Reference image of wild coho salmon. Fish returning to spawn in streams in the Pacific northwest are being poisoned by a chemical contained in fragments of car tyres washed into waterways, say scientists.

Car tyre fragments killing salmon, say US researchers

Pollution from car tyres that washes into streams and rivers has been blamed for annual die-offs of coho salmon in Washington state on the west coast of the United States.

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Stormwater exposure has been causing unexplained acute mortality in coho when they return to urban streams to reproduce.

Researchers identified that fragments of tyres washed into watercourses are the cause of the problem. The tyres contain chemicals to prevent them breaking down but also prove deadly to the fish.

Samples taken from urban streams around Puget Sound, near Seattle, and subsequent laboratory work identified a quinone transformation substance called 6PPD as the culprit.

Cardio-respiratory problem

It’s currently unclear how it kills the fish but Jenifer McIntyre, an assistant professor of aquatic toxicology at Washington State University, told The Guardian it was likely to be an “acute cardio-respiratory problem”.

The finding suggests that fish and other wildlife around the world are also at risk from the chemical, study co-author Edward Kolodziej, an associate professor at the University of Washington, said.

The study is published in the journal, Science, and can be accessed here.