Data | Deepavali day: Record pollution levels in Chennai and Bengaluru, but Delhi and Kolkata fare better

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Along with PM2.5 pollution, there were increases in CO, NH3, NO, NO2 and SO2 levels

Along with PM2.5 pollution, there were increases in CO, NH3, NO, NO2 and SO2 levels

State governments across India announced various degrees of restrictions on bursting crackers this Deepavali. While the measures seem to have worked to an extent in eastern India and parts of the north, cities in the south and west reported record pollution levels on Deepavali.

Pollution during Deepavali spikes due to firecrackers. In 2016, the Chest Research Foundation of India, Pune, conducted a series of experiments on firecrackers to determine the quantum of PM 2.5 particles emitted. For instance, the snake tablet produced a peak PM 2.5 level of 64,500 μg/m3 (micrograms per cubic metre). PM 2.5 is particulate matter that has a diameter equal to or less than 2.5 microns. Graph 1 depicts the peak levels of other types.

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The Tamil Nadu, Punjab and Karnataka governments announced a two-hour window to burst crackers. In West Bengal and Haryana, only green crackers could be sold. In Delhi, there was a complete ban on crackers. There were similar measures in other States. Graph 2 shows the PM 2.5 levels in μg/m3 recorded every hour between January 1, 2018, and October 25, 2022, in a measuring station across select cities. Each dot corresponds to the average PM 2.5 level in an hour. The higher the dot, the more the pollution. Deepavali days in the past five years are highlighted. In the graph, blue dot corresponds to Deepavali days in 2018, 2019, 2020 and 2021, while red dot points to Deepavali days in 2022.

The restrictions in place combined with the effects of Cyclone Sitrang ensured that the PM 2.5 levels did not cross 50 μg/m3 in any of the measuring stations in Kolkata. It stayed below India’s 24-hour PM 2.5 limit of 60 μg/m3 during Deepavali hours. Patna also recorded low levels of pollution this Deepavali.

While no other State recorded such a drastic drop in pollution this Deepavali, there was a general decline in the eastern and northern parts. Lucknow and Noida recorded the smallest Deepavali-day pollution spike in the last five years. Anand Vihar in Delhi saw a significant spike, but the level of pollution stayed below the levels seen in the last four years during Deepavali. In Amritsar and Gurugram, alarming levels of PM 2.5 pollution levels were recorded, but they did not reach the peak recorded in previous years.

On the other hand, in Andhra Pradesh’s capital Amaravati, at 10 p.m. on October 24, the PM 2.5 level peaked at 793 μg/m3 — the highest for any hour since the 2018 Deepavali spike. Bengaluru’s Silk Board station peaked at 633 μg/m3 — the highest in the last five years. Sanathnagar station in Hyderabad peaked at 731 μg/m3 — the highest since 2019. Chennai’s Velachery station peaked at 694 μg/m3 — the highest for any Deepavali day since 2018.

Mumbai too recorded a spike during Deepavali though the levels paled in comparison to other cities. In Ahmedabad and Jaipur, the PM 2.5 levels reached nearly 999 μg/m3 on many Deepavali hours — the limit up to which the devices can record the pollution level.

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Peaks in other types of air pollution can also be seen on Deepavali days. Graph 3 shows hourly levels of carbon monoxide (CO), atmospheric ammonia (NH3), nitrous oxide (NO), nitrogen dioxide (NO2), PM10 (particulate matter equal to or less than 10 microns) and sulphur dioxide (SO2) measured in the Velachery station in Chennai. There was a sharp spike in all these air pollutants during Deepavali hours. NO2 and SO2 levels peaked this year during Deepavali. NO and CO were close to the peak levels recorded earlier this year. In the graph, red dot corresponds to Deepavali days 2022, while grey dot points to other days.

NO2 exposure affects lung function. According to the WHO, hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels. Increase in CO levels is linked to congestive heart failures in the U.S.

vignesh.r@thehindu.co.in, sonikka.l@thehindu.co.in and rebecca.varghese@thehindu.co.in

Source: Central Pollution Control Board

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