Sources: What Delhi Breathes

Where to start

Gani, S., Bhandari, S., Seraj, S., Wang, D. S., Patel, K., Soni, P., Arub, Z., Habib, G., Hildebrandt Ruiz, L. & Apte, J. S. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmospheric Chemistry and Physics 19, 6843–6859 (2019). The clearest measured account of why Delhi's winter air is chemically and meteorologically different from its summer air.
Sharma, M. & Dikshit, O. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi — Final Report: Air Pollution Component. IIT Kanpur, submitted to the Department of Environment, Govt of NCT of Delhi and DPCC, January 2016. The Delhi government's own source study; read the executive summary for winter versus summer.
ARAI & TERI. Source Apportionment of PM2.5 & PM10 Concentrations of Delhi NCR for Identification of Major Sources — Executive Summary (draft). Prepared for the Department of Heavy Industry, August 2018. The second major source study; its method section explains why its numbers differ from IIT Kanpur's.
Central Pollution Control Board. National Air Quality Index (IND-AQI), report of the Expert Group. CPCB, October 2014. How India's AQI was designed, with the breakpoint tables and the reasoning behind the ‘maximum’ rule.
India State-Level Disease Burden Initiative Air Pollution Collaborators. Health and economic impact of air pollution in the states of India: the Global Burden of Disease Study 2019. The Lancet Planetary Health 5(1), e25–e38 (2021; online 22 December 2020). The most-cited state-by-state estimate of air pollution's health and economic toll in India.
Energy Policy Institute at the University of Chicago (EPIC). Air Quality Life Index — India Fact Sheet 2025 (2023 data). A different method for the same question, expressed in years of life; read its method note.
Cherrie, J. W., Apsley, A., Cowie, H., Steinle, S., Mueller, W., Lin, C., Horwell, C. J., Sleeuwenhoek, A. & Loh, M. Effectiveness of face masks used to protect Beijing residents against particulate air pollution. Occupational and Environmental Medicine 75(6), 446–452 (2018). A short, practical test showing that masks fail mostly at the face seal, not the filter.
UrbanEmissions.Info. India NCAP – Air Quality Index (AQI) in Indian Cities 2015–2023. Updated March 2024. Ten years of every Indian city's daily AQI, compiled from the bulletins; the raw material behind this site's calendar.

A year in Delhi's air: every day of 2024

Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
CPCB. Air Quality Index on Nov 01, 2024 @ 4 PM (daily bulletin), including notes and the “Health Statements for AQI Categories” colour table. cpcb.nic.in/upload/Downloads/AQI_Bulletin_20241101.pdf. Accessed 24 October 2026.
UrbanEmissions.Info. India NCAP – Air Quality Index (AQI) in Indian Cities 2015–2023. Updated March 2024. urbanemissions.info/india-air-quality/india-ncap-aqi-indi…. Accessed 24 October 2026.
Dammalapati, S. K. & Guttikunda, S. (UrbanEmissions.Info). AQI_bulletins: AQI Analysis for Indian Cities from 2015 to 2023 (code and data repository, GPL-3.0). GitHub. github.com/urbanemissions-info/AQI_bulletins. Accessed 24 October 2026.

What is PM2.5, and what else is in Delhi's air?

