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page html_indicator.xsl Current_Ozone_Levels_USA
Ground-level ozone or smog irritates the lungs and can make it difficult for people to breathe. Ozone is formed when chemicals emitted by motor vehicles, power plants, certain industries and processes, and even vegetation react chemically in the presence of sunlight. Both ozone and some of the pollutants which cause it are carried by the wind, so pollution generated in one state can affect ozone levels in downwind areas.
The U.S. Environmental Protection Agency has established standards requiring that the maximum daily 8-hour average ozone level at any location be no greater than .08 parts per million. The EPA is considering lowering the standard to .07 or .075 parts per billion.
Current Ozone Levels - U.S.A. including all Benchmark Regions
The Ozone reporting season lasts from April to October.
This map from the EPA AirNow website shows the hourly ozone levels at the subset of monitoring locations that report continously on a daily basis. The colors show ozone levels based on the EPA's Air Quality Index. Green means ‘Good’, Yellow means ‘Moderate’, Orange means ‘Unhealthy for Sensitive Groups’ and Red means ‘Unhealthy’. For more information, visit the EPA's AIRNow website.