Health Effects of Particulate Matter
Epidemiological research has established that particle pollution has a large impact on human health. An overview of mass, number, and lifetime of a typical city aerosol is given in Figure 6. For general background information on particles, see Aerosols; for details about emissions of particles, see Air pollution emissions.
The large number of very small particles is caused by high-temperature processes. Recently, transportation emissions have increased greatly. Otto (cars with ignition) and Diesel engines cause great emissions of very small particles with very little mass and short lifetimes, because they coagulate very quickly. Aerosol particles between 0.2 and 2 micron present a large fraction of the mass; they are present in smaller numbers than the small particles, but they have relatively long lifetimes. Large particles are very low in number, have large mass, and short lifetimes; they “fall” out of the atmosphere, a process called deposition.
The epidemiological research has not yet revealed, with certainty, which fraction of aerosol, PM-10 (mass of aerosol particles with a diameter < 10 ?m), PM-2.5 (mass of aerosol with a diameter < 2.5 ?m) or ultra-fine particles or specific compounds in aerosol particles are responsible for the observed health effects. Many indicators point in the direction of ultra-fine particles.
Health Effects of Particulate MatterEpidemiological research has established that particle pollution has a large impact on human health. An overview of mass, number, and lifetime of a typical city aerosol is given in Figure 6. For general background information on particles, see Aerosols; for details about emissions of particles, see Air pollution emissions.The large number of very small particles is caused by high-temperature processes. Recently, transportation emissions have increased greatly. Otto (cars with ignition) and Diesel engines cause great emissions of very small particles with very little mass and short lifetimes, because they coagulate very quickly. Aerosol particles between 0.2 and 2 micron present a large fraction of the mass; they are present in smaller numbers than the small particles, but they have relatively long lifetimes. Large particles are very low in number, have large mass, and short lifetimes; they “fall” out of the atmosphere, a process called deposition.The epidemiological research has not yet revealed, with certainty, which fraction of aerosol, PM-10 (mass of aerosol particles with a diameter < 10 ?m), PM-2.5 (mass of aerosol with a diameter < 2.5 ?m) or ultra-fine particles or specific compounds in aerosol particles are responsible for the observed health effects. Many indicators point in the direction of ultra-fine particles.
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