Document oD741QerpE6zOjmexLxrVD9kr

c V.l- I i EDITORS DAVID L. EDSALL, M. D.. S. D., United States EDGAR L. CQLLIS, M. D., M. R. C. S., Great Britain ll I j i r ItI 1 VOLUME XII JANUARY. 1930--DECEMBER. 1930 li i, l| PUBLISHED BY HARVARD SCHOOL OF PUBLIC HEALTH Boston, Mass. . -v r THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER * PULMONARY AFFECTIONS IN ASBESTOS WORKERS* E. R. A. Mr:!'.r:vrr.TnEn, M.D. H. it. Mcdicr.l ImyciaT of Factoria I.VTnODUCTIO.V He was treated in the Charing Cross Hos pital for two months, and then returned to RIOR to the commencement of work. After a few months, however, he Pthis inquiry, in February, IP?4?, definite knowledge existed of Ix'cnineill again, and wasre-adroitted to the HnspitrI in April, 1900, where he died. The only two deaths of asbestos workpeor?it-mortcm examination confirmed the about whom there was expert opinion clinical diagnosis of extensive pulmonary fibrosis. There was no evidence of pulmo that the inhalation of asbestos dust nary tuberculosis, and examination of the had at least contributed to, if not. rputirm for B. tuberculosis was negative. caused, the fatal outcome. The first of these, in rctro'p'-' t the The second case was reported by Dr. most suggestive, only came to liidit. IV. E. Cooke iu 1921, eighteen years some years after the occurrence, when Inter (2): full information was unobtainable. All that is known of this case, now referred to as "the Montague Murray Case," is contained in the evidence given by Dr. Montague Murray before the Departmental Committee on Com pensation for Industrial Diseases in The deceased, s woman, aged 33, who died in 1921, had worked in asbestos for IS yers, but intermittently for the last 5 year.*, owing to periods of ill-health. The post-mortem examination revealed, not .nly extensive fibrosis of the lungs, but also murh change due to pulmonary tuberculosis. 1906 (1). From this source, wc learn that: The patient, a male aged 33, came under the care of Dr. Montague Murray at the Charing Cross Hospital in the beginning of 1899. He had worked with asbestos for "some 14 years," 10 years as a cardroom hand, and the remainder in some other room of the factory, "where there was much less dust." He volunteered that, of the 10 people working in the cardroom when he went into it, he was the only survivor, and that all the others had died somewhere client 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 tween the inhalation of asbestos dust nnd fibrosis of the lungs would have been strengthened by the absence of a tuberculous infection. - Cooke's case is, however, of out- 30 yean of age. There is no note a? to the nature of his work, previous tu that in the asbestos factory. sl ending importance, not only because of the discovery of "curious be.'' in the lungs--discussed later -but also, Received for publication l'eb. 17, POO. and of more importance generally, bc- 199 . Jt. It. Mr. MM t ' f i ] \ t f i \ f i1 i i ciur att' pan sitic prill the of v Mr sucl dial use* the: ties nmr C gen' pres Mu: the Deg pub ovet mil bv t '?: Gric grot tic, acre It Met drew wor1 in o Thibcei sen? logi I fibrt lous turn itirvi othi dll-:' cxis V..' t N.. J rUI.MONAltV FfJ'.RfK<io 12: Asiii-.s n Jw cause its publication again directed This :-.l that time the third of attention to the possibility that inor which Him F.acbuy f -p.irfmcnt had ganic dusts containing little or no free knowledge, was, lee.-,ever, the first in silica may be productive of extensive which the four r--e:ili:il conditions, pulmonary fibrosis. Of these dusts, necessary to establish a relationship the silicates form a very large class, between the inlmlat ion of asbestos dust of which asbestos is but one example. and the development of fibrosis, could Many other members of the class, be demonstrated. These conditions such as the feldspars, kaolin, French arc: chalk, and pumice, are extensively used in industry. The importance, therefore, of delimiting the potentiali 1. Work involving exposure to asbestos dust. . 2. The existence, ritnonstrable clinically 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 and radiological!)-, nf a definite pulmonary fibrosis. 3. The aba-nee of precious or present in fections known to rsii-e pulmonary fibrosis --t.g., tuberculosis, influents, or pneu- rooms. ' Murray ease, although contained in the evidence presented before the Departmental Committee in 1906, and 4. The al's-nec of previous or present work involving exposure to other dusts, which might enuse pulmonary fibrosis. published in 1907, were liable to be These conditions being fulfilled, a overlooked in the mass of important relationship between the inhalation of material on industrial diseases elicited asbestos dust and the development of by that Committee. the pulmonary fibrosis may be pre Since Cooke's case, Dr. X. M. D. sumed. Grieve has made a careful study of a The importance of establishing group of asbestos workers in his prac whether the supervention of this dis- tice, and has courteously allowed .case in an asbestos worker was an access to his records. exceptional occurrence, or evidence of In February, 192S, Dr. MacGregor, n grave health risk in the industry, was Medical Officer of Health for Glasgow, now apparent, and steps were taken, drew my attention to an asbestos forthwith, to obtain prima facie evi worker who was receiving treatment dence in proof, or disproof, of the exist in one of the hospitals in that city. ence of such a risk. This case, the details of which have A number of workers in asbestos been reported by H. E. Seiler (5), pre were selected and examined clinically sented, both clinically and radio- and radiographically. The findings logicnlly, signs of a diffuse pulmonary invited further investigation through fibrosis, with no evidence of a tubercu out the industry, with t he result that a lous infection. On further investiga comprehensive inquiry involving the tion into the patient's industrial and investigation of the different processes medical history, no presumptive cause, in relation to the evolution of dust, and ocher than the inhalation of asbestos the examination, both clinical and ra dust, was found to account for the diologic, of r. erkers, was undertaken existence of the fibrosis. during the year 1928, commencing Vo*. II No. I 200 THE JOURNAL OF JNl tFSTfjfAL HYGIENE with the carding, spinning, and weav ing processes of the industry. In the meantime, in March, 192*?, the death of an asbestos worker (one of Dr. Grieve's cases) occurred in nnoiher part of the country, and, on post mortem examination, a condition of widespread Gbrosis 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 (0) reported a fatal case of fibrosis of the lungs occurring in a native work ing in an asbestos mill in southern Rhodesia. In order that this brief surrey of the events leading up to the present in quiry may be complete, it is necessary to renew 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," 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 chic to sickness, etc. Also inquiries were made of the Canadian government ns to the conditions in the asbestos quarries and mills in that Dominion, evidence of increased sickness and mortality rates among the workers, r'"! my methods of ventilation which In'! h' <'n found of especial value. 'I |io iccU!t of this investigation did '( conclusively prove that asbestos p'.'s--"rcd injurious properties, but it pointed to the probability that such was fhe case. It is interesting to con sider why it was that no conclusive pro"f one way or the other could be obtained, then, as to the injuriousness of s'hestos dust. Some, if not all, of tfif* factors which affected the position then are, in varying degree, continu ing factors, and have an important bee ring 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 hemming suspected as a cause of indus trial di'^nse? The answer appears to be that in the past it was not practicably possible to ohinin 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 had 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. Fieeiso knowledge of the morbid affections of the lungs produced by the inhnbifmn of dusts was more frngincn- J.l.'U. War. i 1 / J i j i t I i i i I i i t tary th was ck: evidence mission Quarries porting know wl eontnini a patho1 though Beattie may occt or two tl: definite effects o lungs (8) In 191 both its t aspects, so far fro status of the dingo lungs, wr In add urc of c\: dn*ty prr pletc as i in niodif. duration tions re.