Coho salmon returning from its years at sea to spawn, seen near the Suquamish Tribe’s Grovers Creek Hatchery.
The return of coho salmon to the rivers and creeks around Seattle was a conservation triumph—the hard-won result of millions of dollars of habitat restoration work. But around 20 years ago, when the muscular, determined bodies of cohos started returning to these urban waterways to spawn, a mysterious phenomenon cast a dark pall over their homecoming.
After it rained, the iconic fish started dying in droves, but nobody knew why. In the streams hit by the unknown scourge, 40 to 90 percent of the salmon went belly up.
Now, new research published in the journal Science has finally nailed the culprit: tires.
The researchers identified a chemical called 6PPD, a common rubber additive aimed at making car tires last longer, that transforms into deadly 6PPD-quinone when unleashed in nature.
“We pretty much figured out that anywhere there’s a road and people are driving their car, little bits of tire end up coming off your tire and end up in the stormwater that flows off that road,” Ed Kolodziej, a chemist at the University of Washington whose lab led the study, tells Rosanna Xia of the Los Angeles Times. “We were able to get all the way down to this one highly toxic chemical—something that kills large fish quickly and we think is probably found on every single busy road in the world.”
More studies are needed to determine how sensitive other salmon species are to the chemical, not to mention whether it’s harmful to humans, McIntyre tells the Los Angeles Times.
The Seattle Times reports that there are roughly 3.1 billion tires globally manufactured each year, painting a picture of a dauntingly pervasive pollutant.
https://www.smithsonianmag.com/smart-news/researchers-reveal-why-seattle-salmon-bite-dust-after-rain-180976463/?