Document bawzD9GjBpQV9ZVOw93nMRN16

FILE NAME: Owens Illinois Library (OWL) DATE: 1930 Apr DOC#: OWL008 DOCUMENT DESCRIPTION: Two Relevant Articles from The Journal of Industrial Hygiene and Toxicology - The Silica Dust Hazard in the Granite Cutting Industry & Pulmonary Fibrosis in Asbestosis Workers 4 i 1 THE JOURNAL OF INDUSTRIAL HYGIENE Volume X II APRIL, lO.'U) \ i miu; ii I T H E SILICA DUST HAZARD IN T i l l '. (IRANITH (TT T IX C . INDUSTRY* L. R. T hompson, M .D . Surgeon, United States Pahlir Health Sirn'ee AND Hollo H. B uittkn dssaeiatc Statistician, United States Public Health Sirnre IN tho past our knowledge- of the effect of industrial hazards on the health of workers has t*vn gained Largely from occupational m ortality statistics and the physical examinat ion of sample grou ps of cm ployees. 11 was believed that the- dust hazard in this country offered an opportunity for an investigation of a more intensive char acter, by observing groups of workers over a period of time as to tin* charac ter and severity of sickness which might be associated with the hazard. In order to study tin- health of workers in the dusty t ratios, six specific investigations wen- undertaken, each dealing with a different typo of dust. * Received fur publication Jan 13, t`.3il. A list of these dusts follows: 1. Calcium lust (Portland cement plant)1 2. Silica dust ^granite industry)1 3. M etal and other dusts (silver polish ing) 4. C arlton dust (hard foal n:iitimr)* 5. Vegetable dust (rotten milling) 6. Municipal dust (street sweeping) Two pajiers in regard to the study of calciHtn dust h ate been published in 1 T h o m p s o n , h. It . Hrundatiu. l b K-, Russell, A. I.' , a m i Moomfiidd, .1 J . : T h e H e alth of W orkers in D u sty Trades. I. H e a lt h of W o rk e rs in :i P o r tla n d C e m e n t P la n t. Ik S. P a h . H e alt h Hull. X - lT'b logs. : Russell, A. Ik, Hritten, U lb . '1hotup- suti. 1. It., ml lihiomlield, .1. I lie Health of Workers in Dusty Trades 11 Kxposts re to Sib. m i l s Dust, d Irani Ie Indus try) Ik tv Pul,. Health Hul! \k. t"7. I'd.'' ' Also a modite d . l u d y in so!' e ot I district. k - ' Si-., . T IIE O CCUR R E X tT . OK IT I.M O X A R Y FIB R O SIS A X D O T H E R R U LM O X A ltY A IT E C T IO X S IX ASBESTOS W O R K ER S* E . R. A. M eiiew eth er, M .D . //. M . .*/. -/'ce-r I*,/ Factories I nTUODVCTK'N Po n l y R IO R to th e com m encem ent of th is inquiry, in F eb ru ary . 192b, definite know ledge exi-ted of tw o death. of asbestos w orkers about whom there was expert opinion th a t the inhalation of ashes:.- dust h a d a t least c o n trib u te d to. if not caused, the fatal outcom e. T he first of these, in n-trosjK-ct th e m ost suggestive, only came to light som e y e a rs a fte r th e o ceu rret.ee. whe n full inform ation was unobtainable. A ll t h a t is k n o w n of th is ca-e. now- re fe rre d to a s -`th e M o n ta g u e M u rra y C ase," is co n tain ed in th e evidence given by Dr. M ontague M urray before the D epartm ental C om m ittee on Com pensation for In d u stria l D iseases in 1906 (1). From th is source, we learn th a t: The patient, a male aged 33, came under the care of Dr. Montague M urray at the Charing Cross Hospital in ib-- beginning of 18tM>. He had worked with asbestos for "some I t years," 10 years as a cari!m.,m hand, and the remainder in some other room of the factory, "where there was much less d u st." He volunteered th a t, 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 uicut 30 years of age. There is no note as to the nature of his work, previous to that in tiea-Uesti. fart"rv. lie was treated in the Charing Cross Hos pital for two months, and then returned to work. After a few months, however, he became ill again, and was re-adm itted to the Hospital in April, 1000, where he died. The post-mortem examination confirmed the clinical diagnosis of extensive pulmonary fibrosis. There was no evidence of pulmo nary tuberculosis, and examination of the sputum for B. tuberculosis was negative. The- second case was re p o rte d b y D r. W. E. Cooke in 1921, eighteen y ears later 2): The deceased, a woman, aged 33, who died in 1`j 24, had worked in asbestos for IS years, but interm ittently for the last 5 years, owing to periods of ill-health. T he post-mortem examination revealed, not only extensive fibrosis of the lungs, but also much change due to pulmonary tuberculosis. A lth o u g h C'o o k c (3) a n d S tu a r t M cD onald (4) were conclusively of th e opinion th a t in this case th e lungs showed a progressive dust fibrosis, to gether with a chronic tuberculous in fectio n , th e eti*>logic re la tio n sh ip be tween the inhalation of asbestos d u st an d fibrosis of th e lungs w ould h av e been strengthened by the absence of a tuberculous infection. CoMia.'.s case is, h o w ev er, of o u t standing im portance, not only because cause its ; attention i ganic dus ' silica max i puknonar | the silica. * of which M any ot , such as t ! chalk, a: i u e d in | therefore ties of th ' m o n a rv ti : C ooke's getierally t press: ti. i M urray < ! the evid D e p a r t t;: published overlook- m aterial < by that ( Since ( Grieve ha i group of i | tice, and I access to h In E ebr M edical <1 drew m y w o rk er w. I in one of * This case 1 been repoi | sented, 1 y logically, | fibrosis, u lolls infer tion inn. 111-.*. PULM ONARY FIBROSIS IN ASBESTOS W ORKERS 199 { cause its publication again directed T his case, at th a t tim e th e 'th ird of { attention t<> th e pos-dbihty that inr- which th e F actory D epartm ent had l panic dusts containing little or no tree knowledge, was. however, the first in 1 silica m ay bo productive of extensive which the four essential condition-;, i pulmonary fibrosis. Of these dusts, necessary to establish a relationship I the silicate'' form a very larpe class, between th e inhalation of asbestos du>t ' of which asbestos is but one example, and the developm ent of fibrosis. c*>uh- i M any oth er members of the class. lx* dem onstrated. These conditions I such as the feldspars, kaolin. French are: ! chalk, and pumice, are extensively 1. Work involving exposure to a.--!,,:-.; i u-ed in industry. T he im portance, dust. i therefore, of -limitin^r the wtentiali- 2. The existence, demonstrate- eliniva'b. ties of the class as producers of pul- and radiological!}', of a definite pulmonary f m onarv fibrosis is clear. fibrosis. 3. The absence of previous or present in \ Cooke's case was the first to lx> fections known to cause pulmonary (i!,r -i; * generally reported in the medical --c.t;., tuberculosis, intlurn/a. nr pn>- t press; the facts of the M ontague monia. j M urray case, although contained in 4. The absence of previous or present the evidence presented before the D epartm ental Com m ittee in 1906, and work involving exposure to other dusts, which might cause pulmonary fibrosis. published in 1907, wore liable to be T hese conditions being fulfilled, a overlooked in the mass of im portant relationship between th e inhalation of material on industrial diseases elicited asbestos d u st and the development of by th at Committee. th e pulm onary fibrosis m ay bo pre Since C ooke'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 w hether th e supervention of this d i - tice, and has courteously allowed case in an asbestos worker was an access to his records. exceptional occurrence, o r evidence of In F ebruary, 192>>, D r. MacGregor. a grave h ealth risk in th e industry, was Medical Officer of H ealth for Glasgow, now apparent, and steps wen- taken, drew m y attention to an asbestos forthw ith, to obtain primn June evi worker who was receiving treatm ent dence in proof, or disproof, of the exist in one of th e hospitals in th a t city. ence of such a risk. This case, th e details of which have A num ber of w orkers in asbestos been reported by II. E. Seiler (5), pre were selected anil examined clinically sented, both clinically and radio and radiographically. The findings logical]}', sinus of a diffuse pulm onary invited fu rth e r investigation th ro u g h fibro.'is. will; is i evidence of a tubercu out the indu.-try. " i 'h the result th a t a lous in te r!.. .i, <in furUi'T invc'i na C< 111! U'*-ie-l t i - - l . M i l i r v i n v - i ! V i l e r t h e tion ini'- : iu-tri:il s nied. - . 11 . "'I fJ 200 THIS JOURNAL OF IN DU STRIAL H Y G IEN E with the carding, spinning. and weav ing processes of the industry. In the meantime, in March. 192$, the death of an asbestos worker tone of Dr. Grieve's cases) occurred in another part of the country, and. on post mortem examination, a condition of widespread fibrosis of the lungs, with out tuberculosis, was revealed. The microscopic examination also disclosed the presence of the curious bodies. In 192S. 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 survey of the events leading up to the present in quiry may be complete, it is neee.-sary to review the investigation made in 1910 to 1911 by Dr. Gollis 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 samefactory. Following this, extensive inquiries were made, a medical report on all the employees in the factory concerned was obtained, and Dr. Collis and Miss Whitlock investigated generally the various processes in the industry with respect to the evolution of dust, methods of ventilation, lost time due to sickness, etc. Also inquiries were made of the Canadian government as to the conditions in the asbestos quarries and mills in that Dominion, evidence of increased sickness arid mortality rates among the workers. and any methods of ventilation which had been found of especial value. The result of this investigation did not conclusively prove that asbestos possessed injurious properties, but it pointed to the probability that such was the case. I t is interesting to con sider why it was that no conclusive proof one way or the other could be obtained, then, as to the injuriousness of asbestos dust. Some, if not all. of the factors which affected the position then are, in varying degree, continu ing factors, and have an important bearing on the present inquiry. Their operation, while providing a solution to this query, also affords an explana tion to another pertinent question: Why is it th at this industry, founded in antiquity, has only recently excited attention, by reason of its raw material becoming suspected usacause of indus trial disease? The answer appears to be that in the past it was not practicably possible to obtain proof of the injuriousness of asbestos dust, considering the limita tions imposed by the state of the indus<ry, 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. Precise knowledge of the morbid affection.