@skyfaller July and August for the most part in the 70s and early 80s. The radio station with all the weather gadgets that used to do the local measurement was bought out somewhere around the mid 80s when I was at college. So I can't say if the air quality improved or not. It was just that people stopped checking it.
@oreoteeth Then would you say that it's odd they're still wearing masks in November, then? Would this have been after smog season?
Are they wearing the masks to make a point about how increasing bicycle use would reduce smog, rather than for practical reasons because it was actually smoggy that day?
This post has a pic of a 1977 protest, could be the same one? Nobody is wearing a mask because they are singing, although one man to the right has a mask under his chin: https://bicyclecoalition.org/launching-in-the-70s-the-bicycle-coalitions-first-decade/
@oreoteeth Then would you say that it's odd they're still wearing masks in November, then? Would this have been after smog season?
Are they wearing the masks to make a point about how increasing bicycle use would reduce smog, rather than for practical reasons because it was actually smoggy that day?