| Rank | City |
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Data Source and Description
●Air quality data of mainland China, Hong Kong, Macao, and Taiwan obtained from local government agencies for ecological environment and environmental monitoring.
●Worldwide air quality data comes from aqicn, AirNow, OpenAQ and local environmental agencies.
●For the stations at mainland China, the Air Quality Index (AQI) value adopts the Chinese standards. Other stations adopt their local standards or U.S. standards.
●O3-8H is the arithmetic average of the hourly ozone concentration values within 8 hours back to the current time. For sites that do not have publicly released O3-8H values from ecology and environmental departments, the Blue Map calculates and presents the O3-8H data based on statistical method in the "HJ 663-2013 Technical Specification for Ambient Air Quality Assessment (Trial)". Annual National Environmental Data and Statistics59