Document npK7MgKjaOBNxRyaGDpZ2gR71

THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS* E. R. A. Mebxwxthke, M B. il.lltdual Inrptdor of Pa&ariu INTBODVCTIOW He was treated in the Charing Croat B pital for two months, and then returned RIOR to the commencement of work. After a few months, however, he Pthis inquiry, in February, 1928, became ill again, and waa re admitted to the definite knowledge existed of Hoepitai in April, 1900, where he died. The only two deaths of asbestos workpeorset-mortea examination confirmed the about whom there was expert opinion clinical diagooaia of extensive pulmonary fibroeis. There wae no evidence of pulmo that the inhalation of asbestos dust nary tuberculosis, and examination of the had at least contributed to, if not sputum for B. tuberculosis was negative. caused, the fatal outcome. The first of these, in retrospect the The second case wss reported by Dr. most suggestive, only came to light W. E. Cooke in 1924, eighteen years some years after the occurrence, when later (2): full information was unobtainable. All that is known of this cose, now referred to as "the Montague Murray Case,*' is contained in the evidence given by Dr. Montague Murray before The deceased, a woman, aged 33, who died in 1934, had worked in aebestoa for 18 years, but intermittently for the last 5 years, owing to periods of ill-health. The post-mortem examination revealed, not the Departmental Committee on Com only extensive fibrosis of the lungs, but also pensation for Industrial Diseases in much change due to pulmonary tuberculosis. 1906 (1). From this source, we learn that: The patient, a male aged 33, earns under the care of Dr. Montague Murray at the Charing Croat Hoepitai in the beginning of 1899. Be had worked with asbestos for "some 14 years," 10 years as a eardroom Although Cooke (3) and Stuart McDonald (4) were conclusively of the opinion that in this case the lungs showed a progressive dust fibrosis, to gether with a chronic tuberculous in fection, the etiologic relationship be hand, and tba remainder in some other room of the factory, "where there wae much lees dust." He volunteered that, of the 10 people working In the eardroom whan he went into it, ha was the only survivor, and that all the others had died somewhere about tween the inhalation of asbestos dust and fibrosis of the lungs would have been strengthened by the absence of a tuberculous infection. Cooke's case is, however, of out 30 years of age. There is no note ae to the nature of his work, previous to that in the aebeetos factory. standing importance, not only because* of the discovery of "curious bodies" in the lungs--discussed later--but also, Iteceived for publication Feb. 17, 1930. and of more importance generally, be- 198 J.X.H. Uaj. UM - & t- CD CD V & tv* 3i .* PULMONARY FIBROSIS IN ASBESTOS WORKERS cause its publication again directed attention to the possibility' that inor ganic dusts containing little or no free silica may be productive of extensive pulmonary fibrosis. Of these dusts, the silicates form a very large class, of which asbestos is but one example. Many other members of the class, such as the feldspars, kaolin, French chalk, and pumice, are extensively used in industry. The importance, therefore, of delimiting the potentiali ties of the class as producers of pul monary fibrosis is clear. Cooke's case was the first to be generally reported in the medical press; the facts of the Montague Murray case, although contained in the evidenoe presented before the Departmental Committee in 1906, and published in 1907, were liable to be overlooked in the mass of important material on industrial diseases elicited by that Committee. Since Cooke's case, Dr. I. M. D. Grieve has made a careful study of a group of asbestos workers in his prac tice, and has courteously allowed access to his records. In February, 192S, Dr. MacGregor, Medical Officer of Health for Glasgow, drew my attention to an asbestos worker who was receiving treatment in one of the hospitals in that city. This case, the details of which have been reported by H. E. Seiler (5), pre sented, both clinically and radiologically, signs of a diffuse pulmonary fibrosis, with no evidence of a tubercu lous infection. On further investiga tion into the patient's industrial and medical history, no presumptive cause, other than the inhalation of asbestos dust, was found to account for the existence of the fibrosis. This case, at that time the third of which the Factory Department had knowledge, was, however, the first in which the four essential conditions, necessary to establish a relationship between the inhalation of asbestos dust and the development of fibrosis, could be demonstrated. These conditions are:. 1. Work involving exposure to asbestos dust. 2. The existence, demonstrable clinically and radiologieally, of a definite pulmonary fibrosis. 3. The absence of previous or present in fections known to cause pulmonary fibrosis --e^., tuberculosis, faSn****, or pneu monia. 4. The abeenee of previous or present work involving exposure to other dusts, which might cause pulmonary fibrosis. These conditions being fulfilled, a relationship between the inhalation of asbestos dust and the development of the pulmonary fibrosis may be pre sumed. The importance of establishing whether the supervention of this dis ease in an asbestos worker was an exceptional occurrence, or evidence of a grave health risk in the industry, was now apparent, and steps were taken, forthwith, to obtain jrrima fade evi dence in proof, or disproof, of the exist ence of such a risk. A number of workers in asbestos were selected and examined clinically and radiographically. The findings invited further investigation through out the industry, with the result that a comprehensive inquiry involving the investigation of the different processes in relation to the evolution of dust, and the examination, both clinical and ra diologic, of workers, was undertaken during the year 1928, commencing Vol.U K.i tsC'* se-* 200 THE JOURNAL OF INDUSTRIAL HYGIENE with the carding, spinning, and weav ing processes of the industry. In the meantime, in March, 1928, the death of an asbestos worker (one of Dr. Grieve's cases) occurred in another part of the country, and, on post mortem examination, a condition of widespread fibrosis of the lungs, with out tuberculosis, was revealed. The microscopic examination also disclosed the presence of the curious bodies. In 1928, also, Dr. F. W. Simson (6) reported a fatal ease of fibrosis of the lungs occurring in a native work ing in an asbestos mill in southern Rhodesia. In order that this brief survey of the events leading up to the present in quiry may be complete, it is necessary to review the investigation made in 1910 to 1911 by Dr. Collis and Miss Whitlock--the only previous inquiry into the subject. In May, 1910, the Registrar-Gen eral drew attention to a death which had been certified as "acute pulmonary phthisis in an asbestos worker,0 and to a statement (for which he was un able to vouch) that seven other deaths from phthisis had occurred in the same factory. Following this, extensive inquiries were made, a medical report on all the employees in the factory concerned was obtained, and Dr. Collis and Miss Whitlock investigated generally the various processes in the industry with respect to the evolution of dust, methods of ventilation, lost time due to sickness, etc. Also inquiries were made of the Canadian government as to the conditions in the asbestos quarries and mills in that Dominion, ^evidence of increased sickness - and mortality rates among the workers, and any methods of ventilation which had been found of especial value. The result of this investigation did not conclusively prove that asbestos possessed injurious properties, but it pointed to the probability that such was the cose. It is interesting to con sider why it was that no conclusive proof one way or the other could be obtained, then, aa to the injuriousness of asbestos dust. Some, if not all, of the factors which affected the position then are, in varying degree, continu ing factors, and have an important bearing on the present inquiry. Their operation, while providing a solution to this query, also affords an explana tion to another pertinent question: Why is it that this industry, founded In antiquity, has only recently excited attention, by reason of its raw material becoming suspected as a cause of indus trial disease? The answer appears to be that in the past it was not practicably possible to obtain proof of the injuriousness of asbestos dust, considering the limita tions imposed by the state of the indus try, and the point reached by research work into the relationship between dust inhalation and diseases of the lungs. The industry itself, not a large one today, was then (1910) consider ably smaller. Certainly it bad begun to grow rapidly, but the number of workers who could have been employed for a period of time long enough to allow of the development of definite physical signs . of pneumonokoniosis must have been quite small, and dis persed over the country. Precise knowledge of the morbid affections of the lungs produced by the inhalation of dusts was more frogmen- rich did tOS - it ich DD- ive be ess of ion ' uimt eir on ian: ed ed iai 19- r he to -t of a- .9- =h ?n ie ;e r- v )' in >f d ;o o ia 9- d' lO l- PUU10NARY FIBROSIS IN ASBESTOS WORKERS < 201 tapy than it' is today. The position w.-!; dearly stated two years later in evidence placed before the Royal Com mission on Metalliferous Mines and Quarries. This Commission, when re porting in 1914 (7), stated "we do not know whether other dusts besides those containing free crystalline silica induce a pathological condition in the lungs, though the experiments of Professor Beattie in animals suggest that this may occur." It is only in the last year or two that research hasproduced some definite evidence aa to the precise effects of some of these dusts on the lungs (8) (9) (10) (11) (12). In 1910, radiography of the lungs, in both its technical arid its interpretative aspects, was still in its infancy and, so far from having attained its present status of being an indispensable aid to the diagnosis of the dust diseases of the lungs, was an unused ally. In addition, the existence of a meas ure of exhaust ventilation In the most dusty processes of the industry, incom plete as it was, had important results in modifying the onset, course, and duration of any pathologic lung condi tions resulting from the inhalation of the dust. This influence has been much more pronounced in the period intervening between 1912 and the present inquiry, and will be referred to again. Another factor which has tended and still tends to obecure the possible deleterious effects of the non-silica dusts, is the general use of the phthisis mortality rate as a comparative index of the degree of injuriousness of the dust encountered in the various dusty occupations. JThis rate, while of great value in separating dusty industries into two great groups--those which show an excess mortality from phthisis, and those which do not--as well as being a comparative index of the in dustries belonging to the former group, not only is of little value as ameans of classification in the latter group, but also tends to distract attention from it, and to result in the associated dusts b^ ing dismissed as more or less innocuous. Evolution of dust is only one factor, though an important one, which may cause variations in the phthisis mor tality rote in different industries. Wages, boun of work, aggregation of workers, amount of food, housing, and other social and environmental condi tions are, however, powerful In the same direction, and are not necessarily comparable as between the workers in any two industries. In thus reviewing some of the influ ences which have retarded recognition of the baneful effects of some dusts upon the lungs, the attributes of pulmonary fibrosis, the most impor tant of the diseases caused by the in halation of dust,.must not be over* looked. This disease, insidious in its onset, stealthily advances with but faint warnings of its progress; inexorably it cripples the essential tissues of the lungs, yet for a considerable period causes almost no inconvenience to the worker. As time goee on, however, the lungs find more and more difficulty in re-aerating the blood; and breathing is quickened on slight exertion. Still the worker is able to remain at work, but is aware of his undue shortness of breath on extra effort. Usually, how ever, he ascribes it to causes other than the dust he is inhaling. As the disease progresses, if no acate illness has caused a fatal termination, s; t ] ?' % >* n. 'cr> 1F*~* * \JD DOW 02176 202 THE JOURNAL OF INDUSTRIAL HYGIENE * stage is reached when the lungs can asbestos dust has a totally different do little more than maintain life; and physicochemical constitutionfrom that r ST006U94I the shortness of breath is extreme. of dusts containing much free silicaand Even in its terminal stages, the disease, causing silicosis. It was felt that deceitful to the last, may masquerade although much valuable guidance as chronic bronchitis, pulmonary tu could be obtained from the methods berculosis, bronchopneumonia, or the of investigation of silicious dusts, care like. had to be taken to keep an open mind, I While more or less acute cases of so as not to be Mnconadousiy biased fibrosis closely simulating miliary in the direction of assuming that the tuberculosis have occurred, even in this effects of the dust, if any, must be com country (13), they have all been ass&> parable in some degree to those of dated with the inhalation of dense crystalline silica. concentrations of free silica dust, and are, fortunately, the exception rather than the rule. The difficulty of diagnosing pulmo Asbestos astd the Asbestos Znbustbt Asbestos nary fibrosis, especially in its early The term asbestos is a collective stages, or if complicated by tubercu name, of no definite mineralogic sig I losis, has been stressed by a number of nificance, which has been applied to a authorities, and has, undoubtedly, con variety of silicate minerals, which differ tributed to impede the attainment of from one another in chemical compo precise knowledge of the extent to sition and physical properties, but which the various industrial dusts which resemble one another in their affect the lungs. finely fibrous feature and flexibility Difficulties and obscurities still im (14). Their value depends on the t pede, though to a less degree than in facility with which they ore capable of the past, any investigation into the being split up into long and flexible effects of an industrial dust upon the fibers, which cun be spun like cotton lungs of those exposed to it; but prior and woven into cloth; on their resist to the War, although there were certain ance to beat and acids; and on their slight indications that asbestos, in insulating properties with respect to * common with some other dusts, heat and electricity. might produce permanent pathologic Varieties of asbestos possess these changes in the lungs, it was not possible qualities in differing degree. Com to obtain evidence sufficient to prove mercially, therefore, selection is made or disprove this hypothesis. by the manufacturer of that variety At the outset of the present inquiry and grade which is most suitable for % into what, if any, pulmonary diseases the purpose in view, regard being paid workers exposed to the inhalation of to ordinary economic factors, such as if t ( asbestos dust are more prone to con the cost of the raw material, and the { tract than the general population, it price which the finished article may be was considered essential to view the expected to command. problem afresh, and with complete Consignments of asbestos of the f detachment, because of the fact that same general variety, but with differ- J.I.H. UH V ent hat md hat nee ods are nd, 3ed the of ive dg0a ffer pobut teir !ity the 1 of ble ton ist.eir to eae >m- ade ety for aid i as the 'be the ter- PULMONARY FIBROSIS IN ASBESTOS WORKERS 203 ent countries of origin, are frequently binod water, and usually more cal mixed in the preliminary processes of cium, aluminium, and iron. Members manufacture. Thus Canadian chryso- of this group are resistant to adds, tile may be .mixed with Russian, or but are more difficult to spin, some Rhodesian chrysotile, and so on. Less being quite unsuitable for this purpose. frequently, totally different varieties, The most important members of this such as smosite and chrysotile, may be group are croddolite, amosite, and mixed. tremolite. Practically speaking, all that goes Croddolite and amosite are mainly under the name of asbestos, in com silicates of iron, the former having a merce, is either fibrous serpentine or a beautiful lavender-blue color, thelatter t fibrous mineral of the amphibole, or being brownish-gray. Both are spun hornblende, group. The former is the and the yam is woven into doth for most important commercially; but various purposes, such as add filter strictly, the mineralogists confine the ing, and for ftiring into insulating TABLE 1.