Context:
Delhi’s air quality continues to remain persistently degraded, with the Air Quality Index (AQI) staying in the ‘Poor’ category. A 2025 analysis by the Centre for Research on Energy and Clean Air (CREA) highlights that a major share of pollution originates outside the city, underscoring the limits of city-centric pollution control strategies.
Key Highlights:
Current AQI Status
• Delhi AQI stood at 276 (‘Poor’) on Saturday, worsening from 236 recorded on Friday.
• Noida AQI deteriorated to 242, while Gurgaon AQI declined to 244, indicating region-wide air quality stress.
• The IMD issued a yellow alert for moderate fog, signalling adverse meteorological conditions.
Regional vs Local Pollution Contribution
• 65% of Delhi’s air pollution in 2025 originated from outside the city, as per CREA.
• Local sources contributed only 35%, showing that transboundary pollution dominates, especially in winter.
• Delhi’s geographical location in the Indo-Gangetic plains makes it highly vulnerable to polluted air transported by winds from surrounding states.
Major Local Sources
• Vehicular emissions emerged as the largest local contributor to PM2.5, accounting for nearly half of locally generated fine particulate matter.
• Stubble burning contribution declined sharply to 4.9% in 2025, compared to 15.5% in 2024, indicating partial success of agricultural interventions.
Meteorological Constraints
• Unfavourable weather conditions—including calm winds and reduced mixing depth—restricted pollutant dispersion.
• Mixing depth, which determines vertical dispersion of pollutants, is projected to decline from 1,400 m to about 1,000 m by January 5–6, likely worsening air quality.
Air Quality Trends
• Despite improvements in average PM2.5 and PM10 concentrations in 2025, Delhi did not record a single ‘Good’ AQI day, reflecting the severity of baseline pollution.
Relevant Prelims Points:
• Air Quality Index (AQI): Composite indicator reflecting overall air pollution levels and associated health risks.
• PM2.5: Fine particulate matter with diameter ≤2.5 microns; penetrates deep into lungs and bloodstream.
• Mixing Depth: Vertical height up to which pollutants can disperse; lower values worsen pollution concentration.
• Airshed: A geographic area where air pollution sources and impacts are interlinked.
Relevant Mains Points:
• Dominance of regional pollution highlights the inadequacy of city-only mitigation approaches.
• Vehicular emissions reflect challenges in urban transport planning and fuel transition.
• Declining role of stubble burning indicates that policy interventions can work when regionally coordinated.
• Meteorological dependence of pollution underscores the need for season-specific governance responses.
• Air pollution poses serious public health, productivity, and economic costs, especially in megacities.
Way Forward:
• Shift from city-based actions to airshed-level governance involving Delhi and neighbouring states.
• Strengthen regional coordination mechanisms under CAQM and similar bodies.
• Accelerate clean mobility transitions, public transport expansion, and emission norms enforcement.
• Integrate real-time meteorological forecasting into pollution response plans.
• Focus on long-term structural measures alongside emergency responses during winter peaks.
UPSC Relevance:
GS 3 – Environment & Ecology
GS 1 – Indian Geography
Prelims – AQI, Air pollution sources, Meteorological factors