There's a practice here (UK) of buying diesels for the increased fuel economy, then having the particulate filters removed (discreetly, leaving the casing in place to hide the work) to reduce maintenance costs. Most garages offer this as a service openly, and it's common practice.
The cars are very easy to spot as the exhaust belches huge clouds of thick black smoke every time they accelerate.
The irony of this is that a great many of the cars currently on the road here are dirtier than cars that were banned twenty years ago for that same reason. The point being that we're not just not fixing the problem - we're actively going backwards.
I don't take my son to school through the car park (the most direct route) anymore for this reason. Most parents drive 4x4s which they idle there while parked. The smell alone is eye-watering, not to mention the smoke.
The point is that people just don't care. They don't care about their own kids' health, so of course they don't care about anyone elses.
Anyone I've discussed this with offline think it's silly to be bothered by this or I'm over-reacting, because (and I don't have the science to back this up) the world's getting progressively more stupid and (ob)noxious over time.