-i the dust, much mo intcrvenii present u to again. Anothe still ten'! dclcteriou dusts, is t mortality of the d,,* dust cnco occupntio value in into two Vol. t* No. 1 iiich did -'tOS -t it. uch 'on-ivc I be tess . of ion nu:int icir ion n.aon: led led i.il -15- I t ii i| I 1 of !n1S- ch P cn he ee rm < of !-d :o to is i d< et i- PULMONARY FIBROSIS IN ASM^n* IVORKMIIR 201 t.-iry than it is today. The position was clearly 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 has produced some definite evidence as to the precise effects of some of these dusts on the lungs (S) (9) (10) (11) (12). In 1910, radiography of the lungs, in both its technical and its interpretative aspects, was still in its infancy and, so far from having attained its present status of beiDg an indispensable aid to the diagnosis of the dust diseases of t he lungs, was an unused ally. In addition, the existence of a meas ure of exhaust, ventilation in the mostdusty 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 obscure 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. This rate, while of great value in separating dusty- industries into two great groups--those which show an r rr-t nun lalif.y from phthisis, and tlio'-o 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 a means of classification in the latter group, but also tends to distract attention from it, .and to result in the associated dusts be ing dismissed os more or less innocuous. Evolution of dust is only one factor, though an important one, which may rani" vniinUons in the phthisis mor tality rate iti different industries. Wages, hours of work, aggregation of workers, amount of food, housing, and other social and environmental condi tions .are, however, powerful influences in the smno 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 tlm lungs, (he singular attributes of pulmonary fibrosis, the most impor tant of tlm 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 goes 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 acute illness h.a* caused a fatal termination, Yol. II Ns. I ' ' * ! 202 THE JOURNAL OF INDUSTRIAL HYGIENE a stage is reached when the Fine* nn ri'.-lwstns dust has a totally different do little more than maintain life; and jiliy-icm-liernical constitulionfrom that the shortness of breath i;- 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. bad to b taken to keep an open mind, While more or less acute cas** of so f" not to be unconsciously 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 asso parable in some degree to those of ciated 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 AsnESTOS ANO THE ASBESTOS Industut Asbestos nary fibrosis, especially in its early The term asbestos is a collective stages, or if complicated by tubercu name, of no-definite raineralogic sig 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 pede, though to a less degree than in facility with which they are capable of 'the past, any investigation into the being split up into long and flexible effects of an industrial dust upon the fibers, which can be spun like cotton lungs of those exposed to it; but prior and woven into cloth; oo their resist to the War, although there were certain ance to heat 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 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 problem afresh, and with complete detachment, because of the fact that expect cd to command. Consignments of asbestos of the Fame g'-n-ral variety, hut with diffrr- 1.1, n. liar. 19)9 I i I t i t i i i i i i I ent coun mixed in manufac tile may Rhodesia frequent! such as a: mixed. Fractic under th merce, is fibrous n hornblem most im strictly, TADLE MtKCF.At ORocr Scrpvntinr AmpUitioto (bornblende) term asbe blende. ' distinguis alogically Serpent a hydrate taining pr pcrcentaglow percc is very si attacked 1 of the wor derived f variety; t from Soul The air ctics cont Vol. ts No. J 1'ULMONAUY l-lI!U(>rii.S U: A;:n! Ous UORKKUS 2in ent countries of origin, arc frequently mixed in the preliminary proces^-a of manufacture. Thus Canadian chrysntilc may be mixed with Russian, or Rhodesian chrysotile, and so on. L^ss frequently, totally different varieties, such as arnosite and chrysotile, may lie mixed. Practically speaking, all that goes under the name of asbestos, in com merce, is cither fibrous serpentine or a fibrous mineral of the amphibole, or hornblende, group. The former is the most important commercially; but strictly, the mineralogists confine the 1 lined water, and usually more cal cium. aluminium, and iron. Members of this pump are resistant to acids, but an- more difficult to spin, some bring quit* unsuitable for this purpose. 'I lie niu'-f. important members of this group pm crocidolite, arnosite, and ttrinnliln. (Jroci'Milo and nmosite are mainly silicates of iron, the former having a beautiful lavender-blue color, the latter being brotvnih-gray. Roth are spun and the yarn is woven into cloth for various purposes, such as acid filter ing, and for making into insulating TABLE 1.--COMPOSITION OF SERPENTINE AND AMPHIBOLE VARIETIES OF ASBESTOS MINERAL oaoor VARIETY rsncrKVAOK or SiO, Al,0, FcO FciOi Com MrO C*0 Na,0 K,0 bined Water Serpentine Amphibole (hornblende) Chrysotile 39-42.5 0-3.7 0.7-4.4 33-43 0-0.35 ... 13.3-18.5 Crocidolite 50.5-52.1 O-l 35.5-37.4 0-3 0.75 0.2-9 . 1.6-4.5 Arnosite 48-53 1.2-9.4 34-44 0.7-6.4 0-2.5 2-3.8 Trcmolite 57.2 0.9 3.2 22.8 13.4 0.6 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 calcium, & high percentage of combined water, and a low percentage of iron. This variety is very suitable for spinning, but is attacked by adds. 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 ma! tresses, ns well as for other pur poses. Both are produced extensively in South Africa, from which quarter all required commercially is obtained. Arnosite, a comparatively recent dis covery, is found there in very large deposits; its use is steadily increasing, the initial difficulties associated with the manufacture of textiles from this variety haring been overcome. Trcmolitc, 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 Vot. 1* No. * 204 THE JOURNAL OF INDUSTIiML IIVC!IENE sources, shows the main difTcrcncos 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 spin ning, 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, some of which give rise to an increased amount of dust. About four-fifths of the world's pro duction of asbestos 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 lias been responsible for the phenomenal expan sion of the industry as a whole. The spinning and textile section has also shared, because of the extensive use of the yarn and cloth 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, the 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, nnd by 1925 to over 330,000 short tons (15). The imports of asbestos (all grades) '..to the United Kingdom rose from 18,591 tons in 1922 to 33,520 tons in 1927 (10). The figures for 1927 refer to Great Britain and northern Ireland only. Of these quantities 8,844 tons and 3,794 tons, respectively, were rrcvporf'>!. Tims the consumption of asbestos in (his country trebled within five years. ' The Industry On considering the uses of asbestos one is nrtnnMiod, not only at the wide . range of articles manufactured from this mineral, in greater or less propor tion, but alo at the diversity of indus- . tries which nowadays find its use neee.ss.ary, either in the form of the raw material, or as manufactured articles. Evidently, therefore, with the multi plicity of processes and dusts encounterod in lh ramifications of the indus try, discrimination would have to be exorcised, ami some limit set to the processes included in the inquiry. 