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<br />BIGl
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<br />Division: Air Pollution Control Division
<br />James M. Lents, Director
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<br />B. PARTICULATE EXPOSURE
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<br />Particulate matter represents a broad class of cheaically and physically diverse substances. Their prlncipai cODllDOn feature is e::dstence in
<br />the liquid or solid phase as discrete particles ranging In size fro. molecular- clusters of 0.005 aicroaeters (um) to coarse particles ou the
<br />order of 100 um in diameter. the major chelllic:al and physical properties of particulate aatter vary greatly with time, region, meteorology and
<br />source category. For the purpose of assessing health and welfare, particulate matter is dividend into three categories.
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<br />'I11e range of most concern is from 0-10 um. Particles in the sIze range 0-2.Sum are referred to as- -respirable- particles, indicating that they
<br />are taken Into the deepest region of the lung. 'Ibose particles in the sIze range 2.5-15 um are called "lDhalable-, meaning that they are taken
<br />into the respiratory tract but not -as deeply as respirable particles. Host of the rell8.1ning particles, in the range 15-100 Ula, are fUtered
<br />out by the nose or cillia.
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<br />Pollutants of concern fro. diesel engInes include nitrates, sulfa,tes and carbonaceous particles. Diesel part.iculates are in the respirable
<br />size range and contain known and suspected carcinogenic substances. Diesel particulates have also been shown to be a -sIgnificant contributor
<br />to Denver's vIsibility pra:blem.. and are al.so more.damaging,w1th respect 'to,urhan Boiling than, typIcal airborne par'tlculates.
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<br />Windblown crustal. Pl8teria1s and road dust propelled by moving vehicles, sulfates formed froll sulfur oxides, -residential voo!! combustion.
<br />products of oil and coal combustion, and industrial ellllIssions contribute most of the particulate utter in urban areas. Fme partl--cles are
<br />usually produced by industrial emissions, combustion processes, or atlllOspheric transforiDatlon of gases to particles; llechanical processes
<br />provide most of the coarse particles.
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<br />Fine particles generally constst of water, alllDlonium sulfate, sulfuric acid, carbonaceous material, a variety- of condensed organics, lead.
<br />nitrates and a small amount of trace elements. Coarse particles are more variable aud depend 1Il.o-re upon the part.icula-r geog1:aphy and induat.rlea
<br />in an area. Quartz, clays, limestone, asbestos, rubber tIre particles, organics, nitrates and road salt make up the bulk. of the coarse
<br />particles.
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<br />Host particles that are deposited in the nasa-pharynx region are coarse. High levels of such particles aay cause dryness of the throat. but
<br />have no effect on IDucocilliary clearance. These particles are norll81ly cleared froa the regloJl in a matter of ainutes. Both fine and coarse
<br />particles are deposited in the tracheobronch1al region. They can cause --constriction of the bronchia, reduced mucocl11iary clearance, ana
<br />aggravation of chronic respiratory diseases such as asthma, bronchItis, emphYse8la, and poss1bl'y cancer.
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<br />Fine and coarse particles up to 10 UIP: can be absorbed by the alveolar region of the lung. Deposition. in this area can be of special concern
<br />because the body may take weeks or years to remove these particles. 'lhey can affect the lung in several ways. '!bey may aggravate chronic luna:
<br />disease by disturbing normal ventilation and causing a reflex constriction of blood vessels that suPPlY part of the lung. They may also cause
<br />inflamation, fibrosis, and other conditions of the lung.
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<br />Parliculate mat-ter may have chemicals adsorbed on them whicb can cause eye and skin irritatIon. There can be damage to plants, buildings, and
<br />cars from cllemical, sandblasting and deposition effects. Particulate matter is also a primary cause of visibility reduction.
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<br />(1 um = 1/1,000,000 meter)
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