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FILE NAME: CERAMICS (CER) DATE: 1936 Oct DOC#: CER012 DOCUMENT DESCRIPTION: Journal Article - The Causation of Pneumoconiosis \ICOLOGY [Sept., 1836 'mined as much by the ng as by the selection of 'inplcte discussion of fan tore, consideration should ''ole system and not to the application of fans to of exhaust, pressure and would form a welcome esent volume. 'onfusion that exists with 'nition of total and static od by an exhaust fan nn in a blowing or booster or would have done well ightforward discussion of was prepared primarily ii the proper selection of tical considerations have -.dary to this practical ay that has not weakened dore Hatch. / THE JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY Volume 18 OCTOBER, 1936 N umber 8 THE EFFECTS OF HEAT AND HUMIDITY UPON THE HUMAN BODY* Cecil K. D rinker From the Department of Physiology, Harvard School of Public Health, Boston CONSIDERATION of heat falls into divisions: of the effects two natural worked through regular shifts during long periods of time. 2. The effect o f residence in tropical 1. The acute effects of encounteringclimates. By this is meant the grad very high temperatures such as are met ual deterioration experienced by most in m any industrial processes and under northern white people who reside in natural conditions in such places as the tropics. A tropical climate of the the desert regions of southwestern United States. The temperatures with which we are concerned in this division of our inquiry are necessarily high. Brief exposures to temperatures of 200F. are encountered in the steel industry. One hundred and fifty de grees Fahrenheit is frequently found in the stokeholds of coal-fired steam ers. Outdoor temperatures of 100 to 125F. were met at Boulder City, Nevada, and under such exposure men sort that interests us is characterized by little change. There are no seasons such as we have in the temperate zone. Monthly temperatures and tempera ture differences between day and night are slight. In the Marshall Islands for example, islands lying in the equatorial belt, the daily maximum temperatures for a year were between 88 and 91.5F. and the daily minima, between 75 And 77F. It has been said of such places that "they possess Received for publmation July 3, 1936. Read before the Harvard University Ter centenary Celebration, 1636-1936, Sympo sium on "The Environment and Its Effect on M an." Harvard School of Public Health, Boston, August 25, 1936. more climate and less weather", but in spite of such qualification they are not so suitable for human residence as are the changeable regions of the temperate zone. 471 /O aaeoasm rHfrrrii rif THE CAUSATION OF PNEUMOCONIOSIS* Philip D rinker Prom the Department of Industrial Hygiene, Harvard School of Public Health, Boston, Mass. T HERE are four different types of reaction produced in man by the inhalation of dust. The first and most important are the pneumoconioses, such as silicosis and be small enough to float about in the air and be carried by rather slight air currents; otherwise they cannot be in haled. The modem word, pneumoconiosis, asbestosis, which cause specific lung is a shortening of Zenker's original pathology and often are followed by j.ncunionokontosis. Zenker (1) de pulmonary tuberculosis. The second picted lungs definitely damaged by type of reaction is caused by toxic dust particles, but today pneumoconio dusts like lead, cadmium, and radium. sis Is generally used to describe any A third type of malady follows the lung which has been dusted to more inhalation of finely divided metallic than the normal degree--there need fume particles such as zinc oxide and not necessarily be demonstrable lung is known as metal fume fever. Fi pathology. Silicosis, asbestosis, an nally, the fourth reaction, allergic in ti, racosis, anthraco-silicosis, and simi character, is caused by breathing or lar terms indicate the different ganic dusts such as pollen and certain causative agents (silica, asbestos, and types of pulverized wood and flour. coal) in various kinds of pneumoconio In all four instances dust inhalation sis. can be the sole cause of the disability The International Silicosis Confer but with the toxic dusts characteristic ence in 1930 i,2j defined silicosis as a reactions result from swallowing as ``pathological condition of the lungs well as from inhalation. The latter due to the Inhalation of free silica route, however, is much the more im (SiOj)". The American Public portant. Health Association (3) described it as In the present instance we are con a "disease due to breathing air con cerned only with the pneumoconioses taining silica." Sayers and Jones (4) which result solely from the action of state that ``from the viewpoint of inhaled dust upon the lung tissue. Of etiology, the harmfulness of a given necessity then, the dust particles must dust containing free silica is directly influenced by the number of particles ` Received for publication July 14,. 1936. Read before the Harvard University Tercentenary Celebration, 1636-1936, Sym posium on "The Environment and its Effect upon Man". Harvard School of Public Health, Boston, August 27, 1936. of free silica less than 10 microns in diameter that it contains". Collis has claimed for years that free silica, es pecially quartz, was the all-important 524 dfifairi&flfe^ ref. IS, no. SJ factor. In summ.v African experience. \ (5) wrote In 1927 the. silica could ``give r permanent and rd conditions--one can diseases--as anthra siderosis etc" . In figure 1 arc Collis indicating t! portance of free Public Health S, r o c c u p a tio n FLINT KtiFPPEFi (Brando*)) OR/NDEPS (Sheffitld) GKfiHlTE-CUTTZPS ( r it. anJ KH.) POTTERS co/TL-mn ino Fig. J.-Mv-rta:-;;, shown in tal-h' !. : ther the imporr:.:. Silica.--Silica c manly as the minor:., a natural contamina occurs in many rock.-, fairly ~ure state as : flint, sandstone, gr. quartzite, and jasper. Quartz is a hard t which is weakly bin its two indexes of rtogether. Chemical; and inactive. In fa< : inertness are the tw; make it especially uOther varieties of n I>Bissau IOSIS* lie Health, Baton, Mat*. to float about in the d by rather slight air ise they cannot be in- vord, pneumoconiosis, of Zenker's original 3. Zenker (1) de finitely damaged by it today pneumoconioused to describe any been dusted to more 1 degree--there need -ie demonstrable lung osis, asbestosis, anico-silicosis, and simif "N icate the different (silica, asbestos, and ands of pneumoconio- onal Silicosis Conferdefined silicosis as a ndition of the lungs alation of free silica American Public on (3) described it as <o breathing air conSayers and Jones (4) n the viewpoint of .rmfulness of a given free silica is directly <}number of particles than 10 microns in contains". Collis has rs that free silica, esivas the all-important vol. 18, no. A] CAUSATION OF PNEUMOCONIOSIS 525 factor. In summarizing his South African experience, Watkins-Pitchford (5) wrote in 1927 that dusts other than silica could "give rise to such non permanent and relatively harmless conditions--one can hardly call them diseases--as anthracosis, aluminosis, siderosis etc". - - In figure 1 are shown data from Collis indicating the etiological im portance of free 6ilica. The U. S. Public Health Service's data (6), opal, which is non-crystalline, have not as yet been appraised hygienically and there are no statistical studies to show the relative potency of the vari ous forms of pure silica. Silicates.--Silicatosis is a word sug gested by Badham (7) to describe a lung fibrosis caused by dusts in which silicates and not free silica predomi nate. The distinction between free and combined silica is best shown by a simple example: A granite dust (8) occi/panoN FUNT KMFPERS (HnmHoo) GRIHOER9 (ahtffitid) citmiiT<irrmes (M*. mod H.H.) POTTERS COfflr MINING B QURRTZ CONTENT I o r oust PERCENT DEPTHS FROM puutoMur naataM ds PBBO BBBBBH 8BH II 100* | 50 t# \W \N 3or. la . % p s .* * Fro. 1.--Mortality from pulmonary tuberculosis in various dusty trades. (After Collis) shown in table 1, emphasize still fur might have the following mineral com ther the importance of free silica. position: Silica.--Silica occurs most com monly as the mineral, quartz, which is a natural contaminant of most ores, Perm I Feldspar (orthoclase)....................... 70 Quarts................................................. 25 occurs in many rocks, and is found in a Mica (muscovite)................................. 5 fairly pure state as beach sand, chert, flint, sandstone, gritstone, ganister, 100 quartzite, and jasper. Quartz is a hard crystalline mineral which is weakly birfringent, that is, Chemical analysis of this granite ' would give the following result: its two indexes of refraction are near Portent together. Chemically it is very inert 8iO, (to ta l)................................... 72.55 and inactive. In fact its hardness and AM),............................................... 14.80 inertness are the two properties which make it especially useful in industry. K ................................................. 12.42 H .0 .................................................... 0.23 Other varieties of pure silica such as 100.00 JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [ reci CO coal sul 3 o SUHMAHT OF TUT. S lX 1>H S T S t C I>I ES HY TIIE II. S . INI) VBTBy AVAEHOE i*t;bt COUNTIN wiu.toNB nr r \ nrtci.r-A ter cemc FOOT AVERAGE P RftNT- AOR nr Atl.ICA (QUARTf.) TA1U.K 1 . H f.a i .t i i S f. k v h -k S h o w i n t u e D e u t C o n c k n t h a t i o n , C o m p o s i t i o n a n i . t h e R esulting IIaxakd* .................. OTHER CHARACTERIATNR or i>rRT n r . C P r . B o r t u n i n r w D M c o n d i t i o n a b o m i h t i d i n c a c i i b t t ' j-vt (ramie cutting: Hand-pneumatic ton! o p era t or ................................................. Surface-machine operator, e t c ............. ........................ ( doncral a i r .................................... I-e t h a n g e n e r a l a i r . . - :v> :) 20 0 Balance mostly hined ilica mm-l G r e a t e x c e s s of p u l m o n a r y t u b e r c u l o s i s a f t e r 15 y e a r s o r m o r e e x p o s u r e ; s i l i c os i s i n f r o m 2 t o 10 y e a r s . Si l i cosi s a f t e r p r o longed e x p o s u r e ; no excess of tuberculosis Negative except for occasional nondisftbling silicosis Anthracite coal: R o c k d r i l l e r .......................... Miner and miner' helper X2 m SilieeouH rock I bita insufficient; other studies show Revere ha za rd i r, C a r b o n a n d i n o r g a n i c D y s p n e a a n d o t h e r s i g n s of p n e u m o c o n i o s i s ; ex< es s s i c k n e s s matter *> u. t . \ from respiratory conditions; excess mortality from in fluenza, pneumonia and possibly tuberculosis Bituminou coal: Rock driller . 7X Izoaderfl And m a c h i n e men 112 ( Y m e n t ............................................ 20 Cotton-cloth manufacturing. 7 Silverware manufacturing . 