'The processes selected may bo divided, roughly, into 1. rroeevc involving the manipulation of either pure, or admixed with a email proportion of cotton, or other vege table liber. 2. Process involving the manipulation of a-l'cstos t"!"'tlier with other dusty ma terial". 3. I'r'--r---" involving the making up of rlnfli into other articles. Otniip I entails exposure to asbestos dust mainly, end to cotton, or other vegetable du=t, very slightly; group 2 entails exposure to asbestos dust in very varying amounts, and also exposure to divers other dusts, such as brick dust, magnesia, kicsclgulir, fossil meal, and cement; in group 3 the exposure to asbestos dust--provided no other as bestos processes arc being carried on in the vicinity--is, in the majority of cases, negligible. Processes belonging to all three groups may be carried on in the same factory, and workers may transfer from one department to another (tWI). j. i. n. U.y. W30 , 1 ' : t. i ( 1 I I PUL Inve-Mpatio tion of the cflc possibly prod', corolle.ry, wou! in the absenc* effects of the sc end moreover calculable vai results. For t because the Cooke's, Grie\ all occurred ii group 1, it wc to exclude, as f inquiry all wor flucnce of mixe not employed i groups 1 and 3 The process are the crushi opening, inixii doubling, plaill ing of nsbcstr operations inc included is mat filling is asbeste of some insuiati dust produced i The carding have many po the corrospom cotton industr modifications r by the different the asbestos f are aided by aor other veget from 2 to 10 cotton is adder special purpose is carded and s of vegetable fit yarns contain or metal wire. Asbestos yar voi. i: No. 5 M|.!in!; :.in ' a.'best 03 the wide red from :s proper* of iudus- its use >f the raw I articles, he multi* cncounhc indusve to be t to the irymay be nipulntion ed with & tlier rege- nipulation dustr ma- . of asbestos or other v; group 5 dust in 'O expos es brick sil meal, 'osurc to tiler asrried on jority of clonging icd on in ers may vent to ITMIONAK Y I ini'- i ' '< i' \Yci:i,i.i:s j i j ftu c: Ui:nti'iii into I In- ini i i' >;>' (I' ' ' ' iTI!* ff fabric*', v.hich llrur- lion of the ('(frets of mixed dirt". v. iiit<- :1 i : U""d for a mtdl.ii ndu of pnr- possibly produclivn of some 'd p' b-,!. I.msdod together, are made corollary, would lose much of its value jriio re;.'-- for use ns steam packings f in the absence of knowledge of the and oM.i'r purposes. The interstices effects of the several component. du'ts, end r'ut"r of the rope may be filled and moreover would introduce on in witb other materials such as talc, oil, calculable variable into the final or graphite, depending on the precise results. For these reasons, and also tire In which the rope is to be put. because the Montague Murray case, Asbestos mattresses, used for blan I Cooke's, Grieve's, and Seiler's cases keting steam engines, and for other I nil occurred in processes included in insulating purposes, arcinadc of asbes I group 1, it was considered advisable tos cloth stuffed with asbestos fiber. I to exclude, as far as possible, from flic Th" stuffing material may be, however, < inquiry all workers exposed to the in ring wool, magnesia (containing apfluence of mixed dusts, and all (lm-.e provim-tcly 15 per cent, of asbestos not employed in processes included in fiber), or kiesclguhr with a small per groups 1 and 3. centage of asbestos fiber. The man The processes included, therefore, ufacture of mattresses filled with arc the crushing, preparing, sieving, mixtures of asbestos fiber and other opening, mixing, carding, spinning, mat . rial- has not been included in this doubling, plaiting, braiding, and weav portion of the inquiry. ing of asbestos, together with the The shortness, slipperiness, and lack operations incidental thereto. Also of strength of the individual asbestos included is mattress making, where the fiber, ns compared with cotton, flax, filling is asbestos, and the manufacture wool, silk,and other textile fibers, have of some insulating materials, where the been the cause of much technical diffi dust produced is asbestos. culty in manufacture. The efTorts of The carding and spinning processes manufacturers to cope with these diffi have many points of resemblance to culties, together with those due to wide the corresponding processes in the variations in the physical properties of cotton industry, but with essential the raw material, arc reflected in the modifications and restrictions caused methods employed by each. For these by the different physical characters of reasons, and because of the great num the asbestos fiber. These processes ber of patented and special products are aided by an admixture of cotton, manufactured, one finds considerable or other vegetable fiber, and usually differences in detail in the processes in from 2 to 10 per cent, by weight, of use. cotton is added. More rarely, and for The majority of the processes men special purposes, long-fibcrcd asbestos tioned result in the evolution of dust, is carded and spun with no admixture although by no means to the same I of vegetable fiber, but usually asbestos extent. Differences in plant, quality yarns contain a core of cither cotton of asbestos used, methods of manufac or metal wire. ture, type of finished article, and extent . Ash 4'9 yarns are not only used for of application of exhaust ventilation, i. n. II IT. IMO ( Vol. U N<.( 206 THE JOURNAL OF INDUSTRIAL HYGIENE all 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. | Populatioruil 7?fsfc.j--A calculation of tUeTotaTnumber olwoorkers employed in the processes already enumerated ns TABLE 2.--DISTRIBUTION, ACCORD ING TO LENGTH OF EMPLOYMENT, OF (A) 775 WORKERS ENGAGED IN ASBESTOS PROCESSES AND (B) SELECTED SAMPLE OF 363 WORKERS (A) (B) TM. ZlfFLOTZD fi.. oz hz u V *cu oz OzHH c hi 0-4............................... 5-9............................... 10-14...................... . 15-19.............................. 20 asd over.................. 483 62.3 200 25.8 51 6.6 24 3.1 17 2.2 89 24.5 141 38.8 84 23.2 28 7.7 21 5.8 Total.......................... 775 100.0 363 100.0 included in this inquiry, but excluding those engaged in processes included in group 3 in which the exposure to as bestos dust is negligible, gives a figure of approximately 1,600; if we could add to this the number of workers engaged in handling pure ash--,-os fiber only, in the preliminary Btagcs of the processes included in group 2, we should obtain the total population at risk from the effects of asbestos dust it self. Unfortunately, tin's latter figure is unobtainable; but a rough estimate, and most probably an overestimate, is COO. Tim*, about 2,200 appears to be the total population at risk in this country, for the purposes of this in quiry. Tlii^fi'Mirrv however, does not iqrju'lo th l -rpe number of workers engaged in the processes in group 2 wTii'-h involv' d exposure to the influ-'-' one? of mixed 'lusts, of which asbestos is but on, end commonly not more then 20 p>-r root, of the mixture. This estimate of the population risk, although it may be excessive, is useful, since it enables us to judge of the adequacy of the sample of workers crammed, and to apply more correctly the incidence rates of any pulmonary affections di'closed by the examination of the sample (30). The sample examined (after eleven cases are excluded of fibrosis and prefibrotic conditions due to causes other than the inhalation of asbestos dust) numbered 303, representing 1G.5 per cent, of the population at risk, esti mated as above. The manner of select ion of the sample must be referred to, since just- interpretation of the results depends upon a due appreciation of the relationship of the sample to the whole population at risk. The principle of selecting primarily those longest employed was adopted; but regard was also paid to the other end of the scale, so as to obtain infor mation ns