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Sulfur Dioxide (SO2) Pollution

Technical Data and Reports on Sulfur Dioxide (SO2) Measurements and SIP Status

EPA collects data from the states and regions on their air quality and state implementation plan (SIP) progress. This information is compiled in a database, and used to create reports, trend charts, and maps.

SIP status reports

Reports for nonattainment area SIP requirements

Reports for infrastructure SIP requirements

SIPs approved by EPA

Air quality data

  • SO2 Design Values: view statistics that describe the air quality status of a given area relative to the level of EPA's National Ambient Air Quality Standards. These Excel reports are listed by pollutant.
  • AirNow: see real-time air pollution data in the United States.
  • Air Quality Trends for SO2: View SO2 level trends; measured nationally, regionally, and locally; up to 2014.


  • SO2 Designations: Find information on the process EPA, the states, and the tribes follow to designate areas as "attainment" (meeting) or "nonattainment" (not meeting) the sulfur dioxide standards.
  • Green Book: listings of areas designated nonattainment for each NAAQS pollutant. It includes current designation and classification status, area maps, reports, and Federal Register notices.
  • SO2 Data Requirements Rule Source List: Lists of facilities that emit SO2 submitted by state environmental agencies under the Data Requirement Rule to inform future designations, redesignations, or other decisions concerning attainment of standards.