On August 1, 2023, Earthjustice filed a citizen petition under Section 21 of the Toxic Substances Control Act (TSCA) asking the U.S. Environmental Protection Agency (EPA) to establish regulations prohibiting the manufacturing, processing, use, and distribution of N-(1,3-Dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD) (Chemical Abstracts Service Registry Number^® (CAS RN^®) 793-24-8) for and in tires. Earthjustice filed the petition on behalf of the Yurok Tribe, the Port Gamble S’Klallam Tribe, and the Puyallup Tribe of Indians. According to Earthjustice’s August 1, 2023, press release, “[w]hen 6PPD reacts with ground-level ozone, it breaks down into 6PPD-q -- the second most toxic chemical to aquatic species ever evaluated by the EPA.” The press release states that exposure to 6PPD-q “can kill coho salmon within hours, and the chemical is responsible for ‘urban runoff mortality syndrome,’ which kills up to 100% of coho returning to spawn in urban streams.” The Tribes contend that 6PPD in tires poses unreasonable risks to the environment, requiring EPA to regulate the chemical under TSCA.