Society · Environment · 1998–2026

Delhi Air Pollution Measures: What Actually Worked?

📅 Updated 19 October 2026🌫️ Annual AQI 209 to 201 in 2025⚠️ December 2025 averaged 351

Written & reviewed by Nazish Fatima · Updated October 19, 2026

In short

Delhi air pollution measures from the 1998 CNG order to odd-even, GRAP and the 2026 winter plan, scored on the evidence: what cut smog and what did not.

Latest Story

PoliticsWhy Seats Still Follow 1971What's really at stake here?BusinessFrom the 2G Row to 5GWhat's driving this market shift?BusinessThe Day the City Went GlobalWhat's driving this market shift?BusinessThe Pound That Lost 98%What's driving this market shift?Politics13 Demands, 1,310 Days, One DealWhat's really at stake here?

Delhi has tried almost everything: CNG buses, cleaner fuel, a Metro, odd-even car rationing, emergency bans, smog towers and even cloud seeding. Some Delhi air pollution measures changed how emissions are produced and delivered lasting gains; others gave a few days of relief or none at all. This timeline dates each major step from the 1998 CNG order to the 2026 winter plan and scores it on what the evidence shows, not on how loudly it was announced.

Quick Answers Timeline Score a Measure AQI Chart Scorecard Sources GRAP Stages Winter 2026 FAQ

💡 Short Answer

The measures that worked best in Delhi changed emissions every day: the court-ordered switch of buses, autos and taxis to CNG (1998–2002), cleaner fuel and BS-VI vehicles, the Metro and the closure of coal plants inside the city. Emergency tools such as odd-even and GRAP curbs gave limited, short-lived relief. Delhi’s annual AQI improved from 225 in 2018 to 201 in 2025, but December 2025 still averaged 351.

⚡ Delhi Air Pollution Measures: Quick Facts

Annual AQI 2025201 (209 in 2024)

Severe days 20258 (17 in 2024)

PM2.5 average 202596 μg/m³

CNG orderSupreme Court, 28 July 1998

Odd-even effect4–16% PM2.5, Jan 2016 only

Top winter sourceSecondary particles, 27%

⚡ Quick Answers — AI Overview Ready

Delhi’s Air Pollution Measures: Key Questions

Which Delhi pollution measures actually worked?

Structural ones. The CNG switch for public transport, cleaner fuel and BS-VI vehicle standards, the Metro and the closure of the Badarpur coal plant cut emissions every day of the year. Studies and official data credit these with Delhi’s gradual improvement, from an annual AQI of 225 in 2018 to 201 in 2025.

Did odd-even reduce pollution?

Only a little, and only in winter. Estimates for January 2016 range from a 4–6% fall in PM2.5 to 14–16% during scheme hours; the April 2016 round showed no clear effect. Pollution rebounded 57% within a day of the January round ending, so it works at best as a short emergency measure.

Is GRAP effective?

As an emergency brake, partly. Its four stages curb construction, trucks, generators and some vehicles as the AQI rises, and since 2022 it acts on forecasts. But Delhi still had 17 severe days in 2024 and 8 in 2025, because GRAP cannot remove the regional and year-round sources that build up in winter.

What is Delhi doing in winter 2026?

A Winter Action Plan from 1 November 2026 to 31 January 2027 bars non-BS-VI vehicles from outside Delhi, requires 50% work from home, doubles parking fees and halts construction from 10 December to 20 January. A ‘No PUCC, No Fuel’ rule has applied at about 500 pumps since 1 October.