5 M u n i c i p a l ......................................... f After Thompson, ct al. r.i 1 2 S u u N t imp ( 'a r l ' o n r> x r r i m a r i l y l i me 7 Vegetable and silica 1 7 Metal and other 7 Not determined D a t a i mhu f b e i e n t ; o t h e r s t u d i e s i n d i c a t e s e v e r e h a z a r d ( localized fibrosis chiefly linear in character; excess mor- falitv from influenza and pneumonia ' ' Some early pneumoconiosis; excess of disease of up p e r rcspirato rv tract. am! of influenza Negative Negative Ncg ati vo ir o o Cu aP p O cr O pB too b ol p cr o - JO K' p 5re' o 5` CT5 C P B o n n a. o S 5' I o M O- :;i P IS H ZZ- i n - o a - ' r, O o p* r X Li. ' r cr to X p tn o p. CL. o cZ 'it a - ~.J-s 5 ' 1 - cp n o tr o oo rcr>r 7 ` o:: [sn'5 cr n 12 ' u> cr o c: H p p ^ p o 1 txi o r r . . ^7- 0 X 5 Pm C x P 0 EO3T p% in5Hf>>!- tr: pPoUl pcOr Z-Z* p o p c r C3 M rr> GO V 0 b- o o 0 p 5 * S3 C l_ C/t 1. M 30 - r ? OQ - K * m0 r/j T 3 p c O O 3 o r* C - ?T / K '7 0 o' C 0 p n Ci 'CICOIXKJY tOd.f 1936 r^Xr.'S-iT^ wl. 18, no. 8) CAUSATION O f PNEUMOCONIOSIS Recently Jones (9) showed that seri cite was the outstanding common mineral constituent of a considerable series of lungs he analysed. Sericite is a variety of mica with the formula K0 3AljO6SiOi2H0. Its occur rence in nature is widespread but the quantities actually found are much less than those of quartz. I t has not been shown that sericite, without quartz, will produce silicotic pathol ogy; all investigations along such lines have been negative. Asbestos is the only silicate at pres ent recognized as causing pathology which is definitely and distinctly dif ferent from that due to silica alone. The condition known as asbestosis, like silicosis, predisposes to tubercu losis but to a much less degree. Since, however, asbestos is handled by far fewer persons than are dusts contain ing free silica, asbestosis is much less common than silicosis. Asbestos is not a true mineral but is a name applied to any mineral which is easily separable into more or less flexible fibers. In this country, the commonest asbestos is the fibrous va riety of serpentine in the form of the mineralchiysotile, 3MgO 2SiOt 2 H / \ Other silicates such as talc, 3MgO4SiOi-HiO, which resembles asbestos chemically, shale, kaolin, AljOj-2SiOi2HjO, feldspar, and pure mica have been studied in both the field and the laboratory. The pathology they pro duce is much less significant than that from quartz and the fibrosis rarely is disabling. Cation.--An extensive examination of coal miners' lungs was made by Cummins and Sladden (10) as the re sult of which they wrote that "coal is only retained in large amounts when there is a really high silica content'' and "we believe that in the absence of the silica factor there would be, under modem mining conditions, no serious degree of anthracosis.. . Men who were engaged in trimming coal ships with virtually no quartz exposure but undoubtedly with very heavy dust exposure, showed some fibrosis but it was not considered disabling (11). The study made by the U. S. Public Health Service (12) in the anthracite mining district of Pennsylvania adds much weight to statements quoted from Cummins and Sladden, namely, that the harmfulness of a coal dust varies with the silica which contami nates the coal. Haldane considered that coal dust might even reduce the severity of a quartz dust exposure; he suggested actually blowing coal dust into a mine with high quartz content as an anti dote for the quartz dust (13) but no serious attempt apparently was ever made to test the validity of Haldane's claims. The recent statistical analy sis of lungs autopsied in the Pittsburgh district (14) shows beyond doubt that city air, contaminated by an unusual amount of coal dust, does not produce a disabling fibrosis. Many of the lungs were markedly pigmented but the pathology found was not, in gen eral, significant. Calcium and magnesium carbonates.-- , These substances occur in nature as the minerals calcite, CaCOj, magne site, MgCOi, and dolomite, CaCOjMgCO. Limestone and marble con tain high percentages of calcite while the bulk of the rock from which cement is made consists of these carbonates. All three minerals are a great deal more soluble in water and in body fluids than .JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY 1 0 * . If, nc. 8] is quartz. Furthermore the solubility of all three substances increases greatly if the solvent is saturated with carbon dioxide, a condition which occurs m the lung fluid which wets inhaled duet. The several studies which have been E stimation of D ust E xposure The effect of any inhaled dust varies more or less directly with the duration of the exposure, the dust concentra tion and the volume of air breathed. In the case of the gas, carbon monox ness Mavrogordat Bloomfield and I.' tions of necessity and use only figun ness. T he Value of made on calcium carbonate dusts indi cate that the dusts are not harmful probably because they are so readily dissolved (8). , ,,,, Gypsum.-- 'This mineral, CabtV 2HjO, is very common and is mined and milled all over the civilized world. ide, our knowledge of the relationship of these factors is sufficiently exact to permit the use of a simple rule (16) for predicting the effects of breathing various gas concentrations under vari ous conditions. Unfortunately, one cannot estimate or predict the seventy The purpose of make possible thy tion of dustines- re1 a precise measure tion. Conditions almost from, mono It is an essential ingredient of ordinary of dust exposures with any such nicetj. plaster and is now used extensively as In cases where men work for a num a wall board. When partialh de ber of year? at different jobs with du- E x c M f - E r . r M r : hydrated it again takes up water readily, but in neither that state nor fering degrees of dustiness Bloomfield and DallaYalle (17) compute exposures as the native substance has it been shown to be harmful (15). It is an interesting fact that pure limestone (quartz free), dolomite, and gypsum, by averaging dustiness in these various jJbs over the total period in question. In their anthracite coal dust study they found that computations so made Slate picker (cry ' P a tch c r C r y e.ir.-i Mule driver (dry Miner' s laborer (>-. are recognized universally as the dusts agreed well with the results of the phi s- Miner (chamber rr.i:..: safest (hygienically) to blow into sof. ical and x-ray examinations of the Secticn foreman coal mines to prevent explosions. Iron Oxides--'The mining of iron, men. A typical example of their method of computing dust exposure is Totals. r \ next to coal, is perhaps the mining industry in which the greatest number of men are employed throughout the world. The ore generally is hematite, FejOi, but other oxides, and sometimes the sulfide, pyrites, FeS:, are handled on a considerable scale. As a result of the improvements made in machine-tool steel, it is possible today to see iron dust created by work on lathes, drnls, and the like. Yet there are no data to indicate that iron, in the absence of silica, causes pathology in any way comparable to silicosis. However, lungs which have been heavily dusted with iron in any form are generally colored distinctively and were called reproduced in table 2. The advantage of these estimates lies in their simplicity and the fact that they have proven useful in corre lating dustiness with physical examina tions. The error in such calculations is that the effects of dust do not i a n exactly, but only ven- approximately, with the dust concentration and with the exposure. Thus, Mavrogordato (IS) writes that "Lesions of silicosis m a mild degree can be produced in an animal by 30 hr. exposure to intense dust clouds, and one is inclined to suspect that it is intermittent exposure to relatively dense clouds that is the deciding factor in producing the dis ease in susceptible human subjects." After V. CVy ornas ior.ay a. cor:slan t (luring" a gen oral, th on, it l~ a alts of the final ir.dieation of the ; "Thus, as a rr.ea:..esses according n health hazards, it . necessary to arranu tration groups cl cent, i.e., 0 to 5, ' 20 to 40, etc." (S;. ment is consiste:. American data we : . 1 r^ r^ r)30 JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Om, 1 Methods of Sampling the sake of the legal prestige thus gained has its drawbacks, know Dustiness is given gravimetrical!)' of one case where a gasoline motor- i: the dust is to be determined chem driven generator and electric pump ically arid by counts if the chemical determination is especially difficult. mounted on a mine car and hauled bv tractor, with three men in attendance, Thus, lead Ls always recorded in milli resulted in obtaining only four samples grams per cubic meter but dust which may cause silicosis is given in panicles per'cubic foot or per cubic centimeter. Sometimes one may wish to convert one set of readings into the other. If the dust particles are perfectly uniform and of definite shape such as spheres or cubes and of known composition the conversions can be made u itli pn-- ei.-don. In such a case, it docs not matter how dustiness is recorded. But in practice the dust particles are r.iver uniform in size and rarely in composition. Conversions are, there fore, apt to be misleading. For prac tical work, 1 mg. of fine quartz^as collected by the impinger contains 300 million particles (by the light-field in one day. In South .Africa where dust sampling has been done on a scale far bejond anything attempted elsewhere the konimeter and sugar tube both ha\e been used. In England great hopes for the new thermal precipitator have been advanced but the results pub lished so far have added nothing sig nificant to the data already aiailabie from methods which arc less accurate. In Australia several different instru ments including Owens counter ha\e been used while the remits coming from Germany were obtained by filter methods and by a modification of Owens' counter. In our own studies we use several counting technic). ^ A great deal of energy is being wasted in deciding which dust sa... 'me method is best. The rapidity with which new methods are appearing, each claiming unusual points of merit, indicates that standardization Ls un likely. An international agreement cr. a reference standard would be wG- eomed by all working in this fide a; present, such an agreement seems to be far off. different methods according to the problem. There is every reason to ercourage rapici method.'- which a.e particularly applicable to routine con trol and to discourage the widespread use of the impinger technic except for occasional check-ups. The impinger has little to recommend it in control ---- Vvhi'e a light portable ir.strumen*. =ueh as the konimeter, has already proven its value in practice. In the United States the impinger C omposition of Air-I loated technic is most used, largely because D usts our or.lv extensive field data come from the Public Health Service whose workers favor this instrument. If one wishes to compare his results wuth those of the Public Health Sendee he rc.nVtheir technic. But copying Public Health Sendee's technic for It is rarely that one meets exposures to pure silica; generally the dust is a mixture of which the original compo sition either is fixed, as in granite, or variable as in most foundry and mining operations. But the composition of iol. IS. r.a. 1 the dust hreat;.>o seldom the sa:r.<- a-- ' material. If a dust arise- :: comminution of a r substance, such a.~ resulting material stantially the same eraiogical analysis particle subdivision 05 06 cr oe 150 1240 1 10 0 Fi c. 2.