A study found that unfavourable weather could keep Delhi-NCR's pollution elevated for five days. The findings underline the need for sustained emission cuts alongside weather-sensitive pollution controls.A hazy view of the residential area, in New Delhi, Wednesday, Oct.

21, 2026. (PTI Photo) Delhi-NCR residents may have to endure several days of toxic air when weather conditions prevent pollutants from dispersing, with pollution levels potentially remaining elevated for up to five days, according to a new study published in the journal Environmental Pollution.The study, titled “Impact of meteorological drivers on air quality index: A case study from Delhi”, found that temperature was the most influential meteorological factor affecting the city's air quality over time.Researchers said pollution in Delhi was driven largely by the accumulation of pollutants and their subsequent dispersion, underlining the importance of reducing emissions at their source.Researchers from Jamia Millia Islamia, the Delhi Pollution Control Committee and the Central Pollution Control Board analysed daily Air Quality Index (AQI) readings and weather data from January 2017 to December 2024. The analysis covered temperature, rainfall, relative humidity and wind speed.

The monthly analysis showed that 'very poor' and 'severe' air quality days increased between October and February. Delhi recorded an average AQI of around 210 during the eight-year period, placing it in the 'poor' category under the CPCB's classification.

Although the average AQI in 2024 was 8.14 per cent lower than in 2017, severe pollution episodes continued, particularly during winter.The study found that past AQI values accounted for around 93.3 per cent of variations in air quality during the first five days of analysis. This contribution declined to about 81.1 per cent by the 16th day, highlighting how existing pollution levels influence subsequent air quality.Temperature accounted for 13.235 per cent of AQI variation over the 16-day analysis, followed by rainfall at 2.127 per cent.

Wind speed contributed 3.271 per cent during the second analysis period, while relative humidity consistently accounted for less than 2 per cent.During winter, low temperatures, a shallow atmospheric boundary layer and temperature inversions can trap pollutants close to the ground. Stronger winds can help disperse pollution, while rainfall washes pollutants out of the atmosphere and reduces the resuspension of road dust.NOVEMBER EMERGES AS THE WORST MONTHThe monthly analysis showed that 'very poor' and 'severe' air quality days increased between October and February.

November recorded the highest proportion of 'very poor' days at 53.8 per cent and 'severe' days at 24.6 per cent.In contrast, satisfactory air quality days accounted for 62.7 per cent in July and 60.5 per cent in August, when monsoon rainfall helped wash pollutants from the atmosphere.The researchers cautioned that the study examined four meteorological variables but did not directly account for traffic, industrial activity or crop residue burning.They called for sustained emission cuts, stronger public transport systems, wider adoption of electric buses and taxis, and coordination between states to tackle stubble burning.The persistence of severe pollution episodes, they said, highlights the need for a comprehensive approach that addresses both weather-driven accumulation and emissions at their source.- Ends