Scientists at Washington State University (WSU) have been studying for years why Coho salmon in Puget Sound creeks seem to die more frequently after rainstorms.
New research led by WSU PhD Student Stephanie I. Blair shows exactly how the fish are dying in an event named “coho urban runoff mortality syndrome.”
In 2018, researchers found that the die-offs were linked to pieces of car tires washing into creeks through stormwater runoff, according to a release from WSU.
A 2020 study revealed the runoff contained a chemical in a tire preservative called 6PPD.
Blair and her team recently found that when 6PPD interacts with the ozone, it becomes a toxic chemical called 6PPD-quinone.
Scientists say it can breach the cellular walls of the blood-brain barrier and blood-gill barrier, causing oxygen deprivation.
The study, published in the journal Environmental Science & Technology, says even though Coho salmon are most sensitive to the chemical, it’s also toxic to other fish and mammals, with possible effects on human health.
“We need those tools to be available so we can start screening for alternatives to 6PPD,” Blair said. “This tells us how to evaluate a potential substitute.”
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