Flying into Los Angeles on an extremely clear day. The distant mountains are at least 50 miles away.
When I grew up in LA (the 60’s and 70’s) we had over 120 Stage 1 Smog Alerts per year – that meant that you shouldn’t play outside and you needed to curtail any unnecessary driving. At school, PE was cancelled. There would be 10 or so Stage 2 days each year where it was hazardous just to breath, so that was discouraged too. I remember days when you couldn’t see a block away, and maybe one day a year that looked like this.
Since 2003 there have been zero Stage 1 days.