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! PLAINTIFF'S | EXHIBIT I THE JOURNAL OF INDUSTRIAL HYGIENE --------- EDITORS DAVID L EDSALL M. D- S. D, United Sute. EDGAR L COLLIS, M. D. M. R. C. S,, Great Britain ....... VOLUME xn JANUARY. 1930--DECEMBER. 1930 . PUBLISHED BY -HARVARD SCHOOL OF PUBLIC HEALTH _____ -- - Bcetcn,Mui. - - --- -- i. t & fit THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS* -- - - E. R. A. Merfwstbeb, M.D-------- ------- --------------- B. M. Medical Inepector of Paetoriu __ ___________ Introduction ------------------ ---fie was treated is the Charing Croee Boa* pital for two months, and then returned to RIOR to the commencement of work. After a few months, however, he Pthis inquiry, in February, 1928, beeasxe ill again, and was readmitted to the definite knowledge existed of Hospital in April, 2900, where he died. Tfie only two deaths of asbestos workpeorsst-mortem examination confirmed the .About whom there was expert opinion clinical diagnosis of extensive pulmonary fiHroei* There v-is no evidtu^t yi 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 most suggestive, only came to light some years after the occurrence, when full information was unobtainable. All that is known of this ease, 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 1006 (1). Tioiu ihis source, we 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 eardroom when he went into it, he waa the only stirvivo^ <! that all the others had died somewhere about 30 yean of age. There is no note as to the nature of his work, previous to that is the asbestos factory. Received for publication Feb. 47, 1930. The second case was reported by Dr. W. E. Cooke in 1924, eighteen years later (2):, - . : - ~ -- The deceased, a woman, aged 83, who died in 1934, had worked in asbestos for 18 years, but intermittently for the last 5 yean, owing to periods of ill-health. The post-mortem examination revealed, not only extensive fibrosis of the lungs, but also much change due to pulmonary tuberculosis. 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 and fibrosis of the lungs would have been strengthened by the absence of a tuberrnlous Cooke's case is, however, of out standing importance, not only because of the discovery of "curious bodies" in the lunge--discussed later--but also, and of more importance generally, be- ------------------------------ 198 J.LS. Hat, I0 lND OTHER : RKERS* - ____________ Sharing Croat Boa____________ d then returned to --~ oths, however, "he ` ` " T readmitted to the here he died. The " n confirmed the -- ____ L. enaive pulmonary - iueuce oi puuno* _______- xamination of the -------------- -- a woe negative._____________ reported by Dr. eighteen years j f aged S3, who aabeetoa for IS for the last 5 f ill-health. The i revealed, not he lungs, but also iary tuberculosis. 0 and Stuart clusively of the - --TM :ase the lungs ust fibrosis, to- ' tuberculous in- elationship be- asbestos dust i es would have le absence of a .j rever, of out- t only because irious bodies" iter--but also, generally, be- T J. I. E. lUy. I0 PULMONARY FIBROSIS IN ASBESTOS WORKERS 199 cause its publication again directed This case, at that time the third of attention to the possibility that inor which the Factory Department had ganic dusts containing little or no free knowledge, was, however, the first in silica may be productive of extensive which the four essential conditions, pulmonary fibrosis. Of these dusts, necessary to establish a relationship the silicates form a very large class, between the inhalation 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 are:_ _ _________ _______ _ _ -chalk, and pumioe, are used in industry. The extensively importance,^ . 1. dust. Work involving exposure to asbestos therefore, of delimiting the potentiali 2. The existence, demonstrable 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 radiologically, of a definite pulmonary fibrosis. 8. The absence of previous or present infeetiorr Wiovn to **?? p"1--------e.g.t tuberculosis, influenza, or pneu monia. Murray case, although contained in the evidence presented before the Departmental Committee in 1906, and 4. The absence of previous or present work involving exposure to other dusts, which might cause 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. I. 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 ease in an asbestos worker was an access to his records. exceptional occurrence, or evidence of In February, 1928, Dr. MacGregor, a 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 prime 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 logically, signs of a diffuse pulmonary invited further investigation through ixuruam, witu no eviueuue oi a tubercu out the industry, witu the result iun\ 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 other than the Inhalation of asbestos the examination, both clinical and ra dust, was found to account for the diologic, of workers, was undertaken existence of the fibrosis.' during the year 192$, commencing Vol. 13 * '~ ----------- ---------------------------------- *:.-T V ^tr'. 200 THE JOURNAL OF INDUSTRIAL HYGIENE with the carding, spinning, and weav and any methods of ventilation which ing processes of the industry. had been found of especial value. - - In the meantime, in March, 1928, The result of this investigation did the death of an asbestos worker (one of not conclusively prove that asbestos Dr. Grieve's cases) occurred in another possessed injurious properties, but it part of the country, and, on poet- pointed to the probability that such (mortem examination, a condition of was the case. It is interesting to con ''widespread fibrosis of the lungs, with sider why it was that no conclusive out tuberculosis, vas revealed. The proof one way or the other could be - microscopic examination also disclosed `obtained, then, as to the injuriousness ' the presenoe of the curious bodies. of asbestos dust. Some, if not all, of "In 1928, also, Dr. F. W. Simeon (6) the factors which affecte^the position reported a fatal case of fibrosis of then are, in varying degree, continu the lungs occurring in a native work ing factors, and have an important ing in an asbestos mill in southern bearing on the present inquiry. Their Rhodesia. operation, while providing a solution In order that this brief survey of the to this query, also affords an explana events leading upto the present in tion to another pertinent question: quiry may be complete, it is necessary Why is it that this industry, founded to review the investigation made in in antiquity, has only recently exdted 1910 to 1921 by Dr. Collis and Miss attention, by reason of itsraw material Whitlock--the only previous inquiry becoming suspected as a cause of indus into the subject. trial disease? In May, 1910, the Registrar-Gen The answer appears to be that in the eral drew attention to a death which past it was not practicably possible to had been certified as "acute pulmonary obtain proof of the injuriousness of phthisis in an asbestos worker," and asbestos dust, considering the limita to a statement (for which be was un tions imposed by the state of the indus able to vouch) that seven other deaths try, cuiu the point reached by research from phthisis had occurred in the same work into the relationship between factory. dust inhalation and diseases of the Following this, extensive inquiries lungs. were made, a medical report on all the The industry itself, not a large employees in the factory concerned one today, was then (1910) consider-^ was obtained, and Dr. Collis and Miss - ably smaller. Certainly it had begun Whitlock~ investigated generally the to grow rapidly, but the number of various processes in the industry with workers who oould have been employed' -- respect to the evolution of dust, for a period of time long enough to methods of ventilation, lost time due to allow of fbp development wi ueiinite sickness, etc. Aiso inquiries were physical signs of pneumonokoniosis made of the Canadian government as must have been quite small, and dis-_ to the conditions in the asbestos persed over the country. ----- quarries and mills in that Dominion, Precise knowledge of the morbid.' ----- evidence of increased sickness and -affections of the lungs produced by the :J^"~xnortality rates among the ^workers, inhalation of dusts was more fragmen- PULMONARY FIBROSIS IN ASBESTOS WORKERS 201 ventilation which , pecial value. 2 investigation did ^ >ve that asbestos .