The Air Quality Index (AQI) was developed by the US Environmental Protection Agency (EPA) to report air quality. Every day the AQI tells you how clean or polluted your outdoor air is, along with associated health effects that may be of concern. The AQI translates air quality data into numbers and colors that help people understand when to take action to protect their health.

All the AQI data in this project was collected from The World Air Quality Index project, which is a social enterprise project started in 2007 and initiated by the US Embassies in China. Although the base team is located in Beijing, its mission is to promote air pollution awareness and provide a unified air quality information for the whole world.

Source: http://aqicn.org/