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fc: V" ST0853523 INDUSTRIAL DUST Hygienic Significance, Measurement, and Control PHILIP DRINKER, S.B., Ch.E. Professor of Industrial Hygiene, Harvard School of Public Health THEODORE HATCH, B.S., S.M. Professor of Industrial Health Engineering, Graduate School of Public Health, University of Pittsburgh and Research Adviser, Industrial Hygiene Foundation, Mellon Institute PLAINTIFF'S EXHIBIT SA-572 Second Edition McGRAW-HILL BOOK COMPANY, INC. 1954 New York London Toronto ST085352U INDUSTRIAL DUST Copyright, 1936, 1954, by the McGraw-Hill Boole Company, Inc. Printed in the United States of America. All rights reserved. This book, or parts thereof, may not be reproduced in any form without permission of the publishers. Lib?/ of Congiess Catalog Card Number: 54-6719 II THE MAPLE PBE88 COMPANY, YORK, PA. ST 0853525 PREFACE Control of the dust hazard in industry is the joint duty of the physician and the engineer. In the preparation of this book we have emphasized the cooperative nature of the problem and have devoted considerable space to such of the medical aspects as may help the engineer to understand the manner in which hygienic requirements affect engineering design and operation of dustcontrol equipment. So far as possible, only the basic principles are considered. The book is written from the engineer's standpoint but we hope it will be of some value to physicians who wish to understand more fully the engineering aspects of the problem. Design of dust control apparatus is an engineering matter, but it is often the physician who finally appraises the success of the control system. Unfortunately, current practice in the field of industrial hygiene permits the indiscriminate mixing of British and metric units. Thus, fans are rated in cubic feet a minute but dust particles are measured in microns. We do not support these inconsistencies but have merely followed the usual nomenclature and practice in this book. Many friends and colleagues in this country and abroad have helped us with this second edition. At our request some of them read critically various parts of the manuscript and others sup plied technical material. We extend to them our sincere thanks for their help. Philip Drinker Theodore Hatch ST0853526 CONTENTS PREFACE CHAPTER 1 PHYSICAL PROPERTIES OF DUST, FUMES, AND MISTS 1 Definitions. General Properties. Particle Dynamics. Resist ance. Terminal Settling Velocity. Acceleration. Dynamic Projection. Brownian Motion. Centrifugal Force. Impinge ment. Electrical Field. Thermal Precipitation. Flocculation. Effect of Air Motion and Humidification. Optical Properties. CHAPTER 2 I EFFECTS OF DUSTS AND FUMES UPON MA.N 31 Respiration and Dust Inhalation. Pneumoconiosis. Silicosis. Mortality and Morbidity. Employability of Workmen with Silicosis. Asbestosis. Prevention of Silicosis. Other Pneumo conioses. CHAPTER 3 INERT AND TOXIC DUSTS Carbonates. Gypsum. Iron. Benign Pneumoconioses. Toxic Dusts. Lead. Radioactive Dusts. Manganese. Chromates. Cadmium. Arsenic. Selenium and Tellurium. Insecticides. Vanadium. Fluorides. Metal-fume Fever. Allergic Reactions. Industrial Dusts. 56 chapter 4 PHYSICAL AND CHEMICAL FACTORS IN PNEUMOCONIOSIS Silica. Hardness. Solubility. Particle Size. Chemical Com position of Dusts. Disintegration and Settlement. 76 ST0853527 viii . CONTENTS CHAPTER 5 DUST RETENTION BY MAN Review. Nasal Filtration. Retention of Dusts--of Gases. Alveolar Deposition. Upper Respiratory Retention. Effect of Particle Size. 89 chapter 6 THE DUSTY TRADES Dust Concentrations. Explosive Concentrations. Coal. Food. Metal Powders. Lung Analyses. Permissible Dustiness. Quartz. Coal. Cement and Limestone. Manganese. Lead. Metal Fumes. Cadmium. Arsenic. Fluorides. 96 chapter 7 APPRAISAL OF DUSTINESS 113 Hygienic Survey. Frequency of Sampling. Weighting Dust Exposures. Sampling Rate and Volume. Required Accuracy. Engineering Survey. Unit of Concentration. chapter 8 DETERMINATION OF DUST CONCENTRATION Settlement. Filtration. Impingement. 123 chapter 9 DETERMINATION OF DUST CONCENTRATION 0Continued) Impinger. Electrical Precipitator. Thermal Precipitator. Comparison of Instruments. 147 chapter 10 DETERMINATION OF PARTICLE SIZE 106 Collection of Sample--in Pipe Lines--in Still Air. Measure ment. Screen Analysis. Roller Air Analyzer. Microscopic Measurement. Mounting. Selenium Coating. Linear Meas urement. Particle Diameter. Cascade Impactor. Elutriation. Electron Microscopy. Indirect Measurement. Surface Area. Graphical and Mathematical Representation. Curve Fitting. Average Diameter. Irregular Particles. ST 0853528 CONTENTS lx ' CHAPTER II CHEMICAL AND MINERALOGICAL ANALYSIS OP DUST 200 Collection of Sample. Sixe Separation. Determination of Free and Combined Silica. Petrographic Analysis of Fine Dust. Immersion Method. X-ray Diffraction. Differential Fusion. Staining. chapter 12 METHODS FOR THE CONTROL OF INDUSTRIAL DUST 213 Medical Control. Environmental Control--at Source--by Sub stitution--by Wetting--by Enclosure and Ventilation. Air Displacement in Handling Solids--in Hot Ojrarations--by Process Equipment. Plant Layout and Operation. House keeping. , chapter 13 DESIGN OF LOCAL EXHAUST SYSTEMS 230 Exhaust-ventilation Requirements. Dust-dispersion Force. Air Flow Induced by Falling Objects. Convection over Hot Proc esses. Enclosed Hot Processes. Measuring Air Displacement. Capture Velocities. Aerodynamics of Exhaust Hoods. Velocity Contours. Flanged Hoods. Center-line Velocities. Unob structed Hoods. Effective Distance. Exhaust Hood Design. Required Ventilation. Experimental Determination. Toxicity Requirement. Exhaust Piping. Layout. Adjustable Resist ance. Transporting Velocities. Pressure Losses. Low->velocity Systems. Source of Suction. Fan. chatter 14 AIR CLEANING 273 Definitions. Test Suspensions. Discharge Stacks. Choice of Equipment. Dust Loading. Material Collected. Cleaning Efficiency. Methods. Costs. Gravitational Settling Cham bers. Inertial Separators. Cyclones. chapter 15 AIR CLEANING BY FILTERING 295 Loadings. Velocities. Theory of Filtration. Impingement. Diffusion. Efficiency vs. Particle Size, Filter Depth, Air Veloc ity, Filter Resistance, Loading. Filter Cloths. Temperature Control. Filtering Velocity. Life and Upkeep. Recirculation. Performance Data. Air-conditioning Filters. High-efficiency Filters. Performance Data. Bacterial Filters. S T 0853529 CHAPTER 16 SCRUBBING ANDELECTRICALPRECIPITATION Performance Data. Equipment. Operation. 321 chapter 17 DUST-RESPIRATORS AND AIRMASKS 333 Definitions. Development. Bureau of Mines Approvals. Ve locity and Resistance. Leakage. Valves. Efficiency. Com pressed Air for Air Masks. Cost and Upkeep. BIBLIOGRAPHY AUTHOR INDEX SUBJECT INDEX 347 373 389 ST0853530 ' CHAPTER 1 PHYSICAL PROPERTIES OF. DUSTS, FUMES, AND. MISTS Suspensions of finely divided particles in air in the form of fogs and mists are common natural phenomena. Not so well-known, because it is generally not visible, is the dispersed system of atmospheric dust that extends over the face of the earth. It is only during unusual climatic conditions, such as those of 1935 in the Middle West, when atmospheric dust concentrations reached staggering levels (Fig. 1), or in the more recent Donora, Pa., Fio. 1. Kansas dust storm, April, 1935. (Courtesy Boyce.) incident (371), that the public becomes concerned with this phenomenon in a practical way. Within certain industries, on the other hand, contamination of the atmosphere with dust has long presented a problem, if not as a health hazard, then as a costly damaging agent against plant machinery or products. Even without producing measurable damage, dust constitutes a nuisance and creates poor working conditions. In recognition of the hazards and cost of such contamination, 1 Numbers in parentheses refer to corresponding items in the Biblio graphy on pp. 347-371. 1 ST085353I' 2 INDUSTRIAL DUST the high levels of pollution of an earlier day have been largely reduced in the dusty trades. But the potential hazards remain, and the control of industrial dust continues .is a never-ending battle. Beginning with empirical but common-sense measures, the dust-control program has now the benefit of considerable insight into the nature of dust hazards and is aided by quantita tive methods for the measurement and evaluation of dust expo sures. An understanding of the physical behavior of dust provides an increasingly sound engineering basis for the design of dust-control measures. Some of the physical properties of dusts, fumes, and mists, which are important in a consideration of hazards, in the sampling and analysis of such materials, and in their control, are discussed in the present chapter. The subject is a large one and, in its theoretical aspects, has engaged the attention of physicists and chemists for many years. The application of the theoretical and experimental findings to the solution of practical problems, such as the subject of this volume, however, is relatively new. An outstanding contribution of a quarter century ago which brought together much scattered material was Clouds and Smokes, by W. E. Gibbs (183), now unfortunately out of print. This was followed in 1932 by Smoke, A Study of Aerial Disperse Systems, by Whytlaw-Gray and Patterson (442), and in 1943 DaliaValle's Micromeritics (93) appeared. During World War II, as in World War I, extensive research added enormously to our under standing of the physical properties of finely divided matter in air, with direct and useful application to the study of industrial-dust problems. Much of this work has found its way into technical handbooks (245, 335). We shall have occasion to refer many times to these and other sources of basic information and shall be satisfied, here, to discuss the physical properties of dusts, fumes, and mists in only the briefest outline form. Definitions. To all the various disperse systems in air, such as dust, fog, clouds, mist, fumes, and smoke, Gibbs (183) gave the general name aerosol, which is analogous to the accepted term hydrosol denoting disperse systems in water. Dust is formed by reducing earthy materials to small size. Processes like grinding, crushing, blasting, and drilling produce dust particles of sizes from the submicroscopic to the visible, their composition being the same as that of the parent material. ST0853532 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 3 Common examples are the mineral dusts derived from the dis integration of rock and the organic dusts like wheat and flour. Fumes are formed by processes such as combustion, sublima tion, and condensation. Typical examples are the fumes from burning lead or the zinc oxide produced from zinc vapor. Par ticle size is generally below 1 n. In contrast to dusts, fume particles often flocculate vigorously.1 Smoke "presupposes a certain degree of optical density" (442). Generally it is of organic origin, but it may include systems con sisting "of particles of low vapor pressure which settle slowly under gravity." We shall use the word with reference particu larly to systems that are organic in origin, such as the smoke from burning tobacco, wood, oil,-or coal. In general, smokes are characterized by a particle size below 0.5 n. Mists or fogs are formed by the condensation of water vapor upon suitable nuclei or by the atomization of liquids. Particle or droplet size varies widely depending on the conditions prevailing. General Properties of Dusts, Fumes, and Mists. Disperse systems of dusts or other finely divided matter in air occupy a position with respect to size properties between the colloidal and the macroscopic regions. The particles are larger than those in colloidal systems; yet they are small enough to exhibit some of the properties of colloids and also to have properties not possessed by large masses of the substances from which they are generated. When a solid or liquid is broken up into finely divided particles and is dispersed in the air, two important changes take place: (1) the surface area is greatly increased, and (2) the space occupied by the dispersed material is expanded many times over the volume of the original mass. Thus, if 1 cc of quartz is crushed into particles of 1 cu m in size, there will be 1012 particles with a total surface area of 6 sq m as compared with G sq cm for the original block. Assuming a dust concentration of 100 million particles per cubic foot of air, the 1 cc of material will be dispersed in an air volume of 10,000 cu ft. The effect of these changes is to intensify, the chemical and physical activity of the material. The rate of oxidation is increased so much that substances like soft coal and aluminum 1 It is usual to speak of acid fumes as denoting a mixture of gas and mist. Throughout this book, however, we shall use the word to designate only solid particles. ST0853533 4 INDUSTRIAL DUST powder bum in air with explosive violence. Rates of evapora tion and solubility are also increased, and the phenomena of adsorption and electrostatic activity are intensified. The adsorp tion of a gas film on the particle surface may accelerate or retard chemical reactions, and it also interferes with physical phenomena such as wetting. Since the physiological effect of dust particles always is intimately associated with their physical and chemical activity, small particles generally are of more physiological importance than large ones. Similarity between Dusts and Liquids. Owing to the large amount of air adsorbed upon the surfaces of fine dust particles, a mass of such particles assumes some of the properties of liquids and gases. The mass can be compressed, and it splashes like a liquid when being carried in a pail. It can be poured through a pipe, and ripples are formed when a stone is dropped into a tank of dust. Dust can be "distilled" by passing air through it; the amount carried over varies with the air velocity. A fixed rate of air flow will "evaporate" a constant amount, and the air will become "saturated." When the air speed reaches a certain critical value, the whole body of dust will be carried over, i.e., the dust "boils." In these examples air velocity corresponds to temperature (293). PARTICLE DYNAMICS Like any other body, a microscopic particle is attracted toward the earth, but because of its relatively great surface area per unit of mass and the consequent high air resistance, an air-bome particle does not fall with increasing velocity according to the ordinary law of gravity. Almost immediately after it starts to fall, the air resistance imposed upon the particle balances the gravitational force, thus preventing further gain in speed. The particle then settles at its constant terminal velocity, which for microscopic particles is low, being measured in centimeters and even millimeters per hour. As a consequence, dust suspensions in air have considerable stability and may persist for long periods. Because of the great air resistance it is difficult to project micro scopic particles through air and equally difficult to remove them from the air. In a sense, the finest particles become a part of the air itself. The dynamic properties of microscopic particles are thus of the ST0853534 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 5 greatest importance in a consideration of dust hazards and their control. The characteristics of dust dispersion into the air, the spread of dust away from its source of generation or release, the control of dusty processes, and the problems of air cleaning are all intimately related to the dynamic behavior of air-borne dust. Physiologically, these properties are also of major concern for they largely determine the depth of penetration and degree of retention of inhaled dust in the respiratory tract and, hence, limit the lung-dosage rate in relation to air concentration and with it the dust hazard. General Law of Resistance. Resistance to the travel of a particle through air varies with the size and shape of the particle, with its velocity, and with the fluidity of the air. These factors are combined in the following general equation: CpAu1 CR where (R = resistance C = coefficient of resistance A = projected area of particle u = particle- velocity relative to air p = air density The drag coefficient C is not constant for all conditions of motion but varies systematically with the dimensionless Reynolds number Re = udp/p, p being the viscosity of the air and d the particle diameter. C also varies with the shape of the particle, the effect being different for different values of Re. The relationship C = /(Re), further simplified from the curves of Lapple and Sheppard (275), is shown for spheres in Fig. 2 for a range of Re from 10-< to > 106. The relationship has been divided into three zones according to the nature of dependence of C upon Re. For high values of Re (>103), C is reasonably constant and for spheres has an average value of 0.44. This is the zone of turbulent motion where the viscosity of the air has no effect. For this region, resistance varies with the squares of particle diameter and velocity (Newton) thus: (R = kpd^v? For spheres, k = 0.44 X x/8. When Re < 3.0, however, C varies inversely with Re: ST0853535 6 INDUSTRIAL DUST and (R = kpdu For spheres, k = 3r. Here, resistance varies directly with partide diameter and velocity and with viscosity of the air but is independent of air density. It is the zone of streamline motion for which Stokes developed the foregoing equation. XI o I01 tx \\ Fio. 2. Drag coefficient for spheres vs. Reynolds number. (Adapted from Lapple and Sheppard.) In the intermediate zone, the C vs. Re relationship is a complex one, involving both p and p as well as exponential values of d and u. The function has not been described mathematically except in an empirical way (5). An extensive treatment of particle dynamics is given by Lapple and Sheppard (275) in which the zone of intermediate motion is considered more precisely. Approximate relationships, however, with rounded exponents, are * and (R = 5.5pV"^ ST0853536 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 7 Terminal Settling Velocities. When a free-falling particle has attained its terminal velocity, the air resistance is just balanced by gravitational attraction. Consequently, for spheres, (ft = F, = ^ d*(<r -- p)g where a is the density of the particle and g the gravitational constant. For spherical particles, the terminal velocities in the three zones of motion are derived by equating resistance (ft to the particle weight, as above (neglecting the unimportant buoyancy of air): I. Streamline motion: ut = 9-$18/i II. Intermediate motion: ut -- - (pm) III. Turbulent motion: ut -- Simplifying these equations for spherical particles falling in air at ordinary temperature, p = 1.2 X 10~}, p = 1.8 X 10-<, we get, for velocity in centimeters per second and size expressed in microns, I. Streamline motion: ut = 0.003<rdm2 II. Intermediate motion: (dm < ' ut = 0.34 III. Turbulent motion: The graph in Fig. 3 is for crushed-quartz particles which, owing to their irregular shapes, fall with lower velocities than do spheres of the same diameter. The settling velocities and certain other size properties of microscopic particles are further summarized in the chart (after W. G. Frank) in Fig. 4. For irregular mineral particles obeying Stokes' law it is convenient to recall this rough rule: the terminal velocity for a 10-/x particle is about 1 fpm ST0853537 8 INDUSTRIAL DUST (H cm/sec) and for other sizes is given by the ratio Ffpm = dm* where dm is in microns. Zone Limits. The turbulent zone extends down to Re => 10* which, for spheres of unit density, corresponds to a lower limiting size of about 2 mm; this also applies roughly to irregular mineral particles settling in air. Fio. 3. Terminal velocity for quartz particles in air. (Adapted from Martin.) The upper limit for the zone of streamline motion is defined by Re = 3.0, giving d for spheres of unit density a limiting value of 115 n; for irregular mineral particles the upper limit is about 85 n. Thus, the intermediate zone for mineral particles falls between the approximate limits 85 to 2000 jt. The zone of Stokes' law also possesses a lower limit, for when the particles become small compared with the mean free path of the gas molecules, it is evident that resistance will decrease and, consequently,,the terminal velocity increases over the calcu lated value from Stokes' equation. A suitable correction was developed by Cunningham, see Gibbs (183), thus: ST 0853538 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 9 LAWS OF SETTLING IN RELATION TO PARTICLE SIZE <UNU or KWUHCATIOM AfPROX.) PARTICLES FALL wIlTT INCREASING VELOCITY c* VlocitycayS. ,C* Velocity fl/nm. |ct* Diam.ofpan