____ properties, but it ------ r- ability that such ` y* ateresting to oon------:--------- -- at no. conclusive ~ .: "rrf e other could be the injuriousness ^ me, if not all, of _______ cted the position -. _ degree, continu- ... -- e an important : inquiry. Their 1 iding a solution ------- - >rd6 an explana- f ment question: - - --"r'f": dustry, founded recently excited j its raw material i cause of indue- ,, tary 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 knowwhether 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 mayoccur." It is only in the last year or two that research has produced some definite evidence as to the precise effects of spme of these dusts on the togs (8) (6) (10) (11) (12). ! - 2020, radwg:*pny oi wneiuugs, in both its technical and 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 o be that in the bly posable to iriousness of mg the limitste of the indueed by research *ship between iseases of the ..; - -=>- - 2 - - -* ------ ; ' "" 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 ijuin the inhalation oi the dust. This influence has been not a large : 310) consider it bad begun le number of een employed og enough to at of definite " raonokoniosis - .1' iw.u J:. 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 U6e of the phthisis mortality rate /wmrv* >-- of the degree of injuriousness of the the morbid duced by the " ore fragmen-i.: dust encountered in the various dusty . occupations. This rate, while of great value in separating dusty industries ---------- - into -two great groups--those which Bhow 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 a means of classification in the latter group, but also tends to distract attention from it, _ and to result in the associated du6ts be 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 rate in 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 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 singular 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 ir its stealthily advances with but faint warnings of its progress; inexorably it cripples the essential tissues of the togs, 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, L-i lo aic of hie undue shortness oi 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 acut-e illness has caused a fatal termination, ita. Ktf.WO Vd. U KaJ 202 THE JOURNAL OF INDUSTRIAL HYGIENE a stage is reached when the lungs can do iiiue more than maintain life; and the shortness of breath is extreme. asbestos dust has a totally different physicochemical constitution from that 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, _ While more or/less acute cases of so as 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 oountry (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 tcly, ihv ralLcr than the rule. -- The difficulty of diagnosing pulmo ' Asbestos and the Asbestos Industry 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 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 -=7= 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 sput up iuu> iuug ana 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; on 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 thelungs, it was not possible -to obtain evidence sufficient to prove or disprove this hypothesis. At rtf IVa nmaenf qualities in differing degree. Com mercially, therefore, selection is made by the manufacturer of that variety whirh w>o*t suitable for . into what, if any, pulmonary diseases workers exposed to the inhalation of asbestos dust are more prone to con the purpose in view, regard being paid to ordinary economic factors, such as the cost of the raw material, and the-- - tract than the general population, it was considered essential to view the problem afresh, and with complete detachment, because of the fact that price which the finished article may be__ expected to command. ' ----------- Consignments of asbestos of the -- same general variety, but with differ- '' l i t : I s -i x 4 f PULMONARY FIBROSIS IN ASBESTOS WORKERS 203 itally different ufcioofrom that u free tilica and was felt that ible guidance i the methods ous dusts, care an open mind, 'Ciously biased lining that thej , must be com e to those of -- r 1 i .. r\ Asbestos____ ent countries of origin, are frequently bined water, and usually more cal mixed in the preliminary processes of cium, aluminium, andiron. Members manufacture. Thus Canadian chryso of this group are resistant to acids, tile may be mixed with Russian, or but are more difficult to spin, some Rhodesian chrysotile, and so on. Lees being quite unsuitable for this purpose. frequently, totally different varieties, The most important members of this such as amosite and chrysotile, may be group are crocidolite, amosite, and mixed. tremolite. " Practically speaking, all that goes __Crocidolite and amosite are mainly under' the same of asbestos, in oom* silicates of iron, the former having a meroe, is either fibrous serpentine or a beautiful lavender-blue color, thelatter 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 making into insulating s a collective ineralogic siga Applied to a Is, which differ stoical compo^~ roperties, but her in their _d flexibility >ends on the are capable of g and flexible all AomA*C C4S,UASU <a their resist* and on their th respect to possess these ; iegree. -Com*--.-- ction is made -: ` that variety__________ t suitable for -* ctors, such as------- erial, and the article may be ~ estoe -of the ~ ..irjrsi it with differ-. - ' TABLE 1.--COMPOSITION OP SERPENTINE AND AMPHIBOLE VARIETIES ----------- ------- -------------- -OP ASBESTOS KXMSAAL __ 0*00* . TAStmrr SiOi naesNTeox or AliOi FeO Fe*0, Com MgO CeO Ne0 KrO bined Water Serpentine Amphibole (bornblende) Chiyeotiie Crocidolite Amoeite Tremolite 8042.5 0-3.7 0.7-4.4 30-43 0-0.35 50.5-52.1 0-1 35.5-37.4 0-3 0.75 Id.2-0 ... 43-53 1.2-0.4 34-44 0.7-6.4 .... 0-2.5 57.2 0.0 3.2 22.8 13 4 0.5 0 3 13.3-16.5 1.54.5 2-3.8 2.4 term asbestos to norous forms of hornblende. These two types are sharply distinguishable, chemically and mineralogically. Serpentine asbestos, or chrysotile, is a hydrated magnesium silicate, con---------------taming practically no calcium, a high percentage of combined water, and a . _ low percentage of iron. This variety is very suitable for spinning, but is Nearly SO 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, van_______ etiesoontain leas magnesium and com- mattresses, as well as for other purposes. Both are produced extensively in South Africa, from which quarter all required commercially is obtained. Amosite, a comparatively recent discovery, is found there in very large deposits; its use is steadily increasing, the initial difficulties associated with the manufacture of textiles from this variety having been overcome. Ticmuliie, found in various quarters of the world, has been mined in northera 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 204 THE JOURNAL OF INDUSTRIAL HYGIENE sources, shows the main differences in reexported. Thus the consumption of the composition ol these four varieties. asbestos in this country trebled within Only a very small proportion of the five years. world's production of asbestos, which 16 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 '.T.'a"high price--now -over 100 a ton. The shortage of this grade has Jed to improvements in manufacturing proc esses which have enabled less expen sive grades of fiber to be utilized for spinning, some of which give rise to an i liu ./. j--.,U_-+u- , 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 The Industry On considering the uses of asbestos one is astonished, not only at the wide range of articles manufactured from this mineral, in greater or less propor tion, but also at the diversity of indus- 7 tries which nowadays find its use necessary, either in the form of the raw material, or as manufactured articles. Evidently, therefore, with the multi plicity of processes and dusts encoun tered in the ramifications ot tne 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 ... 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 spinning and textile section has also 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 ma shared, because of the extensive use of tne yaru uuu motu tii tuc manufacture of steam packings, insulating mat terials. 3 Pro<*es6es involving th making up of asbestos cloth into other articles. tresses, brake linings for motor cars, fireproof curtains, and the like. In 18S0, three years after the dis Group 1 entails exposure to asbestos dust mainly, and to cotton, or other vegetable dust, very slightly; group covery of the Urge Canadian deposits, 2 entails exposure to asbestos dust in the world production of asbestos was very varying amounts, and also expos little over 500 short tons; by 1900 it ure to divers other dusts, such as brick had risen to about 35,000 short tons, dust, magnesia, kieselguhr, fossil meal, by 1920 to over 230,000 short tons, and and cement; in group 3 the exposure to i*-r by 1925 to nrer 330 000 short tons (15). asbestos dust--provided no other as The imports of asbestos (all grades) bestos processes are being earned on into the United Kingdom rose from in the vicinity--is, in the majority of 18,591 tons in 1922 to 33,520 tons in cases, negligible. Processes belonging - 1927 (16). The figures for 1927 refer to all three groups may be carried on in _ to Great Britain and northern Ireland the same factory, and workers may - only. -Of these quantities 8,844 tons transfer from one department to and 3,794 tons, respectively, were another (30). MB. PULMONARY FIBROSIS IN ASBESTOS WORKERS 205 consumption of " trebled within ' $j Z? \ ? 