US HB6409

Amends the Clean Air Act to clarify that emissions from outside the United States include both human-caused and natural emissions when determining air quality attainment status

Prohibits EPA from designating an area as nonattainment for any air quality standard if the state demonstrates the area would meet the standard but for foreign emissions

Exempts states from Clean Air Act sanctions and fees under sections 179 and 185 for Severe/Extreme ozone areas and Serious particulate matter areas if nonattainment results from emissions outside the area, exceptional events, or mobile sources beyond state control

Requires states seeking exemption from sanctions to renew their demonstration to EPA at least once every 5 years

Preserves underlying state obligations to implement measures to attain air quality standards despite sanction exemptions