Indian Economic Service, Arthapedia. “National Air Quality Index”. ies.gov.in/arthapedia/concept/national-air-quality-index. Accessed 24 October 2026.
US Environmental Protection Agency. Particulate Matter (PM) Basics (archived snapshot, 19 January 2025). 19january2025snapshot.epa.gov/pm-pollution/particulate-ma…. Accessed 24 October 2026.
Sharma, M. & Dikshit, O. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi — Final Report: Air Pollution Component. IIT Kanpur, submitted to the Department of Environment, Govt of NCT of Delhi and DPCC, January 2016. cerca.iitd.ac.in/uploads/Reports/1576211826iitk.pdf. Accessed 24 October 2026.
Gani, S., Bhandari, S., Seraj, S., Wang, D. S., Patel, K., Soni, P., Arub, Z., Habib, G., Hildebrandt Ruiz, L. & Apte, J. S. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmospheric Chemistry and Physics 19, 6843–6859 (2019). doi.org/10.5194/acp-19-6843-2019. Accessed 24 October 2026.
US EPA. Basic Information about NO2. epa.gov/no2-pollution/basic-information-about-no2. Accessed 24 October 2026.
US EPA. Ground-level Ozone Basics. epa.gov/ground-level-ozone-pollution/ground-level-ozone-b…. Accessed 24 October 2026.
Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
US EPA. Sulfur Dioxide Basics. epa.gov/so2-pollution/sulfur-dioxide-basics. Accessed 24 October 2026.
US EPA. Basic Information about Carbon Monoxide (CO) Outdoor Air Pollution. epa.gov/co-pollution/basic-information-about-carbon-monox…. Accessed 24 October 2026.
Committee on the Medical Effects of Air Pollutants (COMEAP). Statement: response to publication of the World Health Organization air quality guidelines 2021. UK Government, 27 July 2022. gov.uk/government/publications/comeap-statement-response-…. Accessed 24 October 2026.
World Health Organization. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. WHO, 22 September 2021. ISBN 9789240034228. who.int/publications/i/item/9789240034228. Accessed 24 October 2026.

How do you read India's AQI?

Central Pollution Control Board. National Air Quality Index (IND-AQI), report of the Expert Group. CPCB, October 2014. smartnet.niua.org/sites/default/files/resources/Air%20Qua…. Accessed 24 October 2026.
Indian Economic Service, Arthapedia. “National Air Quality Index”. ies.gov.in/arthapedia/concept/national-air-quality-index. Accessed 24 October 2026.
Lok Sabha, Starred Question No. 109, answered 28 July 2015 (Ministry of Environment, Forests and Climate Change). eparlib.nic.in/bitstream/123456789/665803/1/20011.pdf. Accessed 24 October 2026.
CPCB. Air Quality Index on Nov 01, 2024 @ 4 PM (daily bulletin), including notes and the “Health Statements for AQI Categories” colour table. cpcb.nic.in/upload/Downloads/AQI_Bulletin_20241101.pdf. Accessed 24 October 2026.
Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
US Environmental Protection Agency. Final Updates to the Air Quality Index (AQI) for Particulate Matter — Fact Sheet. February 2024 (breakpoints effective 6 May 2024). epa.gov/system/files/documents/2024-02/pm-naaqs-air-quali…. Accessed 24 October 2026.
Central Pollution Control Board. National Air Quality Monitoring Programme report for 2019 (lists the National Ambient Air Quality Standards notified 18 November 2009). static.pib.gov.in/WriteReadData/userfiles/NAAQS.pdf. Accessed 24 October 2026.
Committee on the Medical Effects of Air Pollutants (COMEAP). Statement: response to publication of the World Health Organization air quality guidelines 2021. UK Government, 27 July 2022. gov.uk/government/publications/comeap-statement-response-…. Accessed 24 October 2026.
World Health Organization. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. WHO, 22 September 2021. ISBN 9789240034228. who.int/publications/i/item/9789240034228. Accessed 24 October 2026.
Rajpurohit, S. “Exclusive: Delhi AQI data is unreliable – air monitors flout norms, blocked by trees”. Newslaundry, 31 December 2024. newslaundry.com/2025/03/21/2024/12/31/exclusive-delhi-aqi…. Accessed 24 October 2026.

Where does Delhi's pollution come from?