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 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 m, _ ____ in the absence of knowledge of the and other purposes. The interstices ses of asbestos nly at the wide lfactured .from effects of the several component dusts, and center of the rope may be filled ~ and moreover would introduce an in with other materials such as talc, oil, -------------- calculable .variable. into ..the ..final _ .or .graphite, depending on the precise_____ or less propor- --------- results. For these reasons, and also use to which the rope is to be put. - ------ ersity of indus because the Montague Murray case, Asbestos mattresses, used for blan ; find its use Cooke's, Grieve's, and Seiler's cases keting steam engines, and for other form of the raw all occurred in processes included in insulating purposes, are made of asbes rtured articles. - group 1, it was considered advisable tos cloth stuffed with asbestos fiber. _ with the multi* to exclude, as far as possible, from the The stuffing material may be, however, dusts encoun- . inquiry all workers exposed to the in slag wool, magnesia (containing ap a of the indus- _ fluence of mixed dusts, and all those proximately 15 per cent, of asbestos ild have to be not employed in processes included in fiber), or kieselguhr with a small per- mit set to the groups 1 and 3. oentage of asbestos fiber. The man e inquirycted may -be^= The processes included, therefore, ufacture of mattresses filled with ----- -------are the crushing, preparing, sieving, mixtures of asbestos fiber and other . _ opening, mixing, carding, spinning, materials has not been included in this manipulation -- - admired with a h or other rege- --------- -- doubling, plaiting, braiding, and weav ing of asbestos, together with the operations incidental thereto. Also portion of the inquiry. The shortness, slipperiness, and lack of strength of the individual asbestos .be manipulation other du*ty me- included is mattress making, where the fiber, as compared with cotton, flax, filling is asbestos, and the manufacture wool, silk, and other textile fibers, have of ome insulating materials, where the been the cause of much technical diffi ie making up of rtiele*. dust produced is asbestos. culty in manufacture. The efforts of The carding and spinning processes manufacturers to cope with these diffi :ure to asbestos jtton, or other slightly; group sbestoe dust in and also exposs, such as brick uhr, fossil meal, V omosure to d no other as- ' ?ing carried on .he majority of esses belonging ... be carried on in -- 1 workers may -- (apartment to 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, are reflected in the _____ modifications and restrictions caused methods employed by each. Forthese_____ 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 jt i or other vegetable fiber, and usually differences in detail in the processes in from 2 to AU per cent, py weignt oi use. cotton is added, More rarely, and for The majority of the processes men special purposes, long-fibered asbestos tioned result in the evolution of dust, is carded and spun with no admixture although by no means to the same _ of vegetable fiber, but usually asbestos extent. Differences in plant, quality yams contain a core of either cotton of asbestos used, methods of manufac or metal wire. ture, type of finished article, and extent ' . ______ Asbestos yams are not only used for of application of exhaust ventilation, a&*3? ` il*4**+= ~ ~ irrri 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 tbe Owen6 jet apparatus. Population at Risk.--A calculation of tbe total number of workers employed in tbe processes already enumerated-as TABLE 2.--DISTRIBUTION, ACCORD1NG TO LENGTH OP EMPLOYMENT, - OF (A) 776 WORKERS ENGAGED TV iOQpcTnc pprw^pccrre a vp (B) SELECTED SAMPLE OF 863 WORKERS (A) (B) TES. XKPLOTZD ca iett i i 8 c 0-4.............................. 4S3 62.3 89 24.5 5-e............................. 200 '25.8 141 38.8 10-14............................ SI 6.6 84 23.2 15-19............................ 24 3.1 28 7.7 20 and over................. 17 2.2 21 5.8 Total........................ 775jl00.0 S63|l00.0 included in this inquiry, but excluding those engaged in processes included in group 3 in which tbe exposure to as bestos dust is negligible, gives a figure of approximately 1,600; if we could add to this tbe number of workers engaged in handling pure asbestos fiber in - processes included in group 2, we should obtain the total population at risk from the effects of asbestos dust it-self. Unfortunately, this latter figure is unobtainable; but a rough estimate, and most probably an overestimate, is 600. Thus, about 2,200 appears to be the total population at risk in this country, for tbe purposes of this in- . quiry. This figure, however, does not include tbe large number of workers . engaged in tbe processes in group 2 which involved exposure to tbe 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 ~ tne 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- fibrotic conditions due to causes other__ than the inhalation of asbestos dust) numbered 363, representing 16.5 per cent, of the population at risk, esti mated 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 those 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 tbe particular process in which the worker was ?/ __t..U ------ ik n ia9 iuiv ttiAk, ui viue n , tbe maximum information would be obtained in the shortest time, Table 2 shows the distribution, according to length of employment (not necessarily in one factory), of UE. x*r, mo * * r... * jrestim&te, appears to risk in this of this in* r, does not - of workers n group 2 > the influ sh asbestos - not more ; ;ure. - pulation at xcessive, is to judge of - rtf workers re correctly .. pulmonary rumination iter eleven $is and pre* auses other ^toe dust) , 16.5 per ; risk, estimanner of : be referred :cs cf thA ,e appreciaie sample to 4 ____ -I .g primarily as adopted; o the other _ btain inforexposure to ts are mani3 particular worker was in this way, .. a would be ae. listribution, -- employment _ factory), of J.LB. MM PULMONARY FIBROSIS IN ASBESTOS WORKERS 207 775 workers engaged in the processes under review, and of the sample of 363 workers, distributed in the same way. . The enormous preponderance numeri-tally 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 = -4he chest in investigations into the effects of dust upon the lungs, has been emphasised repeatedly by WatkinsPitchford, and reaffirmed by the Departmental Committee on Compen sation for Silicosis (17). A high standard of radiography is essential; as Watkina-Pitchford 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 U> be Uuteu 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, ae 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 clinical 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 tire necessary appointments. On occasions the noise of traffic or from the adjoining factory was a hindrance, but in one way or tt&OkhcT kUCOC dluiCUiMwh Wwv CVC*' come or minimised. 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. Middle ton. His far-reaching experience of the Vd.U 208 THE JOURNAL OF INDUSTRIAL HYGIENE pathologic changes in the lungs, pro duced by the inhalation of various dusts, was of great value, and his assistance was much appreciated. Every effort was made to complete the clinical examination of the workers before the onset of winter introduced difficulties due to ephemeral bronchitis, colds, and influenza, which would tend --to obscure the main issues. Thus the clinical, and two-thirds of the radio graphic examinations were completed bytbemiddleofNovember, 1928,prior to the commencement of the influenza epidemic early in 1929. Clinical Examination - - Percussion ' The inhalation of asbestos dust originates changes in the lungs, which may be looked upon as a measure of the efforts of the living tissues to repel, or incarcerate, the irritant particles of dust. These changes modify the per cussion note. It is true that the note elicited may be similar on both sides, but the note is not normal. It is thinner and higher pitched thaui nor mal, and there is a sense of resistance imparted to the plexor Anger. In other words there is a diffuse, but slight, impairment of resonance. This alteration in the percussion note, however, is more difficult to recognize because it is bilateral, and extends over a wide area; consequently the aid of contrast percussion is denied. It is best elicited by ranirilv. and very lightly, percussing the back of the chest from apex to base on each side. It will be found that the extreme apexes remain clear, but below the _ apexes the impairment is general. It