Particulate Matter National Ambient Air Quality Standard

Last modified Wednesday, July 09, 2008 11:16

Particulate matter (PM) is a term for particles and liquid droplets suspended in the air.  Particulate matter originates from a variety of sources, including diesel trucks, power plants, wood stoves and industrial processes. The chemical and physical compositions of these various particles vary widely.  Health risks include premature death from heart and lung disease, aggravation of heart and lung diseases, and respiratory and cardiovascular effects. 

Historically, particulate matter pollution was measured under a coarse particulate matter standard, PM10 (particles with diameters equal to or less than 10 µm).  However, the standard was revoked in 2006 and replaced with a standard for fine particulate matter, PM2.5 (particles with diameters equal to or less than 2.5 µm).  This standard further protects human health.  The fine particulate standard is met when the three-year average of annual concentrations does not exceed 15 µg/m3 and the three-year average of the daily PM2.5 concentrations at each monitor does not exceed 35 µg/m3.

Unlike the ozone standard, there is no classification system for fine particulate matter; an area either meets the standard (attainment) or exceeds the standard (non-attainment).  The US EPA has designated the 20-county metro Atlanta as a nonattainment area for fine particular matter, effective April 5, 2005.  For more information on particulate matter reference "An Introduction to Particulate Matter for Transportation Officials." (PDF).