A US judge will decide if, as research suggests, a chemical tyre additive is harming endangered fish species
Last week, a district judge in San Francisco, California, presided over a three-day trial brought by west coast fishers and conservationists against US tyre companies. The fishers allege that a chemical additive used in tyres is polluting rivers and waterways, killing coho salmon and other fish. If successful, the case could have implications far beyond the United States.
The case was initiated after the apparent solving of a decades-old mystery: what was causing mass deaths of endangered coho salmon in the Pacific north-west as they returned to streams to spawn. The deaths happened after heavy rain. Before dying, the fish would exhibit unusual behaviour, swimming in circles, their mouths gaping, as if gasping for air. Scientists, suspecting storm runoff, described the phenomenon as “urban runoff mortality syndrome”.
It took years for scientists from Washington State University to pinpoint what they now allege is the chemical culprit. In 2020, they published a study in Science that claimed to solve the mystery: they found a toxic substance in leachate from car tyres that killed the fish. Known as 6PPD-quinone or 6PPD-q, it is an oxidation product from 6PPD, a chemical added to car tyres to prevent them breaking down. This transformed chemical, 6PPD-q, leaches into rivers and creeks with, scientists say, devastating results for the protected and endangered species.