increases over the root areas; below these, it diminishes in intensity, but still persists. In other word* we And tacked on to the paravertebral dulnees an area, above and below, of impaired resonance, which is much more exten sive than that usually associated with old inactive hilar tuberculosis. Impairment of the percussion note was found to be constantly more marked in the right side; in fact, at first it was thought that in the earliest degrees of fibrosis it was confined to that side, but later, and more extended observations lead to the conclusion that the earliest detectable cases at* buaterai, although the signs on th^left side are tenuous. This change is so constant that it has been adopted as the most reliable single clinical sign presented by this type of pulmonary fibrosis, and -no case has been classified as fibrotic in its ab sence. Considering the frequency with which signs indicating what may be termed "enlarged roots" were found in asbestos workers, it may be that para vertebral duiness is one of th* esrlioct signs produced by the inhalation of asbestos dust, indicating congestive changes in the root areas and a choking of the lymphatics with dust. Reflex impairment of note, due to irritation of the lung tissue by dust, is, however, an attractive explanation. It does not follow, of course, that workers present ing these signs will ever develop a defi nite asbestos fibrosis. Clear.,, signs presented by any case of diffuse pulmonary fibro sis not only may be modified by changes produced by some intercurrent lung disease, but, ab -initio, will vary according to the state of the lungs be fore the onset of the fibrosis. Thus, x. i. s. PULMONARY FIBROSIS IN ASBESTOS WORKERS 209 atensity, but ords, wc find ebrai dulue&s , of impaired more extenjodated with losis. cussion note tantly-more 3 fact, at first the earliest confined to ore extended ? -conclusion -tip PP os on the left :----_--_=--^ir I i Qt that it has eliable single this type of no case has----------- ~ = s .in its ab- j ^ency with hat may be ere found in e that para- f j ^ s- ihalation of congestive 3d a choking ___ ust. Reflex irritation of however, an. ' It does not era presentvelop a defi- t -- ;[ * 5\ .= is presented onary fibromodified by mtercurrent o, will vary le lungs be- ... ;*sis. Thus, . ** - -=* ...... ......* --^1 - ".'----la ; 3.I. B. Va*. lean TT~ :-i the fibrosis may be implanted upon a to healed tuberculosis. That there is ' perfectly nonnal chest, in which case an extensive fibrosis is clear enough, the problem of diagnosis is straight- and that most of it is not due to asbes- forward. In other cases, however, tos is strongly suggested when examin- ~ preexisting root changes, so common in ation of the lower portions of the lungs ____ _ _ an industrial community, may be pres- shows that they are -comparatively -ent, or the lungs may be already the slightly affected. Further help *n seat of emphysema and chronic bron- these cases, of course, may be obtained ------------chitis.-or -of -definite -old 'tuberculous -fromthe history and symptoms. --. ~ ' lesions, or there may' be a massive The third type, also rare, is that in pleural thickening, the result of an old which changes following an old massive pleural effusion. All these examples pleural effusion on one side so obscure have been noted in the present investi- the physical signs of any dust fibrosis " gation, and others will readily oome to -as to render that side useless clinically mind. for diagnostic purposes. IT the side Although in most of these cases the affected by the pleurisy happens to be -dust fibrosis, if moderate in degree, can the right, the radiographic picture is be confidently diagnosed, especially also curtailed by the normal partial with the aid of radiography, it must be obscuration of the left lung base by the admitted that the problem becomes heart shadow. ~very difficult-when the dust fibrosis is -- These three types were, with the : comparatively slight, and the changes possible exception of the first, uncom- produced by other conditions are pro- mon, and are mentioned merely to call nounced and diffuse. Three types of to mind some of the ways in which an these esses have caused most difficulty asbestos fibrosis may be masked, in among those examined; fortunately, greater or less degree, by changes due numerically they were few. to other disease. The first of tlieae L> *iiere the duel Guiy passing reference need be made fibrosis has been implanted upon lungs to the other physical signs found in the already emphysematous. It seems asbestos fibrosis, since they do not - that, at any rate in the case of the differ materially from those presented asbestos fibrosis, until the fibrotic by silicosis. Chest expansion is dimin- changes get the upper hand, clinical ished and may be reduced to one-half ---------- diagnosis of the fibrosis in these cases --inch or even less in advanced cases. is impossible. Nevertheless, although Retraction of the apexes is common, the problem of the diagnosis of a and sometimes shows a peculiar feature fibrosis implanted upon an empby- differentiating it from that found in nematoue chest has caused some diffi- fibroid phthisis Tnstesd of thp irr- culty in this inquiry, it seems likely mobile and sunken apexes seen in the - that it can arise only under exceptional latter disease, the apexes are seen to ...... circumstances. descend during inspiration, and to rise _____ The second type of case which has again during expiration. This seems - - -* been a source of difficulty in clinical to indicate the anchoring of nonnal ____'' diagnosis is that in which there are apexes by fibrous tissue in the lower extensive bilateral fibrotic changes due portions of the lungs. Some confir- ___________VoLU V* I 210 THE JOURNAL OF INDUSTRIAL HYGIENE mation of this was obtained radio logically. Auscultation In tbe majority of the cases of fibrosis, tbe respiratory murmur is weakened, much or little, generally, more on tbe right side, and often still more at tbe base; tbe expiratory sound -is -weaker -than tbe Inspiratory, and often becomes less and less audible as one approaches tbe bases. . Transitional phases between this and harsbened breath sounds and pro* longed expiration are not uncommon, even in tbe rTM: w.wt. The iawer may be noticeable in the upper por tions of tbe lungs, but progressively diminish toward tbe bases. Other combinations were also noted, how ever. Tbe dry character of this type of fibrosis during most of its course is rather striking. Scattered fine riles and elides in tbe root areas, axillae, and bases were not infrequent; slight edema of tbe lower halves of tbe lungs was noted in one of tbe more advanced cfle;butinanuiubcx, no adventitious sounds at all were beard. Pleural crepitations, and rarely a alight pleural rub, were noted--these attacks seem to cause little pain--and in one case a little fluid at tbe right base. ... ------------- - - ------- ' No doubt this variability in tbe sounds heard on auscultation reflects underlying changes, temporary or permanent, in tbe June. and is depend ent, inter aba, on tbe extent of tbe fibrosis with Its associated pleural thickening--changes due to past dis ease, catarrh, or other intercurrent affection, and to tbe degree of compen satory emphysema present. - -- Symptoms Tbe symptoms exhibited by these cases of fibrosis, as might be expected, closely resemble those of silicosis. Tbe distribution of tbe main symp toms, and of one sign, cyanosis, which is included with tbe 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 OF FOUR COMMON* syM^TO^C, AND Or CYANOSI8, AMONG CASES OF FrBROSIS SYMPTOM * CASKS IN a e WBJCB 2 87 NTTOM < WAS PBXStNT a d a No. Per Cent. Cough........................... Cyanosis....................... Dyspnea....................... Expectoration.............. Pain.............................. SI 93 91 91 94 64 39.3 32 659 47 51.6 31 34.1 10 10 6 * Excluding those 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 cases complained of cough, or of short ness of breath on slight exertion, or wLvncu bowe aegree of cyanosis, whereas only about one-third com plained of expectoration, and onetenth of pain, or discomfort, in tbe chest. Also, while 14.6 per oent. of the cases had no complaints and showed no cyanosis, and only 3.4 per 3 bited by these ht be expected. . e of silicosis. >e main sympcyanosis, which iptoms for conable 3: A Tew "-' luded on the er of the synajK_ ;bt be assigned e fibrosis, such i ION OF FOUR :S, AND OF G CA8E8 v---- TC : CASKS IN ' * wncB ---------------- : STicrToac i WAS PBSSSNT No. Per Cot.- ----------- i 64 86.8 62 66.6 47 51.6 31 34.1 ..........*- "' 10 10.6 ch the presence to otner causes. SB of breath in tory of mild " - of dyspnea __ j" ! -r *r cent.