6PPD and Tire Manufacturing

U.S. Tire Manufacturers Association (USTMA) members are committed to producing the safest, most durable and most efficient tires possible. As such, all USTMA members use a chemical called 6PPD to help tires resist degradation and cracking, which is vital for driver and passenger safety. In December 2020, a report published by researchers at the University of Washington and the Washington Stormwater Center (Tian et al.) identified a 6PPD transformation product that they called 6PPD-Quinone and concluded that it is toxic to coho salmon and may be causing urban runoff mortality syndrome in this fish species. Earlier studies of 6PPD transformation products had not identified this substance.

USTMA and its members are committed to collaborating with researchers and regulators to better understand these distinct compounds (6PPD and 6PPD-Quinone), resolve knowledge gaps and determine appropriate steps to ensure continued driving and environmental safety.

As global leaders in manufacturing, USTMA member companies embrace a shared responsibility of helping to achieve a more sustainable society. With this commitment,USTMA members continually look for new ways to improve both their products and operations and their understanding of the impact of tires on the environment.


6PPD is an antioxidant and antiozonant that helps prevent the degradation and cracking of rubber compounds caused by exposure to oxygen, ozone and temperature fluctuation. 6PPD is used industry wide to help tires resist degradation and cracking, which is vital for driver and passenger safety. Antioxidants support increased tire endurance. There are no known alternatives to 6PPD that provide the same safety and performance characteristics in a tire.

6PPD-Quinone is NOT used in U.S. tire manufacturing. It is a transformation product of 6PPD that may form when 6PPD reacts with oxygen and/or ozone. While 6PPD has been studied, not enough is known about this newly discovered transformation product, 6PPD-Quinone. While the Tian et al. study suggested a connection between exposure to 6PPD-Quinone and coho salmon mortality, subsequent research has shown that 6PPD-Quinone does not exhibit acute lethal toxicity to other freshwater aquatic species and has a comparatively low leaching potential from rubber particles in aqueous media.

USTMA takes seriously the findings of the Tian et al. study, but there are still many questions that need to be answered in order to drive solutions.

Read more on USTMA’s efforts to understand and address the potential impacts of 6PPD and 6PPD-Quinone


The tire industry is science-driven and committed to safety and sustainability, as evidenced by the tens of millions of dollars invested in peer-reviewed research with the World Business Council for Sustainable Development Tire Industry Project (TIP). The focus of TIP research is to assess the impact of tire materials on the environment, wildlife, and human health, including tire and road wear particles (TRWP).

USTMA not only collaborates with TIP, but since 2019, USTMA also has engaged with Washington state researchers and regulators on stormwater issues that may be impacting urban runoff mortality syndrome in coho salmon. Additionally, USTMA worked with TIP and researchers in Washington to produce samples of cryogenically milled tire tread (CMTT) to support research on TRWP. Researchers are able to request CMTT samples here

Since becoming aware of the Tian et al. study in late 2020, USTMA has led efforts to identify relevant data gaps for 6PPD-Quinone and to develop plans to fill those gaps. Throughout 2021, USTMA convened a global 6PPD task force comprised of USTMA, ETRMA, and Tire Industry Project (TIP) staff and member company representatives to address the study’s findings.

Other efforts by USTMA to learn more about 6PPD and 6PPD-Quinone include:

  • USTMA is actively and voluntarily engaged with the California Department of Toxic Substances Control (DTSC ) to support regulatory actions to advance the review of 6PPD in tires under the Safer Consumer Products Regulations (SCPR).
  • USTMA members via the World Business Council for Sustainable Development’s Tire Industry Project (TIP) are currently sponsoring research into 6PPD-Quinone.
  • USTMA is actively engaged in ongoing conversations with both federal and state regulators in Alaska, California, Oregon and Washington State.
  • USTMA has been engaged with the U.S. EPA on this issue to share its actions and to learn more about EPA’s activity on this topic.
  • USTMA testified before the House Natural Resources Subcommittee on Oversight and Investigations to outline the tire industry response to the Tian et al. 2020 study and advocate for stakeholder collaboration.
  • USTMA participated in UC Berkeley’s Greener Solutions Program, a project-based class supported by DTSC, WA Department of Ecology and EPA Region 9.
  • USTMA is an active member of the Washington State Stormwater Work Group, 6PPD subgroup.


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