Bulgaria Pollution?

Just depends. Sofia is in a valley, sometimes there is an inversion layer that traps the nastiness, sometimes not. It's certainly not like China or something. Sofia is a city only people who have done no research about Bulgaria stay in anyway.

I spent several days in Sofia, enjoyed it very much, and at least at that time, never sensed that it was particularly polluted. Air seemed fine. I loved Bulgaria!

I've been to Sofia in September, never felt that it was any different to any other major city.

It may be the most polluted capital, but far from the most polluted city.

Anyway, we're not talking Asian levels of pollution here, like in China and India. It must be pretty bad for the locals who are constantly exposed to the pollution, but it won't be a huge effect on you if you're spending only a couple of days.

I've been to Sofia a couple of times and didnt notice it being any worse than Rome. Of course that's not a complement. Very interesting city, do some research before you go and you will find it fascinating. I dont think tourists spend enough time in Sofia. But after a couple of nights get out and see the rest of the country. Fascinating and beautiful country.

The Balkan capitals are generally polluted cities.Belgrade, Skopje and Sofia are known to be the worse.

Actually Belgrade and Sofia are pretty far down on the list. https://www.google.com/amp/s/www.dailymail.co.uk/news/article-6773899/amp/Worlds-polluted-capital-cities-revealed-Delhi-ranked-worst.html

Then again this one puts Sofia up higher on the list https://www.airvisual.com/

I've been to most of the Eastern European capitals and they aren't bad at all. That list compares capitals. I suspect there are worse cities in the West.