Several runners who took part in the Tata Mumbai Marathon (TMM) on Sunday (January 18) raised concerns over a sharp discrepancy between air quality readings recorded on their personal devices and those reported by the Brihanmumbai Municipal Corporation (BMC), questioning the accuracy of the civic body’s Air Quality Index (AQI) calculation method.

According to multiple runners, portable air quality monitors, smartwatches, and mobile-based sensors used during the run showed AQI levels ranging between 200 and 350 at different stretches of the route — readings classified as “poor” to “very poor” as per Central Pollution Control Board (CPCB) standards. In contrast, data displayed on BMC-operated monitoring stations indicated AQI levels largely in the “satisfactory” to “moderate” range, around 80-100, as per CPCB standards.