PARTICULATE MATTER 2.5

Subject : Environment

Concept :

Particulate matter

Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.
Particles can be suspended in the air for long periods of time.
Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with a microscope.
Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM.

PM 2.5

Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as “fine” particles and are believed to pose the greatest health risks.
Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.
Particles with diameters between 2.5 and 10 micrometers are referred to as “coarse” particles.
PM 2.5 particles can only be detected with the help of electron microscope.

Sources of PM

Sources of fine particles include all types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes.
Sources of coarse particles include crushing or grinding operations, and dust from paved or unpaved roads.
Other particles may be formed in the air from the chemical change of gases. They are indirectly formed when gases from burning fuels react with sunlight and water vapor. These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.