- of the lungs produced by the inhalation , ' !;-> was more fragmen I'. tary than i was clearly evidence plu mission on (Quarries, i porting in 1 know wheth- containing fi a pathologic though the Beattie in : may occur." or two that r definite eve effects of sc* lungs (.$) (9 In 1910. r; both its tech aspects, was so far from 1 status of bei the diagnose lungs, was a! In additio ure of exhati t dusty proces ' plete as it w t in modifying I duration o f: tions result): the dust, much more ! intervening ; present imp. | to again, i A n oth er f: still tends \ deleterious ; dusts, is the > mortality ra j.- of the degr l dust encoui: I occupation- u value in .< t into "a. I T LM uX AUY TllItO SIS IN ASBESTOS WORKERS 201 tarv 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 th a t 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 ou the lungs ($) (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 being an indispensable aid to the diagnosis of the dust diseases of the lungs, was an unused ally. In addition, the existence of a meas ure of exhaust ventilation in the most dusty processes of the industry', incom plete as it was. had important results in modifying the onset, course, and duration of any pathologic lung condi tions resulting from the inhalation of the dust. This influence has been much more pronounced in the period intervening between 1912 and the present inquiry, and will be referred to again. Another factor which has tended and still tends to obscure the possible deleterious effects of the non-silica du.-ts, is the general u>e of the phthisis mortality rale a> a comparative index of the degree of mjuriousiiess of the dust encounters, i o t !:>* various dusty Occupations. Yio- while oi area value in sep _ " ,.r V ndo-tries into > ,. i. show an excess m ortality from phthisis, and those which do not--as well as being a com parative 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 liv ing dismissed as more or less innocuous. Evolution of dust is only one factor, though an im portant one. which may cause variations in the phthisis mor tality rate in different industries. Wages, hours of work, aggregation of workers, am ount 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 du sts upon the lungs, the singular attributes of pulmonary fibrosis, the most impor ta n t of the diseases caused by the in halation of dust, m ust 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, hut is aware of his undue shortness of breath on extra effort. Usually, how e v e r , ie- a-oribes :t to r !11 s <*ri*-r than tie- hi-! h<- is ii-1 h . As the h-e:;-.- M " ---- : M. no i 202 T in: jo n iX A i. o f in o fs t im a i. h y g ie n e a stage is readied when the lungs can do little more than maintain lit'e: and the shortness of breath is extreme. Even in its terminal stages, the disease. (deceitful to the last, may masquerade as chronic bronchitis, pulmonary tu berculosis, bronchopneumonia, or the like. While more or less acute cases of fibrosis closely simulating miliary tuborculosishnve occurred, even in this country (Id), they have all been asso ciated with the inhalation of dense asbestos dust has a totally different physicochemical constitu ion from th a t of dusts containing much free silica and causing silicosis. It was felt th a t although much valuable guidance could be -obtained from the methods of investigation of silicious dusts, care had to be taken to keep an open mind, so as not to lie unconsciously biased in the direction of assuming that the effects of the dust. if any, must In* com parable in some degree to those of crystalline silica. ent mix* mat tile Uhi free sue! mix- r um! :! me.' I tibr hot' concentrations of free silica dit-t. and are, fortunately, the exception rather than the rule. The difficulty of diagnosing pulmo nary fibrosis, especially in its early Asbestos and the Asbestos I xdcstky Asbestos The term asbestos is a collective T t stages, or if complicated by tubercu name, of no definite minralogie 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 attainm ent of from one another in chemical compo precise knowledge of the extent to sition and physical properties, but which the various industrial dusts affect the lungs. Difficulties and obscurities still im pede, though to a less degree than in which resemble one another in their finely fibrous feature and flexibility (14). Their value depends on the facility with which they* are capable of i Ai the past, any investigation into the effects of an industrial dust upon the lungs of those exposed to it; but prior to the War, although there were certain slight indications th at asbestos, in being split up into long and flexible fibers, which can be spun like cotton and woven into cloth; on their resist ance to heat and acids; and on their insulating properties with respect to ( tc I 1.1 t d; ai- common with some other dusts, might produce permanent pathologic changes in the lungs, it was not possible to obtain evidence sufficient to prove or disprove this hypothesis. At the outset of the present inquiry into what, if any, pulmonary diseases workers exposed to the inhalation of asbestos dust are more prone to con tract than the general population, it was considered essential to view tinproblem afresh, and with eumpioii- heat and electricity. Varieties of asl>estos possess these qualities in differing degree. Com mercially, therefore, selection is made by the manufacturer of that variety and grade which is most suitable for the purpose in view, regard being paid to ordinary economic factors, such as tin* cost of the raw material, and the price which the finished article muy be expected t>>command. ( 'iti<i-_rti'i i-!it< oi a sb e s to s o f t he a t:- P' F- ti is i O' d t \ 1 ft i detachment, because of the fact that s-tum a - : -mi'-ty. I tit with differ i t ''***-* lT I.M O N A R Y FIB RO SIS IN ASBESTOS W O RKERS * -j(t7 cnt countries of origin. are frequently bined w ater, and usually more cal mixed iti the preliminary processes of cium, alum inium , and iron. Members manufacture. Thus Canadian chryso- of this group are resistant to acids, tile m ay be mixed with Russian, or but are more difficult to spin, some Rhodesian chrysotile. and so on. I.ess being quite unsuitable for this purpose. ! frequently, totally different varieties, such as amosite and chrysotile, may be mixed. The m ost im portant members of this group are croeidolite, amosite, ami tremolite. Practically speaking, all th at goes Croeidolite and amosite are mainly under the name of asbestos, in com silicates of iron, the former having a merce. is either fibrous serpentine or a beautiful lavender-blue color, th elat ter fibrous mineral of the amphibole, or being brownish-gray. Both are spun hornblende, group. The former is the and the yarn is woven into cloth for most important commercially: but various purposes such as acid filter strictly, the mineralogists confine the ing, and for making into insulating TABLE 1.-COMPOSITION OF SERPENTINE AND -AMPHIBOLE VARIETIES OF ASBESTOS MINERAL <3KOIT VARIETY CERCEKTAGE '~-T SiOj AljO FeO Com MgO CaO Na0 K,0 bined Fe,0, Wat-r Strj/cmiht. Chr>oot ilt.i 39-42.5 0-3 7 0 7-4 4 39-43 0-0 35 13 3-10 Croci<j.,liti; 50.5-52.1 0-1 35.S-37.4 0-3 0 75 6 2-9 1 6-4 5 (liorr.- ' Amosite 48-53 1.2-9 4 34-44 0 7-6 4 .. 0-2.5 2-3 A blende) : Tremolite 57.2 0.9 3 2 22. S 13 4 10 6 0 3 2 4 term asbestos to fibrous forms of horn m attresses, as well as for other pur blende. These two types are sharply poses. Both are produced extensively t distinguishable, chemically and miner- in South Africa, from which quarter all alogicully. required commercially is obtained,. Serpentine asbestos, or chrysotile, is Amosite, a com paratively recent dis a hydrated magnesium silicate, con covery, is found there in very large I taining practically no calcium, a high deposits; its use is steadily increasing, percentage of combined water, and a the initial difficulties associated with l--w percentage of iron. This variety the m anufacture of textiles from this is very suitable for spinning, but is variety having been overcome. at tached bv aci<Is. Nearly SO per cent, Trem olite, found in various quarters of th e world's production of asbestos is of the world, has been mined in north derived irom ( un.ula, and is of this ern Italy since the time of the Roman-. I V ariety; the remainder comes mainly Its chief use is in the m anufacture <>f from Smith Ainert and Ru-.-ia. asbe.-.t-ws lmi'b-.r-d and fur iiln id.g < 11.a n . p l , . . . i.-.niblemle. v.ari- pnrji. i-i" I ; 1 !.. t 204 THE JOURNAL OF INDUSTRIAL HYGIENE sources, shows the main differences in the composition of these four varieties. Only a very small proportion of the world's production of asbestos, which is between 300.000 and 400.000 short tons per annum, is suitable for 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 utilized 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 has 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 m at tresses, brake linings for motor cars, fireproof curtains, and the like. In 1880, three years after the dis cover}' 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, and by 1925 to over 330,000 short tons (15). The imports of asbestos (all grades) into the United Kingdom rose from 18,591 tons in 1922 to 33,520 tons in 1927 (16). The figures for 1927 refer to Great Britain and northern Ireland only. Of these quantities S.844 tons and 3,794 tons, respectively, were reexported. Thus the consumption of asbestos in this country trebled within five years. The Industry On considering the uses of asbestos one is astonished, Dot only a t the wide range of articles manufactured front this mineral, in greater or less propor tion, but also at the diversity of indus tries which nowadays find its use necessary, either in the form of the raw material, or as manufactured articles. Evidently, therefore, with the multi plicity of processes and dusts encoun tered in the ramifications of the indus try, discrimination would have to be exercised, and some limit set to the processes included in the inquiry. The processes selected may be divided, roughly, into 1. Processes involving the manipulation of asbestos, either pure, or admixed with a small proportion of cotton, or other vege table fiber. 