A) The wind DOES blow it around, here’s a really cool map that shows the realtime winds and smog patches.
B) Most of the smog in an area has been recently produced by the pollution source (factory, power planet, forest fire, cars, etc) it’s not building up over a very long time, usually a few days at most if the winds are really light.
When I eat a few dill pickles, my scalp tingles. It’s mostly a pleasant sensation.