The Environmental Protection Agency (EPA) has initiated a regulatory investigation into the potential environmental and human health risks posed by N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its transformation product, 6PPD-quinone. This action, driven by a petition from tribal organisations and environmental groups, seeks public input on alternatives and regulatory measures under the Toxic Substances Control Act (TSCA).
Why 6PPD is Under Scrutiny
6PPD, a chemical widely used in vehicle tires to prevent rubber degradation, is under investigation due to its transformation into 6PPD-quinone. Studies have linked 6PPD-quinone to acute mortality in aquatic species such as coho salmon, triggering "urban runoff mortality syndrome" in waterways near urban areas. These findings raise significant concerns about its impact on ecosystems and human health.
The investigation follows a 2023 petition filed by Earthjustice on behalf of the Yurok Tribe, Port Gamble S’Klallam Tribe, and Puyallup Tribe of Indians. The petition stated,
“Exposure to 6PPD-q[uinone] can kill a coho salmon within hours, and the chemical is responsible for ‘urban runoff mortality syndrome,’ which kills up to 100% of coho returning to spawn in urban streams.”
The petition further highlighted the chemical’s presence in sediments, household dust, and even the urine of pregnant women, with emerging studies suggesting potential toxicity to mammals.
Call for Data and Public Comment
The EPA is actively soliciting input from researchers, industry stakeholders, and the public regarding the environmental impact, exposure pathways, and safer alternatives to 6PPD. Comments and data must be submitted by 21 January 2025. Topics of interest include the chemical’s environmental fate, potential regulatory measures, and case studies of successful mitigation strategies.
Exploring Safer Alternatives
Efforts are underway to identify and evaluate alternatives to 6PPD. A consortium led by the United States Tire Manufacturers Association (USTMA) is researching substitutes such as other phenylene diamines, graphene-based materials, and bio-based polymers. California and Washington State have also launched initiatives to assess these alternatives under their Safer Consumer Products programmes.
Tribal and Environmental Justice Implications
Tribal nations, whose cultures and economies rely heavily on salmon populations, have underscored the urgency of regulatory action. The Yurok Tribe, in particular, emphasised in the petition that exposure to 6PPD-quinone poses a direct threat to their water resources and traditional lifeways. “Salmon and steelhead populations...cannot recover without its removal from the environment,” the petition stated.
