Tire chemical tied to coho kills
Social posts this week renewed attention to 6PPD‑quinone, a chemical produced when common tire rubber wears down that has been linked to coho salmon die‑offs in urban streams (x.com). Advocacy groups urged a nationwide ban and noted a Washington state bill to curb the chemical failed recently, and they also called for removing the compound from artificial turf materials (x.com). Scientists cited in related coverage warned salmon are highly sensitive to pollutants like copper as well, highlighting multiple chemical threats in runoff that can disrupt fish behavior and survival (x.com).
A chemical formed as tires wear down and hit air is killing coho salmon in urban streams, and Washington’s latest bill to curb it stalled in the Legislature. (wdfw.wa.gov) (app.leg.wa.gov) The chemical is called 6PPD-quinone. Tire makers add 6PPD to rubber to keep tires from cracking, and when that additive reacts with ozone, it turns into 6PPD-quinone and sheds into the environment as tire particles wear off. (epa.gov) (wdfw.wa.gov) Rain does the rest. Stormwater washes tire dust from roads, parking lots, and storm drains into streams, where Washington fish officials say concentrations after heavy rains can exceed levels that are toxic to coho within hours. (epa.gov) (wdfw.wa.gov) Washington wildlife officials say researchers at the University of Washington and Washington State University identified 6PPD-quinone in 2020 as the cause of the coho die-offs long seen in urban runoff. The United States Environmental Protection Agency points to a 2021 paper in *Science* that linked coho deaths in stormwater to the compound. (wdfw.wa.gov) (epa.gov) The problem is not limited to roads. Washington’s Department of Health says crumb rubber made from recycled tires, which is used in some artificial turf fields, is also a common source of 6PPD and 6PPD-quinone, and researchers have detected both chemicals in turf fields in the United States. (doh.wa.gov) State regulators have already started a slower regulatory track. Washington enacted Senate Bill 5931 in March 2024, which put 6PPD-containing tires into the state’s Safer Products for Washington process rather than banning the chemical outright. (ncel.net) (wa-law.org) The newer proposal, House Bill 2421, would have gone further by targeting 6PPD and “regrettable substitutes” in tires, but the Legislature’s bill page listed it as sitting in House Rules as of April 12, 2026. That left advocates this week pointing to a failed push for a direct phaseout. (app.leg.wa.gov) (wa-law.org) Washington agencies are also working on runoff controls while the tire industry looks for alternatives. The Washington Department of Ecology says 6PPD is lethal to coho salmon, and recent Northwest coverage reported the agency has funded more than 20 local and regional projects and has two studies underway on chemicals in stormwater runoff from turf fields. (ecology.wa.gov) (opb.org) Scientists are widening the search beyond coho. Washington fish officials say steelhead and Chinook may also be harmed at some stormwater concentrations, and the National Oceanic and Atmospheric Administration said in 2025 that its researchers had developed a way to measure 6PPD-quinone directly in fish, shellfish, and marine mammals. (wdfw.wa.gov) (fisheries.noaa.gov) Federal researchers say many Tribes rely on salmon for food and cultural practices, and that healthy salmon runs are tied to treaty rights as well as commercial and sport fisheries. For now, the chemical remains in common tires, and the fish are still encountering it every time rain carries road dust into streams. (epa.gov) (fisheries.noaa.gov)
