Archive · 31 Dec 2025
Delhi's Severe Air Pollution and Fog
Delhi is experiencing very poor air quality with high levels of PM2.5 pollution.
This pollution is partly due to secondary aerosols formed from gases like sulfur dioxide and ammonia, which come from coal power plants and farming.
The air quality has been especially bad this December, with pollution levels not seen since 2018.
Dense fog is also causing low visibility, leading to delays and cancellations in flights.
Authorities are advising people to check flight statuses and be prepared for travel disruptions.
Experts say that reducing these gases is crucial to improving air quality.
Delhi's Air Quality Index (AQI) remains in the 'very poor' category at 381, with some areas crossing 400.
December 2025 saw the highest PM2.5 levels since 2018, averaging 211 µg/m³ for the month.
Dense fog and low visibility have caused delays and cancellations in flight operations at Indira Gandhi International Airport.
Airlines like IndiGo and Air India have issued advisories, warning passengers of potential disruptions.
Secondary aerosols, formed from precursor gases like sulfur dioxide and ammonia, contribute significantly to PM2.5 pollution.
- Who
- Residents of Delhi and nearby regions, air travelers
- What
- Severe air pollution and dense fog affecting visibility and health
- When
- December 31, 2025, and throughout December 2025
- Where
- Delhi and surrounding states like Chhattisgarh, Odisha, Jharkhand, and Telangana
- Why
- Due to high levels of PM2.5 pollution and meteorological conditions causing dense fog
Environmentalists
Industrial and Agricultural Lobby
Primary Pollution Sources
Environmentalists
Environmentalists argue that the primary sources of pollution, such as coal-fired power plants and agricultural activities, need immediate regulation to reduce precursor gases like sulfur dioxide and ammonia.
Industrial and Agricultural Lobby
The industrial and agricultural lobby contends that strict regulations will harm economic activities and suggest a more gradual approach to pollution control.
- Air Quality Index (AQI)
- 381 (Very Poor)
- PM2.5 Levels
- 211 µg/m³ (December 2025 average)
- High Pollution Days
- One out of three days in December 2025 crossed 250 µg/m³ citywide
- Flight Operations
- Operating under CAT III protocols due to dense fog
- Affected Areas
- Delhi-NCR and several airports in northern India
- Meteorological Conditions
- Dense fog and low visibility
- Secondary Aerosol Contribution
- 49% of PM2.5 during post-monsoon, 41% in winter, 21% in summer and monsoon
- Ammonium Sulfate Contribution
- Nearly one-third of Delhi’s annual PM2.5 load
Sources
A third of Delhi’s annual PM2.5 load is made up of secondary pollutants. This is how they are formed
"Wall-To-Wall" Paving, Mist Sprayers: Inside Delhi's Plan To Curb Pollution
Delhi records highest PM2.5 this month since Dec 2018
Delhi AQI Remains ‘Very Poor’ as Dense Fog Reduces Visibility; Check Flight Status and AQI in Your Area
Dense Fog Blankets Delhi-NCR; Airlines Warn Flyers Of Delays, Cancellations Amid Low Visibility