Airborne particulate matters (PMs) consist of a mixture of solids or liquids suspended in the air. PMs are conveniently classified based on their aerodynamic diameter sizes, ranging from nanometers to 100µm. Thoracic particles (PM10) are those with aerodynamic diameters less than 10µm, with similarities applicable to coarse particles (PM2.5–10), fine particles (PM2.5), and ultrafine particles (PM0.1). Although the ultrafine particles are smaller and weigh less, their numbers are much larger than those of the rest. Generally speaking, coarse particles constitute about 90 percent of suspended particles, while fine and ultrafine make up 1 to 8 percent of the total mass. Large particles come from such things as stirring up road dust, agricultural processes, mining operations, sea spray along coastlines, plant pollen, and insect parts. Ultrafine ...

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