While true, there's other stuff that generates much more tiny dust particles - tires. Heavy vehicle tire rub is cause to roughly 1/3 PM2.5+ air polution, consid

While true, there's other stuff that generates much more tiny dust particles - tires. Heavy vehicle tire rub is cause to roughly 1/3 PM2.5+ air polution, considering all sources. (Used to work for a exhaust emissions systems manufacturer, I remember reading studies about this, can't give you source now). So, the small particle dust from such motors, I imagine, is a minuscule source to air polution, compared to tire abrasion.