Capital in a chokehold as air quality plummets to 'severe+'

Delhi's air breached the “severe plus” category on Sunday for the first time this winter—with a 24-hour average air quality index of 461— making it the second worst AQI reading for December since the system was launched in April 2015.

- Jasjeev Gandhiok

However, the average number was only a glimpse of the crisis as at least three stations maxed out at the 500-mark at various points on the day.

At 4pm, 38 of Delhi's 39 active stations were “severe,” with only Shadipur in “very poor.” Wazirpur topped 500 the upper limit of Central Pollution Control Board's monitoring; Rohini and Ashok Vihar also breached it, while Jahangirpuri, and Mundka hit 499.

CPCB classifies air quality as “moderate” when the AQI is between 101 and 200, “poor” between 201 and 300, and “very poor” between 301 and 400. Beyond 400, air quality is categorised as “severe”. For the purpose of Grap, 450+ is termed as “severe plus” with CPCB values not going beyond 500-a threshold already considered seriously dangerous by the pollution agency.

The only time December recorded a higher AQI than Sunday's was on December 21, 2017, when the reading stood at 469.

At that time, Delhi only had eight active air quality monitoring stations, compared to the number now. This makes Sunday's average far more alarming for this time of the year as it is easier to breach this threshold in terms of average AQI with a fewer stations, compared to the same average with more stations.