The U.S. Environmental Protection Agency on Nov. 2 granted a petition by environmental advocates and three tribes to address the chemical 6PPD used in tire production because of the possible negative impact on salmon habitats through pavement stormwater runoff. The decision sets the stage for the agency to take steps to better understand potential risks associated with the chemical, especially regarding groundwater pollution and even regarding humans, as well as the need for regulation.

The chemical is widely used in tire and other rubber product manufacturing. When tire particles wear off during use, 6PPD reacts with ozone in the air to form 6PPD-quinone, which then is washed into waterways as stormwater runoff from streets and parking lots, exposing aquatic organisms to the chemical.

 That’s a problem, according to environmental nonprofit Earthjustice, which submitted the petition in August on behalf of the Yurok Tribe, Port Gamble S’Kallam Tribe and Puyallup Tribe of Indians. The group says 6PPD-quinone is “the second most toxic chemical to aquatic species ever evaluated.”  

The petition asks EPA to prohibit the use of 6PPD in tires, used to prevent degradation and cracking of rubber compounds, according to the U.S. Tire Manufacturers Association. The reaction that results in 6PPD-quinone was discovered in 2020.

In a statement, the Puyallup Tribal Council said a ban would be “hugely important” to protect coho salmon and other fish. “6PPD is a major and uniquely lethal threat to the health of salmon in urban streams on our reservation,” the council said. 

In its letter granting the petition, EPA did not promise an outright ban but said it would publish by next fall an advanced notice of proposed rulemaking under the Toxic Substances Control Act (TSCA). The law grants the agency authority to develop regulations to restrict production or disposal of chemicals deemed to cause risk to human health or the environment. 

The chemical can kill coho salmon within hours, and is responsible for the urban runoff mortality syndrome, which kills the fish as they return to urban streams to spawn, according to Earthjustice. 

EPA also plans to gather more information that could inform its rulemaking. The petition highlights studies which found the presence of 6PPD-quinone in soil, household dust and the urine of pregnant women. Officials noted that while research has already shown 6PPD-quinone is toxic to fish, its impacts on humans are still uncertain. It also intends to finalize a rule requiring manufacturers and importers of 6PPD to report unpublished health and safety studies to EPA by the end of next year. 

In a statement, the tire group said it and its members are already working with regulators, researchers and others to determine if an alternative is available. So far, no technically feasible alternative has been identified, according to the group. It "looks forward to continuing this effort by working with EPA to identify an alternative to 6PPD and to implement it on a time-frame consistent with public safety," says the group.

It also notes that EPA must consider the availability of alternatives when any proposed prohibition takes effect. The group plans to coordinate with EPA on any rulemaking and would provide information on the performance, safety and environmental characteristics of 6PPD, 6PPD-quinone and potential alternatives.

The California Dept. of Toxic Substances Control has already finalized its own regulation earlier this year. It gives manufacturers until the end of this month to notify officials if they sell tires containing 6PPD in the state. Officials say the rule will encourage manufacturers evaluate safer alternatives.