During the last winter, 204 out of 238 Indian cities recorded average PM2.5 (a chief pollutant) levels above the Indian standard of 40 g/m³, as per the Central Pollution Control Board (CPCB) data analysed by the Centre for Research on Energy and Clean Air (CREA).

Ghaziabad was the most polluted city, recording an average PM2.5 concentration of 172 g/m³, followed by Noida (166 g/m³), and Delhi (163 g/m³), as per CREA, a Finland-based independent research group.