Currently, our Major Cities Ranking (or just 'Ranking', as seen on our app) is made up of around 80 major cities, although this may continue to grow as we receive requests to add additional locations.
Our website shows the top 10 on any given day, whilst using our air quality app (either Android or iOS), you can scroll down and view the full list, 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 our air quality data from a combination of government monitoring stations, as well as a network of crowdsourced AirVisual monitors, whose readings we carefully validate.
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 prioritise 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!