tide in cm 0' Diam.ofpar tide m Haas r* Radiusofpar- tide in cm. jg18lcm./4ec? acceleration 5,-Density of particle SDensilyof Air (Very small relative fo s, y-Viscosily of airinpooes ISM x 10 for airaf 70*F. |\*IO'5cm. (Mean free path ofgas molecules) PARTICLES^MOvTukT GAS MOLECULES A* Distance of moiioninhfnet R* Gas constant 8.3l6xl0-7 T- Absolute Temperature M" Numberof Gas molecules in one nx>l,4(&IJ0i Fio. 4. Size properties of air-borne particulate matter. {After W. G. Frank.) where uc is the corrected velocity, u, is calculated by Stokes' equation, and X is the mean free path of the gas molecules (about 10-5 cm, under ordinary atmospheric conditions). For particles above Yi the correction is negligible; there is a fivefold increase in settling velocity, however, for 0.05-ji particles. i ST 0853539 10 INDUSTRIAL DUST In free-air dust suspensions, the gravity settlement of submicroscopic particles is of little importance and their movement is conditioned more by natural air currents m space. Diffusion is generally the controlling factor in the removal of submicroscopic particles from the air onto collecting surfaces. Particle Acceleration during Free Fall. Microscopic particles falling in air accelerate from rest up to the terminal velocity within a very short distance. There is little interest, therefore, in considering the acceleration phase in an analysis of behavior of such particles during free fall. . The terminal velocity may be applied to the entire height of fall. Larger particles, however, undergo acceleration over significant distances, and this zone must be properly described in many practical problems dealing with falling particles. Acceleration in Laminar Zone of Motion. Particle acceleration at any instant equals the difference between the gravitational constant and the particle resistance per unit of mass, as derived from a balance of forces. Thus, du _udu _ _ (R _ / u dt ~ ~dh ~ g M ~ g\ ~ ut Integration leads'to the following equation: 2 g--(.ah+uiu)/ut> Ut where u is the particle velocity after falling distance h and u, is the terminal velocity of the particle. This equation applies only to particles whose terminal velocities are in the streamline zone (<85 m for mineral particles falling in air). Acceleration in Turbulent Zone of Motion. Coarse particles will pass through the streamline and intermediate zones of motion in the course of acceleration in a short distance, and for practical purposes the behavior of such falling bodies may be considered only in relation to the drag coefficient imposed in turbulent motion. Since the. coefficient is taken as a constant (0.44), the velocity increases with distance according to the following equation: j/2 . = 1 - e-h'k' u? ST 0353540 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 11 where u, ut, and h are as above and ht = ut2/2g. In this equation it is assumed that the distance of fall required to reach Re = 10*, the point of transition from the intermediate into the turbulent zone, is negligible. A more exact form of the equation recognizes the distance ho and corresponding velocity w0, which mark the beginning of turbulent motion: . Ut2 ~ = e-<.h-ki)/h, U? - Uo1 Acceleration in Intermediate Zone of Motion. Since the drag coefficient varies in a complex manner with Re throughout the intermediate zone of motion, a convenient statement of the rela tionship between velocity and falling distance cannot be written. Lapple and Sheppard (275) developed a method for constructing the u vs h curve over this zone based upon graphical integration of differential relationships. By this method a fraction k is derived which corrects the time of fall to reach any velocity, calculated on the assumption of streamline motion, to yield the actual time for any particle size and velocity. The Lapple and Sheppard procedure makes use of the following equation: 4agd'p The factor k has the values given in Table 1 for different values of Zi and 4> as indicated. In use, a series of velocities are taken over the desired range up to the terminal velocity and the corre sponding values of Re are calculated. Values of C are then obtained by reference to the chart, Fig. 2, and C Re is determined. Finally, Z2 is calculated for each velocity'and corresponding values of k are obtained from Table 1. These serial values of C Re, Z2, and k together with the appropriate constants are then entered in the equation to calculate the time required to develop each of the successive velocities. From the time vs velocity ST085354 I 12 INDUSTRIAL DUST curve thus constructed, the relationship between u and h is readily obtained by graphical integration, keeping in mind that h -- $udt Calculations of velocity of fall of a 3-mm particle are given in Table 2 in -accordance with the Lapple and Sheppard procedure, and results are plotted in Fig. 5 together with a similar curve calculated for a 1-mm particle. For comparison with these kTable 1. Values of fob Fbee-faluno Spherical Particles Values of k at the following values of <f> 10 50 100 1000 10` 10` 10` 10T 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.85 0.90 0.95 0.98 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.000 1.000 1.000 0.998 0.999 0.995 0.995 0.990 0.991 0.984 0.987 0.976 0.982 0.967 0.976 0.955 0.968 0.941 0.964 0.934 0.960. 0.924 0.953 0.913 0.948 0.905 0.946 0.902 0.943 0.900 1.000 0.995 0.990 0.982 0.973 0.961 0.947 0.928 0.905 0.890 0.875 0.856 0.841 0.836 0.830 1.000 0.990 0.983 0.975 0.965 0.950 0.933 0.909 0.877 0.858 0.835 0.807 0.785 0.775 0.700 1.000 0.987 0.976 0.963 0.947 0.930 0.907 0.880 0.845 0.826 0.800 0.768 0.743 0.730 0.700 1.000 0.985 0.970 0.952 0.933 0.912 0.886 0.857 0.821 0.799 0.770 0.734 0.700 0.680 0.600 1.000 0.982 0.964 0.945 0.924 0.900 0.872 0.840 0.801 0.778 0.748 0.708 0.668 0.645 0.500 Source: After Lapple and Sheppard (275). calculated relationships, the straight line indicates the theoretical fall in vacuo. Triangles plotted on the 3-mm curve and circles accompanying the 1-mm curve represent values calculated by the equation for acceleration in the turbulent zone, using in each case, however, the correct terminal velocity. Terminal fall is in the turbulent zone for the 3-mm particle, but for the 1-mm particle the motion does not exceed the intermediate zone. The agreement is satis factory for the 3-mm particle since the shift from intermediate to turbulent motion occurs at an early point in the fall. Even for the 1-mm particle, the error in the assumption of turbulent motion is not great. ST 0 853542 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 13 3 I 2 53 x a3 II H2 ttVIfbf. 5*14 aa a CM ho 4> * X > co oI 2 2J <0- b PU=< X bO. 2O S< D O< a <a H< X 4* *c < J3 o (2 XO to* Mn6 Oa5 nWQ 9a^ 0Oh0 ONh qOo d d d d o i- h CO CO CO CO ,, iH n CO *4 S3 b 440 CO s <N CO s o cc <-4 e* CM CO CO *4f 8 cm CO od M CO CO cc b* fH s CO O H '- CM 00*< CO b- CO b CO *4 iO CO CM CM r-i 800 on03 03 cm CO p*4 CO a b Oo o N i tof> CO cm N) X m cm CO 03 cO fH Oo CM CO ** O O CM 03 ** CO Q o m CO CO CM 03 Tf 3 w co03 cO CO CO CO ** ** *-4 o CO 3 1* ** -r ** . 8 X 8 8 g 88 *rr 00 CM f-4 CM CM l g-I 3!C 8) 8N 8a 8 h 8 ST0853543 14 INDUSTRIAL DUST Dynamic Projection. Dust particles generated by industrial processes are dispersed into air by virtue of the kinetic energy imparted to them initially during formation or release. Neglect ing gravitational and other field effects, a particle is projected in a straight line through the air for a distance which depends upon its mass and initial velocity u0 and upon the air resistance. Thus, the loss in kinetic energy with distance equals the integrated product of air resistance and distance: -M \ udu - C (Kdu J u jo For large particles in the turbulent zone, (R = 0.44 X r/Spu2d2 and According to this relation ship, a 2-mm particle thrown into the air with an initial velocity of 5000 cm/sec would travel 2200 cm, or 70 ft, neg lecting gravity, before its speed is reduced to the limit Fiq. 5. Particle velocity vs. height of fall, compared with u(a -- y/2gh. of the turbulent zone (about 1000 cm/sec for a 2-mm quartz particle). In the streamline zone, on the other hand, (R = 3tm du and u -- uo -- gh u, A 10-jr particle with an initial velocity of 5000 cm/sec will, by this relationship, come to rest in about 4 cm, * and a 1-^ particle will be projected through still air scarcely any distance at all (0.4 mm) before its kinetic energy is entirely exhausted. The conclusions from these calculations are of very great significance in the study of dust dispersion in industry and in the * The distance will be somewhat greater in fact because the beginning motion of the particle will be in the intermediate zone. STO 8 53544 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 15 design of dust-control measures (212). They demonstrate the important fact that the spread of microscopic particles beyond their source into the workroom air is not dependent upon the kinetic energy of the particles; such dispersion takes place only by movement of air away from the dust source. The stream of sparks flying away from a grinding- wheel is an example of dynamic projection of coarse particles. These are of no hygienic importance, however, because of their size and are of concern in the control of dust hazards only to the extent that microscopic particles are carried along in the air stream set up by the drag of the relatively large fragments. Fundamentally, therefore, dustsuppression measures involve the control of air movement around dust sources and are not directed toward the dust itself. This point is considered more fully in Chaps. 12 and 13. Stirred Settling. Under still-air settlement, particles of a given size are removed from the air by gravity at a constant rate. With complex vertical mixing of the air such as naturally occurs in open rooms, however, this is not true and the rate of removal decreases with time. We may write, for perfect mixing, nh n = noe~(,`/A)1 where n number concentration of particles in the air at time t n no at l -- 0 h = height of settlement chamber u = settling velocity Both the rate of settling (number removed per unit time) and the concentration decrease exponentially with time. The rela tionship may be employed to determine settling velocity and the particle size of the suspension from simultaneous measurements of n and dn/dt. Brownian Motion. The mass of a microscopic particle is so small that it is driven about in the air by the# buffeting action of the gas molecules. Under equilibrium conditions the vectorial sum cf molecular blows is zero, and there is no net motion of the particle in any direction. This oscillating behavior is known as Brownian motion, which has been described mathematically by Einstein in the following terms: ST 0853545 16 INDUSTRIAL DUST t A 3ryd where A -- amplitude of motion in a given time t R = gas constant - iV"= Avogadro's number ' T = absolute temperature Brownian motion increases in magnitude with decreasing particle size in contrast to the decrease in gravitational settle ment. It is evident, then, that for some given size the combined Table 3. Comparative Particle Velocities Due to Gravitation and Molecular Impact in Relation to Particle Size Particle diameter, #* Gravitational settling velocity, cm/sec Molecular impact velocity, cm/sec 0.002 0.01 0.02 0.10 0.2 1.00 2.00 12 X 10" 3 X 10~4 12 X 10"4 3 X 10"4 12 X 10"4 3 X 10"* 12 X 10"* 6.3 X 10-* 2.8 X 10-* 2.0 X 10-* 8.9 X 10" 6.3 X 10-4 2.8 X 10~` 2.0 X 10"4 Source: After Gibba (183), effect of the two upon particle movement is minimum, the rela tive instability increasing on one side with increasing gravita tional effect and on the other with greater molecular impact. Gibbs (183) gives the comparative values in relation to size for silver particles shown in Table 3. It will be observed that gravitational and molecular-impact velocities are about the same for particles of 0.2-n diameter and that molecular velocity is higher for the smaller particles. This point of minimum activity at a particle diameter of about 0.25 ix has great practical importance in the consideration of dust behavior. It represents, for example, the most difficult particle size to remove from the air by filtration or by retention in human lungs. Smaller as well as larger particles are captured more efficiently. Movement in Centrifugal Field. Particles moving in a rotat ing gas stream are subjected to the centrifugal force which drives them away from the center of rotation. The centrifugal force is given by ST 0853546 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 17 Fe = gd*(v ~ p)r* where is the angular velocity in radians per second and r the radius of curvature of the path. Equating Fc and (ft to give the terminal centrifugal settling velocity, -we get, for the streamline zone, . = ror 18/i -- p)d1 Comparing this with the gravitational settling velocity, for the same type of flow, the following relationship is obtained: u. = rg where v is the linear velocity of the rotating gas stream. The term v*/rg is called the separation factor (285) since it measures the effectiveness of centrifugal force as compared with gravity for the removal of particles from a gas stream. In cyclone design, for example, it is evident that the radius should be small and the gas velocity high (see Chap. 14). Starting with the equations of motion in a centrifugal field, Davies (103) gives the following relationship for calculating the time required for a microscopic particle to move radially from R\ to R2: RS - Ri* At = ' 4PVoR** where Ri and Ri =* inner and outer radii of the gas stream Vo = linear velocity of rotation P = dimensionless parameter P = (<r - p) dWo !8pR2 UtVo gRt By equating t to the time of descent in a cyclone of normal design, Davies derived the following for the minimum size particle removed by the centrifugal force: 36pRi [`-(STdmin " 8(<r - p)VoH/Rt where H is the cyclone height. ST0853547 *1 18 INDUSTRIAL DUST Impingement. Particles collect on the surface of an obstruc tion around which dust-laden air flows. This is a form of cen trifugal precipitation resulting from the inertial resistance of the particle to change in its direction of travel in conformance with the streamlines of the flowing air. It is evident that the strength II |! -.....- Flo* ttrtomline Fio. 6. (a) Mechanism of impaction and (ft) efficiency of impingement on ribbon, sphere, and cylinder. {After Lapple, Ref. 335.) of the precipitating force will vary with the kinetic energy in the particle (mass and velocity), with the air resistance imposed upon the particle, and'with the sharpness with which the air flow breaks around the obstruction. Assuming that all particles which come in contact with the surface are retained, then the efficiency of collection is proportional to the ratio x/Di, as shown in Fig. 6. Davies (103) presents the following relationship between efficiency E and the dimensionless ratios: ST 0853548 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 19 VoDbp d\ F ' Db) A high, air velocity increases both P and Re. For large values of Db, Re is also increased, but this is more than offset by the lessened values of P and d/Db. Therefore, the finer the obstruc tion, for example, the fiber in an air filter, the higher is the effi ciency of collection. For obstructions of simple geometric shape, such as a cylinder or sphere, the pattern of streamlines and, hence, the ratio x/Db can be derived from classical hydrodynamics, but experimental determinations are required for complex shapes. Efficiency curves derived for three simple obstructions in a laminar-flow stream, for microscopic particles, are shown in Fig. 6 (335, 271). Application of these relationships to design and to the analysis of performance in certain types of air-cleaning apparatus is considered in Chaps. 14 and 15. In filtration, the collection of submicroscopic particles depends upon diffusion rather than inertial impingement (see Chap. 15). A special application of inertial impingement is seen in the design of a number of dust-sampling instruments in which the dust-laden air is discharged through a nozzle at high velocity against a closely positioned collecting plate. The sharp 90-deg bend in the air stream creates a strong centrifugal field, resulting in the deposition of particles in proportion to the dimensionless parameter: p _ ad1v _ UiV 18fih gh where v is the jet velocity and h is one-half nozzle width (301). The design and performance of impinging instruments in relation to basic physical relationships is considered in Chap, 8. Movement in an Electric Field. Here the force of attraction is the electric gradient acting upon charged particles, and this may be equated to the air resistance to give the precipitation velocity in the streamline zone: Fe = Ene = 3x^ du Ene U ~ iWd * where E is the field strength in electrostatic units per centimeter and ne the charge on the particle. ST0853549 20 INDUSTRIAL DUST For particles larger than 0.5 p, for which the charging process is rapid, Davies gives the following relationship from Rohmann (351) and Ladenberg (266) between charge and particle size: ne - 2 LZI) + 2/ d* where E0 is the field in the charging space and the dielectric con stant of the particle. For conducting particles this becomes 3Fods In the case of smaller particles Davies states that a full theory is lacking, but for small currents and moderate strength ne = 4.25 X 10~*d From these relationships we have, for large particles, where and for small particles (<M p) 9.5 X 1Q~*E U 6tp These equations give the values of precipitating velocity in relation to particle size shown in Table 4. Table 4. Electric Precipitating Velocity in Relation to Particle Size Conducting particles in a field with E = 10 esu (3000 volta/cm) Particle Radius Velocity, cm/sec J00 10 1 0.1 All sizes (small) 885 88.5 8.85 0.88 2.8 Source: After Davies. ST0853550 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 21 Thermal Precipitation. The presence of a clear area around a hot rod in dust-laden air was demonstrated by Aitken (3) who showed that smoke could be removed quantitatively from air passing through a hot-cold tube, the smoke precipitating on the cold surface. The precipitating force, according to Cawood (72), results from the decrease in concentration and velocity of the gas molecules along a temperature gradient. Equating the excess momentum acting on the upstream side of the particle to the air resistance, Cawood obtains the following relationship for thermal precipitating velocity: (> + !) dT dx where p = gas pressure T = absolute temperature dT/dx -- uniform thermal gradient in hot-cold space The dependence of u upon the particle diameter in the equation is not correct, according to Cawood, but results from a basic assumption made in the formulation respecting convection cur rents. For particles of microscopic size (> X), Davies (103) gives the following equation: 0.036 dT U T dx . The thermal force is small, and to secure a significant precipi tating velocity, dT/dx must be made high. This is accomplished in the dust-sampling thermal precipitator (Chap. 9) by making the distance x very small. Thermal precipitation accounts in part for the blackening of cold walls above radiators and for the pattern of dust deposit on plastered ceilings. It has not been applied to large-scale air cleaning, although it is employed commercially for the collection of lampblack. FLOCCULATION Dusts from materials like quartz and marble#differ from fumes (magnesium oxide, for example) in their flocculating character istics. Freshly formed discrete particles of magnesium oxide are often below 0.1 n in size and therefore exhibit violent Brownian motion in air. This increases their frequency of collision, with the consequent formation of flocculated masses. Whvtlaw-Gray ST085355 I 22 INDUSTRIAL DUST and others (442) showed that the rate of flocculation in still air is predictable and that suspensions of such fumes clear up rapidly owing to the formation of floes with sufficient mass to settle. Particulate masses of fumes also tend to stick rather tenaciously to vertical walls and other surfaces with which they collide. The time course of flocculation in a homogeneous smoke, measured by the decrease in the number of separate particles in the suspension, is given by the relationship (442) - --dt = fKcnn1 1-1 kt n n0 where n is the number concentration at time t and k is a constant which is independent of particle size and concentration,1 having the calculated value of about 3 X 10"10 cc/sec and a somewhat larger value in experimental clouds. Expressing the coagulation rate as the percentage decrease in number concentration per hour (245) -100--n = 1.08 X 10~4n it is seen that, with dust concentrations ordinarily encountered, the rate of flocculation is negligible; thus, with an extreme dust concentration of n = 104 per cubic centimeter (300 million per cubic foot), it amounts to only 1 per cent per hour. For typical industrial dusts this concentration would exceed 100 mg/cu m. In contrast, a fume with a particle size of 0.1 m will undergo 50 per cent flocculation in the same time when the weight concentration is no more than 1 mg/cu m. These differences in particle size and concentration of industrial dustB as compared with fumes explain the relative unimportance of flocculation in dust clouds. As a dust cloud clears up, the size of the particles remaining in suspension decreases and the degree of dispersion increases, i.e, the ratio of flocculated to discrete particles becomes less. Con- 1 In the region below Stokes' law, the Cunningham correction introduces a particle-size effect and the change in particle size of floes with time causes k to vary also with concentration. In a heterogeneous smoke, the particlesize distribution has additional effect on k. The shape of the particle has negligible influence. ST0853552 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 23 versely, the percentage of floes and their size both increase with the age of a metallic fume cloud. This difference between dusts and fumes is nicely demonstrated by Brown's photographs (58) in Fig. 7. 