Editing Delhi (section)

== Geography ==
{{Main|Environment of Delhi}}
[[File:Delhi aerial photo 04-2016 img11.jpg|thumb|Aerial view of Delhi in April 2016 with river [[Yamuna]] in top-right]]
Delhi is located in [[North India|Northern India]], at {{coord|28.61|N|77.23|E}}. The city is bordered on its northern, western, and southern sides by the [[States and union territories of India|state]] of [[Haryana]] and to the east by that of [[Uttar Pradesh]] (UP). Two prominent features of the geography of Delhi are the Yamuna flood plains and the [[Delhi ridge]]. The [[Yamuna River]] was the historical boundary between [[Punjab]] and UP, and its flood plains provide fertile alluvial soil suitable for agriculture but, are prone to recurrent floods. The Yamuna, a sacred river in [[Hinduism]], is the only major river flowing through Delhi. The [[Hindon River]] separates Ghaziabad from the eastern part of Delhi. The Delhi ridge originates from the [[Aravalli Range]] in the south and encircles the west, northeast, and northwest parts of the city. It reaches a height of {{convert|318|m|abbr=on}} and is a dominant feature of the region.<ref name=gisridge>{{cite web |url=https://www.fig.net/resources/proceedings/fig_proceedings/fig_2002/Ts3-9/TS3_9_mohan.pdf |title=GIS-Based Spatial Information Integration, Modeling and Digital Mapping: A New Blend of Tool for Geospatial Environmental Health Analysis for Delhi Ridge |access-date=3 February 2007 |last=Mohan |first=Madan |date=April 2002 |work=Spatial Information for Health Monitoring and Population Management |publisher=FIG XXII International Congress |page=5 |url-status=live |archive-url=https://web.archive.org/web/20151222151705/https://www.fig.net/resources/proceedings/fig_proceedings/fig_2002/Ts3-9/TS3_9_mohan.pdf |archive-date=22 December 2015 }}</ref>

In addition to the wetlands formed by the Yamuna River, Delhi continues to retain over 500 ponds (wetlands < {{Convert|5|ha|abbr=in}}), that in turn support a considerable number of bird species.<ref name=":0">{{Cite journal |last1=Rawal |first1=Prakhar |last2=Kittur |first2=Swati |last3=Chatakonda |first3=Murali K. |last4=Sundar |first4=K.S. Gopi |date=2021 |title=Winter bird abundance, species richness and functional guild composition at Delhi's ponds: does time of day and wetland extent matter? |url=https://academic.oup.com/jue/article/7/1/juab001/6139341?searchresult=1 |journal=Journal of Urban Ecology |volume=7 |issue=1 |pages=Online first |doi=10.1093/jue/juab001 |doi-access=free |access-date=31 March 2021 }}</ref> Delhi's ponds, despite experiencing ecological deterioration due to garbage dumping and concretisation, support the largest number of bird species known to be using ponds anywhere in the world.<ref name=":1">{{Cite journal |last1=Rawal |first1=Prakhar |last2=Kittur |first2=Swati |last3=Chatakonda |first3=Murali K. |last4=Sundar |first4=K.S. Gopi |date=2021 |title=Capital ponds: Site-level habitat heterogeneity and management interventions at ponds regulate high landscape-scale bird diversity across a mega-city |url=https://www.sciencedirect.com/science/article/abs/pii/S0006320721002676 |journal=Biological Conservation |volume=260 |pages=109215 |doi=10.1016/j.biocon.2021.109215 |bibcode=2021BCons.26009215R |issn=0006-3207 |s2cid=237716829 |access-date=23 June 2021 |archive-date=24 June 2021 |archive-url=https://web.archive.org/web/20210624203639/https://www.sciencedirect.com/science/article/abs/pii/S0006320721002676 |url-status=live}}</ref> Existing policy in Delhi prevents the conversion of wetlands and, quite inadvertently, has led to the city's ponds becoming invaluable refugia for birds.<ref name=":0" /><ref name=":1" />

