The Wire Staff 
New Delhi: On the morning of November 1, just after the night of Diwali celebrations, many parts of New Delhi were shrouded in smog. As per data released by the Central Pollution Control Board, air quality in the city dipped, with the government’s Air Quality Index (AQI) clocking 328 in the city on October 31 and 339 on November 1 though still remaining in the “very poor” category. Air of this quality can cause respiratory illnesses on prolonged exposure.
Several other metro cities across the country also witnessed a dip in air quality.
Delhi smothered in smog post-Diwali
Smog smothered many parts of the national capital on the morning of November 1, just after the festival of Diwali that was celebrated on October 31.
Called the “festival of light”, Diwali celebrations in Delhi and across many parts of the country are characterised by the use of fireworks, including firecrackers. Studies show that firecrackers release many pollutants into the air, including nitrous oxides and fine particulate matter (or PM2.5).
Fine particulate matter – which are also released when wood and other fossil fuels are burnt, such as in gas in vehicle engines, coal in thermal power plants, and wood in traditional fire stoves – are particles less than 2.5 microns in diameter and can be detrimental to health, causing respiratory illnesses and even cancers.
A study published in 2019 found that firecrackers burst during Diwali 2017 increased levels of sulphates and other pollutants by 3-23 times over the city of Ahmedabad. Another study in 2018 found that the use of firecrackers during Diwali in Delhi causes a small, “but statistically significant increase” in air pollution in the city, and that different locations within Delhi witness different levels of pollution during this time.
With the national capital already witnessing dips in air quality due to stubble burning in croplands in nearby states, the Delhi Pollution Control Committee on October 14 announced a complete ban on the manufacturing, sale, storage, and bursting of all kinds of firecrackers in the the city till January 1, 2025.
However, this didn’t help bring down pollution during this time. As per the Ministry of Earth Sciences’ Air Quality Early Warning System for Delhi (a project undertaken by the Indian Institute of Tropical Meteorology, Pune) and the CPCB, the air quality over Delhi was in the “very poor” category with an AQI of 328 as of 4 p.m. on October 31.
On November 1, air quality dipped further. As per the CPCB bulletin dated November 1, the AQI in Delhi was 339 (still in the “very poor” category) with fine particulate matter (PM 2.5) being the prominent pollutant. Per the Air Quality Early Warning System for Delhi’s bulletin dated November 1, air quality in the city is likely to remain in the “very poor” category on November 2, 3 and 4, and six days to follow. According to the CPCB daily bulletin of November 1, Gurugram also recorded an AQI above 300 (309) which falls in the “very poor” category.
Delhi environment minister Gopal Rai on November 1 flagged off mobile anti-smog guns to counter the pollution menace in the national capital.
Air quality dips in many other metros
Kolkata’s air quality, meanwhile, dipped from a “satisfactory” AQI of 57 on October 31, to a “moderate” AQI of 155 on November 1. Bengaluru witnessed a slight dip in air quality too though it still remained in the “moderate” category on both October 31 and November 1: its AQI increased from 109 to 135 on these days.
Mumbai, however, clocked a “Moderate” AQI of 169 on November 1, barely changing from its AQI of 167 the previous day.
Interestingly, Chennai’s air quality got better on November 1 as its AQI decreased from 213 (“poor”) on October 31, to 142 (“Moderate”) on November 1. This could be because Diwali celebrations that include bursting firecrackers begin earlier here. As per a report by The Hindu, festivities kicked off on October 30, and low wind speeds may have worsened the situation as this prevents pollutants from being dispersed in the air.
According to the report, Chennai also witnessed smog on the night of October 31, with people bursting firecrackers outside the permitted time limits.
Tamil Nadu was among the many states that had banned the bursting of firecrackers except for a specified time slot: it was permitted only for an hour in the morning (6-7 a.m.) and an hour in the evening (7-8 p.m.). Delhi, meanwhile, has a complete ban on firecrackers till January next year. However, people flouted this rule across the city on the night of Diwali, as per several reports.
Other states that had imposed bans and restrictions included Punjab, Haryana, Odisha and Bihar.