New Delhi, Kolkata and Mumbai are among the top 20 most polluted cities in the world in terms of PM2.5 levels, according to the latest State of Global Air report on air quality and health in cities. While New Delhi and Kolkata rank first and second, respectively, Mumbai stands 14th on the list. The study ranked cities on the basis of two major air pollutants found - fine particulate matter (PM2.5) and nitrogen dioxide (NO2). PM2.5 is an atmospheric particulate matter of diameter of fewer than 2.5 micrometres, which is around 3 per cent the diameter of a human hair. It causes respiratory problems and reduces visibility. Meanwhile, road traffic is among the primary outdoor contributors of NO2, long exposure to which is linked to deaths. There were no Indian cities in the top 20 in terms of population-weighted NO2 exposures in 2019. Shanghai, Moscow and Tehran are the top three cities in this list. The Air Quality and Health in Cities report, published by the State of Global Air, is a collaboration between the US-based Health Effects Institute (HEI) and the Institute for Health Metrics and Evaluation’s Global Burden of Disease Project. As per the report, the highest population-weighted annual average PM2.5 exposure in 2019 was in Delhi at 110 μg/m3, followed by Kolkata at 84 μg Here is the list of the top 20 most polluted cities in the world (PM2.5) with the PM2.5 levels in μg/m3: Delhi, India (110) Kolkata, India (84) Kano, Nigeria (83.6) Lima, Peru (73.2) Dhaka, Bangladesh (71.4) Jakarta, Indonesia (67.3) Lagos, Nigeria (66.9) Karachi, Pakistan (63.6) Beijing, China (55) Accra, Ghana (51.9) Chengdu, China (49.9) Singapore, Singapore (49.4) Abidjan, Côte d’Ivoire (47.4) Mumbai, India (45.1) Bamako, Mali (44.2) Shanghai, China (40.1) Dushanbe, Tajikistan (39.7) Tashkent, Uzbekistan (38) Kinshasa, Democratic Republic of the Congo (35.8) Cairo, Egypt (34.2)
