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Delhi AQI post Diwali worst in 5 years, but crackers, stubble burning may not be only problems

Data from 2017 onwards shows the city's air quality starts worsening from the first week of October and turns 'severe' by the first week of November.

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New Delhi: Delhi’s air quality, which has been worsening since the last week of October, took a further hit Thursday, with Delhi’s pollution levels peaking on Diwali. On Friday, a day after Diwali, the Air Quality Index (AQI) of the capital as prepared by the Central Pollution Control Board (CPCB), averaged 462 for 24 hours till 3 PM, the “most toxic air quality” Delhi had experienced on Diwali in the past five years.

According to CPCB standards, an AQI above 400 is severe and not only can it worsen the health of people already suffering from respiratory ailments, but also negatively impact healthy people.

The AQI for places surrounding Delhi too remained poor, with Gurugram recording an average AQI level of 472 Friday, Ghaziabad being at 470, Noida 475, Greater Noida 464, Manesar 458, Sonepat 400, Faridabad 469, Meerut 435, Rohtak 437, Bhiwadi 418, Baghpat 437 and Ballabgarh 462.

The AQI for Delhi on Diwali had averaged 414 (severe) in 2020, 337 (very poor) in 2019, 281 (poor) in 2018 and 319 (very poor) in 2017.

Air pollution experts feel, however, that the city needs to make sustained efforts through the year to control the problem and not blame it only on the bursting of fire crackers or stubble burning by farmers. Rather, pollution caused by power plants and vehicles too need to be addressed and infrastructural measures for the use of clean energy and electrical vehicles put in place.

Also read: Delhi has two smog towers, but here’s why they are unlikely to help fight air pollution

Decoding trends, year by year

According to available data, Delhi experienced cleaner air this October than what it usually records for this month. The average AQI in October this year was 173, which is categorised as moderate. The average AQI for October in the past five years has been 265 — poor — which, according to the CPCB is bad enough to cause breathing discomfort on prolonged exposure.

Graphic: Ramandeep Kaur | ThePrint
Graphic: Ramandeep Kaur | ThePrint

Various factors contributed to the improved air quality in the national capital during most of last month. One of the biggest reasons were the unseasonal rains, which helped check air pollutions levels in the city and brought down the AQI multiple times in October. It was owing to the rains that the AQI on 18 October in Delhi was 46 — the lowest the national capital has experienced in October since 2017.

After 25 October, however, the capital’s air quality worsened sharply — moving from moderate (AQI 100-200) to severe (AQI 300+) in a matter of just ten days. A comparison of the seven-day rolling average of AQIs shows it has worsened by 100 per cent in the past ten days — from 163 on 26 October to 328 on 5 November.

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The Diwali factor

Conversation around Delhi’s air pollution picks up around Diwali, making it to front page news, as thick grey smog routinely blankets the national capital and peripheries. Blame is shared between stubble burning by farmers in areas around Delhi and the bursting of crackers on Diwali.

Graphic: Ramandeep Kaur | ThePrint
Graphic: Ramandeep Kaur | ThePrint

A study of available data shows, however, that the city’s air quality starts worsening much before the arrival of the festival of lights. In the past five years, on average, Delhi’s air quality has dipped to the “poor” category by the first week of October, with the AQI hovering between 200-300. By the third week of October, the city’s AQI typically dips further, into the “very poor” category, with an average AQI range of 300-400. The air quality usually turns “severe” by the first week of November.

Since the date for Diwali keeps shifting according to the Hindu calendar, however, it is typically celebrated sometime between the last 10 days of October to the first half of November. While the past few years’ data from the period around Diwali reveals that Delhi air quality does worsen after the festival, touching “severe” levels before gradually dipping into the “very poor” category, this was not the pattern in 2020.

Last year, Delhi’s air quality turned “severe” a week before Diwali. At that time, various news organisations had reported how stubble burning had broken records in north-western parts of India, impacting the air quality in the national capital.

While Diwali was celebrated on 14 November last year, the city’s AQI had already breached the 400 limit in the first week of November. In fact, the AQI had averaged 442 (severe) for five consecutive days between 5 and 10 November. Rains the the day after Diwali (on 15th November), finally helped bring down the average AQI to 236 (poor) in the next five days.

“You have to see the air quality a day before and after Diwali. It is enough to show that firecrackers do exhibit their colour in the thick dense fog that covers the city,” said Hemant Kaushal, project coordinator of IIT Delhi’s Arun Duggal Centre of Excellence for Research in Climate Change and Air Pollution.

Kaushal adds, however, that the bursting of firecrackers is not the only reason for Delhi’s poor air quality and that the city needs to make efforts through the year to combat the problem.

“Stubble burning in neighbouring states, firecrackers etc. do add up to the city’s pollution, but they are not the major factors. Power plants in the vicinity of the capital, vehicular pollution and other various sources of pollution are present throughout the year,” said Kaushal.

“Even if we had no stubble burning at all, or no firecrackers were burnt, there would still be some level of pollution remaining in the city as these factors are not the biggest contributors to Delhi’s pollution”, he added. “This means that we need a long-haul solution to this problem, not only during the winter season when it gets worse. We need to build infrastructure for accommodating electric vehicles, strengthening public transportation systems and focus on clean energy solutions to combat the bigger contributors, which requires efforts throughout the year.”

(Edited by Poulomi Banerjee)

Also read: Study links air pollution to nearly 6 million premature births worldwide in 2019


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