2. Processes involving the manipulation of asbestos together with other dusty ma terials. 3. Processes involving the making up of asbestos cloth into other articles. Group 1 entails exposure to asbestos dust mainly, and to cotton, or other vegetable dust, very 'slightly; group 2 entails exposure to asbestos dust in very varying amounts, and also expos ure to divers other dusts, such as brick dust, magnesia, kicselguhr, fossil meal, and cement; in group 3 the exposure to asbestos dust--provided no other as bestos processes are being carried on in the vicinity--is, in the majority of cases, negligible. Processes belonging to all three groups may be carried on in the same factory, and workers may transfer fn>m one department to another -'.o' tic po eo: in off' an ca re~ bt C. al. F tc in fl H' g; o d i: o ii f. o d 1. ! t t r 1, t a i ; V. 1TLMONAHY FlBHoSIS IN ASBESTOS WOUKEHS 205 Investigation into the intricate ques the weaving of fabrics, which them tion of the effects of mixed dusts, while selves are used for a multitude of pur possibly productive of some general poses. but. braided together, are made corollary, would lose much of its value into ropes for use as steam packings in the absence of knowledge of the and other purposes. The interstices 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 results. For these reasons, and also use to which the rope is to be put. because the Montague Murray case, Asbestos mattresses, used for blan Cooke's, Grieve's, and Seiler's cases keting steam engines, and for other all occurred in processes included in insulating purposes, are made of asbes group 1, it was considered advisable tos cloth stuffed with asbestos fiber. to exclude, as far as possible, from the The stuffing material may be, however, inquiry all workers exposed to the in slag wool, magnesia (containing ap fluence of mixed dusts, and all those proximately 15 per cent, of asbestos not employed in processes included in fiber), or kieselguhr with a small per groups 1 and 3. centage of asbestos fiber. The man The processes included, therefore, ufacture of mattresses filled with an- the crushing, preparing, sieving, mixtures of asbestos fiber and other opening, mixing, carding, spinning, materials 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, as 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 efforts 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 variatioas 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 In-cause 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 ri 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-filtered asbestos tioned result in the evolution of dust, is carded and spun with no admixture although bv no means to the same of vegetable fiber, but usually asbestos extent. Differences in plant, quality yarns contain a or- of either cotton of asbe.-t*>s uel. methyls of manufac- or metal wire. lutv. ty;x: of fin:,!,- !article. and extent Asbesto- v..n;. : . -::iy u-<-: for >:' application f . a . \ <-n!ila ' III. i all result in variations in the evolution and most probably an overestimate, of dust in similar processes in different is 000. Thus, about 2,200 appears to factories. be the total population at risk in this i Variations in the evolution of dust in country, for the purposes of this in different processes being of outstanding quiry. This figure, however, does n o t importance, a series of samples of dust include the large number of workers from the air of workrooms was col engaged in the processes in group 2 lected. by means of the Owens jet- which involved exposure to the influ apparatus. ence of mixed dusts, of which asbestos Population at R isk.--A calculation of is but one. and commonly not more the total number of workers employed than 20 per cent, of the mixture. in the processes already enumerated as This estimate of the population at risk, although it may be excessive, is TABLE 2.--DISTRIBUTION', ACCORD useful, since it enables us to judge of ING TO LENGTH OF EMPLOYMENT, the adequacy of the sample of workers OF (A) 775 WORKERS ENGAGED IN ASBESTOS PROCESSES AND (B) SELECTED SAMPLE <>F 3*53 WORKERS examined, and to apply more correctly the incidence rates of any pulmonary affections disclosed by the examination of the sample (30). (A) (B) The sample examined (after eleven cases are excluded of fibrosis and pre- TR3. EMPLOTED ! S. jf ,* a * z z Vu fibrotic conditions due to causes other than the inhalation of asbestos dust) numbered 363, representing 16.5 per 0 -4 .............................. ,. 4s3 62.3 SO 24.5 5 -0 .............................. ..I 200 25.S 141 38.8 10-14...............................! 51 6.6 84 23 2 15-19.............................. . | 24 3.1' 28 7.7 cent, of the population a t risk, esti mated as above. The manner of selection of the sample m ust be referred to, since just interpretation of the 20 and over............... , 17, 2.2 21 5.8 results depends upon a due apprecia Total........................ . ,| 775100.0' 363100.0 tion of the relationship of the sample to <<5 ' undt work The call}' year- is a' work C. tabi* met! exar emi grea whii each tary at w X sit y the effe* emp Pit De| sate star as \ rath fact* I? The principle of selecting primarily whi* included in this inquiry, but excluding those longest employed was adopted; l! those engaged in processes included in but regard was also paid to the other wh; group 3 in which the exposure to as end of the scale, so as to obtain infor wor bestos dust is negligible, gives a figure mation as to the length of exposure to scat of approximately 1,000; if we could dust necessary before effects are mani pra add to this the number of workers fested, and also as to the particular engaged in handling pure asbestos fiber process in which the worker was } Siili inq only, in the preliminary stages of the engaged. I t was felt that, in this way, all i processes included in group 2, wc the maximum information would be enti should obtain the total population at risk from the effects of asbestos dust it self. Unfortunately, this latter figure obtained in the shortest time. Table 2 shows the distribution, according to length of employment the i this \ 4 urn is unobtainable; but a rough estimate, (not necessarily in one factory, of inf i r rr V.J 77o workers engaged in the processes a center which is equipped with the under review, and of the sample of 363 necessary X -ray plant, and where the workers, distributed in the same way. services of a consultant versed in the The enormous preponderance numeri science of radiography of the lungs are cally ol workers employed under five available. Furtherm ore, it must not years in these processes is striking, as be overlooked th a t such examinations is also the very low percentage of are voluntary, and not, as in South workers employed ten years or longer. Africa, compulsory. Moreover, re Comparison of the two parts of the peated and protracted examinations table shows th a t the effect of this only result in the exhaustion of all method of selection is that the number concerned, and much depends on the examined in each succeeding five-year willing co-operation of employers and employment group is a progressively employees, since the only incentive is greater proportion of the total number a desire to further the common welfare. which could have been examined in Radiography, therefore, has a differ each particular group. W ith a soli ent function in these inquiries, than tary exception, all those examined were when it is applied to individual ca.-o- 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 that of sity, of radiographic examinations of replacing careful clinical examinations, the chest in investigations into the as has been recently foreshadow ed i is. effects of dust upon the lungs, lias been p. 40), but primarily th a t of being emphasized repeatedly by Watkins- an indispensable aid in diagnosis, Pitchford, and reaffirmed by the especially of doubtful cases, in the | Departmental Committee on Compen sation for Silicosis (17). A high standard of radiography is essential; determination of complicating It-ions, in measuring the extent and progress of the disease, in locating the point at { as W atkins-Pitehford phrases it, the which the earliest radiographic signs radiograms must be "technically satis appear, and finally as a chock 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 i were In a general inquiry, such as this, carried out a t each factory, in a room which involves the examination of set apart for the purpose, suitably workers in factories, large and small, wanned, and with the necessary scattered over the country, it is not appointments. On occasions the noise practicable, nor is it necessary, con of traffic 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 these difficulties were over all the workers examined. The dislo come or minimized. cation of work in a factory, caused by All the selected workers w'ere exam the absence of a number of hands for ined by the writer. At three factories, this purpose, cannot be viewed with however, a n u m lc r of workers were unconcern, eqierially when, :is is not examined jointly with Dr. K. L Middle- infrequent, tl f i<t>ry is remote from ton. His far-reaching experience of the \ 20S THE JOURNAL OF INDUSTRIAL HYGIENE pathologic changos in the lungs, pro duced by the inhalation of various dusts, was of groat 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 radiographic examinations were completed by the middle of November, 192S, prior to the commencement of the influenza epidemic early in 1929. C linical 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 than nor mal, and there is a sense of resistance imparted to the plexor finger. 