What determines the major cities ranking?
Currently, our Major Cities 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.
The list contains 1, 2 or more relevant cities per country with the goal of providing a worldwide context about the air quality for those cities. The Major Cities Ranking is NOT meant to include all the cities in the world. For the complete city ranking, please refer to the annual most polluted city ranking report.
Using either our website or air quality app (Android or iOS), you can scroll down and view the full list of selected cities, ranked in order of hourly AQI. The current list has tried to focus on major cities with a population of >300,000 people, and which represent a wide range of countries to allow global contrast.
We report air quality data from a combination of government monitoring stations, as well as a network of crowdsourced AirVisual monitors, whose readings we carefully validate. You can always check which data sources are being used to calculate each city's air quality data, as we display these transparently. Learn how to check different locations' data sources here:
The data shown for each major city in the major city ranking, is an average (median) value from all the stations in that city, that monitor PM2.5 as one of their pollutants. We prioritize readings from stations that measure PM2.5, since this is widely regarded as the pollutant which is most hazardous to human health.
If you think your city should be added to the major cities ranking, let us know!