Environmental scientists say ozone, which is a particularly critical pollutant, has emerged as a concern in Delhi in the last few years.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/toxic-ozone-gas-double-safe-limit-some-delhi-areas
[2] http://admin.indiaenvironmentportal.org.in/category/author/pritha-chatterjee
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ozone-layer
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-index-aqi
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nitrogen-dioxide
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/centre-science-and-environment-cse
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/atmosphere-and-ozone-layer