-of the -------------ir-- h, or of short- \ exertion, or____________j of cyanosis, * n, and one- -j nfort, in the per oent. of-------- --* aplaints and__ . . only 3.4 per'-.rrfS? 3.1. B. Uaj, mo PULMONARY FIBROSIS IN ASBESTOS WORKERS 211 cent, presented all four oomplaints and were cysnoeed, 60.6 per oent. presented two, three, or four of the five items. Clearly, none of the four oomplaints, find asbestos dust irritating, but to this day cannot work with a cotton scutcher (as he occasionally does) without precipitating a coughing attack . or the presence of cyanosis, can be an within an hour or two. Although he infallible indication of the existence suffers from winter cough and some of fibrosis; but the presence of two of shortness of breath, he stated that his them, shortness of breath on slight health has been much better since the exertion, And cyanosis in some degree, change. in an asbestos worker, is highly suggee- ___Asbestos dust, therefore, bas only ________ _ r--tive,-In the absence of other evident very mild powers as a reflex irritant of ------------- cause. the upper respiratory tract, and is, in Nevertheless an advanced degree of this respect, comparable to free silica. fibrosis may be present, and little oom- This is an unfortunate attribute, since plaint made. Symptoms, unless dis it leads to the assumption that the dust . _______ tressing, are so often a function of is more or less innocuous. - -- the uaruepecxiveness of the patient. The second type of cough is more Slight degrees of fibrosis, too, give rise intimately associated with the develop to no symptoms, in the absence of ment of fibrosis, and occurs, or perhaps " an intercurrent bronchitis, since the is noticed, after a varying number of remaining sound lung tissue is still years' work. Usually it is present only __ _ amply sufficient for all purposes. _ in the morning on getting up, when---------------- " ~ Cough wss the most frequent symp after rather a sharp attack of coughing, tom, and was of two types. For a few a little viscid sputum "like an oyster" weeks after commencing work in a is brought up. A similar bout may dusty process, asbestos workers often occur at night after eeasing work; at find the dust irritating, and cough times it is sufficiently sharp to cause while in the dusty atmosphere; this retching. It is generally rather worse lasts for a few weeks, and then usually in winter, and may be noticed only disappears. The writer has noticed then. Although it closely resembles this effect on himself, but only while in smokers' cough, its features are pre a very heavy cloud of asbestos dust. cisely the same in nonsmokers. - The dust seems to be only slightly Persons giving a history of cough irritant in this way. One or two men dating from an attack of pneumonia or who bad previously worked in cotton other illness in childhood, almost in- -------- card toozds, -or blow rooms, and were 'variably state that the cough has not affected by that dust, stated that they beoome worse since working with -- were unaffected by asbestos dust. asbestos. One worker succinctly de- ~' Certainly asbestos dust does not cause scribed the cough as "first in the asthmatic attacks like these seen is turn, utvet uauMiee uic UUCCI. cotton card room workers. One man, Generally, this cough causes very - who migrated from a cotton card room little inconvenienoe and may pass un ("hard waste") nine years ago to an noticed until the development of some - asbestos card room, on account of the other symptom directs attention to the - ----- 1 " irritating effect of the dust, does not general state of health. Thus, out of vi.u Ho. I 212 THE JOURNAL OF INDUSTRIAL HYGIENE sixty-Bix eases of fibrosis, is thirty- and in the remainder of the cases, three (50 per oent.) the eough was good. ~ stated to have preceded the onset of shortness of breath, in twelve (18.2 per Radiography -- oent.) to have developed contempo Radiograms of the chest were ob raneously, and in twenty-one (31.8 per tained of 133 workers, or 35.5 per cent. - -- cent.) was either not noticed until after of the number examined clinically. _ the onset of shortness of breath, or, Of these, over 100 were taken by Dr. although the latter was complained E. W. Twining of Manchester, and of, cough was not admitted. Dr. N. Tattersalljof LeedSj and _the ~ `Complaints such as-1'colds go'to the remainder (except one) by Dr. F. L.---- chest/' and "frequent colds on the Henderson of Glasgow. To all three, VI" chest/' were not uncommon. Com I am much indebted. Dr. Twining plaint of spitting of blood was excep and Dr. Tattersall have devoted many tional; and in all cases in which this hours to the joint study with the writer ____ oomplaint was mentioned, the exciting of the radiograms, and have drawn uuac , pumaxily, some disease ireeiy on their wide experience of radi- ' other than the fibrosis--t.g., in one, it ography of the chest in furthering the was due to -pulmonary tuberculoma; purposeoftheinvestigation. in another, it occurred only during a Dr. R. S. Paterson of Manchester, prolonged attack of pleurisy; and in a too, added his experience to a final third, the hemorrhage was gastric in review of the films, and Dr. E. BarclayK origin. Cyanosis, a valuable sign now of Cambridge, lent his assistance__ when present, rarely amounts to more in interpreting some difficult -films; than a duskiness, or slight blueness, of to both, grateful acknowledgment is the lips; it contrasts, however, with the made. -- genera] pallor of the face with which The standard of radiography was it is often associated in these cases. very high; indeed, & high standard is Cyanosis in some degree was noted in indispensable, if it is desired to trace 50 per cent, ot tbe cases. It may be the cause of such a fine and diffuse absent even when there is a consider fibrosis as that produced by asbes able degree of fibrosis, or it may come tos. . .. and go. The films are superficially, but only Pain in the chest is rarely com superficially, comparable to silicosis. plained of, and then it is usually de In the earliest negatives studied with scribed as -"tightness of the chest/' ~Dr. Tattersall, a characteristic slight "soreness," or "aching." It was noted obscuration of the lung fields, a general in 10.6 per cent, of the cases. ----- lack of translucency, was noted. This Well-marked clubbing of the fingers appearance, for want of a better term, w z frT ZZSZZ. ucuviuiuttbvu &b "veiling.*' Dr. nutrition is hardly affected, except in Burton Wood has independently noted . the latest stages. Only ten (10.5 per (19) and confirmed this, referring to it cent.) were noted as being thin. In as the "ground glass appearance." one, the nutrition was very poor; in Dr. Tattersall also drew attention to "VH twenty-one (22.1 per cent.), fair; the more or less rounded "whorls" of - J.LH. May, i the cases, . est were ob- ' ' '== 35.5 per cent. " clinically. __ aken by Dr. y- .cheater, and -- eds, and the by Dr. F. L. To all three,-----Dr. Twining ----- ~ evotedmany ------------ -- iththe writer have drawn ienoeof radi- - irthcriLg the . _ _. an. -- -- - Manchester, :e to a final r. E. Barclay, iis assistance j fficult films; -- vledgment is rr-? :r-,~'^ ` .grapby was i standard is ired to trace ' and diffuse -J by a&ue `! __ __ j _ .lly, but only ; to silicosis. **"; ""-f studied with --7 eristic slight z. Ids, a general---------27- noted. This better term, _____ _ a eiling." Dr. - tdenfly noted eferring to it l appearance." : - - j attention to --------- . "whorls" ofT. 2. LB. Bat. mo -- PULMONARY FIBROSIS IN ASBESTOS WORKERS 213 varying size seen in the striation in the The radiographic appearances in the mid-zones in some of the films. earlier stages are most marked on the There was general agreement as to right side at the base or in the central the fine and delicate nature of the gone. This corresponds with the clin characteristic mottling. Dr. Twining ical findings. This preference for the (in a personal communication dated right side has been noted also in Aug. 2, 1929)--while lamenting that silicosis, by the South African ob there has been, as yet, neither time nor servers. The cases showing radio opportunity to study the changes from graphic signs of a du6t fibrosis have every aspect, and therefore his present been classified in three broad groups. views may be modified on considers This grouping, although unscientific, ___ tion oT all the evidence--states: ; ~1s convenient practically, considering the main purpose of this investigation. In general my opinion ia that the earli Indeed more precise classification est stages are not characteristic radio logically, but that the stage of fine dusty _ stippling is almost certain to be eventually provable as an early asbestos lesion. We saw it constantly in a large series of films, and after a little experience it is quite easy -- -to detect it. -- -- Some of the other eases showed a 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 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 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 groups of primary lobules making up a lobule, the walls of which are infiltrated. They certainly seem to correspond in size with the macroscopic lesions seen in the pathological specimen. The advanced cases show heavy basal and 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 iniu-mriu uiuiuiugft, vwiuiuuu i puciiiuuuw* eoniosis, 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 tos dust produces* a puluiumuy Huiosia 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 I think we ean recognise: radiologic picture with those of stand- ________ l._A very .doubtful stage of increased --ard silicotic films, is untenable. - - linear striations. 