Winter air better but Kol 14th among 22 state caps
Times of India | 7 March 2025
123 Kolkata: This winter (2024-25), from Oct 1 to Feb 28, Kolkata emerged as the 9th most polluted among 22 capital cities in India as far as PM2.5 count in the ambient air is concerned, finds an analysis by the Centre for Research on Energy and Clean Air (CREA). Despite a significant improvement in its air quality compared to previous years, the city's PM2.5 concentration this winter was 63 micrograms per cubic meter (µg/m³) while the national ambient air quality standard (NAAQS) is 40 µg/m³.
CREA is an independent research organisation focused on revealing the trends, causes, and health impacts of air pollution.
However, two Bengal cities, Durgapur and Asansol, featured well in the list of top 10 polluted cities in India with their PM2.5 count being 97 and 98 µg/m³. Rajasthan, Bihar, and West Bengal were among the states where all monitored cities exceeded NAAQS. Bengal has six such non-attainment cities under the National Clean Air Programme (NCAP), like Kolkata, which do not conform with the NAAQS annually.
"Delhi remained the most polluted city in India, recording a winter-average PM2.5 concentration of 159 µg/m³. Byrnihat closely followed, with an average PM2.5 level of 157 µg/m³. A total of 173 out of 238 monitored cities recorded PM2.5 levels above India's NAAQS of 40 µg/m³. Rajasthan, Bihar, and West Bengal were among the states where all monitored cities exceeded NAAQS annually," said CREA analyst Manoj Kumar.
Aizawl (Mizoram) with 7 µg/m³ and Gadag (Karnataka) with 17 µg/m³ PM2.5 concentration in the air were two cleanest cities this winter. Despite such performance, they could not match the WHO standard of 5 µg/m³. All top polluted cities are in the Indo-Gangetic Plain, while all clean air cities are either in north-east or in south India.
PM2.5 is considered the most harmful component when determining a city's Air Quality Index (AQI) because these tiny particles are so small that they can easily penetrate deep into the lungs, reaching the bloodstream and causing significant health issues like respiratory problems, cardiovascular disease, and even premature death, making it a major concern for human health compared to larger particulate matter.
Continuous ambient air quality monitoring station (CAAQMS) data from the Central Pollution Control Board was analysed for winter 2024-25. Only cities with at least 80% data availability during this period were considered for the analysis. In winter 2024-25, 173 out of 238 cities with more than 80% of the days with CAAQMS data recorded PM2.5 concentrations above India's National Ambient Air Quality Standards (NAAQS) of 40 µg/m³. None of the 238 cities complied with the World Health Organization's (WHO) safe guideline concentration of 5 µg/m³.
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