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Air Trends

Carbon Monoxide

National Trends in CO Levels
Regional Trends in CO Levels
Local Trends in CO Levels

National Trends in CO Levels

Using a nationwide network of monitoring sites, EPA has developed ambient air quality trends for carbon monoxide (CO). Trends starting in 1980, 1990, and 2000 are shown here. 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 www.epa.gov/airquality/carbonmonoxide.

Carbon monoxide air quality between 1980 and 2014, based on the annual second maximum 8-hour average. Chart shows a range of concentrations in 74 monitoring sites nationwide, with the average decreasing 85% from 1980 to 2014. Most of the sites have had concentrations below the national standard since the early 1990s.

How to Interpret the Graphs
View the chart data in Microsoft Excel  (Download Excel Viewer) Exit EPA Disclaimer
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Carbon monoxide air quality between 1990 and 2014, based on the annual second maximum 8-hour average. Chart shows a range of concentrations in 120 monitoring sites nationwide, with the average decreasing 77% from 1990 to 2014. Most of the sites have had concentrations below the national standard since the early 1990s.

How to Interpret the Graphs
View the chart data in Microsoft Excel  (Download Excel Viewer) Exit EPA Disclaimer
View the chart data in HTML  (New window opens)


Carbon monoxide air quality between 2000 and 2014, based on the annual second maximum 8-hour average. Chart shows a range of concentrations in 189 monitoring sites nationwide, with the average decreasing 58% from 2000 to 2014. Most of the sites have had concentrations below the national standard since the early 1990s.

How to Interpret the Graphs
View the chart data in Microsoft Excel  (Download Excel Viewer) Exit EPA Disclaimer
View the chart data in HTML  (New window opens)


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.

Source: NOAA National Climatic Data Center

Local Trends in CO LevelsNote to users of screen readers: The Local Trends information is available on the web only as graphical images. Please call 919-541-5224 for assistance.

Air quality trends can vary from one area to another. Local trends can be viewed at individual monitoring locations in the map below or in this KML file (KML, 352 KB) using Google Earth or another KML browser. 

 Carbon monoxide monitors that meet mimimum trends completeness criteria
 Carbon monoxide monitors that have some data during the trend period but do not meet the mimimum trends completeness criteria for 1990-2012

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