--COMPOSITION OF SERPENTINE AND AMPHIBOLE VARIETIES OF ASBESTOS nvrztuh cboup TABTXTT 810, nSCZIfTlOB OF AlsOi FeO FeOi Com MgO CsO N*0 KtO bined Water Serpentine Amphibole (horn blende) Chrysotile 39-12.5 0-3.7 0.7-4.4 39-43 0-0.35 13.3-16.5 Croeidolite 50.5-52.1 0-1 35.5-37.4 0-3 0.75 1.6-4.5 Amosite Tremolite 48-53 1.2-9-4 34-44 0.7-6.4 0-2.5 2-3.8 57.2 0.9 3.2 22.8 13^4 0.8 0*3 2.4 term asbestos to fibrous forms of horn blende. These two types are sharply distinguishable, chemically and mineralogically. Serpentine asbestos, or chrysotile, is a hydrated magnesium silicate, con taining practically no caldum, a high percentage of combined water, and a low percentage of iron. This variety is very suitable for spinning, but is attacked by odds. Nearly 80 per cent, of the world's production of asbestos is derived from Canada, and is of this variety; the remainder comes mainly from South Africa and Russia. The amphibole, or hornblende, vari eties contain less magnesium and com- mattresses, as well as for other pur poses. Both are produced extensively in South Africa, from which quarter all required commercially is obtained. Amosite, a comparatively recent dis covery, is found there in very large deposits; its use is steadily increasing, the initiul difficulties associated with the manufacture of textiles from this variety having been overcome. Tremolite, found in various quarters of the world, has been mined in north ern Italy since the time of the Romans. Its chief use is in the manufacture of asbestos millboard and for filtering purposes. Table 1, compiled from various DOW 02178 204 THE JOURNAL OF INDUSTRIAL HYGIENE sources, shows the mein differences in the composition of these four varieties. __ Only a very small proportion of the world's production of asbestos, which is between 300,000 and 400,000 short tons per annum, is suitable for spinning, and the most desirable grades of spinning fiber, consequently, command a high price now over 100 a ton. The shortage of this grade has led to improvements in manufacturing proc esses which have enabled less expen sive grades of fiber to be utilised for spinning, sane of which give rise to sn increased amount of dust. About four-fifths of the world's pro duction of ssbestos is fiber unsuitable for spinning, and this is used in the manufacture of asbestos millboard, tiles, sheeting, paper, and many other articles. It is the discovery of indus trial uses for these very short fibers, and the dust-like waste, which has been responsible for the phenomenal expan sion of the industry as a whole. The pinning and textile section has also shared, because of the extensive use of the yarn and doth in the manufacture of steam packings, insulating mat tresses, brake linings for motor cars, fireproof curtains, and the like. In 1880, three years after the dis covery of the large Canadian deposits, tiie world production of asbestos was little over 500 short tons; by 1900 it had risen to about 35,000 short tons, by 1920 to over 230,000 short tons, and by 1925 to over 330,000 short tons (15). The imports of asbestos (all grades) into the United Kingdom rose from 18,591 tons in 1922 to 33,520 tons in -4927 (16). The figures for 1927 refer to Great Britain and northern Ireland only. Of these quantities 8,844 tons and 3,794 tons, respectively, were reexported. Thus the consumption of ssbestos in this country trebled within five years. Th$ Indmtry On considering the uses of asbestos one is astonished, not only at the wide range of artides manufactured from this mineral, in greater or less pro^rtion, but also at the diversity of indus tries which nowadays find its use necessary, either in the form of the raw material, or as manufactured artides. Evidently, therefore, with the multiplidty of processes and dusts encoun tered in the ramifications of the indus try, discrimination would have to be exercised, and some limit set to the processes included in the inquiry. The processes selected may be divided, roughly, into 1. Processes involving the manipulation of asbestos, either pure, or admixed with a small proportion of cotton, or other vege table fiber. 2. Processes involving the manipulation of asbestos together with other dusty a*- terials. 3. Processes involving the snaking up of asbestos cloth into other articles. Group 1 entails exposure to ssbestos dust mainly, and to eotton, or other vegetable dust, very slightly; group 2 entails exposure to asbestos dust in very varying amounts, and also expos ure to divers other dusts, such as brick dust, magnesia, kieselguhr, fossil meal, and cement; in group 3 the exposure to asbestos dust--provided no other as bestos processes are being carried on in the vicinity--is, in the majority of eases, negligible. Processes belonging to all three groups may be carried on in the some factory, and workers may transfer from one department to another (30). J.ta Ur,uu i ty t h f oo o cr> UD CO i I PULMONARY FIBROSIS IN ASBESTOS WORKERS 205 Investigation into the intricate ques tion of the effects of mixed dusts, while possibly productive of some general corollary, would lose much of its value in the absence of knowledge of the effects of the several component dusts, and moreover would introduce an in calculable variable into the final results. For these reasons, and also because the Montague Murray case, Cooke's, Grieve's, and Seiler's cases all occurred in processes included in group X, it was considered advisable to exclude, as far as possible, from the inquiry :Jl workers exposed to the in fluence of mixed dusts, and all those not employed in processes included in groups 1 and 3. The processes included, therefore, are the crushing, preparing, sieving, opening, mixing, carding, spinning, doubling, plaiting, braiding, and weav ing of asbestos, together with the operations incidental thereto. Also included is mattress making, where the filling is asbestos, and the manufacture of some insulating materials, where the dust produoed is asbestos. The carding and spinning processes have many points of resemblance to the corresponding processes in the cotton industry, but with essential modifications and restrictions caused by the different physical characters of the asbestos fiber. These processes are aided by an admixture of cotton, or other vegetable fiber, and usually from 2 to 10 per cent, by weight of cotton is added. More rarely, and for special purposes, long-fibered asbestos is carded and spun with no admixture of vegetable fiber, but usually asbestos yams contain a core of either cotton or metal wire. Asbestos yarns are not only used for the weaving of fabrics, which them selves are used for a multitude of pur poses, but, braided together, are made into ropes for use as steam packings and other purposes. The interstices and center of the rope may be filled with other materials such as talc, oil, or graphite, depending on the precise use to which the rope is to be put. Asbestos mattresses, used for blan keting steam engines, and for other insulating purposes, aremade of asbes tos cloth stuffed with asbestos fiber. The stuffing material may be, however, slag wool, magnesia (containing ap proximately 15 per oent of asbestos fiber), or kieselguhr with a small per centage of asbestos fiber. The man ufacture of mattresses filled with mixtures of asbestos fiber and other materials has not been included in this portion of the inquiry. The shortness, slipperiness, and lack of strength of the individual asbestos fiber, as compared with cotton, flax, wool, silk, and other textile fibers, have been the cause of much technical diffi culty in manufacture.* The efforts of manufacturers to cope with these diffi culties, together with those due to wide variations in the physical properties of the raw material, an reflected in the methods employed byeach. Forthese reasons, and because of the great num ber of patented and special products manufactured, one finds considerable differences in detail In the processes in use. The majority of the processes men tioned result in the evolution of dust, although by no means to the same extent. Difference? in plant, quality of asbestos used, methods of manufac ture, type of finished article, and extent of application of exhaust ventilation, 206 THE JOURNAL OF INDUSTRIAL HYGIENE aft result in variations in the evolution of dust in similar processes in different factories. ..Variations in the evolution of dust in different processes being of outstanding importance, a series of samples of dust from the air of workrooms was col* lected, by means of the Owens jet apparatus. Population at Risk.--A calculation of the total number of workers employed in the processes already enumerated as TABLE 2.--DISTRIBUTION, ACCORD. ING TO LENGTH OP EMPLOYMENT, OF (A) 775 WORKERS ENGAGED IN ASBESTOS PROCESSES AND - (B) SELECTED SAMPLE OF 363 WORKERS 88 24.5 and most probably an overestimate, is 600. Thus, about 2,200 appears to be the total population at risk in this country, for the. purposes of this inquiry. This figure, however, does not include the large number of workers engaged* in the processes in group 2 which involved exposure to the influ ence of mixed dusts, of which asbestos is but one, and commonly not more than 20 per cent, of the mixture. This estimate of the population at risk, although it may be excessive, is useful, since it enables us to judge of the adequacy of the sample of workers examined, and to apply more correctly the incidence rates of any pulmonary affections disclosed by the examination of the sample (30). The sample examined (after eleven cases are excluded of fibrosis and pre* fibrotie conditions due to causes other than the inhalation of asbestos dust) numbered 363, representing 16.5 per cent, of the population at risk, estimated as above. The manner of selection of the sample must be referred to, since just interpretation of the results depends upon a due apprecia tion of the relationship of the sample to the whole population at risk. The principle of selecting primarily thoee longest employed was adopted; but regard was also paid to the other end of the scale, so as to obtain infor mation as to the length of exposure to dust necessary before effects are mani fested, and also as to the particular process in which the worker was engaged. It was felt that, in this way, the information would be obtained in the shortest time. Table 2 shows the distribution, according to length of employment (not necessarily in one factory), of CO Jfc CD CD GO CO i: V CJ1 I t F i a c t t u ii Vc Sc DOW 02181 J? PULMONARY FIBROSIS IN ASBESTOS WORKERS 207 ^iG ^O O iS 775 workers engaged in the processes under review, and of the sample of 363 workers, distributed in the same way. The enormous preponderance numeri cally of workers employed under five years in these processes is striking, as is also the very low percentage of workers employed ten years or longer. Comparison of the two parts of the table shows that the effect of this method of selection is that the number examined in each succeeding five-year employment group is a progressively greater proportion of the total number which could have been examined in each particular group. With a soli tary exception, all those examined were at work on the day of examination. Not only the value, but the neces sity, of radiographic examinations of the chest in investigations into the effects of dust upon the lungs, has been emphasised repeatedly by Watkiruf* Pitchford, and reaffirmed by the Departmental Committee on Compen sation for Silicosis (17). A high standard of radiography is essential; as Watkins-Pitch/ord phrases it, the radiograms must be "technically satis factory." Indifferent films are useless, since it is the fine detail of the lung which is being studied. In a general inquiry, such as this, which involves the examination of workers in factories, large and small, scattered over the country, it is not practicable, nor is it necessary, con sidering the special purposes of the inquiry, for radiograms to be taken of all the workers examined. The dislo cation of work in a factory, caused by the absence of a number of hands for this purpose, cannot be viewed with unconcern, especially when, as is not infrequent, the factory is remote from a center which is equipped with the necessary X-ray plant, and where the services of a consultant versed in the science of radiography of the lungs are available. Furthermore, it must not be overlooked that such examinations are voluntary, and not, as in South Africa, compulsory. Moreover, re peated and protracted examinations only result in the exhaustion of all concerned, and much depends on the willing co-operation of employers and employees, since the only incentive is a desire to further the common welfare. Radiography, therefore, has a differ ent function in these inquiries, than when it is applied to individual cases for compensation or other legal pur poses. This function is not that of replacing careful dimt-al examinations, as has been recently foreshadowed (18, p. 40), but primarily that of being an indispensable aid in diagnosis, especially of doubtful cases, in the determination of complicating lesions, in measuring the extent and progress of the disease, in locating the point at which the earliest radiographic signs appear, and finally as a check upon the human factor presented by the examiner himself. The examinations (except one) were carried out at each factory, in a room set apart for the purpose, suitably warmed, and with the necessary appointments. On occasions the noise of traffic or from the adjoining factory was a hindrance, but in one way or another these difficulties were over come or minimized. All the selected workers were exam ined by the writer. At three factories, however, a number of workers were examined jointly with Dr. E. L. Middleton. His far-reaching experience of the Vrf.tt No. 4 208 THE JOURNAL OF INDUSTRIAL HYGIENE pathologic changes in the lungs, pro these, it diminishes in intensity, but duced by the inhalation of various still persists. In other words, wc find dusts, was of great value, and his tacked on to the paravertebral dulness assistance was much appreciated. an area, above and below, of impaired Every effort was made to complete resonance, which is much more exten the clinical examination of the workers sive than that usually associated with before the onset of winter introduced old inactive hilar tuberculosis. difficulties due to ephemeral bronchitis, Impairment of the percussion note oolds, and influenza, which would tend was found to be constantly more to obscure the main issues. Thus the marked in the right side; infact, at first clinical, and two-thirds of the radio it was thought that in the earliest graphic e.carainations were completed degrees of fibrosis it was confined to by the middle of November, 1828, prior that side, but later, and more extended to the commencement of the influenza observations lead to the conclusion epidemic early in 1829. that the earliest detectable eases are bilateral, although the signs on the left Olznxcax* Exoiowation side are tenuous. Percuttion This change is so constant that it hss been adopted as the most reliable single The inhalation of asbestos dust clinical sign presented by this type of originates changes in the lungs, which pulmonary fibrosis, and no case has may be looked upon as a measure of been classified as fibrotic in its ab the efforts of the living tissues to repel, sence. or incarcerate, the irritant particles of Considering the frequency with dust. These changes modify the per which signs indicating what may be cussion note. It is true that the note termed "enlarged roots" were found in elicited may be similar on both sides, asbestos workers, it may be that para but the note is not normal. It is vertebral dulness is one of the earliest thinner and higher pitched than nor signs produced by the inhalation of mal, and there is a sense of resistance asbestos dust, Indicating congestive imparted to the plexor finger. In changes in the root areas and a choking other words there is a diffuse, but of the lymphatics with dust. Reflex slight, impairment of resonance. impairment of note, due to irritation of This alteration in the percussion the lung tissue by dust, is, however, an note, however, is more difficult to attractive explanation. It does not recognize because it is bilateral, and follow^ of course, that workers present extends over a wide area; consequently ing these signs will ever develop a defi the aid of contrast percussion is denied. nite asbestos fibrosis. It is best elicited by rapidly, and Clearly, the physical signs presented very lightly, percussing the back of the by any case of diffuse pulmonary fibro chest from apex to base on each side. sis not only may be modified by It will be found that the extreme changes produced by some intercurrent apexes remain clear, but below the lung disease, but, oh initio, will vary apexes) the impairment is general. It according to the state of the lungs be increases over the root areas; below fore the onset