitioning the Department of Toxic Substance Control (DTSC) to act on water pollution caused by zinc, another harmful chemical found in tires.

Understanding more about how salmon habitat is degraded in urban environments makes it all the more important to protect habitat in roadless or less frequently traveled areas like some tributaries of the Eel River.

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