📚 Key Takeaways

What Three Decades of Clean-Air Policy Show

Structural beats seasonal: measures that change fuels, vehicles and power plants have delivered the most lasting gains.
CNG was the first big win: ordered on 28 July 1998 and completed for buses by 2002.
BS-VI is the quiet one: cleaner fuel in Delhi from 2018 and BS-VI vehicles nationwide from April 2020.
Odd-even was limited: 4–16% lower PM2.5 in January 2016, no clear effect in April.
GRAP is a brake, not a cure: notified in January 2017, forecast-based since October 2022.
Gimmicks disappointed: smog towers (2021) and cloud seeding (2025) showed little or no effect.
2025 was better on average: AQI 201, the best since 2018 outside the 2020 lockdown.
But winter still wins: December 2025 averaged 351, and GRAP Stage IV returned twice.
Sources are many: winter PM2.5 is about 27% secondary particles, 23% transport, 20% biomass burning.
The 2026 test: 211 clean-air days by mid-October, with the winter plan and ‘No PUCC, No Fuel’ now in force.

The Timeline: From the CNG Order to the 2026 Winter Plan

Newest first. Tags mark structural measures, emergency measures, institutions, data and the 2026 chapter.

17 Oct
2026

211 clean-air days so far 2026

Good to moderate AQI on 211 days this year200 in the same period of 2025, 110 in 2016Poor-or-worse days down from 168 (2016) to 79

Environment Minister Manjinder Singh Sirsa called the 101-day gain over 2016 a collective achievement but warned that winter is the real test. These figures cover January to mid-October, before the months when Delhi’s air is usually at its worst, so the full-year result may look different.

1 Oct
2026

‘No PUCC, No Fuel’ goes city-wide 2026

About 500 fuel stations with number-plate camerasNo petrol, diesel, CNG or LPG without a valid pollution certificateSimilar rules in NCR districts of UP, Haryana and Rajasthan

Cameras read each number plate at the pump and check the vehicle’s Pollution Under Control Certificate against the national database; if it has lapsed, fuel is refused until the owner gets a fresh test. It is an enforcement measure for rules that already existed, aimed at the poorly maintained vehicles that emit far more than their share.

30 Sep
2026

Rain is not a solution, CSE finds Data

Only 1 ‘good’ air day in the 92-day monsoon, on 9 July576.9 mm of rainPM2.5 up 10.7% within 24 hours and 37.9% within 48 hours after rain stopped

The Centre for Science and Environment’s analysis found that rain cut PM2.5 by about 19.5% while it fell, but the washout did not last. Ground-level ozone, which forms in sunlight from vehicle and industrial gases, was the leading pollutant on about 20 monsoon days. Even in the cleanest season, most days were only ‘moderate’.

28 Sep
2026

Winter Action Plan 2026–27 Emergency

1 November 2026 to 31 January 2027Non-BS-VI vehicles from outside Delhi barred from 1 November50% work from home, staggered office hours, doubled parking feesTotal construction ban 10 December to 20 January

The plan also adds 150 electric buses, taking the e-bus fleet past 700, fitness tests for about 2.5 lakh vehicles at automated testing stations and weekly inspections of 37 pollution hotspots. Many measures are seasonal, but the bus fleet and vehicle testing are lasting changes. Whether the work-from-home and construction rules are enforced will decide how much they help.

Feb
2026

A clearer picture of where the pollution comes from Institution

CAQM synthesis of 2015–2025 source studiesWinter PM2.5: secondary particles 27%, transport 23%, biomass burning 20%, dust 15%, industry 9%46 new monitoring stations approved, taking NCR to 157

The new stations are split between Delhi (14), Haryana (16), Uttar Pradesh (15) and Rajasthan (1), and are meant to cover suburbs, industrial zones and border areas where pollution enters and leaves the city. The commission also considered tighter particulate standards for industry and stronger dust rules. A fresh emissions inventory involving IIT Delhi and ARAI was commissioned.

Dec 2025–
Jan 2026

GRAP Stage IV, again Emergency

Stage IV invoked on 13 December 2025 and again in January 2026December 2025 averages an AQI of 351Severe days still occur despite a better year

A cold, still December undid much of the year’s progress: the month was the most polluted of 2025, and the strictest curbs, on trucks, construction and in-person schooling, returned twice within five weeks. It is the clearest example of how weather can overwhelm emission controls in winter.

