According to the Central Pollution Control Board’s (CPCB) 4 pm bulletin, Delhi recorded a 24-hour average AQI of 261, classified as “poor”, on Sunday. This marked a significant decline from 117, which fell in the “moderate” category, a day earlier.
On Friday, the AQI had dropped to 60 after heavy rain washed pollution out of Delhi’s air, giving the national capital its cleanest October day in four years.
Of Delhi’s 59 air quality monitoring stations, data was available for 58. Among these, 36 recorded “very poor” air quality, while Jahangirpuri was the only station to fall in the “severe” category, with an AQI of 417.
Five monitoring stations recorded “moderate” air quality, while the remaining stations reported readings in the “poor” category.
The CPCB classifies an AQI of 0-50 as “good”, 51-100 as “satisfactory”, 101-200 as “moderate”, 201-300 as “poor”, 301-400 as “very poor” and 401-500 as “severe”.
PM2.5 emerged as the primary pollutant at most monitoring stations across the city.
At 6 am on Monday, the CPCB listed PM2.5 as the primary pollutant at 51 of the 58 reporting stations, while PM10 was recorded at the remaining seven.
At the same time a day earlier, PM2.5 was the main pollutant at 46 of 57 stations, while PM10 was recorded at 11 stations.
Delhi last recorded “very poor” air quality on February 11 this year, when the 24-hour average AQI stood at 305. Before that, the AQI had reached 339 on February 4.
The latest deterioration comes a week ahead of Diwali, when firecracker bursting typically adds to the pollutant load in the Capital’s air.
However, the figures may not be directly comparable, as stubble burning has increasingly shifted to later hours of the day.
About 98 per cent of the fire heat recorded by Meteosat in 2025 came after 3 pm, compared with 94 per cent in 2024.
Figures from both years are likely to be undercounts, as most burning now takes place after the satellite’s pass at around 1.30 pm.
Meteorologist Navdeep Dahiya warned that the smog season had begun, with unfavourable weather conditions likely to worsen pollution levels in the coming days.
With air quality already deteriorating to the “very poor” category and the AQI crossing 300, Delhi is facing a fresh spell of pollution after last week’s rain temporarily improved conditions.
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