Delhi logs cleanest April air in 6 years: CAQM data

Delhi's air quality index was below 200 for 23 days in April, the highest in 6 years, showing improvement, but still beyond permissible standards.

The air quality index (AQI) in Delhi was less than 200 on 23 days in April, logging the highest number of such days in the last six years, barring 2020, which was impacted by the Covid-induced lockdown, said the Commission for Air Quality Management (CAQM) in the National Capital Region (NCR) on Tuesday.

Visitors at Lotus Temple in New Delhi on Tuesday. (Raj K Raj/HT Photo)

AQI below 200 is classified into three categories considered acceptable in terms of air quality. It is “moderate” when the AQI is between 101 and 200; “satisfactory” when between 50 and 100 and “good” below 50, as per the Central Pollution Control Board. Similarly, an AQI over 200 is divided into three categories that are considered in the unacceptable range in terms of pollution. It is “poor” when between 201 and 300, “very poor” when between 301 and 400 and “severe” when over 400.

The data, shared by CAQM since 2018 onwards, showed that Delhi recorded 23 such days this month this year, as compared to 17 days last April; zero days in 2022; 18 days in 2021; 30 days in 2020; 12 days in 2019 and eight in 2018.

“As a result of favourable meteorological or weather conditions coupled with consistent, comprehensive and concerted efforts by Commission for Air Quality Management in NCR and adjoining areas and various stakeholders to control air pollution in the National Capital Region (NCR), Delhi recorded maximum number of ‘good’ category to ‘moderate’ category air quality days in April 2024 as compared to the corresponding period of last six years starting from 2018 (except 2020 - the year of lockdown due to Covid), denoting a marked improvement,” CAQM said in a statement on Tuesday.

The average AQI in April this year was marginally worse than last year. The average AQI in April this year was 182. In comparison, it was 180 in 2023; 255 in 2022; 202 in 2021; 110 in 2020; 211 in 2019 and 222 in 2018, it added.

“CAQM is working closely with various stakeholders concerned to take effective measures for prevention, control and abatement of air pollution and to improve the overall air quality in NCR,” the statement said.

Delhi, much like previous years, was ranked the world’s most polluted capital city in the world in 2023, recording an annual PM 2.5 concentration of 92.7µg/m3, beating Dhaka in Bangladesh (80.2 µg/m3). Though pollution levels in the the capital are worst during the winter months, in the summers, they can also remain fairly high, with the AQI known to touch “very poor” when dust storms hit the city. In addition to the usual sources impacting Delhi around the year in terms of vehicles and industries, dust pollution becomes a pertinent problem during the summer months.

Anumita Roychowdhury, executive director, research and advocacy at the Centre for Science and Environment said though a marginal improvement has been seen this time, these levels were still beyond the permissible standards.

“The air quality challenges are different in summer than in winter. In a more open and well-ventilated atmosphere during summers, the impact of dust pollution — especially wind-blown dust increases. This is also the time when the number and frequency of days exceeding ozone standards increases. To combat these, we will require deeper control measures, particularly on combustion sources like vehicles,” she said.