To amend the Clean Air Act to modify the application of certain provisions regarding the inclusion of entire metropolitan statistical areas within nonattainment areas, and for other purposes.

Amends the Clean Air Act to revise procedures regarding the inclusion of metropolitan statistical areas (MSAs) or consolidated MSAs in nonattainment areas. Requires the Administrator of the Environmental Protection Agency to revise the boundaries of all nonattainment areas that included such MSAs before this Act's enactment to exclude all counties within such MSAs that do not contribute significantly to a violation of the national ambient air quality standard concerned.