Sharma, M. & Dikshit, O. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi — Final Report: Air Pollution Component. IIT Kanpur, submitted to the Department of Environment, Govt of NCT of Delhi and DPCC, January 2016. cerca.iitd.ac.in/uploads/Reports/1576211826iitk.pdf. Accessed 24 October 2026.
ARAI & TERI. Source Apportionment of PM2.5 & PM10 Concentrations of Delhi NCR for Identification of Major Sources — Executive Summary (draft). Prepared for the Department of Heavy Industry, August 2018. teriin.org/sites/default/files/2018-08/AQM-SA_0.pdf. Accessed 24 October 2026.
TERI. “Strong policies needed to clean Delhi NCR air by 2025: ARAI & TERI report” (press release), 16 August 2018. teriin.org/press-release/strong-policies-needed-clean-del…. Accessed 24 October 2026.
Centre for Research on Energy and Clean Air (CREA). India Monthly Air Quality Snapshot — November 2025 (press release), December 2025. energyandcleanair.org/wp/wp-content/uploads/2025/12/CREA_…. Accessed 24 October 2026.

Why is Delhi's air worse in winter?

Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
US National Weather Service, Louisville. Temperature Inversions. weather.gov/lmk/inversion. Accessed 24 October 2026.
Gani, S., Bhandari, S., Seraj, S., Wang, D. S., Patel, K., Soni, P., Arub, Z., Habib, G., Hildebrandt Ruiz, L. & Apte, J. S. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmospheric Chemistry and Physics 19, 6843–6859 (2019). doi.org/10.5194/acp-19-6843-2019. Accessed 24 October 2026.
ARAI & TERI. Source Apportionment of PM2.5 & PM10 Concentrations of Delhi NCR for Identification of Major Sources — Executive Summary (draft). Prepared for the Department of Heavy Industry, August 2018. teriin.org/sites/default/files/2018-08/AQM-SA_0.pdf. Accessed 24 October 2026.
Sharma, M. & Dikshit, O. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi — Final Report: Air Pollution Component. IIT Kanpur, submitted to the Department of Environment, Govt of NCT of Delhi and DPCC, January 2016. cerca.iitd.ac.in/uploads/Reports/1576211826iitk.pdf. Accessed 24 October 2026.
Centre for Research on Energy and Clean Air (CREA). India Monthly Air Quality Snapshot — November 2025 (press release), December 2025. energyandcleanair.org/wp/wp-content/uploads/2025/12/CREA_…. Accessed 24 October 2026.
Roychowdhury, A. & Kaur, S. Post-stubble pollution: year-end analysis. Centre for Science and Environment, 31 December 2025. cseindia.org/Year-end-Post-stubble-pollution-Dec2025.pdf. Accessed 24 October 2026.
PRS Legislative Research. The Commission for Air Quality Management in National Capital Region and Adjoining Areas Bill, 2021 (bill track). prsindia.org/billtrack/the-commission-for-air-quality-man…. Accessed 24 October 2026.
Business Today. “Delhi AQI: Two days after Diwali, AQI remains ‘very poor’”, 2 November 2024. businesstoday.in/amp/india/story/delhi-aqi-two-days-after…. Accessed 24 October 2026.

What does the government do? GRAP, CAQM and NCAP

Commission for Air Quality Management in NCR and Adjoining Areas. Graded Response Action Plan (GRAP) for the National Capital Region — schedule, revision dated 29.09.2026. caqm.nic.in/FileUploadDomain/WebsiteDocument/GRAP/GRAP%20…. Accessed 24 October 2026.
PRS Legislative Research. The Commission for Air Quality Management in National Capital Region and Adjoining Areas Bill, 2021 (bill track). prsindia.org/billtrack/the-commission-for-air-quality-man…. Accessed 24 October 2026.
Press Information Bureau. “CAQM revises GRAP schedule, making it more stringent to prevent further deterioration of air quality in Delhi–NCR”, 22 November 2025. pib.gov.in/PressReleasePage.aspx?PRID=2192852&reg=3&lang=2. Accessed 24 October 2026.
Ministry of Environment, Forest and Climate Change / PIB. Swachh Vayu Diwas and the National Clean Air Programme (backgrounder), 24 September 2024. static.pib.gov.in/WriteReadData/specificdocs/documents/20…. Accessed 24 October 2026.
CPCB. Air Quality Index on Nov 01, 2024 @ 4 PM (daily bulletin), including notes and the “Health Statements for AQI Categories” colour table. cpcb.nic.in/upload/Downloads/AQI_Bulletin_20241101.pdf. Accessed 24 October 2026.
Rajpurohit, S. “Exclusive: Delhi AQI data is unreliable – air monitors flout norms, blocked by trees”. Newslaundry, 31 December 2024. newslaundry.com/2025/03/21/2024/12/31/exclusive-delhi-aqi…. Accessed 24 October 2026.