103-128 220-250 500-690 MgO--Minute# after cloud formation. 0-2 29-34 100-130 212-312 436-1440 CaCOj--Minutea after cloud formation. Fio. 7. Variation in particulate sire of magnesium oxide a^d calcium carbonate with age of cloud. {After Brown, courtesy J. Induti. Hyg.) The foregoing considerations have to do with direct flocculation in air. There is another and quite different source of dust flocculation which has considerable practical importance. This is related to the origin of the dust cloud and the way it is dis- ST0853553 24 INDUSTRIAL DUST parsed into the air. We may properly distinguish between true dust-generating processes, wherein microscopic particles are formed from larger masses and are immediately distributed into the surrounding air, and the simple dispersion of dust from a bulk of previously ground material. In the first case, the degree of flocculation in the dust,cloud will be subject to the foregoing law and thus limited by the concentration. A cloud formed by simple dispersion, on the other hand, may exhibit a marked degree of particle aggregation simply because these aggregates, naturally present in the original bulk material, are not broken up in the dispersing process. The aggregates are tenacious, and a high degree of dispersion from bulk is therefore obtained only with a considerable expenditure of energy. The dust generated Fig. 8. Effects of turbulent air motion and of steam jets (local humidification) on the stability of silica dust clouds. Dry air refers to normal room air with about 60 per cent relative humidity--not ohemically dried air. {Courtesy J, Indust. Hyg.) by pneumatic chisels in stone cutting, for example, is relatively highly dispersed, whereas the cloud arising during the handling from storage and packaging of previously ground silica is char acterized by considerable floccu lation. Aggregates of fine particles take on the dynamic proper ties of equivalent large particles. Hence, they are relatively easily removed from the air and, when inhaled, are retained in the upper respiratory tract. A dust cloud formed by simple disper sion from bulk is inherently less dangerous, therefore, than the same concentration produced by a true dust-generating process. This practical aspect of dust flocculation has received too little attention in the analysis of dust hazards. Xo quantitative dis tinction is ordinarily made between the relative degrees of aggregation in dust clouds, despite the fact that very marked differences of considerable physiological importance do exist (218). The Effect of Air Motion and Humidification upon Flocculation. Turbulent air motion accelerates the formation of floes owing to ST0853554 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 25 greater frequency of collision as compared with the rate in still air (417). This applies to suspensions of fumes and mists which flocculate easily, but no great improvement is observed with true dusts. Thus, in Figs. 8 to 10 are shown the comparative effects of air motion upon the settling rates of dusts, fumes, and smokes. Commenting upon these curves, Drinker, Thomson, and Finn (129) state that "turbulent air motion was found to have no effect on silica dust, a marked effect on freshly generated zinc Fio. 9. Stability curves of zinc oxide fume made by exploding zinc powder and potassium chlorate. Note the effects produced by turbulent air motion and by steam jets. Both cause the particles to aggregate into units large enough to fall out of the suspensions. (Courtesy J. Indust. Hyo.) Fio. 10. Stability curves of tobacco smoke. Air motion appears to exert less effect on tobacco smoke than on zinc oxide (see Fig. 9). Curve C represents air saturated with mois ture before the smoke was intro duced--i.e., general humidification. (Courtesy J. Indust. Hyo.) oxide, and a considerable effect on tobacco smoke." A fume of lead particles, which do not flocculate vigorously, probably would not be greatly affected by air motion. Variations in the humidity of the air below saturation have no effect upon the stability of aerosols. It is sometimes alleged that dustiness in a factory is worse on still, humid days than in dry weather because of the greater stability of the dust cloud. We have never seen figures to substantiate this claim; it may have arisen from the fact that dustiness is far more apparent in wet 28 INDUSTRIAL DUST than in dry weather and also from the fact that the greater air movement on dry days carries away more dust. Supersaturating the atmosphere with moisture does have a noticeable effect upon suspensions of dusts and fumes owing to the fact that the particles act as nuclei upon which the moisture condenses. The application of live steam in air cleaning is more effective than a water spray. In Figs. 9 and 10 is shown the rapidity with which clouds of zinc oxide and tobacco Bmoke can be cleared up with steam. In contrast to this, Warren (436) found the efficiency of water blasts for cleaning mine air to be only 62 per cent. During dry drilling, external water blasts do not improve conditions, according to Harrington (206), while Gray (188) states that water blasts and sprays fail to bring down the really fine dust.1 OPTICAL PROPERTIES The presence or absence of suspended dust in the air is easily demonstrated by directing a beam of light through a darkened room containing the dusty air. The beam will not be revealed unless there are suspended solid or liquid particles to reflect the light. This test, which was first used by Tyndall in his classic studies of atmospheric pollution, is one of great sensitivity. The optical behavior of an aerosol varies with the nature of the suspended material, such as its transparency and shape, but it is influenced to a greater degree by the size of particles in the suspension. Distinction may be made in this connection between two classes of particles: those larger than the wavelength of light, which reflect and refract light according to the general optical laws, and a second group containing particles sensibly smaller than the wavelength of light. These particles scatter light in all directions with an intensity that varies with the wavelength of the light; the light is polarized to a considerable extent. The light scattered by large particles is also polarized to some extent in a plane perpendicular to the incident beam. Particles Larger than the Wavelength of Light. Tolman (414) has shown that the intensity of light reflected by particles larger than 0.6 to 0.7 m is given by the equation 1 See Chap. 16 for a discussion of spray-type air cleaners. ST 0853556 PHYSICAL PROPERTIES OF DUSTS, FUMES, AND MISTS 27 kc Id where I c d Since intensity of reflected light concentration (weight) of dust per unit volume particle size c Id'an where <r =< density of dust particles n = number of particles per unit volume of the suspension we may write I =tfc,nd* where k' includes several physical constants pertaining to the dust. Thus, the strength of the Tyndall beam varies directly Fio. 11. Relation between tyndallmeter reading and particle size expressed in terms of M, and <ra. {Couriety J. Franklin Init.) with the surface area concentration of the particles in the sus pension. For equal weight concentrations per unit volume, however, the strength of the beam varies inversely with size (Fig. 11). Particles Smaller than the Wavelength of Light. In this region the intensity of the beam varies, according to Rayleigh, ST0853557 28 INDUSTRIAL DUST with concentration, size, and wavelength of the incident beam in the following manner: j lend6 k'cd* where X = wavelength of light Again, the intensity varies with the concentration of dust in the suspension. It is also influenced to a considerable degree by the wavelength of light; red rays, for example, are scattered with only one-twelfth the intensity of the rays at the short end of the spectrum. Conversely, the long rays are transmitted through a suspension to a greater degree than the violet rays. Hence, the Tyndall beam devel^ed by minute particles appears blue in color when viewed at right angles and red when examined from the end. This explains the blue color of the sky, which is produced essentially by light scattered by gas molecules and minute particles, and the red at sunset, which comes to us by transmission through the dust atmosphere near the earth's surface. For equal weight concentrations, the intensity of the scattered light increases rapidly with particle size to a maximum in the region corresponding to the wavelength of the incident beam and then decreases less rapidly with a further increase in size, the exponent of d changing from 3 to --1. This is nicely shown in terms of the variation in strength of the transmitted beam with particle size (407) in Fig. 12. A more complete theoretical treatment of the laws of light scattering by small particles was developed by Mie (313). During World War II, this was employed extensively in the optical study of homogeneous aerosols by La Mer and associates (245) who developed methods for determination of particle size and concentration, based upon the selective scattering and trans mission of light of different wavelengths and the variation in degree of polarization with particle size. The method is limited, however, to the.study of particles of uniform size and has little application to the study of heterogeneous industrial dusts. Obscuring Power. The intensity of a light beam passing through a dust suspension when viewed on end decreases with an increase in the distance from the light source as well as with an increase in dust concentration. Simon and his coworkers (389) ST0853558 PHYSICAL PROPERTIES OP DUSTS,,FUMES, AND MISTS 29 Fio. 12. Variation in light transmission with particle size. (After SluU, courtesy J. Franklin Inst.) have shown by theoretical considerations, assuming a suspension of opaque spherical particles of uniform size, that the intensity of light changes according to the logarithmic equation L =.Lo*rn(r/4)d'' = LaeM/* where L and L0 = intensities of incident and emergent beams, respectively l = length of path between points where L0 and L are measured n = number of particles per unit volume of air m -- weight concentration of dust per unit volume of air a = density of material of which the dust is composed ST0853559 30 INDUSTRIAL DUST Written in another way, this relationship shows that the per centage reduction in light for a given column of the dust-laden air is constant, regardless of the intensity of the incident beam, and that the percentage value varies directly with the number of particles, length of path, and square of particle size. The correctness of this theoretical equation was demonstrated by Simon (389), who describes a method of measuring the rela tively heavy concentration of dust in blast-furnace gas based upon this equation. It is frequently suggested that this phenomenon could be used as a simple method for determining the concentration of dust in an industrial establishment. The application of the above equa tion to a practical problem, however, indicates the fallacy of this contention. Assume a concentration of 10 million particles per cubic foot of air (350 particles per cubic centimeter) with a uniform diameter of 2 n, and determine the distance l necessary to reduce the light intensity only 5 per cent, i.e., from 100 to 95. Entering these values in the above equation, we get l = 47 m Obviously, this distance is too great for practical use, although to be effective any dust recorder must be sensitive to a degree as dose as 10 million particles per cubic foot. ST 0853560 CHAPTER 2 EFFECTS OF DUSTS AMD FUMES UPON MAN Exposure to dusts can produce several distinct types of dis ability: (1) the pneumoconioses are caused only by dust inhala tion; (2) systemic toxic effects are produced as the result of either breathing or swallowing of certain dusts such as lead and manganese; (3) metal-fume fever is caused by inhaling certain metallic oxide fumes; and (4) an allergic reaction, as typified by hay fever, is the direct result of breathing pollen or other organic substances. Dust inhalation is the usual cause of disability; only in the case of a few dusts are there other modes of entrance. Respiration and Dust Inhalation. The lungs are nonsymmetrical bilateral structures encased in a rather elastic cavity, the chest, and they communicate with the nose and mouth through the trachea, or windpipe. The left lung has two divi sions, or lobes, and the right lung has three; the right lung is about 12 per cent larger than the left. (Fig. 13) RIGHT BROHCHUS UPPER LOBE RIGHT LUNG--... BRONCHIAL / RAMUS TO UPPER LOBE !l' ERARTERIAL-fc 11 BRONCHIA RAMUS TO MIDDLE LOBE > MIDDLE--( LOBE [ .BRONCHIAL-V 'RAMUS \TO LOWER 11 : LOBE \. 'lower LOBE-J TnsKONcrm--i BRONCHIAL RAMOSE, nrypm uoBE- j " .UPPER LOBE ) ^//BB^^^HjOWER LOBE Flo. 13. Lungs, bronchi, and trachea. (After Sobotta and McMurrich.) - 31 ST085356I 32 INDUSTRIAL DUST In the normal adult, the trachea is about 2 cm in diameter and is fortified with ringlike cartilage with an opening in the posterior part. The trachea is, therefore, strong, fairly rigid in front, and somewhat elastic in back. At the approximate level of the fourth rib, the trachea branches into the bronchi, and these in turn subdivide into bronchioles which lead to the terminal air sacs, or alveoli. It is in the alveoli that gas exchange takes place between the blood and air. Oxygen is taken up by the red blood cells, and carbon dioxide is given off. Table 5. Oxtoen Consumption and Volume or Bbeathino bt Man Oxygen consumed at 0C. and 760 mm. pressure, liters per minute Air breathed at 20C., liters per minute RMtftng in bed.................... Sitting................................. Standing.............................. Walking 2 m.p.h................ Walking 4 m.p.h................ fllnwr nin............................. Maximum exertion............ 0.24 0.30 0.36 0.66 1.20 2.00 3.00-4.00 6 7 8 14 26 43 66-100 Source; After Heodenon end Haggled (231). The amount of air breathed and the oxygen consumed vary with the task performed and with the individual's size. The figures for an athletic man weighing 150 lb are shown in Table 5. The untrained man is apt to exceed these figures when per forming comparable exercise--thus, in a contaminated atmos phere, the untrained person will work harder and breathe more often than the trained athlete. The inspiratory and expiratory phases are not exactly alike, but practically we may consider each as taking half the time required for a corfplete respiratory cycle. Thus with a minute volume of 50 liters, the actual inspiration is at the rate of 100 liters/min, and momentarily rather high velocities occur in the trachea. The velocity in the alveoli proper, however, is prac tically zero at all times because each alveolus is a dead end. The slight surge back and forth with respiration must be very close ST0853562 EFFECTS OF DUSTS AND FUMES UPON MAN 33 to still-air conditions. Thus there cannot be any driving or high speed impingement of dust particles into the lung tissue. Any impediment to breathing is annoying, and if severe it may be alarming. No one, strong or weak, will voluntarily work under conditions that cause respiratory embarrassment. This fact is of the utmost importance in the design of protective equipment, as will be shown in Chap. 17. The Fate of Inhaled Dusts. A dust particle the size of a common pollen grain (15 to 25 m) is likely to be caught in the nasal passages or at the back of the throat. If it should enter the trachea near the center line, there is no reason why it should not pass on down to the bronchi, but it is not likely to reach the alveoli. Collection of such a particle is the result solely of chance impact against the moist walls of the respiratory tubes. Obviously such impact takes place most effectively with particles large enough to have appreciable momentum and rapidly ceases to be effec tive as the particles approach sizes at which they move as an integral part of the transport ing gas. Lining the trachea and extending down to the lower ends of the bronchioles Fio. 14. Phagocytic cells containing dust, from sputum of man working in a dusty plant. * (Courtesy J. Indust. Hyg.) are myriads of cells with whiplike appendages, cilia, which carry upward any foreign bodies that chance to touch the wet mucus- bathed linings of the respiratory passages. The nasal passages S T0653563 34 INDUSTRIAL DUST likewise are bathed in mucus and lined with cilia. All the mucus moves toward the exits of the' nose and mouth and is never stagnant. Within the alveoli are other cells, phagocytes, which are brought out in vast hordes by the stimulus of foreign bodies, such as dust particles, which they engulf (Fig. 14) (123). The dust-laden cells, which have the power of independent motion, Fro. 15. Position of lymph nodes in relation to the trachea, the bronchi, and the pulmonary artery. (After Gray's Anatomy.) may pass through the walls of the lung tissue into the lymph and thence into the blood capillaries surrounding the lungs, or they may pass to the finer bronchioles, from which they are removed by ciliary action; thus they eventually reach the mouth and are spit out or swallowed. Within the alveoli there are neither cilia nor mucus. Most of the dust-laden cells, however, migrate into the lym phatic system, which starts as a meshwork of fine vessels and drains the tissue spaces. These fine vessels come together, forming larger and larger vessels which finally discharge the lymph into the blood stream (Fig. 15). At the various bifurca tions of the trachea and the bronchi, the lymph passes through glands or lymph nodes, one of whose functions is the filtration of ST 0853564 EFFECTS OF DUSTS AND FUMES UPON MAN 35 foreign bodies. It is at these tracheobronchial lymph nodes that a great deal of dust is deposited by the phagocytic cells, and it is here that fibrosis of healthy lung tissue starts, following quartzdust inhalation. Dust particles can pass from the alveoli into the lymph circula tion without having been phagocytosed (118). Such particles then can be picked up by phagocytes at any point in the lymph stream or in a lymph node, the latter being particularly suited to such phagocytosis. Fenn (149) found that all dusts are not phagocytosed with the same readiness; he gave cells an equal chance to ingest various dusts and found that quartz was among those least preferred. Gardner and Cummings (176) noted that the motility or rapidity of migration of cells differed with different dusts, but no prog nostic use has been made, so far as we know, of these interesting observations. PHBUMOCONIOSIS It has been recognized for centuries that excessive dust inhala tion can produce serious pulmonary disease which has been known in the various dusty industries as rniners' asthma, miners' phthisis, grinders' rot, etc. Zenker (458) in 1867 proposed the general name -pneumonokoniosis (a lung containing dust) in place of the special names applied in certain industries. Later this was shortened to pneumoconiosis (240) by no less a body than the International Labour Office, but various spellings continue. The word originally implied that the lung had been seriously damaged by dust--enough to cause disability--but the meaning has been broadened in recent years to include all pulmonary