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This is not the current EPA website. To navigate to the current EPA website, please go to www.epa.gov. This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Historical Regulations Impacting the Interstate Transport of Air Pollution

States and EPA have a long history of implementing the good neighbor provision, including developing and implementing regulations that preceded the current Cross-State Air Pollution Rule (CSAPR) programs.  These programs achieved important emission reductions and air quality improvements to help states meet older National Ambient Air Quality Standards (NAAQS).  These historical programs also helped shape the current CSAPR programs.