2. Fairly definite fine dusty stippled At least two general types of pul appearance. - monary fibrosis caused by inorganic 3. Coarser mottling with increased linear dusts can be recognized. A third, striations the purelv peribronchial 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. variety of fibrosis, might be added; or it may be that all dust fibrosis will be found to approximate more or less closely one or the other of these two . . v<ili Not 214 THE JOURNAL OF INDUSTRIAL HYGIENE types. These types are (1) that pro On studying the development of duced by oombined silica dust, an asbestos fibrosis as displayed in a series example of which is seen in asbestos of radiograms, and especially in the few fibrosis, and (2) that produced by free available taken a year or more before a silica dust, represented by silicotic fatal termination, one cannot help fibrosis. asking the question, "What is there These two types, while resembling here which could have this effect?" one another in clinical signs and symp The answer is that the damage to the' toms, differ materially both in the lung is much greater than it appears to nature of the lesion produced in the be when judged by the silicotic stand .Jung, and in the character of the asso- ard. Asbestos fibrosis is much more -dated radiographic picture. Thus, diffuse; it spins its fine web, as it attempts to weigh, consciously or were, crisscross throughout the lung, unconsciously, asbestos fibrosis, or any enveloping and eventually strangling dust fibrosis other than silicosis, by the ultimate lobular structure, rather means of the standard radiographic than depositing itself in numerous changes found in rilicoas, j unsound mcr.. v* *cao uuutiiculoci,asmelucosis. and is likely to lead to a misconception Thus, at any rate in the less advanced of the potentialities of the dust in ques stages, the radiologic picture of the tion. lesions does not impress the eye, uncon Bariham (8) gives an example of this sciously viewing it from the standpoint source of error in reporting the unex of silicosis. ... pectedly early death of a man affected The radiographic picture may show with a fine fibrosis caused by an ortho- soft and fairly coarse nodulation, but it clase basalt containing no free silica. is never so impressive as the nodulation Referring to some of the radiologic in a silicotic film. differences between the fine fibrosis of Paradoxically, the distinctive fea dusts other silica and the nodular ture, both clinically and radiologically, fibrosis of quartz dust (t.e., true sili of the asbestos fibrosis is its uniformity. cosis), he The uiuuesiy oi the symptoms; the unobtrusive, but diffuse, impairment Moreover, the coarse fibroais of silica gave of the percussion note; the homo olaar interspaces of normal long, while the fine fibroais presented a uniform granular mottling leading to the conclusion which ia probably erroneous that the actual develop_meat of fibrous tissue was greater ia s nodular fibrosis as silicosis than in a general geneous stippling of the skiagram; all are fragments of an entity, unmistak able when assembled, but enigmatic whendivorced. -------- ~ "" " Only two references to the radio ised fine fibrosis caused by silicates. To -e it appear* that the mechanical damage to the lung is greater in a fine fibroais than io a coarse whss both ara well developed. graphic appearances of the chest in asbestos workers have been traced: one I a report h? -lJ Pendergrass (10), and the other in an article by Burton Wood (19). The evidence obtained in the present Pancoast and Pendergrass together inquiry amply confirms this general with Miller and Landis examined "17 statement. - .--------- asbestos workers, 2 of whom showed ua. U&7, WO PULMONARY FIBROSIS IN ASBESTOS WORKERS 215 velopment of -- -- tyed in a series J iaiiyinihefew more before a cannot help________^ . Vhat is there ........ x. . this effect?"-------- ~ -SZ.--. lam&ge to the " a it appears to ilicotic stand- a much more ----- e web, as it " ' T out the lung, * Uy strangling_________ icture, rather "----------- :-- as in silicosis. " --? ' * eas advanced------------ r-cture of the eeye, unconie standpoint____ `____ _ re may show ' tion, but it modulation :inctive fea.diologicaHy, ' uiufoiui.iy. .ptome; the impairment the homo- " riagram; all , unmistaki enigmatic------- the radio*.. -- ie chest in *en twKwvJ- icoast and other in an - )). - - ss together____ vmined *`17----- -- om showed - first stage changes and the other and by the time the stage is reached 15 definite second stage appearances. when the features discussed above are, Of the men longest at work, one after in varying degree, positive, and the seventeen years* occupation showed radiologic picture is recognisable, the very definite diffuse, 'soft' spots fibrosis is not in its inception, nor even throughout both lungs, and another in its earliest stages, but is developed ahowed about the same appearance and fairly widespread. after fourteen years* occupation. We must, therefore, recognize an Very slight nodular shadows were _earlier state when the fibrosis is present ' ""'found In oneman after only two years* -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 offree drainage iently as the prefibrotic stage. - hilumward. In all instances the nodu- The indications of this stage are lai ahauows were characteristically indefinite, and some, at any rate, not `soft' and varied considerably in axe.** specific. If, however, they can be Their first stage appears to correspond determined and 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 distinguishworkers 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 363 exam original rock--a view difficult to sub ined (5.8 per cent.) were so classified: stantiate. Burton Wood (19) in a series of fif teen skiagrams of asbestos workers notes: **ine 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 Clinical Examination* Per (ses): No. Cent. FitrGii*................................ io 26.2 Prefibroticconditions........ 21 5.8 Radiologic Examination* U$S): Fibrosis........ --.............. 62 39.1 Suggestive changes sot definitely diffuse fi- _ brosia...,...................... ,22 ..16.5 -. the cases exhibit a 'ground glass' Many of these cases present a slight appearance, though on close inspection diffuse impairment of percussion note fine mottling is evident. . . . when --perhaps bfetter described as a slightly nettling if present it iZtCc&Scu cZic of icstowniw 1CH 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 r. lb. tuy. mo Voi-U No.t 216 THE JOURNAL OF INDUSTRIAL HYGIENE comparison with a radiogram taken prior to commencing work with ashes' toB. By such means the earliest stages of silicosis have been worked out by the South African observers, ~ There, the radiograms taken at periodic six-monthly medical examinations can always be compared with initial radiograms taken before the employees --are -permitted 'to~work ^underground, group is dismissed from any furthej consideration. - A general summary ofthe findings in the 374 workers who were examined clinically, classified under the most import&nt lesion, is presented is Table 4. Illustrative vases The salient points of a few cases are set out below to illustrate clinical and -TABLE 4.--GENERAL SUMMARY OF FINDINGS CLASSIFIED UNDER TEE MOST IMPORTANT LESION -caaxa o. ns- msonc c^vri* nows rCLMONAKT Tcssnco- Loasa i-i u b g_ B a PM \v: JTHTB H/lJtONAXT BE Z.MIONS s| s~ Is s s' Vi m ----- 5 5 16 % i < S % O 1 1 O s s Q I m < s a 1 "3 % e 3 w 1 Si s| s P i P 1 a 2 aaJ < u !i a O .58 0a_ |BBCCV 13 Sa a .!* sS S 0 a< *** 3 *j 9 V S3 a 3 2 xjO gbs* g3a. J fsa It s 3 bTS5 t .3 B 1O e i 3 J XMeX X B> 3 0-4.................. 92 0 8 6 0 0 0 0 5-0.................. 142 36 l 12 0 1 1 4 10-14 ............... 89'27 5 8 0 8 0 3 15-19................ ah* 1 1 1 0 0 1 20 and over-. 2! 1? rvt *V 0 i u 0 13 3 & 0 0 7 1 0 1 62 3 5 2 2 72 0 ? 0 3S 2 11n 1 010 1 Total............. 374j95 10 21 1 5 1 8 - Percentage... loojss.d 2.7 6.6 0.3 1.3 0.3 2.1 21 5.6 13 10 6 3 180 3.5 2.7 1.6 0.6 48.1 1 One cam of thickened pleura due to old gunshot wound. * One cue of emphysema due to gearing. ........ .. In other cases included in this group, diffuse weakening of the .respiratory murmur was noted, with fine sticky r&les in the mnt areas. At preecui no stress can be laid upon this group. _ The clinical changes are 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 nf the There are insuperable difficulties, however, in reproducing the finer changes depicted in the original negatires. - -Cm 1.--This worker, a female, aged 24, has been employed is asbestos for ten and one-half years--as a card tenter one year, >m any further f the findings in - -- were examined ler the most im- ." \ ited in Table 4. ~~ Cases r-- -r; a few cases are . ate clinical and-------------- UNDER THE ""`Z OTHER tTLMONART LESION'S v e 33 Oa 0 1 62 2 2 72 2 0 38 10 7 20 1 180 7! *! * 48.1 11 o> M adiograras are the radiologic of the cases, le difficulties, ;ing the finer ; original nega- i - -> - - .~ . female, aged 24, _-----~ri stos for ten and '^.L . tenter one year,----- 3.1. H. Kaj. mo PULMONARY FIBROSIS IN ASBESTOS WORKERS 217 and as a doubler nine and one-balf years. Her family and personal medical history contain nothing of note. She has no com* plaints and feels quite well. Her nutrition is good. Sbe is pale, but shows no cyanosis. Chest.--Sbe hss a chest expansion of 1$ inches. /No impairment of the percussion note is detected. The breath 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 ahowed some very slight and doubtful changes in the direction of in creased striation. ~ Case 2.--This man, aged 24, has been employed in asbestos for five years, carding and mixing. Previously he worked for four years in the cotton trade, yarn weighing. liie ioinuv aitti j^ejoyiiai xuedjcal iwwi.s contain nothing of note. He has had a slight morning cough and expectoration for a year. His nutrition is good. His color is fresh, and there is 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 sounds are harsh, and expiration is prolonged in the upper hslf of the right lung, behind; expiration is also prolonged over the left upper lobe, behind. The respiratory murmur is weakened at the right base, and the breath sounds are of a "whiffing" character. There are no added c/\,n/te A cl- >a<TTTrv of the right root, and slight haziness and striation in the central zones in both lungs, suggesting early fibrosis. Case 3.--This man. aged 32, has been employed in asbestos for six years in the card room, and as a stripper and grinder. Previously he was employed in a cotton card room for nine years. He had army service for five years, but was not gassed. He gives -a family history of asthma; otherwise there is oothing of note in his family or personal medical history. He has no complaints and feels quite well. Mis 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 old tuberculosis of the lung roots and gen eral increased striation, especially in the lower half of the right lung, suggesting early fibrosis. Case 4.--This worker, a male, aged 23, has been employed in asbestos for nine years, mostly mat tress making. His family and personal medical history contain noth ing of note. He complains of occasional pain in both sides of the chest, and perhaps a little undue shortness of breath on exer- Fic. 1.--Case 4: Moderate fibrosis. L'n* due degree of striation and fine mottling in central zones of both lungs; calcified glands in roots, with rather coarse striatioo in upper loues; ? interlobar pleurisy on right side, between the lower and middle lobes; emphysema at bases. tion. His color is normal. His muscula ture and nutrition are good. Chest.--There is no retraction of the apexes, but there is a slight Battening below the right clavicle. The percussion note is slightly impaired generally, behind, partic ularly on the right side. The breath sounds are weak, generally, and expiration is pro longed. No added sounds are detected. The skiagram (Fig. 1) shows aa undue degree of striation and fine mottling in the central zones of both lungs; calcified glands in the roots, with rather coarse striation in Vol. 12 lA 218 THE JOURNAL OF INDUSTRIAL HYGIENE the upper lobes; ? interlobar pleurisy on the moderate fibrosis, most marked toward the right tide, between the lower and middle bases. lobes; and emphysema at the bases. The Case 6.--This worker, a female, aged 31, case was diagnosed as moderate fibrosis. has been employed in asbestos for seven Case 5.--This woman, aged 40, has been yean, opening, and has been exposed to employed for eleven years in asbestos, for much dust. Her previous employment : most of the period mattress making. Pre* was non-dusty. Her family and personal viouslv she was employed in a laundry. history disclose nothing of note. She com She has recently been ill for three months plains of having had a cough for five years, with pleurisy (no bistoo' of tapping); otber- --and t>f "shortness of breath on hurrying. She is thin and undernourished, and pale. Fig. 2.--Case 6: 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 cough 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 eolor, and no cyanosis. Che**.--'There i* impairment of the percussion note over both, lungs, be hind, more noticeable at the bases. The respiratory murmur is weakened generally. Persistent crepitations and medium riles are noted low down in the right axilla. A skiagram showed diffuse fine striation 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 a chest expansion of onefourth inch. There is alight general impair ment of the percussion note, definite at the apexes and the bases. The breath sounds i.r<; vK, expimuou is engtu.lv prolonged. No 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, especially the right. This is a case of moderate, but fully developed, fibrosis. Case 7.--This woman, aged 48, has been M*y. mo * ( rked toward the female, aged 31, estos for seven >een exposed to os employment iy and personal note. Sbe comrh for five years, th on hurrying, ished, and pale. 1 *1 al fibrosis, mostly ling of right lung. are at |A-Ate. hair and in her expansion of one* ht general impair* t, definite at the be breath sounds lightly prolonged, .rd. Her heart is nurs are detected, tows a numi>cr of -* - n diffuse igs, especially the moderate, but fully aged 48, has been j. LE May. MM \ 1, PULMONARY FIBROSIS IN ASBESTOS WORKERS 229 employed in asbestos for thirty*two years-- about three years on eards, and the re* mainder as a spinner. She has done no other factory work. Her family medical history discloses nothing of note. Sbe has a personal history of nephritis seven or eight years ago, causing three months' illness. Her complaints arc: shortness of breath on hills, and winter cough for about six yean. Her nutrition is fair. She is rather pale. CAesf.--She has a chest expansion of one* half inch. No retraction of the apexes is noted. There is general slight impairment of the percussion note, behind. Breath sounds are harsh and sxpiration is pro* longed. No added sounds are heard. No gross 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 ola puerin tuuercmuua scars at the apexes. The case was diag nosed as general fibrosis. This ease 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 ease 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 62, has been employed in asbestos for twenty years as a weaver. He was previously a cotton and silk weaver. His family and personal medical history show nothing of nn*A <r>wnt *Vi* he wee revtrHeH eate child. His complaints are: shortDess 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, with some cyanosis. Ckeet.--Chest expansion is I inch; there is retraetion of the apexes. The percussion note is impaired over both upper lobes, in front, and over the upper two-thirds of tbe right lung, behind. -Expiration is pro longed at the bases. Pleural rub and incon stant riles are noted at the left base, and a few riles at the nght base. A skiagram showed a definite diffuse fibrosis with nodulation. This is a case of fibrosis in the early -advanced stage. .Cass 9.--This man, aged 41, has been employed for twenty years 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 ct* ?cr the l&s* two cr thrs^ *** otherwise none. His nutrition is fair only. His color is fresh, but there is slight cyano sis of the Ups, at times. Chest.--The skin is poorly elastic; there is some retraction of the apexes. There is an impaired, rather "boxy," note on percus sion, generally, especially over the upper half of the left lung, and over the upper twothirds of the right lung, behind, and in front. Respiratory murmur is generally weak. Expiration is slightly prolonged, but diminishing towsrd tbe bases. Pleural crepitations are noted low down in the right axilla. A fciagram showed a definite fine diffuse fibrosis. Neither lung lights up very toeu, auu uux>uuuili. uuUi iucic ie A Vcj fine diffuse reticulation and mottling-- moderate, but fully developed, fibrosis. The fine diffuse character of the radiologic appearances is particularly noticeable here. Case 10.