In News: The Commission for Air Quality Management (CAQM) released an expert report (Jan 2026) on causes of air pollution in Delhi-NCR, prepared pursuant to Supreme Court directions in M.C. Mehta vs Union of India.
Key Findings
1. Secondary Particulate Matter (Largest Contributor)
- Contributes 27% of winter PM pollution.
- Formed in the atmosphere via chemical reactions of SO₂, NOx, NH₃, VOCs.
- Examples: Ammonium nitrate and ammonium sulphate aerosols.
2. Other Major Winter Sources
- Transport: 23% (largest primary source)
- Biomass burning: 20%
- Dust: 15% (road dust, soil, construction & demolition)
- Industry (incl. TPPs): 9%
3. PM Trends
- PM2.5 and PM10: Gradual decline and stable trend since 2016.
- Still far above National Ambient Air Quality Standards (NAAQS).
4. Transboundary Pollution: Nearly two-thirds of Delhi’s PM2.5 originates outside Delhi (regional sources).
5. Seasonality
- Winter peaks due to meteorological factors:
- Low wind speed
- Shallow planetary boundary layer
- Atmospheric stagnation
- Not due to sudden emission spikes alone.
IAS-2026 - OPTIONAL / GEOGRAPHY / PUBLIC ADMINISTRATION / SOCIOLOGY / ANTHROPOLOGY / ORIENTATION ON 03 & 04-10-2025 
