One of India’s biggest environmental issues that occurs every year, is the poor air quality in Delhi during Diwali. The capital of India, New Delhi, experiences poor air quality every year during winter. The issue continues to worsen; October 2021 witnessed high levels of pollution peaking on Diwali.

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The Air Quality Index (AQI) of Delhi was monitored after Diwali 2021 by the Central Pollution Control Board (CPCB). The AQI of the capital averaged 462 for 24 hours till 3 pm– the most toxic air quality that Delhi has ever witnessed on Diwali in the past five years. According to CPCB standards, an AQI above 400 is severe and can negatively affect the health of both healthy people and people already suffering from respiratory ailments.

What is the cause of the capital city’s poor air quality? Is it the firecrackers that are lit during Diwali? Or is there another reason?

Research on Delhi’s Air Quality

The Supreme Court in Delhi recently observed the bursting of firecrackers in Delhi as a temporary issue. It held stubble burning as a major factor responsible for poor air quality in Delhi during Diwali. A recent study conducted by the Indian Institute of Technology Delhi (IIT Delhi) also confirmed the same in its conclusion.

The study was conducted by several scholars in different departments of IIT Delhi. They examined various samples taken from different areas in Delhi during Diwali and then measured the proportions of various particulate matter in the atmosphere. The thorough research revealed that biomass burning is the main reason behind Delhi’s increasing air pollution and worsening air quality. According to the study, biomass burning during winter includes burning firewood and stubble for heat and clearing of agricultural land. The pollutants from Diwali firecrackers do not even remain in the air for 24 hours.

The study is titled ‘Chemical Speciation and Source Apportionment of Ambient PM_2.5 in New Delhi Before, During, and After the Diwali Fireworks’. It was published June 2022 in Science Direct Volume 13, Issue 6 of Elsevier BV’s Atmospheric Pollution Research Journal.

The contributors and authors of the study were from different departments of IIT Delhi. Chirag Manchanda and Mayank Kumar from the Department of Mechanical Engineering and Vikram Singh and Mohammed Faisal from the Department of Chemical Engineering participated in the study. Naba Hazarika from the Department of Applied Mechanics and Vipul Lalchandani, Ashutosh Shukla, and Sachchidanand Tripathi, researchers from the Department of Civil Engineering, also participated in the study and gave their inputs. The Geoscience Division of the Physical Research Laboratory of Ahmedabad was also an essential part of the research team.

The Cause of Delhi’s Poor Air Quality

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To conduct the research, emissions from different sources were tested and analyzed. The emissions from firecrackers contained carcinogenic factors associated with health risks from prolonged exposure to ambient pollution levels. However, the duration of exposure to pollutants from firecrackers during Diwali is much shorter compared to other pollutants.

Besides firecrackers, the research team also examined emissions from motor vehicles, industries, coal combustion, and dust particles. After testing samples, the main contributor to poor air quality in Delhi during Diwali was found to be associated with biomass burning. According to the study, the impact of fireworks during Diwali is most significant only during firecracker burning periods. The coal combustion and related dust emissions mainly remained unaffected.

The study’s conclusion states that biomass burning and not firecrackers contribute to the poor air quality in Delhi. The pollutants from the firecrackers are not the same as those from biomass burning. Thus, it becomes easy to identify the source of the pollutants.

According to the study, fireworks primarily produce metallic elements, high levels of black carbon, and gaseous pollutants such as carbon monoxide, sulfur oxide, and nitrogen oxide. The concentration of these elements reached a high point around midnight on Diwali and dropped about one-third the next day.

On the other hand, pollutants released from biomass burning remained high during the entire study period. Emission from biomass burning rises steeply after Diwali, and the average value increases by more than twice as compared to the periods before Diwali.

The study solved the long-established debate and discussion between researchers and policymakers committed to improving the air quality in the country’s capital city. The Kejriwal Government in Delhi, on the occasion of Diwali, issued a ban on firecrackers to control pollution in the city. The Kejriwal-led government and the Delhi Police initiated a ban on the sale and bursting of firecrackers until the 1^st of January 2022. The firecracker sellers and manufacturers in Delhi slammed the government’s decision to ban firecrackers.

The Supreme Court then examined the ban on firecrackers and observed that the pollution caused by fireworks is just a minor issue as compared to the impacts caused by stubble burning. The study conducted by IIT Delhi backed the Supreme Court’s observation with scientific evidence.