The National Capital Territory of Delhi covers an area of {{convert|1483|km2|sqmi|abbr=on}}, of which {{convert|783|km2|sqmi|abbr=on|0}} is designated rural, and {{convert|700|km2|sqmi|abbr=on|0}} urban therefore making it the largest city in terms of area in the country. It has a length of {{convert|51.9|km|mi|abbr=on|0}} and a width of {{convert|48.48|km|mi|abbr=on|0}}.{{citation needed|reason=Please also update [[List of cities in India by area]] when you add a citation|date=April 2018}} Delhi is included in India's [[Earthquake zones of India|seismic zone-IV]], indicating its vulnerability to major earthquakes.<ref name=hazardprofile>{{cite web |url=https://www.undp.org.in/dmweb/hazardprofile.pdf |title=Hazard profiles of Indian districts |access-date=23 August 2006 |work=National Capacity Building Project in Disaster Management |publisher=[[UNDP]] |archive-url=https://web.archive.org/web/20060519100611/https://www.undp.org.in/dmweb/hazardprofile.pdf |archive-date=19 May 2006}}</ref>

=== Climate ===
{{See also|Climate of Delhi}}
Delhi features a dry winter [[humid subtropical climate]] ([[Köppen climate classification|Köppen]] ''Cwa'') bordering a [[hot semi-arid climate]] ([[Köppen climate classification|Köppen]] ''BSh''). The warm season lasts from 21 March to 15 June with an average daily high temperature above {{convert|39|C|abbr=on}}. The hottest day of the year is usually witnessed between 26 and 30 May, with an average high of {{convert|42|C|abbr=on}} and low of {{convert|27|C|abbr=on}}.<ref name=weatherspark>{{cite web |title=Average weather for New Delhi, India |url=https://weatherspark.com/averages/33934/New-Delhi-India |publisher=Weatherspark.com |access-date=2 July 2013 |url-status=live |archive-url=https://web.archive.org/web/20130816202008/https://weatherspark.com/averages/33934/New-Delhi-India |archive-date=16 August 2013}}</ref> The cold season lasts from 26 November to 9 February with an average daily high temperature below {{convert|20|C|abbr=on}}. The coldest day of the year is usually witnessed between 1 and 10 January, with an average low of {{convert|6.9|C|abbr=on}} and high of {{convert|19.3|C|abbr=on}}.<ref name=weatherspark /> In early March, the wind direction changes from north-westerly to south-westerly. From April to October the weather is hot. The monsoon arrives at the end of June, along with an increase in humidity.{{Citation needed|date=June 2023}} The brief, mild winter starts in late November, peaks in January and heavy fog often occurs.<ref name=Fog>{{cite news |url=https://www.hindu.com/2005/01/07/stories/2005010719480300.htm |title=Fog continues to disrupt flights, trains |date=7 January 2005 |location=Chennai |url-status=dead |archive-url=https://web.archive.org/web/20060304160457/https://www.hindu.com/2005/01/07/stories/2005010719480300.htm |work=[[The Hindu]] |archive-date=4 March 2006}}</ref> Delhi receives an average annual precipitation of {{Convert|774.4|mm|abbr=on}}.<ref>{{cite news |last1=Agarwal |first1=Priyangi |date=20 August 2023 |title=4 months left, Delhi crosses annual rain quota |url=https://timesofindia.indiatimes.com/city/delhi/4-mths-left-city-crosses-annual-rain-quota/articleshow/102865895.cms |newspaper=The Times of India |access-date=10 December 2023 |archive-date=10 December 2023 |archive-url=https://web.archive.org/web/20231210042216/https://timesofindia.indiatimes.com/city/delhi/4-mths-left-city-crosses-annual-rain-quota/articleshow/102865895.cms |url-status=live }}</ref>

{{Clear}}

<div class="center">{{Delhi weatherbox}}</div>

=== Air pollution ===
{{See also|Environmental issues in Delhi|Air pollution in Delhi}}
[[File:Poulluted killer fog in Delhi.jpg|thumb|A dense toxic smog in Delhi blocking out the sun, November 2017]]

