Delhi Most Polluted, Patna Second: New Report Reveals India's Worsening Air Crisis
The Climate Trends report ranks Delhi and Patna as India's most polluted cities with worsening annual trends.
A new analysis by Climate Trends has identified Patna as the second-most polluted city in India after Delhi, highlighting persistent concerns about air quality across the country. The research-based organisation analysed pollution patterns using air quality monitoring data from the Central Pollution Control Board (CPCB) and studied how weather conditions influence the persistence of fine particulate matter (PM2.5) across major Indian cities.
The report examined air quality data from 2024–2025 along with meteorological clustering to distinguish between pollution caused directly by emissions and pollution influenced by weather patterns. The study focused on six major Indian cities — Delhi, Patna, Kolkata, Mumbai, Chennai and Bengaluru — to understand how atmospheric conditions affect the concentration and persistence of PM2.5 pollution.
According to the report, Delhi continues to face the most severe air pollution crisis in the country, recording the highest annual average PM2.5 levels and the longest periods of “severe” or “emergency” air quality. The city’s pollution levels are driven by a combination of local emissions and regional factors, including seasonal weather patterns that trap pollutants in the atmosphere.
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The analysis found that Patna ranks second in pollution levels, with consistently high PM2.5 concentrations attributed to strong atmospheric stagnation. Researchers warned that the situation signals an intensifying air pollution crisis across the eastern part of the Indo-Gangetic Plain, where weather conditions often prevent pollutants from dispersing effectively.
While cities such as Bengaluru and Chennai historically recorded relatively lower pollution levels, the report noted signs of air quality deterioration during winter months, indicating a new vulnerability trend. Meanwhile, both Mumbai and Chennai experienced a rise in their annual average pollution levels in 2025, suggesting that air pollution concerns in these cities may extend beyond seasonal spikes.
Sagnik Dey, head of the Centre for Atmospheric Sciences at Indian Institute of Technology Delhi, said persistent PM2.5 exceedances in northern cities are strongly linked to wind speeds below 1 metre per second and high relative humidity. Such conditions create stagnation episodes that trap pollutants and increase public exposure to hazardous air.
The report also emphasised that ventilation efficiency plays a key role in determining differences in pollution levels between cities. However, it cautioned that the current evaluation framework of the National Clean Air Programme may not fully account for the impact of meteorological conditions when assessing pollution trends, potentially distorting interpretations of policy effectiveness.
To address these challenges, the study recommended several reforms for the programme’s Phase III implementation, including winter-specific pollution targets, meteorology-adjusted assessment metrics, weather-triggered action plans and improved airshed-based regional planning to tackle pollution more effectively.
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