Air Trends

Carbon Monoxide Trends

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National Trends in CO Levels

Using a nationwide network of monitoring sites, EPA has developed ambient air quality trends for carbon monoxide (CO). Under the Clean Air Act, EPA sets and reviews national air quality standards for CO. Air quality monitors measure concentrations of CO throughout the country. EPA, state, tribal and local agencies use that data to ensure that CO remains at levels that protect public health and the environment. Nationally, average CO concentrations have decreased substantially over the years. For information on CO standards, sources, health effects, and programs to reduce CO, please see
How to Interpret the Graphs



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Regional Trends in CO Levels

Air quality trends can vary regionally. The following climatically consistent regions within the contiguous United States provide a relevant way to look at regional trends in air quality.

U.S. Climate Regions from NOAA's National Climatic Data CenterSource: NOAA National Climatic Data CenterSelect a region: (graph appears below)

Note: The Northern Rockies and Plains region does not have enough data to construct a regional trend for carbon monoxide.


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