of the fibrosis. Thus, PULMONARY FIBROSIS IN ASBESTOS WORKERS 209 the fibrosis may be implanted upon a perfectly normal chest, in which case the problem of diagnosis is straight forward. In Qther cases, however, preexisting root changes, so common in an industrial community, may be pres ent, or the lungs may be already the seat of emphysema and chronic bron chitis, or of definite old tuberculous lesions, or there may be a massive pleural thickening, the result of an old pleural effusion. All these examples have been noted in the present investi gation, and others will readily come to mind. Although in most of these cases tire dust fibrosis, if moderate in degree, can be confidently diagnosed, especially* with the aid of radiography, it must be admitted that the problem becomes very difficult when the dust fibrosis is comparatively slight, and the changes produced by other conditions are pro nounced and diffuse. Three types of these cases have caused most difficulty among those examined; fortunately, numerically they were few. The first of these is where the dust fibrosis has been implanted upon lungs already emphysematous. It seems that, at any rate in the case of the asbestos fibrosis, until the fibrotic changes get the upper hand, clinical diagnosis of the fibrosis in these cases is impossible. Nevertheless, although the problem of the diagnosis of a fibrosis implanted upon an emphy sematous chest has caused some diffi culty in this inquiry, it seems likely that it con arise only under exceptional circumstances. The second type of ease which has been a source Of difficulty in clinical diagnosis is that in which there are extensive bilateral fibrotic changes due to healed tuberculosis. That there Is an extensive fibrosis is clear enough, and that most of it is not due to asbes tos is strongly suggested when.examination of the lower portions of the lungs shows that they are comparatively slightly affected. Further help in these coses, of course, may be obtained from the history and symptoms. The third type, also rare, is that in which changes following an old massive pleural effusion on one side so obscure the physical signs of any dust fibrosis as to render that side useless clinically for diagnostic purposes. If the side affected by the pleurisy happens to be the right, the radiographic picture is also curtailed by the normal partial obscuration of the left lung base by the heart shadow. These three types were, with the possible exception of the first, uncom mon, and are mentioned merely to call to mind some of the ways in which an asbestos fibrosis may be masked, in greater or less degree, by changes due to other disease. Only passing reference need be made to the other physical signs found in the asbestos fibrosis, sinoe they do not differ materially from those presented by silicosis. Chest expansion is dimin ished and may be reduced to one-half inch or even less in advanced cases. Retraction of the apexes is common, and sometimes shows a peculiarfeature differentiating it from that found in fibroid phthisis. Instead of the im mobile acd sunken apexes seen in the latter disease, the apexes are seen to descend during inspiration, and to rise again during expiration. This seems to indicate the anchoring of normal apexes by fibrous tissue in the lower portions of the lungs. Some confir- 210 THE JOURNAL OF INDUSTRIAL HYGIENE mation of this was obtained radiologically. Auscultation In the majority of the cases of fibrosis, the respiratory murmur is weakened, much or little, generally, more on the right side, and often still more at the base; the expiratory sound is weaker than the inspiratory, and often becomes less and leas audible as one approaches the bases. Transitionalphases between this and harahened breath sounds and pro longed expiration are not uncommon, even in the same chest. The latter may be notioeable in the upper por tions of the lungs, but progressively diminish toward the bases. Other combinations were also noted, how ever. The dry character of this type of fibre, is during most of its course is rather striking. Scattered fine riles and clicks in the root areas, axillae, and bases were not infrequent; slight edema of the lower halves of the lungs was noted in one of the more advanced cases; but in a number, no adventitious sounds at all were heard. Pleural crepitations, and rarely a slight pleural rub, were noted--these attacks seem to cause little pain--and in one case a little fluid at the right base. No doubt this variability in the sounds heard on auscultation reflects underlying changes, temporary or pennonent, in the lung, and is depend ent, inter alia, on the extent of the fibrosis with its associated pleural thickening--changes duo to past dis ease, catarrh, or other intercurrent affection, and to the degree of compen satory emphysema present. Symptoms The symptoms exhibited by these cases of fibrosis, as might, be expected, closely resemble those of silicosis. The distribution of the main symp toms, and of one sign, cyanosis, which is included with the symptoms for con venience, is given in Table 3. A few cases have been excluded on the grounds that one or other of the symp toms complained of might be assigned to causes other than the fibrosis., such TABLE 3.--DISTRIBUTION OP Font COMMON SYMPTOMS, AND OF CYANOSIS, AMONG CASES OF FIBROSIS imnov % CASES M which s STMPTOK 5 was nestST K n eX No. Per Cent. Cough............................ Cyaaocis..................... Dyspnea........................ Expectoration.............. Pain............................... 91 93 91 91 94 54 59.3 52 55 9 47 51.5 31 34.1 10 1U * 1 Excluding tboM in which the presence of the symptom is referred to other causes. as a complaint of shortness of breath in a case with a past history of mild thyroid intoxication, or of dyspnea associated with obesity. Between 50 and 60 per cent, of the eases complained of cough, or of short ness of breath on slight exertion, or showed some degree of cyanosis, whereas only about one-third com plained of expectoration, and onetenth of pain, or discomfort, in the chest. Also, while 14.6 per cent, of the cases had no complaints and showed no cyanosis, and only 3.4 per /. r'; CO i --! < O 1'. CD i'. co r r CO ? ce w< tv or In of tfc ei ir tr ce fit Pi tr tl s: u a.n a: tc w d fi w h d t! a T ii w e a w C a c V (' a ii PULMONARY FIBROSIS IN ASBESTOS WORKERS 211 cent, presented all four complaints and were cyanosed, 60.6 per cent, presented two, three, or four of the five items. Clearly, none of the four complaints, or the presence of cyanosis, can be an infallible indication of the existence of fibrosis; but the presence of two of them, shortness of breath on slight exertion, and cyanosis in some degree, in an asbestos worker, is highly sugges tive, in the absence of other evident cause. Nevertheless an advanced degree of fibrosis may be present, and little com* plaint made. Symptoms, unless dis tressing, are so often a function of the introspectiveness of the patient. Slight degrees of fibrosis, too, give rise to no symptoms, in the absence of an intercurrent bronchitis, since the remaining sound lung tissue is still amply sufficient for all purposes. Cough was the most frequent symp tom, and was of two types. For a few weeks after, commencing work in a dusty process, asbestos workers often find the dust irritating, and cough while in the dusty atmosphere; this lasts for a few weeks, and then usually disappears. The writer has noticed this effect on himself, but only while in a very heavy cloud of asbestos dust. The dust seems to be only slightly irritant in this way. One or two men who had previously worked in cotton card rooms, or blow rooms, and were affected by that dust, stated that they were unaffected by asbestos dust. Certainly asbestos dust does not cause asthmatic attacks like those seen in eotton card room workers. One man, who migrated from a eotton card room ("hard waste") nine years ago to an asbestos cartTroom, on account of the irritating effect of the dust, does not find asbestos dust irritating, but to this day cannot work with a cotton scutcher (as he occasionally does) with out precipitating a coughing attack within an hour or two. Although he suffers from winter cough and some shortness of breath, he stated that his health has been much better since the change. Asbestos dust, therefore, has only very mild powers as a reflex irritant of the upper respiratory tract, and is, in this respect, comparable to free silica. This is an unfortunate attribute, since it leads to the assumption that the dust is more or less innocuous. The second type of cough is more intimately associated with the develop ment of fibrosis, and occurs, or perhaps is noticed, after a varying number of years'work. Usually it is present only in the morning on getting up, when after rather a sharp attack of coughing, a little viscid sputum "like an oyster" is brought up. A similar bout may occur at night after ceesing work; at times it is sufficiently sharp to cause retching. It is generally rather worse in winter, and may be noticed only then. Although it closely resembles smokers' cough, its features are pre cisely the same in nonsmokers. Persons giving a history of cough dating from an attack of pneumonia or other illness in childhood, almost in variably state that the cough has not become worse since working with asbestos. One worker succinctly de scribed the cough as "firat in the throat; later catches the chest." Generally, this cough causes very little inconvenience and may pass un noticed until the development of some other symptom directs attention to the general state of health. Thus, out of 212 TEE JOURNAL OF INDUSTRIAL HYGIENE #. 6 E- liity-eix cues of fibrosis, in thirty- three (50 per cent) the cough was stated to have preceded the onset of shortness of breath, in twelve (18.2 per cent.) to have developed contempo raneously, and is twenty-one (31.8 per cent) was either not noticed until after the onset of shortness of breath, or, although the latter was complained of, cough was not admitted. Complaints such as "colds go to the chest," and `^frequent colds on the chest," were not uncommon. Com plaint of spitting of blood was excep tional;. and in aQ cases in which tide complaint was mentioned, the exciting cause was, primarily, some disease other than the fibrosis in one, it was due to pulmonary tuberculosis; in another, it occurred only during a prolonged attadc of pleurisy; and in a third, the hemorrhage was gastric in origin. Cyanosis, a valuable sign when present, rarely amounts to more than a duskiness, or slight blueness, of the lips; it contrasts, however, with the general pallor of the face with which it is often associated in these cases. .Cyanosis in some degree was noted in 56 per cent, of the cases. It may be absent even when there is a consider able degree of fibrosis, or it may come and go. Pain in the chest is rarely com plained of, and then it is usually de scribed as "tightness of the chest," "soreness," or "aching." It was noted in 10.6 per cent, of the cases. Well-marked dubbing of the fingers was noted in a few cases. The general nutrition is hardly affected, except in the latest stages. Only ten (10.5 per cent.) were noted as being thin, in Che, the nutrition was very poor; in twenty-one (22.1 per cent.), fair; and in the remainder of the cases, good. Radiography GO --i Radiograms of the chest were ob O tained of 133 workers, or 35.5 per cent, CD of the number examined clinically. CO Of these, over 100 were taken by Dr. E. W. Twining of Manchester, and CD Dr. N. Tattersall of Leeds, and the cn remainder (except one) by Dr. F. L. Henderson of Glasgow. To all three, I am much indebted. Dr. Twining and Dr. Tattersall have devoted many hours to the joint study with the writer of the radiograms, and have drawn freely on their wideexperience of radi ography of the chest in furthering the purpose of the investigation. Dr. R. S. Paterson of Manchester, too, added his experience to a final review of the films, and Dr. E. Barclay, now of Cambridge, lent his assistance in interpreting some difficult films; to both, grateful acknowledgment is made. The standard of radiography was very high; indeed, a high standard is indispensable, if it is desired to trace the cause of such a fine and diffuse fibrosis as that produced by asbes tos. The films are superficially, but only superficially, comparable to silicosis. In the earliest negatives studied with Dr. Tattersall, a characteristic slight obscuration of the lung fields, a general lack of tranalucency, was noted. This appearance, for want of a better term, was denominated as "veiling." Dr. Burton Wood has independently noted (19) and confirmed this, referring to it as the "ground glass appearance." Dr. Tattersall also drew attention to the more or less rounded "whorls" of h l r: J.LE tttr.UW C&M8, e ob* cent. rally. y Dr. . and i the F. L. .hree, *ining many1 filter Lrawn radig the ester. & , .3 ;*-:5 ; - :\X : - J': . ' -.. , * - >;V relay, tones films; nt is ' was trd is trace iffuse isbes- only cosis. with slight -neral This term, Dr. 10ted ; to it nee." on to a" of ua r.uu ; *. .V - * ,.7w** * V* -- / %, . . - Vv <x PULMONARY FIBROSIS IN ASBESTOS WORKERS - 213 varying size seen in the striatioa in the mid-zones in some of the films. There was general agreement as to the. fine and delicate nature of the characteristic mottling. Or. Twining (in a personal communication dated Aug. 2, 1929)--while lamenting that there has been, as yet, neither time nor opportunity to study the changes from every aspect, and therefore his present views may be modified on considera tion of all the evidence--states: la (eaeral my opinion is that tho sarilttt itagM are not characteristic radio* logically, bat that the atage of fine dusty itippling la alaoat certain to be eventually provable ee an early aebeetoe lesion. We aw it constantly in a large eeriee of films, and after a little experience U is quite eesy to detect it. Some of the other easee showed a few grouped lesions, like rosettes or leoptrd markings, each component being about the sits of a primary lobule. These are similar to lesions sometimes seen in tuberculosis. In the asbestos cases I regard them as being groups of primary lobules making up a lobule, the walls of whieh are infiltrated. They certainly teem to correspond in size with the macroscopic lesions seen in the pathologies! specimen. The advanced eases show heavy basal and mid-field mottling!, common in pneumonoconioeis, with a tendency to avoid the apiees. On the whole the lesions are diitinctly Ism dense than those of silicosis, and are lees easy to group into well-defined stages, but 1 think we can recognisa: 1. A very doubtful stage of increased linear stristiona. 2. Fairly definite fine dusty stippled appearance. 3. Coarser mottling with increend linear atnations. 4. Grow lesions with pleural changes and displacements"due to the pull of the fibros ing lesions. The few tuberculous lesions we have come across have been easily distinguishable. The radiographic appearances in the earlier stages are most marked on the right side at the base or in the central zone. This corresponds with the clin ical findings. This preference for the right side has been noted also in silicosis, by the South African ot> servers. The cases showing radio graphic signs of a dust fibrosis have been classified in three broad groups. This grouping, although unscientific, is convenient practically, considering the main purpose of this investigation. Indeed more precise classification based on the particular radiographic changes noted might well be mislead ing at the present time. .. Much combined clinical, radiologic, and pathologic study is required into the whole subject of these fine types of dust fibrosis, which have b itn noted in workers exposed not only to silicate dusts other than asbestos, but also to other inorganic dusts containing no silica, before it will be possible to classify the radiologic changes as has been done so successfully by the South African workers in respect, to silicotic fibrosis. The hypothesis that, because asbes tos dust produces a pulmonary fibrosis with consequent deviations from the normal in the lung skiagram, the de gree and potentialities of this fibrosis can be assessed by comparison of its radiologic picture with those of stand ard silicotic films, is untenable. At least two general types of pul monary fibrosis caused by inorganic dusts can be recognized. A third, representing the purely peribronchial variety of fibrosis, might be added; or it may be that aQ dust fibrosis will be found to approximate more or less closely one or the other of these two Voiu No. I \* hi. co i: * --i o o cr> CO cn ro j ' ji I -vJ i.: 11fJ.V 214 THE JOURNAL OF INDUSTRIAL HYGIENE types. These types ere (1) that pro duced by combined silica dust, on example of which is seen in asbestos fibrosis, and (2) that produced by free _ silica dust, represented by silicotic fibrosis. These two types, while resembling one another in clinical signs and symp toms, differ materially both in the . nature of the lesion produced in the lung, and in the character of the asso ciated radiographic picture. Thus, attempts to weigh, consciously or unconsciously, asbestos fibrosis, or any dust fibrosis other than silicosis, by means of the standard radiographic '* changes found in silicosis, is unsound and is likely to lead to a misconception of the potentialities of the dust in ques tion. Badham (8) gives an example of this source of error in reporting the unex pectedly early death of a man affected with a fine fibrosis caused by an orthodase basalt containing no free silica. Referring to some of the radiologic differences between the fine fibrosis of dusts other than silica and the nodular fibrosis of quartz dust (*.., true sili cosis), he states; Moreover, the eosrse fibroeis of silica fare dear interspaces of normal lung, while the fine fibroeis presented a uniform granular mottling leading to the eonduaion which is probably erroneous that the actual develop ment of fibrous tissue wss greeter in a nodular fibrosis assilicosis than in a general ised fine fibroeis caused by ailieates. To me it appears thst the mechanical damage to the lung is greaher in a fine fibroeis then in s coarse fibroeis when both are well developed. The evidence obtained in the present tDTquiry amply confirms this general statement. On studying the development of asbestos fibrosis as displayed in a series of radiograms, and especially in the few available taken a year or more before a fatal termination, one cannot help asking the question, "What is there here which could have this effect?