To add to that, I spent a lot of time in Los Angeles during the 80s and remember coming over the Grapevine to see a soup-like atmosphere above the valley, resembling this
Now, when I make the same drive there's a bit of smog, but it's nothing like it used to be. More people, but during the 80s there were still an awful lot of carbureted cars with non-catalyst exhaust systems flatulating all sorts of leaden vapors into the air. These days if I get behind some old carbureted junker I notice it because unlike all the modern cars on the road, I can actually smell its exhaust funk. The past sucked, for real.