2025

Best annual average in seven years, barring 2020 Data

Annual AQI 201, down from 209 in 2024PM2.5 96 μg/m³, PM10 197, lowest since 20208 severe days, down from 1779 good-to-satisfactory days, up from 66

The government’s year-end review credited coordinated action under the CAQM. February and July were the cleanest of their months since 2018. But the number of days with an AQI below 200 actually fell, from 209 to 200, a reminder that a lower average can hide a worse spread. The figures show outcomes, not which measure caused them.

Oct
2025

Cloud seeding trial Emergency

Trials with IIT Kanpur over parts of Delhi on 28 OctoberClouds held too little moistureNo significant rain followed

Artificial rain had been discussed for years as a quick fix. The trial showed its limits: it needs the right clouds, which are rare in a dry Delhi winter, and even real rain only cleans the air for a day or two, as the CSE’s 2026 analysis later confirmed.

Jul
2025

Old-vehicle fuel ban paused within days Emergency

From 1 July 2025 pumps were told to refuse fuel to end-of-life vehicles (diesel over 10 years, petrol over 15)Put on hold after public protests and technical problems

The age limits themselves date from a 2014 National Green Tribunal order upheld by the Supreme Court in 2018. Enforcing them at the pump proved difficult: the cameras were not yet working everywhere, and owners argued that age is a poor proxy for emissions. The 2026 ‘No PUCC, No Fuel’ rule targets actual test results instead.

18 Nov
2024

AQI hits 494 Emergency

GRAP Stage IV in forceSchools moved online2024 ends with 17 severe-to-severe-plus days

A combination of farm fires, a temperature inversion and calm winds sent Delhi’s 24-hour AQI to 494, one of the highest on record. The Supreme Court criticised the delay in invoking Stage IV and ordered that it stay in force until the court allowed it to be relaxed.

1 Oct
2022

GRAP becomes forecast-based Institution

Revised GRAP by the CAQMMeasures triggered three days ahead using AQI forecastsThresholds tied to AQI bands, not raw PM levels

The original plan reacted once the air had already turned severe. The revision aimed to act before the peak, for example banning construction or diesel generators when a severe spell was forecast. It made the system faster, but the pollution it responds to still comes from sources outside its emergency reach.

Aug
2021

The CAQM gets a law; smog towers open Institution

Commission for Air Quality Management Act passed by ParliamentFirst smog tower opens at Connaught Place on 23 August 2021Second at Anand Vihar in September

The commission, first created by an ordinance in October 2020, replaced the court-appointed EPCA with a statutory body covering Delhi and the NCR states plus Punjab. The smog towers drew more headlines but far less evidence: monitoring suggested any benefit was confined to the area around each tower, and the idea was not scaled up.

Mar–May
2020

Lockdown shows what activity does to the air Data

Traffic, construction and most industry halt2020 annual AQI 185, the lowest of 2018–2025Gains vanish as activity resumes

Skies cleared visibly in spring 2020. But it was not a controlled experiment: the weather also changed, and secondary particles from sources outside Delhi kept forming. The episode proved that emissions matter, not that shutting down the economy is a pollution policy.

1 Apr
2020

India jumps from BS-IV to BS-VI Structural

New vehicles must meet BS-VI emission norms nationwideDelhi already had BS-VI fuel from 1 April 2018Diesel particulate and NOx limits sharply cut

India skipped BS-V entirely. The benefit is permanent but gradual: it grows as older vehicles are scrapped, which is why the 2026 winter plan bars non-BS-VI vehicles from outside Delhi and why enforcement of fitness and pollution certificates matters.

10 Jan
2019

National Clean Air Programme Institution

Target: 20–30% less particulate pollution by 2024 against 2017Later revised to up to 40% PM10 reduction by 2025–26City action plans for Delhi and more than 100 other cities

The NCAP made air quality a standing national priority with funding tied to results. Its targets are measured in PM10, which is heavily affected by dust, so progress on PM10 does not always mean progress on the finer, more harmful PM2.5.

