In 2023, Delhi saw rise in PM2.5 levels: Study

NEW DELHI: The Capital recorded a more polluted 2023 compared to 2022, the Centre for Science and Environment (CSE) has said in an analysis of the Capital’s annual PM2.5 levels, which meant the city had reversed gains it had been making in reducing particulate pollution levels since records began to be kept in 2015.

According to its report, the annual PM2.5 concentration last year was 101 micrograms per metre cube (µg/m3) — around 2% higher than 2022 (99µg/m3). Before that, the city recorded an annual PM2.5 concentration of 106µg/m3 in 2021, 109.2µg/m3 in 2019, and 115.8 µg/m3 in 2018.

The only outlier in this trend was 2020 when the country was in a 68-day hard lockdown due to Covid-19, which helped keep the annual average PM2.5 levels to 95µg/m3, the analysis showed.

“Delhi has been witnessing a gradual yet consistent decline in its annual PM2.5 levels since 2015, with 2020 being the only outlier due to massive disruption caused by pandemic lockdowns. But this downward movement stopped in 2023. Delhi’s PM2.5 annual average for 2023 was around 101 µg/m3. This was an increase of 2% compared to the 2022 annual levels and 6% higher than an exceptionally clean 2020. However, the levels were not as high as they used to be earlier – the average of 2018-22 winters is higher than that of the winter of 2023,” CSE said in its analysis.

To be sure, the national standard for PM 2.5 concentration levels is 40µg/m3.

The Capital did meet this standard on 151 days, but the number of “good” air quality days — when the PM2.5 levels are less than 20µg/m3 — dropped from the 41 in 2022 to only 24 in 2023, the report said.

“There was a significant fall in the number of ‘good’ air quality days in 2023. Meanwhile, in 2023, the number of days with PM2.5 concentration in the ‘very poor’ or worse categories stood at 107 days, including 24 with ‘severe’ levels... In 2022, there were 106 ‘very poor’ or worse days, but ‘severe’ days were just nine in number – this was less than half of that of 2023,” it added.

HT on January 1 had reported that last year, Delhi, till October, was on track to record its cleanest year since 2020. However, high PM 2.5 levels in both November and December, impacted the overall average.

Avikal Somvanshi, senior programme manager, Urban Lab at CSE explained, “The summer and monsoon months in 2023 were unusually cleaner, compared to the months in the previous years. However, winter levels turned out to be one of the worst due to very slow surface wind speed. This impeded the dispersal of pollution and led to higher levels. This trapping of local pollution from all sides made this winter exceptionally bad despite lesser smoke from farm fires.”