IT is 6.30 in the morning and you are starting your day in Gurugram. A thin fog, more like a mist, hangs low outside. You check your phone for the weather report to see if there could be rain coming. Along with the weather, you check the Air Quality Index (AQI). It is at 162 at the level of unhealthy. This despite your neighbourhood being leafy and greener than most. In Delhi, where you will spend much of your day, the AQI is 159 at that hour and you wonder how much worse it will get.

Tracking of air pollution has become an everyday activity, particularly so for people in the National Capital Region (NCR). Data is collected from thousands of monitoring devices and made available in real time, instantly, on the screen of your phone. Comparisons are now possible between cities and regions.