Tackling Air Pollution Requires a Science-Based Plan, Not Just GRAP

07 Nov 2026

Tags: Environment   Conservation   Pollution control

Source: The Indian Express

Context: Delhi has implemented its Winter Action Plan from November 1, introducing measures such as restrictions on vehicles below BS-IV emission standards, the No PUCC, No Fuel policy and construction restrictions.

• Despite these measures, Delhi's air quality deteriorated to the 'Very Poor' category on the first day of implementation, highlighting the limitations of emergency measures without addressing underlying pollution sources.
• The article emphasises two major requirements: airshed-based pollution mitigation and moving beyond dependence on the Graded Response Action Plan (GRAP).

Role of Changing Weather Conditions

• The onset of Delhi's peak pollution season was delayed by nearly two weeks due to unusual climatic conditions, potentially influenced by a Super El Niño, Cyclone Arnab and associated rainfall.
• A climatic interaction between slow wind speeds and delayed onset of winter influenced pollution levels:
  • Slow winds favour the accumulation of pollutants.
  • Delayed and relatively mild winter conditions initially help keep pollution levels comparatively lower.
• A recent NIAS study indicates a strong connection between El Niño–Southern Oscillation (ENSO) and air pollution.
• The coming 30–40 days could be particularly challenging due to stubble burning, unstable early-winter meteorology and intermittent high-emission episodes.
• Deeper winter may worsen pollution through local fog and fog transported from the Indo-Gangetic Plain, potentially aggravated by weaker western disturbances and slower winds.

Limitations of Existing Stubble-Burning Estimates

• Conventional fire-count estimates from NASA's MODIS sensors aboard Terra and Aqua satellites increasingly fail to capture agricultural fires in Punjab and Haryana because their observation timings do not coincide with actual burning periods.
• More than 90% of stubble-burning events in Punjab during 2024 and 2025 occurred after 3 PM, compared with less than 3% in 2021, making conventional satellite observations less reliable.
• South Korea's KOMPSAT-2A satellite, equipped with the Advanced Meteorological Imager (AMI), provides continuous observations through its geostationary positioning and detects substantially more agricultural fires than official estimates.
• NIAS air-quality modelling indicates that incorporating realistic stubble-burning emissions reproduces the sharp rise in measured PM2.5 levels on November 1, attributing approximately 20% of Delhi's PM2.5 burden to stubble burning.
• Reliable satellite observations and realistic emission inputs are essential for accurate pollution forecasting and effective policy interventions.

Need for an Airshed-Based Approach

• Delhi's pollution originates not only within the National Capital Territory (NCT) but also from surrounding regions, requiring coordinated action across geographical areas that share the same air pollution system.
• A Delhi-centric approach addresses only around 50–70% of the emission sources affecting the city, even before accounting for additional stubble-burning emissions.
• 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 AIRSHEDEM.
• AIRSHEDEM promotes airshed-based master planning and can potentially achieve nearly 100% coverage of relevant pollution sources through a scientifically defined and administratively feasible geographical framework.
• It proposes a practical middle ground between covering the entire National Capital Region (NCR) and restricting interventions to Delhi NCT.

Limitations of the Graded Response Action Plan (GRAP)

• GRAP provides emergency pollution-control measures that are activated according to the severity of air pollution.
• It is comparable to an Intensive Care Unit (ICU) intervention for a chronic patient: necessary for immediate stabilisation but insufficient to cure the underlying problem.
• Emergency restrictions may temporarily reduce pollution but cannot substitute for sustained and structural emission reduction.
• Repeated restrictions also impose public inconvenience without necessarily addressing the sources responsible for recurring pollution episodes.

Persistent Sources of Delhi's Air Pollution

• Transport emissions: Traffic congestion at road junctions and ineffective traffic management increase vehicular pollution.
• Road dust: Poorly maintained roads contribute to particulate matter emissions.
• Waste burning: Open burning of municipal and other waste releases harmful pollutants.
• Agricultural emissions: Stubble burning in neighbouring States contributes to seasonal deterioration in air quality.
• These sources require year-round interventions rather than measures restricted to the winter pollution season.

Way Forward

• Scientific monitoring: Adopt reliable satellite-based fire detection systems and realistic emission inventories to improve pollution forecasts.
• Airshed-level governance: Coordinate pollution-control measures across Delhi and surrounding regions instead of relying on isolated State-level interventions.
• Structural emission reduction: Address vehicular emissions, road dust, waste burning and agricultural pollution through sustained measures.
• Weather-informed planning: Integrate ENSO, wind patterns, western disturbances and other meteorological factors into air-quality forecasting.
• Beyond GRAP: Treat emergency restrictions as supplementary measures while prioritising long-term emission reduction and comprehensive airshed-based planning.

Important Concepts

• Airshed: A geographical region within which air pollutants circulate and disperse under common meteorological conditions. It may extend across multiple administrative boundaries.
• PM2.5: Fine particulate matter with a diameter of 2.5 micrometres or less, capable of penetrating deep into the lungs and entering the bloodstream.
• ENSO (El Niño–Southern Oscillation): A recurring climate phenomenon involving fluctuations in sea-surface temperatures and atmospheric pressure over the tropical Pacific Ocean. It influences global rainfall, temperature and wind patterns.
• Western Disturbances: Extra-tropical weather systems originating around the Mediterranean region that bring winter rainfall to north-western India and snowfall to the Himalayas.
• GRAP: A graded emergency response mechanism implemented in Delhi-NCR to control air pollution through restrictions on activities such as construction, industrial operations and vehicular movement, depending on pollution levels.