Tire chemicals cause salmone decline

As many as 90% of Puget Sound salmon die before they can spawn. Storm water runoff from urban areas and roads were thought to be responsible, and scientists have identified the culprit.

The chemical antioxidant 6PPD is used in tires to increase their longevity, but tires still break down over time. As they do, 6PPD as tire treads break down over time and leave behind bits of microplastics on roads, the 6PPD reacts with ozone to become a byproduct called 6PPD-quinone. So toxic is this chemical compound to coho salmon that it’s thought to be the primary reason for their dramatic population decline.

Four coho salmon populations are listed as threatened under the Endangered Species Act by the US Fish and Wildlife Service.