Delhi, Faridabad and Varanasi have the poorest air quality among the 32 Indian cities which are connected to the web-based system National Air Quality Index Portal.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/indian-cities-poorest-air-quality
[2] http://admin.indiaenvironmentportal.org.in/category/author/samarth-bansal
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu-new-delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/faridabad-t
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/varanasi-t
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-index-aqi
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pm-25
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rspm-pm-10
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[13] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health