Question raised in Lok Sabha on List of Most Polluted Cities, 22/11/2016. The methodology for calculation of pollution index in various parts of world is not same. Cities can be ranked on the basis of different criteria pollutants with different results. An ambient air pollution database released by the World Health Organisation in May 2016
indicates that 10 Indian cities fall among top 20 most polluted cities in the world in respect of PM2.5 (particulate matter) which is based on extrapolation of data relating to PM10 to arrive at PM2.5 data based on conversion factors in respect of cities where PM2.5 data is not measured. Therefore, care has to be exercised before drawing any inference. The names of Indian cities with concentration of PM2.5 reported by WHO and level of air pollution with available Air Quality Index monitored by CPCB is annexed.