15 Oct
2018

Badarpur coal plant closes for good Structural

NTPC’s 705 MW coal plant shut permanentlyHad been closed temporarily during earlier smog emergenciesDelhi left with no coal power plant inside its borders

Badarpur was one of Delhi’s largest single industrial sources of particulates and sulphur dioxide. Its closure, together with the earlier shutdown of the Rajghat plant in 2015, removed coal burning for power from the city itself, though plants in the wider NCR continue to operate.

2018

Cleaner fuel and a truck bypass Structural

BS-VI petrol and diesel in Delhi from 1 April 2018Eastern Peripheral Expressway opens on 27 May 2018, diverting through-trucksSupreme Court upholds 10- and 15-year age limits in October

The bypass, together with the Western Peripheral Expressway, gave heavy trucks bound elsewhere a way around the city instead of through it, while an environment compensation charge on trucks entering Delhi, in place since 2015, added a financial nudge.

12 Jan
2017

GRAP notified Emergency

Graded Response Action Plan notified by the environment ministry on the Supreme Court’s directionFour stages from ‘moderate to poor’ to ‘severe plus’First enforced in the winter of 2017

GRAP gave the region a rulebook for emergencies: pre-agreed actions, from road sweeping to bans on construction and diesel generators, that kick in as pollution worsens. It replaced improvised responses with a common framework, but by design it acts only on emergencies, not on the everyday emissions that set the baseline.

Nov
2016

The post-Diwali smog Data

Days of ‘severe’ air after Diwali on 30 OctoberSchools closed, construction halted, Badarpur temporarily shutCalled the worst smog in nearly two decades

The crisis, with PM2.5 readings far above anything the scale was designed for, pushed the Supreme Court and the Centre to formalise emergency planning. Within weeks the court asked for a graded plan, which became GRAP.

Smog over Rajpath in New Delhi on 6 November 2015, two months before the first odd-even trial. Photo: juggadery, CC BY-SA 2.0, via Wikimedia Commons.

Jan & Apr
2016

The odd-even experiment Emergency

First round 1–15 January 2016, second 15–30 AprilPrivate cars allowed on alternate days by number plate, with many exemptionsA third round followed on 4–15 November 2019

Evidence on the January round was mixed. A multi-institution study estimated PM2.5 fell by only 4–6%, while EPIC researchers estimated 14–16% during scheme hours. Both found no clear effect in April. CSE recorded bus and Metro ridership up 7–8% and lower peaks during the scheme, but PM2.5 jumped 57% within 24 hours of it ending.

6 Apr
2015

National Air Quality Index launched Institution

One number and six colour bands for eight pollutantsDaily bulletins for Delhi and other citiesThe basis for GRAP’s stages

The AQI turned scattered monitoring data into a figure the public could follow, and later into legal triggers for action. Measurement alone does not cut emissions, but it made the problem impossible to ignore and gave policy a scoreboard.

May
2014

WHO names Delhi the most polluted city Data

WHO ambient air database ranks Delhi first worldwide for PM2.5Annual average of 153 μg/m³ in the data usedNational attention shifts to fine particles

The ranking, disputed at the time by Indian officials, focused public debate on PM2.5 rather than coarser dust and helped drive the measures that followed, from the AQI to the odd-even trial.

24 Dec
2002

The Delhi Metro opens Structural

First stretch from Shahdara to Tis HazariNetwork grows to about 400 km across the NCRRooftop solar and regenerative braking cut its own emissions

The Metro is a long-term structural measure: its pollution benefit depends on how many trips it takes away from cars and two-wheelers, which in turn depends on last-mile connections and bus feeders. The 2026 winter plan’s exemption of Metro parking from doubled fees reflects that aim.

A Delhi Metro Pink Line train at Anand Vihar ISBT. The Metro’s first stretch opened in December 2002. Photo: Kool Nerd 123, CC BY 4.0, via Wikimedia Commons.

