Sections 165 and 173 of the CAA specifically note that any change in pollution levels from an existing source triggers NSR and accompanying technological upgrades. Nothing in the rulemaking's proposed definition based on cost of changes or maintenance address this clear language of Congress. --Victor B. Flatt, A.L. O'Quinn Chair in Environmental Law, University of Houston Law Center, written comments submitted to EPA on February 26, 2003.

Taken together, the two proposed exclusions from NSR would allow many grandfathered air polluters to operate indefinitely without installing state-of-the-art pollution control equipment. This would contravene the purpose of NSR, which is to ensure that grandfathered facilities eventually do improve their environmental performance. --Michael M. O'Hear, Assistant Professor, Marquette University Law School, written comments submitted to EPA on March 2, 2003.