manifestations of dust inhalation, whether the dust is injurious or harmless. Silicosis and asbestosis are still the most important forms of pneumoconiosis. Names such as silicatosis, anthracosis, anthracosilicosis, siderosis, and byssinosis have been given to other forms of pneumoconiosis, and new names are*added as studies of the dust problem progress. Silicosis. For reasons still unexplained silicon dioxide as quartz (free silica) produces the most serious form of lung fibrosis. The American Public Health Association definition of silicosis (11) states that it is a "disease due to breathing air ST0853565 36 INDUSTRIAL DUST containing silica (SiO) characterized anatomically by generalized fibrotic changes and the development of miliary nodulation in both lungs, and clinically by shortness of breath, decreased chest expansion, lessened capacity for work, absence of fever, increased susceptibility to tuberculosis. . . . " The International Silicosis Conference at Johannesburg in 1930 defined silicosis (241) as a Fia. 16. Silicosis. Isolated silicotic nodules above; fine nodules below. (After Gardner, courtezy U,S. Public Health Service.) "pathological condition of the lungs due to the inhalation of free silica dust. It can be produced experimentally in animals. It can be detected by clinical and radiological means, which can be confirmed with the above pathological condition with sufficient accuracy to separate it from other pneumonoconioses. It also affords a fair basis for legislative measures." In general, the damage done in silicosis (and asbestosis) is per manent ; an unalterable tissue change takes place in the lungs. Of prime importance is the fact that prolonged exposure to these dusts results in increased susceptibility to tuberculosis, more so from quartz than from asbestos. Gardner showed in the labora tory the great importance of this fact which had long been ST0853566 EFFECTS OF DUSTS AND FUMES UPON MAN 37 recognized in industry. Deaths from uncomplicated lung fibrosis caused by dust are infrequent, but they have been reported (348). Free quartz seems to possess a peculiar cytocidal power and can kill phagocytic cells which disintegrate and thereby release their dust load. The surrounding tissue then begins to fibrose and gradually becomes more or less stringy, as is shown in Fig. 16 and 16a; such fibrotic nodules contain dust. \ Fia. 13a. Barre granite cutter. Two isolated silicotic nodules. Cellular connec tive-tissue borders and hyaline fibrous centers. Thickened interlobular septum extending upward to the left of the right nodule. Note dilated lymph vessels in septum. (After Gardner; courtery U.S. Public Health Service.) Characteristics of Silicosis. In 1930 silicosis was conven tionally reported as being present in one of three stages. In the first, the disease did no measurable harm (and produced no dis ability). The victim could work as well as ever. But as his condition progressed to the second stage, his respiration was affected, he was bothered by dyspnea, or labored breathing. If his dust exposure continued (and often even if he kept out of dusty air), he was likely to reach a third stage in which dyspnea became severe and to contract pulmonary tuberculosis, generally with fatal results. Whether he developed tuberculosis or not, the health of the person with advanced silicosis was far below normal. We question whether such divisions are valid today, simply because the epidemiological picture of silicosis has changed so. ST0853567 38 INDUSTRIAL DUST l Silicosis is diagnosable by x-ray only if a good history, with proof of adequate dust exposure, is available. Anyone with normal vision can follow the changes that appear in a series of x-ray plates of the chest taken of a man who has had a severe dust exposure over a number of years and ultimately died of silicosis. Such a series is, today, something of a curiosity. The modem medical student is about as apt to see a case of typhoid fever as he is one of silicosis; so familiarity with the disease is not to be expected. Silicosis and Duration of Exposure. Silicosis may not become disabling until some years after dust exposure has ceased. Watkins-Pitchford (437) gave examples of Welsh miners who passed the physical examination for enlistment in the British army, fought in the trenches through World War I, then came I i back to England and died of silicosis. Britton and Head (54) ! gave more detailed' examples of similar latent effects in the United States.1 This problem of latency may be embarrassing--it is not reassuring to a client to state that some dust-control measure you recommend cannot really be appraised until the men exposed have worked through this vague latent period. Harrington (207) of the U.S. Bureau of Mines assembled data ii on the length of exposure required to give definite silicosis; these showed that first-stage silicosis could develop in as short a time ii as 8 months. Among foundry workers where the risk is low, McConnell and Fehnel (305) in. 1934 and Pope and Zacks (338) in 1935 found first-stage silicosis only after long employment. But in severe quartz-dust exposure the condition is very likely to progress and to become complicated by tuberculosis whether the man leaves his dusty occupation or not. Thus the length of exposure that will produce the disease varies with the working conditions and individual susceptibility. In Great Britain the reports of the Chief Inspector of Factories show the number of deaths from silicosis as well as the ages of the victims. We show Tables 6 and 7 taken from the reports of 1934 and 1947. One could compile the yearly figures and the rates for silicosis, but we believe that the progressive increase in age at death is the important item. We doubt the value of yearly figures or of rates because of this vague latent period of the 1 We emphasize it further in Fig. 34, p. 107, from South African data. ST 0853568 EFFECTS OF DUSTS AND FUMES UPON MAN 39 disease which makes it impossible to fix causative exposures with any semblance of accuracy. From all parts of the industrial world the indications clearly point to a lengthening of the time required to produce silicosis. Table 6. Fatal Cases or Silicosis and Asbestosis Investigated up to End or 1934 (Great Britain) * Duration of Number Average employment, years of age at deaths death Maxi Mini Aver mum mum age Silicosis.......................................... Silicosis with tuberculosis............ Asbestosis...................................... Asbestosis with tuberculosis......... 281 315 41 26 55.4 52.5 41.0 38.0 60 2.3 34.8 67.0 2.0 32.0 27.0 1.5 12.9 29.0 0.8 9.9 Source: After Bridge (62). Table 7. Fatal Cases or Silicosis and Asbestosis Investigated up to End or 1947 (Great Britain) Duration of Number Average employment, years of age at deaths death Maxi Mini Aver mum mum age Silicosis.......................................... Silicosis with tuberculosis............ Asbestosis...................................... Asbestosis with tuberculosis........ 1037 1046 160 72 Source: After Barnett (25). 58.2 53.6 47.5 39.0 62.0 1.5 34.3 67.0 0.7 31.3 48.0 0.5 14.9 29.0 0.8 10.4 The improvement is partly due to the decreased incidence of tuberculosis and not solely to better working conditions. In 1913 the Metropolitan Life Insurance Company established a tubercu losis sanitarium for its own employees, and'in 1945 they cele brated its abandonment because they no longer had enough patients to justify maintaining it. This event comes close to being a milestone in public health and shows how spectacularly the tuberculosis rate is being reduced. ST0853569 40 INDUSTRIAL DUST Joseph. (249), summarizing 25 years' experience (1913 to 1938) in the Rand mines, shows (Fig. 17) the remarkable lengthening in the exposure time needed for development of silicosis in that famous mining community. We have no data to prove it, but our opinion is strongly that this graph indicates the epidemiological trend of silicosis in the m Fio. 17. Length of service vs. rate at which silicosis was produced at dates indi cated; Witwatersrand mines. {After Joseph, courtesy J. Chem., Met. Mining Soc. S. Africa.) modern industrial world--a steady and consistent lengthening of the time required to develop the disease. This is tantamount to saying that both the frequency and the severity of silicosis are steadily decreasing. We are all familiar with Agricola's epidemiological observa tion (2) that many women in the Carpathian mining district married seven husbands who were carried off to an early death-- presumably by silicosis. We cannot question his mortality figures, but we do question his etiology. This remarkable book ST0853570 * EFFECTS OF DUSTS AND FUMES UPON MAN 41 on metallurgy was published in 1556. Blasting and pneumatic rock drilling, the main dust producers in mining, are a product of the end of the last century. Dust exposures, as we know them, did not exist in Agricola's time. If tuberculosis had been con trolled among the Carpathian miners, we doubt that their mor tality would have been unusual. - A significant part of the increase in pneumoconiosis in Britain occurs in their coal miners. It is not a new disease in coal mining, it is found only after years of work in coal dust, it is responsible for peculiar and distinctive chest x-ray markings, it is often dis abling and it is compensable. There is no thought among the British authorities that coal miners' pneumoconiosis is a new disease. Fletcher (159, 238) sums up the present British situation by stating that from 1931 to 1948 there were 22,000 men (90 per cent from South Wales) certi fied as disabled from coal dust. These men came from about 100,000 underground workers, while only 600 were certified as disabled from 600,000 miners exposed elsewhere in Great Britain. The importance of the dust hazard, in its effect upon both the death rate for tuberculosis and the death rate for all causes, is shown in Table 8, giving the number of actual and of expected cases (based upon general experience) among workers in the chief dusty trades. These data, which represent the combined experi ence of 12 life-insurance companies from 1915 to 1926, show excess mortality varying from 114 to 450 per cent of the expected rate for all causes and from 103 to 1833 per cent for tuberculosis. In general, the mining, quarrying, and stone-dressing operators show a higher hazard than the general manufacturing workers. The Employability of Workmen with Silicosis. We like what Cummins (89) wrote about the disability of the person with silicosis: "It may be said of pneumoconiotic cases in general that what most interests the clinician is the mottling seen in x-ray films; what chiefly attracts the pathologist is the mystery of the silicotic nodule; and what distresses the patient is shortness of breath." There has been much work directed toward appraising this disability, for there is nothing more distressing than difficulty in breathing. The subject is complicated, and it is overoptimistic, perhaps, to expect a formula whereby percentage disability can be fixed by physiologic tests, with or without x-rays. No one i I ST085357I INDUSTRIAL DUST T able 8. N umber of D eaths E xpected from Specified Causes and N umber W h ic h A c tu a lly Occurred among Persons E ngaged in C e r t a in Oc c u patio n s E xpo sed to Sil ic a D ust (U n it e d St a t e s ) Source; Ordinary department mortality experience of 12 life insurance companies, 1915-1020 <274). * ST 0853572 EFFECTS OP DUSTS AND FUMES UPON MAN 43 appreciated these difficulties better than the late L. U. Gardner, whose wealth of experience gives his opinions unusual value. At the request of the Department of Labor and Industry of Min nesota he discussed the subject in their Thirtieth Biennial Report (1945-1946) with special reference to the silicosis problem in their iron mines. What he says applies so generally that we quote parts of his report (171), one of the finest pieces of work in this field: In the absence of associated tuberculosis of the lungs, silicosis does not ordinarily cause symptoms or disability. Most of the disability in silieotice is a result of associated tuberculosis. Silicosis is a menace largely because its presence predisposes to fresh tuberculous infection from without, and because, in combination with the tubercle bacillus, inhaled quartz produces massive fibrosis of the lungs. Contraction of this fibrous scar causes the air spaces in the rest of the lung to over-distend in order to fill the chest cavity. This process of dktention is known as compensatory emphysema, and it is emphysema, rather than fibrosis, that gives rise to shortness of breath. Since so many of the older silicotics had associated chronic tuberculosis, short ness of breath came to be recognized as the cardinal symptom of the disease. However, it should be borne in mind that, without tuberculo sis, silicosis alone causes little emphysema. Some uncomplicated silicotics may also have emphysema because it is prone.to develop in older men, but in them it is not caused by the dust disease. The problem that faces employers, industrial physicians and com pensation officials today is the disposition of cases of silicosis, largely produced by exposure to heavy dust concentrations fifteen or more years ago. At that time there was no general appreciation of a hazard. Today's adjustments to this situation must involve compromises, which it is hoped will become less frequent after the present generation is gone. New employees who have worked only under controlled atmospheric environments should create few problems of this nature. To discharge all men now discovered to have silicosis will not correct the damage that has already been done. Change to surface employment may be tem porarily acceptable to a miner but, being a specialist, he is rarely able to command as high wages in another job. Compensation may amelio rate the economic strain, but such payments can onlv he temporary. The mere knowledge that he has a pulmonary disease of such nature that it necessitates loss of earning capacity may transform a strong and healthy workman into a neurotic invalid. For these reasons, it would seem ill advised to recommend that every case of simple silicosis be dis charged as soon as the diagnosis is made. ST0853573 44 INDUSTRIAL DUST . If the subject is comparatively young, in his twenties or early thirties, there is more reason to advise change of employment than in men over i 45. If an iron miner, he may be kept out of development work where I there is apt to be some exposure to quartz dust, j In men over 45 who develop silicosis not complicated by tuberculosis, , there is even less reason for change of employment. In all probability the disease has taken a lifetime to develop under the high dust concen. trations which prevailed before the hazard was locally recognized. ' Transfer to positions where there is less free silica and much less dust because of modem methods of control may ultimately do less harm than discharge. As long as such men remain with their original employers, . they are subject to periodic examination, which will detect superimposed I tuberculosis in early stages when it is amenable to treatment. Dis! charged from their jobs, they lose the benefits of such control, for the I silicotic nodulation in their chests is a cause for rejection in any plant i using x-rays as part of its physical examination program. A few such rejections may turn an able workman into a discontented neurotic. : The young silicotic workman who develops tuberculosis should be sent to a sanatorium as promptly as possible. Only there has he any chance ` to cure his infection, and there he is not a menace to the public at large. Old silicotics with massive conglomerate disease in which latent tuberculosis generally plays a part are apt to be partially disabled by short fness of breath. Sanatorium treatment does them no good; in fact, to put them to bed merely increases their dyspnea. | In this country, the most acceptable compromise has been continued j employment at jobs compatible with the subject's condition. Many ! of them are able to do regular work as miners; some can be usefully employed as pump men or at other jobs that do not involve severe physical exertion. The major difficulty is to find enough jobs of this nature to keep such old employees on the payroll. Experience has demonstrated that most of them do reasonably well j for prolonged periods. Followed in annual examination films over i periods as long as ten or twelve years, their disease gradually increases ` in extent and their shortness of breath becomes more marked. Sputum j examinations should be made from time to time to make certain that j their infection has not become active and that they consequently are not a public health menace. Negative results may be expected until such time as the x-{ay reveals more rapid changes in their disease, i When this finally happens, hospitalization for the protection of others is j I indicated. I j This recommendation may seem heartless but, for the most of these i cases, it is perhaps the kindest treatment that can be offered. Until . medical science finds some means of combating the infection, the expect- ST 0853574 EFFECTS OF DUSTS AND FUMES UPON MAN 45 ant treatment is as good as anything that can be offered for these tragic results of past ignorance. Asbestosis. The pathologic changes produced by asbestos are not like those of silicosis. The asbestos fibers group about the neck of an alveolus and stimulate the formation of a diffuse fibrosis. There is no definite migration or transportation of the dust particles to the lymph nodes and no formation of the fibrous nodules shown in Fig. 16a. As the fibrosis increases, the reduc tion in lung area causes serious dyspnea. Lanza (273) suggested that the enlarged hearts noted frequently in his cases of secondstage asbestosis may be the result of the increased work of the heart resulting from this condition; it takes more work to pump blood through the asbestotic than through the normal lung. Gardner stated (175, 170): "On grinding these fibrous min erals to a very fine state of subdivision they do not become more irritating but practically lose all power to provoke tissue reac tion . . . ." Vorwald ei al. (433) continued the animal work initiated by Gardner and concluded: "The duration of exposure required to develop the pulmonary reaction to inhaled asbestos dust is inversely proportional to the concentration of long fibers in the atmosphere; as the concentration is increased, the reaction develops in shorter time." In silicosis it seems to be a general rule that, after a certain point, the victim's condition grows worse even if his exposure to dust has ceased. But Wood and Gloyne (455) stated that they have seen patients with asbestosis "whose condition appears to have remained stationary since stopping work in the factory," but they advised definitely that the individual with asbestosis be removed from his dusty job. Merewether (311) and Lanza were less certain on this point. Asbestosis Bodies. In the lungs of patients who have died after prolonged exposure to asbestos dust and in the sputum of men with considerable asbestos-dust exposure are found what first were called curious bodies and later asbestosis bodies (Fig. 18) (140). While somewhat similar bodies can occur in the lungs of coal workers and even of normal persons, it is admitted that asbestosis bodies in sputum are characteristic of asbestosis. Stewart (402) gives considerable diagnostic weight to their pres ence as do Sparks (397) and Gloyne and Merewether (184). J ST0853575 - 46 INDUSTRIAL DUST Asbestosis and Lung Cancer. The British require autopsies of persons who have allegedly died as a result of industrial exposures such as cause asbestosis or silicosis. The 1947 report of the Chief Inspector of Factories (25) states that, of 235 cases of asbestosis autopsied between 1924 to 1946, 31 or 13.2 per cent were com plicated by carcinoma of the lungs or pleura. This figure should Fio. 18. Asbestosis bodies in sputum. (.After EUman, Ref. 140; courtesy J. Indust. Hyg.) be compared with that of their cases of silicosis of whom 6884 ; were autopsied over the same period and in which 1.32 per cent ' showed cancer of the lungs. This latter is about the rate ij reported in the 1946 census in the United States (13 per cent of !; all deaths were from cancer and 1 per cent from cancer of the : i respiratory tract). ;j We do not imply that our American pathologists and our = hospitals are less careful than the British in collecting data from ; autopsies. For example, Vorwald and Karr (434) at the Saranac '! Laboratories reviewed such data from their own experience and concluded that "inhaled dusts," except those containing recog : nized carcinogenic substances, "cannot in general be considered ST 085357"; . 