According to the [[World Health Organization]] (WHO), Delhi was the most polluted<ref>{{cite news |url=https://www.hindustantimes.com/india-news/delhi-has-dirtiest-air-china-data-foggy-who/article1-1216605.aspx |title=Delhi is most polluted city in world, Beijing much better: WHO study |work=Hindustan Times |access-date=8 May 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140508004750/https://www.hindustantimes.com/india-news/delhi-has-dirtiest-air-china-data-foggy-who/article1-1216605.aspx |archive-date=8 May 2014 }}</ref> city in the world in 2014. In 2016, WHO downgraded Delhi to eleventh-worst in the urban air quality database.<ref>{{cite web|url=https://www.digital-development-debates.org/issue-18-cities--delhi--fancy-schemes-for-a-dirty-business.html|title=Fancy Schemes for a Dirty Business|last=Kumar|first=Rahul|date=July 2016|website=Digital Development Debates|access-date=5 September 2016|url-status=live|archive-url=https://web.archive.org/web/20160915234747/https://www.digital-development-debates.org/issue-18-cities--delhi--fancy-schemes-for-a-dirty-business.html|archive-date=15 September 2016}}</ref> However, as recently as 2022, data from the WHO and IQAir, alongside comprehensive research, ranked Delhi as the fourth most polluted city globally.<ref>{{cite news |last1=Blinns |first1=Rob |date=5 September 2023 |title=Most polluted cities in the world {{!}} The Independent |url=https://www.independent.co.uk/advisor/solar-panels/polluted-cities-in-the-world |work=Independent Advisor |access-date=12 March 2024 |archive-date=12 March 2024 |archive-url=https://web.archive.org/web/20240312131052/https://www.independent.co.uk/advisor/solar-panels/polluted-cities-in-the-world |url-status=live }}</ref> According to one estimate, [[air pollution]] causes the death of about 10,500 people every year.<ref name="TimePollution">{{cite magazine |url=https://world.time.com/2014/02/10/smog-in-new-delhi/ |title=Delhi's Air Has Become a Lethal Hazard and Nobody Seems to Know What to Do About It |magazine=[[Time (magazine)|Time]] |access-date=10 February 2014 |date=10 February 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140302085642/https://world.time.com/2014/02/10/smog-in-new-delhi/ |archive-date=2 March 2014 }}</ref><ref name="VOAPollution">{{cite web |url=https://www.voanews.com/a/indias-air-pollution-triggers-comparisons-with-china/1855331.html |title=India's Air Pollution Triggers Comparisons with China |date=20 February 2014 |publisher=Voice of America |access-date=20 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140221104928/https://www.voanews.com/content/indias-air-pollution-triggers-comparisons-with-china/1855331.html |archive-date=21 February 2014 }}</ref><ref name="EconomistPollution">{{cite news|url=https://www.economist.com/blogs/banyan/2012/11/air-pollution-india|title=A Delhi particular|newspaper=The Economist|access-date=6 November 2012|date=6 November 2012|url-status=live|archive-url=https://web.archive.org/web/20121106114416/https://www.economist.com/blogs/banyan/2012/11/air-pollution-india|archive-date=6 November 2012}}</ref> [[Air quality index]] is generally moderate (101–200) level between January and September, and then it drastically deteriorates to Very Poor (301–400), Severe (401–500) or Hazardous (500+) levels in three months between October and December,<ref>{{cite news |last1=Chaman |first1=Vishakha |last2=Pal |first2=Ayantika |title=Out of here in November: In Delhi-NCR, smog break is becoming the new annual vacation |url=https://timesofindia.indiatimes.com/city/delhi/out-of-here-in-november-in-del-ncr-smog-break-is-becoming-the-new-annual-vacation/articleshow/104979257.cms |access-date=5 November 2023 |work=The Times of India |date=5 November 2023 |archive-date=5 November 2023 |archive-url=https://web.archive.org/web/20231105062436/https://timesofindia.indiatimes.com/city/delhi/out-of-here-in-november-in-del-ncr-smog-break-is-becoming-the-new-annual-vacation/articleshow/104979257.cms |url-status=live }}</ref><ref>{{cite news |title=Delhi AQI: CP Smog tower down due to DPCC, says minister Gopal Rai; official says running cost high |url=https://timesofindia.indiatimes.com/city/delhi/delhi-aqi-cp-smog-tower-down-due-to-dpcc-says-minister-gopal-rai-official-says-running-cost-high/articleshow/104978284.cms |access-date=5 November 2023 |work=The Times of India |date=5 November 2023 |archive-date=5 November 2023 |archive-url=https://web.archive.org/web/20231105062840/https://timesofindia.indiatimes.com/city/delhi/delhi-aqi-cp-smog-tower-down-due-to-dpcc-says-minister-gopal-rai-official-says-running-cost-high/articleshow/104978284.cms |url-status=live }}</ref> due to various factors including [[stubble burning]] (a type of [[Combustion of biomass|biomass burning]]), fire crackers burning during Diwali and cold weather.<ref>{{cite news|url=https://timesofindia.indiatimes.com/city/delhi/day-after-diwali-delhis-air-turns-hazardous/articleshow/66539912.cms|title=Pollution level in Delhi: Day after Diwali, Delhi's air turns 'hazardous'|website=[[The Times of India]]|date=8 November 2018 |access-date=8 November 2018|archive-url=https://web.archive.org/web/20181108173945/https://timesofindia.indiatimes.com/city/delhi/day-after-diwali-delhis-air-turns-hazardous/articleshow/66539912.cms|archive-date=8 November 2018|url-status=live}}</ref><ref>{{cite news|url=https://timesofindia.indiatimes.com/city/delhi/delhi-breathed-easier-from-january-to-april/articleshow/59011204.cms|title=Delhi breathed easier from January to April|website=[[The Times of India]]|date=6 June 2017 |access-date=8 November 2018|archive-url=https://web.archive.org/web/20181109070658/https://timesofindia.indiatimes.com/city/delhi/delhi-breathed-easier-from-january-to-april/articleshow/59011204.cms|archive-date=9 November 2018|url-status=live}}</ref><ref>{{cite web|url=https://www.hindustantimes.com/delhi-news/air-pollution-delhi-enjoys-cleanest-february-in-three-years/story-SANlmslHev8ifFgZbh3WXI.html|title=Air pollution: Delhi enjoys cleanest February in three years|date=27 February 2018|access-date=8 November 2018|archive-url=https://web.archive.org/web/20181109070735/https://www.hindustantimes.com/delhi-news/air-pollution-delhi-enjoys-cleanest-february-in-three-years/story-SANlmslHev8ifFgZbh3WXI.html|archive-date=9 November 2018|url-status=live}}</ref> During 2013–14, peak levels of fine [[particulate matter]] (PM) increased by about 44%, primarily due to high vehicular and industrial emissions, construction work and crop burning in adjoining states.<ref name="TimePollution" /><ref name="WSJPollution">{{cite news |url=https://blogs.wsj.com/indiarealtime/2014/02/15/how-crop-burning-affects-delhis-air-pollution/ |title=How Crop Burning Affects Delhi's Air |newspaper=The Wall Street Journal |access-date=15 February 2014 |date=15 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140306041835/https://blogs.wsj.com/indiarealtime/2014/02/15/how-crop-burning-affects-delhis-air-pollution/ |archive-date=6 March 2014 }}</ref><ref name="GARDINER, 25 January 14">{{cite news |last=Harris |first=Gardiner |title=Beijing's Bad Air Would Be Step Up for Smoggy Delhi |url=https://www.nytimes.com/2014/01/26/world/asia/beijings-air-would-be-step-up-for-smoggy-delhi.html |access-date=27 January 2014 |newspaper=The New York Times |date=25 January 2014 |url-status=live |archive-url=https://web.archive.org/web/20141103045801/https://www.nytimes.com/2014/01/26/world/asia/beijings-air-would-be-step-up-for-smoggy-delhi.html |archive-date=3 November 2014 }}</ref><ref name="BEARAK, 8 feb">{{cite news |last=Bearak |first=Max |title=Desperate for Clean Air, Delhi Residents Experiment with Solutions |url=https://india.blogs.nytimes.com/2014/02/07/desperate-for-clean-air-delhi-residents-experiment-with-solutions/?emc=edit_tnt_20140208&tntemail0=y |access-date=8 February 2014 |newspaper=The New York Times |date=7 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140222171648/https://india.blogs.nytimes.com/2014/02/07/desperate-for-clean-air-delhi-residents-experiment-with-solutions/?emc=edit_tnt_20140208&tntemail0=y |archive-date=22 February 2014 }}</ref> It has the highest level of the airborne particulate matter, [[PM2.5]] considered most harmful to health, with 153 micrograms.<ref>{{cite news |author=Madison Park |title=Top 20 most polluted cities in the world |url=https://www.cnn.com/2014/05/08/world/asia/india-pollution-who/index.html |publisher=CNN |date=8 May 2014 |url-status=live |archive-url=https://web.archive.org/web/20160508104416/https://www.cnn.com/2014/05/08/world/asia/india-pollution-who/index.html |archive-date=8 May 2016 }}</ref>

