IQAir's live ranking puts Dakar and Lahore ahead of Kolkata, while Delhi and Mumbai also feature among the world's 10 most polluted cities. Check the top 10 most polluted major cities and their AQI levels, according to IQAir's live ranking. Mumbai’s air quality is again raising concerns, with the city ranking third among the world’s most polluted cities in a global snapshot. Delhi stands second, while Pakistan’s Lahore tops the.