48 INDUSTRIAL DUST One of the most important duties of the Bureau of Mines is to . advise our mining industry in matters of safety. The prevention of fires and explosions in mines falls to their lot (see Chap. 6). By 1930 the dusting of bituminous mines, to prevent explosions, had become an accepted practice and the Bureau was charged with recommending dusts that could be used safely and would not cause silicosis. The dusts had to be cheap, which means that the minimum of handling and of processing could be allowed. l Fio. 19. (a) Liver of rabbit 1 year after injection of 500 mg of 1 to 3 fi quarts. (Course of 20 injections in 1 month, each dose contained 5 cc of 1 per cent suspen sion in physiological salt solution.) Massive silicotic cirrhosis and fibrosis. (6) Same, with addition of 0.33 per cent gelatinous colloidal alumina. (After Gardner, courtesy J. Indust. Hyg. & Toxicol.) In order to carry out this assignment Miller and Sayers (315) adopted Mavrogordato's (299) intraperitoneal method of testing the toxic effect of dust on guinea pigs. As a routine they found that it was best to run all tests with controls of quartz and anthracite coal dust and to kill their animals at intervals of 14, 45, and 90 days, although their first experiments were run for as long as a year. They found that it was practicable to divide the commercially available dusts into three general classes: (1) those causing an absorptive reaction: calcite, limestone, precipitated calcium carbonate, cement, gypsum, and dolomite; (2) those causing a proliferative reaction (the silicosis producers): quartz or sand, diatomite, tripoli, and various combinations of natural dusts high ST0853578 EFFECTS OF DUSTS AND FUMES UPON MAN 49 in quartz; (3) those causing an inert reaction: alundum (AljOi) and silicon carbide (SiC), anthracite and bituminous coal, bentonite and kaolin, fuller's earth, feldspar, mica, talc, soap stone, shale, traprock, pyrophyllite, sericite, volcanic and pre cipitator ash (from power plants), hematite (as jeweler's rouge), and asbestos. As the result of this work the Bureau approved the use of the dusts in the first class--those causing "an absorptive reaction." It is interesting to note, after some 20 years, that their ranking of dusts as potential silicosis producers has not been changed by any of the more elaborate methods since devised or by epi demiologic studies. Up to about 1950 the harmfulness of the potential silicosis pro ducers was more or less rated in proportion to the free quartz of fine particle size. Sayers' three classes were sound at the time he suggested them. Now we would probably accept the first two, namely, the absorptive and the proliferative classes, but the third still is being explored. It is no longer enough to say that mineral dust is safe to use simply because it is low in quartz. Aluminum Therapy. Denny and Robson (111) at the McIn tyre Mine in Schumacher, Ontario, noted in 1936 that "the pres ence of small amounts of metallic aluminium almost completely prevented siliceous material from passing into solution." Later they and Irwin (111) showed a relationship between reduction of solubility of free silica by aluminum powder and a decrease in the occurrence of silicotic lesions. They then "tried to prevent silicosis in quartz-dusted animals by giving them daily inhala tion of powdered aluminium" and "were completely successful." The quotations are from King (251) who gives the best appraisal of this interesting episode that we have seen. Denny and Robson's animal experiments were checked and confirmed by Gardner (179), Fig. 19, at Saranac Lake, by King (251) in London, and by Policard (337) in France. Gardner had often referred to "protector dusts" and suggested that hydrated alumina would work better than metallic aluminum powder. Also it is easier to disperse in air, presents no explosion problem, and does not require fresh grinding as it is stable. It was natural to test the efficacy of aluminum on patients with silicosis, especially men with respiratory embarrassment but without tuberculosis. In 1944 Crombie et al. (85) reported ST0853579 50 industrial dust improvement of about half of a group of 34 patients with silicosis who were treated by being given freshly ground aluminum dust to inhale. Denny and Robson patented the treatment and assigned it to the McIntyre Foundation which then granted licenses to properly qualified physicians. If the treatment was to be used at a factory or mine, the Foundation required proof that modern dust control and medical control were enforced. In 1948 Berry (39) at Denver reported a careful study of 35 patients with silicosis, without tuberculosis, but with definite respiratory embarrassment. Twenty-six breathed aluminum hydroxide at concentrations of 300 million particles per cubic foot by impinger counts and nine breathed filtered air, none of them knowing which men were the controls. Concentrations were obtained by a carefully adjusted modification of the dusting equipment used at the U.S. Bureau of Mines for testing respira tors (see Chap. 17). Berry concluded that "in the aluminum treated group, no objective changes were observed which could be convincingly attributed to the metallic therapy," and that is about where the matter stands today (10). Colloidal Silica. In 1937 Bruce (65) of Stockholm described cases of silicosis among men making silicon alloys. The actual numbers involved were very small, and he could not decide whether exposures resulted from dust generated in handling the quartz used as raw material or from the silica fumes which resulted from the spontaneous burning of vaporized silicon. The fume escaped from "the furnace in the form of an immense, dense, spreading, white jet of smoke." The particles were examined by Sundius, state geologist, who found them to be mostly finely divided powder of silica with some quartz grains. Under the microscope they showed abundant floes with discrete particles^ presumably in the pigment range of size. We do not question Sundius' report, but we are confident that present-day methods of pigment microscopy, using the electron microscope, would place the particle size of this fume in the colloidal range. In 1947 Shaver find Riddell (373) in Canada reported cases of severe pulmonary disability, new to industry, which "disclosed a peculiar type of lung shadowing, together with a pneumothorax which had developed spontaneously." Shaver's first patient was seen in February, 1942. The men affected were working around electric furnaces making ST 0853580 EFFECTS OF DUSTS AND FUMES UPON MAN 51 a synthetic abrasive comparable to the natural mineral corundum, AljOj. In the trade it is called both alundum and aloxite. The raw materials were bauxite, AltOj-2HiO; coke; and iron. Silica was not added, as such, but was present in the bauxite in trifling amounts. The furnaces had a steel shell, and cooling water was sprayed around the upper edge. Within the melt, temperatures were about 2035C. When fusion had been completed, the furnace was cooled, the wall removed, and the pig weighing about 8 tons broken up; the pieces were then sorted and crushed for shipment. The process was fairly old as such things go, and no trouble had been experienced up to 1942. Even in retrospect we doubt if Shaver's cases should have been predicted. In any event they were not. In writing up this incident, Jephcott el al. (244) reported: "A faster rate of production was obtained in some plants during the war," and "This change caused a marked increase in the amount of fume given off." Jephcott found the fume to be a mixture of which the significant constituents were 35 to 64 per cent alumina and 16 to 54 per cent silica. In Germany, Gartner (181) reported severe reactions, with some tuberculosis, among Korunsckmelzems, caused by overload ing the industrial capacity of their plants. We pointed out that the raw material in Shaver's cases had a low silica content but that the fume evolved contained high percentages of alumina and silica. Gartner (181) suggests that the German troubles were essentially the same as those reported by Shaver and Riddell and that mullite, 3Al20j-2Si02) identified in both Canadian and German furnace fumes, caused the disabilities. It is unlikely that the etiology of this unique disease, known as Shaver's disease, will be worked out in a systematic fashion. As soon as it was suspected that the capacities of the Canadian plants were overtaxed, steps were taken to remedy conditions and the exposure of the workmen was controlled. Animal work since then has not brought out anything conclusive, so we are informed, and no more human exposures are apt to occur. OTHER PNEUMOCONIOSES Silicates. Exposures to silicate dusts were common in industry long before modern methods of rock drilling, crushing, milling, i ST085358I 52 INDUSTRIAL DUST 1 and conveying had been developed. Excepting only asbestos, the silicates together with limestone, gypsum, and coal had not this unpleasant legacy of involvement with tuberculosis at the time modem bulk handling of raw materials was becoming common place. It is our belief that our very modernization made some I processes, formerly handling silicates safely, somewhat risky. By 1950 this situation was generally recognized and now is being brought under control. In 1927 Badham (19) in Australia coined the word silicatosis to cover the pulmonary disabilities resulting from breathing the various silicate dusts (113). In 1933 McCord (307) reviewed the subject which was considered at each of the first four Saranac symposiums. The recent summary by Koelsch (251) shows clearly that the problem is recognized all over the industrial world. t We now have good laboratory or field studies of exposures to talc (115, 376, 372), mica and pegmatite (116), pyrophyllite (136), various clays (256), fuller's earth (310, 69), pumice (394), sillimanite (182,250), mullite (251), olivine (257), and others. The t list is sure to be enlarged. We doubt that any responsible per son, in this age, would condone heavy dust exposures, especially chronic exposures, to any silicates on the doubtful premise that they have not been shown to produce the nodules of classical silicosis and have 'not the bad name of involvement with tuberculosis. Mineral and Glass Wool. Mineral wool is made by blowing molten slag from the spouts of furnaces adapted from small foundry cupolas. Glass can be made into fibers similarly. Later developments of Fiberglas are beautifully mechanized and bear little resemblance to the early process. Both mineral wool and glass wool are artificial silicates the composition of which is controlled by the ingredients of the melt. Fiberglas is now sold in spooled thread as yarn from which fabrics can be made by adaptations of standard textile processes. Either type of fiber can be made up in batts of convenient size to handle, or it can be collected as fluffy wool and blown in between the walls of houses for insulation. Fiberglas. for some time, has been an important insulating material both thermal and electrical. Men handling it for the first time complain of skin irritation from the tiny spicules, especially around their ST0853582 EFFECTS OF DUSTS AND FUMES UPON MAN 53 --11-- and cuffa. They have asked whether it would not be irritating to the lungs if breathed. Animal studies (146, 174) and periodic examinations of workers (121) indicate that there is nodanger at all of pulmonary damage from either mineral wool or FZbergLaa. Carbon Dusts. As long ago as 1837 Stratton (405) wrote: Ola examining the bodies of elderly persons we find the lungs always of a dark color. Sometimes the color is much deeper in various parts of the lungs which then are as black as charcoal; at other times the whole lungs are uniformly of a dark color. The first appearance is eoaddered healthy, the second receives the name of melanosis, and the third is what has been called the black lung of coal miners and may more shortly be defined as anthracosis. In 1928 Collis and Gilchrist (81) had reported upon the health of coal trimmers, men who loaded coal into barges at Cardiff and had no mining experience. Collis noted no significant disability hunsf, as he thought, there was not enough silica in the coal. In their monograph on the lungs of coal and other miners in Australia, Badham and Taylor (20) in 1938 wrote: "We find osuselves by no means in agreement with the opinion that coal miners' lung is only the product of free silica.--That coal-dust mad not the country rock is to blame is shown not only by the nmlyais of affected lungs and coal seams, but hy the fact that we have seen individuals affected with pulmonary fibrosis who did not work underground but only on the screens." Cummins and Sladden (90) in 1930 examined many coal Baers' lungB, pathologically, histologically, and chemically and then correlated these studies with case histories. Commenting on Haldane and Mavrogordato's opinion on the relative harmlessaess of carbon (because it is more easily removed from the lungs than is quartz), they state that both coal dust and silica in large amounts may be present in the lungs of coal miners but that "cool is only retained in large amounts when there is a really high silica content, and there seems no doubt that in general the absorption of silica favours a retention of coal dust when this is freely available as in coal-mining or coal-trimming conditions." The whole question of pulmonary disease among British miners and coal handlers was reopened in 1937 by the Medical Research Council's Committee on Industrial Pulmonary Diseases.  ! . 1 S T 08 53583 54 INDUSTRIAL DUST A full account of the resulting progress with excellent bibliography is given by Fletcher and Gough (159). Widespread pulmonary disease was found, more in anthracite than in bituminous coal handling. Recently Ray et al. (343, 344) reported convincingly that either pure coal or graphite, with only 2 -.per cent quartz contamination, could initiate typical silicotic fibrosis. In com paring the pathogenicity of different coals Fletcher and Gough say that it "does not appear to be directly related to their free silica content, but may depend upon some property associated with the `rank' (i.e. volatile matter) of the coal." Their anthra cites with 5 per cent volatile matter were more potent than the bituminous coal with 30 per cent volatile matter. In the United States in 1949 there were 76,000 anthracite and 409,000 bituminous miners (162). There have been no studies on the health of the whole industry, but there have been good studies of representative samples. In 1935 Sayers et al. (365) published a report of their field study with physical examinations, dust determinations, and petrographic analyses of conditions under which 2711 miners worked. They reported an incidence of 22.7 per cent anthracosilicosis. In 1941 Flinn et al. (160) made a similar study among bituminous miners in Utah and reported the occurrence of 3.2 per cent anthracosilicosis among 545 miners. It is more than doubtful that one could correctly extrapolate this last figure to cover our soft-coal miners in other parts of the country, but the consensus indicates that a figure of less than 2 per cent anthracosilicosis is about right, as of 1951. The coal mines of Britain are probably more vital to the national economy than is the case in the United States. In both countries the industry has had some rude economic and social jolts in which the workers' health is by no means the main issue (238). Whether one calls coal miners' pulmonary dis ability pneumoconiosis or anthracosilicosis seems to us unimpor tant compared with the proved facts--with dust control and a modem medical program the industry is not an unhealthy one. Beryllium. The pulmonary manifestations of beryllium poi soning, or berylliosis, occupy a large space in the industrial toxicological literature of the present era. This metal is used metallurgically in small amounts as an alloy with copper, alu minum, and magnesium and in steels. It has had considerable usage in phosphors (as a complex silicate of zinc) for fluorescent ST0853584 EFFECTS OF DUSTS AND FUMES UPON MAN 55 lamps, but so much trouble resulted from poisoning that this application has been discontinued.1 The most important use today is as the pure metal in atomic-energy installations. The medical aspects of pulmonary beryllium poisoning place it logically with the pneumoconioses. Symptoms can be caused, apparently, by inhaling fractions of a milligram per cubic meter. This ranks its theoretical toxicity with the lethal war gases, but such is by no means borne out generally in practice. Estimates of toxicity either on men or on animals vary greatly, and one must conclude, as suggested by Sterner and Eisenbud (401), that some other process (as yet unidentified) enters the picture to account for the great differences in reactions which have been noted and the puzzling epidemiology. Beryllium poisoning in its various forms, acute and chronic, has been described in detail by Hamilton and Hardy (203). Acute poisoning is generally less of a problem than the chronic type, which takes months or even years to become apparent. The respiratory distress of the severe chronic cases is extreme, the chest x-rays are characteristic, and the prognosis generally is poor. Once the disease was recognized, much of the risk was elimi nated by process control and careful medical supervision, but cases are still (1954) cropping up. Sterner and Eisenbud (401) state that more than 100 cases of pulmonary granulomatosis (the chronic type of poisoning) and more than 200 of acute pneu monitis have occurred during the past several years among individuals exposed to beryllium and its compounds. Eisenbud el al. (138) reported 11 possible cases of beryllium poisoning among persons living in the neighborhood of a beryl lium-producing plant. Concentrations which might have been breathed were estimated at 0.01 to 0.1 microgram/cu m. While Eisenbud points out that there is no justification for applying these data for estimating hazards of exposed workers, a manu facturer whose plant handles and processes beryllium in any amount should be aware of these figures. The degree of process control which they imply is most exacting. * 1 By agreement among U.S. lamp manufacturers, production of Be phos phors was discontinued June 30, 19-19. ST0353585 BIBLIOGRAPHY 1. Abramson, H. 