Tire chemical kills coho

A chemical formed when tire additives break down in air and water can kill coho salmon after storms wash road runoff into streams. (epa.gov) The chemical is called 6PPD-quinone. It forms when 6PPD, an additive used in vehicle tires to slow cracking and extend tire life, reacts with ozone and then washes off roads in stormwater. (epa.gov) U.S. Environmental Protection Agency researchers say stormwater concentrations have killed coho after only a few hours of exposure. A 2021 *Science* paper first tied the compound to the long-running “urban runoff mortality syndrome” seen in Pacific Northwest streams. (epa.gov; itrcweb.org) The number cited by advocates — 41 parts per trillion, or 41 nanograms per liter — comes from research summaries that describe coho mortality at that concentration. That is roughly a few drops in an Olympic-size pool, and Washington officials say the compound ranks among the most toxic chemicals to aquatic life they track. (sciencedirect.com; opb.org) The problem is not limited to one creek or one storm. The U.S. Geological Survey says 6PPD-quinone is acutely toxic to coho salmon and has also harmed brook trout, rainbow and steelhead trout, lake trout, and white-spotted char, though often at higher concentrations. (usgs.gov) In British Columbia, Raincoast Conservation Foundation said in May 2024 that Ottawa had agreed to prioritize 6PPD for assessment under the Canadian Environmental Protection Act after a request from Raincoast, Watershed Watch Salmon Society, and Pacific Salmon Foundation through Ecojustice. Raincoast said Environment and Climate Change Canada had committed to a priorities plan by June 2025, with any regulatory intervention to come later. (raincoast.org) Canada’s federal registry now lists substances prioritized for assessment under that law, but the public materials available through the registry do not show a finished rule banning 6PPD in tires as of April 19, 2026. The current federal process is still framed around assessment and consultation. (canada.ca; canada.ca) Scientists are still working on the practical question that follows: what replaces 6PPD, or what keeps it out of streams if tires still use it. Washington state has funded stormwater retrofits and field studies, while U.S. federal agencies are testing treatment systems and screening possible alternative tire additives. (opb.org; usgs.gov) That leaves the same chain in place each rainy season: tires shed particles onto pavement, runoff carries the byproduct into creeks, and coho can die before they spawn. The policy fight in Ottawa is over whether to interrupt that chain at the tire, the road, or the storm drain. (epa.gov; vancouversun.com)