Science-Based Strategies For Air Pollution Control In India

Source: Indian Express
GS III: Environmental Pollution and Degradation

Why in the News?

Delhi’s winter air pollution has highlighted the limitations of the Graded Response Action Plan (GRAP), with experts calling for a shift towards science-based, airshed-level pollution management rather than relying primarily on temporary restrictions.

News in Brief

• Delhi’s air quality deteriorated to the ‘Very Poor’ category after a prolonged period of relatively better air quality, despite the implementation of GRAP restrictions.
• Delayed winter conditions, changing wind patterns and rainfall variability have influenced the onset of the pollution season.
• Satellite-based monitoring by NASA and South Korea has raised concerns about the underestimation of stubble-burning incidents in Punjab and Haryana.
• Experts have recommended an airshed-based approach supported by scientific modelling, accurate emission inventories and long-term pollution control measures.

Limitations of GRAP in Addressing Air Pollution

• The Graded Response Action Plan (GRAP) introduces emergency restrictions based on the severity of air pollution in Delhi-NCR.
• Measures include restrictions on non-compliant vehicles, construction activities and other pollution-generating activities.
• However, GRAP primarily responds to pollution episodes rather than addressing the underlying sources of emissions.
• Such restrictions provide temporary relief but cannot ensure sustained improvements in air quality.
• Emergency measures cannot substitute for long-term emission reduction and scientific air-quality management.

Role of Climate Variability in Delhi’s Pollution

• Weather conditions significantly influence the accumulation and dispersion of pollutants.
  • Delayed winter onset: Delhi’s peak pollution season was delayed by nearly two weeks.
  • Super El Niño: The prevailing El Niño conditions may have influenced seasonal weather patterns.
  • Rainfall variability: Cyclone-related unexpected rainfall further delayed the onset of winter pollution.
  • Wind speed: Weak winds prevent pollutants from dispersing, resulting in their accumulation near the surface.
  • Temperature conditions: A delayed and milder winter can influence pollution levels and atmospheric stability.
• These unusual weather patterns may be associated with the unprecedented Super El Nino.
• Air pollution is influenced not only by emission sources but also by meteorological conditions.

Stubble Burning

Concerns have emerged over the underestimation of stubble-burning incidents in Punjab and Haryana.

• NASA’s MODIS sensors aboard Terra and Aqua satellites may miss fires occurring between satellite observation periods.
• A NIAS study found significant differences between official estimates and satellite-based observations.
• More than 90% of stubble-burning incidents in Punjab during 2024 and 2025 reportedly occurred after 3 PM, compared to less than 3% in 2021.

Implications

• Conventional satellite monitoring may underestimate farm fires.
• Inaccurate fire counts can affect emission inventories and air-quality forecasts.
• Reliable monitoring is essential for identifying pollution sources and planning effective interventions.

Advanced Satellite Monitoring

• Combining satellite observations can improve the monitoring of agricultural fires and air pollution.
• South Korea’s KOMPSAT-2A satellite uses the Advanced Meteorological Imager (AMI), which provides continuous observations through geostationary monitoring.
• Unlike satellites that observe specific locations at periodic intervals, geostationary satellites can improve the detection of short-lived fire incidents.
• Incorporating accurate stubble-burning data into air-quality models helps improve pollution estimates.
• NIAS modelling estimates that stubble burning could contribute approximately 20% of Delhi’s PM2.5 levels.
• Improved satellite monitoring and accurate emission inventories support reliable air-quality forecasting and evidence-based pollution control.

Need for an Airshed-Based Approach

• An airshed refers to a geographical area within which air pollutants circulate and disperse through atmospheric processes.
  • Air pollution does not remain confined within administrative boundaries.
  • Emissions from neighbouring states, industries, transport and agricultural activities can affect Delhi’s air quality.
  • A city-centric approach cannot adequately address pollution originating outside its jurisdiction.
  • A recent NIAS study undertaken under a project of the Office of the Principal Scientific Adviser to the Government of India, proposes an indigenous framework called AIR-SHED for improving India’s air-quality management.
• Key features:
  • Airshed-based master planning.
  • Integration of emission inventories and satellite observations.
  • Identification of pollution sources across geographical regions.
  • Scientific modelling of pollutant movement.
  • Coordination among different administrative jurisdictions.
• The framework could potentially provide mitigation options covering 90–100% of emission sources.
• It also offers a practical approach that is not restricted to the Delhi National Capital Territory and can be extended across the National Capital Region.

Why Airshed Management is better than GRAP alone

• GRAP provides immediate relief during severe pollution episodes.
• However, repeated emergency restrictions cannot eliminate the underlying causes of pollution.
• They also impose economic and social costs through repeated public inconveience.
• Airshed-based planning focuses on identifying and reducing emissions at their source.
• GRAP is necessary during pollution peaks, but sustained emission reduction requires long-term science-based interventions.

Emerging Challenges for Delhi’s Air Quality

The factors that could worsen air pollution during the coming weeks;

• Stubble burning: Continued agricultural residue burning in neighbouring states.
• Unstable meteorology: Early-winter weather conditions may favour pollutant accumulation.
• Weak winds: Reduced atmospheric dispersion can increase pollution concentration.
• Fog: Pollution transported from the Indo-Gangetic Plain may combine with fog and worsen air quality.
• Western disturbances: ENSO-related changes in western disturbances could affect rainfall and atmospheric conditions.

Apart from seasonal factors, year-round sources also require attention;

• Traffic congestion at road junctions.
• Poorly maintained roads.
• Ineffective traffic management.
• Open waste burning.

These sources require continuous interventions rather than  seasonal restrictions.

Challenges in Tackling air Pollution

• Fragmented governance: Pollution sources extend across multiple states and administrative boundaries.
• Data limitations: Inaccurate emission inventories and missed fire incidents affect pollution estimates.
• Weather dependency: Wind speed, rainfall, temperature and atmospheric stability influence pollutant concentration.
• Seasonal approach: Excessive dependence on emergency restrictions weakens long-term pollution management.
• Implementation gaps: Traffic congestion, open waste burning and road dust remain persistent sources.
• Inter-state coordination: Effective control requires cooperation among Delhi, Punjab, Haryana, Uttar Pradesh and Rajasthan.

Way Forward and Conclusion

Adopt airshed-based planning, improve pollution monitoring and promote crop-residue management. Strengthen inter-state coordination and address vehicular, industrial and construction emissions through sustained measures, while using GRAP for emergency response.

Delhi needs long-term, science-based pollution control rather than temporary restrictions to achieve cleaner air.

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