Rising air pollution level has significantly increased lung-related ailments (especially asthma and lung cancer) among Delhi's children and women.<ref name="TodayPollution">{{cite magazine |url=https://indiatoday.intoday.in/story/pollution-in-delhi-cng-children-in-delhi/1/344904.html |title=Children in Delhi have lungs of chain-smokers! |magazine=[[India Today]] |access-date=22 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140302000403/https://indiatoday.intoday.in/story/pollution-in-delhi-cng-children-in-delhi/1/344904.html |archive-date=2 March 2014 }}</ref><ref name="DNAPollution">{{cite web |url=https://www.dnaindia.com/health/report-pollution-increasing-lung-cancer-in-indian-women-1959054 |title=Pollution increasing lung cancer in Indian women |date=3 February 2014 |publisher=DNA |access-date=3 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140305181411/https://www.dnaindia.com/health/report-pollution-increasing-lung-cancer-in-indian-women-1959054 |archive-date=5 March 2014 }}</ref> The dense [[smog]] and [[haze]] during winter results in major air and rail traffic disruptions every year.<ref name="ReutersPollution">{{cite news |url=https://in.reuters.com/article/india-delhi-winter-smog-idINDEE9BH0D420131218 |title=Delhi blanketed in thick smog, transport disrupted |work=Reuters |access-date=18 December 2013 |date=18 December 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131220012916/https://in.reuters.com/article/2013/12/18/india-delhi-winter-smog-idINDEE9BH0D420131218 |archive-date=20 December 2013 }}</ref> According to Indian meteorologists, the average maximum temperature during winters has declined notably since 1998 due to rising air pollution.<ref>{{Cite news |date=27 January 2014 |title=January days getting colder, tied to rise in pollution |work=The Times of India |url=https://timesofindia.indiatimes.com/city/delhi/January-days-getting-colder-tied-to-rise-in-pollution/articleshow/29429495.cms |url-status=live |access-date= |archive-url=https://web.archive.org/web/20150904034839/https://timesofindia.indiatimes.com/city/delhi/January-days-getting-colder-tied-to-rise-in-pollution/articleshow/29429495.cms |archive-date=4 September 2015 |issn=0971-8257}}</ref>

