The system for comprehensive national air quality monitoring established under CAA § 319, 42 USC § 7619.

Engine Manufacturers Ass'n v. EPA, 88 F.3d 1075, 1099 (D.C. Cir. 1996).EPA can regulate due to aesthetic harm such as reduced visibility and soiling of property because that is a harm to public welfare.

Sierra Club v. Leavitt, 368 F.3d 1300, 54 (11th Cir. 2004).EPA's claim that it is impossible to meet a statutory deadline due to competing demands does not justify a determination that a schedule is impossible because Congress, in setting deadlines, has determined the relative priorities of various programs.

National Mining Ass'n v. EPA, 59 F.3d 1351, 1354-1357 (D.C. Cir. 1995) (per curiam).In order to aggregate emissions from different facilities, the facilities need not fall into a similar industrial classification, or be the same souce category, or come withing the same Standard Industrial Classification.