Govt hails Jan–Nov AQI gains, leaves out December Delhi’s dirtiest month

The Delhi government has claimed that the national capital recorded its best air quality in eight years in 2025, citing improvements in the average Air Quality Index (AQI) between January and November . However, an analysis of monthly AQI data shows that the government’s assessment excludes December , which emerged as the most polluted month , raising questions over the selective framing of the claim.

Environment Minister Manjinder Singh Sirsa said the improvement reflected the government’s sustained, multi-front efforts to tackle pollution, including dust control, vehicle emission checks and coordination with neighbouring states. According to the data cited by the government, the January–November average AQI for 2025 stood at around 160 , significantly better than the corresponding period in previous years about 199 in 2022 , 191 in 2023 , and 202 in 2024 .

The improvement was driven by consistently lower pollution levels from February to October , covering the summer and monsoon months, when AQI readings in 2025 were markedly better than in the previous three years. These gains helped bring down the overall average for most of the year and formed the basis of the government’s claim.

However, the picture changes sharply in winter. December 2025 recorded an average AQI of 366 , making it the worst December in the four-year comparison , and worse than December levels in 2022, 2023 and 2024. The month saw prolonged spells of ‘very poor’ and ‘severe’ air quality , driven by unfavourable meteorological conditions, local emissions and seasonal factors.

Experts note that while the government’s claim is statistically correct for the January–November period , excluding December, traditionally Delhi’s most critical pollution month presents an incomplete view of the city’s air quality challenge. Public perception of worsening pollution is shaped largely by winter conditions, particularly November and December, when health impacts are most severe and visibility drops dramatically.

When December is included, the full-year average AQI for 2025 works out to around 177 , still better than 2022 (210) , 2023 (205) and 2024 (215) . However, this improvement is largely attributable to cleaner air during the first ten months of the year, rather than any breakthrough in controlling winter pollution.

The data suggests that while structural improvements may be taking hold outside the winter season , Delhi continues to struggle with severe pollution during November and December , underlining the need for stronger and more targeted interventions during the cold months, rather than selective presentation of annual averages.