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. I t is best elicited by rapidly, 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 c-!.- these, it diminishes in intensity, but still persists. In other words, we find tacked on to the paravertebral dulness 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 are bilateral, although the signs on the 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 dulness is one of the earliest 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. Clearly, the physical signs presented by any case of diffuse pulmonary fibro sis not only may be modified by change.- produced by some intercurrent i'lia: di.-e;t.-e. but. nb it a>!! w e PULMONARY FIBIiOSIS IN ASBESTOS WORKERS 209 the fibrosis may be implanted upon a perfectly normal chest, in which case the problem of diagnosis is straight forward. In other cases, however, preexisting root changes, so common in an industrial community, may be pres ent, or the lungs may be already the seat of emphysema and chronic bron chitis, or of definite old tuberculous lesions, or there may be a massive pleural thickening, the result of an old pleural effusion. All these examples have been noted in the present investi gation, and others will readily come to mind. Although in most of these cases 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 cases have caused most difficulty among those examined; fortunately, numerically they were few. The first of these is where the dust fibrosis lias been implanted upon lungs already emphysematous. I t seems that, at any rate in the case of the asbestos fibrosis, until the fibrotic changes get the upper hand, clinical diagnosis of the fibrosis in these cases is impossible. Nevertheless, although the problem of the diagnosis of a fibrosis implanted upon an emphy sematous chest has caused some diffi culty in this inquiry, it seems likely that t can arise only under exceptional cireum-lance-. i ; type of case which has 1 '' i.dfioulty in eUrnea! to healed tuberculosis. That there is an extensive fibrosis is clear enough, and that most of it is not duo to asbes tos is strongly suggested when examin ation of the lower portions of the lungs shows that they arc comparatively slightly affected. Further help in these cases, of course, may be obtained from the history and symptoms. The third type, also rare, is that in which changes following an old massive pteurai effusion on one side so obscure the physical signs of any dust fibrosis as to render that side useless clinically for diagnostic purposes. If the side affected by the pleurisy happens to be the right, the radiographic picture is also curtailed by the normal partial obscuration of the left lung base by the heart shadow. These three types were, with the possible exception of the first, uncom mon, and are mentioned merely to call to mind some of the ways in which an asbestos fibrosis may be masked, in greater or less degree, by changes due to other disease. Only passing reference need be made to the other physical signs found iti the asbestos fibrosis, since they do not differ materially from those presented by silicosis. Chest expansion is dimin ished and may be reduced to one-half inch or even less in advanced cases. Retraction of the apexes is common, and sometimes shows a peculiar feature differentiating it from that found in fibroid phthisis. Instead of the im mobile and sunken apexes seen in the latter di-e.t-e, the apexes are seen to descend during inspiration, and to rise MV":' ' ';n_r expiration. This seems O' . ' 'i.e .sficlr.niitr of normal 210 TI1K JOURNAL OF IN D U STRIA L H Y G IE N E mat ion of this was obtained rauiologieallv. In the majority of the cases of fibrosis, (lie respiratory murmur is weakened, much or little, generally, more on the right side, and often still more at the base; the expiratory sound is weaker than the inspiratory, and often becomes les- 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 bo noticeable in the upper por tions of the lung', 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 rales 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 a t 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 the fibrosis with its associated pleural thickening--changes due to past dis ease, catarrh, or other m tercum nt affection, and to the degree of compen satory emphysema pr^'t-nt Symptom* The symptoms exhibited by these cases of fibrosis, as might be expected, closely resemble those of silicosis. The distribution of the main symp toms, and of one sign, cyanosis, which is included with the symptoms for con venience. is given in Table 3. A few cases have been excluded on the grounds that one or other of the symp toms complained of might be assigned to causes other than the fibrosis, such TABLE 3.--D ISTRIBUTIO N OF FOUR COMMON SYMPTOMS. A N D OF CYANOSIS, AMONG CASES OF FIBROSIS SYMPTOM ~~ TASKS I.V " WHICH - SYMPTOM < WAS PRESENT - 2 No. :CPe.nrt. .......; <u Cyanosis............. ........; 93 D yspnea.............. ........! 91 Expectoration... ........1 91 Pain ................... .......i 94 54 52 47 31 ;1 10 i 59 3 i 55.9 , 51.6 i 34.1 I 10 6 1 Excluding those in which the presence of the Bymptom 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 showed some degree of cyanosis, whereas only about one-third com plained of expectoration, and one- tenth of pain, or discomfort, in the chest. Also, while 14.6 per cent, of tie- eases had no complaints and . cvaTM* i- : ' cent, pri were eya two. thr> C'learl. or tin* p: iniallibh of flbro^ i them, p: I exert-on j in an a-' j tive. in cattle. Neve' fibrosis plaint ; trussing the '.nt j Slight i ! to no an int' remain amply Corn tom. ai weeks dusty ; find t! while ; lasts f< \ disapp this efi | a very j The d j irritan \ who h j card r ' affeetc ' were j CTt:i j asthn ! cotto: i wtl" 1 M { t t ITLM OXAKY F f im o s is IX ASBKSTOS w o h k k r s 211 coni, presented all four com plaintsnnd find asbestos dust irritating, but to were eyanosed. IVO.Oper cent, presented this day cannot work with a cotton two. three, or four of the five items. scutcher (as he occasionally does! with t'learlv. none of the four complaints, out precipitating a coughing attack or the presence of cyanosis, can be an within an hour or two. Although he infallible indication of th e existence suffers from winter cough and some of fibrosis: but the presence of two of shortness of breath, he stated that hi- 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 sugges Asbestos dust, therefore, has only tive. in th e absence of oth er evident very mild powers as a reflex irritant of cau^e. th e upper respiratory tract, and is. in N evertheless an advanced degree of this respect, comparable to free silica. fibrosis m ay be present, and little com This is an unfortunate attribute, s o w plaint m ade. Symptoms, unless dis it leads to th e assumption that the du -i tressing. are so often a function of is more or less innocuous. the introspectivenoss of the patient. The second type of cough is more Slight degrees of fibrosis, too. give rise intim ately associated with the develop to no symptoms, in th e absence of m ent of fibrosis, and occurs, or perhaps an intercurrent bronchitis, since the is noticed, after a varying number of rem aining sound lung tissue is still years' work. Usually it is present only amply sufficient for all purposes. in the morning on getting up. \\b<-n Cough was the most frequent symp after rather a.harp at tack of coughing, tom. and was of two types. For a few a little viscid sputum "hke an oy.-mr" weeks afte r commencing work in a is brought up. A similar bout m ay dusty process, asbestos workers often occur at night after ceasing work: at find th e dust irritating, and cough tim es it is sufficiently sharp to cause while in the dusty atm osphere; this retching. It is generally rather worse Lasts for a few weeks, and then usually in winter, and may be noticed only I disappears. The writer has noticed then. Although it closely resembles I this effect on himself, bu t only while in smokers' cough, its features arc pre i a very heavy cloud of aslestos dust. cisely the same in nonsmokers. The dust seems to be only slightly Persons giving a history of cough irritan t in this way. One or two men dating from an attack of pneumonia or who had previously worked in cotton other illness in childhood, almost in card rooms, or blow rooms, and were variably state th a t the cough has not affected by th a t dust, stated th a t they become worse since working with ! were unaffected by asbestos dust. asbestos. One worker succinctly de < 1 C ertainly asbestos d u st docs not cause scribed th e cough as " first in the asthm atic attacks like those seen in throat; later catches the chest." cotton card room workers. One man, (Jenerally, this cough causes very \ wh-> migrated from a cotton card room little inconvenience and may pass utt- w ("liar i waste") nine years ago to an noticcit u nt i l the development of s o m e I * ,r.| mom. on account of the tic - ymp'om directs attention to the ! i i ! d n ~ t. i>ie^ r.<>t - :! i, -i itc of hcalt'.. Tims, out of 212 THE JOURNAL OF INDUSTRIAL HYGIENE sixty-six cases of fibrosis, in thirty- three (50 per cent.) the cough was stated to have preceded the onset of shortness of breath, in twelve (1S.2 per cent.) to have developed contempo raneously. and in twenty-one (31.8 per cent.) was either not noticed until after the onset of shortness of breath, or, although the latter was complained of, cough was not admitted. Complaints such as "colds go to the chest," and "frequent colds on th e 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--e.