Along this line, for many years now, people from Japan and China have been wearing masks.
Long before covid19. They knew something Americans didn't know?
They live in a sh*thole city and know firsthand how bad the air pollution can get.
Walk around in downtown Bangkok. Then you'll know what they know: they can't breathe without filtering out all the gas fumes -- especially during rush hour!!
It's the same in Seoul, S. Korea and I'm sure in many other countries in that part of the world.