NEW DELHI: The gradual and consistent decline in the city's annual PM2.5 levels since 2015-17 was interrupted in 2023, according to the Centre for Science and Environment. Delhi's annual PM2.5 average for 2023 till December 29 stood at 100.9 micrograms per cubic metre, an increase of 2% from 2022 6% from the exceptionally clean 2020.
The analysis by CSE found that in 2023, 151 days met the National Ambient Air Quality Standards.
This was similar to the trend in 2021 and second only to the lockdown year of 2020 when 174 days had met the quality standard. In 2022, only 117 days had met the norms. Almost all of these cleaner days were recorded in the summer and monsoon seasons, said CSE.
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Despite the days meeting the quality norms in 2023, there was a significant fall in the number of 'good' air days when the pollution levels were 50% below the standard that year, with 24 such days against 41 in 2022. Between October 1 and December 29 in 2023, there were only three days of 'satisfactory' air quality and no 'good' air day. There were more days in these categories in the same period in the previous two years.
According to CSE, Delhi also suffered the highest number of smog episodes of the past six winters in the current season. While there are usually two smog episodes (defined as at least three or more continuous days of 'severe' pollution) in the months of November and December, there were three in 2023 by December 24 and the fourth by December 30.
"This was the highest number of smog episodes observed in a season in the past six winters," said a CSE statement. "Overall, the 2023 winter seems to have had the most consistent bad air in the last six winters, with minimal fluctuations in daily PM2.5 levels. The data indicates that this was the longest spell of 'very poor' or 'worse' air in the last six years."
Anumita Roychowdhury, executive director, research and advocacy, CSE, said, "Due to the impact of the unusual winter levels, the overall annual pollution concentrations plateaued and even worsened, undoing the gains of the long-term downward trend. With the contribution of stubble burning to Delhi's pollution going down this year because of rain in November and less severe cold conditions, the annual PM2.5 level should have improved." She explained that the worsening of meteorological conditions - mostly, low wind speed - left pollution at high levels.
Avikal Somvanshi, senior programme manager, Urban Lab, CSE, said, "Sustained action is required on reducing vehicular emissions, with a massive scaling up of the zero-emission electric vehicle programme and an efficient public transport strategy. There has to be a clean fuel transition in all segments of industries, with stringent compliance with emissions targets and replacement of solid fuels in households and eateries. Waste burning must be eliminated and strong measures taken in the construction sector."
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