What happens to all the tire rubber from all the cars on the highway?

Hey, Matt:

As I sat in my car, parked on the highway at the 5/805 merge the other afternoon, a curious thought came into my mind. There must be 10 million cars and trucks on the highway at any given hour of the day. They all have various quantities of tires on these vehicles. I have to replace my tires every couple of years because they come up bald. Where does all that rubber go? There should be piles of the crumbs or mounds of rubber dust along every roadway in the world. It's like it just evaporates. It's magic!

-- Mort Schwarts, Sr., Encinitas/Leucadia

Apparently Mort spends so much time at the merge he occasionally forgets where he lives. Well, be that as it may, Mr. S, to answer your own question, as you idle on the asphalt, stick your head out the window and suck in a big toke of l'aire du commute. The American Automobile Manufacturers Association sez there are about 210 million cars, trucks, and buses registered in the U.S. That's about a third of the world's total. That's a lotta liberated rubber. The road surface reduces it to dust, which is either sucked up into the air or washed off the road and into our back yards, lakes, rivers, etc. Studies of particulate air pollution show that a lot of the black soot that collects on our windowsills and circles around the globe is made of tire crumbs and shredded brake linings as well as the usual collection of dust, bugs, and industrial and car exhaust crud. Out of sight, out of mind? Out of sight, into lungs. The elves are making a name and address tag that you can pin to your mittens to make sure you pull into the right driveway every evening.