Lack of calibration of pollution-measuring instruments has been hampering efforts of the country's pollution watchdog to come out with accurate data on air pollution.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/air-quality-index-doesnt-give-you-correct-picture
[2] http://admin.indiaenvironmentportal.org.in/category/author/vishwa-mohan
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/council-scientific-and-industrial-research-csir
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-monitoring
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-index-aqi
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb-0