Most of the material in plants (including grass) is created via photosynthesis. Hence the dirt in which it is planted does not sink away as it grows.
Tires mostly turn to dust. In the US, that is 650,000 tons of dust a year. Many believe the rise of latex allergies is related, since 25% of the tire is latex, and the dust that we breathe causes said allergies. Obviously so much dust can cause other problems too.
I'd like to blame anti-matter for something, but it looks pretty innocent to me. As long as it keeps its distance. Which is is prone to do anyway.
If you were smart, you would have asked these questions prior to the advent of the internet and google. They would have been more fun. But there just aren't many mysteries any more.
And as with the news about tires and the harm they do, sometimes the truth hurts.