[ipqk]

Certainly most particulate matter, and it's not even close. Comparing particulates to gas emissions is difficult, so there's no way to say what's "most".

Either way, my greater point still stands: switching to EVs isn't a cure-all to breathing around cars.

[JumpCrisscross]

Sure, I suppose this is where I find umbrage with the claim. Instead of “most” maybe try “a comparable quantity of”? (I’d cut to the chase by clarifying tyres and brakes are the principle source of particulate matter, a pollutant with proven harms.)