Coho salmon were the first warning. Concentrations of 6PPD-quinone in Pacific Northwest stormwater proved lethal to the fish after only a few hours, the Environmental Protection Agency has said, and the compound is linked to a die-off known as urban runoff mortality syndrome. A new paper now asks whether the same tyre chemical deserves a look for what it might do to people.
The salmon case
6PPD is added to tyres to slow cracking and is nearly everywhere in US tyre manufacturing, SeafoodSource reported. Once exposed to ground-level ozone it becomes 6PPD-quinone. In November 2023 the EPA granted a petition from the Yurok, Port Gamble S’Klallam and Puyallup Tribes, brought through the group Earthjustice, though it stopped short of a ban.
The Puyallup Tribal Council called 6PPD “a major and uniquely lethal threat to the health of salmon in urban streams on our reservation.” Nisqually Tribe Chairman William Frank III told a Senate committee the tribe had watched salmon populations decline dramatically over thirty years.
Now the brain
The new work is a computer analysis in the journal Open Medicine, by Chun Zhang and Jingqi Zhang. It reports that 6PPD-quinone binds strongly to three of five genes that predict Alzheimer’s disease, in a simulation that also suggested trouble for microglia, the brain’s immune cells. The authors lean on earlier findings that the compound can pass through the blood-brain barrier in mice and has been detected in human blood and urine.
Nobody has shown that the chemical harms human neurons. The brain tissue came from late-stage patients, and one dataset included only 12 Alzheimer’s cases. The authors say experiments on living cells, animal studies and long-term epidemiology are needed.
The regulatory side moved first. On Nov. 14, 2024 the EPA issued an advance notice of proposed rulemaking asking for data on 6PPD and 6PPD-quinone, including potential human health effects and alternatives to 6PPD.
Sources
- US Environmental Protection Agency begins investigation of tire chemicals harming salmon (SeafoodSource)
- EPA Issues Advance Notice of Proposed Rulemaking to Protect Salmon from Chemical Used in Rubber Products
- A common chemical from car tires might disrupt human brain cells and promote dementia (PsyPost)
- Invisible Tire Dust Hijacks Alzheimer's Predictor Genes (Neuroscience News)