--Dut rMsvr ogor dal o' 1. plex materia! like gr the dust then seasamples of differ*:. have very different Many examples composition of airfound in the literal statements but it . the facts generally Thus, in this ecu ixicoLOGY iOct., me legal prestige thus awbacks. We know rc a gasoline motor . and electric pump ne car and hauled by c men in attendance, ling only four samples .i where dust sampling a a scale far beyond .pted elsewhere the ugar tube both have England great hopes nal precipitator have out the results pubc added nothing sig.ata already available iich are less accurate, cral different instruOwens' counter have the results coming .ere obtained by filter v a modification of udies we use several is according to the is every reason to methods which are .cable to routine conurage the widespread er technic except for >ups. The impinger jmmend it in control :t portable instrument, nimeter, has already in practice. of Ais -F loated lUSTS t one meets exposures nerally the dust is a i the original compo sed, as in granite, or st foundry and mining ,, the composition of vol. IS, no. #) CAUSATION OF PNEUMOCONIOSIS 531 the dust breathed from a mixture is seldom the same as that of the parent material. If a dust arises from the grinding or comminution of a comparatively pure substance, such as beach sand, the resulting material must have sub stantially the same chemical and mineralogical analysis in all stages of particle subdivision. But if a com frequently sample and count air-borne dust by the impinger technic and then for chemical and mineralogical anal yses take samples of material which has settled on rafters which will have a quite different composition. To make bad matters worse, samples for mineralogical and chemical analysis usually have not been graded into various sizes. 05 06 07 o e 09 10 II 12 13 14 IS 16 17 16 19 20 21 22 2 3 24 Fig. 2.--Dust control and silicosis in South African gold mines (adapted from MavTOgordato). plex material like granite is ground and the dust then scattered in the air, samples of different particle size will have very different composition. Many examples of the changes in composition of air-borne dust can be found in the literature to prove these statements but it is interesting that the facts generally have been ignored. Thus, in this country, investigators Jones (19) has given indisputable, proof of the carelessness of which most of us have been guilty in recording the composition of air floated dusts. In support of Jones' contentions an in teresting example is given by Drinker and Hatch (8) for foundry dusts. "A good molding sand is made up of about 80 per cent quartz in the shape of coarse particles; the bulk of the re- JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Ocl., 1SSS maining material is clay in the form of fine particles which coat the coarse quartz grains. The chemical com position of the finer fraction (say below 10 microns) of material in foundry sand is markedly different from the composition of the coarse fraction." Thus, the original material contains about 76 per cent quartz, while par ticles above 10 microns have 85 per cent quartz and those below 10 mi crons have only 19 per cent (see table 3). Under the present methods of estimating dust composition and dust hazards a large error obviously would be made, by assuming that the changes in the composition of Barre granite, of 35 per cent original quartz composition, and of various coal-silica mixtures take place on settlement in air. Obviously, changes will occur (probably great changes) but they have not been measured as yet al though we have all welcomed the figures of reasonable dustiness sug gested by the U. S. Public Health Service for the two industries in ques tion, granite cutting and coal mining. Their analyses were all made from samples which had settled out on raft ers, and no samples were separated into various particle size fractions. TABLE 3 C omp os i t i on of C o a r s e and F i n e F racti ons o f U n u s e d F o u n d r y S and ( Co n t a i n i ng N atural Bond) _____ CONSTITUENT CumuuSvibic........... HjSiF soluble ( c l a y ) ................................. Residue (quartz)....................................... Total. PERCENTAGE BT * EIGBT Total f.imple >10 2.3 0.7 5.5 1 6 16.0 12 7 76.3 85 0 100.0 ICO 0 CIO# 12.7 30,5 37.5 19.2 100.0 original material represented the fine air floated dust. " Another example is given by Jones (19) from the South African "banket" --large crystals of quartz held together by fibrous serieite. In figure 3 are illustrated the changes in dust com position which he noted as the dust was allowed to settle, as it would in practice. Obviously, the quartz con tent decreases as the serieite increases. Jones remarks that "when a wall built of quartz boulders is pulled down, the bulk of the dust comes not from the quartz boulders but from the mortar." It would be interesting to know what Particle Size It is well known that in silicotic lungs dust particles under 3 microns vastly outnumber those which are larger. It has been alleged that the respiratory mechanism, the lungs, and the phagocytes are mostly responsible for this size grading. However, it is easy to show that the size grading is done in the air before the dust is breathed and not later in the human body. That is, we find an excess of small particles in the lungs simply because that is the way that they oc cur in air. It is physically impossible for any but particles below 5 microns rof. 8, no. 5] to remain afloat ir. be carried about by and to be inhaled, that the alveoli a: Fio. 3 --Sketch. particles at diffrer.15 minutes after bi blasting; and (d) ab Metallurgy.) admit particles 1' crons in length an are occasionally f But the reason tl; lungs so infrequ- CIOOLOGY lOct., 1936 imposition of Barre cent original quart of various coal-silica ice on settlement in changes will occur changes) but they aeasured as yet al- all welcomed the able dustiness sug. S. Public Health o industries in que6ng and coal mining, ere all made from ,1 settled out on raftswere separated into :ze fractions. ,bt S and (Containing BT WXtQBT 0 .7 .6 1.1 VO 0 <10 12.7 30.5 37.5 10.2 100.0 ide Size ran that in silicotic les under 3 microns or those which are i,een alleged that the anism, the lungs, and re mostly responsible ling. However, it is at the size grading is r before the dust is it later in the human we find an excess of in the lungs simply .icles below 5 microns rot. 18, no. 8] CAUSATION OF PNEUMOCONIOSIS 533 to remain afloat in air long enough to be carried about by gentle air currents and to be inhaled. I t is perfectly true that the alveoli are large enough to rarely remain in air more than mo mentarily. Bloomfield (21) has re corded hundreds of measurements of air floated dusts. His average sizes F ig. 3.--Sketches illustrating the increase in the ratio of particles at different periods after blasting m a Witwatersrand gold mine, (o) about 15 minutes after blasting; (6) about 1 hour after blasting; (e) about 2} hours after blasting; and (d) about 3 hours after blasting. (After Jones, courtesy Inst. Mining and M pU llunv.) admit particles 100 or even 200 mi crons in length and that such particles are occasionally found in lungs (20). But the reason that they are found in lungs so infrequently is that they are all of the order of those found in lungs and in phagocytes. Gye and Kettle (22) showed that colloidal silica was extremely toxic and that it could initiate fibrosis. It r mia JOURNAL 0 INDUSTRIAL HYGIENE AND TOXICOLOGY [Od., 1933 ... claimed ( ccasior.sliy that the dam* ;;"p done Lv q'.iartz particles is due enlirtiv to those which approach the colloidal in size. Usually particles possessing colloidal as distinguished from crystalloidal properties are con sidered to be less than 0.1 micron in size. All colloidal particles are so small that they can be measured only uUra-microscopically. There is no evidence indicating that appreciable or significant quantities of ultra-microscopic quartz can be made bv any known process of grind ing or comminution, including blast ing. In fact, the difficulty of prepar ing even small specimens of quartz ,,low 0.5 microns is considerable. Furthermore, there are no published data indicating the relative potency ,,f quartz particles in various sizes be low 3 microns. Under the circum stances, then, there is no good reason to blame colloidal particles as the in itiators of the silicotic nodule when it has been demonstrated again and again that such nodules can be pro duced by 'articles approximating tr.e common bacteria in size. Standards of Dustiness Under one name or another the plant or mine manager .always wants an objective for his dust control pro gram. It serves no uscuui purpose to evade the issue on the ground that precise figures are not available. Probably they never will be. The practical man argues, very properl}, that if dust is the cause of silicosis must be some degree of dustiness or of air cleanliness which is safe. Having been told that silicosis is a pects of the physician or hygienist some objective of air cleanliness, call it by whatever name one likes. In this country the U. S. Public Health Service studies have furnished the only published data we have from which we may suggest dust standards. In the case of Barre granite it was pointed out that a dustiness of 10-20 million particles per cubic foot was reasonably certain not to cause dis ability. The coarse dust, in this case, contained about 35 per cent quartz. In their recent anthracite coal study the Public Health Service found that counts o! 50 million 'per cubic foot, with 5 per cent quartz in the coarse dust, seemed saie. In the ca.se of pure quartz Cum mings (4) suggests a figure of 5 mil lion particles per cubic foot which is not far from the South African figure of 1 milligram per cubic meter (fig ure 3). We have then 50 million for dust with less than 5 per cent quartz and 5 million for pure quartz. It is very questionable i: one has any r.glit to interpolate for the quartz percentages between 50 and 5 but the figures certainly invite such inter polation. These standards do not answer the question of the plant which handles dust of r:0 proven pulmonary signifi cance. What standard should the manager of such a plant take as his objective or need he take any precau tions at all? Vve cannot give him any standards but we can only suggest that Le investigate one of the many plants which has reduced dustiness without waiting for any physiological justifica tion. Generally the manager and workmen of a clean plant will uphold eloquently the advantages of dust ic-i. l, no. S, It Is only in mm' ness and sllmo-m ! routinely over a There they realii-: dustiness would : properly unless : corded routinely, suits of their pr-e Chairman of tht Medical Bureau i:. "No `New Rand .' tered the industry i.e. 10J years ago, :. silicosis. Them : that the engi-v. : measures which . against silfio.-is : . significant ci` g. O' be hard to do-. i-< a complete proof <: t sampling and c; d . Th e various causative 1 Ze n k e r , F. A ' krani, he itor. Arch, f km. ' : 2 Internat' ...o I :. (sup: crr.cr.t 3. American Pur.!.Report (joint Pt.iurr.octni Ucn Standard Po tior. of O. P. H. A. Year h 4. Saranac Sym; . Employers' M v 1936. 