New Delhi, Oct 22 Delhi’s winter air quality has shown no consistent improvement in the four years since revision of the Graded Response Action Plan (GRAP) in 2022, with the city experiencing high pollution levels despite frequent imposition of stringent curbs, according to an analysis by the Centre for Research on Energy and Clean Air (CREA).
The city’s mean air quality index (AQI) rose from 280 in the winter of 2022-23 to 304 in 2023-24, declined to 285 in 2024-25 and increased again to 295 in 2025-26, said Manoj Kumar, an analyst at CREA.
The median AQI also fluctuated, rising from 294 in 2022-23 to 324 in 2023-24, falling to 289 in 2024-25 and climbing to 305 last winter.
The findings indicate that the capital’s winter air quality has not followed a sustained downward trend since the revised GRAP framework was introduced, with both mean and median AQI levels in 2025-26 higher than those recorded in 2022-23.
The analysis, based on daily AQI readings and GRAP stages between October 2022 and February 2026, found that Delhi spent around 78 to 83 per cent of observed days across the four winters under Stage II or higher of the pollution-control plan.
The city recorded 32 days under GRAP Stages III and IV in 2022-23, 39 in 2023-24, 57 in 2024-25 and 42 in 2025-26. “That is roughly four out of every five days,” the analysis mentions.
Although the number of days under the two most stringent stages declined last winter compared with the year before, the mean and median AQI remained higher than those in 2022-23, the analysis said.
To examine pollution trends following escalation of emergency measures, CREA analysed 12 instances in which Delhi moved from GRAP Stage II or below to Stage III or Stage IV curbs, identifying three episodes in each of the four winters.
The mean AQI in the seven days following the escalation was higher than in the preceding seven days in 10 of the 12 instances.
The sharpest increase followed the November 2, 2023, episode, when the mean AQI rose from 317 in the preceding week to 431 in the following week, an increase of 114 points.
Other significant increases were recorded following episodes on October 29, 2022, and January 3 and January 28, 2025.
The day-by-day analysis showed that average AQI logged around 25 per cent increase from the preceding seven-day average on the first and second days after the escalation of measures. By the seventh day, it remained around 15 per cent above that baseline.
However, the analysis cautioned that these trends do not establish whether GRAP restrictions caused changes in pollution levels, as AQI is also influenced by weather conditions and the measures have evolved over the four winters.
GRAP, first introduced in 2017 and substantially revised in 2022, is an emergency response mechanism intended to address deteriorating air quality through progressively stricter measures.
Kumar said long-term clean-air strategies should prioritise reducing emissions at source across the national capital region’s wider airshed, with GRAP serving as the last line of defence rather than primary means of tackling pollution.
The analysis called for action across different pollution sources instead of relying mainly on temporary restrictions or concentrating efforts on a limited number of sectors.
It also highlighted the need to address why emissions remain high enough for Delhi to repeatedly experience severe air pollution episodes, rather than focusing only on measures to be implemented once air quality deteriorates.
The analysis used daily AQI bulletins issued by the Central Pollution Control Board and GRAP-stage records published by the Commission for Air Quality Management.
(PTI News)
