The new abnormal: Air pollution is not just a winter thing in Delhi anymore | Deep Dive

There is a new summer cocktail of pollutants in Delhi, made not just of particulate pollution from winters, but also more harmful gases during the summer months this year.

delhi air pollution
Representational image (File/PTI)

Delhi is infamous for being one of the most polluted cities in the world. The situation is considered to be most critical during the winter months, starting in October. But hold on! Air pollution in Delhi is not just a winter phenomenon anymore. Studies have established that pollutants affect the residents of the Indian capital throughout the year now.

While there was a downward trend following the national lockdown during the first wave of the Covid-19 pandemic, air pollution is now back with a vengeance. India Today accessed the five-year daily and monthly data to analyse how the situation has gone from bad to worse over the years with the exception of the lockdown.

Government agencies like the Central Pollution Control Board (CPCB) and the Delhi Pollution Control Committee (DPCC) monitor air quality in different parts of Delhi. These agencies also keep track of the average pollution in 24-hour cycles through the continuous monitoring of real-time data. India Today found that air pollution this year has almost reached pre-pandemic levels from 2018 and 2019. And that’s not just for the usual winter pollution months — the increase in pollution trend is also sustained during March, April, and May.

In fact, these months have surpassed the pollution levels of 2018 and 2019. Executive Director of Center for Science and Environment (CSE) Anumita Roychoudhury explained that comparing the air quality of different months in the last five years since 2018 revealed that March, April, and May this year were the most polluted. She said, “The rise in pollution levels can be attributed to the meteorological conditions like the dry weather and the heatwave spell.”

The data accessed by India Today also reveals there’s much more to worry about. Of the first 151 days of 2022, Delhi recorded a total of 114 days that clocked air quality in the Severe, Very Poor, and Poor categories. In only 37 days, Delhi experienced either Satisfactory or Moderate air quality. What is worrying is that so far this year, Delhiites have not experienced even a single day of “Good” air quality. This year also saw the lowest number of satisfactory and moderate days in the last five years.

In comparison, in the first 151 days of 2018, which was the second-worst in this category, Delhi recorded Satisfactory or Moderate air quality on 44 days, while the Severe, Very Poor, and Poor days were 107 in number.

2019 and 2021 were comparable as both the years recorded 59 days each with Satisfactory or Moderate air quality and both years had 92 days each with air quality in the Severe, Very Poor, and Poor categories.

2020 was the best in terms of air quality and that can be attributed to the national lockdown. In 2020, during the first 152 days of the year, 92 had Good, Satisfactory, or Moderate air quality. The remaining 59 days were in the severe, very poor, or poor category. 2020 was the only year when Delhi recorded two days of Good air quality.

Chandra Bhushan Kumar, the CEO of the iForest, explained to India Today, "Bad air quality has become a year-long phenomenon and is not just limited to the winter months. We are having just 40-45 days of moderate air quality and that too largely in the rainy season or the months of March and April when rain or wind washes away the pollutants out of the capital."

2022 has the best winters but worst summers as far as the air quality is concerned. India Today accessed the month-wise comparative data from 2018 to 2022, starting from January to May end. This year, January had the best average Air Quality Index (AQI) at 155. February, too, had the best average AQI in five years at 110. Things were going well till the middle of March when the gains of the first 75 days were nullified in the subsequent 75 days. The trend that is worrying environmentalists is this sudden jump in the pollution levels during the summer. April and May in 2022 recorded the worst air quality in the last five years.


Till now particulate matter was considered the most harmful pollutant in Delhi's atmosphere. But in summers, the nature of the pollutant change significantly. A study conducted by the CSE revealed that in 2022, Ozone pollution has been predominant and widespread during the summer.

Ozone is formed naturally through the interaction of solar ultraviolet radiation with molecular oxygen. Ground-level ozone is formed primarily from photochemical reactions, depending upon the presence of heat and sunlight. This results in higher ambient ozone concentrations in the summer months.

Anumita Roychoudhury said, "This year, the ozone levels have not just exceeded the normal limits but it has become a widespread phenomenon. Till now it was localised to a few places but now we are finding it in a widespread area. In several industrial areas in Outer Delhi, East Delhi, and even in South Delhi we found the ozone spread in ongoing summers."

Since ozone is a highly reactive gas that triggers health-related problems in a short period, scientists and environmentalists take eight hours on average and not 24 hours to measure its concentration, unlike other polluting gasses.

Roychoudhury further explained that "the concentration of ozone is quite variable and complex to understand. It dissipates from the areas where another pollutant NOx (Oxides of Nitrogen) is more prevalent and affects the nearby areas where the source of pollution is not abundant."

The complex nature of pollutants in the summer months is leaving experts puzzled about their final impact on the human body because these are products of a cocktail of components. Chandra Bhushan Kumar explained, "The smoke that comes out from the vehicles and biomass burning reacting with the SOx (Oxides of Sulphur) becomes Sulphur particles that we are inhaling.

He further said, “So, the Ozone or Sulphur is not being emitted directly but these are the byproducts of chemical reactions in the air and then reaching our respiratory system." Kumar suggested that over-emphasis on vehicular pollution won't help the cause as it contributes only 20 per cent of total pollutants and the rest of the pollution is coming from biomass burning like coal, garbage, etc.