New Delhi: Heavy rain cleaned Delhi’s air on Thursday, with the air quality index (AQI) improving to 48, from 59 a day earlier.As a result, residents could enjoy ‘good’ air for the first time in nearly three years. The city last recorded such a day on Sept 10, 2023, when the AQI dropped to 45 following rainfall and restrictions imposed during the G20 summit.Central Pollution Control Board (CPCB) classifies an AQI of 0-50 as ‘good’, 51-100 as ‘satisfactory’ and 101-200 as ‘moderate’, 201-300 as ‘poor’, 301-400 as ‘very poor’, 401-450 as ‘severe’, and 451 and above as ‘severe plus.’Of the 38 active continuous ambient air quality monitoring stations (CAAQMS), Dr Karni Singh Shooting Range was the cleanest on Thursday with an AQI of just 23. Jahangirpuri was the most polluted with the AQI reaching 102.Anumita Roychowdhury, executive director, research and advocacy, Centre for Science and Environment, said, “This reaffirms the fact that monsoon rains have a strong washout effect on pollution and clean the air. However, we need round-the-year action on all key sources of pollution and a clean- and zero-emission roadmap to minimise the seasonality in air quality trends and sustain this impact.”Since CPCB began measuring AQI in 2015, Delhi has recorded good air quality only after spells of heavy rainfall or when polluting activities were significantly reduced due to lockdown or restrictions. Overall, Delhi has seen only 15 such air days till now in the past 11 years.Sept 10 was the only such day in 2023. Delhi did not record a single ‘good’ air day in 2015, 2016 and 2018. In 2017, there were two such days during monsoon — on July 30 and 31. A similar pattern was seen in 2019, when the AQI fell to 49 on two consecutive days — on Aug 18 and 19.The highest number of good air days was seen in 2020 during the pandemic. One was in March during the Covid-19 lockdown, while four were recorded in August during monsoon.In 2021, Delhi witnessed just one good air day on Oct 18, when persistent rainfall across the city and neighbouring districts brought the AQI down to 46. The following year, the capital recorded three such days in Sept and Oct, with rainfall once again playing a key role in improving air quality.Dipankar Saha, former head of CPCB’s air laboratory, said, “Monsoon helps improve air quality by washing dust and other pollutants from the air. As a result, these months are the cleanest in Delhi.”