to the length of exposure to dust necessary hefore 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 maximum information would be obtained in the shortest lime. Tnhlc 2 shows the distribution, according to length of employment (not necessarily in oue factory), of 3.1. If. m>x, mo 1 j i 1 } j PULM 775 workers eng: under review, anworkers, distribu The enormous pi cnlly of workers years in these pr is also the very workers employe Comparison of table shows the method of sotccti examined in eact employment gro greater proportio which could ha\ each particular tary exception, a! at work on the d; Not only the sity, of radiogra the chest in in effects of dust up emphasized reps Pitchford, and Departmental Cr sation for Filit standard of radi as Vatkins-Pitc.' radiograms must factory." Indiff since it is the fi which is being st- In a general i which involves workers in facto scattered over t practicable, nor sidcring the spe inquiry, for radii all the workers r cation of work i the absence of a this purpose, c:t unconcern, rspe. infrequent, the f Vrt. 15 No. S pulmonary i: ` - -tits WOliKKUS :<>7 775 workers engaged in the procc7"-~ ; ,-r'.r ijirb is equipped with the i. ars to in this iiis in>cs not orkcrs oup 2 influ`be.xtou i under review, and of the sample of workers, distributed in the same wav. The enormous preponderance numeri cally of workers employed under fiveyears in these processes is striking, ns is also the very low percentage of workers employed ten years or longer. Comparison of the two parts of the i ,-r: --iv X-ray plant, and where the r, rvic^s of a consultant versed in the of radiography of the lungs nre available. Furthermore, it must not be overlooked (hat such examinations are voluntary, and not, ns in South Africa, compulsory. Moreover, re peated and protracted examinations moro table shows that the effect of this only result in the exhaustion of nil t method of selection is that the number concerned, and much dopoiuls on tho ion at ivc, is <lge of f i i examined in each succeeding Gve-ycnr employment group is a progressively greater proportion of the total number willing (o-npcriitioii of i-mployem and employee-', idnce the only iiiiTiil.ivn in a d'-'irc to further (ho common welfare. orkcrs which could have been examined in Kmliography, llierefore, lion a differ redly each particular group. With a soli ent function in tln-so ini|iiirii-n, than ion;try tary exception, all those examined were when it is applied to individual cuki-h nation at work on the day of examination. for compensation or other legal pur Not only the value, but the neces poses, This function is- not flint of cloven sity, of radiographic examinations of replacing careful clioir.nl exaiiiiiiaLioiio, 1 pro- the chest in investigations into the as has bc'-n recently forcjilmdowed (IH, ot her effects of dust Upon the lungs, has been . 4fl), hut primarily thiiL of being - dust) emphasized repeatedly' by Watkins- an indi::[i<:fiHabl<! aid In di/i|/iinoi( 5 per Pitch/ord, and reaffirmed by the . -pi.oially of doubtful canoe, in tho Departmental Committee on Compen determination of coiriplie.al.iog Ineioiut, sation for Silicosis (17). A high in measuring the extent and pnigrceM ed (be ecia'leto arily >ted; iher ifore to :mi'il.nr tvas standard of radiography is essential; of the disease, iq locating the point at as Watkins-Pitehford phrases it, the which (he earliest radiographic signs i radiograms must be "technically satis appear, and finally as n check upon ( ) factory." Indifferent films are useless, the human factor presented by the since it is the fine detail of the lung examiner himself. which is being studied. The examinations (except one) were In a general inquiry, such as this, carried out. at each factory, in a room which involves the examination of set sport- for the purpose, suitably * workers in factories, large and small, wn-rned. and with the necessary I scattered over the country, it is not appointments. On occasions the noise practicable, nor is it necessary, con of trafiiu or from the adjoining factory sidering the special purposes of the was a hindrance, but in one way or inquiry, for radiograms to be taken of another those difficulties were over `>y, all the workers examined. The dislo come or minimized. be cation of work in a factory, caused by Ail the selected workers were exam the absence of a number of hands for ined by the writer. At three factories, on, this purpose, cannot be viewed with however, a number of workers were ent unconcern, especially when, ca is not examined jointly with Dr. E. L. Middle of infrequent, .the factory is ireraote from ton. His far-reaching experience of the IT. voi.a 1030 No. t I 203 THE JOURNAL OF INDUSTRFAf, riVGfE.N'J-: ft FULM< i pathologic changes in the lungs, pro these, it diminishes in intonsit}', but the fibrosis may t duced by the inhalation of various still persists. In other words, we find perfectly normal dusts, was of great value, and his tacked on to the paravertebrat dulncss the problem of c assistance was much appreciated. an area, above end below, of impaired forward. In oil Every effort was made to complete resonance, which is much more exten preexisting root c! I the clinical examination of the workers sive than that usually associated with an industrial com: before the onset of winter introduced oid inactive hilar tuberculosis. cut, or the lungs difficulties due to ephemeral bronchitis, Impairment of the percussion note seat of cinphystn colds, and influenza, which would tend to obscure the main issues. Thus the clinical, and two-thirds of the radio graphic examinations were completed was found to be constantly more marked in (he right ride; in fact, at first it was thought that in the earliest degrees of fibrosis it was confined to i i chitis, or of defi lesions, or there pleural thickenin' pleural effusion, by the middle of November, 1923, prior that side, but later, and more extended to the commencement of the influenza observations le-<| to the conclusion i have been noted i gation, and other epidemic early in 1929. that the r:ir)* st detectable cases are mind- bilateral, although the signs on the left Although in m> Clinical Examination side are tenuous. dust fibrosis, if nu Percussion This change is so constant that it has been adopted as f he most reliable single he confidently < with the aid of ra The inhalation of asbestos dust clinical sign presented by this type of originates changes in the lungs, which pulmonary fibrosis, and no case has i t admitted that t very difficult whi may be looked upon as n measure of been classified as fibrotic in its ab comparatively sli the eHorts of the living tissues to repel, sence. ) produced bvothf or incarcerate, the irritant particles of Considering the frequency with dust. These changes modify the per which signs indicating what may be notinccd and difi these cases have , cussion note. It is true that the note termed "enlarged roots" were found in among those ex elicited may be similar on both sides, asbestos workers, it may be that para numerically they but the note is not normal. It is vertebral dilliuts is one of the earliest The first- of th thinner and higher pitched than nor signs produced by the inhalation of fibrosis has been mal, and there is a sense of resistance asbestos dust, indicating congestive ( alrcndy emphy.