Jump to main content or area navigation.

Contact Us

Air Trends

Sulfur Dioxide

National Trends in Sulfur Dioxide Levels
Regional Trends in Sulfur Dioxide Levels
Local Trends in Sulfur Dioxide Levels

National Trends in Sulfur Dioxide Levels

Using a nationwide network of monitoring sites, EPA has developed ambient air quality trends for sulfur dioxide (SO2). Trends starting in 1980, 1990, and 2000 are shown here. Under the Clean Air Act, EPA sets and reviews national air quality standards for SO2. Air quality monitors measure concentrations of SO2 throughout the country. EPA, state, tribal and local agencies use that data to ensure that SO2 in the air is at levels that protect public health and the environment. Nationally, average SO2 concentrations have decreased substantially over the years. For information on SO2 standards, sources, health effects, and programs to reduce SO2, please see www.epa.gov/airquality/sulfurdioxide/.

Sulfur dioxide air quality between 1980 and 2012, based on the 99th percentile of daily max 1-hour averages.  Chart shows a range of concentrations in 57 monitoring sites nationwide, with the average decreasing 78% from 1980 to 2012.

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)


Sulfur dioxide air quality between 1990 and 2012, based on the annual arithmetic average.  Chart shows a range of concentrations in 163 monitoring sites nationwide, with the average decreasing 72% from 1990 to 2012.

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)


Sulfur dioxide air quality between 2000 and 2012, based on the annual arithmetic average.  Chart shows a range of concentrations in 260 monitoring sites nationwide, with the average decreasing 54% from 2000 to 2012.

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 Sulfur Dioxide 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.


Note: The Northwest region does not have enough data to construct a regional trend.

Source: NOAA National Climatic Data Center

Local Trends in Sulfur Dioxide 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, 478 KB) using Google Earth or another KML browser. 

 Sulfur dioxide monitors that meet mimimum trends completeness criteria
 Sulfur dioxide monitors that have some data during the trend period but do not meet the mimimum trends completeness criteria

Related Links | Acronyms | Hardcopies

Jump to main content.