NGL, it was still this nasty into the early 70's when I was a child. Palo Alto in the 70's was hardly smog free..There were days where we'd have smog alerts and the schools would keep us inside - the classrooms all had heavy vinyl curtain walls set up between every two rooms - so the teachers could open the rooms up and make one big class and we'd push our desks to the sides of the room and we could hang out and play for recess.. You could also watch the sunset w/o needing glasses, the sky would be so brown at times.. It was gross.