- imparted to the plexor finger. In changes in the root areas nnd u choking that, at any rab other words there is & diffuse, but of (ho lymphatics with dust. Reflex asbestos fibrosis slight, impairment of resonance. impairment of note, due to irritation of changes get the This alteration in the percussion note, however, is more difficult to recognize because it is bilateral, nnd the lung tissue by dust, is, however, an attractive explanation. It docs not follow, of course, that workers present \ i* diagnosis of the f is impossible. N the problem of extends over a wide area; consequently ing t lies0 sign will ever develop a defi fibrosis implant' the aid of contrast percussion is denied. nite. asbestos fibrosis. sematous chest I 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 \ culty in this itv that it can arise i chest from apex to base on each side. sis not only may be modified by circumstances. It will be found that the extreme changes produced by some intcrcurrcnt f The second t; apexes remain clear, but below the lung dieaset but, ab initio, will vary t been n source < apexes the impairment is general. It according to the state of the lungs be diagnosis is the increases over the root areas; below fore the onset of the fibrosis. Thus, J. l. n. My. 1930 { i V extensive bilatei Vrt. iNo. i \ l- nnuosiH n; r.i . i- -I: i:i .i:s ill!' fibrosis m:iv In; implanted upon n perfectly normal clicr-t, in wli'mli the problem rf diagnosis is str.'iigMforward. In oilier Rises, however, preexisting root ch.ingrs, so common in an imluslri.il community, may lie pres ent, or the limes may be already the scat of emphysema anil chronic bron chitis, or of definite old tuberculous lesions, or there may be a massive pleural thickening, the result of nn 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 eases the 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 eases 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 ease of the asbestos fibrosis, until the fibrotic changes get the upper hand, clinical diagnosis of the fibrosis in these eases 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 wems likely that it can 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 |,, -.If.| I III < l,ll|n j Tint (lltTf i'l an c- i-ir iv' 11!- i*= i'l rKir enough, and that run t tJ il. burnt due (ft ashesl(i is strongly niOT-sfed when exam in al ion of I lie lower portions of the lungs shows (lint (hey are comparatively slightly nfTi-Hed. Further help in ihiri' r;io^, of course, may be obtained from I be history and symptoms. 'Clio fliird type, also rare, is that in which changes following an old massive pleural effusion on one side so obscure tlic physical signs of any dust fibrosis as to render that side useless clinically for diagnostic pnr|vises. If the siilo :i (folded by (he pleurisy happens to ho the right, the radiographic picture is nlso curtailed by the normal partial obscuration of the left lung base by the heart, shadow. These ft,roe 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 fibrois may be masked, in greater or less degree, by changes due to other disease. Only pissing reference need be made to the other physical signs found in the asbestos fibrosis, since they do not differ materially from those presented by silicosis. Chest expansion is dimin ished and mny be reduced to one-half inch or even less in advanced cases. Retraction of the apexes is common, and sometimes shows a peculiar feature differentiating it from that found in fibroid phthisis. Instead of the im mobile and 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 (he anchoring of normal apexes by fibrous tissue in the lower portion? of the lungs. Some confir- VoLIl Ko. 210 THE JOURNAL OF lNOrSTlUA I, HYGIENE mation of this was obtained railiologicalif. 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 inspirator}', and often becomes less and less audible as one approaches the bases. Transitional phases between this and harshened breath sounds and pro longed expiration are not uncommon, even in the same chest. The latter may be noticeable 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 fibrosis 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 permanent, In the lung, and is depend ent, inter alia, on the extent of (lie fibrosis with its associated pleural thickening--cltangcs due to past dis ease, catarrh, or other intorcurrcnt affection, and to the degree of coinpcnsatory emphysema present. Symptoms ' The symptoms exhibited by these rr>ee? of fibrosis, as might be expected, clos'-ly resemble those of silicosis. The distribution of the main symp tom0, 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 t hat one or other of the symp toms complained of might be assigned to causes other than the fibrosis, such TABLE 3.--distribution of four COMMON SYMPTOMS, AND OF CYANOSIS, AMONG CASES OF FIBROSIS PTMrTOM a CAS!:s in u z WH icn 5<? 6TU1'TOM WAS MIE3ENT H U oz No. Per Cent. Coogh............................ Cyn.no?!).................... Dyspnea....................... Expectoration.............. Faia.............................. 91 93 91 91 94 54 59.3 52 55.9 47 51.6 31 34.1 10 10.6 * Excluding those in which the presence of the symptom is referred to other causes. as n complaint of shortness of breath in a case with a past history of mild thyroid intoxication, or of dyspnea associated with obesity. Uctweon ."0 and GO per cent, of the ca*s complained of cough, or of short ness of hre.ath on slight exertion, or showed some degree of cyanosis, whereas only about one-third com plained of expect oration, and onetenth of pain, or discomfort, in tho chest. Also, while 14.G per cent, ot the cases hud no complaints and showed no cyanosis, and only 3.4 per s. i. u. Mjr. IMS IT i 1 cent, presentt ! were cynuoset two, three, or i Clearly, no or the presen infallible ind tI of fibrosis; bi them, shortr exertion, and I in an asbesto tive, in the ; cause. Ncvcrtholc fibrosis may l plaint made, tressing, are the introspet Slight degree to no svmpi an intercurrt remaining sc amply suffice Cough w.as tom, and war weeks after dusty proces find the du while in the \ \ lasts for a fer Is disappears, this effect on a very lieav; The dust sc irritant ini tk t who had pre card rooms, affected by t were unalTe Certainly :isJ asthmatic :v I cotton card i who migrate (`hard wnst ! i asbestos c:ir irritating cfl i Vo!. No. i . .-sc 'Pcctcd, silicosis. i syrup. -' wliicli for con- - A few on the > syrup- 'signed s, such : [ j j ; j I I FOUR OF rs ix IOI TOM 'CSZXT 59.3 55.9 .6 'COCO uses. h in nild nca the *rtor in, m It'tm of 1(1 cr ir. :o i } / ) ( i / i ruLMONAiiY rmuosis ir '>':'' i I"'; \U)KKi;i!S 211 rent, presented nil four complnmfr ami uerc cyanosed, 60.C per cent, presented two, three, or four of the five item'!. Clearly, none of the four complaint?, or the presence of cyanosis, can he nn 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, arc 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, Etated that they were unaffected by asbestos dust. Certainly asbestos dust docs not cause aaUiiiiatifl attacks like those seen in col l on pin) room workers. One iiiim, who migmUil frtmi a coll on rnril room ("lmrd waste") niiui yearn ago In an asbestos card room, on account of the irritating effect of the dust, does not fi"'1 iliirf. irritafirii:. but I' (hi-. '-iy r cm.il work with a coll on rfii'ii' ('i-- h" occasionally docs) with out prprioifriting a coughing attack within sii hmir or two. Although he puffers from winter cough and some Fhor(n<' of breath, lie stated that his health ha? hern much better since the change. Asbestos dust, therefore, has only very mild powere 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 I he assumption that tbedust 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 itis prcsentonly in the morning on getting up, when after rather n sharp attack of coughing, a little viscid sputum "like an oyster" is brought up. A similar bout may occur at night after ceasing 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 invnrinbly stale that the cough has not become worse since working with nshestos. One worker succinctly de scribed the cough as "first in the throat; Infer catches the chest." r.rnniilly, Mum cough chuhcb very lit lie iiieonvenienen mid limy jinmi imnuliiTt! iiulil the ilovotiipmetil of hiiiiiii other symptom directs attention to tho general state of health. Thus, out of Vol. 13 No. I 212 THE JOURNAL f'F l.'