Area Designations for the Federal PM2.5 Standards

This page last reviewed December 20, 2018


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.

Latest Activities:


Annual Standard.   In December 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.  Area designations became effective on April 15, 2015 (Federal Register Notice published January 15, 2015).  Current area designation information can be found on U.S. EPA's website

24-Hour Standard.  In December 2006, U.S. EPA lowered the federal 24-hour PM2.5 standard from 65 ug/m3 to 35 ug/m3.  Area designations became effective on December 14, 2009 (Federal Register Notice published November 13, 2009).  Current area designation information can be found on U.S. EPA's 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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