[Lewis Thomson (OP)]

Jeremy has written in asking us this question,

"I would like to know what happens to the rubber dust that comes of vehicle tires. Where does it go and is it dangerous to our health? I also have the same question on the dust from brakes. It seems that there is a lot of focus on the exhaust emissions but I suspect that the tire and brake dust could be harmful to the environment too."

Discuss your findings in the comments below...

[Petrochemicals]

It is, the wash off from roads is considered hazardous and there are methods to deal with it such as Reed beds.

https://www.newcivilengineer.com/latest/road-runoff-pollution-ignored-claim-environment-agency-insiders-11-03-2020/

[alancalverd]

Asbestos brake dust used to be a serious hazard for garage workers but has lessened with the advent of disc brakes and the inclusion of materials in the pads to agglomerate the dust into larger particles that fall on the road and get washed into the drains and soil. Rubber dust is less hazardous and gets washed away anyway.

The direct contribution to global warming is small but calculable as the function of a mechanical brake is to convert kinetic energy into heat. 

[vhfpmr]

If the brakes haven't dissipated the energy by the time the car comes to a halt, then wind resistance and other general friction will have, so it comes down to whether the car is powered by renewable energy or fossil fuel, not whether you use the brakes.