What Is 6PPD, and Why Does It Matter for Salmon?
Vehicle tires contain 6PPD to keep them from breaking down through reactions with ozone and other reactive oxygen species in the air, the EPA says, and when 6PPD reacts with ozone it forms 6PPD-quinone. Tires wear down through contact with roads and release particles, and when it rains, stormwater from parking lots and streets washes those particles into streams and other water bodies, where aquatic life can be exposed.
The EPA says available information indicates 6PPD-quinone is toxic enough to quickly kill some fish. A 2021 publication in the journal Science linked coho salmon deaths to 6PPD-quinone in stormwater, with concentrations found to be lethal to coho after exposures lasting only a few hours, and later work identified some other fish species as vulnerable. For people, the EPA says limited information is available on the human health effects of 6PPD-quinone.
In 2024 the EPA developed an agency-wide action plan. It has developed final screening values for 6PPD-quinone and 6PPD to protect sensitive salmon and other aquatic life and a draft laboratory method for detecting 6PPD-quinone in surface water and stormwater, and it published an Advance Notice of Proposed Rulemaking on 6PPD and 6PPD-quinone in response to a petition from the Yurok Tribe, the Port Gamble S’Klallam Tribe and the Puyallup Tribe of Indians.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Government sourceThe EPA says vehicle tires contain 6PPD to prevent them breaking down through reactions with ozone, and that when 6PPD reacts with ozone in the air it forms 6PPD-quinone. US EPA ↗
- Government sourceThe EPA says tire wear particles are washed by stormwater from parking lots and streets into streams and other water bodies, where aquatic organisms can be exposed to 6PPD-quinone. US EPA ↗
- StudyThe EPA says a 2021 publication in Science linked coho salmon death to 6PPD-quinone in stormwater, with concentrations lethal to coho following exposures of only a few hours. US EPA ↗
- Government sourceThe EPA says available information indicates 6PPD-quinone is toxic enough to quickly kill some fish, and that limited information is available on its human health effects. US EPA ↗
- Regulatory filingThe EPA says it developed an agency-wide action plan in 2024 and final screening values for 6PPD-quinone and 6PPD to protect sensitive salmon and other aquatic life. US EPA ↗
- Regulatory filingThe EPA published an Advance Notice of Proposed Rulemaking for 6PPD and 6PPD-quinone in response to a petition from the Yurok Tribe, the Port Gamble S’Klallam Tribe and the Puyallup Tribe of Indians. US EPA ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.