An updated report published by the Centre for Research on Energy and Clean Air (CREA), has confirmed that Byrnihat, located on the Assam-Meghalaya border, was the most polluted city in India during the first six months of 2025, followed by Delhi in the second spot. This report is based on air quality data provided by the Continuous Ambient Air Quality Monitoring Stations (CAAQMs) in 293 Indian cities. The findings pose serious credibility issues to India’s air pollution problem, and in particular, that of cities.
Conclusion: Most polluted cities
The report reveals that Byrnihat had an average PM 2.5 level of 133 micrograms per cubic metre (ug/m3) well above the national prescribed level of 40 ug/m3. Delhi had an average of 87 ug/m3, ranking it the second-most polluted city in India.
Other polluted cities included Hajipur (Bihar) Ghaziabad (Uttar Pradesh) and Gurgaon (Haryana). Other cities in the report partially included Sasaram, Patna and Rajgir in Bihar and Talcher and Rourkela in Odisha.
What is PM 2.5 and why does it matter?
PM 2.5 refers to air particles that are smaller than or equal to 2.5 micrometers, less than the width of a human hair. PM 2.5 can penetrate the lung and enter into the body’s blood stream, creating chronic health issues, such as, asthma, heart disease and respiratory infections.
According to the National Ambient Air Quality Standards (NAAQS), an appropriate level of a safe PM 2.5 is 40 ug/m3. Many cities levels are well above the NAAQS recommended levels.
Source of Data and Monitoring
The CREA study used data from CAAQMS which monitor air quality in 293 cities. The summary is as follows:
• 122 cities exceeded the national standards for air quality in India.
• 117 cities were under the safe limit.
• 259 cities had already crossed the yearly PM 2.5 limit by June, so it appears these cities will remain in the unsafe zone for the rest of the year.
• The National Clean Air Programme (NCAP) is monitoring 131 cities. 98 of these cities have CAAQMS installed.
The Cleanest Cities in India
On another positive note, Aizawl, the capital of Mizoram was noted as the cleanest city with an average PM 2.5 level of 8 ug/m3, although still above the WHO safe to breathe level of 5 ug/m3.
Additional clean cities included:
• Tirupur and Tirunelveli in Tamil Nadu
• Bareilly and Vrindavan in Uttar Pradesh
• Maihar in Madhya Pradesh
• Imphal in Manipur
• Chamarajanagar and Chikkamagaluru in Karnataka