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 sign when present, rarely amounts to more than a duskiness, or slight blueness, of the lips; it contrasts, however, with the general pallor of the face with which it is often associated in these cases. Cyanosis in some degree was noted in 56 per cent, of the cases. It may be absent even when there is a consider able degree of fibrosis, or it may come and go. Pain in the chest is rarely com plained of, and then it is usually de scribed as "tightness of the chest," "soreness," or "aching." It was noted in 10.6 per cent, of the cases. Well-marked clubbing of the fingers was noted in a few cases. The general nutrition is hardly affected, except in the latest stages. Only te n ?10.5 per cent.) were noted as 1 big thin i:i one. the nutrition w;,- t'.vent v > } and in the remainder of the cases, good. Radiography Radiograms of the chest were ob tained of 133 workers, or 35.5 per cent, of the number examined clinically. Of these, over 100 were taken by Dr. E. W. Twining of Manchester, and Dr. X. Tattersall of Leeds, and the remainder (except one) by Dr. F. L. Henderson of Glasgow. To ail three, I am much indebted. Dr. Twining and Dr. Tattersall have devoted many hours to the joint study with the writer of the radiograms, and have drawn freely on their wide experience of radi ography of the chest in furthering the purpose of the investigation. Dr. R. S. Paterson of Manchester, too. added his experience to a final review of the films, and Dr. E. Barclay, now of Cambridge, lent his assistance in interpreting some difficult films; to both, grateful acknowledgment is made. The standard of radiography was very high; indeed, a high standard is indispensable, if it is desired to trace the cause of such a fine and diffuse fibrosis as that produced by asbes tos. The films are superficially, but only superficially, comparable to silicosis. In the earliest negatives studied with Dr. Tattersall, a characteristic slight obscuration of the lung fields, a general lack of translucency, was noted. This appearance, for want of a better term,, was denominated as " veiling." Dr. Burton Wood has independently noted (10) and confirmed thi-, r<Yrring to it :> the "ground t r t ranee " v ; PULMONARY FIBROSIS IN ASBESTOS W ORKERS 2 b? varying size seen in the striation in th e mid-zones in some of the films. There was general agreement as to the fine and delicate natu re of th e characteristic mottling. Dr. Twining (in a personal com m unication d ated Aug. 2. 1929)--while lam enting th a t there has been, as vet. neither tim e nor oppon unity 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 stages are not characteristic radio logical lv. but th at 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 scries of films, and after a little experience it is quite easy to detect it. Some of the other cases showed a few grouped lesions, like rosettes or leopard markings, each component being about the eize of a primary lobule. These are similar to lesions sometimes seen in tuberculosis. In the asbestos cases I regard them as being groups of primary lobules making up a lobule, the walls of 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 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-Jcaued stages, but I think we can recognise: 1. A very doubtful stage of increased linear striations. g. Fairly definite fine dusty stippled aj>| earan. e. d. ( '..arst r m ottlin g with increased linear ri.tt I E'i. 1 i h- --i li-sioiH wit ti , r;u chanae.-; ai. 1 T h e radiographic appearances in the earlier stages are most market! on the right side at the base or in the central zone. This corresponds w ith the clin ical findings. This preference for the rig h t side h as been n oted also in silicosis, by the South African ob servers. T he eases showing radio graphic signs of a dust fibrosis have been classified in three broad groups. T his grouping, although unscientific, is convenient practically, considering th e m ain purpose of this investigation. Indeed m ore precise classification based on the particular radiographic changes noted m ight well be m islead ing at the present tim e. M uch combined clinical, radiologic, a n d pathologic stu d y is required into th e whole subject of these fine types of d u st fibrosis, which have been noted in workers exposed n o t only to silicate d usts other than asbestos, but also to o ther 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. T he hypothesis that, because asbes tos d ust produces a pulm onary fibrosis w ith consequent deviations from the norm al in th e lung skiagram , the de gree and potentialities of this fibrosis can be assessed bv comparison of its radiologic picture with those of stand ard silicotic films, is untenable. At least two general types of pul m onary fibrosis caused by inorganic d u -ts eati be recognized. A third, pre-i-riiiim the purely peribronchial :;< *v i",' iii-r o s ! - . m ight be a d d e d ; ........' ' .............. 214 THE JOURNAL OF INDUSTRIAL HYGIENE ! types. These types are (1) that pro On studying the development of duced by combined 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, aud v2; th a t 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 lung, and in the character of the asso ard. Asbestos fibrosis is much more ciated radiographic picture. Thus, diffuse; it spins its fine web, as it attem pts 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 silicosis, is unsound more or less isolated foci, as in silicosis. 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 Badham (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 m ay 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 than silica and the nodular ture, both clinically and radiologically, fibrosis of quartz dust (i.e., true sili of the asbestos fibrosis is its uniformity. cosis), he states: The modesty of the symptoms; the | unobtrusive, but diffuse, impairment Moreover, the coarse fibrosis of silica gave of the percussion note; the homo clear interspaces of normal lung, while the fine fibrosis presented a uniform granular mottling leading to the conclusion which is probably erroneous that the actual <1-volnpment of fibrous tissue was greater in a nodular fibrosis as silicosis than in a general geneous stippling of the skiagram; all are fragments of an entity, unm istak able when assembled, but enigmatic when divorced. Only two references to the radio- ised fine fibrosis caused by silicates. To graphic appearances of the chest in me it appears that the mechanical damage to the lung is greater in a fine fibrosis than in a coarse fibrosis when both are well developed. asbestos workers have been traced: one in a report by Paneoast and Pendergrass (10), and the other in an article by Burton Wood '!!)). The evidence obtained in tie- pn-.-t-ni. Pancoa.-t and iVieli-rer-'S together V* inquiry amply confirms tlii- g- i.-i-l aitli Miller and I.midis '\m iiiie-: -17 I -111 lenient. I first stage 15 definiu Of the me: seventeen very deb throughou showed a after for Very slig found in i occupatiostage cas first stag indicating hilumwai lar shad 'soft' ano Their fir.with sta with sta; It ap: these ob as being ture of original stantiute Burto teen sk notes; skiagrtuto asbe shadow uffectire of the 1 shadow the ca appear fine ne inure l:-h> i the sk t" '" PULMONARY FIBROSIS IN ASBESTOS WORKERS 215 first staple chan pcs 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 recognizable, 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 showed 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 one man after only two years' in slight degree, and also when there is occupation. Most of these second evidence of choking of the lymphatics, stage cases 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 aa the prefibrotic stage. hiluimvard. In all instances the nodu The indications of this stage are lar shadows were characteristically indefinite, and some, at any rate, no: `soft' and varied considerably in size." 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 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 series of fif teen skiagrams of asl>e.stos workers notes: "The most noticeable feature of skiagrams of workers exposed longest Clinical Examinations (,363): .Vo. Fibrosis.................................. 05 Prefibrotic conditions........ 21 Radiologic Examinations P tr Cent. 26 2 5 x to asbestos dust is the presence of (133): shadows suggesting a diffuse fibrosis uffectirig chiefly the lower two-thirds of the lungs. The fine quality of the shadows is worthy of note. Some of Fibrosis.................................. 52 39.1 Suggestive changes not definitely diffuse fi brosis................................ 22 16.5 the eases 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 le t ter described as a slightly more definite mottling is present it increased sense of resistance felt on lacks the coarse quality described iti percussion, mostly of the right lung, the skiagrams of chests showing prieu- at least as eontrusted with the left, ( m>'. :;j,Kw. e.g. South African gold and a-sociated with some weakening V mm'-: -. . . " of tie- j-e.-pirat.ory murmur. Ib u b - 1 1 r ! ' i. ia t u r a ilo ti ..J a. be.-!"- :! !\ ' ' is e u'iy stnue eouM be dHeele.i ? \ Cl." ;ii v. hip o n l y b y m e a n s 216 THE JOURNAL OF INDUSTRIAL HYGIENE comparison with a radiogram taken prior to commencing work with asbes tos. By such means the earliest stages of silicosis have been worked out by the South African observers. There, the radiograms taken at peri odic 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 fu rth er consideration. A general summary of the findings in th e 374 workers who were examined clinically, classified under the most im portant lesion, is presented in T able 4. I llustrative Cases The salient points of a few cases are set out below to illustrate clinical and TABLE 4.