Rains help bring a clean start to Delhi in 2023

New Delhi: Air quality during the first four months of 2023 was recorded as the second cleanest in the last eight years, only behind 2020 when the Covid-19 lockdown was in place in the country, according to pollution data for January to April shared by the Commission for Air Quality Management (CAQM) on Sunday.

CAQM data showed that Delhi recorded 52 days in these four months when the Air Quality Index (AQI) was lower than 200 till April 30. In 2020, owing to the lockdown, Delhi recorded 68 such days. In comparison, Delhi had 27 such days last year, while the figure was just eight in 2016.

The Central Pollution Control Board (CPCB) classifies an AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor” and over 400 as “severe”.

Therefore, an AQI lower than 200 is “moderate”, “satisfactory” or “good”. While no good air days were recorded so far this year, a majority of the 52 days with lower than 200 AQI comprised “moderate” air days, CAQM said.

Though CPCB launched AQI in 2015, the data only began being collated in April 2015. Therefore, full-fledged comparative data is only available from 2016.

CAQM said with the number of “satisfactory” and “moderate” days increasing, the number of “poor” to “severe” air days have subsequently reduced during this period and attributed this relatively clean start to the year to persistent ground-level efforts and policy initiatives, which it said was beginning to show results.

However, it needs to be noted that meteorological factors also helped Delhi’s air quality this year. February was warmer than usual, with an average monthly maximum temperature of 27.7°C, making it Delhi’s warmest February since 2006 (29.7°C), and the month was also characterised by strong winds. Both high temperatures and strong winds allow pollutants to disperse more freely.

In the past, low temperatures in February have often led to Delhi recording days where the AQI fell in the “severe” range. The second half of March, meanwhile, recorded three back-to-back western disturbances, bringing strong winds and rain that settle pollutants. April recorded multiple western disturbances as well with surplus rain and strong winds.

“Persistent field-level efforts and targeted policy initiatives in the short, medium, and long term are expected to result in gradual but marked improvement in air quality. The number of “poor” to “severe” air quality days from January to April came down by 37.03% when compared to 2016 when it was 108 such days,” CAQM said in a statement.

In 2016, there were eight days when the AQI was lower than 200, in 2017 there were 29 days, 32 in 2018, 44 in 2019, 68 in 2020, 31 in 2021, and 52 in 2023.

The same improvement reflected in the daily average particulate matter 2.5 concentration between January and April, with Delhi recording an average PM 2.5 concentration of 109 micrograms per cubic metre, which is the second lowest in the last eight years, behind 2020, when it was just 94 micrograms per cubic metre.

The figure was 158 micrograms per cubic metre in 2016, 124 in 2017, 126 in 2018, 123 in 2019, 132 in 2021, and 118 last year.

Anumita Roychowdhury, executive director, research and advocacy at the Centre for Science and Environment said while there has been a gradual improvement in AQI over the last few years, the contribution of meteorological factors has also helped. “Helpful meteorological conditions also led to a much cleaner winter as well. We can attribute this improvement to both long-term interventions, aided by factors like strong winds and rain. If one considers the long-term annual trends in Delhi, then the overall pollution does appear to be reduced,” she said.