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Med., 2: 116 (1867). il ST08536I 0 AUTHOR INDEX Abramson, ref. 1, asthma and resist ance to breathing, 340 Adley, ref. 147, lead arsenate, 66 Agricola, 40-41 Aitken, dust counter, 125-126 thermal precipitation, 21, 160 Alden, exhaust hoods, 257 ref. 4, pipe layout, 262 Alexander, ref. 260, x-ray diffrac tion, 211 Allen, ref. 5, settling of dust, 6 Allsop, ref. 6, rock dusting, 101 American Conference of Govern mental Industrial Hygienists (ACGIH), permissible concen trations, 106-112 ref. 8, pressure losses, 265 ventilation code of, 257, 202 American Foundrymcn's Associa tion, industrial hygiene code of, 257 American Medical Association, Council on Industrial Health, ref. 10, aluminum therapy, 50 American Public Health Associa tion, definition of silicosis, 35 ref. 12, lead poisoning report, 61 American Society of Mechanical Engineers, Power Test Code for Dust Separators, 167, 282 Anderson, E., 285-286, 289 Anderson, E. (and Schmidt), elec trical precipitators, 325 Anderson, F. P., ref. 16, testing effluent of air filters, 313 Armitage, 138 Armspach, ref. 16, testing effluent of air filters, 313 Armstrong, ref. 117, lead battery manufacture, 61 Army Chemical Corps, breather pump for mask testing, 340 Aylward, refs. 104, 105, impinge ment, 132-135, 138, 144-151 Badham, permissible dustiness, 108 silicatosis, 52 Badham and Taylor, coal miners' lung, 53 lung ash, 105 Baetjcr and Vintinner, 56 Baliff, ref. 399, unit collectors and recirculation, 282 Ballard el al., 211 Barnes and Penney, 159, 330 Barnett, ref. 25, silicosis and asbes- tosis in Britain, 39, 46 Baron el al., 279 Barreto et al., ref 28, masks and respirators, 304-305, 336 Barrett et al., cadmium oxide fume, 64 Batchelor el al., 72 Battista et al., ref. 30, hoods for electroplating, 251 Baum, ref. 59, microprojector for impinger dust counts, 151 Baumberger, 9Cf Beadle, konimeter vs. thermal pre cipitator in sampling mine air, 139, 163 review of dust sampling methods in South Africa, 118 ST085361 I 374 INDUSTRIAL DUST Bedford and Warner, 121 Bowler, ref. 233, respiratory cancer, Belden and Garber, galena workers, 66 61 Boyd, ref. 47, sugar-tube dust sam ref. 34, galena workers, 111 pling, South Africa, 126 Belknap, urinary lead, 61 Boyland et al., 89 Belt and Ferris, ref. 36, silica in Bracket (and Daniel), 189 lungs, 103 Brandt, dust-clciud apparatus, 275 Belt and King, intratracheal injec ref. 50, hoods for electroplating, tion of dust suspensions, 47 251-252 Bennett, ref. 146, effects of glass Industrial Health Engineering, wool and mineral wool, 53 book, 257, 336 Berly, cyclone efficiency, 293 Brandt and Steffy, ref. 51, effect of ref. 153, test suspensions for air hood shape, 263-264 cleaning, 275-276 Bridge, 39 Berman (and Larsen), 208-210 Brinton, ref. 160, anthracosilicosis, Berm and Drinker, P., 343 54 Berry, 50 Brinton et al., ref. 53, chromates, 64 Beyer (and Hurlbut), 85 Briscoe (and Mathews), 127, 201 Billings, ref. 153, cyclone efficiency, British Textile Commission report, 293 75 ref. 153, test suspensions for air Britten, ref. 358, granite study, 81, cleaning, 275-276 115 Billington, ref. 40, use of resin- ref. 365, permissible coal dust, 109 impregnated filters, 318 permissible granite dust, 108 Black (and Landahl), 89 ref. 359, permissible lead dust, 111 Blaisdcll (Crombie el al.), 49 ref. 365, time-dustiness studies of Blodgett, ref. 271, trajectories of coal mining, 54, 116 particles, 19 '' Britton and Head, 38 4 Bloomfield, ref. 412, cement workers, 56, 110 Brooks, ref. 416, laboratory-type Cottrell precipitator, 330 ref. 414, particle size and Tyndall ref. 43, chromic acid mist, 64 beam, 26-27 granite dust concentrations in Brown, A. S., ref. 450, lead poison practice, 81, 115 ing, 61 ref. 365, permissible coal dust, 109 Brown, C. E., ref. 369, A-C precipi ref. 358, permissible granite dust, tator, 159 108 detecting leakage of respirators, ref. 359, permissible lead dust, 111 340-341 size of dust particles, 79 determining dust by filter paper ref. 365, time-dustiness studies of method, 128 coal mining, 54, 116 dust dispersing apparatus, 275 weighting dust exposures, 115 dust retention by man, 90 Bloomfield el al., urinary silica, 78 flocculation and settling, 23-24 Blum, ref. 43, chromic acid mist, 64 ref. 60, visibility of smallest par Blumgart, lead absorption by nose, ticles in dust counting, 154 60 Brown, C. E., et al., ref. 59, micro retention of ethyl iodide, 92 projector for impinger dust Bowditch, 255 counts, 151 ST08536I 2 4VTH0R INDEX 375 Brown, C. E., and Schrenk, ref. 61, rock drilling, 217 Brown, C. E., and Yant, 164, 166 Brown, E. W., ref. 63, cutting lead- painted steel, 61 Brown, H. R., ref. 211, explosibility of metal powders, 102 Brown, J. H., el al., ref. 64, 92-94 Brace, 50 Brumfiei, ref. 177, cement dust, 56, 110 Brunauer (and Emmett), 189 Brundage, ref. 412, cement workers, 56 ref. 365, permissible coal dust con centration, 109 ref. 365, time-dustiness studies of coal mining, 54, 116 Bubar, 166 Buchan, ref. 67, selenium, 66 BuckeLI, ref. 233, respiratory cancer, 66 Bulmer el al., ref. 68, cadmium oxide fumes, 64 Burke, ref. 193, rock drilling, 217 Campbell and Gloyne, ref. 69, ful ler's earth, 52 Card, ref. 27, cadmium oxide fume, 64 Carman, ref. 70, specific surface of powders, 189 Carpenter, ref. 136, pyrophyllite, .2 Cassel and Schultz, 189 Castberg, ref. 322, lead arsenate, 66 Castle el al., G2 Cawood, 21 Charleston, ref. 415, bacterial filters, 320 Chirico, 237, 239, 243 Choate, ref. 216, size analyses, 193 Clark, G. I., and Reynolds, 211 Clark, \V. I., 77 Clayton, ref. 371, Donora pollution report, 1 Clelland el al., 78 Clinton, 66 Collings el al., 69 Collis, importance of free silica, 76 Milroy Lectures, 76 Collis and Gilchrist, 53 Collis and Goadby, ref. 86, iron miners, 57 Cook, ref. 64, dust retention, 92 Cooper, ref. 210, explosibility of cornstarch, 101 Cottrell, 325 Couchman and Schulze, 153 Craw, 57 Crombie el al., 49 Cronin, 57 Crowley, ref. 399, unit collectors and recirculation, 282 Cumming, ref. 76, solubility of silica, 78 Cummings, air masks in mining operations, 345 dust measuring technic, 183, 185 permissible quartz dust, 108 Cummings (and Gardner), ref. 176, 35, 77, 82 Cummins, 41 Cummins and Sladden, 53, 104 Cunningham, correction, 8, 22 Cutter et al., 59 DallaValle, aerodynamics of exhaust hoods, 247-252 Exhaust Hoods, book, 257 ref. 161, manganese, 64, 110 ref. 116, mica and pegmatite, 52 Micromeritrics, book, 2 ref. 115, talc, 52 ref. 365, time-dustiness studies of coal mining, 54, 109, 116 transporting velocities, 262 weighting dust exposures, 115 DallaValle and*Hatch, ref. 97, hood design, 246-252 Daniel and Bracket, 189 Dautrebande, ref. 99, errors in microscopy, 187 Davenport (and Harrington), 38 ST0853613 376 INDUSTRIAL DUST Davies, C. N., air filtration, 318, 336-337 centrifugation of particles, 17 diffusion in air filtration, 297 fibrous filters, 318, 336 impingement, 18 nasal filtration, 89 ref. 243, overlapping of dust par ticles, 138 particle size and retention, 92 particles in electric field, 20 resin-impregnated filters, 318, 337 thermal precipitation, 21 Davies, C. N., et al., refs. 104, 105, impingement, 132-135, 138, 144-151 konimeter efficiency, 138 Davies, G., ref. 360, dust respirator, 337 Dean, ref. 106, Trail smelter, 278 Decker el al., 320 Delahant, ref. 179, aluminum ther apy, 49 DeMeio, ref. 108, tellurium breath, 67 Dempster and Ritchie, 78 Dennis, ref. 340, air flow induced by falling materials, 235 ref. 153, test suspensions for air cleaning, 275-276 Dennis el al., ref. 110, air filter tests, 313-314 ref. 110, wet collector tests, 325 327 Denny et al., 49-50 Doig, ref. 112, welders, 58 Dolan, ref. 258, lung ash, 105 Dolan and King, 78 Dolin, ref. 225, dust in foundries, 227 Dooley, ref. 161, manganese, 64, 110 Dougherty, ref. 415, bacterial filters, 320 # ref. 417, flocculation of smoke, 25 Dreessen, ref. 322, lead arsenate, 66 marble dust, 110 ref. 116, mica and pegmatite, 52 ref. 365, permissible coal dust con centration, 54, 109 Dreessen, silicate dusts, 52 ref. 115, talc, 52 ref. 365, time-dustiness studies of coal mining, 116 Dreessen et at., ref. 117, lead battery industry, 61, Drinker, C. K. (Castle el al.), 62 Drinker, C. K., and Field, 35 Drinker, C. K. (Hegsted et al.), 72 Drinker, C. K., and Shaw, 60 " Drinker, K. R., ref. 29, health of zinc workers, 72 Drinker, K. R. (Castle et al.), 62 Drinker, P., ref. 125, acquired resist ance to metal-fume fever, 70 ref. 169, aerosols, size of, 81 air cleaning, costs of, 282 CO-free compressed air for masks, 343 dust concentrations, 98-99 ref. 153, efficiency of cyclones, 293 ref. 224, efficiency of impinger, 148, 151 ref. 121, glass wool, 53 ref. 169, high-efficiency filters, 318 ref. 122, lead burning, 61 ref. 314, lead mist, 61 ref. 28, masks and respirators, 304-305, 336 ref. 406, metal-fume fever, 70 nasal filtration, 89 phagocytosed dusts, 34 phagocytosed dusts, size of, 191 quartz, potency of various sized particles, 82 ref. 153, test suspensions for air cleaning, 275-276 ref. 121, welding galvanized iron, 72 Drinker, P., et al., A-C precipitator, 157, 332 refs. 127, 128, dust and fume reten tion, 90, 92, 106, 111 ref. 130, magnesium oxide, 111 turbulence and stability of sus pensions, 25 refs. 131, 132, welding fumes, 72, 111 ST08536IU AUTHOR INDEX 377 Drinker, P., and Hatch, dust respi rators, 336 Druett, ref. 233, respiratory cancer, 66 Duckering (and Legge), 110 Dunn, counting cell, 153 Durkan, ref. 433, asbestos dust, 45 ref. 177, cement dust, 56, 110 determination of free silica, 204r' 208 Dustan, ref. 138, berylliosis, 55 Dworski, ref. 199, aluminum ther apy, 49 ref. 178, marble dust, 56, 110 Easom el al., pyrophyllite, 52 Edwards, ref. 322, lead arsenate, 66 ref. 117, lead battery manufac ture, 61 ref. 116, mica and pegmatite, 52 ref. 115, talc, 52 Ege, ref. 379, color standards for aerosol determinations, 128 ref. 377, 378, fume samplers, 129 Eickhoff, ref. 250, sillimanite, 52 Einstein, 15-16 Eisenbud, ref. 449, permissible mer cury concentration, 112 Eisenbud el al., berylliosis, 55 Eisenbud and Harris, 277-280 Eisenbud and Sterner, 55 Elkins, 60-61 Ellman, 45-48 Elrod (and Figley), ref. 150, 73 Emmett and Brunaucr, 189 Knzer and Sander, 58-59 Epstein, 192 Evans, 63 Factory Insurance Association, ref. 144, dust explosions, 101 Fairhall, ref. 322, lead arsenate, 66 ref. 146, rock wool, 53 Fairhall and Sayers, ref. 145, lead in serum, 111 Faller, ref. 91, tin oxide, 59 Fanning, ref. 233, respiratory can cer, 66 Farner el al., 66 Faulds (and Stewart), 57 Faust, G. T., 212 Faust, R. C., ref. 435, thermal pre cipitator, 161, 167, 186-187 Fehnel, ref. 273, asbestos dust, 45 ref. 305, foundry dust, 38, 58, 203 ref. 29, health of zinc workers, 72 Feicht, ref. 287, midget impinger, 150 ref. 60, visibility of smallest par ticles in dust counting, 154 Feiner, ref. 399, unit collectors and recirculation, 282 Fenn, 35 Ferris, ref. 36, silica in lungs, 103 Field (and Drinker, C. K.), 35 Fieldner, ref. 366, lead fume reten tion, 90 Figley and Elrod, ref. 150, castor- bean dust, 73 Findeison, 92 Finlay, ref. 244, alumina abrasives, 51 Finn, ref. 125, acquired resistance to metal-fume fever, 70 ref. 128, dust retention, 90 ref. 127, fume retention, 92 ref. 28, masks and respirators, 304-305, 336 ref. 130, magnesium oxide, 111 ref. 127, permissible fume concen tration, 106, 111 ref. 127, permissible zinc oxide, 106 Finn (Drinker, P., et al.), 157, 332 First, ref. 169, aerosols, particle size of, 81 air cleaning, costs of, 282 ref. 110, airfilter tests, 313-314 cyclone design and operation, 290 294 ref. 153, cyclone tests, 293 ref. 380, edge and variable com pression filters, 313, 315 ref. 169, high-efficicncy filters, 318 ST08536 15 378 INDUSTRIAL DUST First, mounting dusts for micros copy, 171 ref. 110, wet collector tests, 325 327 First el al,, ref. 154, performance tests of two-stage precipitators, 330-332 test suspensions for air cleaning, 275-276 First and Drinker, various dust con centrations, 98-99 First (and Silverman), edge and var iable compression filters, 313, 315 First and Silverman, ref. 155, mem brane and molecular filters, 129-132 Fisher, ref. 158, silicosis, discussion by \V. R. Jones, 85 Fitchet (Drinker, P., el al.), 157, 332 Fleming, ref. 78, fluorides, 69 Fletcher, ref. 238, British coni min ing and silicosis, 54 Fletcher and Gough, 54 Flinn el al., anthracosilicosis, 54 ref. 161, manganese poisoning, 64, 110 " Forbes, ref. 162, miners employed in U.S., 97 rock dusting of coal mines, 101 Foster and Schrenk, 174, 208 Fowweathcr, 105 Frank, 7, 9 Frankish, ref. 68, cadmium oxide fumes, 64 Franklin, ref. 382, shattering of par ticles by impingcr, 152 (See also Silverman and Franklin) Franks, ref. 160, anthracosilicosis, 54 Frasier, ref. 53, chromates, 64 Freundlich, from Gibbs, ref. 183, 297 Frcvert (and TrostelT! 126 Friberg, ref. 168, cadmium poison ing, 65 Friedlander, ref. 169, aerosols, size of particles, 81 ref. 169, air cleaning, cost of, 282 air filters of high efficiency, 318 Friedlander, ref. 153, cyclones, 291 293 ref. 153, test suspensions, 275-276 Fulton, ref. 181, manganese, 64 \ } Gaddum, ref. 48, nasal filtration, 89 Gafafer, ref. 371, Donora pollution report, 1 . Garber (and Belden), 61, 111 ' Gardner, artificial abrasives, 77 asbestosis, 45 employability of silicotics, 43 ref. 172, etiology of pneumo coniosis, 47 ref. 174, glass wool, 53 gypsum, 57 protector dusts, 49 silicosis and tuberculosis, 36 Gardner et al., aluminum therapy, 48-49 cement dust, 56, 110 Gardner and Cummings, ref. 176, potency of quartz particles, 35, 77, 82 Gardner and Dworski, marble dust, 56, 110 Gardner and Redlin, lung ash, 105 Gartner, 51 refs. 181, 251, mullite, 51-52 Gartner and van Marwyck, silli- manitc, 52 Gcile, ref. 107, bacterial filters, 320 Gerhard, ref. 26, stack emission of aerosols, 279 Gerke, ref. 414, Tyndall beam and particle size, 26-27 Gerke (and Wells, P. V.), 188 Gfrorcr, ref. 283, dust retention, 89 Gibbs, W. E., Clouds and Smokes, book, 2, 16, 325 Gilchrist, J. C. (and Collis), 53 Gilchrist, M.', ref. 257, olivine, 52 Gilligan, ref. 46, ethyl iodide inhala tion, 92 Gleason, ref. 409, cutting lead- painted steel, 61 Glick, ref. 107, bacterial filters, 320 } ST08536 I 6 `AUTHOR INDEX 379 Gloyne, ref. 69, fuller's earth, 52 Gloyne and Merewether, 45 Gloyne (and Wood), asbestosia, 45 Goadby, refs. 86, 186, health of iron miners, 57 inhaling vs. swallowing lead dust, 60, 110 Godbert and Greenwald, 101 Goldman, ref. 44, urinary silica, 78 Goldschmidt, ref. 257, olivine, 52 Gough (and Fletcher), 54 Goyer, ref. 267, air filtration, 297 Graham, ref. 391, particle sire for rock dusting, 101 Gray, effect of water sprays, 26 Green, H., 171, 190 ref. 190, shape factors, 199 Green, H. L., ref. 360, dust respi rator, 337 ref. 191, microscopy of dusts, 124 126, 177 Green, H. L., and Watson, 160, 182 Greenburg, ref. 443, filtering ve locity and dust loading, 307-309 ref. 194, health of foundrymen, 58 ref. 30, hoods for electroplating, 251 ref. 196, sandblasting, 216 ref. 376, talc, 52 ref. 454, wet grinding, 219 Greenburg el al., ref. 193, rook drill ing, 217 Greenburg and Smith, G. W., im- pinger, 147 . Greenwald, ref. 197, salt in rock dusting, 101 Greenwald (and Godbert), 101 Gregorius (and .\fachlc), 64 Grucn, ref. 267, air filtration, 297 Guckeref al., ref. 2 15, high-efficiency filters, 276 Guernsey, ref. 415, bacterial filters, 320* Guitard, ref. 308, electrical precipi tation, 325 Gurney, Williams, C. R., and Meigs, 143 Gye and Kettle, 77 Haggard (and Henderson), 32, 106 Haldane, effects of carbon dust, 53 Halley, ref. 200, dust counting, 153 Hama, ref. 314, lead mist, 61 Hamilton, galena miners' freedom from lead poisoning, 61 inhaling lead dust vs. swallowing, 59 Hamilton and Hardy, beryllium poi soning, 55 lead poisoning, 60 manganese poisoning, 63 radioactive dusts, 63 vanadium, 68 Hamlin, ref. 204, health of foundry- men, 58 Hamlin and Weber, urinary lead, 61 Hansen, 318, 337 Hardy (see Hamilton and Hardy) Harrington, effect of water blasts, 26 Harrington and Davenport, silicosis, review, 38 Harris, W. B., ref. 138, berylliosis, 55 ref. 208, dust control in tunneling, 218 ref. 193, rock drilling, 217 Harris, W. B. .(and Eisenbud), air pollution surveys, 277-280 Harris, W. J., ref. 435, thermal pre cipitator, 161, 167, 186-187 Harrison, refs. 343, 344, effects, of coal and graphite, 54 ref. 256, kaolin, 52 Hartmann, ref. 197, salt in rock dusting, 101 Hartmann el al., explosibility of cornstarch, 101 ref. 211, explosibility of metal powders, 102 Hartmann and Nagy, ref. 209, cx- plosibilityof plastics, 101 Hartwell, ref. 6, rock dusting, 101 Harvard Air Cleaning Laboratory, tests of air filters, 313-314 tests of cyclones, 293-294 tests of electric precipitators, 330 331 ST08536I 7 ^ 380 INDUSTRIAL DUST Harvard Air Cleaning Laboratory, Hemeon, splash of dust and ven teete of high-efficiency filters, 318 tilation needed, 245 319 ventilation and falling material, testa of wet collectors, 326-327 232 Hatch, ref. 215, capture velocities in ref. 228, wetting dust, 218-219 hood design, 256-259 Hemeon (and Haich), ref. 218, 93, ref. 221, dark-field counting, 155 164 dust respirators, 336 Henderson and Haggard, 32, 106 ref. 64, dust retention, 92 Henry (and Legge), ref. 280, 66 ref. 443, filtering velocity and dust Herman, ref. 414, Tyndall beam and loading, 307-309 particle size, 26-27 ref. 220, foundry dust, analyses of Herrmann (and Landahl), 92 sized fractions, 202-203 Hersey, J. H., Jr., 311 ref. 97, hood design, 246-252 Higgins et al., 80 ref. 30, hoods for electroplating, permissible dustiness, 108 251 Hill, A. B., et al., 66 ref. 214, low-velocity exhaust sys Hill, A. S. G., ref. 360, dust respira tems, 268 tor, 337 ref. 213, particle size, statistical Hill, George R., 277 analysis of, 197-198 Hoffman, dusty trades, 96, 215 ref. 193, rock drilling, 217 Hohfold, 325 ref. 216, size analyses of fine par Holden el al., ref. 237, soluble filter ticles, 193 dust sampler, 127, 201 Hatch et al., ref. 225, dust in found ries, 227 ref. 224, impinger efficiency, 148, 151 " Hatch and Hemeon, ref. 218, 93, 164 Hatch and Kindsvatter, test sus pensions of fine dust, 83, 276 Hatch and Pool, light- and dark- field microscopy, 80 Hatch and Walpole, refs. 222, 223, measuring air displacement, 237-246 Hazen's log-probability paper, ref. 226, 193 Hoover, Herbert C., and Hoover, Lou Henry (Agricola), 40-41 Howart, ref. 197, salt in rock dust ing, 101 Hugh-Joncs, ref. 238, silicosis in British coal mines, 54 Humphries, ref. 297, radioactive dusts, 62 Hurlbut and Beyer, 85, 86 Huron, ref. 419, bronchial asthma from maple trees, 74 Hyatt, ref. 237, soluble filter dust sampler, 127, 201 Head (and Britton), 38 Hegsted et al., 72 Heiman, ref. 371, Donora pollution report, 1 Hemeon, air flow imiuced by hot processes, 239-243 Plant and Process Ventilation, book, 232, 245, 257 ref. 230, sandblasting safely, 216 ref. 237, soluble filter dust sam Illinois Department of Public Health, ref. 429, health of foundrymen, 227 International Labour Office, ref. 240, pneumoconiosis, 35 ref. 241, removal of nonsiliccous matter from dust samples, 137 ref. 241, silicosis, 36, 219 pler, 127, 210 Irvine, 103, 107 ST08536I 8 AUTHOR INDEX 381 Irwin, D. A., ref. 27, cadmium oxide fumes, 64 Irwin, D. A- (Denny ei al.), 49-60 Irwin, J. O., A al., 133 Jacobson, ref. 210, explosibility of cornstarch, 101 Jephcott el al., 51 Jephcott (and Riddell), 37 Johnson, G. A., ref. 110, teste of air filters, 313-314 ref. 153, test suspensions for air cleaning, 275-276 ref. 110, testa of wet collectors, 325-327 Johnston, ref. 244, alumina abra sives, 51 Johnstone, H. F., Handbook on Aerosols, 2, 22, 276 stack discharge, 279 Jones, J. L., ref. 160, anthracosilicosis, 54 Jones, It. IL, ref. 365, permissible coal dust, 109 ref. 359, permissible lead dust, 111 ref. 365, time-dustiness studies of coal mining, 116 Jones, S., and Tidcswcll, 101 Jones, W. IL, ref. 158, discussion of Fisher's paper on silicosis, 85 minerals in silicotic lungs, 84-85 Joseph, 40, 103 Jotten, ref. 251, mullite, 52 ref. 250, sillimanite, 52 Kane, 282-283 Karr (and Vonvald), 46 Katz ei al., 336 Kehoe, lead poisoning, committee report, 61 Keppler, ref. 398, cadmium oxide fumes, 64 Kettle, subcutaneous injection of dust suspensions, 47 ref. 254, toxicity of colloidal silica, 77 . Kettle (and Gye), 77 Kindsvatter (and Hatch), 83, 276 King, ref. 251, aluminum therapy, 49 refs. 343, 344, coal and graphite, 54 ref. 37, intratracheal injection and silicosis, 47 ref. 258, lung ash, 104-105 pathogenicity of various free silicas, 78 King ei al., ref. 256, kaolin, 52 olivine, 52 King and Dolan, urinary silica, 78 Kinney, ref. 334, particle size, 190 Klug ei al., 211 - Knopf, 208 Knudsen, ref. 340, air flow induced by falling materials, 235 Kobrak, 336 Koelsch, silicates, 52 Kottler, 192-193, 196 Kotz6, konimeter, 135 particle size in air, 79 Kovcn, ref. 53, chromates, 64 Kron (Simon ei al.), 29-30 Kruger, ref. 267. air filtration, 297 Kuhn ei al., 304, 330 Kummcr, ref. 200, x-ray diffraction, 211 LaBcllc, 184 ref. 452, uranium oxide particles, 94 Ladenberg, 20 La Mer, 28 La Mer el al.. air filtration. 297 U Mer (and Wilson), aerosol reten tion by man. 92 T^ndahl and Black, nasal filtration. 89 fAmdahl and Herrmann. 92 Landis, 72 Laney, ref. 232, Joplin silicosis study, 80. 108 Langmuir, ref. 271. trajectories of particles, 19 I,anza, ref. 232, Joplin silicosis study, 80, 108 ST0853619. , 382 INDUSTRIAL DUST Lanza, Silicosis, book, 58 Lanza, McConnell, and Fehnel, 45 Lanza and Vane, ref. 274, silicosis in the U.8., 41-42, 96 Lapp, 268 Lapple, 282 Lapple and Sheppard, 5-6, 11-13 Larsen, E. P., and Berman, 208 210 Larsen, S., 235-236 Laskin, adhesive coating of dust particles for microscopy, ISO182 elutriation of dust particles, 183 189 selenium coating of dust particles, 174, 175 ref. 452, uranium oxide particles, 94 Lea, ref. 279, specific surface of powders, 189 Leacey, ref. 105, impingement, 132 135, 138, 144-151 Lee, G., ref. 383, valves for respira tors and masks, 341-342 ref. 384, velocity and resistance in various masks, 338-340 Lee, R. C., ref. 383, valves for respirators and masks, 341-342 Leggc, 60 Legge and Duckcring, 110 Leggc and Goadby, 00 Legge and Henry, 06 Lehmann, G., 89 Lehmann, K. B., el al., 89 Lidwell, 320 Lissman, cyclones, 289 separation factor, 17 Little, A. D., Inc., ref. 286. hightemperature filter. 318 Littlefield, ref. 287, midget impinger, 150 Lodge, 325 Lombard, ref. 395, arsenical cancer, 65 Lorenz. 