Delhi worst, Kolkata best: CSE study ranks air quality in Indian metros

Kolkata city

Kolkata has emerged as the Indian metro with the cleanest air quality, overtaking its larger rivals over a four-year period, according to new research published by the Centre for Science and Environment (CSE). The report, highlighted by TOI, places the city well ahead of Delhi, Mumbai, Bengaluru, Hyderabad and Chennai for the number of days with 'very good' and 'satisfactory' air quality out of 1,550 days tracked between January 2021 and March 2025.

Analysis by the CSE, detailed in its annual State of India’s Environment in Figures 2025, recorded Kolkata having 791 days where air quality was described as either 'very good' or 'satisfactory.' The Bengal capital enjoyed 368 days of 'very good' and 423 days of 'satisfactory' air, with only 231 days falling under the 'moderate' category and, notably, not a single day rated as 'severe.' This stands in sharp contrast to Delhi, which endured 284 days of 'severe' air, the highest in the country.

The CSE findings underline the health implications for citizens, noting that with just 513 'poor' and 15 'very poor' air quality days, Kolkata residents were largely shielded from prolonged hazardous pollution. The city’s relative success has been credited to a combination of policies and innovations steered by local authorities and the West Bengal Pollution Control Board (PCB).

PCB chairman Kalyan Rudra was cited by TOI as saying that the city’s improved air quality was due to a series of strategic actions, including "using sprinklers to prevent dust-resuspension, deploying fire tenders at landfills, biomining of garbage heaps, shifting to clean fuel, use of smokeless chullah by food vendors and urban and rural poor." He added, "Kolkata’s success story is a result of several key policy decisions by PCB and their effective implementation by the local bodies." Rudra, however, emphasised that persistent efforts are needed to further reduce emissions.

CSE’s air quality expert Anumita Roychowdhury noted that the National Clean Air Programme (NCAP) has played a major role in monitoring pollution and enforcing remedial action. Under this system, cities update the Central Pollution Control Board’s PRANA portal every quarter, setting targets, outlining the scope for action and documenting funding needs. Roychowdhury was quoted by TOI: "The performance-linked NCAP framework helped lay the foundations of national air quality management in non-attainment cities, such as Kolkata."

In southern metros like Bengaluru, Hyderabad and Chennai, the report observed a preponderance of 'poor' air quality days, though 'very poor' or 'severe' readings were absent, largely attributed to local weather and a distinct mix of pollution sources. Vehicular emissions, dust and industrial activity remain persistent contributors there.

Meanwhile, Mumbai’s air quality showed a hybrid pattern. The financial capital recorded 145 days of 'very good,' 637 days of 'satisfactory,' 118 'moderate' and 649 'poor' AQI days. The city narrowly escaped the worst air, with just one 'very poor' day and no 'severe' days on record during the assessed period.