Delhi’s air quality was in the “severe” category on Tuesday, with 29 of the city’s 40 monitoring stations recording Air Quality Index readings above 400, according to data from the Sameer application at 9.05 am.
The national capital’s average AQI stood at 416, showed the application, which provides hourly updates from the Central Pollution Control Board.
At least five stations recorded an AQI of 450 or more, which is in the “severe plus” category.
At 9 am, the Delhi airport said that flight operations had been hampered because of “dense fog”, which may cause delays and cancellations.
The cities adjoining the capital also reported hazardous air quality levels on Monday. While Noida recorded an AQI of 428, Ghaziabad 416 and Greater Noida 378, Gurugram remained in the “very poor” category at 362.
An index value between 301 and 400 indicates “very poor” air. Between 401 and 450 indicates “severe” air pollution, while anything above the 450 threshold is termed “severe plus”.
An AQI in the “severe” and “severe plus” category signifies hazardous pollution levels that can pose serious risks even to healthy individuals.
Delhi and the National Capital Region are under Stage 4 restrictions under the Graded Response Action Plan to curb pollution. The restrictions came into force on December 13 after the air quality slipped into the “severe plus” category.
GRAP is a set of incremental anti-pollution measures that are triggered to prevent further worsening of air quality once it reaches a certain threshold in the Delhi-NCR region.
The air quality in the national capital had worsened to the “severe plus” category between December 13 and December 15, but had improved marginally to the “very poor” category till December 22.
Air quality deteriorates sharply in the winter months in Delhi, which is often ranked the world’s most polluted capital. Stubble burning in Punjab and Haryana, vehicular pollution, along with the lighting of firecrackers during Diwali, falling temperatures, decreased wind speeds and emissions from industries and coal-fired plants contribute to the problem.
Also read: Why air quality numbers in Delhi vary widely
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