Describing what LA currently has as "Smog" really doesn't give people now an idea of what LA smog was like when I was growing up in the 60s. It was like Beijing is now. You have to go way inland to get anything even remotely resembling 60s smog. 

What you get now is slightly tinted water vaper. We had "smog alerts" when I was a kid, where breathing LA air felt like breathing mustard gas. It burned your eyes, it burned your nose, and it especially burned your lungs.

Cleaning up LA's air did come at a cost though. It de-industrialized the area. All of the major employers in South Central LA and the industrial areas to the east pulled up stakes and moved, deepening entrenched poverty in the area. There are plenty of states who don't give a crap about the health of their population, as long as the politicians get bribed through campaign financing. And if they can't find a state that will let them poison their own people, they'll find a whole country that will.