28 Jul
1998

The Supreme Court orders CNG Structural

M.C. Mehta v. Union of IndiaWhole bus fleet to move to CNG by 31 March 2001Autos and taxis followEPCA formed in January 1998 to oversee it

The deadline was missed amid fuel shortages and resistance from transport operators; the court imposed penalties and by the end of 2002 Delhi’s buses ran on CNG. Combined with lower-sulphur fuel, older-vehicle bans and the relocation of polluting industries, it was the city’s first big structural clean-up.

A Delhi Transport Corporation CNG bus. The court-ordered switch from diesel, completed by 2002, gave Delhi one of the world’s largest CNG bus fleets. Photo: Ramesh NG, CC BY-SA 2.0, via Wikimedia Commons.

🧪 Interactive: Score a Measure

Pick a measure to see what the evidence says it achieved, and where it fell short.

Verdict–

What it did–

The limit–

Delhi’s Annual AQI, 2018–2025

An 11% improvement from 2018 to 2025, but the annual average has hovered around the ‘poor’ threshold every year except the 2020 lockdown.

2025 vs 2024: Better on Average, Not Everywhere

Indicator	2024	2025	Change
Annual average AQI	209	201	Better
Average PM2.5 (μg/m³)	about 104	96	Better; lowest since 2020
Average PM10 (μg/m³)	about 212	197	Better; lowest since 2020
Good-to-satisfactory days (AQI 0–100)	66	79	Better
Days with AQI below 200	209	200	Worse
Severe-to-severe-plus days (AQI 401+)	17	8	Better
December average AQI	–	351	Very poor

The annual numbers improved on almost every measure, and severe days halved. But the count of days below an AQI of 200 slipped, and the year ended with its worst month. The government’s own review describes outcomes; it does not show which measure caused them, and weather varies a lot from one winter to the next. The 2024 particulate figures are approximate.

What Actually Worked? An Evidence-Based Scorecard

Measure	Assessment	Why
CNG transition and cleaner fuels	Strong structural contribution	Cut emissions from the vehicles it covered and set a lasting clean-fuel requirement
BS-VI standards and fuel	Strong long-term potential	Tighter limits for every new vehicle; real-world gains depend on fleet turnover and compliance
Metro and public transport	Strong potential	Reduces private-vehicle trips where capacity, frequency and last-mile links are good
Coal power plant closures	Strong, local	Removed large point sources inside Delhi; NCR plants remain
Odd-even restrictions	Limited and temporary	Some traffic reduction; evidence of large citywide PM2.5 cuts is mixed
GRAP	Useful emergency response	Curbs selected activities in severe spells; does not replace prevention
Construction and road-dust control	Necessary, enforcement-dependent	A major source, especially in warmer months; must be continuous
Crop-residue and biomass control	Necessary regional measure	A big seasonal contributor, but not the only cause of winter smog
More monitoring stations	Essential enabling step	Better diagnosis and accountability; does not cut emissions by itself
Smog towers and cloud seeding	Weak or unproven	Local or short-lived effects at best
Rain and favourable winds	Temporary natural relief	Lowers readings without removing any source

Where Delhi’s PM2.5 Comes From

🌡️ Interactive: Winter vs Summer Sources

Switch seasons to see how the estimated sources of Delhi’s PM2.5 change.

Secondary particles–

Transport–

Biomass burning–

Dust–

Industry incl. power–

CAQM synthesis of 2015–2025 source-apportionment studies. Shares are study averages and vary by day, place and method; the listed categories do not add up to 100%.

The CAQM’s synthesis explains why single-sector fixes fail. In winter no source makes up more than about a quarter of the pollution, and the largest share, secondary particles, forms in the air from gases released by vehicles, power plants, industry and farms, often outside Delhi. In summer, dust leads. A plan that targets only cars, or only farm fires, can at best move one of these numbers.

