Praja has gathered the data of air quality through an Right to Information query to the Central Pollution Control Board.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/mumbai%E2%80%99s-air-getting-worse-day-day-ngo
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/asian-age-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/maharashtra
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mumbai
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ngo
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/right-information-rti
[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