Delhi clocked three-year PM2.5 level high in 2024, reveals study

New Delhi

Delhi in 2024 recorded a three-year high in terms of annual PM2.5 (particulate matter having a diameter of 2.5 microns or less) concentration, clocking a reading of 104.7 micrograms per cubic metre (µg/m3) last year compared to 106.4µg/m3 in 2021, according to an analysis by the Centre for Science and Environment (CSE) released on Monday.

Delhi’s peak winter pollution also followed this trend, clocking 732µg/m3 on November 18,the highest since the city clocked a peak winter PM2.5 concentration of 776µg/m3 on November 13, 2021.While the PM2.5 levels were similar to 2019 levels—one of the worst-polluted winters when the AQI dipped to a low of 494 (severe plus) and 24 “severe” air days were recorded—Delhi fared better this winter on average, clocking PM2.5 average of 178.3µg/m3, compared to 182.1µg/m3 clocked last year.

“A troubling trend has also emerged in the peak pollution levels. The citywide winter peak for 2024 soared to 732 µg/m³, marking a 26% jump compared to last year’s peak of 580 µg/m³,” the analysis said.

To be sure, the Central Pollution Control Board (CPCB) has set a safe limit of 40µg/m3 for PM2.5, which is considered hazardous and worsens respiratory ailments, especially during winter.

The study looked at PM2.5 concentration from Delhi’s 37 ambient air quality monitoring stations available from 2018 to 2024. For winter months, the period from October 1 to December 31 was used. 

The study said that the annual PM2.5 level was 3% higher than the three-year average of the 2021 to 2023 period, indicating a loss in air quality gains over the recent past. The study noted that 2024 winter average was 0.2% lower than the 2019 winter average, but 4.6% higher than the three-year winter average (2021-2023), based on data from 37 monitoring stations across the city.

CSE said the annual average PM 2.5 concentration for 2021-23 was 102µg/m3

Sharanjeet Kaur, programme officer with CSE’s Urban Lab and part of the study, said real-time data between October 1 and December 31 showed alarming pollution levels when compared to 2022. “This was a 26% surge in peak pollution levels. The city also experienced 17 days of ‘severe’ or worse air quality, alongside two extended smog episodes with average smog intensity of 371µg/m³ and 324µg/m³, respectively. This kept the average levels elevated,” she said.

Significant station-wise variations

According to CSE’s analysis, in 2024 winter, only eight of 37 air quality stations showed an improvement in their seasonal averages when compared to the 2021-23 period.

The most notable improvements were observed at DTU and NSIT Dwarka stations, which recorded an improvement of 26% and 22%, respectively, compared to the mean of the previous three winters. On the other hand, the North Campus, Okhla Phase 2 and Jahangirpuri stations showed no change in their seasonal averages.

At the other end of the spectrum, CRRI Mathura Road (22%), Aya Nagar (17%), Ashok Vihar and Vivek Vihar (15% each) and Pusa IMD (14%) were the top five stations that recorded an increase in seasonal PM2.5 level compared to previous winters.

“The seasonal averages ranged from 97µg/m³ at DTU to 226µg/m³ at Wazirpur, with Anand Vihar emerging as the second most-polluted location in the city, recording a seasonal average of 224µg/m³,” CSE said.

Anumita Roychowdhury, executive director, research and advocacy, CSE said the data shows 2024 cannot be seen as an annual aberration due to meteorological factors.

“A consistent rise in the annual PM2.5 levels indicates the impact of growing pollution in the region. Delhi seems to be losing its air quality gains from past action. Local and regional sources of pollution including vehicles, industries, open burning of waste, use of solid fuels, construction and dust sources have offset the gains -- undermining the longer term progress over the past decade,” she said.