'Almost severe' days in November highest ever

Noxious November: What AQI numbers hide, reveal

- Jasjeev Gandhiok and Abhishek Jha

Yes and No.

Delhi’s average air quality index (AQI) between November 1 and 29 this year was 372, making this the third most polluted November since 2015, the earliest year for which the Central Pollution Control Board (CPCB) has published daily AQI bulletins. But remove the good AQI days on account of rain and the average AQI reading for November 2023 jumps up to 390, just short of “severe”, making it the most polluted November in recorded history.

More than anything, these numbers suggest that without a natural clean-up from favourable meteorological factors, Delhi does not have any plan to control pollution.

The numbers speak for themselves. Delhi’s average AQI between November 1 and 29, 372, ranked third behind 2016 (373) and 2021 (378). But November 2023 was the rainiest November in Delhi since 2015, both in terms of amount of rainfall and the number of days it rained (2023 is tied with 2019 here). November 2023’s average AQI of 372 is significantly worse than the average AQI reading of 334 for November 2018 which was the second rainiest November in terms of rainfall since 2015.

What would pollution levels look like if it had not rained at all? One way to answer this question is to take out the low AQI (less polluted) days coinciding with rainy days . November 2023’s average AQI jumps to 390 after doing this adjustment, which makes it the most polluted November since AQI has been measured for the Capital. (see chart 1)