Delhi woke up to a thick blanket of fog on Tuesday, but the real danger lies in the air residents are breathing. The national capital is currently battling a lethal cocktail of dense fog and hazardous pollution, with the Air Quality Index (AQI) hovering close to 400, a level classified as ‘Severe’, raising serious health concerns across Delhi-NCR.
According to the India Meteorological Department (IMD), visibility at Indira Gandhi International Airport (IGI) at 10:00 UTC dropped to around 1.1 km, while runway visual range remained just about 2 km. The poor visibility severely disrupted flight operations— 78 arrivals and 70 departures were cancelled, while two flights had to be diverted. The chaos followed another day of disruption, as 118 flights were cancelled yesterday, with delays continuing despite the implementation of CAT-III landing protocols.
Fog Trapping Toxic Air, Experts Warn
Meteorologists and environmental experts have warned that fog is making the pollution situation even worse. Fog traps pollutants near the earth’s surface, preventing them from dispersing. As the fog lingers, the AQI is expected to deteriorate further, exposing residents to heightened respiratory risks. Many are now questioning whether Delhi has seen this level of pollution before.
December Pollution Trend: A Grim Pattern
Over the past decade, Delhi’s December air quality has consistently fallen under the ‘Very Poor’ to ‘Severe’ category. Historical data shows:
- Worst December AQI recorded in 2016 at 365, followed by 2018 at 360.
- After slight relief in 2024, when December AQI dropped to 294, pollution rebounded sharply in 2025, touching 350, making it the third-worst December air quality in 10 years.
What Is Polluting Delhi the Most?
Data from the Central Pollution Control Board (CPCB) reveals that Delhi continues to suffer from dangerously high PM2.5 and PM10 levels.
In December 2025, the city recorded:
- PM2.5: 212 µg/m³
- PM10: 341 µg/m³
PM10 has historically remained the dominant pollutant in Delhi’s air. However, experts note a worrying shift— PM2.5 levels have surged by over 50% between 2023 and 2025, narrowing the gap. While coarse dust particles remain a problem, it is the fine particulate matter that now poses an even greater threat to human health, as PM2.5 penetrates deep into the lungs and bloodstream.
Delhi’s Worst AQI Days of 2025
Delhi recorded its most polluted day of the year on 14 December 2025, when AQI touched a shocking 461, firmly in the ‘Severe’ zone. Many of the capital’s top 10 worst air quality days fell in November and December, including:
- 13 December – AQI 431
- 15 December – AQI 427
- 11 November – AQI 428
Experts attribute this winter spike to a combination of cold weather, low wind movement, and atmospheric inversion, which traps pollutants close to the surface.
As Delhi battles suffocating fog and toxic air, concerns continue to mount over public health, disrupted travel, and the capital’s worsening winter pollution crisis.