How GRAP Works

GRAP stage	AQI	Typical measures
Stage I	201–300 (poor)	Dust control at sites, ban on open burning, PUC checks, ban on coal and firewood in eateries
Stage II	301–400 (very poor)	Diesel generator curbs, higher parking fees, more buses and Metro trips
Stage III	401–450 (severe)	Ban on most construction and demolition, curbs on older petrol and diesel cars, hybrid classes for schools
Stage IV	Above 450 (severe plus)	Ban on non-essential trucks entering Delhi, all construction stopped, offices at 50%, schools online

Simplified from the CAQM’s revised schedule; each stage includes all measures of the stages below it, and the commission adjusts the list most years.

Winter 2026–27: What Is in Force

Winter Action Plan 2026–27	Detail
Period	1 November 2026 to 31 January 2027
Vehicles	Non-BS-VI vehicles from outside Delhi barred from 1 November; ‘No PUCC, No Fuel’ at about 500 pumps from 1 October
Offices	50% work from home; staggered hours (MCD 8:30–5, Delhi government 10–6:30)
Construction	Dust-generating demolition and outdoor work barred; total ban 10 December to 20 January
Transport	150 more electric buses, fleet past 700; parking fees doubled except at Metro sites
Enforcement	Weekly hotspot inspections at 37 sites; daily evening AQI bulletins; citizen reporting

Five Measures Most Likely to Deliver Lasting Improvement

1. Transport

Cut vehicle emissions every day

Faster fleet turnover to BS-VI and electric, real enforcement of pollution certificates, and buses and Metro feeders good enough to replace car trips.

2. Dust

Control it at the source

Covered materials, site barriers, paved and maintained roads and mechanised sweeping, all year, not just when GRAP is invoked.

3. Industry and power

Act across the NCR

Continuous emissions monitoring, cleaner industrial fuels and controls on the sulphur and nitrogen gases that form secondary particles.

4. Crop residue

A year-round regional programme

Machines, markets for straw and support for farmers in Punjab and Haryana, alongside, not instead of, action in the city.

5. Accountability

Targets for every source

Named agencies, sector-wise targets, public reporting and evaluation against a weather-adjusted baseline, rather than counting announcements.

What the Evidence Rules Out

Blaming one source: no single sector made up more than 27% of winter PM2.5 in the CAQM’s study.
Reading one year as proof: a cleaner year can come from kinder weather; a bad December does not erase real progress.
Waiting for rain: PM2.5 rose 37.9% within 48 hours of rain stopping in the 2026 monsoon.
Air purifiers for a city: smog towers clean a neighbourhood at best.
Lockdowns as policy: 2020 showed the effect of activity, not a usable strategy.

Explore More Timelines

TechnologyHow Much of Your Old Smartphone Can Actually Be Recycled?Where is this technology headed?SocietyAir Quality and Environmental Awareness in India…Why does this matter right now?SocietyHow Did They Reach Mumbai?Why does this matter right now?SocietyGrenfell Tower: The Failures Behind the 2017 DisasterWhy does this matter right now?SocietyWho sends the headlines first?Why does this matter right now?

Frequently Asked Questions

Did the odd-even scheme solve Delhi’s air pollution?

No. The January 2016 trial produced mixed results: one multi-institution study estimated a PM2.5 fall of only 4–6%, which it did not consider significant, while researchers at the Energy Policy Institute at the University of Chicago estimated 14–16% during the hours the rule applied. The April 2016 round showed no measurable effect, and pollution rebounded as soon as each round ended.

Which measure made the biggest difference to Delhi’s air quality?

No single measure can take the credit. The strongest evidence supports structural changes that cut emissions every day: the switch of buses, autos and taxis to CNG from 1998 to 2002, cleaner fuel and the leap to BS-VI vehicles, the closure of coal power plants such as Badarpur and the steady growth of the Metro. Emergency curbs help in a crisis but do not shift the annual average much.

Is crop burning the main cause of Delhi’s pollution?

Not over the whole year. Farm fires in Punjab and Haryana can dominate on some days in late October and November, but the CAQM’s 2026 synthesis of studies put biomass burning, which includes crop residue and waste, at about 20% of winter PM2.5 and 12% in summer. Secondary particles, vehicles, dust and industry together contribute far more.