63 Lundgrcn el al., 65 McConnell, ref. 305, asbestos dust, 45 ref. 366, lead fume retention, 90 McConnell and Fehnel, ref. 306, foundry dust, 38, 58, 203 McCord, autobiography, 215 silicates, 52 ! McCrae, 82, 103-104 McDonald, ref. 48, nasal filtration, 89 ... Machlc and Gregorius, 64 McKibben (Hegsted el al), 72 McLaughlin, ref. 112, welders, 58 McMahon, ref. 303, prevention of lead poisoning, 02 McNally, 104 McNally and Trostler, ref. 310, fuller's earth, 52 MacPherson (Crombie el al.), 49 Madison, ref. 292, pressure losses, 265 Martin, conveying velocities for various materials, 263 settling velocities, 4, 8 size and surface area of particles, 199 ref. 296, statistical diameters of particles, 179 Martland, 62 Mathews and Briscoe, 127, 201 Mavrogordato, accuracy in koni- metcr sampling, 119-120 effects of carbon dust, 53 intraperitoncal injection of dust suspensions, 48 potency of various size quartz particles, 82 ref. 299, silicosis and dust con centration, 107 May, K. R., cascade impactor, 144 impingement, 132-135 May, R., ref. 78, fluorides, 69 Mayers, 60 ref. 303, prevention of lead poison ing, 62 Medical Research Council (Britain), industrial pulmonary diseases, 53 1 ST 0853620 AUTHOR INDEX 383 Meigs (Gurney and Williams, C. R.), 143 Meiter, ref. 253, dust respirators, 336 Merewether, asbestosis, 45 ref. 312, sandblasting, 216 Merewether (and Gloyne), 45 Middleton, 219 Mie, 28 Miller, H. I., ref. 314, lead mist, 61 Miller, T. W., and Sayers, gypsum, 57 intraperitoneal test for potency of dusts, 48 ref. 315, selecting rock for dusting of coal mines, 100 Miners' Phthisis Medical Bureau, 107 Miners' Phthisis Prevention Com mittee, ref. 317, 217 Minot, 60 Moir, 84 Moir (and Watkins-Pitchford), 103 Moke, ref. 220, foundry dust, anal yses of sized fractions, 202-203 Moorman, ref. 107, bacterial filters, 320 Morse, ref. 320, arsine poisoning, 65 Moschella, ref. 153, cyclone effi ciency, 293 ref. 153, test suspensions for air cleaning, 275-276 Mullikan, ref. 414, Tyndall beam and particle size, 26-27 Nagelschmidt, ref. 109, 78 ref. 256, kaolin, 52 ref. 257, olivine, 52 Nagy, ref. 211, explosibility of metal powders, 102 ref. 209, explosibility of plastics, 101 Neal, ref. 161, manganese, 64, 110 Neal et al., 66 ref. 323, permissible mercury con centration, 112 Nelson, use of water sprays, 220 ref. 131, welding fumes, 72, 111 New York State, code on dustiness in rock drilling, 109, 217 ref. 326, code for foundries, 58 rules on recirculation, 313 ref. 328, safe practice in radium dial painting, 63 Newton, 5-8 Ney, ref. 64, dust retention, 92 Nicholson, ref. 360, dust respirator, 337 Nurse, ref. 279, specific surface of powders, 189 Nussbaum, refs. 349, 350, mill fever, 75 O'Neil, ref. 400, recirculation, 282, 313 Oshry, ref. 22, x-ray diffraction, 211 Owens, ref. 374, determining dusti ness by settlement, 124 ref. 329, dust in exhaled air, 89 jet dust counter, 140 Page, filter studies by, 296, 299-304 ref. 117, lead battery manufac ture, 61 ref. 132, welding fumes, 111 Patterson, H. S., (and Van Wijk), 92 Patterson, J. C., ref. 27, cadmium oxide fume, 64 Pearce, 337 Pendergrass, benign pneumoconio ses, 58-59 Pendergrass and Pryde, 59 Penney, ref. 333, two-stage precipi tator, 330 Penney (and Barnes), electrostatic dust sampler, 159, 330 Perina, ref. 393, artificial abrasives, 215 * ref. 399, unit collectors and recir culation, 2S2 Perott, ref. 334, particle size, 190 Perry, J. H., ref. 335, Chemical En gineers Handbook, 2, 19 ST 085362 I % 384 INDUSTRIAL DUST Perry, K., ref. 233, respiratory can cer, 66 Pierce, ref. 417, flocculation of smoke, 25 Pihl, ref. 449, permissible mercury concentration, 112 Platt el al., ref. 336, cotton textile report, 75 Plotkin, ref. 384, air velocity and re sistance in various masks, 338 340 Policard, 47 Pool, rof. 221, dark-field counting, 156 Pool (and Hatch), 80 Pope and Zacks, 38 Porter, ref. 398, cadmium oxide fumes, 64 Pratt, ref. 433, asbestos dust, 45 Princi, 65 Pring, filter cloths, 305-306 measuring air displacement, 236, 243 Pring el al., air flow induced by fall ing materials, 235-236 Pryde (and Pendergrass), 59 Rammlcr (and Rosin), 193 Ran* and Wong, 132-135 Ray, refs. 343, 344, effects of coal and graphite, 54 Rayleigh, 27-28 Raymond (Simon el al.), 28-30 Rcdlin (and Gardner), 105 Reece, bacterial filters, 320 Reinhart, ref. 322, lead arsenate, 66 ref. 117, lead battery industry, 61 ref. 161, manganese, 64, 110 Reynolds (and Clark, G. I.), 211 Rice, ref. 232, Joplin silicosis study, 80, 108 * ref. 340, rock dusting of coal mines, 100 Richtn6r, ref. 290, copper-arsenic smelting, Co Riddell, effect of gypsum, 57 Riddell and Jephcott, uncompli cated silicosis, 37 Riddell (and Shaver), 50-51 Riley, ref. 441, bacteria in air, 124 Ritchie, ref. 76, solubility of silica, 78 ' Ritchie (and Dempster), 78 Ritter and Nussbaum, refs. 349, 350, mill fever, 75 Robson (Denny el al.), 49-50 Rogers, ref. 257, olivine, 52 Rohmann, 20, 189 Roller, 169-171, 192 Rollet (and Policard), 49 Rosin and Rammler, 193 Ross and Sehl, ref. 356, free silica determination, 203, 209 Rossano, ref. 153, cyclone efficiency, 293 ref. 153, test suspensions for air cleaning, 275-276 Rothchild, ref. 450, lead poisoning, 61 Rothwcll, rof. 68, cadmium oxide fumes, 64 Ruf and Belknap, ref. 357, urinary lead, 61 Ruotolo, ref. 409, cutting lead- painted steel, 61 Russell, ref. 412, cement workers, 56, 110 Russell el al., ref. 358, granite study, 81, 115 permissible granite dust, 108 ref. 359, permissible lead dust, 111 Rycrson, ref. 416, laboratory-type Cottrell precipitator, 330 Sadd el al., 337 Saito, 89 Salazar and Silverman, 212 Sampson, ref. 177, cement dust, 56, 110 Sander, 58-59 Saranac Symposium on silicosis, ref. 363, 108 f I i. \I 1,1,11'iwgwwjWBpgps" I ST 0853622 AUTHOR INDEX 385 ref. 40, resin-impregnated atm, 318 Sauwat, ref. 364, water infusion in coal cutting, 218 Sawyen, ref. 384, air velocity and resistance in various masks, 338-340 Sayers, gypeum, 67 tef. 117, lead battery manufac ture, 61 ref. 146, lead in serum, 111 ref. 116, mica and pegmatite, 52 potency test of siliceous dusts, 48, 100 ref. 316, selecting dusts for rock dusting of coal mines, 48, 100 ref. 366, time-dustiness studies in coal mining, 116 ref. 44, urinary silica, 78 Sayers et al,, lead fume retendon, 90 permissible coal dust, 109 Schilling, ref. 367, byssinosis, 75 ref. 233, respiratory cancer, 66 Schmidt and Anderson, E., electrical preeipitators, 325 Sehrenk, ref. 369, A-C precipitator for dust sampling, 159 ref. 371, Donora pollution report, 1 ref. 59, microprojector for impinger dust counts, 151 ref. 165, microscopy and petrog raphy of dusts, 174, 208 ref. 287, midget impinger, 150 ref. 370, permissible dustiness, 107 ref. 369, respirator testing, 275 ref. 61, rock drilling, 217 ref. 22, x-ray diffraction, 211 Sshuitz (and Cassel), 189 Schnlz, potency of different sizes of quartz particles, 82 Schulz and Williams, ref. 372, talc, 52 Schulze, ref. 450, lead poisoning, 61 Schulze (and Couchman), 153 Schwartz, ref. 46, ethyliodide in halation, 92 Scott, J. K., ref. 452, uranium oxide particles, 94 Scott, N., ref. 147, lead arsenate, 66 Sehl, ref. 356, free silica determina tion, 203, 209 Seifert, ref. 160, anthracosilicosis, 54 Semmons, ref. 27, cadmium oxide fumes, 64 Setterlind, ref. 320, arsine poisoning, 65 Shaver and Riddell, 50-51 Shaw, L. A. (and Drinker, C. K.), 60 Shaw, N., and Owens, ref. 374, 124 Sheppard (and Lapple), 5-6, 11-13 Shillaber, 174 Siegal et cl., ref. 376, talc, 52 Siegel, ref. 194, health of foundry- men, 58 Siegel (and Smith), 52 Silverman, ref. 169, aerosols, size of particles, 81 ref. 169, air cleaning, cost of, 282 differential fusion for quartz de termination, 212 ref. 109, high-efficiency filters, 318 microprojection method, 154-155 ref. 155, molecular filter, 129-132 ref. 154, performance tests of two- stage precipitators, 330-332 ref. 153, test suspensions for air cleaning, 275-276 ref. 110, tests of air filters, 313-314 ref. 153, tests of cyclones, 291-293 ref. 110, tests of wet collectors, 325-327 Silverman et al., air velocity and resistance in various masks, 338-340 valves for respirators and masks, 341-342 Silverman andEgc, ref. 379, color standards for aerosol determina tions, 128 refs. 377, 378, fume samplers, 129 Silverman and First, edge and vari able compression filters, 313, 315 ST0853623 386 INDUSTRIAL DUST Silverman (and First), ref. 155, membrane and molecular filters, 129-132 Silverman and Franklin, mounting dusts for microscopy, 171 ref. 382, shattering of particles by impinger, 152 Silverman and Thomas, ref. 385, apparatus and hand pump for dust sampling, 128 Silverman and Valenzuela, ref. 386, fume sampler, 129 Silverman and Viles, ref. 387, high- volume sampler, 129, 201 Silverman and Williams, C. R., ref. 388, high-volume sampler, 129 Simon el al., 28-30 Sjoberg, 68 Sjostrand, ref. 290, copper-arsenic smelting, 65 Skinner, ref. 391, size particles for rock dusting, 101 Sladdcn, 103, 105 Sladdcn (and Cummins), 53, 104 Smith, A. R., ref. 194, health of foundrymen, 58 ref. 376, talc, 52 Smith, A. R., and Pcrina, ref. 393, artificial abrasives, 215 Smith, A. R., and Siegel, pumice. 52 Smith, F. R,, Jr., ref. 450, lead poisoning, 61 Smith, G. W., ref. 253, dust respira tors, 336 impinger, 147 Smyth, ref. 416, laboratory-type Cottrell precipitator, 330 ref. 414, Tyndall beam and par ticle size, 26-27 Snegireff, 65 Sosman, 78 Sparks. 45 Spolyor el al., ref. 398. cadmium oxide fumes, 64 Stantial, ref. 258. lung ash. 105 Steadman, ref. 138, berylliosis, 55 Steffy, ref. 51, effect of hood shape, 263-264 . Stern, ref. 399, unit collectors and recirculation, 282 Stern and O'Neil, ref. 400, recircu lation, 282, 313 Sterner and Eisenbud, 55 Stewart, asbestosis bodies, 45 lung ash, 105 Stewart and Faulds, 57 Stocklen (Cutter el al.), 59 Stokes, 6-9, 170 ' Stokinger, ref. 452, uranium oxide particles, 94-95 Stone, R. S., ref. 404, Manhattan Project, 63 Stone, W. R., ref. 440, bacteria in air, 320 Stratton, 53 Sturgis, ref. 406, metal-fume fever, 70 Stutz. ref. 407, scattering of light by small particles, 28-29 Sundius, 50 Sutton, 278-279 Swain, ref. 106, Trail smelter, 278 Sweany, ref. 419, bronchial asthma from maple trees, 74 Sylvester, ref. 452, uranium oxide particles, 94 Tabershaw el al.. ref. 409, cutting lead-painted steel, 61 Talvitic, 207 Taylor (and Badham), 53, 105 Tebbens el al., 82 Thomas, B. G. H., ref. 366, lead fume retention, 90 Thomas. T. R.. ref. 385, dust sam pling apparatus, 128 Thompson, ref. 358, granite study, 81, 115 ref. 358. permissible granite dust, 103 ref. 359, permissible lead dust. Ill Thompson el al., ref. 412, cement workers, 56 ST 085362U AUTHOR INDEX 387 Thomson, ref. 125, acquired resists ance to metal-fume fever, 70 refa. 127, 128, dust and fume re tention, 90, 92 ref. 130, magnesium oxide, 111 ref. 28, masks and respirators, 304-305, 330 ref. 406, metal-fume fever, 70 ref. 127, permissible fume concen tration, 106, 111 ref. 132, welding fumes, 111 ref. 29, zinc workers, 72 Thomson (Drinker, P.t el al.), A-C precipitator, 157, 332 Tideswell (and Jones, S.), 101 Titus, 56 Tolman, ref. 417, flocculation of smokes, 25 Tolman el al., bacterial filters, 320 laboratory-type Cottrell precipi tator, 330 Tyndall beam and particle size, 26-27 Tourangeau and Drinker, P., 89 Towey et al., 74 Trice, ref. 136, pyrophyllite, 52 Trostel and Frcvert, 126 Trostler, ref. 310, fuller's earth, 52 Tyndall, 89 U.S. Bureau of Mines, ref. 422, allaying dust in mining, 218, 220 dust-feed devices for filter testing, 275 ref. 331, schedules for respiratory protective equipment, 337 U.S. Bureau of Standards, ref. 428, Handbook on Radium Dial Painting, 63 U.S. Public Health Service, ref. 429, health of foundrymen, 227 University of Birmingham, Mining Research Report, 85 Urban, ref. 314, lead mist, 61 Urbano. ref. 399, unit collectors and recirculation, 282 Valenzuela, ref. 386, fume sampler, 129 Vane (and Lanza), 41-42, 96 van Marwyck, ref. 182, sillimanite, 52 Van Siclen, 96 Van Wijk and Patterson, 92 Viles,' ref. 387, high-volume sampler, 129, 201 Vintinner (and Baetjer), 56 Vliet, ref. 417, flocculation of smokes, 25 Vorwaid et al., 45 Vorwald and Karr, 46 Walpole, 237-246 Walton el al., ref. 435, oscillating thermal precipitator, 101, 167, 188, 187 Wants, ref. 138, berylliosis. 55 Warner (and Bedford), 121 Warren, H., ref. 224. efficiency of impinger, 148, 151 ref. 132, welding fumes. Ill Warren, P. H., efficiency of water blasts, 26 Watkins-Pitchford, 38 Watkins-Pitchford and Moir, 103 Watson. C, H. (Simon et al.), 28-30 Watson, H. H., ref. 360, dust respi rator, 337 Watson, H. H. (and Green), thermal precipitator, 160. 182 Weber, ref. 204, health of foundrymen, 58 urinary lead, 61 Webster, ref. 146, glass wool and rock wool. 53 ref. 322. lead arsenate, 66 ref. 117, lead battery manufac ture, 61 Wells, P. V., and Gerke, 188 Wells. W. F., and Riley, ref. 141. bacteria in air. 124 Wells, W. F,, and Stone, W. R,, ref. 440, bacteria in air, 320 ST0853625 *, 388 INDUSTRIAL DUST Wexler, ref. 371, Donora pollution report, 1 Wheeler, ref. 6, rock dusting, 101 Whittenberger, ref. 1, effect of re sistance on breathing, 340 Whytlaw-Gray and Patterson, Smoke, book, 2 definition of smoke, 3 flocculation, 21-22 Williams, C. E., ref. 226, dust in foundries, 227 Williams, C. E.. et al., * filtering velocity and dust loading, 307 309 Williams, C. R., Bausch and Lomb counter, 143 fluorides in magnesium founding, 69, 112 fluorides, permissible concentra tion, 106, 112 ref. 388, high-volume sampler, 129 identification and analyses of dusts, 208-210 impinger dust counts, 153 magnesium founding, 69 ref. 372, talc, 52 Williams, C. R., cl al.. ref. 449, mercury concentratiohs, 112 Williams, C. R.. and Silverman, 154-155 Williams, H., ref. 450, lead poisoning from battery casings, 61 Williams, N., vanadium, 68 Wilson, H. B., et al., 94 Wilson, I. B., and La Mer, 92, 93 Wilson, W. L. (Cutter et al.), 59 Winslow, ref. 196, sandblasting, 216 WinBtow and Greenburg, ref. 454, wet and dry grinding, 219 Wolf, ref. 138, berylliosis, 55 Wong (and Rims), 132-135 Wood and Gloyne, 45 Wright, 275 Wycrs, 68 Yaffee, ref. 147, lead arsenate, 66 Yancey, ref. 384, air velocity and resistance in various masks, 338-340 Yant, ref. 366, lead fume retention, 90 refs. 59, 62, microprojector for impinger dust counts, 151, 154, 156 Zacks (and Pope), 38 Zenker, 35, 57 ST0853626 SUBJECT INDEX Abrasive blasting, wet, 219 Air filters, for air conditioning, 315 Abrasive blasting helmet, 344 318 Abrasives, alumina, disabilities from for bacteria, 320 manufacture of, 50-51 cost of cloth, 305-306 synthetic, as substitute for sand edge and variable compression, stone, 215 313, 315 Aerosol, definition, 2 high-efficiency types, 318-319 Aerosols, effect of size on retention increase of efficiency and resist by man, 92-95 ance on use, 301-305 for filter testing, 273-276 industrial, 305-320 optical properties, 26 life and upkeep, 311-312 particle size of various, 81 performance tests of, 298-320 stability of, 21-26 plugging for uniform porosity, wettability of, 323-325 303, 336 Aerotec, 292 protecting men cleaning, 312-313 Air cleaning, choice of equipment, resin-impregnated, 318, 333, 337 280 resistance coefficients for various cost and maintenance of equip dusts, 307 ment, 282-283 reverse jet, 309, 311 efficiency, definition of, 273 test media for, 273-276 efficiency required, 281-282 various fabrics for, 303-305 by electrical precipitation, 325 Air filtration, 295-320 332 control of resistance in practice, by filtration, 295-320 308 by gravitational and inertial effect of dusting and plugging on methods, 282-294 filter resistance, 301-305 permissible recirculation, 281-282 effect of fiber size on, 298-299 by scrubbing, 321-327 effect of particle size on, 298-299 iSee also Air filtration) effect of precleaning dusty air, Air-conditioning filters, 315-318 308-309 requirements for, 295 efficiency vs. air velocity, 300-301, Air displacement, in hot operations, 307-309. 225 efficiency vs. dust loading, 303 methods of measuring, 237-238, 305 243 efficiency vs. filter depth, 299-301 by process equipment, 226 efficiency vs. resistance, 301-303 significance in dust control, 220 recirculation in, 312-313, 315-320 226 role of diffusion in, 297-298 389 ST0853627 390 INDUSTRIAL DUST Air filtration, role of impingement in, 296-297 site of particles before and after, 299 temperature control in, 305-307 Air-line respirator and air mask, 333-340 Aitken's dust counter, 125-126 Aloxite, 51 (See also Alumina) Alumina, test of potency, 49 Alumina abrasives, disabilities from manufacture of, 50-51 safety in use of, 77, 215 Aluminum, fluorides evolved in pro ducing, 69 Aluminum oxide (see Alumina) Aluminum powder, collection by cyclone, 293 explosibility, 102 Aluminum therapy in silicosis, 49-50 Alundum (see Alumina) Alveoli, anatomy and gas exchange in, 31-33 dust retention in, 92-94 Anatase in mine air, 84 Anthracite coal (see entries under Coal) Anthracosilicosis, 35, 53-54 Anthracosis, 35, 53-54 Antimony compounds, permissible concentrations, 112 Antimony powder, explosibility, 102 Arrestance by air cleaners, defini tion, 273 Arsenate of lead sprays, 66 Arsenic, 65-66, 112 Arsenic compounds, permissible con centration, 112 Arsenic trioxide, effects of exposure to, 65-66 Arsine, generation aad toxicity of, 65, 72 Artificial abrasives, 77 as substitute for sandstone, 215 Asbestos, test of potency, 49 Asbestos fibers for filter plugging, 303, 337 Asbestos products, number of men handling, 90-98 Asbestosis, British mortality from, 39 definition, 35 . and lung cancer, British statistics, 46 pathology and disability from, 45 permanence of, 36 Asbestosis bodies, 45-46 Asthma, bronchial, from debarking maple trees, 74 Atmospheric dust, particle size of, 81 Bacteria in air, determination of, 124 Bacterial filters and respirators, 320 Baratosis from barium sulfate, 58 Barium compounds, permissible con centrations, 112 Barrc granite study, 81, 108 Barrel filling, dust control in, 223, 257 Bausch and Lomb counter, 142-144 Bauxite, 51 Bentonite, test of potency, 49 Beryllium poisoning, epidemiology and prevention, 54-55 Bituminous coal (see entries under Coal) Blast-furnace gas, dust measurement in, 30 Blast gates, objection to, in dust exhaust systems, 262 Blood cells, size of, 81 Breather pump for mask testing, . 340 Bronchi, anatomy of, 31-33 Bronchial asthma from debarking maple trees, 74 Bronzing powder, explosibility of, 102 Brownian motion, 15 Bubar's apparatus for dust sam pling, 166 Byssinosis, 35, 75 ST0853628 ' SUBJECT INDEX 391 Cadmium oxide, effect of, 64-65 Cadmium oxide fumes, permissible concentration, 112 Cadmium powder, explosibility, 102 Caicite, 48 (See alto Calcium carbonate) Calcium carbonate, harmlessness of, 56 test of potency, 48 Calcium carbonate dust, retention of, by man, 90-91 settlement of, 274 Cancer of lung from dusts, 46, 63-66 Capture velocities required in vari ous processes, 257 Capture velocity and exhaust venti lation, 243-246 Carbon black, particle sice of, 81 Carbon dusts, 53-54 (See alto Coal dust) Carpathian miners, silicosis among, 40-41 Cartridge respirators, 337-338 Cascade impactor, 144-146 efficiency of, 146 vs. thermal precipitator, 146 use in size measurement of par ticles, 179-182 Castings, exhausts for jet cleaning of, 253 Castor-oil beans, toxicity of dried residue, 73 Cement, harmlessness of, 56 permissible dustiness, 110 test of potency, 48 Cement plants, number of men in, 96 CSiert, 77 Chimneys (see Stack discharge) Chip traps in exhaust systems, 265 Chlorite in mine air, 84 Chromate dust, effect of, 64 Chrysotile asbestos, 45 Cilia and dust inhalation. 