Try 3city (Gańsk-Sopot-Gdynia up north on Baltic). Definitely better air quality then in other places in Poland. Do not know how it compares to other European cities though.
I'm Polish and I left because of the air quality. But, 15 years passed, and it got much better (obs. through holiday visits). People no longer heat with trash and coal isn't less of an option. Also, it isn't as cold in the winter so there is less need for heavy heating. Really thinking of coming back, to family.
It's getting better year by year but I suspect it'll take another decade before we'll have acceptable air quality during the heating season. During earmer seasons it's fine tho.