*' The answer is that the damage to the lung is much greater than it appears to be when judged by the silicotic stand ard. Asbestos fibrosis is much more diffuse; it spins its fine web, as it were, crisscross throughout the lung, enveloping and eventually strangling the ultimate lobular structure, rather than depositing itself in numerous more or less isolated foci, as in silicosis. Thus, at any rate in. the less advanced stages, the radiologic picture of the lesions does not impress the eye, uncon sciously viewing it from the standpoint of silicosis. The radiographic picture may show soft and fairly coarse nodulation, but it is never so impressive as the nodulation in a silicotic film. Paradoxically, the distinctive fea ture, both clinically and radiologic&Uy, of the asbestos fibrosis is its uniformity. The modesty of the symptoms; the unobtrusive, but diffuse, impairment of the percussion note; the homo geneous stippling of the skiagram; all are fragments of an entity, unmistak able when assembled, but enigmatic when divorced. Only two references to the radiographic appearances of the-chc*t is asbestos workers have been traced; one in a report by Fancoast and Pendergrass (10), and the other in as article by Burton Wood (19). Pancoast and Pendergrass together with Miller and Landis examined "IT asbestos workers, 2 of whom showed j.lh. SUy. OH i ST 0064953 it of series e few .'ore a help there eet?" o the irs to ^admore as it lung; Sling ither irons ;osis. need ' the iconx>int show mt it tfioa fea:afly, nity. the nent rno; nil stnkiatic idiot in .ired: and a an tber "17 >wed .r.a. uw < * } . i- -v PULMONARY FIBROSIS IN ASBESTOS'WORKERS . 215 first stage changes and the other 15 definite second stage appearances. Of the men longest at work, one after seventeen yean' occupation showed very definite diffuse, /soft' spots throughout both lunp, and another showed about the same appearance after fourteen years' occupation. Very slight nodular shadows were found in one man after only two years' occupation. Most of these second stage cases showed also well-marked first stage appearances still present, indicating a persistence offree drainage hdumward. In all instances the nodular shadows were characteristically soft' and varied considerably in size." Their first stage appears to correspond with stage 1, and their second stage with stages 2 and 3 mentioned above. It appears from the context that these observers regard asbestos fibrosis as being really a silicosis due to admix ture of free silica derived from the original rock'--a view difficult to sub stantiate. Burton Wood (19) in a series of fif teen niriagramg of asbestos workers notes: "The most noticeable feature of skiagrams of. workers exposed longest to asbestos dust is the presence of shadows suggesting a diffuse fibrosis affecting chiefly the lower two-thirds of the lungs. The fine quality of the shadows is worthy of note. Some of the cases exhibit a 'ground glass' appearance, though on close inspection fine mottling is evident. . . . when more definite mottling is present it lacks the coarse quality described in the skiagrams of chests showing pneu moconiosis, e.g. South African gold miners. . . . . " Clearly, tfie maturation of asbestos fibrosis is spread over a period of years, and by the time the stage is reached when the features discussed above are, in varying degree, positive, and the radiologic picture is recognizable, the fibrosis is not in its inception, nor even in its earliest stages, but is developed and fairly widespread. We must, therefore, recognize an earlier state when the fibrosis is present in slight degree, and also when there is evidence of choking of the lymphatics, and of a measure of pulmonary catarrh. This stage may be referred to conven iently as the prefibrotic stage. The indications of this stage are indefinite, and some, at any rate, not specific. If, however, they con be determined and applied with only a moderate degree of accuracy, informa tion of practical valpe will be available. Efforts have been made, therefore, to distinguish workers in this stage. The following tabulation shows that twenty-one workers out of 363 exam ined (5.8 per cent.) were so classified: Clinical Examination* {363): No. Fibrosis............................... 95 Prefibrotic conditions....... 21 Radiologic Examination* (133): Fibrosis................................ 52 Suggestive changes sot definitely diffuse fi brosis................. 22 Per Coni. 28.2 5.8 39.1 18.5 Many of these cases present a slight diffuse impairment of percussion note --perhaps better described as a slightly increased sense of resistance felt on percussion, mostly of the right lung, at least as contrasted with the left, aad associated with some weakening of the respiratory murmur. Prob ably this early stage could be detected radiographically, but only by means of Vtf.U * li!' iMl' i -a;,i ffc `3. ' 4. i* *j# **'4*^*>**K'-, ^ViCs: m 216 THE JOURNAL OF INDUSTRIAL HYGIENE comparison with a radiogram taken prior to commencing work with asbes tos. By each means the earliest stages of silicosis have been worked oat by the South African observers. There, the radiograms taken at peri odic six-monthly medical examinations can always be oompared with initial radiograms taken before the employees are permitted to work underground. group is dismissed from any further consideration. A general summary of the findings in the 374 workers who were examined clinically, classified under the most im portant lesion, is presented in Table 4. Illustrative Cases The salient points of a few eases are set out below to illustrate and TABLE 4.--GENERAL SUMMARY 07 FINDINGS CLASSIFIED UNDER THE MOST IMPORTANT LESION Iicases OF macro vasmsonc coxninoxa FCUfOKaST tcsaacu- boro gu8 Sol OTXXX FULMOXaST bXSIOMS Ho Sb9 U a a 16 aX s*K <9 3 i o 3 6x 1 s o In 3 i < s s j U 2 o 3 S * Q S| Iss! So 1 J t o < Vk. 1 3 S 1 e Is M 3S-, |a "e = si| fils oa o s ii ii %s H b i s a* a l a 1 *MHbC3 o s i 3 a9Xa0a X 5 1 o-c................. 92 0 3 5 o o 0 0 5-9................. 142 38 1 12 0 i 1 4 10-14............... 89 27 5 3 0 3 0 3 15-19................ 30 15 1 1 1 0 0 1 20 sad over.... 21 17 0 0 0 1 0 0 13 3 5 0 0 7 1 0 1 62 3 5 2 2 72 0 3 2 0 38 2 110 7 1 010 1 Total............. 374 95 10 21 1 5 1 8 Percentage... 100 25.4 2.7 5.8 0.3 1.3 0.3 2.1 21 5.6 13 10 6 3 180 3.5 2.7 1.6 0.8 48.1 * 1 One cut of thickened pleorn due to old gunshot wound. * One cm* of emphysema due to gassing. In other cases included in this group, diffuse weakening of the respiratory murmur was noted, with fine sticky riles in the root areas. At present no stress can be laid upon this group. The clinical changes are so slightly marked that until comparative radiograns are available it would be unsafe to draw any deductions. For the pur poses of this inquiry, therefore, this other features. Five radiograms are reproduced to illustrate the radiologic appearances of some of the cases. There are insuperable difficulties, however, in reproducing the finer changes depicted in the original nega tives. Cass 1.--`This worker, s female, sged 24, bss been employed in ssbeetoe for ten and one-half year*--a a card tenter one year, J.LH. ur. u V l <S> C? cp cn c_n cn t Y st.: ai H Cl pl is in nc rii in rif sk tic er cu as y H eo ali f.. eo pc rif ba ex th pf T1 rw "v SO' of st; SU( err. cai Pr. nx for af. ia : me fee gw eye i per the a. sou vt. No. PULMONARY FIBROSIS IN ASBESTOS WORKERS 217 ST 0 0 6 1956 udui doubler nine and ose~balf years. Her Umily sad personal medics) bistory costsia nothing ofjiote. She has no com* plaints sad feels quite well. Her nutrition go4. She is pole, but shows no eyaaoeis. Che*L--She has s cbcst expansion of 1} aches. No impairment of the peremsion cote is detected. The Ineath sounds in the right lung are weaker, generally, than those in the left. Expiration is prolonged at the right root; no added sounds are heard. A skiagram ehowad some very slight and doubtful change* in the direction of in* creased striation. Caae 2.--This man, aged 24, has been employed in asbeto for five yean, earding and mixing. Previously he worked for four yean in the cotton trade, yarn weighing. His family and personal medical history contain nothing of note. He has had a slight morning cough and expectoration for a year. HU nutrition is good. His eolor U fresh, and there U no cyanosis. Chest.--There is some impairment of the percussion note over the middle third of the right lung, behind, and slightly at the right base. The breath eouods are hereh, and expiration is prolonged in the upper half of the right lung, l* hind; expiration is also prolonged over the left upper lobe, behind. The respiratory murmur is weakened at the right hose, and the breath sounds are of s "whiffing" character. There are no add-l sounds. A skiagram showed enlargement of the right root, and slight haziness and striation in the central cones in both lungs, suggesting early fibrosis. Cass 3.--This man, aged 32, haa been employed in aabeetos for six yean in the can! room, and as a stripper and grinder. Previously he was employed in a cotton card room for nine year*. He had army service for five yean, but was not gassed. He gives s family history of asthma; otherwise there is nothing of note in bis family or personal medical history. He has no complaints and feels quite well. His musculature is very good. His color is pale, but be shows no cyanosis. _ Choi.--There is slight impsdnnent of the percussion note generally, particularly at the right base. The respiratory murmur is s little weakened generally. So added w>unds are detected. A skiagram showed old tuberculin of the lung roots and gen* eral increased striation, especially in the lower half of the right lung, suggesting early fibrosis. Cass 4.--This worker, a male, aged 23, has been employed in asbestos for nine yean, mostly mattress making. Bis family and personal medical history contain noth* ing of note. Be complains of occasional pain in both sides of the chest, and perhaps a little undue shortness of breath on exer* Fig. 1.--Case 4: Moderate fibrosis. Un due degree of striation and fine mottling in central zones of both lungs; calcified glands in roots, with rather coarse striation in upper lobes; ? interlobar pleurisy on right side, tetween the lower and middle lobes; emphysema at bases. tion. His color is normal. His muscula* lure ami nutrition are good. Che-.l -There is no retraction of the apexes, but there is a slight flattening below the right clavicle. The percussion note is slightly impaired generally, behind, panic* ularly on the right side. The breath sounds are weak, generally, and expiration is pro* longed. So added sounds are detected. The skiagram (Fig. 1) shows an undue degree of striation and fine mottling in the central zones of both lungs; calcified glands in the roots, with rather coarse striation in V4. it ,Ve. i 218 THE JOURNAL OF INDUSTRIAL HYGIENE the tipper lobee; ? interlobar pleurisy on the right tide, between the lower and middle lobes; and emphysema at the bases. The ease was diagnosed as moderate fibrosis. Cass 5.--This woman, aged 40, has been employed for eleven yean in asbestos, for most of the period mattress making. Pre, viousiy she was employed in a laundry. She has recently been ill for three months with pleurisy (no history of tapping); other* wise her family and personal medical history moderate fibrosis, most marked toward the bases. Cass 6.--'This worker, a female, aged 31, has been employed in asbestos for seven years, opening, and has been exposed to much dust. Her previous employment was noa-dusty. Her fsmily and personal history disclose nothing of note. She com plains of having had a eough for five yean, and of shortness of breath on hurrying. She is thin and undernourished, and pale. i i v a \ ST0064957 t. } K i Fia. 2.--Case 9: Moderate, but fully developed, fibrosis. Enlarged glands in both roots; diffuse fine mottling in both lungs, especially the right. Fio. 3.--Case 7: General fibrosis, mostly linear, but with little mottling of right lung. Old puerile tuberculous scars at apexes. are negative. She complains of having had a winter eough for three or four years, and of shortness of breath on exertion since her attack of pleurisy. Her nutrition is good; her weight is stationary. She has normal color, and no cyanosis. CAet.--There is some general impairment of the percussion note over both lungs, be hind, more noticeable at the buses. The respiratory murmur is weakened generally. Persistent crepitations and medium rales are noted low down in the right axilla. A skiagram showed diffuse fine stristion and fine nodular mottling, with light opacity at the bases. The case was diagnosed as Dust is present on her hair and in her nostrils. Chest.--She has s chest expansion of one- fourth inch. There is slight general impair ment of the percussion note, definite at the apexes and the bases. The breath sounds are weak; expiration is slightly prolonged. Ho added sounds are heard. Her heart is not enlarged, and no murmurs are detected. The skiagram (Fig. 2) shows a number of enlarged glands in both roots, and a diffuse fine mottling in both lungs, especiaiiy the right. This is a case of moderate, but fully developed, fibrosis. Cass 7.--This woman, aged 48, has been ;.lh. Har. ISX trd the nd31, * seven md to ayment crsonxl m corn- m-ying. id polo. it h, mostly shtlung. exet. d ia her .a of onad impairite at the h .-minds roloaged. f heart ia detected, .urabor of 1 a diffuse rially the . but fully , has been J.LH. tUr.mo .V' iVt j-v; PULMONARY FIBROSIS IN ASBESTOS WORKERS 219 employed in aabeatoa for thirty-two year*about three yean on eardi, and the remaiader as a spinner. She has done no other factory work. Her family medical history discloses nothing of note. She has a personal history of nephritis seven or eight yean ago, causing three months' illness. Her complaints an; shortness of breath on hills, and winter eough for about sis years. Her nutrition is fair. She is rather pale. Chest.*--She has a chest expansion of onehalf inch. No retraction of the apexes is noted. There is general slight impairment of tbs percussion note, behind. Breath sounds an harsh and expiration is pro longed. Xo added sounds are heard. Xo grom enlargement of the heart is noted, but the second sound is found to be accentuated over the aortic area. The skiagram (Fig. 3) shows a general fibrosis, mostly linear, but with a little mottling of the right lung. There are also very old puerile tuberculous tears at the apexes. The case was diag nosed as general fibrosis. This ease should be compared with Case & In Case 6 then was a heavy exposure to dust extending over a few yean; in the pres ent csss there was exposure to a very much less concentration of dust, exeept possibly in the first three yean, but extending over many years. Cass 8.--This worker, a male, aged 62, has been employed in asbestos for twenty yean as a weaver. He was previously a cotton and silk weaver. His family and personal medical history show nothing of note, except that he was regarded as a deb ate child. His complaints are: shortness of breath on exertion, and on going upetain, for three yean; morning cough aod a little expectoration for the laat three winters. He is thin and pale, with some cyanosis. Chat.--Chest expansion is 1 inch; there is retraction of the apexes. The percussion note is impaired over both upper lobes, in front, and over the upper two-thirds of the right lung, behind. Expiation is pro longed at the bases. Pleural rub and incon stant riles are noted at the left base, and a few riles at the right base. A skiagram showed a definite diffuse fibrosis with nodulation. This is a ease of fibrosis in the early advanoed stage. Cass 0.