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6PPD-Q and You

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine or 6PPD is a chemical used in tire manufacturing to prevent them from breaking down. Friction between tires and the road causes 6PPD to be released in dust. When exposed to ozone in the air, 6PPD undergoes a chemical reaction and becomes 6PPD-quinone, or simply 6PPD-q. This new chemical then gets into waterways where it has been proven to be extremely hazardous for marine life.

Marine die-offs beside roadways had been noticed before, but the pollutant responsible hadn’t been figured out. 6PPD-q was first discovered as that pollutant in December 2020 by scientists at the University of Washington-Tacoma and Washington State University. Coho salmon seem the most vulnerable to 6PPD-q, but it is toxic to other fish species like rainbow trout and chinook salmon. The discovery of 6PPD-q has caused a flurry of legal activity and regulation discussions.

In 2022, the EPA launched a group to research 6PPD-q and how to prevent further fish deaths. Both California and Washington have included 6PPD-q in their chemical safety programs, and Oregon has released a primary report about ways to reduce 6PPD-q runoff. Management of tire wear runoff has been included in the draft of Washington’s stormwater permits, even though 6PPD-q has not been mentioned by name. This year, the EPA released a 6PPD-q test to better assess and manage water systems.

Likewise, 6PPD-q has been the subject of multiple legal cases. The Yurok, Port Gamble S’Klallam, and Puyallup tribes petitioned the EPA to prohibit the use of 6PPD in tire manufacturing due to 6PPD-q’s effects on the salmon the tribes traditionally fish. The EPA agreed to the petition and has drawn up a plan to further research 6PPD and 6PPD-q and phase its use out of tire manufacturing. Shortly after the petition was granted, the Institute for Fisheries Resources (IFR) and the Pacific Coast Federation of Fishermen’s Associations (PCFFA) filed a joint suit against multiple tire manufacturers for their use of 6PPD, which endangers animals protected by the Endangered Species Act. Similarly, the Center for Biological Diversity sent an intent to sue letter to the California Department of Transportation, the US Department of Transportation, the Oregon Division of Federal Highway Administration, the National Marine Fisheries Services, and the Secretary of Commerce for alleged inactions related to road management, which led to 6PPD-q ending up in critical salmon habitat

The legal issues surrounding 6PPD and 6PPD-q are coming fast. Those in the tire industry need to stay abreast of the issue, while some have an opportunity to invest in things like 6PPD-q cleanup and green infrastructure that will help prevent 6PPD-q from getting to the fish in the first place.



6PPD - Washington State Department of Ecology. (n.d.). 

Dixon, S. T., & Furman, K. C. (2024, March 1). Beyond PFAS: What’s up with emerging contaminant N-(1,3-Dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD)? americanbar.org

Earthjustice. (2023, November 8). U.S. fishing groups sue tire manufacturers over 6PPD impacts on salmon, Steelhead - Earthjustice