5. Wa tk ins- P itckf : of the Sooth Air the changes po : tive and adrrur.s' J o c r ., S, 109 . IS C'. T h o m p s o n , L. R cf workers ir. . _ ien or hygienist ir cleanliness, call c one likes, the U. S. Public ies have furnished lata we have from st dust standards, re granite it was lustiness of 10-20 r cubic foot was not to cause dis dust, in this case, , per cent quarts, hracite coal study h Service found million per cubic ent quartz in the . safe. pure quartz Cum a figure of 5 milubic foot which is outh African figure . cubic meter (fig* y'" '\ then 50 million for i 5 per cent quartz r pure quartz. It jle if one has any ite for the quartz .n 50 and 5 but the invite such inter- do not answer the ilant which handles i pulmonary signifiandard should the a plant take as his he take any precaucannot give him any can only suggest that ... of the many plants d dustiness without liysiological justifica- the manager and an plant will uphold advantages of dust CAUSATION OF PNEUMOCONIOSIS It is only in South Africa that dusti ness and silicosis have been correlated routinely over a considerable period. There they realized at the outset that dustiness would not be controlled properly unless measured and re corded routinely. Concerning the re sults of their procedure, Irvine (23), Phairman of the Miners' Phthisis Medical Bureau in 1934, stated that "No `New Rand Miner' who has en tered the industry since August, 1923, i.e. 10 years ago, has as yet contracted silicosis. These facts demonstrate that the engineering and medical measures which have been directed against silicosis have achieved a very significant degree of success." It would be hard to devise a more eloquent or complete proof of the advantage of dust sampling and of dust standards. Summary The various pneumoconioses and their causative agents are discussed. Silicosis and asbestos are definite dis eases; in anthraco-silicosis and various silicatoses one sees modifications of normal lung conditions. The effects of carbon, or carbonates, of gypsum and of iron oxides are also discussed. Methods of estimating dust ex posures of a workman includes the taking of dust samples from the work place and interpreting the results dur ing the man's total period of exposure. Errors which have been made from estimating the composition of dust from samples which have settled upon rafters instead of using samples taken from the air, are emphasized. Permissible dust concentrations need not exceed 50 million particles per cubic foot for dust with very low quartz content or 5 million for pure quartz. In defense of the use of standards of dustiness the experience in South Africa where such standards have been applied successfully for many years is cited. BIBLIOGRAPHY 1. Zenker, F. A.`: UeberStaubinhalations- krankheiten der Lunge. Deutsch. Arch. f. klin. Med., 3, 116 (1867). 2. International Labour Office: Silicosis (supplement). Geneva, 1930. ^ _ 3 American Public Health Association: Report (joint) of the Committee on Pneumoconiosis and the Committee on Standard Practices in Compensa tion of Occupational Diseases. A. P. H . A. Year Book, 1933, p. 100. 4. Saranac Symposium on Silicosis, 1935. Employers' Mutuals, Wausau, Wis., 1936. . 5. Watkins-Pitchford, W.: The silicosis of the South African gold mines, and the changes produced in it by legisla tive and administrative efforts. T his J our., 9,109 (1927). 6. T hompson, L. R., et al.: The health of workers in dusty trades. General statement and summary of findings. U. S. Pub. Health Bull. No. 208 (1933). 7. Badham, C.: An investigation concern ing ventilation and the sandstone dust present in the air of certain sewer tunnels under construction at North Shore, and in other sandstone work ings. Rept. Dir.-Gen. Pub. Health, New South Wales, 1924, p. 52. 8. Drinker, P., and H atch, T .: Indus trial dust. McGraw-Hill Book Com pany, Inc., New York, 1936. _ 1 9. J ones, W. R .: Silicotic lungs: the nun- erals they contain. J. Hyg., S3, 307 (1933). 10. Cummins, S. L., and Sladden, 8. F .: Coal-miner's lung: an investigation into the anthracotic lungs of coal miners in South Wales. J. Path. Bact., 35, 1095 (1930). 11. Colub, E . L., and Gilchrist, J. U : r> m r N A L OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Oct.. TM Effects of dust upon coal trimmers. T i n s Jock., 10,101 (192S). _ Saters, R. R., et al g Anthraco-eWi- cosis among bard coal miners. L . >- Pub H ealth Bull. No. 221, (193o). ',3 H aldane, J. S.: The avoidance of sili cosis with dry methods of working. J. Chcm. Met. Min. Soc. S. Africa, SO, m (1929), Abst. a t length in T in s J o r a . , IS, "7 (1930). 14 Sciinurer , L., Allison, W. C., B olc ek , C. M., and H a t t b o r n , S. R . i P n e u moconiosis in the Pittsburgh district, based on a study of 2,500 post mortem examinations made in Pittsburgh hos pitals. T his J ocr., J ' , 29-4 (1935). i r K , udell, A. R.I Clinical investigations into the effects of gypsum d u s t Canadian Pub. H ealth J . is. 14 < (1934). ^ . ;r,. H enderson, A'., and H aggard, H A Noxious gases. Chr-mmn! Cataiog Co., New York, 192,. 17 B l o o m f i e l d , J. J., and D allaA a l l e , J M The determination and control o f 'industrial dust. U. S. Pub. H ealth Bull. No. 217, 1935. N M ggordato. A.: Aa'ue of t.,e ko- ` Dimeter, being an investigation into the m ethods and results of dust sam pling as at present practised in the mines of the AYitwatersrand. S. African Inst. Med. Res. No. 17, p. 4a, 1923. . . 19 J o n e s , AY. R.i Silicosis. In st. Min. and M^t., 42d session, London, 1933-1934. 20 C oo k e ', AY. E g Modern views on sili cosis. J. Hvg . 55, 207 (1935). 21 B l o o m f i e l d , j . J.: T h e size-frequency of industrial dusts. U . S. Pub. Health Reptsi-, +5,901 (1933). 22 Gte. AV. E., and K e t t l e , E. IL: Si.!i- cosis ur.d miners' phthisis Brit. J. Exp. Path S, 241 (1922J. 23 I rvi ne , t G : Miners' phthisis. J. Cl. emA M \j;n See , S Africa. P. .>:4 '19341 CLINICAL f-om :Kt .AVo n C. - T h e r e am which may of pneur..' been termed i:.` r The deterrr.ir.atn : mached by p.cb . of the lur.c> o? ti.1- R eview ok A:,." The study t.y lion has been pc it provides 3. IV the effect oi a p ing tissues 9t' ,j ' effect c: :'irr.Pa dusts. Ti. e white rats keys, fowl rci*.. perirr.erP.s, i ac y' The met hccitd 1. Dusii: -- posing the ex; "high cor.centr.it: : or 12 Lilhon ; art: air, dark-field) to effects in short Received f-,r ; j Read before pC.< Tercentenary Ceh : ' ' posium on "The Er.vv upon Man," Harm : Health, Boston. AycWhen presented. : trated by lantern s : : kicology [Oct., m e . J., and D allaVallx, termination and control lust. U .S . Pub. Health . 1935. , >, A.: Value of the ko- ig an investigation into ,\nd results of dust saro- uresent practised in the .he Witwatersrand. 8. Med. Res. N o. 17, p. 45, Silicosis. Inst. Min. and /ion, London, 1933-1934. Modern views on silig,, 35,207(1935). ' J.: The sire-frequency lusts. U .S .Pub.Health ,1 (1933). \-d Kettle, E. H .^ Siliiners' phthisis. Brit. J. , 241 (1922). : Miners' phthisis. J. Min. Soc., S. Africa, S9, r> CLINICAL ASPECTS, DIAGNOSIS AND TREATMENT OF PNEUMOCONIOSIS* ' W. I rving C lark From the Norton Company, Worcester, and Harvard School of Public Health, Boston, Mass. THERE are two types of dust which may cause some degree of pneumoconiosis; these have been termed inert and active dusts. The determination as to whether or not a dust is active or inert has been reached by pathological examination of the lungs of those dying of pneumo coniosis, by clinical studies, especially x-ray, and by animal experimentation. might be called the normal breathing method. 2. Injection of suspensions of dusts. --This consists in injecting suspen sions of dusts into various parts of animals to detect the capacities of different dusts to provoke reaction in the tissues. Results are obtained more rapidly than by dusting but do not correctly show the natural developmenfof disease in the lungs. R eview of Animal E xperiments The dust suspensions may be intro The study by animal experimenta tion has been particularly valuable as it provides a method of determining the effect of a given dust upon the liv ing tissues and a comparison with the effect of similar exposure to other dusts. The animals used have been white rats, rabbits, guinea pigs, mon keys, fowl, cats, and, for some ex periments, tadpoles and fish (1, p. 44). duced into the animal by: 1. Intratracheal or bronchoscopie injections. 2. Intraperitoneal injections (Mil- ler-Sayers method (2)). 3. Subcutaneous injections. . 4. Intravenous injections--showing the effects of the dust on the extra pulmonary viscera. 5. Intracutaneous injections--for The methods used have been: gross reaction. 1. Dusting.--This consists in ex 6. Intra-lymphatic injections--for posing the experimental animal to a reaction of lymph node cells (3). "high concentration of dust (up to 10 All animals tested either by dusting or 12 billion particles per cu. ft. of or by injection showed a tissue reac air, dark-field) to produce maximum tion to silica. This reaction was typi effects in short time." This method fied by the formation of fibrotic Received for publication June 24,1936. Read before the Harvard University Tercentenary Celebration, 1636-1936, Sym posium on "The Environment and its Effect upon Man," Harvard School of Public Health, Boston, August 27, 1936. When presented, the paper was illus trated by lantern slides showing x-rays and specimens of pathological conditions. nodules except in the cold blooded ani mals where there was necrosis followed by 6ome fibrosis. Changes in sus ceptibility of animals to tuberculosis as a result of the effects of various dusts have also been studied, and the 537 r\ 53S JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Oct., 9SS activating effect of silica demon strated. The effect of the inert dusts upon the animal tissue was found similar to that of anv foreign body. There was reac tionary enlargement of lymphatic nodes, slight fibrotic reaction imme diately surrounding the injected dust but no continuation of this fibrosis and no formation of nodules. The exact pathology noted was scattered or clumped cells containing the inert dust hung in the alveoli, slight inflam mation or no inflammation of the adjacent walls, a slow accumulation of dust-containing cells in the lymph nodes with enlargement of the nodes, and a deposition of dust about the lymphatics of the lung or pleura. When inert substances were injected intravenously, intraperitoneally _or subcutaneously, there was no reaction beyond that of any foreign body (2). As a result of such experiments which have been repeated in many parts of the world, it is believed that of all suspected dusts only silica has a specific action upon animal tissue which results in fibrotic nodulation. .Asbestos fibres produce a peculiar re action in the lung which is different from silica. Following the inhalation cf asbestos dust there are for "cuffs of more dense connective tissue about the terminal bronchioles" (1, p. 46). Contraction and collapse of the alveoli supplied by the affected bronchioles occurs. This is followed by induration and fibrosis of the col lapsed alveoli, presenting the picture of diffuse fibrosis of parts of the af fected lung with persistent foci oi normal air spaces. S ilicosis The Committee on Pneumoconio sis and the Committee on Standards of the American Public Health Associa tion (4) adopted in 1932 the following definition: ``Silicosis is a disease due to breathing air containing silica (Si02) characterized anatomically by general ized fibrotic changes and the develop ment 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 tu berculosis, (some or all of which symp toms may be present) and by charac teristic x-ray findings." I. Pathology of Silicosis Dust particles after reaching the lung alveoli may remain quiescent for a considerable period as is the case with the inert dusts, or they may pene trate the lymph spaces in small num bers. The bulk, however, are phagocytosc-d, that is engulfed, by wandering endothelial cells which at first, lining the wall of the alveolus, become de tached, and then, having taken up the dust particles, pass by ameboid move ment through the walls of the alveolus int.. the lymph spaces. The cells now sio .iy nugrate to the minute lymph islands which guard the entrance to the small lymphatic vessels, pass through these, thence to the lymph vessels, and finally are caught by the large group of lymphatic glands which form part of the hilus or root of the lung. These wandering cells are com monly called dust cells. The piling up of cells and the reac tion of the glands blocks the free circu toi. 18, no. S] C L IN lation of lymph ^ lend to move bo' roots, blocking tb later the minute ! guard the entrant sels. The dust e by the silica d. the silica dust for neighboring t l the tissues to sib of fibrous tis-ue. forms along t b which accompany the lung, invar!