Every fall more than half of the coho salmon that return to Puget Sound’s urban streams die before they can spawn. In some streams, all of them die. But scientists didn’t know why.
Now a team led by researchers at the University of Washington Tacoma, UW and Washington State University Puyallup have discovered the answer. When it rains, stormwater flushes bits of aging vehicle tires on roads into neighboring streams. The killer is in the mix of chemicals that leach from tire wear particles: a molecule related to a preservative that keeps tires from breaking down too quickly.