but it's the worst for ozone, where it's 80's reputation for smog comes from. to be fair, LA's air quality is far better than the 74 major cities in chinaa: https://www.latimes.com/world/asia/la-fg-china-la-smog-stats...
which is where a significant portion of the air polution comes from (enough to go from good to bad): https://en.wikipedia.org/wiki/Air_pollution_in_the_United_St...