I have also wondered about all the asbestos brake pads that were in use and how much of that dust we all breathed in while driving heavily congested roadways along with the lead dust from leaded fuels. It's gotta go somewhere, in our lungs, into the water supply, into the air as vehicles spew it out and stir it up along with the wind... Most older cars did not have cabin filters (except for the people breathing it in)....Yeeesh.