Area Designations for the Federal PM 2.5 Standard

This page last reviewed November 7, 2012

Background:


On December 18, 2006, the United States Environment Protection Agency (U.S. EPA) strengthened the 24-hour PM2.5 standard from 65 ug/m3 to 35 ug/m3.  Per Clean Air Act requirements, ARB transmitted our nonattainment area recommendations to the U.S. EPA on December 17, 2007.  These nonattainment area recommendations were based on 2004-2006 PM2.5 air quality monitoring data.   ARB transmitted additional analysis in support of our earlier recommendations on October 15, 2008.  U.S. EPA responded to our recommendations and posted these on their website.  

In late 2009, U.S. EPA issued a final Federal Register notice designating areas as "nonattainment" and "unclassifiable/attainment" for the 24-hour national air quality standards for fine particulate matter (PM2.5), with additional designations and clarifications following in 2011.  Further detailed information on the 2006 24-hour fine particulate (PM2.5) standard and the regulatory process can be found on the U.S. EPA website.

Recent Activities:


Below you will find links to meeting notices, staff reports, and transmitted documents, as well as the final Federal Register Notices issued by U.S. EPA.

2011 U.S. EPA Additional Air Quality Designations:


2009 U.S. EPA Final Designations:


2008 Additional Analysis to Support ARB Recommendations:


2008 U.S. EPA Response to ARB Recommendations:


2007 Transmittal to U.S. EPA:

On December 17, 2007, ARB submitted initial recommendations for area designations under the  Revised Federal PM2.5 Standard.

ARB Public Hearing -  December 6-7, 2007 

  • Hearing Notice - (PDF - 11 KB)
  • Staff Report (PDF - 89 KB)
  • Potential Exceptional Events (pdf - 2.8 MB): U.S. EPA guidance allows for the exclusion from regulatory determinations of air quality data affected by exceptional events. Since U.S. EPA will base their final nonattainment area designations on 2005-2007 PM2.5 air quality monitoring data, ARB must submit 2007 calendar year exceptional events documentation by December 18, 2007. The following document addresses monitoring days which may have been impacted by wildfires late in 2007 for areas in which the data may affect their designation status.


2004 Transmittal to U.S. EPA:

U.S. EPA finalized the below PM2.5 designations effective April 2005 based on 2002-2004 PM2.5 air quality monitoring data.  The South Coast Air Basin and the San Joaquin Valley Air Basin were designated nonattainment for both the 24 hour and annual PM2.5 standards.


Contact Information:

Comments and questions regarding this subject may be sent to:

Sylvia Vanderspek
Particulate Matter Analysis Section
Air Resources Board
P. O. Box 2815
Sacramento,  CA 95812
(916) 324-7163
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