[Code of Federal Regulations] [Title 40, Volume 5] [Revised as of July 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR58.50] [Page 217] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 58--AMBIENT AIR QUALITY SURVEILLANCE--Table of Contents Subpart F--Air Quality Index Reporting Sec. 58.50 Index reporting. (a) The State shall report to the general public through prominent notice an air quality index in accordance with the requirements of appendix G to this part. (b) Reporting is required by all Metropolitan Statistical Areas with a population exceeding 350,000. (c) The population of a Metropolitan Statistical Area for purposes of index reporting is the most recent decennial U.S. census population. [64 FR 42547, Aug. 4, 1999]