It's a sad state of affairs in major Polish cities. Out of the 4 major tech hubs: Warsaw, Krakow, Wroclaw, 3-city (Gdansk/Sopot/Gdynia which form one long city) air is terrible in all with the exception of 3-city. Even there it's not so rosy (depends on the area, some are very clean, some not so much but air pollution stations are too sparse to show it). I moved out because of it and I wouldn't advise anyone to live in Poland (outside 3-city) if they have other options. It's not worth it to risk your health.

The situation is terrible for many reasons but major 2 are ancient coal/junk heating (people won't upgrade to eco-friendly heating because most of them are dirty poor and their main problem is to find a cheaper coal substitute for next winter) and Germans flooding us with used diesel cars with particulate filters long not working (or removed). There is a lot of talk about CO2 but this is long term danger while used diesel cars are poisoning us right now at massive scale.

It is literally the worst in Europe at the moment. It's a huge issue over there.

In Krakow? Has it changed a lot in the past years? I was there in 2014 and the air was great.