Comment submitted by National Association of Clean Air Agencies (NACAA)

Summary: The National Association of Clean Air Agencies (NACAA) supports the proposed rule but argues that states with existing State Implementation Plans (SIPs) should not be required to adopt the new definitions if they choose to keep their current, more stringent rules. They contend that because the proposed revisions are less restrictive, states have the legal right under the Clean Air Act to maintain their own standards.