33 C5*y, selective settlement from foundry dust, 87 various, effects of breathing, 49, 52 Cleaning efficiency, definition, 273 (See alto under various appa ratus) Clouds, definition of, 2-3 Coal dust, exposure in mining opera tions, 96-98 pathogenicity and rank of, 54 permissible, 109 test of potency, 49 Coal dust explosion, cause and pre vention, 100-101 Coal miners' lungs, 53-54 analyses of, 104-105 . Coal miners' pneumoconiosis, epi demiology, 41 social consequences of, 54 time-dustiness studies of, 116 Coal mining, water infusion in, 218 Coal trimmers, report on, 53 Cocoa, explosibility, 101 Conveying velocities for various materials, 263 Copper, 70 arsenical ores of, 65 Copper oxide, metal-fume fever from, 70 Copper powder, explosibility, 102 Cornstarch, explosibility, 101 Corundum smelter's lung, etiology of, 51 Cotton flock, collection by cyclone, efficiency of, 293 Cotton-mill fever, 75 CottreJl process, 325-330 Count-weight conversion in dust sampling, 109, 120-121 Count-weight relation of particulate size, 194 Cristobolite, 77 Crushing of rock, dust control in, 257 Cryolite, 69 Cummings' elutriation method, 183-185 Curve fitting in size-frequency meas urements, 195 Cyclone, 288-294 performance test of, 293 wet type, 324 ST0853629 392 INDUSTRIAL DUST Diamond dust, harmleesness of, 77 Diatomaceous earth and silicosis, 77 Diatomite, test of potency, 48 Differential fusion for quartz deter mination in dusts, 211 Diffusion, role of, in air filtration, 297-298 Disaggregation and shattering of particles by impinger samplers, 138, 141, 144, 151, 152, 163, 167 Discharge stacks, 277-280 Dispersion of dusts for microscopy, 171-174 Dispersion force in relation to ex haust systems, 231 Dolomite, galena, and quartz, selec tive settlement, 86-87 for rock dusting of coal mines, 100 solubility of, 56 test of potency, 48 Donora pollution report, 1 Dunn counting cell, 153 Dust, allergic reactions from, 31, 72 analysis, chemical and mincral- ogical, 200-212 chemical composition, 83-88 definition of, 2-3 ' disintegration and selective settle ment, 83-88 dispersion and control of, 15, 171, 231 cxplosihility of, 98-103 fate of inhaled, 33-35 ingestion by phagocytes, 33, 39 inhaling vs. swallowing, 59 microscopy of, 171-199 optical properties, 26 permissible concentrations, 106 112 physical properties of, 1-30 physiological effects of, 31-55 (See atso specifiosubjects, as Silicosis) radioactive, 62 retention of, by man, 89-95 for rock dusting of coal mines, 56 58 silicotic potency, 48, 83, 100 Dust, toxicity of various, 59-70 wettability of, 323-325 Dust clouds, production of, for test ing, 93, 274-276 settlement of, 24-26 Dust concentration* absolute, deter mination of, 126 accuracy required in measuring, 119 count-weight conversion, 98, 120 121 determination of, 123-165 by electrical precipitator, 155 160 by filtration, 126-132 by impingement, 132-155 by thermal precipitation, 160 162 various, found in practice, 97-99 Dust collectors (see Air cleaning; Air filters) Dust control, air displacement and, 221-226 capture velocities required for, 257 by enclosures, 228-229 local exhaust systems for, 230-272 methods for, 213-229 plant operation and layout, 226 229 by process change, 214-215 and silicosis, 107 at source, 214 by sprays, 26, 220 by wetting at source, 216 Dust counting, conversion of count to weight, 98, 109, 121 by light- and dark-field micros copy, 80, 152, 155 by microprojection, 154 overlapping of particles in, 142 146 (See also under various apparatus) Dust explosions. 98-103 apparatus for determining risk of, 101 effect of particle size on, 102 Dust-feed devices for filter testing, 93, 273-276 ST 0853630 % SUBJECT INDEX 393 Dust loadings, definition, 273 determination of, 113-122 in practice, 280-282, 295 Dust particles, size of air-borne, 79 83 size frequency, 179, 191-199 size limits in microscopy, 80 specific surface of, 189 Dust respirators, 336-346 coat of upkeep, 345-346 detecting leakage of, 340-341 filtering efficiency, 342 filters of uniform porosity, 336 history and development, 336-338 valves for, 341-342 velocity and resistance through, 338-340 Dust sampling, for chemical and mineralogies! analysis, 200 instruments for, 163-165 man as instrument for, 117 from rafters, 203 rate, air volume, and frequency, 114-118, 166 size separation, 201-203 Dust storm, 1 Dust survey, 113-122 Dustiness, engineering control and sampling, 119 fluctuation expected, 115 permissible, 106-112 seasonal variations in, 119 Dusty trades, concentrations in, 97 99 mortality in, 41 respiratory disease in, 96 tuberculosis in, 76 Dyspnea in silicosis, 37, 41-43 Edge and variable compression filters, 313, 315 Ejector-flowmeter for dust sampling, 149 Electric precipitator, for air clean ing, 325-332 for dust sampling, 155-160 Electric precipitator, for particle size determination, 167, 186 performance tests of low voltage, 326 Electron microscopy of dusts, 185 190 Electroplating, hoods for, 251 Elutriation for size measurement of particles, 182-185 Emphysema as cause of silicotic dyspnea, 43 Ethyl iodide gas, retention of, by man, 92 Exhaust hoods, aerodynamics of, 243-260 coefficients of entry, 264 pressure losses in, 263-265 static suction as measure of per formance, 255 ventilation requirements of, 254 260 zones of effectiveness, 254-260 Exhaust systems, design of, 230-272 effect of abrasion in, 266 low-velocity, 266-271 Explosive dusts, 98-103 determination in air, 126 fan for handling, 271-272 Falling droplets, air flow induced by, 235-237 Falling materials, air flow induced by, 231-240 ventilation required for, 231 Fan, location of, for exhaust sys tems, 272 Feldspar, test of potency, 49 Ferric oxide fume, permissible con centration, 111 Ferromanganese powder, explosi- bility, 102 Fiberglas (se<? Glass wool) Filar micrometer, 177-178 Filters (see Air cleaning; Air filters: Dust respirators) Filtration, determination of dusti ness by, 126-129 I ST085363 I 394 V INDUSTRIAL DUST Filtration, theory of, 295-305 Galvanized iron, metal-fume fever Filtration rate, definition, 273 from welding, 72 Filtration velocity, definition, 273 Canister, 77 Flint, 77, 218, 219 Gilding powder, explosibility of, 102 Flint knappers, silicosis among, 76 Glass wool, for air filters, 315-318 Flocculation of aerosols, 21-26 effects of, 52-53 Flour, explosibility, 101 filter pads, bacterial filtration by, size of particles, 81 320 Flowmeter, ejector type, at constant Granite cutting, dust fluctuations flow, 149 in, 115 Fluoride dusts, permissble concen hoods for, 255, 257-259 trations, 106, 112 Fluorides, 69-70 silicosis from, 47, 76 Granite dust, composition of, 204 Fly ash, size of particles, 81 inhalation by experimental ani Fog, definition of, 2-3 mals, 47 sea, size of particles, 81 silicotic nodules from, 37 Food dusts, various, explosibility of, silicotic potency of. 47 101 study at Barre, 81, 108 Foundry dust, mineralogical analy Granite quarrying, time-dustiness ses of sized fractions, 202-203 studies of, 116 mineralogy and selective settle Graticule for microscopy of dusts, ment of, 85 178 screen analyses of air samples, 281 Gravel collection by cyclone, effi Foundry sand, free silica in, 87 ciency of, 292 Foundry workers, healthiness of, 38, Grinders' rot, 35 42, 58 Grinders, sandstone, and silicosis, 76 number of, in U.S., 97 Grinding, dust control in, 257 Franklinite dust, 63 size of particles produced by, 79 Free silica, determination of, 204-208 wet, dustiness from, 219 determination in presence of sili Gritstone, 77 cates, 207-212 Gypsum, harmlcssness of. 57 variation with particle size in for rock dusting of coal mines, 100 mixed dusts, 202-203 test of potency, 48 Fuller's earth, 49, 52 Fume concentration, determination of, by electrical precipitation, Hematite, test of potency, 49 155-160 Hematite dust. 57 by filter paper method, 128-131 Hersey reverse jet air filter, 309-311 Fume retention by man, 89-90 High-efficiency filters, 318-319 Fumes, definition and physical prop requirements for, 295 erties of, 1-30 High-volume filter for dust sampling, (See also Metal-fume fever) 129 Hoods, aerodynamics of. 243-260 pressure losses in, 263-264 Galena, low incidence of lead poison (See also Exhaust hoods) ing from handling, 61 Hot processes, air flow induced by, quartz, and dolomite, selective 238-243 settlement, 86-87 ventilation required for, 240-243 i t 4 ST 0853632 SUBJECT INDEX 395 Housekeeping and dust control, 229 Howard dust collector, 286 Hydroblast, 219 use of, in foundry shakeouts, 253 Hydrofluoric acid, permissible con centrations of, 112 Hydrogen selenide, 07 Hygienic survey, 113 Immersion method for quartz identi fication, 209-210 Impingement, 18-19 disaggregation and shattering by, 134, 151-152 dry and wet compared, 134, 151 dust-determining apparatus, 132 152 effect of jet shape, 133-135 role of, in air filtration, 296-297 Impingcr samples, microprojector for counting, 154 overlapping of particles, 138 Impingors, effect of coating plate, 138-146 efficiency of, 132, 151 by impact, 134 Greenburg and Smith, 147-155 midget, 150 Inert and toxic dusts, 56, 59 Inertial separators, 287-294 Inflammable vapors and dusts, fan for handling, 271-272 Insecticidal dusts, cxplosibility of, 101 Insecticides, 66-68 Inversions and stack effluents, 277 280 Iron oxide dust, 57 Iron oxide fume, permissible concen tration, 111 Iron powder, cxplosibility, 102 Jasper, 77 Jets (see Impingement) Joplin, silicosis and dustiness mines at. 108 in Jumper duct in low-velocity sys tems, 268 Kaolin, test of potency, 49, 52 Konimeter, critical review of sam pling by, 118 efficiency of, 138-140 Kotz6, 135-140 vs. thermal precipitator, 138-140 Konimeter samples, counting, 136 overlapping of particles, 138 removal of nonsiliceous matter from, 136-137 Lead, 60-62 absorption of, and control, 60-62 dust and fume, permissible con centration, 110-111 fumes, determination of, 128-131 from tetraethyl lead, retention of, by man, 90 metal-fume fever from, 70 metallizing with, 01 toxicity of various compounds, 111 urinary concentration and per missible dustiness, 60, 111 Lead arsenate sprays, 66, 111 Lead batteries, manufacture of, health of workers, 61 poisoning from burning casings, 61 Lead burning, 61 Lead oxide, metal-fume fever from, 70 Lead-painted steel, risk in flame cutting, 61, 111 Lead poisoning, from arsenate of lead sprays, 66 from burning battery casings, 61 prevention of, 60-62 Lead powder, explosibility of, 102 Light-vs. dark-field counting of dust, 80 Limestone, harmlessness of, 56, 58 permissible dustiness. 110 retention of, by man, 91 ST0853633 396 INDUSTRIAL DUST Limestone, for rock dusting of coal mines, 100 (See also Calcium carbonate; Mar ble) Litharge, permissible dustiness, 111 Local exhaust systems, design of, 230-272 . Local exhaust ventilation, capture velocity required in, 243-246 Low-velocity exhaust systems, 266 271 Luminous paint, 62 Lung, anatomy of, 31-33 analysis, in silicosis, 103-106 cancer of, from dusts, 46, 63-66 Lymph nodes and dust deposits, 34 Magnesite, harmlessness of, 56 Magnesium carbonate, harmlessness of, 56 Magnesium founding, fluoride con centrations in, 112 fluorides used in, 69 Magnesium oxide, metal-fume fever from, 70 Magnesium oxide fume, flocculation, 21, 23 permissible concentration, 111 retention of, by man, 90-91 Magnesium powder, explosibility, 102 Make-up air, in exhaust systems, 263 Manganese compounds, permissible dustiness, 110 Manganese dioxide, dust, effect of, 63 metal-fume fever from, 70 permissible dustiness, 110 Manganese powder, explosibility, 102 Manhattan Project, 63' Marble, dust, flocculation, 21, 23 harmlessness of, 56 permissible dustiness, 109 solubility of, 56 (See also Calcium carbonate) Mass median diameter of particles, 81 Materials handling, dust control in, 221-226 and ventilation requirements, 231 238 ' Maximum allowable concentrations, 106-112 May's graticule, 178 Mechanization and dust control, 227 Medical control and dustiness, 213 Melanosis, Stratton's description of, 53 Membrane of molecular filters, 129 132 Mercury, permissible concentration, 112 Metal dusts, apparatus for determin ing in air, 128 Metal-fume fever, 31, 70 effect of deep breathing, 70, 92 importance of dispersion and par ticle size, 71 Metal fumes, permissible concen trations, 111 sampling by electric precipitator, 160 sampling by filter paper method, 127-129 Metal industries, silicosis in, 42 Metal miners, silicosis among, 41-42 Metal powders, explosibility, 102 size determination by Roller's method, 170 Metallizing, 61 Mica, effects of inhaled, 52 test of potency, 49 Microscopy of fine particles, 171-199 Midget impinger, 150 vs. molecular filter, 132 Mill fever, textile. 75 Mineral dust, determining on paper filters, 128-129 staining of. 212 Mineral wool, effects of, 52 Mineralogical analysis of dust, 200 212 i ST0853634 SUBJECT INDEX 397 Minerals, various, men exposed to dust of, 96-98 Miners' asthma, 35 Miners' phthisis, 35, 103, 107 (See alto Pneumoconiosis; Sili cosis) Mining, dust exposure in, 40-45, OSOS number of men engaged in, 96-98 use of water in, 218 Minute volume and respirators, 32, 338-340 Mist, definition of, 2-3 physical properties of, 1-30 Mists, insecticidal, for spraying, OS es Molecular filter, for dust sampling, 129-132 for particle sire determination, 167 Mounting media, 173-174 Mucking, dust control in, 218 Mullite, toxicity of, 51, 52 Nose as dust filter, 89 Olivine, effects of breathing, 52 Opal and silicosis, 77 Organic dusts, effects of breathing, 72-74 explosibility, 101 Oscillating thermal precipitator, 161 sire measurements with, 167, 186 Oscillation of particles in electric field, use of, in size measure ments, 188-189 Owens' jet dust counter, 140-142 criticisms of dimensions, 142 efficiency of, 140 shattering of particles by, 141 vs. thermal precipitator. 141-142 Oxygen consumption by man. 32 Paint-spray mask (air-line respira tor), 334, 344 Paint spraying, capture velocities re quired in controlling, 257 Particle sire, determination of, 166 199 by count-weight method, 190 by elutriation, 182-185 .by microprojection, 178 from pipe lines, 166 from still air, 167 graphical representation of, 190 199 physiological limits of, 82 and polarization, 26-28 statistical analysis, 190-199 Particles, acceleration in air, equa tions, 10-12 diameter of, 179, 190-191, 194 drag coefficient vs. Reynolds num ber, 5-6 dynamic projection. 14 dynamics of, 4 movement in centrifugal field, 16 17 movement in electric field, 19-20 resistance to travel in air, 5 stirred settling of, 15 Pease-Anthony Venturi scrubber, 323 Pegmatite, effects of inhaled, 52 Penetration in filters, definition, 273 Permissible dustiness. 106-112 Petrographic analysis of fine dusts, 208-212 Phagocytes containing dust, 33 Phagocytosis of quartz and carbon, 35 Phosphorus compounds, permissible concentration, 112 Photographs, use of. in surveys, 121 Phthisis, miners', 35. 103, 107 (See aho Pneumoconiosis;Silicosis) Piping, design and construction for exhaust systems. 260-271 Plastics, explosibility of dusts of. 101 Pneumoconiosis. 31-54 benign, 58-59 definition. 35 epidemiology and etiology, 35-47 ST0853635 398 INDUSTRIAL DUST Pneumoconiosis, physical and chemi cal factors in, 76-88 Polarization of light hy dust par ticles, 26-28 Pollen, allergic reaction from breath ing, 72 . Pollen asthma, prevention by wear ing respirator, 72 Porosity of filters, definition. 273 Porton graticule (May), 178 Portland cement (see Cement) Potassium bichromate, effect of, 64 Potteries, 96, 98, 218 Powders, specific surface of, 189 Precipitator ash, test of potency, 49 Protector dusts, Gardner's, 49 Pumice, 52 Pyrophyllite, 49, 52 Q, air-flow, determination of, for process control, 257-262 Quarry operatives, silicosis among. 41-42 Quarry workers in U.S. and Britain, 97-98 . Quartz, content of mixed dusts and particle size, 202-203 cytocidal power of, 37 determination of, 204-212 occurrence and properties of, 76 79 permissible concentration. 107 110 phagocytosis of. 35 potency of various size particles. 82-83 and selective settlement. 86-87 and silicosis, 76 test of potency, 48 Quartzite, 77 . Radioactive dust, 62 determination in air. 124. 130 Recirculation in air filtering, 281 282, 312-313. 315-320 Refractive indices, of mounting media, 173-174 Resin-impregnated filter, for air cleaning, 318 for dust respirators, 333, 337 Resistance of air cleaners, definition, 273 Respiration and dust inhalation, 31 Respirators, 336-346 cost and upkeep, 345-346 valves for, 341-342 ` (See also Dust respirators) Respiratory cycle and respirator testing, 338-340 Reverse-jet air filter, 309-311 Ricin in castor-oil beans, 73 Rock drilling, dry and wet, 57, 216 New York code covering, 109, 117 permissible dustiness in, 109 for producing dust clouds, 24, 274 screen analysis of dust from, 280 281 size of particles produced by, 80 time-dustiness studies of, 116 Rock dusting of coal mines, cost of, 101-102 Rock wool. 53-54 Roller air analyzer, 169 Sand, collection by cyclone, effi ciency of, 293 as free silica, 77 test of silicotic potency, 48 Sandblasting, helmet, 344 introduction of. 58 safety in, 216 silicosis from, 216 Sandstone, 77 Sawdust. 73-74 Schnccherg and Joachimstal mines, 63 Screen analysis of dusts, 168 Scrubhers. inertial. 322-325 mechanical-centrifugal, 321-322 Scrubbing of air for cleaning, 321 327 ST0853636 SUBJECT INDEX 399 Sedgwick-Rafter cell for dust count ing, 153 Sedimentation cell, 125 Selenium, 66-67 coating of dusts for microscopy, 174-177 compounds, permissible concen trations, 112 Separation factor, 17, 288-289 Sericite, in dusts, 84-85 test of potency, 49 Settlement, determining dustiness by, 123-126 Settling chamber, gravitational, 283 287 Settling velocities, 7-9 Shale dust, size of particles, 81 test of potency, 49 Shape of irregular particles, defining, 199 Shattering of particles by impinger, 152 Shaver's disease, 51, 215 Shot blasting, introduction of, 58, . 216 Siderosis, 35, 57 Silica, colloidal, toxicity of, 50, 77 determination, 204 free and combined, definition, 204 fumes, toxicity of, 50-51 in lungs of silicotics, 103-106 metabolism of, 78 permissible concentration, 107 110 occurrence and properties, 77 and silicosis, 76 solubility of, and silicosis, 77-78 Silicates, determination of free silica and, 207-212 toxicity of, 51-53 Silicatosis, 35, 52 Silicon alloys, silicosis in manufac ture of, 50 Silicon carbide, harmlessness of, 77 test of potency, 49 Silicosis, aluminum therapy in, 49 definition. 35 in dusty trades, 41-42, 96-98 Silicosis, dyspnea in, 41 employability of men with, 41 etiology of, 47 fibrotic nodules in, 36-37 length of exposure to produce, 38, 40 lung analysis in, 104-105 mortality from, in Britain, 38-39 in old and young workers, signifi cance of, 43 and other pneumoconioses, 35 particle size and potency, 79-83 permanence of, 36 permissible dustiness to prevent, 107 prevention of, 47 and tuberculosis, 36-41, 43 uncomplicated, rarity of, 37 Silicosis Act (British), 57 Sillimanite, effects of breathing, 52 Size frequency of particles, 190-199 Smoke, definition of, 2-3 Soap powder, explosibility, 101 Soapstone, test of potency, 49 Sodium bichromate, effect of, 64 South African gold mines, dust sampling in, 84, 118-120 permissible dust, in, 107 silicosis in, 103, 107 Specific surface of particles, count vs. weight, 194 measurement of, 189 Spencer haemocytometer, 153 Stack discharge, 277-280 control of, 282 Staining of mineral dusts, 212 Starch, explosibility, 101 Steel shot for abrasive blasting, 58, 216 Stone cutters, silicosis among, 42 43 0 Stone ladder to reduce dust scatter ing, 222 Stonocutting, dust control in. 255. 257-259 Streamline motion of particles in air. 7-9 ST 0853637 400 INDUSTRIAL DUST Submicroscopic particles, measure ment of, 188 Sub-sieve sizes of dust, elutriation of, 183-185 Sugar tube for dust determination, 126 Supplied-air masks, 333-346 Surface-area measurement of par ticles, 189-190, 194 Surge bin, use of, in ore handling, 236 Synthetic abrasives as substitute for sandstone, 215 Traprock, test of potency, 49 Tridymite, 77 Tripoli, test of potency, 48 Tuberculosis in dusty trades, 76 Turbulent motion of particles in air, 7-9 , Two-stage precipitators, 330-332 Tyndall beam, 26-30 Tyndallmeter in dust studies, 27 Uranium oxide dust, deposition and retention of inhaled, 94 Talc, collection by cyclone, efficiency of, 293 effects of inhaled, 52 test of potency, 49 Tellurium, 66-67 compounds, permissible concen trations, 112 Textile dusts, 74-75 Textile mills, bacteria in air of, 124 Thermal precipitation, 2L Thermal precipitator, 160-102 vs. Bausch and Ixjmb counter, 144 vs. cascade impactor, 146 vs. konimeter, 138-140 vs. Owens' counter, 141-142 for particle size determination. 167 Tin oxide, benign pneumoconiosis from, 59 Tin powder, cxplosibilitv, 102 Titanium powder, cxplosibility, 102 Tobacco smoke, determination of, by electric precipitator. 159 effect of turbulence on settling, 25 retention of. by man. 90 Trachea, air velocit"y in. 92 anatomy of, 31-33 Trail smelter, 278 Transfer points, capture of dust at, 257 Transporting velocities for various materials, 2G3 Vanadium, 68-69 Velocity contours of exhaust hoods, 246-260 Viscous filters, 315-318 Volcanic ash, test of potency, 49 Volume of particles, count vs. weight, 194 Water jets, high-velocity, for clean ing castings, 253 Water sprays, dust control by, 219 particle size of. 81 Weighted average dust exposures, 115 Welding fumes, 111-112 causing benign pneumoconiosis, 58-59 Wet abrasive blasting, 219 Wet collectors, 324-327 Wet drilling, 216-218 introduction of, in Britain, 57 Wet grinding, 219 Wettability of dusts, fumes, and mists. 323-325 Wetting agents, 220 Whipple disk for dust counting, 152 Wood bark, asthma from spores in, 74 Wood dust. 73 Wood waste, collection by cyclone, efficiency of, 293 ST0853638 SUBJECT INDEX 401 X-ray, appraisal of silicosis and asbeatosis by, 38 X-ray diffraction analyses, 210-211 Zinc oxide fume, effect of turbulence on settling, 25 metal-fume fever from, 70-72 particle size of, 81 Zinc oxide fume, permissible concen tration, 111 retention of, 92 Zinc powder, explosibility of, 102-103 Zinc refining, electrolytic, arsine from, 72 Zinc smelting, health of workers in, 72Zirconium powder, explosibility, 102 - DECEIVE l t IHD 1py !.*? 1956 i , rlt~ ' > / r Til!# m us;. } ST0853639