The U.S. Environmental Protection Agency (EPA) has issued an advance notice of proposed rulemaking (ANPRM) to investigate the risks associated with N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its highly toxic byproduct, 6PPD-quinone. The chemical, used to extend tire lifespan, has been linked to severe ecological damage, including mass salmon deaths in U.S. waterways. This move responds to a 2023 Tribal petition under the Toxic Substances Control Act (TSCA) and aims to protect aquatic ecosystems and human health.
ANPRM: A Key Step Toward Regulation
The EPA’s ANPRM, published under Section 6 of the TSCA, opens a critical public comment period for stakeholders to provide scientific data, technical studies, and input on the environmental and health impacts of 6PPD and 6PPD-quinone. It specifically requests insights into the chemicals' effects on aquatic and terrestrial ecosystems, human exposure pathways, persistence, and bioaccumulation. Additionally, the agency seeks information on potential alternatives to 6PPD and mitigation technologies.
The ANPRM outlines the risks posed by 6PPD-quinone, which is formed when 6PPD reacts with ozone in the atmosphere. This chemical is found in stormwater runoff, particularly in urban areas, and is known to cause acute mortality in coho salmon. Data suggest that other aquatic species, including steelhead and rainbow trout, are also vulnerable.
Environmental and Cultural Impacts of 6PPD-Quinone
Research has highlighted the devastating ecological effects of 6PPD-quinone on sensitive aquatic life. The chemical has been implicated in urban runoff mortality syndrome, which has severely impacted salmon populations in the Pacific Northwest. Salmon are not only vital to regional ecosystems but also hold cultural, economic, and spiritual significance for Tribal communities.
The Yurok Tribe, Port Gamble S’Klallam Tribe, and Puyallup Tribe of Indians, who spearheaded the 2023 petition, underscored the profound harm caused by declining salmon populations. "Thriving salmon populations are essential for subsistence, cultural practices, and the economic well-being of Tribes," the petition stated. In granting the petition, the EPA acknowledged its obligation to act under TSCA to address the risks.
Seeking Alternatives and Filling Knowledge Gaps
A major focus of the ANPRM is identifying and evaluating safer alternatives to 6PPD for use in tires. The EPA is collaborating with state initiatives, including California’s Safer Consumer Products Regulations and Washington State’s Safer Products Program, to advance alternative assessments. Preliminary studies suggest potential replacements, such as other phenylene diamine derivatives, plant-based polymers, and novel additives like graphene nano-platelets.
The ANPRM also highlights the need for additional research to fill existing knowledge gaps, particularly concerning the long-term environmental fate of 6PPD-quinone, its transformation products, and their potential human health impacts. EPA is actively funding investigations into these areas, including methods to detect and remediate the chemical in contaminated stormwater and sediments.
Ongoing Research and Mitigation Efforts
The EPA has already made strides in developing screening values for 6PPD-quinone to guide water quality standards. Researchers have created analytical tools to monitor the chemical in surface and stormwater. The agency is also testing green infrastructure solutions, such as biofiltration systems, to mitigate contamination before it reaches waterways.
Despite these efforts, uncertainties remain about the potential impacts of 6PPD-quinone on human health. Preliminary studies suggest that the chemical may bioaccumulate in the food chain and adversely affect neurological and metabolic functions. Populations near roadways and urban watersheds, as well as workers in tire manufacturing and recycling, may face heightened risks of exposure.
Next Steps for Regulation
The EPA is now soliciting comments and data from industry stakeholders, researchers, and the public to inform a potential rulemaking process. This process may include restrictions on the manufacture, distribution, or use of 6PPD, requirements for labeling and monitoring, or an outright ban.
“This is an opportunity to address one of the biggest threats to salmon recovery in Puget Sound,” said Rep. Derek Kilmer (WA-06). “It’s crucial that we work together to find solutions that protect ecosystems, uphold Tribal treaty rights, and ensure the sustainability of local fisheries”.
The EPA’s ANPRM on 6PPD and 6PPD-quinone represents a pivotal moment in addressing environmental risks posed by tire-related contaminants. Stakeholder contributions during the comment period will play a critical role in shaping future regulations, driving innovation in safer alternatives, and protecting both ecological and human health.