--This man, aged 41, has been employed for twenty yean in asbestos in many capacities. There is nothing of note in his family history. He gives a history of pneumonia a number of years ago. His complaints are; a little shortness of breath on exertion for the last two or three yean; otherwise none. His nutrition is fair only. His color is fresh, but there is slight cyano sis of the lips, at times. Chest.--The skin is poorly elastic; there is some retraction of the aix'xes. There is an impaired, mther "boxy," note on percus sion, generally, especially over the upper half of the left lung, and over the upper twothirtU of the right lung, behind, and in front. Respiratory murmur is generally weak. Expiration is slightly prolonged, but diminishing toward the bases. Pleural crepitations am notod low down in the right axilla. A skiagram showed a definite fine diffuse fibrosis. Neither lung lights up very well, and throughout both there is a very fine diffuse reticulation and mottling-- moderate, but fully developed, fibrosis. Thu fine diffuse character of the radiologic appearances is particularly noticeable here. Case 10.--This man, aged 46, has been employed for twenty-five yean in asbestos, during nine yean of which he was not ex posed to dust. For eleven years of the remainder he was employed in the card room, and mattress making. His family and personal medical history disclose noth ing of note. His complaints are; shortness of breath oa exertion for three months; eough after a few hours' work in dust during the last two or three years, with little or no expectoration; and pain in the left side of the chest for the last three months. His nutrition is good. He is pale, with slight duskiness of the lipe. Chut.--There is some retraction of the apexes. The percussion note generally is impaired, and of a "boxy" character. Breath sounds are harsh and expiration < prolonged over the right upper lobe; where the respiratory murmur is a little weakened and expiration is not materially prolonged. Xo added sounds are heard. The heart is normal. The skiagram (Fig. 4) shows diffuse striation and line speckled mottling throughout both lungs--fibrosis, fully developed. Cask 11.--This worker, a male, aged 40, VLt3 No.5 DOU 02194 220 THE JOURNAL OF INDUSTRIAL HYGIENE hat been employed for twenty-two yean in asbestos--durinc the first eleven year* <<u earda and aa a weaver, during which he was expoeed to a considerable concentration of dost. During the remainder of the time he waa employed on a non-dusty process, but was expoeed to a leee concentration of dust derived from other prooeaaes. His family and personal medical history give nothing of note. His complaints are: shortness of breath on climbing stairs for the last five years; slight morning cough and expeetors- F:o. 4.--Case 10: Fully developed fibro sis. Diffuse striation and fine speckled mottling throughout both lungs. tioo for about the same time; and slight aching of the chest in front, below the left clavicle. His nutrition is good. There is slight cyanosis of the foee. CAJ.--Chest expansion Is 1 ineh; there is retraction of the apexes. There is im pairment of the percussion note generally, most evident over the whole of the right lung, behind, and over the right upper lobe in front. The note is "boxy" over the remainder of the chest. The breath sounds are slightly weakened generally, exoept at the right apex, but there is no grose change. Expiration is prolonged generally. Fine crepitations are heard in both axillae, and over the right upper lobe, in front. The heart is normal. Sputum is mucoid, but is negative for Bacillus tuberculosis. Clubbing of the fingers has been noted for about two years. A skiagram showed an exten sive diffuse fibrosis--fibroeis in a fairly advanced stage. Cass 12.--This worker, s male, aged 60, has been employed in asbestos for twentysix years in the eard room. Previously he was a sawyer's laborer. There is nothing of note in bis family and personal medical history. He complains of slight shortnri* of breath on exertion of recent years, and of winter cough for the last three or four years; expectoration is stated to be oil. His musculature and nutrition are fair. There is alight cyanosis of the face. Chest.--He has a chest expansion of threefourths inch. The percussion note is im paired generally, especially over the left upper lobe in front. The respiratory mur mur is weakened over the whole of the chest except the left upper lobe, where there are whistling breath sounds, and medium idles. The heart is normal. A skiagram showed very extensive changes throughout the chest of a coarse type without fine stippling. The roots showed a choked appearance. There was heavy mottling at the base. One old tuberculosis focus was ooted st the left base, and some ealcified glands in the left hilum. The diagnosis was fibrosis in the advanced stage. Csss 13.--This man, aged 66, has been employed in ssbestos for twenty-one yesrs as a weaver. For about sixteen yean pre viously he was a cotton and silk weaver. His father died of "chest trouble" st the age of 45; his sister died aged 15 of pulmonary tuberculoais. He has only been away sick a week or two in twenty-one yean, and has never had any serious illness. His com plaints are: undue shortness of breath on exertion during the last two yean; cough for the last two or three winten. Expector ation is creamy, and oecun a fair amount of times. He hue lost weight, and is thin. He is pale, but with some cyanosis of the face, and with a malar fiush. CAssl.--Chest expansion is 1} Inches; there is retraction of both apexes. Dulness is detected on percussion over the upper two-thirds of the right lung and over the left J. ML May. IU \ \ 4 ST0O64959 - The but is Clubabout oxtenfairiy tod eo, venty:sly ho othing cdical irtness s, and r four * nil. * fair. three* is imte left < murjcheat rc are t rale*, howod .cheat . The There ne old t base, Uilum. taocud ? btvn year* rs preleaver, the age nonary tick a ud hoa !> comcath on ; cough l>vctormunt of tit. He he face, inches; Dulness upiwr the left 1. t It. PULMONARY FIBROSrS IN ASBESTOS WORKERS 221 upper lobe, behind, and over both upper the sputum had remained small in amount, lobes in front. Breath sounds are rather and its appearance did oot suggest tubercle. weak, with prolonged expiration. Scat "My diagnosis from the beginning was tered variable rhonchi and idles are heard one of pulmonary asbestoeia with possibly over the right lung, behind, over the left addod tubercle. upper lobe in front, and over the left root. "I took two X-rays of him, neither of A The skiagram showed a definite diffuse which showed appearances suggestive of fibroeia plus tuberculosis. Sputum was tubercle, everything pointing to a very negative (one examination). The diagnoais extreme degree of fibrosis." was dust fibrosis in the advanced stage, with He died on Oct. 13,1928. No postmortem tuberculosis, probably active. examination was obtained. Cass 14.--'This worker, a male, aged 36, commenced work in an asbestos plant in 1010, but was employed on other work until January, 1914. During the next five yean, until early in 1019, about three yean and nine months were spent in army serv ice, for nine months of which be was a pris oner of war, but lie had two short periods of work in asbestoe--eleven months in the weaving, and six months in the mattress, departments. From early in 1010 to No vember, 1927, he worked in asbestos proc esses, but for only six yean and ten months in a dusty one (mattress making). He Hum cessed work. He was referred to a tul>*-n > losis dispensary on Oct. 19, 1927, when he gave a history' of bronchitis in 1916 and 1917 during the War, and of never being very well since; complaining of dyspnea, pain in the right side, and a slight cough of only about six months' duntion, with a small amount of grayish sputum. Dr. N. Tsttenali status that at that time: "Dyspnoea waa very marked, even on talking, and there was definite cyanosis. He had marked hollowing and respiratory retraction at both apices, especially the Fia. 3.--Case 14: Massive fibrosis, with pleural thickening, retracted apexes, and pneumothorax on left side with incomplete collapse of lung. right; loss of note over most of the right lung and the upper half of the left; bronchial breath sounds at both spices; fairly numer ous crepitations, mostly on the right side, end a pleural rub at the right baee. He had a systolic bruit at the apex and pleuro- lericardial friction. "I examined him a number of times, the tut occasion being April 20, 1928. In that time he had lost 9 pounds, felt very weak, tad the dyspnoea was increasing. The signs remained much the same, though occa It will be noted that the length of expo sure to asbestos dust is unlikely to have been more than about ten years and two months, and of this time he was employed only about eight and one-half years in a dusty process. War service, of eourae, may have reduced his resistance. The skiagram (Fig. 5) shows a massive fibrosis with pleural thickening, retracted apexes, and pneumo thorax on tho left side with incomplete col lapse of the lung. sionally, if be got a cold, the moist sounds were more numerous, especially at the bates. Seven sputum examinations were negative, and up to the time I last saw him No doubt fibrosis of the type pro duced by asbestos dust can of itself lead to complete disablement, and wa :s ST006U960 ^^m^asasrni^i^uauBuaam a(&SEjr '* f| &$*'*'*- ~ -'ZPfriFZtili tits--- - 222 THE JOURNAL OF INDUSTRIAL HYGIENE finally to a fatal termination, even in the absence of a supcnuided tubercu lous infection. The primary effect of the fibrosis would appear to be that of causing defective aeration of the blood, result ing in an added strain on the heart. For many years, and even with on advanced degree of fibrosis this may be of little inconvenience, provided physical exertion is limited, and acute illnesses ore avoided. Ultimately, however, the margin of safety, already diminished, is lost and the circulation slowly fails, with the usual signs of edema of the lungs. More often, however, an attack of bronchopueurnonia, influenza, or other acute infec tion adds too much to the strain, im pairs the cardiac musculature, and results in a fatal termination. (7*0 concludetT) BOOK REVIEWS BurvxjictrnjNO. By Prof. Dr. Paid Schmidt, Direktor Ues HygienUehen In* itituts 4er Universit&t Haile a. d. 3.; Priv.-Do*. Dr. Adolf Setter, 0beraa*la tent am Hyneoiaehen Institut Halle a. d. $.; und rriv.-Dot. Dr. Stillfned Litsner, Awistent ao der Meduimsehcn Klinik Halle it. d. S. Paper. Pp. 79 with index, illustrations, and bibliogra phy. Berlin and Vienna: Urban A Sehwarzenberg, 1930. This monograph is divided into a short introductory or general section and a special section. The first part is devoted principally to a discussion of the outstanding diagnostic symp toms of lead poisoning and of the work done by Dr. Sciunidt and his collabora tors in the microchemical determina tion of lead in blood, urine, and feces. The second part discusses in detail the usual sources of lead poisoning; the absorption, distribution, and excretion of lead; the pathology and clinical find ings associated with lead poisoning; and, finally, the diagnosis, prophylaxis, and therapeutic treatment of lead poi soning. Dr. Schmidt's monograph is particu larly apposite. It brings the literature of the subject down to the present date and represents the mature thought of on investigator wU) has long made this field particularly his own. The discus sion of the diagnostic features of lead poisoning is especially clear and to the point. In this connection it is of in terest to note that emphasis is placed on the importance of the determina tion of lead in the blood. No attempt is made to discuss the details of technic. The monograph presents instead a critical review of the more recent experimental work relat ing to lead poisoning and will, in con sequence, doubtless have a wide ap peal to all investigators in this field. The bibliography, which contains 208 references to the recent work and brings the literature of the subject down to 1030, is particularly valuable. "Bleivergiftung" may well l>e recom mended as a valuable addition to the library of students of public health.-- L. T. Fnirhall. J. I. H. 1930 ; . X.S..V--? -rf- . DOW 02197 :he ice r*- be liA- V*t V. ind au : is -,\s`ffi- >-r the me ^ : Vfc ; v . '* M*4. *? '* * tfnf, - "h * / -_if `y - i. E. vino --sv -' cr. -r^- Wfe-- 25^ - as? <friO 5/(5/7f THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS ` (Co*dud*n E. R. A. Mebewsthee, M.D. B. U. Utdicel Intpoctor of Fadoriu Morbid Anatomy Professor M. J. Stewart of Leeds has kindly supplied me with a detailed description (dated March 28, 1929) of postmortem appearances of several eases. From this account the follow ing points are extracted: The totally fibrosed areas of lung show grayish-blsck mottling, owing to immobili sation of carbon. This tissue is excess vely dense and completely airless; but the:* is no evidence uf calcification. Other por tions of lung show varying grades of the same process, and even the least affected parts are definitely tougher than normal. In none of the cases was there any evidence of an active tuberculous lesion. The (tom morbid aastozay of this Ictioa, as wo in persons who have been at work for many years is the dusty atmosphere of as asbestos factory, consists in a widespread pulmonary fibrosis affecting especially the basal region of both lungs. There are ca tenas-, j, densely fibrous adhesions through out the pleural sacs, which may, indeed, be come completely obliterated. In particular, the bases oi the lungs are firmly adherent to the diaphragm, and between theee two structures there is often a thick, homo geneous layer of fibrous tissue, similar in appearance and coaaistenee to yellow fibrocartilage. As a result of these two prooessss--pulmonary fibroeis and pleural sac obliteration--bronchiectasis develops in the midst of the more grossly diseased tissue end msy go on to the formation oi multiple abscesses with smooth walls. The distribution of the fibrosis, apart from the extensive basal lesions, is rather irregular, the peripheral, eubpleunl regions of the lungs being more affected than the central areas. In one ease in which the pa tient had been away from work for four yean (following nineteen years in ths mill), the ereas of dense fibroeis were extraordinarily ahsrply eireumaeribed. The nodular char acter of tbeJeeion which is so striking a feature of silicosis in its earlier stages is not met with in this disease. Histology The essential lesion is a chronic interstitial fibrosis of the lung. In the earlier stages, there is fibroblastic proliferation in the alveolar walls, which become increasingly thickened in consequence; and there is catarrhal desquamation of the alveolar epithe lium. Atthisstageofthediseasepeculiar golden-yellow "asbestosis bodies" ore found in varying, usually con siderable numbers, both in the alveolar spaces and in the thickness of their walls. Detached portions of bodies may often be seen engulfed by alveolar phagocytes, or a large unbroken body may be partially surrounded by theee cells. In the more advanced stages of the disease, the fibrosis of the lung is complete. Alveoli can no longer be made out; but the asbestosis bodies still remain embedded in the fibrous tissue. Varying quantities of carbon are also present, chiefly in little masses as though it had been contained with in phagocytes. Chronic bronchitic L!J No. I 230 m lr If m tim Iw f 1JS -V. ftf%7} *-'j m f:...... -(Sr-'S Hi DOW 02198 t If m> ii m * *; ii s* ii .