North Indian cities struggle with poor air quality, while Southern and Western cities breathe easy, reason is…
The analysis is based on annual average Air Quality Index (AQI) data of 11 cities, including Ahmedabad, Bengaluru, Chandigarh, Chennai, Delhi, Kolkata, Lucknow, Mumbai, Pune, Varanasi and Vishakhapatnam. Read here for details
A recent study found that between 2015 and November 2025, not a single major city in India had air quality that could be considered ‘safe’. The capital, Delhi, was consistently the country’s most polluted city during this period. The analysis, titled ‘Air Quality Assessment of Major Indian Cities (2015-2025)’, was published by Climate Trends, a Delhi-based climate research organisation.
The state of air quality in major cities
The analysis is based on annual average Air Quality Index (AQI) data of 11 cities, including Ahmedabad, Bengaluru, Chandigarh, Chennai, Delhi, Kolkata, Lucknow, Mumbai, Pune, Varanasi and Vishakhapatnam. The data paints a bleak picture of air quality in these cities.
Delhi had the worst air quality among 11 cities, with an annual average AQI level exceeding 250 in 2016. Although there has been a decrease in the AQI level since 2019, it still remains far from the safe level. In 2025, the AQI level in Delhi was 180.
Regional differences in air quality
The analysis highlights significant regional differences in air quality. Northern cities like Delhi, Lucknow and Varanasi have much worse air quality compared to western and southern cities like Chennai, Chandigarh, Vishakhapatnam and Mumbai. AQI levels in these cities were consistently higher, especially during the winter months. In contrast, air quality is relatively better in Chennai, Chandigarh, Vishakhapatnam and Mumbai, with AQI levels ranging between 80 and 140.
Why are northern cities more polluted?
The geographical location of northern cities is an important factor contributing to poor air quality. Cities are landlocked and surrounded by the Himalayas, which trap pollutants and prevent them from dispersing. The urban structure of these cities also creates additional ‘surface roughness’ that slows wind speed and limits dispersion.
During the winter months, the situation is made worse by the winter inversion phenomenon, where cold air becomes trapped under warm air, creating an atmospheric ‘cap’ that prevents pollutants from escaping.
Seasonal changes in air quality
The analysis highlights that air quality in northern cities is particularly poor during winter months. During the summer months, monsoon rains and strong westerly winds help disperse pollutants, but the situation changes in the winter months. Delhi is particularly affected due to its location in a wide, flat valley surrounded by the Himalayas. The planet’s boundary layer is thinner during the winter months, trapping pollutants and making them harder to disperse.
