Most global cities far exceed World Health Organisation’s (WHO) air pollution guidelines, posing serious health risks, with Delhi and Kolkata figuring as top two most polluted cities in terms of being exposed to hazardous fine particulate matter (PM2.5) whereas Shanghai in China and Moscow in Russia figured as top two most polluted for being exposed to nitrogen dioxide (NO2), said a new report released by the US-based Health Effects Institute’s (HEI) State of Global Air Initiative on Wednesday.