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page html_indicator.xsl Current_Ozone_Levels_USA
Ground-level ozone, widely known as smog, is formed when sunlight triggers chemical reactions between nitrogen oxide and volatile organic compounds emitted from industrial plants, electric utilities, motor vehicles and other sources. Ozone pollution travels with the breeze and can affect downwind counties and states. Breathing ozone particularly irritates the respiratory tract. Short-term exposure can exacerbate asthma and trigger attacks and other health problems. The U.S. Environmental Protection Agency lowered the health-based ozone standard from a maximum daily 8-hour average of no greater than .075 parts per million to .070 ppm in 2015.
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.