Last winter, all six megacities of the country recorded high average concentrations of fine particulate matter (PM 2.5), with Delhi continuing to be the most polluted, followed by Kolkata, according to a new analysis by the Delhi-based non-profit Centre for Science and Environment. The CSE’s Urban Labs assessed annual and seasonal trends in PM 2.5 concentrations for the October 1 to January 31 period between 2021-22 and 2024-25 using real-time data available from air quality monitoring stations across the six metro cities. In Delhi, the data showed, the average PM 2.5 concentration in the winter of 2024-25 was 175 µg Kolkata, Hyderabad and Mumbai were next: 65 ug/mn3; 52 ug/m3 and 50 ug/m3, respectively. Chennai saw 36 ug/m3 and Bengaluru 37 ug The WHO guidelines recommended that the daily PM 2.5 level should not exceed 15 ug/m3 for 3-4 days in a year. According to the CSE data, Delhi’s average PM 2.5 concentration was 1% higher than the average of the previous three winters, but 7% lower than the previous winter (188 ug/m3). However, the daily peak surged significantly. The Capital’s daily PM 2.5 level — 602 ug/m3, on November 18 last year — was the highest in the past four winters. In the winter of 2021-22, the daily peak was 505 ug/m3, but fell in the next two years to 400 and 364, respectively. “Even after five years of the National Clean Air Programme (NCAP), the megacities — despite investing substantial shares of the grant from the XVth Finance Commission for clean air action — are still struggling to meet clean air standards throughout the year.” said Anumita Roychowdhury, executive director, research and advocacy, CSE. “The NCAP needs to be further strengthened to accelerate action to drastically cut emissions from all key sources.”