What does air pollution do to health?

World Health Organization. Ambient (outdoor) air pollution — fact sheet, 24 October 2024. who.int/news-room/fact-sheets/detail/ambient-(outdoor)-ai…. Accessed 24 October 2026.
Committee on the Medical Effects of Air Pollutants (COMEAP). Statement: response to publication of the World Health Organization air quality guidelines 2021. UK Government, 27 July 2022. gov.uk/government/publications/comeap-statement-response-…. Accessed 24 October 2026.
World Health Organization. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. WHO, 22 September 2021. ISBN 9789240034228. who.int/publications/i/item/9789240034228. Accessed 24 October 2026.
India State-Level Disease Burden Initiative Air Pollution Collaborators. Health and economic impact of air pollution in the states of India: the Global Burden of Disease Study 2019. The Lancet Planetary Health 5(1), e25–e38 (2021; online 22 December 2020). doi.org/10.1016/S2542-5196(20)30298-9. Accessed 24 October 2026.
Energy Policy Institute at the University of Chicago (EPIC). Air Quality Life Index — India Fact Sheet 2025 (2023 data). aqli.epic.uchicago.edu/files/India%20FactSheet_2025_India…. Accessed 24 October 2026.

What actually helps at home?

Cherrie, J. W., Apsley, A., Cowie, H., Steinle, S., Mueller, W., Lin, C., Horwell, C. J., Sleeuwenhoek, A. & Loh, M. Effectiveness of face masks used to protect Beijing residents against particulate air pollution. Occupational and Environmental Medicine 75(6), 446–452 (2018). doi.org/10.1136/oemed-2017-104765. Accessed 24 October 2026.
Lu, F. T., Laumbach, R. J., Legard, A. et al. Real-World Effectiveness of Portable Air Cleaners in Reducing Home Particulate Matter Concentrations. Aerosol and Air Quality Research 24(1) (2024). doi.org/10.4209/aaqr.230202. Accessed 24 October 2026.
Vyas, S., Srivastav, N. & Spears, D. An Experiment with Air Purifiers in Delhi during Winter 2015–2016. PLoS ONE 11(12): e0167999 (2016). doi.org/10.1371/journal.pone.0167999. Accessed 24 October 2026.

Which Delhi air myths don't hold up?

