PM10 NAAQS Implementation
The term "particulate matter" (PM) includes both solid particles and liquid droplets found in air. Many manmade and natural sources
emit PM directly or emit other pollutants that react in the atmosphere to form PM. These solid and liquid particles come in a wide
range of sizes.
Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system Particles less than 2.5 micrometers in diameter (PM2.5)are referred to as "fine"particles and are believed to post the largest health risks. Because of their small size, fine particles can lodge deeply into the lungs. Sources of fine particles include all types of combustion (motor vehicles, power plants, wood burning, etc.) and some industrial processes. Particles with diameters between 2.5 and 10 micrometers are referred to as "coarse." Sources of coarse particles include crushing or grinding operations, and dust from paved or unpaved roads.
In 1997, EPA established NAAQS for PM2.5 for the first time as well as revised NAAQS for PM10. Because the monitoring and implementation plans for these two pollutants are different, separate sets of webpages have been created for them. This page is a launch point for information on PM10.