EPA is revising the level of the primary 8-h standard for O3 to 0.075 ppm, expressed to three decimal places. EPA is revising the secondary 8-h standard for O3 by making it identical to the revised primary standard. EPA is also making conforming changes to the Air Quality Index (AQI) for O3, setting an AQI value of 100 equal to 0.075 ppm, 8-h average, and making proportional changes to the AQI values of 50, 150 and 200. This final rule is effective on May 27, 2008. The POC is Dr. David J. McKee, Health and Environmental Impacts Division, Office of Air Quality Planning and Standards, U.S. EPA, Mail Code C504-06, Research Triangle Park, NC 27711; telephone: 919-541-5288; fax: 919-541-0237; e-mail: mckee.dave@epa.gov. (Federal Register: March 27, 2008 [Rules and Regulations], Page 16435-16514).