In winter time, almost every evening, from 6:00 PM through the night. Except for windy days (from ~7 m/s upwards), which are pretty rare.

It's all because of the old Soviet heavy industry which hasn't been properly maintained since 1991 (say what you want about USSR, but there was more responsibility then), crappy gasoline, lots of old cars which made their first 100k miles in Germany or US, high sulfur coal being used in stoves... the whole shebang.

Did I mention that some people use cow dung/rubber/plastic rubbish in their stoves?

Yep, we're living on the same planet as you are.