--GENERAL SUMMARY OF FINDINGS CLASSIFIED UNDER THE MOST IMPORTANT LESION 1 PULMONARY 5 i CA*Ea Ipibrotic TUBERCU H ,, !C riBROsts; LOSIS s 5a Dz 3 X t1 H 5P ' 1! - 5 s- ! S fi m ^ 3 c.S s w t* 5 a 5 do u , * c e z 'J 1 c, fe a ho j 8 Z8 ---- - * W ! ao c '< 5 < 1 S -a 5 X a 1 1 3 w W9 ;! 9a 2 I* 98 s ! 3 34 1 93 a 3 < j 0fc. ? i 1 a A { 1-- 3 0 - 4 .................... 92 0 3 j 5 0 0 0 0 13 5 - 9 .................... 14236 1 12 0 1 1 4 3 10-14.................. 8927 5 j 3 0 3 0 3 5 15-19.................. 3015 10 0 1 0 20 and over-- 2117 0 j 0 0 1 0 0 0 T o ta l.............. 374'95 10 -21 1 5 1 8 21 P ercentage... 100!25.4 2.7| 5 .6 0 .3 1.3 0 .3 2.1 5.6 Due to Other Causes j Other Active Lesions Other Inactive Le gions WITHIN NORMAL LIMIT OTHER i s PULMONARY LESIONS f i X i t>* - "k e ae 5 < - ' * 5 2 *>> *Sc u>% u 20 * I ja* b Sa0 7 1 0 1 62 3 5 2 2 72 0 3 2 0 3S 2 1l0 7 i 0 10 1 13 10 6 3 180 3.5 2.7 1.6: O.sj 43.1 1 One case of thickened pleura due to old gunshot wound. * One case of emphysema due to gassing. In other cases included in this group, diffuse weakening of the respiratory m urm ur was noted, with fine sticky rles in the root areas. At present no stress can be laid upon this group. T he clinical changes are so slightly marked that until comparative radio gram s are availahl'- it would Le un- u t o d r a w tiny ik-dui-t-,..!.- : 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. r "> ! Thi- , . ( I yt. and a- I Her faroutait- y p>od <>., ill. In'SIinli- is right u. in t right r skiasra doubt: piva- (\- tuni ! and in. vi-:*e-- illn.lltll .-ligi.' for a p..|..r I > !'r,:: rigiit i ha.-'-. <`\-|iir:i tlii' ri pruh't Tin- r. right 'hie 1 simrid 1 ()f till' strit : suggr- ! C.A empi, card ! l'n vi- room i f o r : ; -, a fini, i- io.' v i-.*** ,!! IT L .M O X A H Y l 'I BROS IS IX A SH K STO S W o R K K U S 217 ,im as a doubler nine and year s. o l d t u b e r c u l o s i s o f t h e l u n g r< rot s a m i ! g e n Her family and personal m dical history o r a l i n c r e a s e d s t r i a t i o n , r < t v e i a i l v r ii t i l e contain nothing of noto. She has no coin l o w e r h a l f o f t h e r i g h t l u n g . *ou g g - t m g i a :!> plainis ami feels quite well. Her nutrition f i b r o s i s . i* good. She is pah*, hut shows no cyanosis. t h w K 4 . - - T h i s w o r k e r , a m a h '. a g t 1 --v l. I t'ht s t .--She has a chest expansion of l i a s b e e n e m p l o y e d i n a - b < i t o * ft *r n i n e inches. \ o impairment of the percussion y e a r s , m o s t l y m a t t r c s s m a k i t : ig. H i - i a m i l y note is detected. The breath sounds in the a n d { > e r s o u a l m e d i c a l h i s t o n ' c o n i a i . '; m u h - right lung are weaker, generally, t h a n those ! ! lg o f n o t e . | f e c o m p l a i n * o f o c r a - 'i **m 1 m ?In* left. 'Apirution is prolonged at the p a i n i n b o t h s i d e * o f t h e <}]-i . a n d :>e r i t a p s right root; no added sounds are heard. A a l i t t l e u n d u e s h o r t u r - * o f bTeat i i 1a e \ < r - skiagram showed some very slight and doubtful changes in the direction of in It ert a- i stria! ion. C\-m 2 . --'flus man. aged 24. has bwri cnq !*yrd in a>ho>t s for !tv* yvars. carding and mixing. Ihw io uslv he worked tor four year- m the not.n trade, van weighing. Hi- family atol personal rm lieal history r contain nothing of note. Ib* has had a i slight morning rough and expectoraren for a w a r His nutririoti is good. His color is fr< -d. ami there is no cyan"-U ' > 1 There i* so/no impairment of th" ' -i:] p. r e i o n m u 1*ver i In* middh* t Idrd of t he right lung, behind, and slightly at the right Itase. The breath -minds are harsh, and expiration i< prolonged in the upper half of the right lung, behind; expiration is a!.-- prolonged over tin* left up|wr lobe, behind. The respiratory murmur is weakened at the right base, and the breath sounds are of a " whiiimg' character. There are no added sounds. A skiagram showed enlargement of the right root, and slight haziness and Fin. 1. - C a s e 4: Moderate fibro-is Fn- striation in tie* rent ral /ones in both lung'5, suggesting early fibrosis. <\\>k 1. This man, aged d2, has been due degree of striation and fine mottiing iu central /.ui-oif iM.th lung- : e : d n \ . j glands in roots, with rather roar.-* - ' n a w m in upper lole.x; ! interlobar ph-uri-v on right employed in asbestos for six years in the side, between th** lower ami middle lobes; d' X card room, and as a stripper and grinder. emphysema at bases. Previoudy In* was employed in a cotton card room for nine years. He had army service* tion. His color is nomini. His muscula for five years, but was not g a - ^ 'd. He gives ture and nutrition are good. a family history of a sthm a; otherwise there i 'i t t ' t . There is no retraction of the i- nothing of note in his family or personal apexes, but. then' i- :t slight Ila! tenihg below djeal hi.-tory. He has no complaint* and the light clavicle. The p e m i' -to !i Dote is e|- quite Well. H.S tlltlM'.. iut UTe S V<T\ -light!* impaired generally, behind, parti*- Hi' color is pah*. a le- >ho\\- *iu: ; oil the right - ile. I he b fva h -mi fid- f 1>* i ,- -Sight h. ; ire.ie-jT , . i ! ,. 11*t:t 1Sv. and \pirat i!! i- pr- \ . ;< h j . >: !; ; Iii-t I I !.. j I IS T in: JOURNAL o r INDUSTRIAL u y o ik n k t !io u p p e r lobes; ? i n t e r l o b a r pleurisy on t he ridili .-i.it*. boi weiti t he lower aiui mi ddl e lobes; anil e m p h y s e m a at tlu* bases. T h e ease wa> diagm**id a** mod* rat* til C . w : . T h b \ ' o m a n . aged -to. ha: been f nip'i'V. d j\-r r h - w n \ear.- ih a<besto>. t\r most t h e p-rh*d m a t n v -- maki ng. P re\ i*12^!> >hr ua > e mp l o y e d in a l aui ul ry, >!.iv ha* r e c en t l y U r n ill for t hree m o u t h s w it h i\: uri sy -no h b t o r y o f t ap pi u g ; therwi" !. : :'-i its :\ a:; i ;>* r-otsa! medical K bt o ry m o d e ra te tibrnsis. m ost m ark ed to w ard th o bases. C ask 0. - T h is w o rk er, a fem ale, aired 31, h a s b e e n e m p lo y e d in a s h o s r.w *'or < e \ e t t years, opening, an d has been e\po> ed to n m eh d u s t. H er previius em p lo y m e n t w as h en -d u sty . H er fam ily an d p erso n al h isto ry disclose n o th in g of note. She co m p la in s of h a v in g h ad a ro u g h fo r rive \e a r s , a n d of .hortness of b re a th on h u rry in g . S he is th in am i u n d e rn o u rish e d , .in i p ate. F n . "2.-- C a>` C: Mn< lenite. but ful iyTl h-Veb. peli, libi*. ISis Knlarged glare b in oil] !.... is; u n u s e ft IIt* m o t t l i n g in b o t h Ulig'. ' -pe ci al l v tie- right . K im 3 .- C a s e 7 : C e n e r a i fibrosi*, m o s tly linear, b u t w ith little m oti ling of rig h t lu n g . O ld p u e r i l e t u h e r e u i o u s -`e a r s a t a p ' A-.- are n e g a tiv e . S h e c o m p la in s of h a v in g h u d a w inter cough for th ree or four years, and of fdiortness of b rea th on exertion since her a tta c k of p le u ris y . H e r n u tr itio n is g o o d ; h e r w e ig h t is s t a t i o n a r y . S h e ha** n o r m a l co lo r, a n d n o rvam >is. ('h> . '/ . - 'T h e n - is mine g e n e r a l im p a i n n e J i t o f th e p e r c u s s io n nte o v e r b o th lu n g s , b e h in d , fnore n o tic e a b le at th e bases. T h e r e s p ir a to r y m u r m u r b u are-md gi-in-rallv. P e r s i s t e n t e r e p i t a t ion* a n d m e d iu m r `d- s a r e n o ti d 1>\\ d*w n m t i* us: : \ s k i a g r a m s h o w e d di*' 1:-*' - i* ' <.; f*i- r;*i , h r ..........1o .g : ' ' D u s t is p re se n t on h er h a ir an d in h e r n o strils . Chrat. --She has a rhest expansion of one- four th inch. Th er e is siigli! general i m p a i r ment of the pereu.-don hole. definite at the apexes ami the bases. The breath sounds are weak; expiration b dighib pn-h.nged. \ o added sounds are heard. J b r heart is n ot e n l ar g ed , atei te murmur' are d e t e c t e d . T h e >ki.tgrafll d ig 'J h a \ -, n u m b e r o! enl ar g ed gl and - if: i-otii r*-!-. a!:u : ditfu-** M e * H e * ? !*. g !!; :-r i g ,-} t'- W l i e * iti 1t i i.; i< . -a ` !-. .... ,1 , J ,:r . ! u r vd v i em ploy about t m uim ler i o ilie r f; h is to ry a pel's I veal's a H er eon h ilb . at Her mu / * h a h ' in. Holed, of fio>oUleb tinged gro-" tie- s*< Vet* t ! - l i o n w ith : Then >e :1 1 h o -rd Th I tk H in-* rlit r le .- * ! in t li m ail'' (' has I yearc o t t pers* n o te c a te of bi for t exp It- i ( is n not f r* *r rig- '- * * * < *- V . **, \ m . M O X A U Y K IM IO S IS IN A SB K STOS W nW K Iil.'S 4 e m p l o y e d in a s b e s t o s f o r th ir ty - tw < y a r< -- e m p l o y e d for t\Yen:> Wars it: a-b. -t.'- in a b o u t t h r e e v i a r s o n c a r d s , a n d t h e r e m a n y ca paci ti es. Tin re i- ti ' king :' mu c m a in d e r a s a s p in n e r . S h e h a s d o n e n o in his tam ilv history. He gi\< - a h>.e-\ ,.f o t h e r f a c t o r y w o r k . H e r f a m i l y im - d ie a l p ne um o ni a a n um be r i \ . v - a g i n - h i s t o r y d is c lo s e * n o t h i m r o f n o t e . S h e h a s complaint - a r e a l ittl e -hurt: -- by. . h a p e r s o n a l h i s t or> o f n e p h r i t i> s e v e n r r i g h t n e x e r t i"U f.<r t ii. i a - ` * u . ; i y e a r s a g o , c a u s i n g t h r e e m o n th s * i l l n e s s . o t h e r w i - e n o n e . H i - m i t r i t i u i . - fai r :..- . H e r c o m p l a i n t s art* : s h o r t n e s s o f b r e a t h o n H S C o lo r 1- f r e - |I , b u t t h<T' i- - `igh* ili" - lulls, an d w in te r cough for ab o u t s i\ vears. H e r n u tr itio n is fa ir. S h e is ra th e r p ale. SIS tf t he p>. at t inte-. t Vi * \ - - The skin i- ......... i- . b., iv <' f i rst .-- S h e h a s a c h e s t e x p a n s i o n o f o n e h a l f i n c h . N o r e t r a c t i o n *f tie* a n e x e s is n o te d . T h e r e is g e n e ra l slig h t im p a irm e n t of th e p-reu>sion n o te , b e h in d . B re a th is s ome re1tract i`i: *. ' !: 1 i- an impaire *!. rath**r :'. .>n o. *v -itu g'-m- rai!