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Interstate Air Pollution Transport

Interstate Air Pollution Transport

What's New
  • November 21, 2014 - EPA issued a ministerial rule that aligns the dates in the CSAPR rule text with the revised court-ordered schedule, including 2015 Phase 1 implementation and 2017 Phase 2 implementation. In a separate ministerial action, EPA issued a NODA, as required by CSAPR, that aligns the final CSAPR default allowance allocation years with the revised court-ordered schedule.
  • October 23, 2014 - The U.S. Court of Appeals for the D.C. Circuit ordered that EPA's motion to lift the stay of the Cross-State Air Pollution Rule be granted.
  • June 26, 2014 - The U.S. government filed a motion with the U.S. Court of Appeals for the D.C. Circuit to lift the stay of the Cross State Air Pollution Rule. While the Court considers the motion, CAIR remains in place and no immediate action from States or affected sources is expected.
  • April 29, 2014 -The U.S. Supreme Court reversed the D.C. Circuit opinion vacating CSAPR. EPA is reviewing the opinion.
  • January 8, 2014 - EPA published its 2018 base year emissions modeling platform for public comment. These data will support the assessment of interstate air pollution transport.

    • The Clean Air Act's "good neighbor" provision requires EPA and states to address interstate transport of air pollution that affects downwind states' ability to attain and maintain National Ambient Air Quality Standards (NAAQS).

    A combination of local emissions and emissions from upwind sources impacts air quality in any given location. Emissions of sulfur dioxide (SO2) and nitrogen oxides (NOX) can react in the atmosphere to form fine particle (PM2.5) pollution. Similarly, NOX emissions can react in the atmosphere to create ground-level ozone pollution. These pollutants can travel great distances affecting air quality and public health locally and regionally. The transport of these pollutants across state borders makes it difficult for downwind states to meet health-based air quality standards for PM2.5 and ozone.

    Next Steps in Addressing Interstate Air Pollution Transport Under the Clean Air Act:

    Together with our state partners, EPA is assessing the next steps to address interstate air pollution transport under the Clean Air Act. Information pertaining to stakeholder outreach and Agency actions will be posted to this website as available.

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