New Delhi: Delhi has shown no consistent improvement in winter air quality over the last four years, in spite of emergency pollution-control measures under the Graded Response Action Plan (GRAP), a data analysis by a non-profit research organisation the Centre for Research on Energy and Clean Air (CREA) has revealed.The analysis, authored by Manoj Kumar, an analyst specialising in South Asia energy and air quality assessments at CREA, found that Delhi’s winter air quality has fluctuated since the revision of GRAP in 2022, with the mean and median Air Quality Index (AQI) measuring higher in the previous winter season than 2022-2023.“Delhi’s winter AQI has fluctuated over the past four years, with no consistent improvement. The mean AQI rose from 280 in winter 2022-23 to 304 in 2023-24, fell to 285 in 2024-25 and increased again to 295 in 2025-26. The median AQI followed a similar pattern, rising from 294 to 324, falling to 289 and then increasing to 305,” the analysis read.Its findings raise questions about whether emergency restrictions, albeit necessary during severe periods of pollution, can bring about sustained improvements in emissions.The analysis also found that the national capital spent a substantial proportion of winter under stricter pollution-control measures. Across the four winters, Delhi spent around 78% to 83% of the days considered in the sample under stage II or higher GRAP regulations. Meanwhile, stage III and IV were implemented for 32 days in 2022-2023, 39 in 2023-2024, 57 in 2024-2025 and 42 in 2025-2026, per the analysis.Photo: India Air Quality & Energy Insights, Major Kumar. This pattern evidences that fewer days under the strictest restrictions do not necessarily mean an overall improvement in winter air quality.Higher GRAP stages did not improve air qualityThe analysis examined 12 episodes where Delhi moved from below stage III of GRAP to higher restrictions. Three episodes were selected from each winter and for every individual episode, the average AQI of seven days before the escalation of GRAP stages was compared with the average from seven days after the implementation, excluding the day on which the escalation was enforced.The findings point to worsening air quality in the week after higher GRAP stages were implemented for 10 of the 12 episodes. Only two episodes showed a decrease in AQI levels. The largest spike in AQI was observed after November 2 in 2023, when the mean rose from 317 to 431, a substantial difference of 114 points, in the week after the enforcement of higher measures.Photo: India Air Quality & Energy Insights, Major Kumar. Other notable increases mentioned in the report, include October 29, 2022, with an increase of 100 points; January 3, 2025, with an increase of 94 points; and January 28, 2025, with a rise of 92 points. The episodes where pollution levels declined after higher restrictions were implemented, noted in the analysis, are: December 4, 2022 (from 355 to 324), and January 15, 2024 (356 to 345). These changes, as can be seen, are much lower than the ones observed in the other 10 cases.Kumar’s analysis cautioned that these findings cannot be interpreted to mean that GRAP restrictions led to pollution increase, since GRAP measures are introduced when air quality is already severe or forecast to worsen in the coming days. However, the pattern shows GRAP, designated to respond to severe pollution, did not result in improvements.The need for long-term emission reductionKumar’s analysis argued that if emissions contributing to winter pollution remain high, severe episodes are likely to recur, requiring emergency restrictions to be imposed repeatedly. It called for emission reduction as the primary objective of the capital’s long-term strategy.“A long-term clean-air strategy should therefore place emission reduction at source as the primary objective, with GRAP serving as the last line of defence when severe pollution still occurs. That requires action across the NCR airshed and across the range of pollution sources, rather than relying mainly on temporary restrictions or concentrating primarily on a few sectors,” the analysis read.The analysis also acknowledged that AQI is influenced by weather conditions as well as emissions, thus not establishing a direct link between GRAP restriction and changes in pollution levels. It however urged that the central question should be what sustained steps can be taken by policymakers to reduce emissions and prevent the need for severe GRAP measures.