> . *-t*e.:! >v- - f !- ' , ' f* half of *1 ft JUg . ... " 1 t{o : - ... fe** >mitid > a r e h a r s h a n d e x p i r a t i o n is p r o lo n g e d . N o ttd d e ij --o i t*j^ :\r.- h- v ; \ i thirds n: tin* right ;Ur,.g. * r i' o. n >ut;r. b`. -nira' -r. _ g ro s s e n l a r g e m e n t .o f t h e h e a r t i- mt-*. W eak |-.x ojraM" '- t- t h e s e c o n d s o u n d i< t o lj tid t o n a c c e n t u a t e d o v e r t lie a o r t ie a r e a . T h e d i a g r a m |- ig d but bruito -hi ug povai-i *!.' crenbaMur i- are m?-; v. 1' ' .n _1 - h o w s a ge?-rai f ib r o - i- . n .u - t . v ,i.*-ar. n -p w i t h a l i t t l e m o t t l i n g c ?!,. rig n * . u n g . T h e r e a r e a 1- O VefV O i d PU n . e tur r e ib 'o 'j- a si; la \ -h, gf.rn ' ubi!.- u-i*. N* i1 :n . j r ' - . , ' well, at.-: ?Ill-oJjghu-i* '*' *; M 'al's a* t h e a p e \ r - I h- *a s '' w a - h a g - .'itc * r-i ii-'.i.i* !!. n *' ' n o se d a s g e n e ra l tior-i-. T h is e a s e >ho<thl b e c o m p a re d w b h (\i< fi. I n <`a s e t t h e r e w a - a h e a v y r \ p u - u r r t o fno<|eiaT' b m ; 'h i \ : V '. Tile line b ]ffil-e eba r.-u-:. ja[/f>ea ram- s l- parti'-'i.arc. : - :i- ' -V - : . d u s t e x t e n d in g o v e r a few w a r - ; in b. p r e s f \ \ * U . l o 'Dii** I n : :! . : C 4' . . i a * U e n t c a s e t h e r e \ \ a - e x p o s u r e a v*rv m u c h e m p lo y e i :*T |U ( ;:l - . ! a - le s s c o n c e n t r a t i o n o f h is t, e x c e p t p o - s j i . l y lu r in g !i i* year.- <*: w h ic h n>- w a - m* \ - in t h e f ir s t t h r e e y e a r s , im e x t e n d i n g ver p o s e d t* lu s t. i ' * r I'leV i !. . - a i ' u - m any years. reu iaim i r he w a- <mphy* d n t h a rd ( .'a s k V T l i i s w o r k e r , a m a le , a g e d tVJ. r o o m , a n d m a t t n s - m a k i n g I h - a n .i iv h a s b e e n e m p l o y e d in a s b e s t o s f ,,r tw n tv a m i j mi - ifiit l m e d i c a l h i - n . r \ ; -**i *.- i. t h y e a r s a s a w e a v e r . H e w a - p re v i u s iy a i n g o f hot e i ! I- ' rupia III t - a : ... c o t t o n a t n l s ilk w e a v e r . H is f a tn l iv a iid o f b r e a t h o n e x e r t i o n p ,r :. n, p e r s o n a l m e d i e a l h i s t o r y s h o w n o t h i n g o f c o u g h aft r a few hour- w-<tr. :*-' ; ing n o t e , e x c e p t t h a t h e w a s r e g a r d e d a* a l !i- t }* l a - t ' a . I.r 1l.P \ V* n> c a t e c h i l d . H is c o m p l a i n t s a r e : s h o r t n e s s e x p e c t o r a t i o n ; a m i p a i n in : -n -i <; of B re a th o n e x e rtio n , a n d on g o in g u p s ta irs , th e c h e -t lo r th- la -t th re e tn u n tn - lli- f o r t h r e e y e a r s ; m o r n i n g c o u g h a m i a l i t t l e n i l t r i t i o l i is g u ild . lb - i- p a l , w it it - l i g h t ex p e cto ra tio n for th e last th ree w in ters. H e is tlitti a m i p a le , w ith *wiue c \a m - -. d u sk in e ss of th e lips. b/v b. There j- -une- r t ;.n-t iu. .; ih Cfu.<L C h e s t e x p a n s i o n is 1 i n c h ; t h e r e apexes . T ic* percu^-mm not* generally is r e t r a c t i o n o f t h e a p e x e s . Tin* p e r c u s s i o n i> i mpaired, ami of a "b \v ' character. mti* is i m p a i r e d o v e r b o t h u p p e r lu b e s in Breath -uicls are hur.-h ami expiratiun i- f n n t, a n d o v e r t h e u p p e r t w o - t h i r d - o f t h e prhnge i ovir the riglit uppr i*b-; i j-e- l i g h t l u n g , b e h i n d . K x p i r a t i o n i- pr>- whr- tii- respiratorv inurnetr is -t iitr}* lu li g e d a t l h e b a - s P l e u r a l r u b a t: i im *on . ntii -\pira r?u!i i- nut (nar-Maiv - 1 a lit r a l e - at*e M u ted a t t },* 1< : i I i - < . an I a ^ \ > :i l a 1 4 - ; Jn I - , ; !' w : .: - a t J h e rig tit i -a-- A - . .1J, * ' i ! : t ,p e blV:;-.- !; t |'u - 1- i `3 '--.t li'* i 220 t iik jo r n x A i, o r in d u s t iu a l iiy ijik x i: In# been cinph'.ved O r twenty-two year# in -to#-'hiring tli" first eleven year# on "rmi-= -ith3 ns !1 weaver, during wliieh lie was expose! :i raid,- concentration of dust During th e rem ainder ot tin- time he w-n |.nipl>'."',l on a non-<lnsty process, hut was ,.\po#od to a less concent rat ion of ilust tlerive.l from oilier processes. Ills family anil |>ersotial nieilieai history give nothin!; of note. His complaints are: shortness of iireath oti climbing -t a il s for the last five vears- -light ttiornitni cough ate! expectora- FtO. 4.--f u s e 10: Fully ilevelopeil fibro sis. Diffuse strlatiott ami fine speckled mottling throughout both lorn's. tion for about the same time; anil slight aching of the chest in front, below the left clavicle. IIis n u trition is good. There i# alight cyanosis of the face. C lin t.--C hest 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, hehltel. ami over the right upper lobe in front. The note is " boxC over the remainder of the cheat. The i.r. ath sound- arc slightly weakened gem-:.a i l V. , \e. pt r th e right a|-.x, but tie r.- i- m. .t I.xpiral iou i- jir"i"i ! 'r** ii a *- e - over the right upper lobe, in front. The heart is normal. Sputum is inueoid. but is negative for ltacillus 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. C ase 12.--1This worker, a male, aged GO. has been employed in asbestos for twentv- six years in the card room. Previously he was a saw yer's laborer. T h ere is noth ing 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 t . t... nil. His musculature and nutrition are fair. There is slight cyanosis of the f a c e. ( 'lust.--He has a chest expansion of t hree- fourths inch. The [s reussioti mo,. s im paired generally, especially over the h i t upper lobe in front. The respiratory m u r m u r is Weakened over the whole of the idlest except the left upper lobe, where th ere are whistling iireath sounds, and medium rales. The lu-art is normal. A skiagram showed very extensive changes throughout the chest of a coarse type without fine stippiiug. Thu roots showed a choked appearance. There was heavy mottling at the base, o n e old tuberculosis focus was noted at the left base, an d some calcified glands in tin- left iiilum. T he diagnosis was fibrosis'in tin- advanced stage. C ase 13.--This man. aged tit;, h as been employed in asbestos for twontv-one years as a weaver. Fur about sixteen year# pre viously he was a cotton and silk weaver. His father died of " chest trouble" at the age of 45; his sister died aged 15 of pu lm o n ary tuberculosis. He has only been away sick a week or two in tw enty-one year.-., am i lias never had any serious illness. Ilis com plaints are: undue shortness of iireath on exertion during the last two years; cough for the last two or three winters. I-Apcctor- ation is creamy, and occurs a fair amount, o! times. He has lo s t weight, and is thin. I b is pale, but with some cyanosis o f 1 1,.- face, and with a malar llu-h. Clllt. Chest e\|ia:.-ioII 1- 1, inches; there is ret rad io), of I .hies# r.OI'c: l,,be- 11. .-IK *. roil , \er A i t "* ( t`. tfl ' \ i 1 i tl M M i r* I. i i lTI.M O X A liY FimtOSIS i x a s b k s t o s w o k k i k s j .m upper lobe, b eh in d . a n d over b o th u p p er lobes in fro m . H tv a th so u n d s a re ra th e r ur.ik. w ith p ro lo n g ed ex p iratio n . S oat- >-`iv .j v a r i a b l e r h o n e h i an i r a le s a r e h e a r d f i v r tie* rig h t h im :, b e h in d . o v e r th e le ft r lo b e in tr<fit a m i o v e r th e le ft r o o t. Tin s k i a g r a m s h o w e d a d e f in i te d if fu s e plus tu h ereu lo sis. S putum w as iie g at iv e Mne e x a m i n a t i o n . Tin* d ia g n o s is wa* d u s i iib m > is in t h e a d v a m v d s ta g e . w ith \ n? .ereuioM r, p r o l .a h l y aetiv*. C am: 14.--T hi s worker, a male, aged d'd commenced work in an a>oestos plant in 1*i*. 1oit wa* employ"! m otiier work imril Ja nu ary , 1**14 ' During lie- n*\t rw until rarlv in lUP*. ubut thr*** w a r s :*.i:d !:!' mouth w on* spent in a rm y s*rv- *. , i *r it in* m o f if :.'. <<:' uhi<*L h e w a* a p r i '- r war. **ut j.- had two 'her* p*rmU' w*rf\ iti i*iev*n m o n t h ' iti fin* .avi:.g. a m i m \ m o n t h ' in th* m u t t r " . ;< :iru n e iit'. ! r-m e a r ly iti to \ > v* jn i r. l'.rJ7. la* w o r k e d in a'beM * p r - - i o u t f u r m ils m \ v * a f 'a n d t*n m o n f hs in a d u s ty me m i a t m - s m ar.im t . ib* th e n w rk. lb* w a** i r i **r i *d i * a t urn r*a- ]'}' di'lHUJM irV uli <>et. It*. Wfieri h e gave a h is to r y oj hrm -hiti.- in half a n d I'M? d u rin g th e W ar. an d of n e w r being v ery w ell >itic*e; c o m p l a i n i n g o f d y s p n e a , p a i n in th e rig h t sil`. a n d a s l i g h t r o u g h o f o n ly a b o u t six m o n th s ' d u r a tio n , w ith a sm a ll a m o u n t of g ray ish sp u tu m . D r. X . T a tte rsa U state* th at at th a t tim e; " D yspnoea w as very m arked, even on talking, an d th ere w as definite cyanosis. II- h a d m a r k e d h o llo w in g a n d r e s p i r a t o r y retrac tio n a t b o th ap ire s. specially the r ig h t; oss of n o te o v e r m ost of tint rig h t iung arid tir e u p |> e r h a lf o f tin* le f t ; b r o n c h ia l hreaf h sounds a t b o th apices; fairly nu m er o u s c r e p i t a t i o n . ', rn*.-{Iy <m t h e r i g h t 'id*, and a p leu ral ru b a t th e rig h t base. Me had a > \ 'tlie b r u i t a t t h e ap**x :im l p f.-u ro - l- r ii u rd ia l f r ie tio n . " 1 e x a m in e d h im a n u m b e r of tim e s , tie* -oi*t <M-a't'*n b e i n g A p ril _,,h H2s. I n t h a t ' >m- h* ii.'d b>M ! p o u n d ', fe ll V erv w e a k . . : t; 1 '!i* d >p 1*11'.i Wa . I ; ' a - 1!: g ] h -. ; i I 111i*11 ` h i **f. t i c - g !. .- . <! :V ' *t J. :. - !I:C ' - < th e s p u tu m hal re m a in e d sm a l l iti a n m u i . r . a n d i t s a p p e a r a n c e d id m-: ugg t : u ; " M y d ia g n o s is f r o m tin- brgimdnu w.;' o n e o f p u l n e m a r y u s h r M . - M ' w it h m>'M hT. added tubercle. "1 to o k tw o X - r a y s id h i m . m v !e ; w h i c h s h o w e d appe ar an- *- ' ' U g g Miv tubercle, evervtliing pointing t>- a \ *. extnu nr drgrr*- *f iibr.