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Adopted Priority Product: Motor Vehicle Tires Containing 6PPD

Effective October 1, 2023: Motor Vehicle Tires Containing N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD)

DTSC has finalized a regulation pursuant to the Safer Consumer Products (SCP) Regulations to list a new Priority Product: motor vehicle tires containing N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), effective October 1, 2023.

Domestic and foreign manufacturers of motor vehicle tires (as defined in the regulation) that contain 6PPD and whose products are placed into the stream of commerce in California must submit a Priority Product Notification (PPN) for those products by November 30, 2023. After submitting the PPN, manufacturers have the option to submit one of the following through CalSAFER by March 29, 2024:

The responsibility to comply falls first on manufacturers, but if a manufacturer fails to comply, the responsibility to comply may shift to importers or retailers, if DTSC notifies them accordingly.

Manufacturers of motor vehicle tires whose products do not contain 6PPD need not take any action.

Available Alternatives

To facilitate manufacturers’ search for alternatives, we included a non-exhaustive list of potential alternatives in the Priority Product Profile (pp. 66-68). The SCP Regulations define “alternatives” broadly, including changes to the product that reduce or eliminate the use of 6PPD, with or without the use of a replacement chemical, or any other change to tires that reduces exposures or potential adverse impacts caused by the Priority Product.

The Priority Product Profile summarizes information compiled by DTSC as of February 2022. Since then, new resources and information have emerged that may help manufacturers identify potential alternatives. We provide a few resources below, but please keep in mind that this is not an exhaustive list and that including the alternatives and resources below does not constitute an endorsement by DTSC. We have not vetted any 6PPD alternatives for safety, functionality, or performance; assessing that is the responsibility of the manufacturer. Manufacturers who elect to perform an Alternatives Analysis must consider all the information on potential alternatives included on our website. Additionally, they must document why the information they rely upon meets SCP’s definition of “reliable information” and explain all the criteria used when selecting their proposed alternative.

Information on Potential Alternatives

Efforts to Develop Potential Alternatives

(These resources may be used to support the Alternatives Analysis but do not need to be included in the report at this time)

Other Resources

Please contact Kelly Grant (kelly.grant@dtsc.ca.gov) for more information about these resources.

Rationale for Priority Product Listing

6PPD has been used as an antidegradant for decades and is found in most, if not all, motor vehicle tires. 6PPD performs the critical function of protecting rubber from reactions with ozone and oxygen, which can lead to cracks.

However, 6PPD is toxic to many aquatic organisms throughout the food chain and can impair wildlife survival. 6PPD-quinone, a reaction product of 6PPD, is acutely toxic to coho salmon and kills fish within a few hours after exposure. While little is known about the effect of 6PPD-quinone on other organisms, 6PPD-quinone is also acutely lethal to other, related fish species found in California, including brook trout, steelhead/rainbow trout, and, to a much lesser degree, Chinook salmon.

Over the life of a tire, 6PPD continuously migrates to the surface, where it provides protection from degradation caused by ozone and oxygen. Tire wear particles (TWP) are generated as tires roll across the road surface, particularly as vehicles brake, accelerate, and turn. TWP, and the 6PPD they contain, can then enter the aquatic environment from road dust carried by surface runoff and stormwater.

While it is unclear exactly where and how 6PPD-quinone is formed, detections of 6PPD-quinone in California waterways clearly indicate that this chemical is sufficiently persistent in aquatic systems for aquatic organisms to be exposed at levels that may cause harm. 6PPD-quinone has been measured in California streams at concentrations above those shown to kill at least half of coho salmon in laboratory experiments.

Based on the criteria in the SCP Regulations, we have determined that aquatic organisms can be exposed to 6PPD and 6PPD-quinone derived from motor vehicle tires. This exposure may cause or contribute to significant adverse impacts to aquatic organisms, including two populations of coho salmon in California, one of which is endangered, the other threatened. Exposure to 6PPD and 6PPD-quinone may jeopardize the recovery of coho salmon and other imperiled species. The loss of coho salmon in California has significantly impacted Native American tribes in California that have traditionally relied on the species as an important food source. The loss of core traditional food sources for tribal communities has been linked to loss of culture, increased physical and mental health issues, and increased poverty.

More details can be found in the Product-Chemical Profile or check out our brief video on 6PPD in tires.

Public Engagement

We began researching this topic in late 2020. On July 29, 2021, we hosted a pre-regulatory public workshop to receive input on our draft Priority Product Profile. Materials from that workshop are available on our 2021 Workshops and Events Webpage. We held a public comment period for this regulatory proposal between May 20 and July 20, 2022. The public comments received can be found on CalSAFER. We considered both verbal input received during the pre-regulatory workshop and written comments submitted during the pre-regulatory comment period, available on CalSAFER, to refine our Priority Product definition and listing.

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