I don't mean this in a bad way but, have you visited other countries? I'm Spanish but lived for about half a year in Krakow, and the difference is just so stark I can't imagine skepticism. In winter the air smells burned. Fog is a phenomenon, sure, but what takes place most of winter in Krakow is not fog. It's just smoke.

I didn't know about any of this when I first travelled there, in fact when my boss at the time recommended I got a mask I thought he was paranoid or something. Absolutely not.