-the lobes, arm s; the lung ti.-'U" masses of lymp: fibrotic nodules a: on, increase m extent that, com! . tissue of the for:, conglomerate ma are formed, block, of the lungs. T. Ivmph flow towar the spread of cm-' and eventually lc.. structure. The fibrotic no of silicosis. It L- .' aline mass surrou' normal lung. It mm. in diamet1'. of these noc-'-scopic foci of ccm 146). This increasing tissue obliterates ' vokes a compeers the alveoli elsewb of enlargement is As the amount of ent to permit t. carbon dioxide inn vol. 18, no. 8] CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 539 lation of lymph so that the dust cells tend to move slowly toward the lung roots, blocking the lymph vessels and later the minute lymph masses which guard the entrance to the lymph ves sels. The dust cells which are killed by the silica disintegrate and free the silica dust for further injury to the neighboring tissues. The reaction of the tissues to silica is the production of fibrous tissue. Thus fibrous tissue forms along ine lymphatic vessels which accompany the blood vessels of the lung, invades the septa between the lobes, and spreads its shoots into the lung tissue itself. The minute masses of lymphatic tissue become fibrotic nodules and these, as time goes on, increase in number to such an extent that, combined with the fibrous tissue of the former lymph channels, conglomerate masses of fibrous tissue are formed, blocking off large portions of the lungs. The blocking of the lymph flow toward the hilus increases the spread of dust cells to the pleura and eventually leads to fibrosis of this structure. The fibrotic nodule is characteristic of silicosis. I t is a small, discrete hy aline mass surrounded by apparently normal lung. It does not exceed 6 mm. in diameter. "Occasionally some of these nodules may show micro scopic foci of central necrosis'' (1, p. 146). This increasing amount of fibrous tissue obliterates the alveoli and pro vokes a compensatory enlargement of the alveoli elsewhere. This condition of enlargement is called emphysema. As the amount of air space is insuffici ent to permit the normal oxygencarbon dioxide interchange of the lungs required by the body, the effort of the heart to pump blood fast enough may promote enlargement of that vital organ. This, however, if it occurs, is a terminal condition infrequently ob served, as the patient usually develops pulmonary tuberculosis or dies of an intercurrent disease before this stage is reached. It must be remembered that only one-fourth of one lung is necessary for life, and that the amount of fibrosis must be enormous to re strict the lung capacity to this extent. I I . Symptoms The effect of the underlying pathol ogy upon the workman is at first too slight to be detected by physical ex amination and the worker shows no symptoms. While there is a patho logical condition present, it is to all intents and purposes harmless, in that if it does not progress rapidly it may not provoke symptoms during a work er's life, or only during the last decade. Even respiratory disease of another nature, such as bronchitis or even pneumonia, may occur with recovery during this period. As the condition progresses, how ever, more and more of the lung tissut is converted into fibrous tissue, and the patient begins to show certain symptoms. He complains of short ness of breath when he goes up-hill and says that he notices his heart beat Qn exertion. He also mentions a cough which is at first dry and infrequent, but which gradually becomes moist and frequent. With the cough he raises scanty, stringy sputum which is some times discolored. The sputum is never large in amount unless he catches coid and develops bronchitis. At this MO JOURNAL OU ,NDUSTR1AL HYGIENE AND TOXICOLOGY {Oc,.. i m stage an attack of bronchitis does not disappear but becomes chronic. Dur ing this period the silicotic may com plain of pain in the chest due to pleu risy or to epigastric pain, anorexia, and morning vomiting. While he is able to work, the victim cannot carry on his usual tasks and seeks lighter cussion note is somewhat flattened without being definitely dull especially posteriorly. Breath sounds have more definite characteristic thinning, the expiration being longer and fainter" (6). With the advent of tuberculosis the physical signs are those of that disease. work. _ Slowly the shortness of breath in creases, the patient has poor lung ex pansion, and his color becomes pale and his lips bluish. At this stage pulmonary tuberculosis is a frequent complication. When this occurs, the cough becomes more severe and continuous, the sputum free and moist, areas of dulness to percussion are noted, r&les are heard ever the chest on physical examina tion, and cavitation may be detected. III. X-ray The most important evidence of silicosis is obtained by x-ray. While a flat film gives valuable information, an accurate diagnosis requires a stereo scopic set of films. In many cases a lateral film is desirable in order to de termine the amount of emph)sema present and the size of the heart. Fluoroscopic examination is of inter est in cases where diaphragmatic ad hesions are suspected or shown on the Tubercle bacilli may or may not be present in the sputum. Many of these cases are able to carry on light work for years before finally succumb ing. Hemorrhage from the lungs oc film. The old classification into first, sec ond and third stages has been recentlychanged to a more descriptive nomen clature. The conditions noted on the casionally occurs. . _ During the early stages when peri vascular, peribronchial, lymph node reaction is present there are only in film are now called: 1. Stage of perivascular, peribron chial, lymph node proliferation. Ir regular exaggeration of linear mark definite physical signs. Irvine (5) de scribes these as follows: 1. Acertain lack of elasticity of the chest wall during movements of respiration to gether with 2. A somewhat reduced air entry, and 3. A characteristic alteration of the in spiratory murmur from the normal vesicular character to a higher pitched or "harshened," thinned and commonly somewhat shortened type, the expiratory murmur although somewhat prolonged remaining fainter than the inspiratory. ings. 2. Stage of nodulation. 3. Stage of fibrosis with conglomer ate masses. 4. Any of above stages complicated by shadows characteristic of tubercu losis. The first is not considered as diag nostic of silicosis as it may occur in persons who are in good health or in a number of pathological conditions which have nothing to do with silicosis. The stage of nodulation is pathog There is little change in these signs nomonic of silicosis but may be con as the disease progresses. "The per fused with films of miliary tuberculosis. roi. 8 t no. 6! C L IN I! The stage of fibr< ate masses may 1 broid phthisis. IV . Di Diagnosis is mad 1. Occupational mated length of c dust and quantity 2. Physical exan 3. X-ray examii. 4. Presence or a1 sis as a complicatk Of these measure are most importa most difficult tie whether or not tut Absence of fever a weight, with abser.' suggesting active r chest, is indicative The absence of t the sputum is ino cases of silico-tubcr bacilli in the sputu: T. P: Silicosis once est;, has a strong ten This appears to be properties of the silt causes this toxic act "Experiments end i. mate tal indicate ' centrations silica . tissue; prolonged s' centrations cause fibrosis" (1, p 46). In spite of the t generally recognizee uble, there is gra velopment of body "Possibly unexplo: silica, electrical i etc., are concerned' ICOLOGY [Oct., 1DS6 -omevhat flattened :itely dull especially th sounds have more i<tic thinning, the onger and fainter" cnt of tuberculous are those of that X-ray rtant evidence of I by x-ray. While luable information, is requires a stereo In many cases a ible in order to de:nt of emphysema -ize of the heart. !nation is of inter diaphragmatic add or shown on the tion into first, sec s has been recently descriptive nomenitions noted on the vascular, peribronproliferation. Ir>n of linear mark- lation. -is with conglomer- stages complicated leristic of tubercu- 'onsidered as diags it may occur in good health or in .ological conditions to do with silicosis, lulation is pathog< but may be conliliary tuberculosis. vol. 18, no. 8] CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 541 The stage of fibrosis with conglomer ate masses may be confused with fi broid phthisis. IV . Diagnosis Diagnosis is made upon: 1. Occupational history with esti mated length of exposure, quality of dust and quantity of dust. 2. Physical examination. 3. X-ray examination. 