> *: 11! "V A\ m Sk**' $J i.j >: W:- 240 THE JOURNAL OF INDUSTRLiL HYGIENE chaagr* mv prwwat tuui all grade* f bronchiectasis may be seen, is eases of longstanding, from simply bronchial and bronchiol&r dilatation, with walls srill more or less intact, to large spaces filled with pus in which the original bronchial walls have become converted more or less completely into fibrous and granulation tissue. Many of the smaller arteries show obliterative endarteritis. Reversionary metamorphosis of alveolar epithelium is frequent, and such alveoli ore often filled with albuminous fluid, in which dumps of "bodies" may be found. Asbsstos Dust in tbs Lungs Dr. W. E. Cooke has supplied (under date of June 25, 1929) deuiils of his researches on asbestos dust in the lungs, and on tho constitution of the curious bodies, which have been freelyusedintbc following notes:-- Sections of lung and the results of digestion of the lung with trypsin show an enormous amount of fine black granular dust, much of which is carbonaceous. In addition, there are two striking features. The first is the almost complete absence of the fine translucent spicules of fiber which make up a great proportion of asbestos dust in factories. The second feature is the presence of lsrge fragments vary ing in length from 10 to 360 microns. They are found in fibrotic and necrotic areas, singly and in groups. The particles are so large--masses of them are seen in some sections--that they must have occluded small bronchi and jesulted in fibrosis of the surrounding area. Comparing these large particles in the lung with those found in asbestos dust, dose resemblance in sites, shapes, and colors is apparent. There are the same black, blue, brown, and trans lucent fragments. In fact it is easy to take such a single particle from the lung and immediately find its brother in a slide made from the dust. Curious Bodits In addition to the fine granular dust and larger fragments of asbestos, sec tions of the lungs show curious bodies. They are found in alveoli, bronchioles, fibrous and necrotic areas, and in phagocytes in sections of both lungs. If a portion of lung is teased and extracted with water, or digested with trypsin, or, as Professor Stewart pointed out (192S), if a smear is made from the cut surface of the fresh lung, these bodies are seen in myriads. The larger bodies measure from 20 to 100 microns or more in length, and are of a golden-brown color. They may have single clubbed ends or may appear as elongated dumb-bells; some are filamentous, while others suggest a series of disks. Single coccal and spore-like forms, and aggregations of these, and strepto coccal forms are not uncommon; the color varies in the smaller types from a very pale yellow to a yellowish-brown. The bodies do not stain with any of the aniline dyes, but in ebrysotile workers, they give the Prussian blue reaction for iron in varying degrees of intensity. These curious bodies have been found in every autopsy in pulmonary ashes* toeis. It would be unprofitable to retrace all the steps which led down many by-lanes during the course of the work, but I will mention a few per tinent details of interest. Professor Stewart suggested to me 3.1. H. JMO t'. $T 0.064 96 3 $3*5 mm^L 353*552x5 A ^5 .'.v --- m <*`.c *-. DOW 02199 | . ; c* : PULMONARY FIBROSIS IN ASBESTOS WORKERS 241 that ft better method than simple the large black, blue, and brown par extraction of the lungs with water or ticles and what appear to be pieces of aline would be to digest portions with quartz. Relatively few fine spicules trypsin. During this process it was are found; but curious bodies of all found that if the specific gravity was descriptions are present in enormous kept at about 1,070, the black dust numbers. and larger fragments of asbestos, as AU these facts lead us to imagine ft. well as the partially digested lung the bodies to consist of a central tissue, sank to the bottom of the tube. nucleus of asbestos spicules, upon By decanting the apparently clear which colloidal aggregate of blood supernatant liquid, and by centrifugal* proteins plus, possibly, soluble frac izing, neutralizing, and washing the tions of asbestos and, in the case of deposit, the curious bodies could be chrysotile workers, an iron salt have # obtained in a pure state. This was been adsorbed and molded by currents done, and sufficient material for X- in the bronchi and the alveoli. ray examination was obtained. The The method of formation would bodies were attached to a hair with appear to be as follows; The fine .3 gum and subjected to a seven-hour spicules of asbestos cause, by mechan exposure by Professor Bragg's method. ical action on the bronchioles and r.'t?: If the bodies were mineral, the X-ray alveoli, either minute extravasations "*V. N-j: film would have shown a definite of whole blood, or serous exudates translatable atomic pattern. The which envelop them. Solution of any films, however, did not do so, and we soluble fraction of asbestos takes Ar were then able to exclude the sugges place. The total amount of asbestos tion that the bodies were altered that is soluble must be extremely asbestos fiber. The result definitely small, as is proved by the X-ray pointed to the greater proportion of pattern of the curious bodies, but in their composition being of nonmineral the cose of chrysotile workers some origin. solution is suggested by the free iron The bulk of the curious bodies is reaction. We must remember, how soluble in strong acids and alkalies, and if the solution is observed under dork ground illumination, their bases are seen as extremely fine spicules some of which by transmitted light would ' probably be invisible. Under a dis secting microscope it is possible par tially to fracture the larger bodies and to show a central fine core. The greater portion of asbestos dust consists of slender translucent fibers. In sections and extracts of the lungs there is a remarkable paucity of these ever, that the Prussian blue reaction may be due to the iron of the hemo globin. Any surface La contact with a colloidal solution may act as an adsorbent, and in the present case the fine spicules must be considered to do so. Interaction between the soluble fraction of chrysotile and plasma proteins takes place, syneresis occurs, and, with the loss of water, the adsorp tion is rendered irreversible. The adsorbent is permanently enaheathed fine spicules. The end-results of diges with stable colloidal aggregates which tion show the fine granular dust and become molded into the familiar Vet. U Mo. I t j*. M {`W* vfn1 'M i i fejiai #H Iff*. m DOW 02200 242 THE JOURNAL OF INDUSTRIAL HYGIENE shapes by alveolar and bronchial cur lymphatic glands; in material obtained ised i rents. by lung puncture during life, first sug CO Ioopc .V Support for this idea is found in the factthat micro-organisms adsorb col loidal material in the presence of blood serum and colloidal asbestos. Staphy gested by S. A. Henry; in the sputa; -H and cut in smear preparations surface of the lung. from the In smear O o cr> preparations they can be readily a hot burne water earn. toais lococci so treated appear as large demonstrated. lowp UD firm* round yellowish-brown disks; in the The importance of these findings C Aaax process their property of staining with lies in the fact that the bodies have cn ben, V. aniline dyes is lost. The organisms never been found, as yet, in any other film. coalesce ami form masses; and I human affection. That similar bodies work think it probable that some of the may be found to occur in the lungs of coccal and spore forms are similar workers exposed to other dusts, is one c the fi necei organisms. quite possible, although they have not ware Finally, are the curious bodies been found in silicosis, nor were they diagnostic of pulmonary asbestoais? present, according to Simson (6), ia s Asbestos is unique among minerals in the fibrosed lungs of a hematite miner. being fibrous; and its dust, generated They appear within a comparatively during manufacturing processes, is short period of time after exposure to tions antic T1 chlor dem< give: also unique. As can be imagined from asbestos dust; at the moment, their the formation of the curious bodies, presence in the sputa, in the absence there is no reason why, given any of clinical or radiologic evidence of pul silicosis, a fine spicule of mineral should monary fibrosis, cannot be taken as in 0 not have colloidal matter deposited dicating anything more than previous inec around it and become molded into a inhalation of asbestos dust. The pres tob curious body. But as no other min ence of the bodies, however, in the in g eral dust is fibrous, this occurrence sputa of persons with signs of a diffuse thes must be so rare as to be negligible from fibroeis, or their presence in numbers on sioc a diagnostic point of view. The con postmortem examination of a fibrosed dus ditions which, apparently, must obtain lung, has evident implications. min for the formation of curious bodies are Professor Stewart, who is continuing if con the presence of plasma proteins and his work on this subject, has devised mei fine spicules soluble only with diffi the following method of examining per ik-' culty. These conditions are ideally sputum for asbestoais bodies: to \ &'. found in asbestos workers; for this due reason I believe that curious bodies, if Half o ounce or so of sputum is added to found in any numbers, are pathog an t*quai quantity of undiluted aatiformis. TLia is gently agitated until the sputum cen nomonic of pulmonary asbestoais.-- is completely dissolved, after which it is di* W, E. Cooke and also Roodhouse diluted with 2 or 3 ounces of water and 1 Gloyne (20) have independently dem allowed to stand in a large test tube for onstrated the presence of a mineral three or four hour*. The bulk of the super Y par core, evidently derived from asbestos natant fluid having then been decanted, the . remainder is centrifuged at a moderate 4 fiber?) in the curious bodies. The speed for ten to fifteen minutes. The whole bodies have been found (Stewart and of the supernatant fluid is now poured off, fou nat one Haddow (21)) in the intrathoracic and the depoeit transferred to an albumin- (24 i. h. Jua*. tsu Vol. No. >$_ :-v! I # >lh %~ci '-r ; 3P >/ ;*** ~vAv.-*vv *? .*Al: r Vf*. **; > :f 4.**; :V:& .tf' PULMONARY FIBROSIS IN ASBESTOS WORKERS 243 . feed elide, by neem of either * plttfauw loop ore pipette. After thorough drying os hot plot* end final fixation over a buneen burner, the film it eery gently washed in water, dried, and mounted in' Canada bal sam. After a little'experience the aabee- toeis bodies are readily picked up with the low power, and their true nature ia then eon- firmed with the 4-ioeh or oil lent. Aa a rule they are present in eery email num bers,,perhaps only one or two in a whole film. In the ease of some of the older workers, however, numerous bodies, up to one or two per field in certain portions of the film, have been found. It is obviously necessary to cleanse thoroughly all glass ware, etc., used in making these examina- tioos; otherwise there is a risk of contami nation of subsequent specimens. The films can be treated with hydro chloric acid and ferroeyanide of potash to demonstrate the Prussian blue reaction given by the bodies. A&bestosxs ax Occupational Hazabp Out of & total of 374 workers exam ined, 105, or 28.1 per cent., were found to be affected with fibrosis of the lungs, is greater or lees degree. But when these figures are corrected by the exclu sion of cases in which previous work in dusty occupations (.p., quarrying, coal mining) may have been the prune, or a contributory, factor in the develop ment of the fibrosis, ninety-five, or 26.2 per cent., of 363 workers were found to be affected with pulmonary fibrosis due to the inhalation of asbestos dust, and a further twenty-one, or 5JS per cent, showed precursive signs of this disease. This percentage may well be com pared with the corresponding figures found by Middleton (22) in his exami nation of metal grinders (46.9 per cent.) and by Sutherland and Bryson (23) (24) in their examinations of potters (39.9 per cent.) and of sandstone workers (58.1 per cent.). The precise significance of the lower figure found in this inquiry is not easy to determine. At first sight it seems to indicate that asbestos dust is less potent as a cause of pulmonary fibrosis than are the dusts containing free silica. Other factors, however--such aa the measure of exhaust ventilation, or other means of reducing the concen tration of dust, in the several indus tries; differences in the average length of employment of the comparable groups in the samples examined in the respective inquiries; and the relative numbers employed in the more dusty and the less dusty processes--will affect the crude incidence rates ex pressed by these percentages. From comparison of the amounts of dust evolved--determined visually and by means of dust counts--in dust/ asbestos processes, uncontrolled by local exhaust ventilation, with obvi ously defective exhaust ventilation, and with comparatively good exhaust ventilation, there can be no doubt that this preventive measure, which has been applied in some degree for more than seventeen years, has been a posi tive factor in minimising the produc tion of fibrosis--probably in the direc tion of lengthening the period before the fibrosis becomes fully developed. Consideration given to the distribu tion of the workers examined both according to length of employment, and according to age, together with the incidence rates of fibrosis in each case, indicates the outstanding importance of length of employment (and hence length of exposure to dust), and the negligible effects of age, on the produc tion of fibrosis. Thus age groups 30 to VoL is No. 7*? _ Aim --4 O 'SR?'*31 O o UD cr> cn pi ilSfa aMM U-. ssr*.:? t ; . -y. fife*'-;- jpilP ' L-K !i.V; ' i.r f a DOW 02202 244 ' THE JOURNAL OF INDUSTRIAL HVCIENE 30 and 50 to 59 have incidence rates of 30 per cent, and 37.9 per cent., respec tively--not a wide difference, since the groups include workers in various processes exposed to different concen trations of dust. Moreover, the aver age length of employment in these two groups, excluding the cases of ffbrosis, fibrosis in age group 20 to 29, has been shortened by increased susceptibility at ages under 20. As, however, the average age of this group of cases of fibrosis is 28.7 years, and also because the establishment of fibrosis does not necessitate immediate retirement from work, this is largely discounted. TABLE 5.--DISTRIBUTION OF WORKERS EXAMINED WHO HAD BEEN EMPLOYED FOR FIVE YEARS OR OVER, TOGETHER WITH CASES OF FIBROSIS, ACCORDING TO PROCESS IN WHICH WORKER WAS LONGEST EMPLOYED raocass KO. sz- amxnxo cases or nssoars No. Per Cent, of Group arsaaos lxkot* or SXF&OTUXMT IK T*8. Group Less Cases of Fibrosis Cases of Fibrosis 1. Crashing, opeBing, disinte- grating, and mixing............ 2s P-inHrtf.................................... 3. Spinning, twisting, doubling, plaiting, ete......................... 4. Mattress ..................... 5. Weaving and associated processes...................................... a. Cloth weaving................... b. Band weaving.................... e. Cloth and band and un- classified weavers............. d. Warpers, beaaers, loom tuners, charge hands, and other* associated with weaving.................. 8, Miscellaneous processes and remaining onclaasifiod worker*................................. 28 21 14 25 21 9 39 15 42.9 41.0 8.9 10.9 9.1 13.2 87 12 13.8 10.1 18.7 15 7 46.7 7.3 13.0 88 40 45.5 10.0 12.7 21 75.0 9.5 14.1 4 19.0 10.9 13.5 4 28.6 7.2 9.5 11 44.0 11.2 10.8 24 11 45.8 8.8 13.8 Total.......................................... 274 95 34.7 9.6 13.5 is also similar, but considerably less than the average length for all the cases of fibrosis (13.5 years). No special susceptibility to the development of fibrosis is shown by young persons, unless it is considered that the figure of S.7 years, the average length of employment of the cases of The effects of length of employ ment ore such that after five years' exposure, the incidence rate of fibrosis mounts rapidly, and after ten years increases almost in geometric progres sion. Table 5 shows the distribution of 274 workers examined, and of those with fibrosis, according to the process UH, Jut*. 1930 i GO O o i *.-c I f-.i i. t- PULMONARY FIBROSIS IN ASBESTOS WORKERS 245 in which they were longest employed. remains longer in the milder, and This was a compromise necessitated radiologically linear stage. by the common customs in the indus This view is evidently of consider try of having several different processes able practical importance since it sug going on in the same room, and of gests that in such cases, the rate of workers transferring from one process accumulation of dust in the lung has to another. Since the intention was not greatly exceeded the rate of elim to obtain some measure of the refctftM ination, the changes still being centered incidence of fibrosis in workers in the in the main lymphatic system. various processes enumerated, and If this hypothesis is accurate, it since no case of fibrosis clearly due to should follow that in order to prevent asbestos dust was found among eighty- the full development of the disease, nine workers examined, who had been among asbestos workers, within an employed for less than five years, in average working lifetime, it is neces clusion of this group of workers would sary to reduce the concentration of only have introduced a varying source dust in the air of the workrooms to a of error. figure somewhat below that pertaining The processes differ, some very to spinning at the present time. materially, in the amount of dust Fortunately, also, the spinning which they cause, and consequently in group is the largest individual group the amount inhaled by the operators in this section of the industry--t.q., (30). The outstanding point brought out of over 400 workers employed by out by Table 5 is the relatively low one firm, this group accounts for more incidence rate of fibrosis in "spinners" than one-third. (group 3), as compared with each of Although'all workers examined who the other groups. They are corrobo have been included as spinners have rated by counts of the dust particles been engaged in spinning, or in simi in samples of air, a number of which lar processes for convenience termed have been taken and are discussed "spinning," for a longer time than on under Dust Risk. any other process, only a few have been There is also some indication in these employed solely on spinning, and in figures that not only are "spinners" workrooms where no other, and more less likely to develop fibrosis, but when dusty processes, were being carried on. they do, it takes longer to develop. These two factors, prior work in Study of the radiograms suggests that more dusty processes and present in such cases (*,., in the less dusty work in proximity to more dusty proc processes) the resulting fibrosis is, for a esses---especially the latter--have had, considerable period, much more linear it is believed, some effect in raising the in its radiologic features, and shows incidence rate of fibrosis for this group. lessmottling. The history and clinical features in theee cases, and the com Dust Risk parative dust counts, all contribute to In an effort to obtain additional data the view that with comparatively low on the influence of concentration of concentrations of dust, the resulting dust in workrooms, a number of sam fibrosis is longer in developing and ples of air were token and the dust con- vl u No. I 246 THE JOURNAL OF INDUSTRIAL HYGIENE TABLE A--SUMMARY OP DETERMINATION OP DUST CONTENT OP ATMOSPHERE OF WORKROOMS AND OTHER PLACES uou *0. flOCUl 4MB 40TOCS Of 4AM?LX LOCAL BX8APST VXNT1LA* OTSXX FSOCrn TXON TO VXOCXaS on MOT IK SANK XOOtt NO. OF FXXCXMT* FXBCXMT* FAX' AOX AOS TICLXS 2m and 7.5m and FtX C.C. TJNBtR ondsx 1. 