India's [[Ministry of Earth Sciences]] published a research paper in October 2018 attributing almost 41% of PM2.5 air pollution in Delhi to vehicular emissions, 21.5% to dust/fire and 18% to industries.<ref name=MoES5>{{cite news|title=Usual suspects: Vehicles, industrial emissions behind foul play|url=https://timesofindia.indiatimes.com/city/delhi/usual-suspects-vehicles-industrial-emissions-behind-foul-play-all-year/articleshow/66228517.cms|access-date=18 December 2018|work=The Times of India|archive-url=https://web.archive.org/web/20181228212103/https://timesofindia.indiatimes.com/city/delhi/usual-suspects-vehicles-industrial-emissions-behind-foul-play-all-year/articleshow/66228517.cms|archive-date=28 December 2018|url-status=live}}</ref> The director of [[Centre for Science and Environment]] (CSE) alleged that the [[Automotive industry in India|Society of Indian Automobile Manufacturers]] (SIAM) is lobbying "against the report" because it is "inconvenient" to the automobile industry.<ref name=CSE>{{cite news|title=UA vicious nexus|url=https://www.downtoearth.org.in/blog/air/a-vicious-nexus-62475|access-date=18 December 2018|work=Down to Earth|archive-url=https://web.archive.org/web/20181213162118/https://www.downtoearth.org.in/blog/air/a-vicious-nexus-62475|archive-date=13 December 2018|url-status=live}}</ref> Environmentalists have also criticised the Delhi government for not doing enough to curb air pollution and to inform people about air quality issues.<ref name="VOAPollution" /> In 2014, an environmental panel appealed to India's Supreme Court to impose a 30% [[cess]] on diesel cars, but till date no action has been taken to penalise the automobile industry.<ref>{{Cite news |date=11 February 2014 |title=Impose 30% cess on diesel cars, panel tells Supreme Court |work=The Times of India |url=https://timesofindia.indiatimes.com/home/environment/pollution/Impose-30-cess-on-diesel-cars-panel-tells-Supreme-Court/articleshow/30180391.cms |url-status=live |archive-url=https://web.archive.org/web/20140304004249/https://timesofindia.indiatimes.com/home/environment/pollution/Impose-30-cess-on-diesel-cars-panel-tells-Supreme-Court/articleshow/30180391.cms |archive-date=4 March 2014 |issn=0971-8257}}</ref>

