The U.S. Environmental Protection Agency has formally begun evaluating a chemical compound used in tire manufacturing and its transformation byproduct, setting in motion a regulatory process that could affect a ubiquitous product found on American roads. The review under the Toxic Substances Control Act focuses on 6PPD, an antioxidant added to tire rubber to prevent degradation, and 6PPD-quinone, a compound that forms when 6PPD reacts with ozone as tires wear down during normal use.
Research has linked 6PPD-quinone to mortality in coho salmon, elevating the substance from an industrial additive to an environmental concern that now commands attention at both the federal and state level, as well as from the global tire industry.
Federal Evaluation Underway
The EPA’s evaluation under TSCA will examine both the parent compound, 6PPD, and its quinone form. The agency’s action follows a proposed rule announced in November 2023, which would require manufacturers of 6PPD to report on its use and environmental releases. Under the statutory framework of TSCA, the EPA must first publish a scope document outlining the parameters of its evaluation, then take public comment before completing a risk evaluation within a deadline set by law.
That evaluation will determine whether the agency moves toward regulation. If the EPA finds that 6PPD or 6PPD-quinone presents an unreasonable risk to human health or the environment, the agency is required under TSCA to promulgate a rule addressing that risk.
This federal process is designed to be thorough and deliberate, reflecting the agency’s role as the independent U.S. government body charged with protecting the environment and enforcing federal environmental law. The TSCA framework allows the EPA to assess chemicals already in commerce and, where necessary, impose controls. The evaluation now underway represents an early but consequential stage in that regulatory machinery.
State Action and Industry Response
California has not waited for the federal outcome. The state’s Department of Toxic Substances Control initiated its own regulatory process to assess alternatives to 6PPD in tires. In 2023, California’s Safer Consumer Products program listed 6PPD as a priority chemical for potential restriction.
That designation allows the state to move toward imposing its own requirements on tire manufacturers selling into California, a major market that often drives product formulation changes nationwide. The parallel state and federal tracks could converge: if the EPA finds an unreasonable risk, it would act under TSCA; California, through its Safer Consumer Products program, could independently require manufacturers to substitute 6PPD or meet other conditions.
The Tire Industry Project, a global consortium of tire manufacturers that collectively produce a significant share of the world’s tire supply, has committed to researching safer substitutes for 6PPD. The consortium set a goal of identifying a viable alternative by 2025, a timeline that suggests the industry recognized the direction of regulatory pressure. The research commitment acknowledges that both federal and state actions are shaping the landscape for tire chemistry.
Broader Regulatory Context
The current scrutiny of 6PPD and its quinone occurs within a longstanding regulatory structure. The Environmental Protection Agency was created after President Nixon proposed it in 1970, and it began operating later that same year under an executive order ratified by Congress. Its formation followed a period of growing public and legislative concern about human harm to the natural world, including the publication of Silent Spring in 1962, which shifted attention to the dangers of pesticides, and a conservation bill introduced in 1959 that ultimately failed. Through the 1960s, lawmakers weighed responses to rising environmental pressure.
Today, the EPA enforces national standards under numerous statutes and delegates some duties to states and tribes. That structural arrangement allows California to run its own chemical review while the EPA acts federally, meaning a single substance can face parallel state and national scrutiny.
This matters because the EPA’s authority to assess and restrict chemicals touches products in daily use, including tires that release compounds onto roads and into waterways. Federal and state actions will influence what manufacturers must report, what alternatives they must consider, and ultimately what chemicals remain in the products Americans rely on every day.