1/2 2. 1/S 3. 1/3 4. 1/7 S. 1/3 6. 1/8 r. i/i 8. 2/11 9. 2/1 10. 2/14 11. 2/10 12. 2/8 13. 2/7 14. 2/9 15. 3/1 16. 3/4 17. 3/3 18. 3/S 19. 3/2 20. 4/1 21. 4/1 22. 4/3 23. 4/4 24. 4/5 25. 4/54 26. 4/6 27. 4/7 28. 4/9 29. 4/10 30. 4/11 31. 4/12 32. 4/13 33. S/1 34. 6/2 35. 6/3 36. 6/9 37. 6/6 Carding; puupn? between sards Spinning Cloth weaving, dry Opening Sieving; aboveling fiber on to sieve Plaiting Office Office Cloth weaving Spinning Mattreu making; filling Mattress making; beating, damp Mattress making; Mating, dry Mattress making; after filling 2 mattresses Band weaving, wet Opeoing Carding; between eards Carding; feeding card Office Mattress making; filling Mattress making; filling basket Emptying settling ehsmber Same Insulating sections; leveling fiber Carding; side of dirty card Carding; end of dean card Carding; feeding card Cloth weaving, very slightly <4fnp Cloth wesving, damp Braiding Spinning Office Band weaving, dry Cloth weaving, dry Band weaving, dry Opening Carding; feeding card Yes No No Yes No No .. No No Yes Yes Yes Yes No Yes Yes Yes 4 No No No No No Ye# Yes Yes No No No No * No Yes Yet Yes Yea Yes 2,139 Yes 1,466 Yes 1,756 Yes 2,384 Yes 2,629 No 1,687 ... 901 e 1,480 Yes 1,788 Yes 1,073 No 985 No 970 No 1,629 No 1,204 No 806 No 2,313 Yes 1.528 Yes 1,321 . . . 1,049 Yes 1,858 Yes 1,390 Yes 3,401 Yes 4,711 Yes 1,838 No 1,402 No 1,092 No 1,689 Yes 3,033 Yes 758 Yea 506 Yes 954 689 Yes 2,202 No 885 No 701 Yes 643 Yet 562 81.3 95.1 95.9 100.0 84.1 96.7 80.9 93.7 83.0 97.6 99.0 99.0 96.8 100.0 98.7 100.0 88.9 98.6 96.2 100.0 92.5 98.1 85.9 95.8 86.9 96.6 96.6 99.4 96.6 100.0 77.7 96.6 82.5 97.4 82.9 .96.4 96.3 100.0 60.1 90.1 -- e .... . * # ,,,, .......... ,,,, . # ..... A ,,,, .... ^ o O C*> ~ ^v_o , J.LH. rXMTax A.VS OCA 5.1 0.0 5,7 3.7 7.6 9.0 0.0 0.0 *8.6 0.0 .l >5.8 >6.6 >9.4 oo 0.6 >7.4 04 0.0 0.1 . *nj. '71 ' *v- * . W: * .*ttV ?T:*? . *'Xs iv.. 3# ;' *. j. u. wo "s PULMONARY FIBROSIS IN ASBESTOS WORKERS 247 TABLE 6.---Continvtd aaim* MO. noctu An aouxe* or tA3BLM nocat. SXXAOST VXKTILa* TtOM TO pxocsas OA MOT otxxa rXOC* ESI IK Sana xoou mo. or rax* Tictxa rxx c.c. MXCXNT- rzacxMTaox aox 2m axn 7.5m aKD CMSXX CtfSKX 88. 6/4 39. 6/5 40. 6/7 41. 6/6 42. 7/3 43. 7/1 44. 7/3 46.7/4 48. 7/5 G. 7/6 48.7n m. 8/2 SO. 8/3 SL 8/5 Carding; center of room Carding; grinding rolleis Spinning Office Cloth weaving, dry Opening; ehoveling fiber into box Opening Band wearing, wet Spinning Carding; between earda Office Goth weaving, dry Band wearing, dry Yes Yea No ... Yes Yes Yes No No Yes No No Yes Yes 620 Yss 540 Yes 620 . . . 666 Yes 4,688 Yss 4,880 Yes 6,324 Yea 5,353 Yes 6,044 Yea 4,607 . 3,413 Yes 1,287 Yes 1,233 Yes 1,105 .... ...... eee *e .... 88.6 78.2 07.2 e 4e 04.0 03.7 04.0 tent was determined by means of Owens' jet apparatus. Here also the undetermined effect of dust from neighboring processes must be noted. Nevertheless some information of prac tical value was obtained. Reference to Table 6 shows that the counts ranged from 506 to 6,324 particles per cubic centimeter in the air of workrooms, and from 666 to 3,413 per cubic centimeter in the air of offices associated with the factories. In some coses there was a smaller count in a workroom than in an office of the same factory; this was due either to there beingmueh fewer smoke particles In the air of the workroom, or to adher ence of the smoke particles to the inorganic dust in the workroom. The character of the dust in the two eases is, however, entirely different. In the air oLthe office almost all the particles are black, or brownish, and amorphous, evidently smoke; in the air of the workroom, the majority of the particles are, just as clearly, crystalline particles of asbestos, to gether with, frequently, some cotton fibers and numbers of black and brown ish particles, some adherent to asbestos spicules and some free. Most of the latter are iron containing and are derived from the asbestos, and there are relatively few smoke particles. Iso lated golden-brown scales or plaques, also derived from the asbestos, are scattered about the field. The asbestos fiber first fragments longitudinally, and apparently this process can go on indefinitely, since there is no ultimate fiber comparable to a vegetable fiber such as cotton. The dust collected in the Owens appa ratus contains numbers of these very fine fibers--some about 0.5 micron in transverse diameter, many less--which have fragmented transversely. Thus spicules of very diverse length--up to Voi. u So. * <jy o o cn -J O DOW 02206 ** a 'Jfcl I * !SK :*#i. A SI* #*V$'. i <\ mi ?_ i rr KSSiH 248 THE JOURNAL OF INDUSTRIAL HYGIENE &bout SO microns--but about 0.5 micron broad, are found in numbers on the sample, together with the black, brownish, and yellow particles already mentioned. The great majority of the spicules are found broken down into particles of the order of 2 microns and less, many being about 0.5 micron and more or las rounded. The proportion of elongated to rounded particles seems to vary in the different processes; for example, a greater proportion of elongated particles is found in the air near dry cloth weaving than near a spinning frame. Weaving damp reduces the proportion of elongated particles. This variety of microscopic spicules, particles, and frequently some cotton fibers, found in the samples of dust col lected in the Owens apparatus, results in a tendency to clumping on the cover slip, making counting, especially of the higher concentrations, a matter of extreme difficulty. Occasionally, also, part of the slot of the apparatus choked up with dust. The effect of the clump ing is to reduce the counts of all except the low concentrations. Furthermore, this apparatus is much influenced by local air eddies and cur rents. It takes a grab sample, which is accurate enough as an indicator of the local conditions at the moment of sampling, but does not give a picture of the average state of the atmosphere during-a period of time, as does a gravimetric apparatus. Moreover, with high concentrations of dust, accurate counting becomes impossible. The apparatus has, however, many advantages, including those of con venience, quickness in operation, and "direct examination of the nature of the dust. By serial observations, too, temporary and local large increases in the dust content of the atmospheresuch as that produced by shoveling asbestos fiber into a sack--can be detected and estimated. This is of great importance since short, but repeated, exposure to massive concen trations of dust is agreed to be very harmful. Counts Nos. 5, 22, 23. and 43 in Table 6 are examples. Much useful work can be done by means of serial dust counts in various dusty processes in the same factory, and by comparison of the results. The counts set out in Table 6 are derived from eight different factories, and it is a matter of interest to con sider whether oounts from different factories can be directly compared with one another. Strictly they cannot, since the content of smoke particles varies in each group. The difficulty might be obviated by oounting only the particles derived from asbestos. The method has been applied success fully to counts of crystalline silica dusts; but it is not so easily applicable to counts of asbestos dust, which con tains numbers of black and brownish iron containing particles, many of which ore not quickly distinguishable from smoke and tarry particles. To classify the processes accurately on the basis of amount of dust evolved, it is necessary to take serial sam pies at intervals corresponding to the details and complexity of the processes. With some straightforward processes, such os spinning, few samples will be necessary; but in others, such os mat tress making, mixing, grading and opening--especially with old-fashioned plant--in which the evolution of dust rises and falls rapidly in a compara tively short space of time, many more observations are necessary throughout J. I.H. JiU*. 19M oo --I o CD CT> **" 10 rfsr DOW 02207 pulmonary fibrosis in asbestos workers 249 ST0064972 a shift, to determine the average eon* centration of dust Repeated controls are also required. Comparative data show that the dustiest processes are opening (with old-fashioned teasers), sieving (with no local exhaust ventilation), and shoveling, or otherwise faulting asbes tos fiber. The heaviest counts of all werefoundin this group, in fillingsacks, by hand, with disintegrated fiber in a settling chamber. The visual cloud of dust was intense, and irritating enough to provoke immediate coughing on the part of the observer. The dumping of the dust particles of the sample on the cover slip was very marked, with the result thatthe toted dust oount arrived at was undoubtedly too low. With counts of asbestos particles of this order, however, the precise count is of little practical importance, since the dust concentration is far beyond the safe limit. Next in order is doth weaving, dry and without the application of local exhaust. This is undoubtedly a dusty process, and although local exhaust reduces the count at the breathinglevel of the weaver, much dust still escapee into the workroom. Further counts are necessary to estimate this. Weaving doth wet, not merely damp, reduces the dust count to a remarkable degree. The figure for band (., narrow) weaving, wet, is not accurate since it was raised by dust from a neighboring dry doth loom; still the improvement due to wet methods is notioeable. One asbestos weaver, who was formerly a cotton weaver, and who has to wear glasses, stated that whereas he used to dean his glasses about three times a day when cotton weaving, he has to de&n them about five times a day when asbestos tape weaving dry, and only once a day when weaving asbestos wet. Next inordercomes mattressmaking, without any precautions such as ex haust ventilation, or damping floors, doth, and tables. Application of ex haust ventilation and damping reduce the count considerably, but it is be lieved that the figures are too low, since counts for some subsidiary processes such os buttoning, sewing, and cutting out are not available. The figures for spinning, plaiting, and braiding are believed to be rather too high, owing to contamination of dust from neighboring and more dusty processes, and further investigation is required here. A. number of the samples taken with the Owens apparatus were examined to determine the size of the particles, and the percentages of particles 2 microns and under, and 7.5 microns and under, were ascertained. The 2micron standard was retained for purposes of comparison, and because of its accepted importance in silicosis. The 7.5-micron figure was also adopted because of the pronounced acicular character of much of the asbestos dust, and because, representing the diameter of the human red blood corpuscle, it is a standard easily distinguishable, and may conceivably represent the limit size of particles which can be con veniently engulfed by phagocytic cells, which ore somewhat larger. Among twenty counts from various processes (Table 6), in two, between 60 and 70 per cent, pf the particles were of sizes 2 microns and under; in two, 70 to 80 per cent.; in ten, 80 to 90 per cent.; and in six, 90 per cent, and upward. When the counts were analyzed ae- r*i i3 x* THE JOURNAL OF INDUSTRIAL HYGIENE cording to the 7.5-micron standard, all twenty showed 90 per cent, or more of the particles to be of this sise or less. With regard to the effect on the Ipngs of different varieties of asbestos, no evidence was found to indicate that any one of its varieties is more potent in producing fibrosis than the others, other factors, such ae concentration of dust, being equal. There is now no doubt, however, that both chrysotile and croddolite will produce fibrosis; while the third, the comparatively newly discovered amosite, resembles croddolite so closely in its chemical constitution, and in the characteristics of the dust, that there can be no reasonable doubt, also, with respect to it. Length of Duet Exposure No case of diffuse fibrosis clearly due to asbestos was discovered with under 5 years' employment. Three cases were found with 3, 3$, and 4} yean' work, respectively, who showed clinical signs of fibrosis. Definite confirmatory radiologic evidence was obtained in the first, definite but slighter radiologic changes in the sec ond, and indefinite suggestive changes in the third. The previous occupation in the first case was fiax weaving for 18 yean; in the second, cool hewing for 16 yean; and in the third, work in an iron foundry for 1 year. All these occupations are dusty; and in the last two there may be some exposure to free silica. Also increased silica con tent has been found in the lungs, after incineration, of flax dressers. For these reasoos, these three cases could not be certainly ascribed to asbestos dost, although it was, probably, at least a contributory factor. Among the cases of fibrosis found, thirty-six had been employed in asbestos for periods ranging from 5 to 10 years; two of these cases, one employed for 9 years and the other for 7 years, show that a considerable degree of fibroeis may occur with less than 10 years* exposure. F. W. Simson (6) examined the lungs of a guinea-pig which had been experi mentally dusted by Mayrogordato for two hours a day on each of fifty days between February and April, 1925, and which died from other causes in December, 1927. He states that his tologic sections showed a alight gen eralised fibroeis. This observer also examined portions of the lungs of two native asbestos mill workers; one had been employed for twelve months and had died from a miliary tuberculosis, and the other, employed for two years, had apparently never recovered from an attack of lobar pneumonia a year before death. In commenting on the amount of fibrosis found, he states that "a com parison between the human cases and the experimental animal showed that the fibrosis was more rapid and exten sive in the human cases than in the experimental animal," and, again, that "the amount of fibrosis in two of the human cases .... was quite definite, and, if due to the presence of asbestos dust, the initial rate of pro duction was rapid when compared with present-day non-infective silicosis on the Rand." Experiments by Professor Beattie, in 1912, demonstrated that the lungs of guinea-pigs exposed to asbestos dust for forty-three and sixty-seven hours showed "definite cellular proliferation, though not very extensive, and this is . X. B. . u **. OO --\ o o cn UD c _ CO i r s h e t t e a v t o t< a a. P b T P- CL CL Ye Sc K DOUi 02209 its * *1 he lungs iexpesij.WJfdato for fty day* J, 1925, ausea in that hi*ght genver also js of tiro one had nths and reuloais, ro years, fed from a year unt of a comsases and wed that extenin the again, two of quite aence of of pro* red with Jcosis on Beattie, lungs >s dust hours ration, this is Jua*. WO PULMONARY FIBROSIS IN ASBESTOS WORKERS 251 certainly a preliminary stage in the production of fibrosis." These pathologic and experimental findings suggest that the inhalation of asbestos dust rapidly causes some changes in the lungs. But no evidence was obtained that asbestos dust can produce an acute type of fibrosis com parable to that formerly noted in South Africa after repeated exposure to massive concentration of free silica, a few cases of which have occurred recently in Great Britain, causing death m from two to four years. The amount of disablement pro duced by the development of pulmo nary fibrosis in these workers is surpris ingly