4. Presence or absence of tuberculo sis as a complication. Of these measures the first and third are most important. Probably the most difficult thing to decide is whether or not tuberculosis is present. Absence of fever and maintenance of weight, with absence of physical signs suggesting active inflammation in the chest, is indicative of simple silicosis. The absence of tubercle bacilli from the sputum is inconclusive, as many cases of silico-tuberculosis fail to show bacilli in the sputum. V. Progress Silicosis once established in the lung has a strong tendency to progress. This appears to be owing to the toxic properties of the silica particle. What causes this toxic action is still in doubt. "Experiments and human pathological material indicate that in high con centrations silica is toxic and kills tissue; prolonged action of lower con centrations cause proliferation and fibrosis" (1, p. 46). In spite of the fact that quartz is generally recognized as relatively insol uble, there is great rapidity of de velopment of body reactions to silica. "Possibly unexplored properties of silica, electrical charge, adsorption etc., are concerned" (1, p. 48). This progressive tendency has been noted by Irvine, Bhme, Russell and others (1, p. 28). The question is not what is the pres ent condition of the silicotic, but how rapidly it will advance and how far. This is a serious problem in industry, for a worker having no symptoms and an early stage pathology by x-ray, may develop a disabling silicosis or a com plicating tuberculosis. It is, there fore, possible for a worker to contract his disease while working for one em ployer and to develop symptoms many years later while working for another. If the work he is doing for the second employer involves exposure to an in ert dust the employer may have diffi culty in proving that this was not the cause of disability. One of the striking differences be tween the effects of the inert dusts and silica dust is the lack of progress of pathology in the former as compared with the latter. Bhme (7) found that silicosis progressed after removal from exposure in 20 per cent of the cases diagnosed as having silicosis grade 1, in 40 per cent of the cases in grade 2 and in practically all the cases in grade 3. The experience of the State of Wisconsin, however, suggests that silicosis detected at an early stage in many cases will not progress if the worker is transferred to non dusty work (8) though the reports of Watkins-Pitchford (9) and Brittoh and Head (10) make this somewhat doubtful. Infection may play a part in the de velopment. In fact, it is the frequent and serious compli_cation_ of silicosis, and of the common infections, pulmonary tuberculosis is by far the most serious. -o JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Ocl., 15S3 r - N .......w , IT. , V Qr-vciop earlv or spiratory tract, the silica .lowly invades r:, i.e~ superimposed ,,unpoonn tthhee ssiilliiccoottiicc fibrosis. . Tiui? Kettle write?, "harmful dusts i: inhaled into the lung may excite to activity a latent tuberculosis infec tion; they may exaggerate an active tuberculosis lesion or a coincident in fection ; and they may render the lung ;.bX to cope with a sup'rimpo.-ed infection'' (11). ^ The course 01 siiuv.-sis with a second- nrv tuberculosis is usually slow and without the usual symptoms of in toxication arT may be carried for warn without serious impairment o! working capacity. While tuberculosis is the most fr these orgaas. Asbestosis `Asbestosis is a pneumoconiosis caused by the inhalation of asbestos dust. It is distinct from silicosis both in its pathology and clinically. As bestos is a hydrated magnesium sili cate containing no ire'- silica but about 44 per cent of com Pin' d suica, 43 per cent magnesium, J/ar.v 13 per cem of water and tracts <; ir;n and nickel (14). 7. Pathology o; AAntons .Asbestos dust differs from other inhalabie dusts in that it exists in thread- other infections do occur. Un the Rand pneumonia is a common cause of disability and death. Pope and Zacks found pncuir.oi.ia occurring with great frequency among foundry workers in Massachusetts. Proske 'nd Savers have confirmed Cummings "hseoverv of fuso-spirochetal organisms ' - - a cause of infection among miners in Richer, while chronic bronchitis with asthma is fairly common (12, p. 4). Co11is and Yule (13) compared the ality experience o OC CUpn- ticnal "group exposed to silica dust with that of the general population, and with that of an occupational group exposed to dust not containing silica, As a remit o' the study, they con- 'em,led that silica is a body poison ; ' Fvr;l . ...ucv cxcrt5 munar v" ho:urious' 'cneeis on the rc- be very small (5 microns or less) but which mav he many microns in length. These dust fibres do not appear to enter the alveoli. Tmy are stopped at th' neck of the alveolus where they are phagocytosc-d or penetrate the t.i..s.s..u..e-s. Acting- s-pecifically or merely as a 'oreign body they become surrounded first by mononuclear phago cytes, later by giant cells and last by fibrous tissue. There is no migra tion in dust cells to the lymphatics ar.d Ivmph nodes as is seen in silicosis. The newly formed fibrous ussue contracts, constricting the nee* of th ^a.veolus so that no air can etuer. o lapse of the a.veolus .o.Io*s and subsequent fibrosis. In this way the lower parts of the Pngs are filled with interstitial fibro- sis and the air space markedly dimm- ot. !S, no. i; CLINICS. ishc-d. A compTis.s may occur in the 1 lungs. Thicucriir.g the lower half o: tn always present. 'I complicating factor n The asbestos fibrcome fixed at the re frequently develops body," the asbesto(15). This is a !o: drical body, golden lucent, often with n dumbbell. Thp?e are found on autop in the sputum. Af.ccur in lungs not dust, the finding " ' diagnostic cf a--l companied by a exposure to as! < ` II. S The symptom? th.ose of silico? pnea. Withth which may or Peis bodies. cases, and n vital cap:'.' .v a: : ' The patient's fa ' look. In advanced c.- out of proportion t' being very severe, a by blueness of the l; by clubbing of th' gers frequently shi from the penetrat; fine spicules cf ash tached from the a.1-1 III. Phyfleet The patient, u : shows loss of Vi : X1C0L0GY [Oct., 1938 e silica slowly invades ving the circulatory us system, the digesidneys and liver, and death through its on one or another of ESTOSIB a pneumoconiosis halation of asbestos t from silicosis both and clinically. Asted magnesium silifree silica but about ibined silica, 43 per nearly 13 per cent sof iron and nickel" , of Asbestosis iffers from other in . ut it exists in threadf h the diameter may microns or less) but y microns in length, s do not appear to They are stopped alveolus where they or penetrate the ecifically or merely they become surnononuclear phagont cells and last by here is no migra to the lymphatics s is seen in silicosis, fibrous tissue cont 'ne neck of the aliir can enter. Coleolus follows and lower parts of the h interstitial fibro se markedly dimin u . 18, no. 81 CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 543 ished. A compensatory emphysema may occur in the upper part of the lungs. Thickening of the pleura over the lower half of the chest is almost always present. Tuberculosis as a complicating factor is not common. The asbestos fibre after it has be come fixed at the neck of the alveolus frequently develops into a "curious body," the asbestosis body of Cooke (15). This is a long, narrow, cylin drical body, golden yellow and trans lucent, often with rounded ends like a dumbbell. These asbestosis bodies are found on autopsy and occasionally in the sputum. As similar bodies may occur in lungs not exposed to asbestos dust, the finding of these bodies is not diagnostic of asbestosis unless ac companied by a definite history of exposure to asbestos dust. I I . Symptoms of Asbestosis The symptoms of asbestosis, like those of silicosis, are cough and dys pnea. With the cough there is sputum which may or may not contain asbes tosis bodies. Hemoptysis is rare. There is loss of weight in the advanced cases, and marked reduction in the vital capacity and in chest expansion. The patient's face has an "earthy" look. In advanced cases the dyspnea is out of proportion to the physical signs, being very severe, and is accompanied by blueness of the lips and occasionally by clubbing of the fingers. The fin gers frequently show "asbestos corns" from the penetration and irritation of fine spicules of asbestos which are de tached from the asbestos in handling. II I . Physical Examination The patient, if an advanced case, shows loss of weight. The chest is emphysematous, and respiration is shallow, expansion being frequently less than 1 inch. The percussion note is one of dull tympany but with no definite dullness. The breath sounds are distant and expiration prolonged. The heart is normal in size, b ut lateral x-ray may show an anteroposterior enlargement. IV . X-ray This shows a fine mottling of a "ground glass" quality over the lower half of the chest. There is often an obliteration of the costophrenic angle and pleural thickening, shown par ticularly in the interlobular pleural on the right. The lateral view may show well-marked compensatory emphy sema. A spot of tuberculosis at either apex is occasional but rare. Still later in the course of the dis ease the appearance is that of a very fine stippling that obliterates most of the natural markings. The pleural shadow is definitely thickened. In some of the advanced cases the heart is enlarged and radiating from it into the lung fields is a series of heavy fi brous bands. This picture has been re ferred to as "porcupine heart." Anthraco-Siucosis This disease occurs among hard coal miners and is commonly known as miners' asthma. It is caused by the inhalation of large amounts of dust consisting of a mixture of anthracite coal and quartz, the quartz coming from the rock in which the coal is imbedded. The pathology consists of a clogging of the lymph spaces with carbon par ticles which invade the upper lobes especially. Accompanying this is a linear or nodular fibrosis due to the r A Ml JOURNAL OF INDUSTRIAL HVGILNE AND TOXICOLOGY |Od., IMi inhaled silica particles. When large areas of the lung are involved there is a compensatory emphysema. 1. Symptoms of Anthraco-Silicosis The cardinal symptom of anthracosilicosis is shortness of breath, which explains the term "miners' asthma." With this there is cough and sputum. The cough may be dry and the sputum scanty but if infection in the form of bronchitis is present, the sputum is muco-purulent and colored with coal dust. As in silicosis, tuberculosis is a frequent complication. The physical signs are similar to those of simple silicosis or of silicosis with infection. Diagnosis is made largely by x-ray which gives a picture very similar to that of simple silicosis. The U. S. Public Health study on this problem (16) suggests that the true lung injury is due to the silica inhaled rather than to the carbon particles. Carbon has been found to be harmless when inhaled in the form of smoke and by animal experiment. Inert D usts I. Pathology The inert dusts are relatively harm less. They may increase the fre quency of respiratory disease when inlialcd in large amounts, but this has not as yet been proved statistically. Workers inhaling these dusts develop a mild fibrosis which follows the course of the lymphatics along the bronchoarterial tree and is accompanied by enlargement of the trachial lymph nodes. This reaction which is very slow, after a number of years may progress to a moderate amount of in terstitial thickening. The pleura may be thickened and there may be dia phragmatic adhesions. These later manifestations only appear after many years of constant exposure to a high concentration of dust. II. Symptoms Caused by Inert Dusts The symptoms of the pneumoconio sis of inert dusts are negligible. If the exposure has been long and the dust discharge abnormally heavy, there may be some dyspnea on moderate working. This is not usually severe enough to interfere with the worker's normal activities and may be caused by degenerative changes of the heart due to advancing age, as much as to the pathology of the lung. There is no evidence that the inert dusts, un less mixed with an active dust, can produce disability. III. X-ray Picture, Physical Eiaminat:on and Diagnosis The x-ray picture is that of peri vascular, peribronchial, lymph node thickening which does not progress. Some diaphragmatic adhesions may show in cases with long exposure to heavy concentrations of dust. Serial pictures fail to show nodulation or the massive areas of fibrosis which char acterize silicosis. The physical examination of those exposed to inert dusts is usually nega tive. In a few cases where there has been prolonged exposure to great quan tities of dust there may be some re striction of chest expansion and signs of emphysema. _ The diagnosis is made by physical examination, occupational history, and x-ray. . A typical inert dust is that of the artificial abrasive, aluminum oxide. This material is widely used in grind- i-oZ. 18, no. <51 CLINK Lng wheels and fc paper, etc. In tie 71,000 tons were so: in the United States The use of alumir, certain amount of of this dust has bee (18) and Simmon.Gardner (19) on animal. In a factory wb sives and grinding factured, Clark has of inhalation of th: years. He believewhich provide pro; the continuous inb abrasive dust extt years of work dorsymptoms or pro.