"When tires wear on pavement, 6PPD is released. It reacts with ozone to become a different chemical, 6PPD-q, which can be extremely toxic — so much so that it has been linked to repeated fish kills in Washington state.... Testing by a British company, Emissions Analytics, found that a car's tires emit 1 trillion ultrafine particles per kilometer driven — from 5 to 9 pounds of rubber per internal combustion car per year....
a team of researchers, led by scientists at Washington State University and the University of Washington, who were trying to determine why coho salmon returning to Seattle-area creeks to spawn were dying in large numbers.... in 2020 they announced they'd found the culprit: 6PPD....
Tests by Emissions Analytics have found that tires produce up to 2,000 times as much particle pollution by mass as tailpipes."
