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EPA/AR RIN: 2060-AO11 Publication ID: Fall 2008 
Title: Air Quality Index Reporting and Significant Harm Level for PM2.5 
Abstract: On July 23, 1999, EPA adopted revisions to the uniform air quality index used by States for daily air quality reporting to the general public in accordance with section 319 of the Clean Air Act (Act). These changes included the addition of the following elements: A new category described as “unhealthy for sensitive groups”; two new requirements 1) to report a pollutant-specific sensitive group statement when the index is above 100, 2) to use specific colors if the index is reported in a color format; new breakpoints for the ozone (O3) sub-index in terms of 8-hour average O3 concentrations; a new sub-index for fine particulate matter (PM2.5); and conforming changes to the sub-indices for coarse particulate matter (PM10), carbon monoxide (CO), and sulfur dioxide (SO2). In addition, EPA changed the name of the index from the Pollutant Standards Index to the Air Quality Index (AQI). The revisions enhance the communication of pollutant-specific health effects information to members of sensitive groups, including precautionary actions that can be taken by individuals to reduce exposures of concern. The revisions also enhance the usefulness of the AQI with regard to other programs that provide air quality information and related health information to the general public, including State and local real-time air quality data mapping and community action programs. In 2006, EPA promulgated a revised national ambient air quality standard (NAAQS) for PM2.5 levels of 35 ug/m3, 24-hour average. The purpose of this rulemaking is to make revisions to the AQI sub-index for PM2.5 to be consistent with the new daily standard. It is important to make this revision expeditiously to allow members of the public, especially members of sensitive groups, to take exposure reduction measures when PM2.5 levels are forecasted to be high. State and local air agencies are encouraging EPA to make the revisions as soon as possible. EPA has never set a Significant Harm Level (SHL) for PM2.5. There are SHLs for sulfur dioxide, ozone, carbon monoxide, PM10 and nitrogen dioxide. Designated areas must have contingency plans in place to prevent ever reaching this level. There is not currently an SHL for PM2.5. The SHL is typically the same concentration as the 500 level of the AQI. So along with revising the AQI for PM2.5, we will also set an SHL for PM2.5. 
Agency: Environmental Protection Agency(EPA)  Priority: Substantive, Nonsignificant 
RIN Status: Previously published in the Unified Agenda Agenda Stage of Rulemaking: Proposed Rule Stage 
Major: No  Unfunded Mandates: No 
CFR Citation: 40 CFR 58.50    40 CFR 58 app G    40 CFR 51.150 subpart H   
Legal Authority: 42 USC 7401 et seq   
Legal Deadline:  None
Timetable:
Action Date FR Cite
NPRM  11/00/2008    
Final Action  04/00/2009    
Additional Information: SAN No. 5115; EPA Docket information: EPA-HQ-OAR-2007-0195
Regulatory Flexibility Analysis Required: No  Government Levels Affected: Federal, Local, State, Tribal 
Small Entities Affected: No  Federalism: No 
Included in the Regulatory Plan: No 
RIN Data Printed in the FR: No 
Agency Contact:
Susan Stone
Environmental Protection Agency
Air and Radiation
C504-06,
Research Triangle Park, NC 27711
Phone:919 541-1146
Fax:919 541-0237
Email: stone.susan@epa.gov

Phil Lorang
Environmental Protection Agency
Air and Radiation
C304-04,
Research Triangle Park, NC 27711
Phone:919 541-5463
Email: lorang.phil@epa.gov