[Sunspot]

This is something I ran across when I was looking for simple facts about rubber. Just a "fun fact". I don't have the reference handy, and I'd rather not have to dig for it, so if this turns into some sort of POMB liquid elimination contest please leave me out of it.
Anyway: we all drive around on rubber tires. The tires wear down. Clearly there is rubber being deposited on the roadway. Now one would expect that in time, on heavily traveled areas in particular, there would be a build-up of rubber. But when a sample of a road is examined in a laboratory, only minute trace amounts of rubber are found. No build-up at all.
Sooooooooo, where does the rubber go???

[CARVER]

In the air I think, burning rubber, and thus some of it ends up in our lungs I think.

[lawnchair]

Some tire dust gets blown into the air, but most washes into whereever road runoff is going.

[Sunspot]

Nope.

[No-Oil]

Theres not that much rubber in a tyre, the primary constituent being "carbon black" I believe. This is what gives it the black colour. Minute particals are laid down evry time the wheel rotates & I guess this extremely fine carbon dust blows away on the wind. Only when you skid the tyre does a serious amount of wear take place, such that smoke is generated or rubber is deposited on the road surface, this kind of deposit normally washes away in the first heavy rain that comes along.

[Sunspot]

Well, that's not the answer I have, mine is more interesting. Rubber is kinda sticky, and being hydrocarbon based - "synthetic" rubber is made from oil (what the hell isn't??) it shouldn't dry up and blow away. At least there would be residue build-up in cracks, larger and micro cracks. But there isn't.
And I've never heard of any concern about rubber build-up on a roadway outside car races, where it does happen. Of course they're stripping rubber off those tires at a far greater rate than we are.
Try again...

[dmtu]

Some of it oxidizes and I think it would be safe to assume some "evaporates". Dry rot.

[Sunspot]

Not it.
Hint: Rubber is organic.

[Grimnir]

I know! I turns back into oil, seeps down into wells, and is responsible for the abiotic oil theory!

[kelee877]

My guess is that the birds eat it..and that is why they have that big blob of black in the middle of their poop, that is very annoying to wash of your car and sometimes leaves a stain...lol..and bird droppiongs are very slippery when wet..yuck

[Sunspot]

Kelee is getting closer. But ya gotta think smaller....
And I have to go to work soon, so the answer may have to wait until tomorrow. I'm sure you're all just dying to know...

[SD_Scott]

Sportbike tires sorta peel and ball up the rubber and then the centrifugal force throws it all over the place. After a motorcycle roadrace it's funny to walk around the pits and see all the pieces of rubber laying around. It's almost like a pencil eraser the way it comes off the tire. Some pieces are small like a BB and some are pretty big, 1/4 inch in diameter and an inch or two long. Riding a sportbike slow on the street doesn't cause this effect. Passenger car tires are so hard that they probably just produce more dust than anything. Excellent point though, that stuff is going somewhere.

Check this out. An ex-Formula 1 driver recently underwent a medical exam and found out his lungs were full of carbon dust. It is due to all of the years he raced in F1. F1 uses carbon brakes that produce this dust.

[Sunspot]

Shannymara wins the prize! Yep, apparantely we are driving down a carpet of micro-organisms who are just waiting to feed off our tire residue. Life finds a way, doesn't it? Thanks for the responses, I think this is a neat "fun fact". And it's probably even true!

[eastbay]

You mean the wind and rain don't wash most of it away??

C'mon now, that's more to the disappearing rubber story than microbes dear. The force of a periodic rainstorm just about anywhere in America cleans the roadway quite thoroughly and must be responsible for eliminating some (maybe even most) of the used rubber particles.

[dmtu]

Microbes eh?

This is kind of related. When I was about thirteen I received a horrible bout of roadrash as the result of being towed behind a moped on a skateboard. The next day the family went to the ocean, the salt water made my wounds heal quickly but I developed a light brown spot on that side of my body that year. I've asked doctors if it could be related to some type of infection I gathered from the road or the ocean and they all laugh but I still have to wonder. I still think some nasty bug got in there and caused this organic tattoo because we all know my genetics are absolutely perfect.