Monday March 31, 2025
The Seattle Times —
For decades, toxic tire dust has choked coho salmon before they can spawn in their natal streams. Now, King County scientists say they have made a “potential breakthrough” in how to save them.
Preliminary results from a recently completed study show certain soil mixes can effectively filter a toxic chemical out of stormwater, boosting coho salmon’s survival rates significantly. The key may be in special soil mixes containing sand, coconut fiber and biochar, a charcoal-like organic fertilizer, King County scientists said this week.
The results suggest there is a potential solution to a seemingly intractable issue of how coho salmon can survive in urban streams where pollution from traffic is so ubiquitous.
Scientists first identified toxic tire dust, or more specifically the chemical 6PPD-quinone, as a salmon-killer in 2020. For decades, observers had watched in agony as adult coho salmon mysteriously gasped at the surface of urban waters before dying.