KOLKATA: In the past two-and-ahalf years, Kolkata's air qualified as 'good' only once for a fortnight in August 2015.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/kolkata-air-quality-now-toxic-all-year
[2] http://admin.indiaenvironmentportal.org.in/category/author/subhro-niyogi
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-kolkata
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/west-bengal
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/kolkata
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-standards
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pm-25
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/heart-diseases
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects