PM2.5

Pm2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5

micrometers,which is about 3% the diameter of a human hair.

Commonly written as PM2.5, Particles in this category are so small that they can only be detected with

an electron microscope.They are even smaller then their counterparts PM10,which are particles that are

10 micrometres or less,and are also called fine particles.

Fine particals can come from various sources.They include power plants,motor

vehicles,airplanes,residential wood burning,forest fires,agricultural burning,volcanic eruptions and dust

storms.

Some are emitted directly into the air,while others are formed when gases and particles interact with one

another in the atmosphere.