--This man, aged 46, has been employed for twenty-five years in asbestos, during nine years 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 on exertion for three months; cough after a few hours' work in dust during 1t twr> or throo venrs with litflo or no expectoration; and pain in tbe left side of the chest for the last three months. His nutrition is good. He is pale, with slight duskiness of the lips. Chest.--There is some retraction of the apexes. The percussion note generally is impaired, and of a "boxy" character. Breath sounds are harsh and expiration is prolonged over the right upper lobe; else where the respiratory murmur is a little weakened and expiration is not materially prolonged. No added sounds are heard. TAe Oeart is normal, xnv skiagram trig. 4) shows diffuse striation and fine speckled mottling throughout both lungs--fibrosis, fully developed. Case 11.--This worker, a male, aged 40, VoL u No.* r -- i&M, it ::ik rrr 220 THE JOURNAL OF INDUSTRIAL HYGIENE Jus been employed for twenty-two years in asbestoe--during the first eleven years on cards and as a weaver, during which he was exposed to a considerable concentration of dust. During the remainder of the time he was employed on a non-dusty process, but was exposed to a less concentration of dust derived from other processes. His family and personal medical history give nothing of note. His complaints are: shortness of .breath on climbing stairs for 4be last five -----------years; alight morning cough and expectora- Fio. 4."Case 10: Fully developed fibro sis. Diffuse striation and fine speckled mottling throughout both lungs. tion 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 face. Cheat.--Chest expansion is 1 inch; 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 ehest. The breath sounds are slightly weakened generally, except at the right apex, but there is no gross 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. Club bing of the fingers has been noted for about two years. A skiagram showed an exten sive diffuse fibrosis-fibrosis in a fairly advanced stage. Case 12.--This worker, a male, aged 60, has been employed in asbestos for twenty- six years in the card room. Previously he -was a sawyer's laborer. There is nothing of note in his family and personal medical history. He complains of slight shortness 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 slieht evno** of the f*'** Cheat.--He has a chest expansion of three- fourths 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 exeept 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 noted at the left base, and some calcified glands in the left hiltim. The diagnosis was fibrosis in the advanced bulge. Cass 13.--This man. aged 66, has been employed in asbestos for twenty-one years as a weaver. For about sixteen years pre viously he was a cotton and silk weaver. His father died of "chest trouble" at the ago of 45; his sister died aged 15 of pulmonary tuberculosis. He has only been away sick a week or two in twenty-one years, and has never had any serious illness. His com plaints are: undue shortness of breath on exertion during the last two years; cough forth#1 last tvoor Fvr.-.;t.--r- ation is creamy, and occurs a fair amount of times. He has lost weight, and is thin. He is pale, but witb some cyanosis of the face, and with a malar flush. Cheat.--Chest expansion is U 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 id front. The mucoid, but is eulosis. Clubnoted for about Dwed an exten'is in a (airly male, aged 60, tos for twenty. Previously he nere is nothing rsonal medical light shortness' ent years, and t three or four ted to be nil. ition are fair, -face. icsion of three;n note L" in- over the left spiratory murole of the chest here there are medium riles, agram showed rhout the chest tippling. The ~^nee. There e. One old -l the left base, the left hilum. the advanced ! 66. has been n tv-one years en years pre: silk weaver. de"at the age of pulmonary -Q away sick a ears, and has -:s. His comof breath on years; cough s. Expectorair amount of I f <1U4U, ATtiV a of the face, s 11 inches; ;es. Dulness ?r the upper i over the left J.1. B. Bay, WO _. _.t S PULMONARY FIBROSIS IN ASBESTOS WORKERS 221 upper lobe, behind, and over both upper lobes in front. Breath sounds are rather weak, with prolonged expiration. Scat tered variable rhonchi and riles are heard over the right lung, behind, over the left upper lobe in front, and over the left root. The skiagram ahowed a definite diffuse fibrosis plus tuberculosis. Sputum was negative (one examination). The diagnosis was dust fibrosis in the advanced stage, with tuberculosis, probably active. Case 14.--This worker, a male, aged 36, ' commenced work in an asbestos plant in 1910, but was employed on other work until January, 1914. During the next five years, until early in 1919, about three years and nine months were spent in army serv ice, for nine months of which he was a pris oner of war, but he had two short periods if work in nsbestos - eleven months in the weaving, and six months in the mattress, departments. From early in 1919 to No vember, 1937, he worked in asbestos proc esses, but for only six yesrs and ten months in a dusty one (msttress making). He then ceased work. He was referred to a tubercu 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 aide, and a slight cough of only about six months' duration, with a small amount of grayish sputum. Dr. K. Tattersall states that at that time: "Dyspnoea was very marked, even on talking, and there was definite cyanosis. He had marked hollowing and respirator}' retraction at both apices, especially the right; loss of note over most of the right lung and the upper half of the left; bronchial breath sounds at both apices; fairly numer ous crepitations, mostly on the right side, and a pleural rub at the right base. He had a systolic bruit at the apex and pleuro pericardial friction. "I examined him a number of times, the last occasion being April 20, 1928. In that iilliu iiv U4U ioai, puuuub, iVll Vvi J Wvm, and the dyspnoea was increasing. The signs remained much the same, though occa sionally, if he got a cold, the moist sounds were more numerous, especially at the bases. Seven sputum examinations were negative, and up to the time I last saw him the sputum had remained small in amount, and its appearance did not suggest tubercle. "My diagnosis from the beginning was one of pulmonary asbestosis with possibly added tubercle. "1 took two X-rays of him, neither of which showed appearances suggestive of tubercle, everything pointing to a very extreme degree of fibrosis." He died on Oct. 13,1928. No postmortem examination was obtained. a Fio. 5.--Case 14: Massive fibrosis, with pieurai thickening, retracted ajx-xc-s, u<i pneumothorax on left side with incomplete collapse of lung. 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. Wsr service, of course, may have reduced his resistance. The skiagram (Fig. 5) show's a massive fibrosis with pleural thickeninc. retracted apexes, and nneuroothorax on the left side with incomplete col lapse of the lung. No doubt fibrosis of the type pro duced by asbestos dust can of itself lead to complete disablement, and Vol.U No. A 222 THE JOURNAL OF INDUSTRIAL HYGIENE finally to a fatal termination, even in illnesses are avoided. Ultimately, the absence of a superadded tubercu however, the margin of safety, already lous infection. diminished, is lost and the circulation The primary effect of the fibrosis slowly fails, with the usual signs of would appear to be that of causing edema of the lungs. More often, defective aeration of the blood, result however, an attack of bronchopneu ing in an added strain on the heart. monia, influenza, or other acute infec For many years, and even with an tion adds too much to the strain, im- -advanced -degree-of -fibrosis this may _pairs the cardiac .musculature, and "be of little Inconvenience, provided results in a fatal termination. physical exertion is limited, and acute (To be eonehded) BOOS REVIEWS Bleivergiftung. By Prof. Dr. Paul DiM-for d?? Hvgiccirchts Ic - tituts der Univereit&t Salle a. d. 8.; Priv.-Doz. Dr. Adolf Seieer, Oberauis- teat am Hygienischen Ixutitut Halle a. d. S.; udo Priv.-Dor. Dr. Stillfried LiUncr, Aaaistent an der Medizioiscbeo Klinik Halle a. d. 8. Paper. Pp. 79 with index, illustrations, and bibliogra phy. Berlin and Vienna: Urban A Sch- warzenberg, 1930. -- This monograph is divided into a short introductory or general section and a special section. The first port is devoted principally to a discussion of the outstanding diagnostic symp toms of lead poisoning and of the work done by Dr. Schmidt 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 poi8oniug. 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 an investigator who 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 298 references to the recent work and brings the literature of the subject down to 1930, is particularly valuable. "Bleivergiftung" may well be recom mended as a valuable addition to the library of students of public health.-- L. T. FairhaU. z * -XJ- -fc=5 r T J.LH. -----"May. mo -