What determines the major city ranking?

Currently, our Major City Ranking (or just 'Ranking', as seen on our app) is made up of around 90 major cities, although this may continue to grow as we receive requests to add additional locations. 

You can view the full list of live ranked cities using our website or air quality app (either Android or iOS). The current list focuses on major cities with a population of >300,000 people, and which represent a wide range of countries to allow global contrast. 

We report our air quality data from a combination of government monitoring stations, as well as a network of crowdsourced community and AirVisual air quality monitors, whose readings we carefully validate.

The data shown for each city in the major city ranking, is an average (median) value from all the stations in that city. A median value is taken for every pollutant that is measured in that city (which may include PM2.5, PM10, NO2, SO2, CO and O3), and a city-wide AQI value is calculated from these median averages. 
You can view which specific stations are listed for each city by browsing our World Air Quality Map, or simply clicking on the city from within the Major City Ranking. You can see the data sources which are reported by each city and station, listed clearly on each location's page in our website and app.

If you think your city should be added to the major cities ranking, let us know! 

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