The World Health Organisation has listed Delhi under the worst places in the world due to its high pollution levels.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/3-home-remedies-fight-delhi%E2%80%99s-nasty-air-pollution
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/respiratory-diseases
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/immunisation
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health