Particulate Matter (PM)

Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols. The physical characteristics of particles, and how they combine with other particles, are part of the feedback mechanisms of the atmosphere. See aerosol, sulfate aerosols.

Solid particles or liquid droplets suspended or carried in the air (e.g., soot, dust, fumes, mist). See aerosol, sulfate aerosols.