PM 2.5 Significance Thresholds and Calculation Methodology

California and the federal governments have established ambient air quality standards for fine particulate matter (PM) less than or equal to 2.5 microns in diameter (PM 2.5).  As a result, there was a need to establish a methodology for calculating PM 2.5 and appropriate PM 2.5 significance thresholds for the purpose of analyzing local and regional PM 2.5 air quality impacts in CEQA or NEPA air quality analyses.  A Working Group was established, which included representatives from various stakeholder groups (XLS, 19kb), to provide input in the development of PM 2.5 significance thresholds and calculation methodology. On October 6, 2006, the SCAQMD Governing Board unanimously adopted the following  methodology to calculate PM2.5 and PM2.5 significance thresholds.  As part of AQMD intergovernmental review (IGR) commenting responsibilities, AQMD staff began submitting comments relative to the PM2.5 proposal on CEQA documents beginning January 2007.

Final Documents


Past Meeting Information


Public Hearing for Governing Board to Consider Implementing Methodology to Calculate PM2.5 and PM2.5 Significance Thresholds - October 6, 2006

Governing Board Public Hearing Agenda Item #36


PM 2.5 Working Group Meeting #3 - August 22, 2006

Agenda (DOC, 908kb)

PM 2.5 Public Workshop - August 9, 2006

PM 2.5 Working Group Meeting #2 - July 11, 2006


Agenda (DOC, 907kb)

PM 2.5 Working Group Meeting #1 - June 8, 2006


Agenda (DOC, 906kb)

  • California Emission Inventory Data and Reporting System (CEIDARS) PM Profile (superseded by Appendix A in the above final document)



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