.'D*'- I l>l\L IiYOJF.NE sixty-six eases of fibrosis, in tliirtvthree (50 per cent.) the cough wa* stated to have preceded the onset of shortness of breath, in twelve (IS.2 jit cent.) to have developed contempo raneously, and in twenty-one (HI.8 per cent.) was either not noticed until aflor tho onset of shortness of hrenlli, or, although tlio latter was complaiinil 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 all cases in which this complaint was mentioned, the exciting cause was, primarily, some disease other than the fibrosis--c.g., in one, it was due to pulmonary tuberculosis; in another, it occurred only during a prolonged attack of pleurisy; and in a third, the hemorrhage was gastric in origin. Cyanosis, a valuable sien 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 wltich it is often associated in these cases. Cyanosis in some degree was noted in 50 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. I'ain in the chest is rarely omiplaiued of, and then it is usually de scribed as "tightness of the chest," "soreness," or "aching." It was noted in 10.6 percent, of the cases. Well-marked clubbing of the fingers was noted in a few cases. Tho general nutrition is hardly affected, except in the latest stages. Only ten (10.5 per cent.) were noted os being thin. Iti one, the nutrition was very poor; in twenty-one (22.1 per cent.), fair; rud in the remainder of the cases, gnn-l. . . Radiography ' Iladiograrns of the chest were ob tained of 133 workers, or 35.5 per cent, of the number examined clinically. Of ilicse, over 100 were taken by Dr. Jv W. Twining of Mancliesl'T, ami Dr. N. Tattersall of Leeds, and tho remainder (except one) by Dr. F. L. Henderson of Glasgow. To all three, 1 rnt much indebted. Dr. Twining and Dr. Tattersall have devoted many hours to the joint study with the writer nf the radiograms, and have drawn firrly on their wide experience of radi(.'graphy of the chest in furthering the purpose of the investigation. Dr. It. S. Paterson of Manchester, too, nddM 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 (lie earliest negatives studied with Dr. Tattersall, a characteristic slight obscuration of the lung fields, a general lack of transluccncy, was noted. This appearance, for want of n better term, was denominated ns "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 j. i. n. Mar. mm ; ! j' ; i I } j j j 1 1 \ ' '. J j J ! j 1 ' * j i } varying si mid-rori''? There r the fine : character: (in a pci Aug. 2, : there hu* opporluii: every asp views me tion of al In gear eat stage: logicsl'.y, tippling i provable saw it cor and after to detect Some < grouped marking; sire of a ; to lesion In t!ie a; group! c lobule, t They cer will) the patholo? The a., mid-fielc conloiis, apices. On th less dens easy to '. I thick v 1. A linear s 2. i'r np|Tiir: 3. C ftriatit d. C displac ins ics The across Vot. i; So. s ascs. obcent. a llr. Dr. and the ' - L. hrec, ining oany riter rawn radi : tho ;ter, - final vilaj-, an' , i. is was i ll is race fi'usc sbes- oaly osis. with light .oral This erm, Dr. ted to it ce." n to " of t. u. K i I I l /) i ( \ i t * i ( PULMONARY FIHllOSIK 111 AfM'-M.-: ('< 21.', varying size seen in the striation in tiic mid-zones in some of the films. There was general agreement as to the fine and delicate nature of the characteristic mottling. Dr. 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: In general my opinion is that the earli est stxgcj are not characteristic radio logically, bat that the stage of tine dusty stippling is almost certain to be eventually provable as an early asbestos lesion. We saw it constantly in a large ecrics of films, and after a little experience it ie quite easy to detect it. Some of the other eases showed few grouped lesions, like rosettes or leopard markings, each component being about the size of a primary lobule. These are similar to lesions sometimes seen in tuberculosis. In the asbestos cases I regard them as being groups of primnry lobules making up a lobule, the walls of which are infiltrated. They certainly seem to correspond in sire with the macroscopic lesions seen in- the pathological specimen. The advanced eases show heavy basal and mid-field mottlings, common in pneumono- coniosis, with a tendency to avoid the apices. On the whole the lesions are distinctly less dense than those of silicosis, and are less easy to group into well-defined stages, but I think we can recognise: 1. A very doubtful stage of increased linear striations. 2. Fairly definite fine dusty stippled appearance. . 3. Coarser mottling with increased linear striations. 4. Gross 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. Tin- [.uli'^i.-ijiliic appearances in the earlier rtnrj - .110 most mark'd on the right side :>i. f ho base nr in (he central muc. This corresponds with the clin ical findings. This preference for tho right side has been noted also in silicosis, by the South African ob servers. The cases showing radio graphic signs of a dust fibrois have i'cen classified in three broad groups. This grouping, although unscientific, is convenient practically, considering the main purposcof this investigation. Indeed more precise classification based on the particular radiographic changes noted might well be mislead ing at the present time. Miirh combined clinical, radiologic, and pathologic study is required into the whole subject of these fine types of dust fibrosis, which have been 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 delations 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, rcprc'cnMng the purely peribronchial variety of fibrosis, might be added; or't may be that all dust fibrosis will be found to approximate more or less closely one or the other of these two Vol. IX No.* I 214 TIIE JOURNAL OF JNI>US I'M ( AT- HVGILNK types. These types ere (1) that pro duced by combined silica dust, an example of which is seen in nsbe-to 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 orthoclase 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 (i.e., true sili cosis), he states: Moreover, the eoarae fibrosis of silica gave clear interspaces of normal lung, while the fine fibrosis presented uniform granular mottling leading to the conclusion which is probably erronoous that the actual develop ment of fibrous tissue was greater in a nodular fibrosis as silicosis than in a general ised fine fibrosis caused by ailientes. To me it appears that the meclinnical damage to the lung is greater in a fine fibrosis than in a coarse fibrosis when both are. well developed.' The evidence obtained in the present, inquiry amply confirms this general statement. On ri miring the development of pci..-;*/, .- f!!,rcm as displayed in n series of j-:`Iir;rrnrn, and especially in the few a vpihble taken a year or more before a fatal fcniunation, 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. Tims, at any rate in the less advanced stage?, 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 radiologically, of tip* as! ms! os fibrosis is its uniformity. The modest}* of the symptoms; the unobtrusive, but diffuse, impairment of the percussion note; the homo geneous stippling of the skiagram; ail arc fragments of an entity, unmi.stnknblo when assembled, but enigmatic when divorced. Only two rcfcrcuccs to the radio graphic appearances of the chest in asbestos workers have been traced: one in a report by Fancoast and Pendergrass (10), and the other in an article by Burtou Wood (19). l'ancoast and Pendergrass together with Miller and Landis examined "17 asbestos workers, 2 of whom showed j. i. n. II.y, 1930 i i i| i i i * tt i / i i \ \ / i I \ 1 first stage 15 defioitc Of the met ecventcen very defir throughout showed nb after fou Very slid found in o: occup.'.tion stage case first stage indicating hilumwart lar shade `soft' and Their first with stag with stag' It appi these obsr as being r ture of f original r stantiate. BurtoD teen ski: notes: skiagram to ashes shadows affecting of the lu shadows the case appearar fine mot more de lacks th the skia ruoconu miners. Clear fibrosis Yul. K No.S PULMONARY FIBROSIS IS V.-MUKLRS 210 fir.