Sec. 160. The purposes of this part are as follows:
     (1)  to protect public health and welfare from any actual or
  potential adverse effect which in  the Administrator's judgment
  may  reasonably be  anticipate to occur  from air  pollution or
  from exposures  to pollutants in other  media, which pollutants
  originate  as emissions  to the  ambient  air), notwithstanding
  attainment and maintenance of  all national ambient air quality
  standards;
     (2) to preserve, protect, and enhance the air quality in na-
  tional  parks, national  wilderness areas,  national monuments,
  na-tional  seashores, and  other areas  of special  national or
  region-al natural, recreational, scenic, or historic value;
     (3)  to insure that economic  growth will occur  in a manner
  consistent with the preservation of existing clean air resourc-
  es;
     (4)  to assure that emissions  from any source  in any State
  will not interfere with any portion of the applicable implemen-
  tation plan to prevent significant deterioration of air quality
  for any other State; and
     (5)  to  assure that  any decision  to permit  increased air
  pollution in any  area to  which this section  applies is  made
  only after careful evaluation of all the consequences of such a
  deci-sion  and  after  adequate  procedural  opportunities  for
  informed public participation in the decisionmaking process.
[42 U.S.C. 7470]