WASHINGTON — The Environmental Protection Agency is reviewing the tire chemical 6PPD-quinone under the Toxic Substances Control Act, following a 2024 study that linked the compound to an increased risk of Alzheimer’s disease. The agency added 6PPD-Q to its list of chemicals of concern in 2023, and is now working with tire manufacturers to find alternatives to 6PPD, the precursor chemical that transforms into 6PPD-quinone when exposed to ozone. The 2024 study that flagged the Alzheimer’s link has prompted researchers to plan further investigations.
These will include epidemiological studies that measure 6PPD-Q exposure in blood or urine samples and then correlate those levels with Alzheimer’s incidence over time. The National Institutes of Health has indicated interest in funding such research.
The EPA’s review under the Toxic Substances Control Act is ongoing. The agency added 6PPD-Q to its list of chemicals of concern in 2023. California’s Department of Toxic Substances Control began its own evaluation of 6PPD in tires in 2023, considering whether to designate it as a priority product for regulation.
The tire industry, represented by the U.S. Tire Manufacturers Association, has committed to researching safer alternatives. The timeline for regulatory action remains uncertain.
The emerging evidence linking the chemical to Alzheimer’s may accelerate efforts to reduce tire particle pollution through means such as improved road design or tire formulations. The epidemiological studies that researchers are planning will need to be carefully designed. Measuring 6PPD-Q exposure in blood or urine is technically feasible, but correlating those levels with Alzheimer’s incidence over time requires long-term studies with large populations.
The NIH’s interest in funding such research is a positive signal, but the studies themselves will take years to complete. In the meantime, the EPA’s work with tire manufacturers to find alternatives continues. The commitment from the U.S. Tire Manufacturers Association suggests the industry is taking the issue seriously.
The 2023 addition of 6PPD-Q to the EPA’s chemicals-of-concern list was a formal recognition that the compound warranted closer scrutiny. The emerging evidence may accelerate efforts on multiple fronts — not just chemical substitution, but also engineering solutions.
Improved road design that captures and treats runoff before it reaches waterways could reduce human exposure even if the chemical remains in use. Changes to tire formulations that reduce particle shedding could also help. For now, the regulatory timeline is uncertain.
The EPA’s review under TSCA could take years, and California’s priority product evaluation is also ongoing. But the convergence of scientific evidence, federal and state regulatory attention, and industry commitment to finding alternatives suggests that change is coming. Consult your doctor for medical advice.
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