@skyfaller I grew up not far from the Lehigh Valley Velodrome. I can remember some of the cyclists wearing either balaclavas or masks in smog season. Most didn't but nobody seemed to care about people who chose to protect themselves from particulates back then.
@oreoteeth When was smog season back then? I assume summer because of heat domes and similar weather phenomena, but I suppose it could also be related to some local industrial process with some other logic to it. Was it regular and predictable? Do you remember smog season not being a thing anymore at some point?