What is GRAP?

The Graded Response Action Plan is a set of emergency measures that tighten in four stages as the air worsens: Stage I at an AQI of 201–300, Stage II at 301–400, Stage III at 401–450 and Stage IV above 450. It was notified on 12 January 2017 and, since October 2022, is invoked by the CAQM in advance based on forecasts.

Did Delhi’s air quality improve in 2025?

On the main annual measures, yes. The average AQI fell from 209 in 2024 to 201, PM2.5 averaged 96 micrograms per cubic metre, the lowest since 2020, and severe days fell from 17 to 8. But December 2025 averaged an AQI of 351, and the number of days with AQI below 200 fell slightly, from 209 to 200.

What were Delhi’s AQI levels each year since 2018?

According to the government’s year-end review, Delhi’s annual average AQI was 225 in 2018, 215 in 2019, 185 in the 2020 lockdown year, 209 in 2021 and 2022, 204 in 2023, 209 in 2024 and 201 in 2025. That is an improvement of about 11% from 2018 to 2025, but every year stayed in the ‘poor’ band or close to it.

Why did the Supreme Court order Delhi’s buses to switch to CNG?

In the M.C. Mehta case, the court on 28 July 1998 accepted the recommendations of the newly formed Environment Pollution (Prevention and Control) Authority and ordered the city’s bus fleet to move to CNG by 31 March 2001. Diesel buses were a major source of soot. The deadline was missed and the court enforced it with penalties; the bus fleet completed the switch by late 2002.

Did the CNG switch actually reduce pollution?

Studies found it cut some pollutants, especially from the vehicles it covered, and that the package of CNG, cleaner fuel, older-vehicle bans and the relocation of some industry improved air quality in the early 2000s. The gains were later eroded by rapid growth in private cars and diesel vehicles, so CNG is best seen as a lasting foundation rather than a cure.

Do smog towers work?

Not at city scale. Delhi’s two smog towers, at Connaught Place and Anand Vihar, opened in August and September 2021. Monitoring suggested they cleaned the air only in their immediate surroundings, and air-quality experts argued that the money was better spent on cutting emissions at source. They were not expanded.

Has cloud seeding been tried in Delhi?

Yes. The Delhi government carried out cloud-seeding trials with IIT Kanpur in October 2025, but the clouds held too little moisture and no significant rain followed. Scientists point out that even successful artificial rain only washes out pollution for a day or two; the CSE’s 2026 analysis found PM2.5 rose 37.9% within 48 hours after natural rain stopped.

What is the CAQM?

The Commission for Air Quality Management in the National Capital Region and Adjoining Areas is a statutory body created by an ordinance in October 2020 and the Commission for Air Quality Management Act passed by Parliament in August 2021. It replaced the court-appointed EPCA and can issue binding directions to Delhi, Haryana, Uttar Pradesh, Rajasthan and Punjab.

What did the CAQM’s 2026 source study find?

Its synthesis of source-apportionment studies from 2015 to 2025 estimated that winter PM2.5 in Delhi came from secondary particles (27%), transport (23%), biomass burning (20%), dust (15%) and industry including power plants (9%). In summer, dust led at 27%, followed by transport (19%), secondary particles (17%), industry (14%) and biomass burning (12%).

What are secondary particles?

They are fine particles that are not emitted directly but form in the air when gases such as sulphur dioxide, nitrogen oxides and ammonia react. Their sources include vehicles, power plants, industry and farming, often far from Delhi. Because they made up the largest share of winter PM2.5 in the CAQM’s study, cutting gases across the region matters as much as cutting smoke and dust.

Did the Covid-19 lockdown clean Delhi’s air?

It reduced it sharply. During the lockdown from late March 2020 traffic, construction and much industry stopped, and 2020 had the lowest annual average AQI of recent years, 185. But weather and regional sources also changed, and the improvement vanished as activity resumed. The lockdown showed how much human activity matters, not a usable policy.

