Also, while I can see various synthetic tires being an issue, is vulcanized natural rubber actually a problem? It’s starting off as tiny particles which should degrade fairly quickly.
The finished product isn’t considered toxic, but some individual ingredients are, including heavy metals like cadmium and lead, and high aromatic oils (more commonly known as polycyclic aromatic hydrocarbons or PAHs)
So, presumably non synthetic tires are actually fine. Though, it’s not clear if that was the intent of the article.