-'ings of crippling fu that the number of tuberculosis docs : the number norms community; and ` wheels made of ar ming this sub.-rtar.' other purposes run pneumoconiosis u removed by exl.au In spite of the fa experimental cv;d< relative harmlcssur an effort should be dust count arour.d per cubic foot of an working conditiomfaetory to the wor. the hazard of respu T reatment oe 1 The only methc the pneumocome,.. Dust in quantity ;. from industry wb o x ic o l o g y (Oc., me licsions. These later nly appear after many it exposure to a high dust. Caused by Inert Dusts i> of the pneumoconioare negligible. If the m long and the dust rmally heavy, there dyspnea on moderate is not usually severe t'ere with the worker's s and may be caused changes of the heart >g age, as much as to if the lung. There is t the inert dusts, un i an active dust, can re, Physical Examina- d Diagnosis ' ( -lure is that of peri-onchial, lymph node h does not progress, natic adhesions may nth long exposure to liions of dust. Serial how nodulation or the .f fibrosis which char- examination of those dusts is usually negacases where there has .xposure to great quanuere may be some re t expansion and signs , is made by physical upational history, and :t dust is that of the ve, aluminum oxide, widely used in grind- vol. 18, no. 1 CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 545 mg wheels and for polishing, sand paper, etc. In the year 1929 over 71,000 tons were sold or used in plants in the United States and Canada (17). The use of aluminum oxide creates a certain amount of dust. The effect of this dus+ has been studied by Clark (18) and Simmons clinically and by Gardner (19) on the experimental fm im nl. In a factory where artificial abra sives and grinding wheels are manu factured, Clark has studied the effects of inhalation of this substance for 25 years. He believes that in factories which provide proper dust removal, the continuous inhalation of artificial abrasive dust extending over many years of work does not produce the symptoms or present the x-ray find ings of crippling fibrosis of the lung; that the number of cases of pulmonary tuberculosis does not greatly exceed the number normally present in the community; and that workers using wheels made of artificial abrasive or using this substance for polishing or other purposes run but slight risk of pneumoconiosis if excessive dust is removed by exhaust systems. In spite of the fact that clinical and experimental evidence points to the relative harmlessness of the inert dusts, an effort should be made to keep the dust count around 20 million particles per cubic foot of air. This will make working conditions much more satis factory to the worker and will reduce the hazard of respiratory disease. T reatment of P neumoconiosis The only method of treatment of the pneumoconioses is prevention. Dust in quantity must be eliminated from industry wherever possible, and in most operations this is feasible. In a few where it is not, protective de vices such as respirators or positive air pressure helmets must be used by the worker. When a worker is found upon ex amination to have lung fibrosis it is wise to keep him at work in a non dusty department. While his lung con dition, if it is due to silica or to asbestos dust, will progress slowly, many years of profitable work are before him un less infection intervenes. As dyspnea increases, lighter work must be pro vided. If tuberculosis complicates the picture and the patient develops tu bercle bacilli in the sputum, he must be isolated from other workers, but even then may be able to do light out door work. In more severe cases where there is temperature, all work must, of course, be stopped. Exposure The rapidity of development of sili cosis and of asbestosis depends upon the amount of dust inhaled and the percentage of free silica (SiOj) or of asbestos in the dust. In men exposed to heavy dust clouds with a high concentration of silica, silicosis has developed in as little as 2 years, but under the usual exposures of mining and of industry where the free silica usually varies from 13 to 35 per cent, the development is slow and symptoms do not appear for 15 or more years. In the case of asbestosis, the de velopment of symptoms is more rapid, 5 to 8 years being the usual required time of exposure. Efforts are now being made to corre late the exposure with the pathology, as shown by x-ray, and with the physi- JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Oct., 19S8 signs. In other words, an effort - heii.g made to determine standards ncrmissible amovin's of dust in the working air for both the inert and the harmful dusts. Such standards will be of the greatest value to industry in its effort to reduce its dust hazard to a minimum. E pidemiology 1. Silicosis The danger of inhaling inorganic dust has been recognized fur centuries, but careful study of the effect of such inhalation was first instituted in South Africa and culminated in the Inter national Conference on Silicosis held in Johannesberg in 1930. In 1933 Van Siclen (20) published an stmate of the health hazard from dust in the mines and allied industries of the United States. In his study he found that of 7722 men examined in the Tri-State zinc-lead district of southwest Missouri in 1927-28, 5704 were classified as negative for lung dis ease, 1362 had signs of first stage sili cosis. 253 had second stage, and 32 had third stage. The remainder showed signs of tuberculosis with or without silicosis. In Butte mines (Montana), of 1018 miners 42.4 per cent showed definite siciis of dust injury to the lungs. In the Lead-Deadwood distnrt mines in South Dakota the sickness rates per thousand for respiratory dis ease was two and a half times greater than in genera! industry, while the tuberculosis rate was almost ten times greater. Grouping the various industries studied, Van Siclen found that in metal mining about 02,22$ workers were ex posed while among those engaged in non-metallic mining or quarrying, 23,665 had a respirator.- hazard. The prevalence of silicosis in the general population was studied by Lanza and Vane in 1934 (21). They cite the following occupations as con stituting a definite silicosis hazard: !. Anthracite-coal and metal min ing, quarrying. 2. Certain manufacturing industries such as potteries, glass works, and plants manufacturing granite, sand blasting. 3. Construction work--rock drill ing. handling sand and grav'd. Their rough estimate of the num ber of workers exposed to silica dust to a harmful degree in the Limed States is upward of 500,000. A careful study of 2,600 granite and foundry workers has recently been made by Pope and Zacks (22) in which correlation of the duration of exposure to dust and the incidence of silicosis was determined. Their conclusions are as follows: 1. In representative groups of both granite and foundry workers in Massa chusetts the frequency of silicosis and of silicosis with tuberculosis was found to be positively correlated with the duration of exposure to dusts containing free silica and to concentration of such dusts in the occupatbnal environment. 1 . .o- - the granite workers exa.r.in . bccsis alone was found in 15.2 per cent and silicosis complicated with tuberculosis in 7.6 per cent. 3. Tuberculosis is the cause of death in over one-third of all granite workers, a proportionate mortality three times that in foundry workers and four times that in all males of 20 years and over. In 1907 Summons of the Miners' Phthisis Committee of Australia re ported that gold miners there who con*'acted silicosis died of tuberculosis ici. <, no. ; CLINIC.1. (23). "The ir.it:..! si by workers in bee: started by a demand r authorities to detent, the excessive mortal:losis which was innrate among the mir.' Russell found an of deaths from tu! Barre, Vermont stud;, granite workers (24 believes that at ha--' those who develop tuberculosis. c Silicosis ... Silicosis with tube r. Asbestcsis . . . . Asbestcsis v, ith tub-:-- J. c. Bridge: R. ; chapter 3. I I Ir.cyii : / The health haz.:t 1 has only been : . The Regulation- Ur dustry In Er.gl-.t.i; ! for only 4 year:. 1 `'Over a numbe' ' not specified! "lb- bestosis report .1 u and compiled m while those from as:. losis numbered 26' Wood and Glovu. b on pulmonary ashec published results c: cases in 1934 (2, cases worked ::. ". According to :. x ic o l o g y [Oct., m e hiing or quarrying, uratory hazard. e of silicosis in the on was studied by in 1934 (21). They occupations as conitc silicosis hazard: oal and metal min* .ufacturing industries 3, glass works, and uring granite, sand- n work--rock drill ed and gravel. -t.imfl.to of the numxposed to silica dust gree in the United of 500,000. . of 2,600 granite and , has recently been J Zacks (22) in which duration of exposure ... incidence of silicosis f ' Their conclusions itive groups of both :ry workers in Msssa.ncy of silicosis and of culosis was found to be d with the duration of s ta in in g free silica and such dusts in the occunt. unite workers examined found in 15.2 per cent cated with tuberculosis is the cause of death in all granite workers, a tality three times that and four times that in s and over. .ions of the Miners' lee of Australia reJ miners there who >sdied of tuberculosis vol. 18, no. 81 CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 547 (23). "The initial studies of silicosis by workers in South Africa were started by a demand made upon health authorities to determine the cause of the excessive mortality from tubercu losis which was increasing at a rapid rate among the miners there.*' Russell found an excessive number of deaths from tuberculosis in his Barre, Vermont study of the health of granite workers (24) and Gardner (25) believes that at least 75 per cent of those who develop silicosis contract tuberculosis. berciilosis is so often associated with asbestosis that it seems probable that the association is more than acci dental". Gardner (1, p. 51) says that many autopsies show a combination of tu berculosis with asbestosis and other silicate dusts but "that surveys of liv ing American workmen show no great excess of this infection", while Lanza (28) in a study of dust conditions in asbestos mines and mills in Canada and in fabricating plants along the Atlantic seaboard found in his study TABLE 1 Silicosis and Asbestosis in Gbeat Britain, through 1934* NUMBER OF AVERAGE OB DEATM TDEATH DURATIONOr EMPLOYMENT Of TEAM Minimus Avens Silicosis............................................................ 