Tyre compound driving mystery salmon deaths identified after years of chemical detective work

Every autumn in urban streams around Seattle, many Coho salmon that return to spawn die when it rains. While there had been clues of what causes this urban stream syndrome as early as 2005, the exact cause of their deaths remained mysterious. Storm water is a very complex mixture, stresses Tian. ‘You will see thousands of chemical features in these mixtures, and most of them are still unknown,’ he says. That motivated the team to query whether one of these substances was killing the salmon. ‘We are producing and using hundreds of thousands of anthropogenic chemicals, so these are inevitable results,’ Tian says.