The Commission for Air Quality Management (CAQM) for the National Capital Region (NCR) announced a significant rollback of stringent anti-pollution measures on Wednesday. This decision came as the region's Air Quality Index (AQI) showed marked improvement, moving out of the 'severe' category into the 'very poor' range, primarily due to favourable weather conditions.
Why the Curbs Were Lifted
The official trigger for revoking the Graded Response Action Plan (GRAP) Stage-IV restrictions was the consistent drop in pollution levels. The AQI on December 24 was recorded at 271, which falls in the 'poor' category, a substantial improvement from 412 a day earlier. The commission cited forecasts from the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) predicting that the AQI would likely fluctuate between 'poor' and 'very poor' in the coming days.
CAQM highlighted the "disruptive nature of restrictions under Stage-IV" which affect a wide section of stakeholders and the public. After a unanimous decision by its sub-committee, the top pollution control body decided to ease these specific curbs immediately.
Role of Meteorological Factors
The dramatic clean-up was attributed more to nature's intervention than to policy measures. Strong, dry winds sweeping across the region played the most crucial role in dispersing accumulated pollutants. IMD data revealed that the peak wind speed reached 22 kilometres per hour in the south-west direction around 2 pm on Wednesday.
An IMD official noted that while dense fog with visibility as low as 100 metres was recorded at Palam between 2 am and 5 am, conditions improved later. Visibility at Safdarjung was 400 metres by 6:30 am. The dry wind, shifting between south-westerly and westerly directions, prevented fog and humidity from trapping impurities near the ground.
What Changes and What Stays
With the revocation of GRAP Stage-IV, BS-IV compliant petrol-powered light motor vehicles (LMVs) from other states are now permitted to enter Delhi. However, it is crucial to note that all restrictions mandated under the previous GRAP-III stage remain firmly in force across the Delhi-NCR.
These continuing restrictions include a ban on non-essential construction activities and the operation of BS-III petrol and BS-IV diesel LMVs within the region. The commission's move is thus a calibrated relaxation, not a complete withdrawal of all anti-pollution measures.
Impact on Pollution Metrics
The improvement was reflected in key particulate matter data. The Delhi Pollution Control Committee (DPCC) reported that hourly PM2.5 levels at some monitoring stations plunged to as low as 11 micrograms per cubic metre. Analysts pointed out that this sharp reduction was directly linked to meteorological factors.
"The reduction in PM2.5 is attributable to... stronger winds, rather than GRAP measures," stated Manoj Kumar, an analyst at the Centre for Research on Energy and Clean Air (CREA). Alongside cleaner air, the city also experienced a rise in temperature, with the minimum at 10.2 degrees Celsius and the maximum reaching 25.2 degrees Celsius.
The situation underscores the heavy dependence of Delhi's winter air quality on favourable wind patterns, even as regulatory bodies keep a watchful eye on the AQI for any future deterioration.