Most of Delhi's residents are unaware of alarming levels of air pollution in the city and the health risks associated with it.<ref name="GARDINER, 25 January 14" /><ref name="BEARAK, 8 feb" /> In 2020, annual average [[PM2.5]] in the city stood at 107.6&nbsp;μg/m<sup>3</sup>, which is almost 21.5 times the WHO's PM2.5 Guideline (5&nbsp;μg/m<sup>3</sup>; set in September 2021).<ref name="auto">{{Cite web |title=The Air Quality Life Index (AQLI) |url=https://aqli.epic.uchicago.edu/the-index/ |access-date=6 September 2022 |website=AQLI |language=en |archive-date=20 August 2020 |archive-url=https://web.archive.org/web/20200820013309/https://aqli.epic.uchicago.edu/the-index/ |url-status=live }}</ref> These pollution levels are estimated to reduce the [[life expectancy]] of an average person living in Delhi by almost 10.1 years.<ref name="auto"/>

However, {{As of|2015|lc=y}}, awareness, particularly among the foreign diplomatic community and high-income Indians, was noticeably increasing.<ref name="NYT021415">{{cite news|author1=Gardiner Harris|title=Delhi Wakes Up to an Air Pollution Problem It Cannot Ignore|url=https://www.nytimes.com/2015/02/15/world/asia/delhi-wakes-up-to-an-air-pollution-problem-it-cannot-ignore.html|access-date=15 February 2015|work=The New York Times|date=14 February 2015|url-status=live|archive-url=https://web.archive.org/web/20150215042638/https://www.nytimes.com/2015/02/15/world/asia/delhi-wakes-up-to-an-air-pollution-problem-it-cannot-ignore.html|archive-date=15 February 2015}}</ref> Since the mid-1990s, Delhi has undertaken some measures to curb air pollution—it has the third-highest quantity of trees among Indian cities;<ref>{{cite web |url=https://www.ndtv.com/news/cities/delhi_third_greenest_city.php |title=Delhi 'third greenest' city |publisher=Ndtv.com |access-date=11 March 2011 |url-status=live |archive-url=https://web.archive.org/web/20110213062310/https://www.ndtv.com/news/cities/delhi_third_greenest_city.php |archive-date=13 February 2011 }}</ref> the [[Delhi Transport Corporation]] operates the world's largest fleet of environmentally friendly [[compressed natural gas]] (CNG) buses.<ref name="cities.expressindia.com">{{cite web|url=https://cities.expressindia.com/fullstory.php?newsid=85665 |title=Express India |work=The Indian Express |access-date=11 March 2011 |url-status=dead |archive-url=https://web.archive.org/web/20101231054504/https://cities.expressindia.com/fullstory.php?newsid=85665 |archive-date=31 December 2010 }}</ref> In 1996, the CSE started a public interest litigation in the [[Supreme Court of India]] that ordered the conversion of Delhi's fleet of buses and taxis to run on CNG and banned the use of [[leaded petrol]] in 1998. In 2003, Delhi won the [[United States Department of Energy]]'s first 'Clean Cities International Partner of the Year' award for its "bold efforts to curb air pollution and support alternative fuel initiatives".<ref name="cities.expressindia.com" /> The [[Delhi Metro]] has also been credited for significantly reducing air pollutants in the city.<ref>{{Cite web |date=28 April 2013 |title=Delhi Metro helps reduce vehicular air pollution, indicates research |url=https://www.indiatoday.in/india/north/story/delhi-metro-helps-reduce-vehicular-air-pollution-delhi-school-of-economics-160315-2013-04-27 |url-status=live |archive-url=https://web.archive.org/web/20140301231933/https://indiatoday.intoday.in/story/delhi-metro-helps-reduce-vehicular-air-pollution-delhi-school-of-economics/1/268105.html |archive-date=1 March 2014 |access-date= |website=India Today |language=en}}</ref>

