Graphical interpretation?of air quality standards, PM10 and PM2.5. [U.S.EPA]

Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.

Those less than 10 micrometers in diameter is called PM10.?They?are so small that they can get into the lungs, potentially causing serious health problems. Ten micrometers is smaller than the width of a single human hair.

The PM2.5, much stricter than the PM10, applies to fine particles 2.5 microns or less in diameter that are believed to pose greater health risks than larger particles. Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.

These particles generally come from activities that burn fossil fuels, such as traffic, smelting, and metal processing.