Area Designations for the Federal PM2.5 Standards

This page last reviewed February 12, 2014


Background:


There are two Federal standards for PM2.5 (fine particulate matter) - an annual average standard of 12.0 ug/m3 and a 24-hour average standard of 35 ug/m3.  Detailed information regarding the Federal particulate matter (PM) standards can be found on the U.S. EPA website.

Recent Activities:


Annual Standard.  On December 14, 2012, U.S. EPA lowered the federal primary PM2.5 annual standard from 15.0 micrograms per cubic meter to 12.0 micrograms per cubic meter.  U.S. EPA made no changes to the primary 24-hour PM2.5 standard or to the seconday PM2.5 standards.  Per Clean Air Act requirements, ARB will transmit nonattainment area recommendation by December 14, 2013.  These nonattainment area recommentations are based on 2010-2012 air quality monitoring data.  U.S. EPA is scheduled to make final designations by December 14, 2014.  These final designations will be based on 2011-2013 air quality monitoring data

24-Hour Standard.  On December 18, 2006, 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.


Documentation / Previous Activities:


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

2013 Transmittal to U.S. EPA for Revised Federal PM2.5 Annual Standard:

On November 25, 2013, ARB submitted initial recommendations for area designations under the Revised Federal PM2.5 Annual Standard.

ARB Public Hearing -  November 21, 2013 


2011 U.S. EPA Additional Air Quality Designations for Revised 24-Hour Standard:


2009 U.S. EPA Final Designations for Revised 24-Hour Standard:


2008 Additional Analysis to Support ARB Recommendations for Revised 24-Hour Standard:


2008 U.S. EPA Response to ARB Recommendations for Revised 24-Hour Standard:


2007 Transmittal to U.S. EPA for Revised Federal PM2.5 24-Hour Standard:

On December 17, 2007, ARB submitted initial recommendations for area designations under the Revised Federal PM2.5 24-Hour 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.



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