Delhi's air is no doubt polluted and gains from CNG have been frittered away. But the air in some residential areas can be far more toxic than we imagine.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/toxic-metals-air-jnu-study
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/toxic-wastes
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/heavy-metals
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/lead
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rspm-pm-10