-t stage change? and the other and by fh'- fii* ii rvnvlird 15 definite second singe appearances. wh-n th* fdiscussed above arc, Of the men longest at work, one after in varying d'!'r<<\ positive, and the seventeen years' occupation siiowcd radiologic pirttir* ia recognizable, the very definite diffuse, 'soft' spots fibrosis is not in its inception, nor even throughout both lungs, and another in its r.nrlio-t. stages, hut is developed showed about the same appearance end fairly widespread. nftcr fourteen yews' occupation. We must, therefore, recognize an Very slight nodular shadows were earlier Mate when the fibrosis is present found in one man after only two yews' in slight degree, and also when there is occupation. Most of these second evidence of choking of the lymphatics, stage eases showed also well-marked and of a measure of pulmonary catarrh. first stage appearances still present, This stage may be. referred to conven indicating a persistence of free drainage iently as the prefibrotic stage. hilumward. In all instances the nodu The indications of this stage are lar shadows were characteristically indefinite, and some, at any rate, not 'soft' and varied considerably in size." specific. If, however, they can be Their first stage appears to correspond determined end applied with only a with stage 1, and their second stage moderate degree of accuracy, informa with stages 2 and 3 mentioned above. tion of practical value will be available. It appears from the context that Efforts have been made, therefore, to these observers regard asbestos fibrosis distinguish workers in this stage. as being really a silicosis due to admix The following tabulation shows that ture of free silica derived from the twenty-one workers out of 303 exam original rock--a view difficult to sub ined (5.8 per cent.) were so classified: stantiate. Burton Wood (19) in a scries of fif teen skiagrams 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 & 'ground glass' Clinical Kri'ninalient (SM): JV. Fibrosis................................ 95 rrefibrotie conditions....... 2t Iii\'li"l"aie r.amnationt (m).: Fibrosis................................ 52 Susceptive chances not definitely difTusc fi brosis............................... 22 Per Cent. 28.2 5.8 39.1 1G.5 Many of these eases present a slight appearance, though on close inspection diffuse impairment of percussion note fine mottling is evident. . . . when --perhaps better described os & slightly more definite mottling is present it increased sense of resistance felt on lacks the coarse quality described in percussion, mostly of the right lung, the skiagrams of chests showing pneu at least as contrasted with the left, moconiosis, e.g. South African gold and associated with some weakening miners. . " of the respiratory murmur. Prob Clearly, the maturation of asbestos ably this early stage could be detected fibrosis is spread over a period of years, radiographically, but only by means of VoLll Ho. i 21G . THE JOURNAL OF INDUSTRIAL HYGIENE comparison with a radiogram liken prior to commencing work with asbes tos. By such means the earliest r.tagns of silicosis have been worked out by the Booth African observer1:. 'J he/e, Ive tui.like:, it croup is dismissed from- ny further consideration. 1 A funeral summary of the findings in the .`574 workers who were examined clir.ivi!!v. th*iTjOct 112- tall always be corn par etf with jnitid radiogram* taken before the employees arc permitted to work underground. fl.i.tivirvirtr. (.'A=-.rs The salient points of a f - ases are set out below to illustrate v'-mical and TAULE 4.--GENERAL SUMMARY OF FINDINGS CLASSIFIED UNDER THE MOST IMPORTANT LESION | Due to Other Causes 1 Other A ctive Lesions CASES FRE- OF FlftROTIC CONDI* FIBROSIS TICKS FUT.MOKAftr TtnfRCU* LOStS 1eu 2_ 2SH aOu 0*3 <2 2H 1e OTSER FULUOVART LESIONS aa B aS ft* M% w V) c H m o o m z 5 %> JvS> << y. O ao 6 SJ zQ VI VI VM 3 S c wo *O>i a V o o.2 h* s o 5 VI < o '>& -O o 3 o a VI e> j3 3 3 :-Q Qa JS > V e uc z.2 o bZ Z *S8 jZ oo ts _ =o o2 3%l ss; a. * 2 oS n tr. e U o < (h tf. U J o 'J 5u 2 71 5o os Sg jf a TI 9 Cl 6. VI *d C to s4>I `S a J3a uo 6 WO A H S 3 *9 < s oa z z e H ec 0-1......................... 92 0 3 5 0 0 0 0 5-9.................. 142 30 1 12 0 1 1 4 10-14....................... 89 27 5 3 0 3 0 3 15-19....................... 30 15 1 1 1 0 0 1 20 and over.... 21 17 0 a 0 1 0 0 13 3 5 0 0 7 i 0 i 62 3 5 2 2 72 0 3 2 0 3S 2 1 10 7 1 010 1 Total............. 374 as 10 21 1 5 1 8 2f i:i in 0 3 ISO I'erccnUgo... 100 25.4 2.7 5.0 0.3 1.3 0.3 2.1 5.0 3.5 2.7 l.G 0.K 48.1 1 One cue of thickened pleura due to old gunshot wound. * Ona euo of emphysema due to gassiiiR. In other cases included in this group, diffuse weakening of tike respiratory mumnar was noted, with fine sticky riilcs in the root areas. At present no stress can be laid upon this group. The clinical changes arc so slightly marked that until comparative radio grams 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. Cask 1.--This worker, a female, aged 21, Ins l'.s'n employed in asbestos for ten and onc-tnlt yenrs--ns a card tenter one year, J. I II. lUy. tv:o \ and on a dou Her family o contain nnti.i plainls and fr Pin' C'-r--il. .. N; : ift the h*f* ri^ht mot,, * Sfitacran sLt doubtful ch3 crcai^J striat Case 2.-- employed in ami mixinc* years in the His family contain nutl slight morn for a year, color is fres Cfccst.--T percussion n ripht luns, t Imsc. The expiration i the richt l' prnlnn'*rt! u Tim rrsptra right tasr, `wliifliusc** sounds. A of Ha* fish si rialiult in mium-jdimS (.'ask II cmpluyrtf i ntnl mum, I'rrviously mom fur ui for live yon h family lit is nothin? mt'dical hi fi-rU ipiit (jtitnl. 11 rynm* ;ts. * rficaf.- |HTCUS.-iu the ri?ht a little Miuutls v..t, \: Na. \ X Auc/ier ridings in xanjincd most iniTable tj. f 4I j (! { '* iscs are 'ical and t the is aro ologic cases. J1 tics, finer ncga- :cd2<, u and i-cir, J I. IT. r, me j ' j. ') I 4 r, r PULMONARY FIIiKO.'IS .-V-T T.:-'! (tS IVOIIKlOiS 217 ,i a iWi * nine and oue-haU yiv. old In11 iriil" i of I hr bine roofs nod gen II,-r family *. i persona/ mrdiral liixf.-rr eral inrr'a 'rd striation, psprcmfly in llitt contain nothing of note. She haa no r"m- lonof I, - If of tltr rich! long, suggesting rnrly plaint* and fccli quite weli. Her nutrition niw-'Y j pnml. She is pair, bu t shows no eyatiori*. !. - This worker, a male, aged 23, (hrit.--She has a cheat expansion of 11 ho* l,"<-n employed in nxbcstns for nine inrlirj. No impairment of the |iretid>n vr-ts, mostly mattress making. His family roitr is detected. The brcatli sounds in the and j <Tenml medical history contain noth right lung are weaker, generally, than tho ing of note. JIc complains of occasional rn the left "ipiratinn is prolonged at the pain in both sides of the chest, and perhaps right root;, added sounds are hoard. A a litl!" undue shortness of breath on cxcr- skiagram <(>. id some very slight and doubtful changes in the direction of in creased *trial ion. R | Case 2.--This man, aged 24, has Wo employed in sslmstns tor five years, carding sad mixing. Previously he worked for four vrars in the cotton trade, yarn weighing. Ilis family and personal medical history contain nothing of note. He has had a slight morning cough and expectoration for a year. His nutrition is good. Ilis color is fresh, and there is no cyanosis. Chest.--There is some impairment of the pcrcussinn note over the middle third of the right lung, behind, and slightly at the right base. The breath sounds are harsh, anti expiration is prolonged in the upper half of the right lung, behind; expiration is also prolonged over the loft upper lobe, behind. The respiratory murmur is weakened nt the right base, and the breath sounds are of a i \ "whiffing" character. There are no added _1 sounds. A skiagram showed enlargement of the right root, snd slight hnriness and striation in the central tones in lioth lungs, suggesting early fibrosis. Case 3.--This man, aged 32, has been employed in asbestos for six years in the card room, and ns a stri|>|>cr and grinder. Fto. 1.