Document R2jEjy9GMEwdM52wxgveBrKDn

sr~. - I a 160 FRANK A. FATTY ENTRY AND ACTION OF TOXIC MATERIALS 161 the alveolar air is the same as that in the room air, with due correction for tem Jjfepelling mucous and foreign material toward the oral cavity is of a high order, perature and humidity, With the more soluble vapors, alveolar air concentratior 1 ^^^fedividual cilium moves toward its goal with whiplike motion, then slowly at any point during accumulation, may be used to estimate the average room-ai " resufngs its former position. It is evident, then, that dust particles trapped any- concentration, given the length of exposure, the saturation curve for the particular, ^^K-uJiqre short of the alveolar ducts are subject to removal from the lungs through vapor, and its coefficient of distribution. An interesting variation, of much practice 'u \ action. Upon arrival at the oral cavity they are expectorated or swallowed. usefulness, is met in the case of radon: its concentration in the alveolar air ma; t\-i'itrticles (silica) reaching and remaining in the alveoli are believed to be be used as an indication of radium storage or deposition, providing sufficient tim has elapsed for relatively complete desaturation (8 hours or more after the end c an inhalation exposure). The physical laws governing the rate of gas exchange between the blood and the respired atmosphere are the basis of a proposed method18 for measuring pul ^^'.rtiigcly'hmited to the sizes ranging between 3 and 0.1 /a,16 3 being the largest to ^*^1 at the alveoli in significant quantities. The majority of particles below 0.1 'a! c^t bought to be too small to be trapped in the alveoli and are exhaled much as 18 an undissolved gas. The particles caught in the alveoli may be ab- through the alveolar wall, or they may be engulfed in phagocyte cells and monary functional capacity in terms of lung ventilation, gas transfer by diffusio MfAvrn;fir'flr'ried into the blood capillaries, or enter the lymphatics and be concentrated at across the alveolar wall, and pulmonary blood flow. The authors suggest Posm-'Mi| lllpheobronchial lymph nodes. Particles of silica 1 n and under are the most bilities of determining the nature and magnitude of respiratory impairment. "~r Sjfhnd dangerous, not only in their ability to remain suspended in the air, but D. DUSTS AND FUMES iffpiailly in their activity in tissue.16 I '. The Absorption oj Particulate Matter 8. Action oj Suspended Particulate Matter Dusts, fumes, and smokes represent solid participate matter differing quality, form, and particle size. The process of their accumulation, distributio^ and elimination is much more complicated than the same process with gasejp Brown14 showed that with a number of dusts having a particle size range of 0.25 f.n fin f., approximately 55 per cent of the inhaled dust was retained by men. Th| extremes of retention reported, however, ranged from 15 to 95 per cent. KetentiijjL was found to be inversely proportional to the rate of respiration and minute ve||r tilation for rates below 20 inhalations per minute, with no apparent change aboyg 20. Retention was directly proportional to the size of particles or their aggregatej| to density^ and to wettability. Of this retained dust, a part is retained in the has| filter and part by contact with wet surfaces in the respiratory passages, while sqm|[ reaches the respiratory tissues. The upper respiratory passages are subject to^bri periods of low velocity, or static air, between alternately directed flows of rath|n high velocity air. Because of sharp changes in direction, some dust, especially t|ej larger particles, 5 to 20 p in diameter, is impinged and arrested in these passajml hy contact, with moist, surfaces- In the alveoli the air must necessarily ,be statist moving slpiwly.-.diiring respiratory movements, so that ample. oppqrtjunity .issfM sented for settling and for contact with the moist alveolar walls. If particleEa|L caught before they .enter the alveoli, they are continually swept toward the mojiMf by the ciliated epithelium,8 which extends from the lower pharynx to the respi||| tory bronchioles.' These ciliated cells are abundant in the trachea, and even-iH|ge abundant in the large bronchioles, but are sparse in the respiratory bronchiole! and absent in the alveoli. The motions of the cilia are wavelike and their efficient "T. F. Hatch and K. M. Cook, AMA. Arch. Ind. Health, 11, 142 (1955). 14 C- E. Brown, J. Ind. Hyg. Toxicol., 13, 293 (1931). |teftoxic dusts may dissolve and enter the circulation by absorption from the Story tract, or they may be absorbed after being swallowed. The action of ttiscussed under the material involved. "Pneumoconiosis'-producing dusts egB) their effects after lodging in the alveoli. Other particulate matter may Upgic reactions or, in the case of disease germs, infections. The possibility f-ug.tion-of.gases-and.vapors-by.-par.ticulate.matter should, not be overlooked Me of significant exposure of the respiratory tract to these gases and gltnough they may not be present in significant concentrations in the gase|Jijmment. Also, it has been demonstrated that the normal locus of action Ssbluble gases may be transferred from the upper to the lower respiratory J&ugh sorption on particles, thereby increasing their physiological effect. |||||;, when gases less soluble in water, such as nitrogen oxides, phosgene, onerare mixed with aerosols, their effects may be lessened because of sorp- complete discussion of the role of dusts and the evaluation of disatherefrom see Chapter XII. E. MISTS - inhaled to reach all parts of the lungs and from there may be slightly volatile material, concentrations far above, those possible Pressures ^e gaseous phase at room temperature may be encounJppy(fat reason a solvent, the vapors of which may be considered harmless fcfJj.V. ffaryTcmperatures, can be very dangerous as a mist. .Gardner, Ind. Med., 9, 45 (1940). raSpjlfjrei&ms, R. Z. Schulz, and P. Drinker, J. Ind. Hyg. Toxicol., 27, 199 (1945). MSM.T'aBene, J. E. Long, and E. E. Christofano, AMA. Arch. Ind. Health, 11, .297 'iki\ illli