Science-Based Strategies For Air Pollution Control In India
Source: Indian Express
GS III: Environmental Pollution and Degradation
Overview
- GRAP provides emergency pollution-control measures in Delhi-NCR but cannot address the underlying causes of air pollution.
- Climate variability, changing weather patterns and stubble burning influence Delhi’s winter air quality.
- Satellite-based monitoring and accurate emission inventories are essential for identifying pollution sources and improving air-quality forecasts.
- An airshed-based approach, supported by scientific planning and inter-state coordination, is necessary for long-term pollution control.
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.
What is GRAP?
- The Graded Response Action Plan (GRAP) is an emergency pollution-control framework implemented in Delhi-NCR.
- It operates through different stages based on the Air Quality Index (AQI).
| Stage | AQI Category |
|---|---|
| Stage I | Poor (201–300) |
| Stage II | Very Poor (301–400) |
| Stage III | Severe (401–450) |
| Stage IV | Severe+ (Above 450) |
- The objective is to introduce progressively stricter measures as air pollution worsens.
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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