--Case 4: Moderate fibrosis. Un due degree of striation anti fine mottling in rentral rones of both lungs; calcified glands in roots, with rather coarse striation in upper lobes; ? interlobar pleurisy on right side, between the lower and middle lobes; emphysema at bases. Previously lie was employed in a cotton parti room for nine years, lie bail nrmy service lion. Ilis color is normal. Ilia muscula for fire yearn, but was not gassed, lie gives ture and nutrition arc good. a family history of asthma; otherwise there I'kr.st.--There is no retraction of the is nothing of note in his family or personal apexes. but there is a slight flattening lielow medical history. He has no complaints and the right elavicle. The |>ercussinn note is feels quite well. His musculature is very good. His color is pale, but he shows no cyanosis. Chest.--There is slight impairment of the percussion note generally, particularly at the right base. The respiratory murmur is a little weakened generally. No added sounds are detected. A skiagram showed slightly impaired generally, behind, partic ularly on the right side. The breath sounds are weak, generally, and expiration is pro longed. No added sounds arc detected. The skiagram (Fig. 1) shows an undue degree of striation and fine mottling in the central mmi of both lungs; calcified glands in the roots, with rather coarse striation in VoLU Mot 218 THE JOURNAL OF JNJfUSTRIAL HYGIENE the upper lobes; 7 interlobar pleurisy on the right side, between the lower end middle lobes; and emphysema at the her"*. The case was diagnosed as moderate fibrosi*. Case 5.--This woman, nged 40, has been employed for eleven years in asbestos, for most of the period mattress making. Pre viously 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 loo.ierato fibrosis, most marked toward the he-'-s. (<<e 0.--This worker, a female, aged 31, "has tien employed in asbestos for seven yrnrs, opening, and has been exposed to much dust. Her previous employment was nnn-diisty. Her family and personal history disclose nothing of note. She com plains of having had a cough for five years, and of shortness of breath on hurrying. Fhc is thin and undernourished, and pale. I. Fio. 2.--Case 6: Moderate, but fully developed, fibrosis. Enlarged glands in both roots; diffuse fine mottling in both lungs, especially the right. Ftc. 3.--Case _7: Genera] fibrosis, mostly linear, but with little mottling of right lung. Old puerile tuberculous sears at apexes. arc negative. She cmnplaimi of having had a winter cough for throe or four yenrs, mid of shortness of hrenth on overtion since her attack of pleurisy. Her nutrition is good; her weight i* stationary. She lias normal color, ami mi cyanosis. Chest.--There is some general impairment of the percussion note over both lungs, lcliind, more noticeable at the liases. The respiratory murmur is wakened generally. 1'crsistcnt crepitations and medium rales arc noted low down in the right axilla. A skiagram showed diffuse fine si nation and fine nodular mottling, with light opacity at the bases. 'The case was diagnosed as Oust is present on her hair ami in her nostrils. f.Virst.-- She has a chest expansion of onefourth inch. There is sligtil general impair ment of the |MTcussiun note, definite at lh n|>exc* nml the liases. The hrenth sounds are weak; expiration is slightly prolonged. No added sounds arc heard. Her heart is not enlarged, ami no murmurs are detected. The skiagram (Fig. 3) shows a numls-r of enlarged glands in both roots, and n difluso fine mottling in both lungs, rsfiecially the right. This is a rase of moderate, Imt fully developed, fibrosis. Cask 7.--This woman, aged 4S, has been J. I. it. May, WO .-it IIIC I 31, scvrn srd to rmrnt . -rsmtal r coiuyears, rryinR. I pule. nn.stly : lung. in her -f one. npnir. at. tlm ."iiihU nged. art. in I'ftcil. ix-r of litTu.-tn Iv the t fully' i been I. n. two ) PULMONARY F1HHOK1S IN ASIILSTOS WOIIKLHS 210 employed in asliestol for thirty-tivo years -- almut three year* on cards, amI the re mainder as a spinner. She bn* done no other fartory work. Tier family meiftral history discloses nothing of note. She has a |iersonat history of nephritis seven or eight years ago, causing three months' illness. Her complaint* nrr: shortness of hrcatlt on hilts, ami winter cough for nhout nix year*. Ilrr nutrition is fair. She is rather pnlc. Chr.it.--She has a ehr*l expansion lit onehalf inch. No retraetion of tho apexes i* noted. There is general (light impnimirt.t of the percussion note, lieliind. Hrcath sounds are harsh and expiration is pro longed. No added sounds are heard. No gross enlargement of the heart is noted, hut the second sound is found to lie 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 arc also very old puerile tuberculous scars at the apexes. The case was diag nosed as general fibrosis. This case should be compared with Case . 6. In Case 6 there was a heavy exposure to dust extending over a few years; in the pres ent case there was exposure to a very much less concentration of dust, except possibly in the first three years, but extending over many years. Case 8.--This worker, a male, aged r-2, has been employed in asbestos for twenty years as a weaver. He was previously a cotton and silk weaver. His family nrd personal medical history show nothing of note, except that he was regarded as a deli cate child. His complaints are: shortness of breath on exertion, and on going upstairs, for three years; morning cough and a little expectoration for the last three winters. He is thin and pale, witli aomn cyanosis. Chnt.--Cheat expansion in 1 ineli; there in retraetion of Ilia n|N'Xea. The |a-reussion mile in impaired over luilli np|s-r Inhrs, in front, and over the up|mr two-thirds of the right lung. In-hind, Inspiration is pro longed at the bases, l'leural roll and incon stant idle* am noted at tho left base, and a few rales at the right base. A skiagram I a definite diffuse fibrosis with noduIstion. This is a ease of fibrosis in the early advanced stage. Case 9.--This man, aged 41, has been employed for tiverity years in ,v.Ix sins in many rapacities. There is nothing of note in his family history. He gives a history of pneumonia a mimlier of years ago. His complaint* arc: a little shortness of breath on exertion for the last two or three years; otherivie none. His nutrition is fair only. His color is fresh, but there is slight cyano sis of the lips, at times. Chr.il.--The skin is poorly elastic; there is some retraetion of the a|ioxrs. There is an impaired, rather "iM/xy," note on percus sion, generally, e*i>eeially over the up|ier half of the left lung, and over the upi>cr twothirds of tho right lung, behind, and in front. ltepiratory murmur is generally weak. F.xpiratinn is slightly prolonged, but diminishing toward the bases. Pleural crepitation* are noted low down in the right axilla. A skiagram showed a definite fine diffuse fibrosis. Neither lung lights up very well, nnd throughout both there is a very fine diffuse reticulation and mottling-- moderate, but fully developed, fibrosis. The fine diffuse character of the radiologic appearances i particularly noticeable here. Cast. Iff.--This man, aged 4G, has been employed for twenty-five years in asbestos, during nin* years of which he was not ex posed to du*t. For eleven years of the r'-emimbr b- was employed in the card rnmn, and mattress making. Ilis family nnd personal medical history disclose noth ing of note. His complaints are: shortness of breath on exertion for three months; cough 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 thn chest for the last three months. His nutrition i* good. He is pale/ with slight duskiness of the lips. Chnt.--There is some retraction of the apexes. The |N-rrus.xion note generally is impaired, and of a 'Mmixv** rharneter, llrenlh found* are Iinmil mid i-xpiriition in prolonged over the right up|sw Inlie; else where the respiratory murmur is a littln weakened and expiration is nnt materially prolonged. No added sounds arc heard. The heart is normal. Tho skiagram (Fig. 4) shows diffuse striation and fine speckled mottling throughout both lungs--fibrosis, ful'.y developed. Case 11.--Thu worker, a male, aged 40, VsL 11 N.s