I actually remember reading about this in a book “Life after cars”. Great read, would recommend !

<…> Tire companies like the one named after Sarah’s ancestor guard their chemical concoctions closely, veiling themselves behind a variety of regulations that protect “proprietary” technologies. (Fossil fuel companies do the same with the liquids they use for fracking.) The tire companies were not going to help figure out the mystery of what exactly was killing the salmon. So researchers at the University of Washington for years doggedly sifted through the dozens of chemicals they found in runoff until they isolated the one they allege is responsible for the salmon deaths. The culprit turned out to be a by-product of a molecule called 6PPD, which for the last sixty years or so has been used as a kind of tire preservative. The ground level ozone that cars give off (a dangerous pollutant that is distinct from the beneficial ozone layer in the atmosphere) can actually harm tires; 6PPD protects them against ozone-induced decay. In so doing, however, it degrades to create a different molecule, 6PPD-quinone, which turns out to be fatal to coho salmon. So the chemical that protects the polluting car’s tires from its own pollution creates even more pollution.

and

<…> Scientists say that 6PPD-quinone, along with the countless other toxic chemicals that run off our roads, could be captured by creating natural buffer zones of plants and wetlands that would filter out the poisons before they could reach the delicate ecosystem of, say, a particular stream that is vital to migrating cohos. Perhaps, like guardrails, this type of solution could be written into road engineering codes, mitigating the damage that roads do to the most sensitive habitats. No one thinks, though, that a scattering of human-engineered roadside filtration marshes could even begin to address all the harms—many of them yet unknown—that 6PPD-quinone presents to the natural world. A more systemic approach might result from lawsuits, which could pressure tire companies to find a replacement for 6PPD, but what are the chances that the replacement will be completely benign? In the meantime, the tires keep rolling along, their decay coating the asphalt that spreads across the land, mixing with rain from ever-morepowerful storms caused by climate change, and ultimately washing into bodies of water. There, the poisonous cocktail is metabolized by some of our planet’s most delicate and irreplaceable creatures, desperately trying to get upstream.