Delhi’s air quality remains very poor; shallow fog envelopes city for 2nd day

Delhi’s air quality remained in the higher end of the “very poor” category for a fourth straight day on Wednesday.

As calm winds continued to impact the dispersion of pollutants even as the shallow fog enveloped the city for a second day. The India Meteorological Department (IMD) said visibility dipped to around 800 metres at 7am. Similar visibility persisted over the next hour. “Winds were calm, with shallow fog recorded for a second straight day. On Tuesday, when we saw the season’s first shallow fog, visibility dropped to 800 metres,” said an IMD official.

An average air quality index (AQI) of 356 (very poor) was recorded at 9am. It marked a slight improvement from Tuesday’s 4pm reading of 373 (very poor),

The Early Warning System for Delhi (EWS) said conditions remain unfavourable for the dispersion of pollutants and no significant change was expected in the air quality. It said the air quality was likely to be in the “very poor” until Friday.

Central Pollution Control Board (CPCB) data showed at least four stations recorded severe category air quality at 9am on Wednesday. NSIT recorded 444 and Wazirpur an average AQI of 421.

CPCB classifies AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.

AQI has worsened to severe at least once by November 6 as per CPCB data since 2015. The earliest Delhi’s AQI touched severe since 2015 was on October 20 in 2017. Normally, it happens between the last week of October and the first week of November. This happened on November 1 in 2015, October 29, 2016, October 30 in 2018 and 2019, November 5 in 2020 and 2021, November 1, 2022, and November 3 last year.

Strong winds post-Diwali and higher-than-normal temperatures were key factors behind preventing AQI from touching the severe mark this season.

Centre for Science and Environment executive director (research and advocacy) Anumita Roychowdhury said that despite Diwali on October 31, strong winds and higher-than-normal temperatures helped dissipate pollutants in hours. “This year, the overall temperature has also been higher throughout October, not just at the end of the month. However, one has to realise that AQI was still touching very poor even in October, which means our background emissions are high and it will only take a further dip in temperature to possibly touch severe.”

Delhi environment minister Gopal Rai on Tuesday announced the start of a campaign to check open waste burning from Wednesday. He added that 588 teams will be deployed across the city for this.

Rai held a review meeting with 33 government departments on air quality on Tuesday. He said Resident Welfare Associations, government departments, and construction sites have been directed to provide heaters to night-time workers and security guards to prevent them from using firewood for heating.