Data Requirements Rule for the 2010 1-Hour Sulfur Dioxide (SO2

The Environmental Protection Agency (EPA) is promulgating a rule directing state and tribal air agencies (air agencies) to provide data to characterize current air quality in areas with large sources of sulfur dioxide (SO2) emissions to identify maximum 1-hour SO2 concentrations in ambient air. The final rule establishes minimum criteria for identifying the emissions sources and associated areas for which air agencies are required to characterize SO2 air quality. Air agencies remain free to also characterize air quality in additional areas beyond those required to be characterized under the rule. The final rule also sets forth a process and timetables by which air agencies must characterize air quality through ambient monitoring and/or air quality modeling techniques and submit such data to the EPA. The EPA has issued separate non-binding draft technical assistance documents recommending how air agencies should conduct such monitoring or modeling. The air quality data developed by air agencies pursuant to this rule may be used by the EPA in future actions to evaluate areas' air quality under the 2010 1- hour SO2 National Ambient Air Quality Standard (NAAQS), including area designations and redesignations, as appropriate.