However, according to several authors, most of these gains have been lost, especially due to [[stubble burning]], a rise in the market share of [[diesel exhaust|diesel cars]] and a considerable decline in bus ridership.<ref name="kumari">{{cite journal |author1=R. Kumari |author2=A.K. Attri |author3=L. Int Panis |author4=B.R. Gurjar |title=Emission estimates of Particulate Matter and Heavy Metals from Mobile sources in Delhi (India) |journal=Journal of Environmental Science and Engineering |volume=55 |issue=2 |pages=127–142 |date=April 2013 |url=https://www.researchgate.net/publication/259827470 |url-status=live |archive-url=https://web.archive.org/web/20141108235156/https://www.researchgate.net/publication/259827470_Emission_estimates_of_Particulate_Matter_and_Heavy_Metals_from_Mobile_Sources_in_Delhi |archive-date=8 November 2014 |pmid= 25464689}}</ref><ref name="CSEPollution">{{cite web |url=https://cseindia.org/node/835 |title=What is the status of air pollution in Delhi? |publisher=CSE, India |access-date=2 March 2014 |url-status=live |archive-url=https://web.archive.org/web/20140301185410/https://cseindia.org/node/835 |archive-date=1 March 2014 }}</ref> According to CSE and System of Air Quality Weather Forecasting and Research (SAFAR), burning of agricultural waste in nearby Punjab, Haryana and Uttar Pradesh regions results in severe intensification of smog over Delhi.<ref name="ETTPollution">{{cite news |url=https://articles.economictimes.indiatimes.com/2014-11-06/news/55835957_1_pm-2-5-level-air-quality-weather-forecasting-pollution-levels |title=Delhi's air quality deteriorating due to burning of agriculture waste |newspaper=The Economic Times |date=6 November 2014 |access-date=8 November 2014 |archive-url=https://web.archive.org/web/20141111083702/https://articles.economictimes.indiatimes.com/2014-11-06/news/55835957_1_pm-2-5-level-air-quality-weather-forecasting-pollution-levels |archive-date=11 November 2014 |url-status=dead  }}</ref><ref name="CSE2Pollution">{{cite magazine |url=https://indiatoday.intoday.in/story/smog-delhi-winter-low-wind-speed-emissions/1/398601.html |title=Thick blanket of smog envelopes Delhi, northern India |magazine=India Today |url-status=live |archive-url=https://web.archive.org/web/20141105070407/https://indiatoday.intoday.in/story/smog-delhi-winter-low-wind-speed-emissions/1/398601.html |archive-date=5 November 2014 }}</ref>

Delhi has been ranked 7th best "National Clean Air City" (under Category 1 >10L Population cities) in India according to 'Swachh Vayu Survekshan 2024 Results' <ref>{{Cite web |date=7 September 2024 |title=Swachh Vayu Sarvekshan 2024 |url=https://prana.cpcb.gov.in/ncapServices/robust/fetchFilesFromDrive/Swachh_Vayu_Survekshan_2024_Result.pdf |website=Swachh Vayu Sarvekshan 2024 |access-date=19 September 2024 |archive-date=14 September 2024 |archive-url=https://web.archive.org/web/20240914164336/https://prana.cpcb.gov.in/ncapServices/robust/fetchFilesFromDrive/Swachh_Vayu_Survekshan_2024_Result.pdf |url-status=dead }}</ref>

According to the World Air Quality Report 2024, Delhi remains the world's most polluted capital city.<ref>{{Cite news |title=Delhi is most polluted city globally; 13 of world's 20 most polluted cities in India: report |url=https://www.thehindu.com/news/national/13-of-worlds-20-most-polluted-cities-in-india-delhi-most-polluted-capital/article69316060.ece |work=The Hindu |agency=PTI |issn=0971-751X |date=11 March 2025 |access-date=16 March 2025}}</ref>