world most polluted cities
1 Delhi is most polluted city in the world in PM2.5 concentrations. 2  Half of the top 20 most polluted cities were in India, according to data.  PM2.5 is considered most harmful to health.
Lucknow, India (annual mean PM2.5, ug/m3: 96) The capital city of Uttar Pradesh is among the most polluted cities in the country. The lack of transport infrastructure and growing number of vehicles exacerbates the problem, according to India's Centre for Science and Environment.