What is Particulate matter?
Particulate matter is the term used for tiny particles found in the air, which includes dust, soot, dirt, smoke, and liquid droplets. These Particles can be suspended in the air for long periods. Some of these particles are large or dark enough to be seen as soot or smoke. While some are so small that individually, they can only be detected with an electron microscope.
Some of these particles are directly emitted into the air (primary particulate matter). They come from different sources such as cars, trucks, buses, factories, tilled fields, construction sites, stone crushing, unpaved roads, and burning of wood.
Other particles (secondary particles) may be formed in the air through a photochemical reaction. They are indirectly formed when gases from combustion processes react with sunlight and water vapour, and sometimes, hydroxyl radical. These can result from the combustion of fuel in motor vehicles, at power plants, and in other industrial processes.
According to the EPA, the size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometres in diameters pose the most significant issues because they can get deep into the lungs, and some can even penetrate into the bloodstream. Exposure to such particles can affect both the lungs and the heart.
Small particles of great concern include “fine particles” (such as those present in smoke and haze), which are about 2.5 micrometres in diameter; and “coarse particles” (found in wind-blown dust), which have diameters between 2.5 and 10 micrometres.