Seasonal shifts, not trends, drive urban air pollution extremes in

A new study argues that seasonal swings—not long-term “trends”—drive extreme urban air pollution across India’s northeast, where conditions often get less attention than major plain-city metros. Researchers at The Assam Royal Global University in Guwahati analyzed three years of daily Air Quality Index (AQI) records from 2022 to 2024 across eight urban centers, using publicly available data from India’s Central Pollution Control Board and state agencies. Published in Air Quality, Atmosphere & Health, the work finds pollution worsens in winter valley cities and improves during the monsoon. Valley locations such as Agartala, Guwahati and Imphal repeatedly recorded AQI above 100 on 40–50% of days, and over 200 on more than 20%.