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Classification of particles based on size |
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| Particle |
Aerodynamic diameter (μm) |
Sources |
Mode of generation |
Atmospheric half-life |
|
|
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| Thoracic particles(PM10) |
< 10 |
- |
- |
- |
|
|
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| Coarse particles(PM2.5-10) |
2.5 - 10 |
Suspension from disturbed soil (farming, mining, unpaved roads), construction, plant and animal fragments |
Mechanical disruption (crushing, grinding, abrasion of surfaces), evaporation of sprays, suspension of dusts. |
Minutes to hours |
|
|
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| Fine particles (PM2.5) |
< 2.5 |
Power plants, oil refineries, wildfires, residential fuel combustion, tailpipe and brake emissions |
Gas-to-particle conversion by condensation, coagulation (accumulation mode) |
Days to weeks |
|
|
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| Ultrafine particles (UFP) |
< 0.1* |
Fuel combustion (diesel, gasoline) and tailpipe emissions from mobile sources (motor vehicles, aircrafts, ships) |
Fresh emissions, secondary photochemical reactions (nucleation mode) |
Minutes to hours |
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PM10 includes all other PM fractions. * While the UFP size cutoff is by definition considered < 0.1 μm, UFP can include particles up to 0.2 μm in experimental studies using particle concentrators, because the distinction between the ultrafine and the accumulation modes can vary from 0.1 to 0.2 μm depending upon location and season for reasons that include among others, variability in the size of particulate derived from "fresh" emission sources and deviation from a spherical shape [101]. Table based on U.S. EPA [8]. | ||||
Araujo and Nel Particle and Fibre Toxicology 2009 6:24 doi:10.1186/1743-8977-6-24 |
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