Firecrackers remained the largest identified contributor to Delhi's air pollution even after Deepavali. According to the Indian Institute of Tropical Meteorology (IITM), their contribution declined sharply after the festival but continued to remain higher than other pollution sources.
Why in the News?
A source-apportionment study by IITM found that firecrackers contributed 71.1% of Delhi's pollution load on November 9, 2026, and 29.8% on November 10, 2026.
Major Sources of Air Pollution in Delhi
Air pollution in Delhi comes from multiple sources, including vehicular emissions, industrial activities, construction dust, road dust, waste burning, firecrackers, and household fuel combustion. Weather conditions, especially low wind speed and temperature inversion, can further trap pollutants near the ground.
1. Pollution Sources on November 9, 2026
Firecrackers were the largest contributor, followed by:
- Vehicular emissions: 6.9%
- Secondary inorganic aerosols: 5%
- Secondary organic aerosols: 4.5%
- Mixed or unresolved biofuel: 4.45%
- Mineral dust and ash: 2.5%
- Mixed combustion: 2.5%
- Wood burning: 1.3%
- Waste burning: 1.1%
- Coal combustion: 0.5%
- Industrial emissions: 0.2%
2. Pollution Sources on November 10, 2026
The contribution of firecrackers declined to 29.8%, but they remained the largest identified source.
- Secondary organic aerosols: 17.5%
- Vehicular emissions: 11.7%
- Secondary inorganic aerosols: 11.7%
- Wood burning: 10.7%
- Waste burning: 7.7%
- Mixed combustion: 5.1%
- Mixed or unresolved biofuel: 3.3%
- Mineral dust and ash: 1.5%
Air Quality Index (AQI) in Delhi
Delhi's air quality showed some improvement on November 10 but deteriorated the following day again.
- November 10, 2026: AQI stood at 299, falling under the Poor category.
- November 11, 2026: AQI increased to 312, entering the Very Poor category.
AQI Classification
| AQI Range | Category |
| 0–50 | Good |
| 51–100 | Satisfactory |
| 101–200 | Moderate |
| 201–300 | Poor |
| 301–400 | Very Poor |
| 401–500 | Severe |
What are Secondary Aerosols?
Secondary aerosols are tiny particles formed in the atmosphere through chemical reactions involving gases released from sources such as vehicles, industries, and other combustion activities.
- Secondary Inorganic Aerosols: Formed from gases such as sulphur dioxide (SO₂), nitrogen oxides (NOx) and ammonia (NH₃).
- Secondary Organic Aerosols: Formed through chemical reactions involving organic gases in the atmosphere.
Key Finding
The IITM estimates show that firecrackers remained the largest identified source of Delhi's pollution even after Deepavali. However, the model estimates had considerable uncertainty, with standard deviations of 104.1 percentage points on November 9 and 27.7 percentage points on November 10.
Conclusion
Firecrackers continued to be a major source of Delhi's air pollution even after Diwali, although their contribution declined over time. The findings also show that vehicles, waste burning, and other sources add to the pollution. Therefore, controlling air pollution requires action throughout the year, not just during festivals.