EPA Seeks Input on Risks of 6PPD and 6PPD-Quinone in Tires

The U.S. Environmental Protection Agency (EPA) has issued an Advance Notice of Proposed Rulemaking (ANPRM) under Section 6 of the Toxic Substances Control Act (TSCA) to gather information about the potential risks associated with N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its transformation product, 6PPD-quinone. This follows a petition filed by several Native American tribes requesting that the EPA regulate the chemical's use in tires, which was granted in November 2023.

Background on 6PPD and 6PPD-Quinone

For over 60 years, 6PPD has been used in the production of motor vehicle tires to enhance their durability. It is also found in other rubber products, such as footwear, synthetic turf infill, and playground equipment. When 6PPD reacts with ozone in the air, it forms 6PPD-quinone, a chemical compound that can enter stormwater runoff from roads, parking lots, and streets, particularly during rain events. This runoff can carry 6PPD-quinone into streams and rivers, where it has been found to be toxic to aquatic life. In particular, 6PPD-quinone has been shown to be lethal to coho salmon, with concentrations in stormwater in the Pacific Northwest proving fatal after just a few hours of exposure.

EPA’s Request for Information

In its ANPRM, the EPA is seeking public input on a range of issues related to the environmental and human health risks posed by 6PPD and 6PPD-quinone. The agency is particularly interested in information on the chemical's effects on aquatic and terrestrial ecosystems, exposure pathways, persistence in the environment, and bioaccumulation potential. The EPA is also requesting data on additional uses of 6PPD, as well as its presence in consumer products like sneakers, playgrounds, and rubber-modified asphalt.
The agency is also seeking comments on potential alternatives to 6PPD and any transformation products that may result from those alternatives.

Focus on Toxicity and Uncertainties

There is substantial evidence that 6PPD-quinone is highly toxic to fish, especially coho salmon, but less is known about its potential impact on human health. The EPA aims to use the information gathered through this ANPRM to better understand the full range of risks associated with 6PPD and its byproducts and to inform future regulatory actions.

Next Steps

This ANPRM is part of EPA’s ongoing effort to address the environmental and health risks posed by 6PPD, particularly in light of the concerns raised by the Yurok, Port Gamble S’Klallam, and Puyallup Tribes. The information collected will help the agency determine whether further regulatory action is necessary under TSCA Section 6.