261 55.4 60 2.3 34.8 Silicosis with tuberculosis........................... 315 52.5 67 2.0 32.0 A s b e s to s is....................................................... 41 41.0 27 1.5 12.9 Asbestosis with tuberculosis....................... 26 38.0 29 0.8 0.9 j . c. Bridge: Report of Chief Inspector of Factories and Workshops, London, 1934, chapter 3. 11. Incidence of Asbestosis The health hazard of asbestos dust has only been recently recognized. The Regulations for the Asbestos In dustry in England have been in force for only 4 years. Bridge (26) says: "Over a number of years" (number not specified) "the deaths from as bestosis reported to the Department and compiled in 1934 numbered 41 of 126 workers by x-ray that 67 were diagnosed as having asbestosis in some form, but that no predisposition to tuberculosis due to asbestos dust was indicated. Clark and Drinker (29) in summing up present beliefs say that while a secondary tubercular in fection is not uncommon in asbestosis, it is far less frequent as a complica tion than in silicosis. while those from asbestos and tubercu Summary losis numbered 26". (See Table 1.) Wood and Gloyne began their studies 1. Pneumoconiosis is a disease re on pulmonary asbestosis in 1928 and sulting from the inhalation of inor \ published results of the study of 100 ganic dust. cases in 1934 (27). Most of these 2. The two pneumoconioses which cases worked in the same factory. produce disability are silicosis and as According to Wood, "pulmonary tu- bestosis. i 548 JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY [Oct., 19S6 3. The pathology of silicosis is char acterized by the presence of fibrotic nodules scattered through both lungs, and that of asbestosis is characterized by an interstitial fibrosis involving the lower half of both lungs. 4. The symptoms of silicosis and as bestosis are similar, the most im portant being dyspnea. _ _ 5. The most common complication is pulmonary tuberculosis which in silicosis is a frequent cause of death. ' 6. The diagnosis of both silicosis and asbestosis is made largely by a correla tion of history and symptoms with the x-ray examination. 7. The treatment of pneumoconio sis is preventive and symptomatic. 8. The course cf silicosis and of as bestosis is slow but eventually leads to incapacity due either to the dis ease itself or to a complication, fre quently chronic pulmonary tubercu losis. 9. The number of workers exposed to harmful mineral dusts in mining and in industry in the United States has been estimated as 500,000. BIBLIOGRAPHY 1. Gardner, L. U.: Second symposium on silicosis at Saranac Lake, N . Y., 1935. Employers' Mutuals, Wausau, Wis., 1935. 2. Miller, J. W., and Saters, R. R.: Microscopic appearances of experi mentally produced dust nodules in the peritoneum. U . S. Pub. Health Repts., 80,1619 (1935). 3. D rinker, C. K., F ield, M. E., and Drinker, P .: The cellular response of lymph nodes to suspensions of crystal line silica and to two varieties of sericite introduced through lym phatics. T his Jour., 16, 296 (1934). 4. Lanza, A. J.: The etiology of silicosis. J. A. M. A., 101, 583 (1933). 5. Irvine, L. J.: Report upon the work of the Miners' Phthisis Medical Bureau over the year ended July 31, 1928. Pretoria, 1929. 6. Saters, R. R.: The clinical manifesta tions of silicosis. J. A. M. A., 101, 580 (1933). 7. B Ohme, A .:Die Prognose der Staublung enerkrankung (Silikose). Beitr. z. Klin. d. Tuberc., 84, 119 (1933). Abstr. in T his Joub., 16,5 7 (1934). 8. Nelson, H. A.: Silicosis problem solved in Wisconsin. Am. Labor Legis. Rev., *4, 53 (1936). . 9. Watkins-Pitchfohd, W.: The silicosis of the South African gold mines, and the changes produced in it by legisla tive and administrative efforts. T his Jour., 9,110 (1927). 10. Britton, J. A., and H ead, J. R.: Pneu moconiosis, the delayed development of symptoms. J. A. M. A., 06, 1938 (1931). ,U rI 11. Kettle, E. H.: The action of harmiui dusts. Inst. Min. & Met. (London), June 24, 1934. Abstr. in T his Jour., 16, 125 (1934). 12. First Symposium on Silicosis, Saranac Lake, 1934. Employers' Mutuals, Wausau, Wis., 1935. 13. Collis, E. L., and Yule, G. U.: The mortality experiences of an occupa tional group exposed to silica dust, compared with that of the general population and an occupational group exposed to dust not containing silica. T his Jour., 16, 395 (1933). 14. Lanza, A. J.: Asbestosis. J. A. M. A., 106, 368 (1936). . 15. Cooke, W. E .: Pulmonary asbestosis. Brit. Med. J., , 1024 (1927). 16. Saters, R. R., et al.: Anthraco-sili- cosis among hard coal miners. U . 8. Pub. Health Bull. no. 221 (1935). 17. Roush, G. A.: The mineral industry, its statistics, technology and trade during 1934. McGraw-Hill Book Co., New York, 48,9 (1935). 18. Clark, W. I.: The dust hazard in the abrasive industry. I, II, w i H I' T his Jour., 7,345 (1925); 11,92 (1929); and IS, 343 (1931). 19. Gardner, L. U ., and Cummings, D . E.: The reaction to fine and medium sized quartz and aluminum oxide particles. vol. 18, no. 81 CLINICAL / Silicotic cirrhosis of tl Path., 9 (whole no. 54 20 Van Siclen, M.: Heal dust in the mines and of the United State.' of the extent and sevr Min, k Met. E ngin.,' 45(1933). 21 Lanza, A. J., and Van, alenee of silicosis population and its incidence of tubercu Tuberc., SO, 8 (1934) 22. P ope, A. S., and Zack logical aspects of sil culosis. Ibid., St, 2 23. Summons, W. E.: R' phthisis submitted t of the Bendigo H< 1907. 24. Russell, A. E., B T hompson, L. R., > J. J.: The health of xicology [Oct., me of D ost E xposure .ny inhaled dust varies ctly with the duration , the dust concentralume of air breathed, le gas, carbon monoxIge of the relationship is sufficiently exact o of a simple rule (16) ie effects of breathing entrations under vari- Unfortunately, one or predict the severity s with any such nicety. men work for a numlifferent jobs with diff dustiness Bloomfield 17) compute exposures -stiness in these various tal period in question, icite coal dust study computations so made the results of the physexaminations of the al example of their puting dust exposure is able 2. .ige of these estimates .mplicity and the fact proven useful in correwith physical examine or in such calculations 'ts of dust do not vary ly very approximately, concentration and with Thus, Mavrogordato t "Lesions of silicosis in can be produced in an hr. exposure to intense <nd one is inclined to is intermittent exposure ense clouds that is the r in producing the dis.tible human subjects." :ary excesses of dusti- voi. 18, no. A] CAUSATION OF PNEUMOCONIOSIS 529 ness Mavrogordato named dust floods. Bloomfield and DallaValle's calcula tions of necessity ignore dust floods and use only figures of average dusti ness. T he Value of D ust Samples The purpose of dust sampling is to make possible the control or elimina tion of dustiness rather than to obtain a precise measure of dust concentra tion. Conditions may vary greatly almost from moment to moment and arda of dustiness and is in reason able agreement with Mavrogordato's "figures of merit" as obtained by konimeter samples. A great deal of time can be saved by ignoring samples which are obviously too dusty--it is as well to take the sample for a matter of record but it is absurd to work long over it if it is cer tain to be vastly in excess of the ob jective. Mavrogordato dismisses such samples with the laconic symbols "T.M.C." (too many to .count). TABLE 2 Example of Method Used im Determining an Employee's T otal Dust E xposure* OCCUPATION T E A M IN OCCUPATION AVERAOE OUST C O N C E N T R A T IO N , M ILLIONS P E R CUBIC FOOT MILLIONS OP PARTICLE T E A M P E R CUBIC ro o t Slate picker (dry breaker).......................... 2 2 Mule driver (drv m ine)............................... 3 3 3 Section foreman............................................ 5 380 760 71 142 71 213 480 1440 480 7200 7 35 T otals.......................................................... 30 9790 9790 millions of particle years per cubic foot , ... --------------------- ----------------------------------- -- 326 millions of particles per cubic foot 30 years * After Bloomfield and DallaValle. only occasionally are they reasonably On the other hand, it is well to have constant during a working shift. In records which indicate that the en general, then, it is advisable to give the vironment is as clean as is desired. In results of the final estimate with an our own experience the ignoring of such indication of the expected variation. samples has raised difficulties in prov 1 "Thus, as a means of classifying proc ing in court that adequate dust con esses according to their respective trol had been enforced. There is no health hazards, it appears to be un doubt whatever that, in the United necessary to arrange them in concen States at least, dust samples now have tration groups closer than 100 per a very definite place in depicting work cent, t.e., 0 to 5, 5 to 10, 10 to 20, ing conditions to compensation boards 20 to 40, etc." (8). Such an arrange or to a court. Under the circum ment is consistent with the few stances, it is very unwise in making American data we now have on stand- surveys to ignore the clean places. OXICOLOGY [Oct., me nd symptoms with the on. .lent of pneumoconio- and symptomatic. : of silicosis and of asbut eventually leads iue either to the dis a complication, fre- pulmonary tubercu- ,*r of workers exposed icral dusts in mining in the United States ted as 500,000. . and Head, J. R.: Pneu- the delayed development s. J. A. M. A., 96, 1938 ..: The action of harmful . Min. & Met. (London), 4. Abstr. in T his Jour., i). _ um on Silicosis, Saranac f ' ' \ i. Employers' Mutuals, is., 1935. ' and Yule, G. U .: The xperiences of an occupa- ,p exposed to silica dust, vith that of the general and an occupational group lust not containing silica. , 16, 395 (1933). Asbestosis. J. A. M. A., .36). Pulmonary asbestosis. J., t , 1024 (1927). ft., et al.: Anthraco-silii hard coal miners. U . S. h Bull. no. 221 (1935). V.: The mineral industry, cs, technology and trade . McGraw-Hill Book Co., 45, 9 (1935). The dust hazard in the idustry. I, II, and III. .7,345 (1925) 11,92(1929); , (1931). U., and Cummings, D . E.: m to fine and medium sized aluminum oxide particles. vol. 18, no. 8] CLINICAL ASPECTS AND DIAGNOSIS OF PNEUMOCONIOSIS 549 Silicotic cirrhosis of the liver. Am. J. Path., 9 (whole no. 54) 751 (1933). 20. Van Siclen, M .: Health hazard from dust in the mines and allied industries of the United States--Initial survey of the extent and severity. Am. Inst. Min. & Met. Engin., Contribution no. 45 (1933). . 21. Lanza, A. J., and Van, R. J.: The prev alence of silicosis in the general population and its effects upon the incidence of tuberculosis. Am. Rev. Tuberc., 99, 8 (1934). 22. Pope, A. S., and Zaces, D .: Epidemio logical aspects of silicosis and tuber culosis. Ibid., 39, 229 (1935). 23. Summons, W. 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