NEW DELHI, March 11, 2026 — Delhi has once again been identified as the most polluted city in India for the 2024-25 period, according to a new report by research group Climate Trends. Based on an analysis of air quality monitoring data from the Central Pollution Control Board (CPCB), the national capital recorded the highest annual PM2.5 levels and the longest stretches of “severe” air quality in the country. Patna followed as the second-most polluted city, confirming an intensifying air quality crisis across the Indo-Gangetic Plain.
The 2024-25 Pollution Leaderboard
The report examined the persistence of PM2.5 pollution across six major Indian cities, including Delhi, Patna, Kolkata, Mumbai, Chennai, and Bengaluru. While Delhi topped the list due to a combination of high local emissions and regional factors, Patna’s ranking was attributed to strong atmospheric stagnation, particularly during the winter months.
| Rank | City | Primary Driver of Pollution |
| 1 | Delhi | High local emissions + Regional factors |
| 2 | Patna | Strong atmospheric stagnation |
| 3 | Kolkata | General Industrial/Vehicle emissions |
| 4 | Mumbai | Seasonal vulnerability (increasing annual averages) |
| 5 | Chennai | Seasonal vulnerability (increasing annual averages) |
| 6 | Bengaluru | Deterioration during winter months |
Weather vs. Emissions: The 40% Impact
A key finding of the study is that meteorological conditions alone can influence pollution levels by as much as 40%. This means that even if emissions remain stable, weather patterns such as low wind speeds, high humidity, and temperature inversions can drastically worsen Delhi AQI levels.
The report noted that between January 2025 and January 2026, the Graded Response Action Plan (GRAP) was imposed 17 times in Delhi to manage severe pollution episodes. This highlights that air quality trends cannot be judged solely by emission changes but must account for weather-driven variability.
Emerging Trends in Coastal and Southern Cities
Historically, cities like Bengaluru and Chennai have enjoyed relatively cleaner air due to marine influences. However, the 2024-25 data shows a worrying new trend:
- Coastal Vulnerability: Both Mumbai and Chennai saw an increase in their annual average pollution levels in 2025.
- Winter Deterioration: Even Bengaluru showed signs of air quality deterioration during the winter months, suggesting that pollution risks are no longer confined to northern India.
Recommendations for National Policy
As the National Clean Air Programme (NCAP) prepares for Phase-III, researchers are calling for a shift in how air quality is managed:
- Meteorology-Adjusted Targets: Policies should evaluate progress based on weather-adjusted data rather than just annual averages.
- Winter-Specific Action Plans: Stagnation-prone regions like the Indo-Gangetic Plain require dynamic, weather-triggered interventions.
- Regional Coordination: Airshed-level management is essential to tackle pollution that crosses city and state boundaries.
The report concludes that without incorporating the role of weather into policy planning, millions of people in northern India will continue to face severe health risks despite improvements in annual average data.
FAQ
Which city was the most polluted in India in 2024-25?
Delhi was the most polluted city, followed by Patna.
Why is Patna ranked so high on the pollution list?
Patna’s high pollution levels are driven by strong atmospheric stagnation, especially in the eastern Indo-Gangetic Plain.
How does weather affect air quality according to the report?
Weather conditions like low wind speed and high humidity can change pollution levels by up to 40%, even if local emissions do not increase.
Is air quality getting worse in southern and coastal cities?
Yes, the report flags an increase in annual average pollution for Mumbai and Chennai, and a winter deterioration trend in Bengaluru.
I’am Siddharth a Air pollution analysts are environmental expert who collect, analyze, and interpret air quality data to identify pollutant sources & develop solutions for reducing atmospheric contamination.