New Delhi: Delhi and the National Capital Region (NCR) on Monday experienced the first smog of the season with air pollutants going up many folds higher than the permissible limits and the air quality falling under the “severe-plus” or “emergency” category.
The sudden deterioration, as forecast last week, was due to a change in the wind direction, from easterly to the north-westerly, that has brought smoke arising from stubble burning, and Delhi’s moist air trapping local and invading pollutants.
The air quality index of Delhi at 2 p.m. was 407.
“It was smog in the morning, the air quality has dropped overnight as the wind speed and direction have changed from the earlier easterly to north-westerly from Punjab and Haryana,” said an official at the Central Pollution Control Board (CPCB).
The average volume of PM2.5 and PM10, or particles with diameter less than 2.5 and 10 microns, across 35 regions in Delhi was 368 and 507 microgrammes per cubic meters, which was 14 times higher than the limit.
The PM2.5 and PM10 across 47 regions of NCR was 359 and 498 units.
The permissible limit for PM2.5 and PM10 is 60 and 80 units by national standards and 25 and 50 units by international standards.
On the weekend, the air quality of Delhi and the neighbouring regions experienced easterly winds that cleaned up the air due to the western disturbance that caused snowfall and rains in northern regions.