Wolverton, B. C., Johnson, A. & Bounds, K. Interior Landscape Plants for Indoor Air Pollution Abatement. NASA Technical Memorandum NASA-TM-101766, 15 September 1989. ntrs.nasa.gov/citations/19930073077. Accessed 24 October 2026.
Cummings, B. E. & Waring, M. S. Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies. Journal of Exposure Science & Environmental Epidemiology 30, 253–261 (2020; online November 2019). doi.org/10.1038/s41370-019-0175-9. Accessed 24 October 2026.
Down To Earth. “Smog towers ineffective; at least 40,000 needed in Delhi to combat toxic air, DPCC tells NGT”, 16 November 2023. downtoearth.org.in/amp/story/pollution/smog-towers-ineffe…. Accessed 24 October 2026.
Centre for Research on Energy and Clean Air (CREA). India Monthly Air Quality Snapshot — November 2025 (press release), December 2025. energyandcleanair.org/wp/wp-content/uploads/2025/12/CREA_…. Accessed 24 October 2026.
Roychowdhury, A. & Kaur, S. Post-stubble pollution: year-end analysis. Centre for Science and Environment, 31 December 2025. cseindia.org/Year-end-Post-stubble-pollution-Dec2025.pdf. Accessed 24 October 2026.
Sharma, M. & Dikshit, O. Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi — Final Report: Air Pollution Component. IIT Kanpur, submitted to the Department of Environment, Govt of NCT of Delhi and DPCC, January 2016. cerca.iitd.ac.in/uploads/Reports/1576211826iitk.pdf. Accessed 24 October 2026.
Deccan Herald. “Monsoon has arrived in Delhi, says IMD”, 28 June 2024. deccanherald.com/amp/story/india%2Fdelhi%2Fmonsoon-has-ar…. Accessed 24 October 2026.
PTI via The Week. “Delhi faces rain fury, records highest rainfall in 88 years”, 28 June 2024. theweek.in/wire-updates/national/2024/06/28/del110-dl-2nd…. Accessed 24 October 2026.
Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
Gani, S., Bhandari, S., Seraj, S., Wang, D. S., Patel, K., Soni, P., Arub, Z., Habib, G., Hildebrandt Ruiz, L. & Apte, J. S. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmospheric Chemistry and Physics 19, 6843–6859 (2019). doi.org/10.5194/acp-19-6843-2019. Accessed 24 October 2026.

How do you read Delhi's live air data yourself?

Central Pollution Control Board. National Air Quality Index portal (station-wise AQI). airquality.cpcb.gov.in/AQI_India/. Accessed 24 October 2026.
Central Pollution Control Board. Sameer — India's AQI (mobile app listing). apps.apple.com/in/app/sameer-indias-aqi/id1186664744. Accessed 24 October 2026.
CPCB. Air Quality Index on Nov 01, 2024 @ 4 PM (daily bulletin), including notes and the “Health Statements for AQI Categories” colour table. cpcb.nic.in/upload/Downloads/AQI_Bulletin_20241101.pdf. Accessed 24 October 2026.
Central Pollution Control Board (CPCB). Daily AQI Bulletins, 1 January – 31 December 2024 (366 PDFs, “Air Quality Index … @ 4 PM, average of past 24 hours”). Ministry of Environment, Forest and Climate Change, 2024. cpcb.nic.in/AQI_Bulletin.php. Accessed 24 October 2026.
UrbanEmissions.Info. India NCAP – Air Quality Index (AQI) in Indian Cities 2015–2023. Updated March 2024. urbanemissions.info/india-air-quality/india-ncap-aqi-indi…. Accessed 24 October 2026.
Delhi Pollution Control Committee. Real-time ambient air quality data portal. dpccairdata.com/dpccairdata/display/index.php. Accessed 24 October 2026.
Indian Institute of Tropical Meteorology, Ministry of Earth Sciences. SAFAR — System of Air Quality and Weather Forecasting And Research. safar.tropmet.res.in/. Accessed 24 October 2026.
Rajpurohit, S. “Exclusive: Delhi AQI data is unreliable – air monitors flout norms, blocked by trees”. Newslaundry, 31 December 2024. newslaundry.com/2025/03/21/2024/12/31/exclusive-delhi-aqi…. Accessed 24 October 2026.
Gani, S., Bhandari, S., Seraj, S., Wang, D. S., Patel, K., Soni, P., Arub, Z., Habib, G., Hildebrandt Ruiz, L. & Apte, J. S. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmospheric Chemistry and Physics 19, 6843–6859 (2019). doi.org/10.5194/acp-19-6843-2019. Accessed 24 October 2026.
Central Pollution Control Board. National Air Quality Index (IND-AQI), report of the Expert Group. CPCB, October 2014. smartnet.niua.org/sites/default/files/resources/Air%20Qua…. Accessed 24 October 2026.
US Environmental Protection Agency. Final Updates to the Air Quality Index (AQI) for Particulate Matter — Fact Sheet. February 2024 (breakpoints effective 6 May 2024). epa.gov/system/files/documents/2024-02/pm-naaqs-air-quali…. Accessed 24 October 2026.