Comparing between Indian cities on levels of particulate matter PM10 and the more harmful PM2.5, Delhi features in the top lists in India.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/gwalior-most-polluted-indian-city-not-delhi-who-report
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/madhya-pradesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/gwalior-t
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rspm-pm-10
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pm-25
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fossil-fuels
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vehicular-pollution