NEW DELHI: This December saw the longest spell of bad air since air quality records are being maintained in the national capital.
While there were six consecutive days of ‘severe’ air quality --- the most hazardous for health, half of the month saw air quality in the ‘very poor’ range --- the highest in five years.
Data maintained by the Central Pollution Control Board (CPCB) showed that the city saw a total of seven ‘severe’ air quality days this month while six of them were in a row (from December 21-26) --- the longest smog episode since 2015, since when air quality records are being kept in Delhi.
Also, December this year saw 15 days in the ‘very poor’ category --- the highest since 2017 when 19 days were recorded in this category, data shows.
However, unlike over the past five years when the month saw at least one or two and in some cases three ‘moderate’ air quality days, this December did not record a single day in the moderate range. On Friday, Delhi’s overall AQI was 321 in the ‘very poor’ zone after improving to ‘poor’ over the past two days.
On a scale of 0-500, a value of 0-50, the air quality is considered good (minimal health risk), 51-100 is satisfactory (minor discomfort to sensitive people), 100-200 is moderate (breathing discomfort to people with lungs and heart disease), 200-300 is poor (breathing discomfort to most people on prolonged exposure), 300-400 is very poor (respiratory illness on prolonged exposure) and 400-500 is severe (affects healthy people and seriously impacts those with existing diseases).
The long pollution spell started soon after the slew of curbs put in place to curb the growing pollution levels by the Commission for Air Quality Management (CAQM) for NCR and as the weather conditions took a turn for the worse.
The CAQM had on December 20 lifted all the curbs including ban on entry of trucks in the city and construction activities considering an improvement in air quality owing to high speed winds, which died down soon.
According to weather officials and experts, the city saw cold wave conditions right after the curbs were withdrawn when stable weather conditions did not allow dispersion.
This was followed by two successive Western disturbances, with which the wind direction changed and moisture content increased further allowing accumulation of pollutants.