slight for a number of years, even more so than is generally the case in silicosis. The nature of the work, however, in the majority of the proc esses does not involve much physical exertion---in fact, ia this respect it is "light work." The affected person may, and often does, continue at work --with occasional intermissions, lat terly, due to exacerbatious of bron chitis--until the condition is advanced, although he suffers increasing incon venience from shortness of breath on the slightest exertion. Usually these cases cease work a year or more before death, but sometimes a terminal bronchopneumonia, or other scute infection, commences while they are still at work, and there is no long period of invalidism. Fatalilie* Particulars of eight deaths have been collected, and are summarised in Table In six of these, advanced pulmonary fibrosis was the primary cause of death. In the remaining two eases, pulmonary tuberculosis was a contributory factor. In six of the eight cases the diagnosis was verified by postmortem examination; in the other two cases, confirmatory radiographic evidence was obtained. Information has recently been ob tained in regard to three other cases, in which death occurred in 1929. The details of one have been published by Wood and Page (25). Postmortem examinations have been made in all three cases, and in all, the presence of pulmonary aabestosis, without tuber culosis, was verified. In one case, the pulmonary fibrosis was the primary cause of death; in one, information as to the extent of the fibrosis has not yet been obtained; and in the third case, a lobar pneumonia was superimposed on the fibrosis. It is not suggested that these few fatalities, in which the cause of death has been verified by strict inquiry, are any criterion of the true effect of the disease on the mortality rates of asbestos workers. Others are known to have occurred in which the exist ence of the asbestos fibrosis has been determined in life, but no postmortem examination has been possible. Difficulties in Diagnosis Many factors have contributed to impede both the recognition of indi vidual coses of this disease, and the establishment of asbestos dust as the determining cause. These factors are consequent, partly on the nature of the disease, partly on the nature of the dust, and partly on the industry itself, its rapid growth and internal condi tions. Difficulties in diagnosing the disease, its points of resemblance, in its latest stages, to fibroid tuberculosis, and the liability of those affected to be ST0064974 ' '1- * i i DOU 02210 Vs* ^"1 . / * Ectitiuted. PULMONARY FIBROSIS IN ASBESTOS WORKERS 253 carried off by some intercurrent die* ease--which alone is notedonthe death certificate--are all of importance. A concrete example' encountered during the inquiry will illustrate one of these points. J. C., Case No. 7 is Table 7, was known by his own doctor and bytheChiet TuberculosisOfficer of the tows to Ik- affected with advanced fibroeis of the lungs. Four or five months before his death it was thought that a change of air would be of advantage to him. Through the gen erosity of the firm with which he had been employed, he was transferred from the tows to a farm in the country, where he died. The death certificate, given locally, stated that pulmonary tuberculosis was the cause of death. In another case chronic bronchitis was given as the cause of death. In the less advanced stages of the disease, the symptoms are so unob trusive that the worker rarely consults his doctor. In the later stages, bron chitis, or the supervention of acute bronchopneumonia, pulmonary tuber culosis, or other scute infection, ail so much more common, masks the under lying fibrosis; and the terminal condi- tion is noted as the cause of death. In the second place, the silicate dusts --of which asbestos dust is one--repre senting silica in the combined form as opposed to free silica, have naturally been overshadowed by the silica dusts, since they do not produce the picture of silicosis and have not been shown to be associated with an increased mor tality from pulmonary tuberculosis. Moreover, although the asbestos in dustry has very rapidly expanded, it is still comparativelysmall, and scattered over the country. A Urge proportion of the workers have been employed in asbestos only for comparatively short periods, and of the processes considered so far, the less dusty spinning group is at the same time the largest. Thus only now the existence of a health risk in the industry is beginning to be recognised. Doss Asbestos Dust Predis pose TO OthSB PUUtONABT Diseases? The important question as to whether asbestos workers show an in creased liability to other diseases of the lungs, such as pneumonia, pleurisy, and pulmonary tuberculosis--espec ially the Utter--requires further in vestigation. A history of pleurisy was given by ten workers, in eight since commencing work in asbestos; in addition, one worker had a slight pleural effusion at the time of examination, and one showed signs of old pleurisy, but no history was obtainable. Of the two with attacks prior to work in asbestos, one had normal lungs, and the other showed signs of a bronchiectasis. Of the eight giving histories of pleurisy, three showed signs of fibrosis, four showed signs of the old pleurisy only (one being due to a gunshot wound during the TTar), and the eighth showed signs of an old inactive tuber culous lesion of the right upper lobe. A history of pneumonia was ob tained in rixteen workers--in ten prior to commencing work in asbestos, and in six since. Of these six, two showed signs of a thickened pleura only, one bowed merely enlarged lung roots, two had diffuse fibrosis, and in one the lungs were normal. Of the remaining ten, one had a thickened pleura, two bronchiectasis, two diffuse fibrosis, one H. VL IS He. t i 2 254 THE JOURNAL OF INDUSTRIAL HYGIENE commencing fibrosis, and in four the lungs were normal With regard to evidence of bron chitis, and bronchial and pulmonary catarrh, fifty-eight of the 363 worker*. (16 per cent.) showed signs of one . other of these conditions, all ben.g quite mild. Of these, thirty-one also showed signs of diffuse fibrosis, repre senting 32.6 per cent, of the fibrotie group, and eight were in the prefibrotic stage (33.1 per cent, of that group). The fact that the clinical examinations were conducted during the warmer months of the year, no doubt operated to reduce the incidence of these com plaints. Under the circumstances, the preponderance among the cases of fibrosis is the more noteworthy, as in dicating persistent irritation resulting from the dust. Of other diseases, eight gave his tories of rheumatic fewr. and of these, two had definite valvular disease of the heart. In addition, valvular disease of the heart was noted in one worker, but no history of rheumatic fever was ob tained. With regard to pulmonary tubercu losis, so definitely an added risk in sili cosis, this disease group has been drawn up to include all workers pre senting signs indicating a past or pres ent pulmonary tuberculous infection, but excluding cases of old inactive hilar tuberculosis. Under this heading are included not only workers with definite clinical signs of active tuberculous lung infections, or of old inactive lesions, equally definite, but also those workers showingsigns of old apical col lapse, usually attributed to a past tuberculous infection. Signs of the latter ore not uncom monly found in quite healthy persons, and are of no importance unless it is shown that the inhalation of asbestos dust is associated with pulmonary tuberculosis to an increased degree, when such cases, as indicating a group of workers with a latent infection, would assume a greater significance. No close association is apparent, how ever, since only thirty-seven, or 9.9 l*r cent, of the 374 examined, showed evidence of this disease, excluding cases of old inactive hilar tuberculosis, even when those showing the minor changes mentioned above are included. In only four was there a family history of pulmonary tuberculosis; and three out of four active eases belonged to this group. Thirty-three eases were inac tive, of which twenty-one presented no evidence of dust fibroeis, and twelve presented evidence. Out of the 374 persons examined, fourteen, or 3.7 per cent., gave a family history of tuberculosis. Evi dence of active pulmonary tubercu losis was present in three; in two of these three the source of infection appears to have been a near relative. Thus, no outstanding susceptibility to pulmonary tuberculosis was dieclosed, either among asbestos workers as a class, or among ihose with fibrosis,considering the frequency of old healed apical lesions among the general population. We have, however, by no means dis posed of the question. The superven tion of a tuberculous infection on a lung already the subject of fibrosis pro duces an increase in symptoms, pre viously unnoticed or disregarded, and causes the worker to seek his doctor's advice. He is then appropriately advised to give up his dusty employ ment, migrates from the industry, and it is estos >nary 'grec, Toup tion, once, bow* r 9.9 cases even -ngea In ryof 3 out this, inacdno elve ned, ea Evi>rcuo of rtion e. ility diskets osis,-iled era! disvenn a propreand tor's -tely -loyand LB. . hm PULMONARY FIBROSIS IN ASBESTOS WORKERS 255 may or may not accept sanatorium treatment. Thus there tends to be a drift of such cases from the fibrosis producing industry. During the course of the inquiry, information was obtained of a number of persons, previously employed in asbestos, who were ether at home or in sanatoriuma, suffering from cheat com plaints. Where an examination of workers is confined to those at work, a certain number of advanced cases of fibrosis, and a certain number of cases of pulmonary tuberculosis, with or without an asbestos fibrosis, in persons who have either given up work, or who are off work temporarily, will be missed. It is necessary, therefore, to leave this question of increased susceptibility to pulmonarytuberculosis in abeyance,, pending further investigation. With respect toanyincreased suscep tibilityto the supervention ofotherlung diseases in workers with an asbestos fibrosis, the data obtained were insuffi cient to lead to any conclusion, except ss to bronchial catarrh. There are in dications, however, that when pneu monia or bronchopneumonia super venes on a fibrotic lung, the prognosis is grave. ASBESTOSIS AMD SlUC0818 CONTRASTED In view of the relationship between the asbestos fibrosis and silicosis, since they ore both varieties of fibrosis of the lungs caused by the inhalation of dusts, it seems desirable to summarise shortly the main points of similarity and dissimilarity between the two dis eases, so far as has been ascertained. 1. Inhaktiowof asbestos dust, under favorable conditions of concentration of dust and length of exposure, will produce a serious and even fatal degree of pulmonary fibrosis. 2. The type of fibrosis produced, however, exhibits a number of diverg ences from that caused by the inhala tion offree silica dust, and the outcome of these variations is not yet apparent. 3. The divergences noted so far are exhibited in the radiologic picture, and on postmortem examination of the affected lungs, both in the gross morbid anatomy and in microscopic sections. 4. In the latter case the appearances of the asbestos fibrosis seem to be sufficiently distinctive not to permit of confusion between it and silicosis. 5. The radiologic appearances of the asbestos type uf fibrosis, even in the more developed stage, are more deli cate, softer, and more than the silicotic fibrosis. 6. It follows, therefore, that an opinion as to the degree and intensity of an asbestos fibrosis, based on a com parison of the radiologic changes with those shown in standard silicosis films, will be an underestimate. 7. In the absence of a full medical and industrial history, possibilities of confusion of the two types of fibrosis will arise in the interpretation of radio grams. 8. There is evidence that other in organic dusts, containing no free silica, may be productive of this fine type of fibrosis in varying degree. Summary 2. There is a definite risk of the development of a diffuse pulmonary fibrosis in persons exposed to the in halation of asbestos dust. 2. This risk varies directly as the length of employment (and hence VoLU No. * CO O o CTi GO --J CO 11 3 Iv.-V f- a >> m lI r-v , -mi '-.T .>%--!r i-.' .7/ gg-- -; ---w ~ >--**>*-'*- DOoWw r0t2?221l4 jg? 256 THE JOURNAL OP INDUSTRIAL HYCIi.'NE length of exposure to dust), end is unaffected bythe age of the worker. 3. There is a considerable difference -between the least dusty and the most dustyprocesses investigated, and there is a corresponding variation in the rela tive risk of the development of fibrosis in the worker* in these processes. 4. With oontinued exposure to high concentrations of dust, the disease may be fully developed in seven to nine years, and may cause death after about thirteen years' exposure, exceptionally in a shorter period. 6. Fibrosis as it occurs in asbestos workers differs considerably from the disease as it occurs in workers exposed to free crystalline silica dust; it differs in the radiologic picture, and also on postmortem examination of the affected lungs. 6. The more dusty processes are those involving the preparation and manipulation of the raw asbestos (other than crushing), dry doth weav ing, and mattress making. 7. The less dusty processes are spin ning and similar processes, and proc esses, other than dry weaving, in volving the manipulation of the spun yam. 8. Further investigation is required to determine whether there is any in creased susceptibility to the superven tion of pulmonary tuberculosis asso ciated with the development of the asbestos fibrosis. Much generous assistance has been re ceived from many sources during the course It of this inquiry, and for this acknowledgment f is gratefully tendered. In addition to those already referred to, the writer is beholden especially to Dr. S. A. Henry, who did much to facilitate the inves tigation, particularly by his detailed reports on various relevant matters, and. by much Ht or j' OX organization and liaiaon work; to many other* of his colleagues in the different dis 10. tricts, to a number of directors and officials --J of various firms, foremen, and employees; to Dr. W. E. Cooke of Wigan and Professor <0 i M. J. Stewart of Leeds for pathologic mate rial and for much information ae to the progress and results of their own researches into the gross anatomic and the histologic features of the asbestos fibrosis, and the constitution and location of the curious bodies; to Dr. MacGregor, Medical Officer of Health for Glasgow, for various clinical CM and radiologic facilities, and for bis ever present marlins-- to land the aid of his Department, and especially to Dr. H. Seiler of his staff; to Dr. J. C. Robertson for the loan of a radiogram, together with detailed clinical notes of one patient and other valuable information; to Dr. W. H. Bateman for the loan of a radiogram, for some clinical histories, for obtaining and examining several specimens of sputum, and for other aid; and to Dr. J. Rennie, Chief Tuberculosis Officer at Sheffield, for a series of radiograms showing various stages of silicosis. BIBLIOGRAPHY 1. Departments! Committee on Compen sation for Industrial Diseases. 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C.: Demonstration of the Peculiar Bodies of Pulmonary Asbestosis ("Aabestosis Bodies") in Material Obtained by Lung Puncture and in the Sputum. Jour. Path, and Beet., 1929, St, 172. 22. Macktjm, E. L,, and Mjddueton, E. L.: Report on the Grinding of Metals and Cleaning of Castings with Special Reference to (ha Effects at Dust Inhalation upon the Workers. London, S. M. Stationery Office, 1923. 23. StrmnLAKD, C. L., and Betson, S.: Report on the Incidence of Silieoeia in the Pottery Industry. London, H. M. Stationery Office, 1926. 24. StTrusanaND, C. L., and Bntdon, S.: Report on the Oeeurrenee of Silicoeu among Sandstone Worker*. London, H. M. Stationery Office, 2929. 25. Wood, W. B., and Pass, D. S.: A Case of Pulmooary Asbeetoeis, Tubercle, 1929, 10,457. For the geologic and the masu/acturing and industrial aspects of asbestos, see: 28. CacxL, F.: Cbryeotile-Asbestos, its Occurrence, Exploitation, Milling, and Uses. Second edition. Ottawa, Govt. Printing Bureau, 1910. 27. Aabeetoe, its Sources, Extraction, Prep aration, Manufacture and Usee in Industry and Engineering. Berlin, Becker and Haag, 1928. 28. T&osm, E.: A Dictionary of Applied Chemistry. London, Longmans, Green A Co., 1912. 29. Asbestos, a monthly trade Journal pub lished in Philadelphia, Pa. For description of processes, and further discussion on the ineideoee rate of fibrosis, and effect of work is different processes sod also preventive measures, see: 30. Mncwsmiu, E. R. A., and Paicx, C. W.: Report oo Effects of Asbestos Dust on the Lungs and Dust Suppres sion in the Asbestos industry. Lon don, H. M. Stationery Office, 1930. ms rt. a. mo K*. t