Delhi’s average AQI falls, but everyday air gets more polluted, says study

New Delhi: Delhi’s air quality showed an apparent improvement this autumn, but a closer look at the numbers reveals a more complicated picture. The city experienced fewer extreme pollution days, while its typical day became more polluted, a new analysis reveals.

The assessment by Climate Trends, a research-based initiative, compared Delhi’s air quality between Sept 15 and Oct 23 across 2024, 2025 and 2026. It found that the mean air quality index, the average of daily AQI readings across the period, fell 15.8%, from 169.3 in 2025 to 142.6 in 2026. However, the median AQI, which represents the middle reading and better reflects a typical day, rose 14.1%, from 135 to 154.

The number of days with AQI above 200 dropped from 10 in 2025 to just three in 2026, while the maximum daily AQI fell from 353 to 245. Yet the median AQI rose from 135 to 154, even as the mean fell from 169.3 to 142.6. The figures suggest that Delhi experienced fewer severe pollution episodes, but its typical daily air quality did not improve.

The findings also challenge the tendency to explain Delhi’s autumn pollution primarily through stubble burning in neighbouring states. Satellite-detected crop-residue fires in Punjab and Haryana fell marginally from 201 in 2025 to 193 in 2026, a decline of 4%. Yet the same-day correlation between fire activity and Delhi’s AQI weakened sharply, from 0.62 to 0.17.