Delhi has earned the dubious tag of being India’s most polluted city, rising from rank 3 in 2019 and rank 2 last year in the worst-polluted list, as per the National Clean Air Programme (NCAP) Tracker based on annual PM2.5 levels measured by the Central Pollution Control Board.Delhi has earned the dubious tag of being India’s most polluted city, rising from rank 3 in 2019 and rank 2 last year in the worst-polluted list, as per the National Clean Air Programme (NCAP) Tracker based on annual PM2.5 levels measured by the Central Pollution Control Board.