When did BS-VI fuel arrive in Delhi?

Delhi switched to BS-VI petrol and diesel on 1 April 2018, two years ahead of the rest of the country. The national move straight from BS-IV to BS-VI vehicle standards took effect on 1 April 2020. BS-VI diesel vehicles emit far less particulate matter and nitrogen oxides than older models, but the benefit grows only as old vehicles leave the roads.

Why was the Badarpur power plant closed?

The coal-fired Badarpur Thermal Power Station, run by NTPC in south-east Delhi, was among the city’s largest single industrial polluters. It was shut temporarily during smog emergencies and closed permanently on 15 October 2018. Delhi no longer has a coal-fired power plant within its borders, though several operate in the wider NCR.

What is the National Clean Air Programme?

Launched on 10 January 2019, the NCAP set a goal of cutting particulate pollution in more than 100 non-attainment cities, including Delhi, by 20–30% by 2024 against 2017 levels. The target was later revised to a reduction of up to 40% in PM10 by 2025–26. It funds city action plans and is linked to performance.

What is Delhi’s Winter Action Plan 2026–27?

Announced in late September 2026, it runs from 1 November 2026 to 31 January 2027. It includes a ban on non-BS-VI vehicles registered outside Delhi from 1 November, 50% work from home for offices, staggered office timings, doubled parking fees except at Metro stations, curbs on dusty construction and a total construction ban from 10 December to 20 January.

What is the ‘No PUCC, No Fuel’ rule?

From 1 October 2026 the Delhi government enforced a rule that vehicles without a valid Pollution Under Control Certificate cannot buy petrol, diesel, CNG or LPG. Cameras with automatic number-plate recognition at about 500 fuel stations check each vehicle against the national database. Fines of up to ₹10,000 also apply, and NCR districts in neighbouring states follow similar rules.

How many clean-air days has Delhi had in 2026?

According to Environment Minister Manjinder Singh Sirsa, Delhi had recorded 211 days in the good, satisfactory or moderate bands by mid-October 2026, compared with 200 in the same period of 2025 and 110 in 2016. The coming winter months, when pollution usually peaks, will decide whether 2026 ends as the cleanest recent year.

What did the CSE find about rain and pollution in 2026?

The Centre for Science and Environment found that Delhi had only one ‘good’ air day in the 92-day monsoon of 2026, despite 576.9 mm of rain. PM2.5 fell during rain but rose 10.7% within 24 hours and 37.9% within 48 hours after it stopped. Ground-level ozone was the leading pollutant on about 20 monsoon days.

Why is Delhi’s winter so polluted?

In winter, cold air near the ground is trapped under warmer air, a temperature inversion, and winds are weak, so pollutants build up instead of dispersing. Crop-residue fires, Diwali firecrackers and more heating and waste burning add to emissions at the same time. The same emissions in summer would cause far less damage because the air mixes much higher.

What can residents do during a pollution emergency?

Follow the health advice issued with each GRAP stage: limit outdoor exercise when the AQI is ‘very poor’ or worse, use well-fitted N95 masks outdoors, keep vulnerable people indoors and use public transport where possible. Reporting burning or dust through official apps such as Green Delhi helps enforcement. Anyone with breathing or heart problems should follow medical advice.

Conclusion: Clean Air Needs Structural Change, Not Just Winter Bans

Delhi’s record shows that pollution control works when it changes how emissions are produced. Cleaner fuels, stricter vehicle standards, mass transit and the end of coal power inside the city have delivered gains that last; temporary restrictions have mostly delivered headlines. Regional coordination and better monitoring are now in place, and dust and biomass burning need steady, unglamorous enforcement.

The real test is simple: can Delhi keep its air cleaner when the rain stops, the winds drop and winter arrives? The winter of 2026–27, with its 211-day head start, will be the next measure.

Sources & further reading

Every dated entry above was checked against these references. Last reviewed 19 October 2026.