I used this source: https://en.wikipedia.org/wiki/List_of_most-polluted_cities_by_particulate_matter_concentration. Baku does not make the top 500. Looking at another source, Numbeo, it rates Baku's air pollution level at 72.62 which is classed as high. By comparison though, it lists Karachi, which is 19 on this list as having an air pollution level of 78.18.