Fine Particulate Matter
Particle pollution, or particulate matter, consists of particles that are in the air, including dust, dirt, soot and smoke, and little drops of liquid. Some particles, such as soot or smoke, are large or dark enough to be seen. Other particles are so small that you cannot see them.
Particles that are 2.5 micrometers in diameter or smaller; are known as Fine Particulate Matter or PM2.5. Air quality measures for PM2.5 are based on the National Quality Standards ().
View the measures and access data charts, tables, and maps