PARTICULATE MATTER

What is 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 an electron microscope.
• Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM.

Size of PM

• These solid and liquid particles come in a wide range of sizes.
• Particles less than 10 micrometers in diameter ( PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system.
• Particles less than 2.5 micrometers in diameter (PM 2.5) are referred to as "fine" particles and are believed to pose the greatest health risks.
• Particles with diameters between 2.5 and 10 micrometers are referred to as "coarse".
• Because of their small size (approximately 1/30th the average width of human hair),fine particles can lodge deeply into the lungs.

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 including 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.

Implications

According to a study , increase in PM 2.5 by one microgram per cubic metre reduces life expectancy by three weeks , which implies that such alarming increases could chop off a significant portion of one's healthy years.