Burn Rubber, a Physics Question

[Anamoly]

Okay, here is the question, I am a little clueless on where to start, on how I would go about solving this. Any help is greatly appreciated. Thanks

The rubber worn from tires mostly enters the atmosphere as particulate pollution. Estimate how much rubber (in kg) is put into the air in the United States every year. To get you started, a good estimate for a tire tread's depth is 1cm when new, and the density of rubber is about 1200kg/m^3.

[HallsofIvy]

Okay, about how often do you need to buy new tires? That's the time required to remove that 1 cm. You will also need to estimate the average radii and width of tires so you can convert that to volume worn in that time and multiply by 1200 kg/m^3 (watch your units here!) to get the answer in kg. for one tire over that time period. If your time period is in years, divide by it to get kg. per tire for one year and then multiply by the number of tires in use in the United States.