Air Quality Index is an easy-to-use application that is available for free and provides the current AQ index value for over 60 countries (1000 cities) worldwide. This software tool functions on tablets, phones, and smartphones with Android 6 or newer in portrait mode and that have an Internet connection. It firstly obtains your local coordinates (latitude and longitude) from the device's GPS and then retrieves the AQ index from a good Internet server (aqicn.org). The index value indicates the level of air pollution in your area as measured by the nearest monitoring station in your city. It includes the measurements of all known pollutants (PM 2.5, PM10, NO2, CO, SO2, O3) and its level means:

0 - 50: (Good) - Air quality is considered satisfactory, and air pollution poses little or no risk.
51 - 100: (Moderate) - Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.