-|~ H` died of1 *>(1. h`>. PCs \ , : .. . examination was obtain-.*. 1'iG. o . --C a s e 14: Ma->iv* l.duo, with p le u ra l th ic k e n in g . rvtracd n p ev -.'. am i p n e u m o t h o r a x o n l e f t si!* w i t h n e o m p b t* collapse of lung. It will be n o ted tha* th e length of \pi. s u r e t asb * sto s d u s t is unlik*ly t i i a v e been m ore t h a n ab o u t ten y ea rs arid tw m o ii ih s , a n d o f t h i s t i m e | M* vva- i*mp; ! o n ly a b o u t eight a n d "!e*-hall y e a rs in a d u s t y prMV><. W a r servi*e. o f o h i n -. m y have reduerd his n*>istaliee. d'he skiagram 1 1*ig. a ' h o w s a m a s s i v e f i b r o s i s w i t h ]>l*ur:d thi ' -ki - ni t i g. r*tra*tei aiH'Xi-s, a t i d pri'' i m o - *!. :us -.I-. li ft ' i1* '' itli inciinph-T` =i- . it f' 'll'- t Ij I>U- i : -t i i l u *-. - * f i 1,.- : \ \ .. : 222 THE JOURNAL OF INDUSTRIAL HYGIENE finally to a fatal termination, even in the absence of a superadded tubercu lous infection. rFhe primary effect of the fibrosis would appear to be that of causing defective aeration of the blood, result ing in an added strain on the heart. For many years, and even with an advanced degree of fibrosis this may be of little inconvenience, provided physical exertion is limited, and acute illnesses arc avoided. Ultimately, however, the margin of safety, already diminished, is lost anti the circulation slowly fails, with the usual signs of edema of the lungs. More often, however, an attack of bronchopneu monia. influenza, or other acute infec tion adds too much to the strain, im pairs the cardiac musculature, ami results in a fatal termination. (To lo' fioict u-h'T BOOK REVIEWS Ui.KiVKiuucTVxo. Hy Prof. Dr. Paul Srhmiili, Dirvktor tics Hygicnischcn Instituts <1i t I'nivcrsitat Halle a. d. S.; l'riv.-Doz. Dr. Atlolf S, ix, r. Oberassist>nt am Hygieni.sciien lnstitut Hallo a it. S.; mul Priv.-Doz. Dr. Stillfried .Wi-itcnt an dor Modi/.inisohon Klinik Hallo a. d. S. Pa[HT. Pp. 79 with indox. illustrations, and bibliogra phy. Berlin and Vienna: Urban A: Schwarzonborg, 1930. This monograph is divided into a short introductory or general section and a special section. The first part is devoted principally to a discussion of the outstanding diagnostic symp toms of lead poisoning anti of the work done by Dr. Schmidt and his collabora tors in the rnicroehomical determina tion of lead in blood, urine, and feces. The second part discusses in detail the usual sources of lead poisoning; the absorption, distribution, and excretion of lead; the pathology and clinical find ings associated with lead poisoning; and, finally, the diagnosis, prophylaxis, and therapeutic treatment of lead poi soning. Dr. Schmidt's monograph is particu larly apposite. It brings the literature of the subject down to the present dale and represents the mature thought of an investigator who has long m ade 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 attem pt 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 29S references to the recent work ami brings the literature of the subject down to 1930, is particularly valuable. " Bleivcrgiftung" may well be recom mended as a valuable addition to the library of students of public health.-L. T. Fairhall. * VOLIMK pr: culties ei the penaccident exceeding sense, or. psycholog I a stringci gration. dent, as I sarily fort of the cot; ous psych tions; anti object th* complex n tal in its throw ligl life as a ' tion is on himsflt ><' reacts i-iti t I - THE JOURNAL OF INDUSTRIAL HYGIENE Volume X I I JUNE, 1930 N umber 6 PERSONAL QUALITIES INX ^ I D E N 't 'CAUSATION* E. G. Chambers, M.A. Investigator for tke Industrial Health Researck Board, Lui.d-m THE main purpose of this article or by avoiding one. If we can find out $ is to give some account of the why some people react in the one way practical and theoretical diffi and some in the other, we shall have culties encountered in a research into learned a good deal about the nature the personal qualities involved1 in of the reactions of mind to its environ accident causation. This problem is ment. exceedingly important and is, in a About the practical importance of sense, one of the main problems of this problem to industry there can be psychology since its solution demands little doubt. The cost of accidents is a stringent research into mental inte enormous not only in actual money gration. The occurrence of an acci but also in loss of time and efficiency. dent, as I shall show later, is not neces It is difficult to gauge the full extent of sarily fortuitous but is often the result this latter lo3s, but the financial cost of of the complicated interaction of vari accidents, as represented by the annual ous psychologic and physiologic func expenditure in insurance premiums, tions; and a research which has as its runs into hundreds of thousands of object the disentanglement of such pounds. This insurance, of course, complex mental situations (using men only covers cases where compensation tal in its widest sense) is bound to has to be paid, and -compensated acci throw light on the nature of mental dents are actually only 1 or 2 per cent, life as a whole. The accident situa of the total number of industrial tion is one in which everybody finds accidents. himself sooner or later, and to wh.ch he An accident is commonly regarded reacts either by incurring an a w i - n t as being dii*' to chance: that h, as an H- .'-iv.- t f,, r | . U c M l i - . l ; \ t i w n t tie.- entiM-s of which an- lo.tertul J i 23S TH E JOURNAL OF INDUSTRIAL H Y G IENE tioned for conjugal tuberculosis is an "average" figure, and therefore sub ject to the usual fallacies of averages. There is, for example, little doubt that the incidence rate among young mar ried couples is higher than 5.G per cent., and that in middle age it is lower. There are many other factors to be considered, as well as the ages of the infectious and the noninfected spouse. Child bearing, lactation, housing, nutrition, educational and social condition, all have their influ ence. B ut when, eventually, all the factors which determine the incidence of conjugal tuberculosis come to be included in one comprehensive equa tion, we must not be surprised to find th a t the variable for "silicosis" has dropped out. Meanwhile, facts are needed. It is in the power of the Tuberculosis Offi cers working in silicotic areas to pile up these facts, little by little, from the families of silicotic patients who come under their observation. a Pi kind desc posti caseing p Th as soi many ashes pulmc basal tensiv out tf come i the be the cl. struct geneoi appea- cartila esses-- obliter the mi. and m absccs The f from t irregul. of the centra tient h (follov areas i. sharp!.' acti'r . feat lie Diet i I THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS (Concluded) E . R. A. Merewether, M.D. S . i t . Medical Inspector of Factories Morbid Axatosit The totally fibrosed areas of lung show grayish-black mottling, owing to immobili Professor M. J. Stewart of Leeds has kindly supplied me with a detailed description (dated March 2S, 1929) of postmortem appearances of several zation of carbon. This tissue is excessively dense and completely airless; but there is no evidence of calcification. Other por tions of lung show varying grades of the same process, and even the least affected cases. - From this account the follow parts are definitely tougher than normal. ing points are extracted: In none of the eases was there any evidence of an active tuberculous lesion. Tiis gross morbid anatomy of this lesion, as seen in persons who have been at work for H istology many years in tho dusty atmosphere of an asbestos factory, consists in a widespread pulmonary fibrosis affecting especially the basaL region of both lungs. There are ex tensive, densely fibrous adhesions through out the pleural sacs, which may, indeed, be The essential lesion is a chronic interstitial fibrosis of the lung. In the earlier stages, there is fibroblastic proliferation in the alveolar walls, which become increasingly thickened come completely obliterated. In particular, the bases of the lungs are firmly adherent to the - diaphragm, and between these two structures there is often a thick, homo geneous layer of fibrous tissue, similar in appearance and consistence to yellow fibro- in consequence; and there is catarrhal desquamation of the alveolar epithe lium. At thisstageofthediseasepeculiar golden-yellow "asbestosis bodies" are found in varying, usually con cartilage. As a result of these two proc esses--pulmonary fibrosis and pleural sac obliteration--bronchiectasis develops in the midst of the more grossly diseased tissue and may go on to the formation of multiple abscesses with smooth walls. siderable numbers, both in the alveolar spaces and in the thickness of their walls. Detached portions of bodies `may often be seen engulfed by alveolar phagocytes, or a large unbroken body The distribution of the fibrosis, apart from the extensive basal lesions, is rather irregular, the peripheral, subplcural regions of tho lungs being more affected than the central areas. In one case in which the pa tient had been away from work for four years may be partially surrounded by these cells. In the more advanced stages of the disease, the fibrosis of the lung is complete. Alveoli can no longer be made out; but the asbestosis bodies (following nineteen years in tho mill), tho areas of dense fibrosis were extraordinarily sharply circumscribed. The nodular char acter of the lesion which is so striking a feature of silicosis in its earlier stages is not met with in this disease. still remain embedded in the fibrous jtissue. Varying quantities of carbon are also present, chiefly in little masses as though it had been contained with in phagocytes. Chronic bronchitic 239 Vol. 12 No. t 0i j 46 240 THE JOURNAL OF INDUSTRIAL HYGIENE changes are present and ail grades of bronchiectasis may be seen, in cases of longstanding, from simply bronchial and bronchiolar dilatation, with walls still more or less intact, to large spaces filled with pus in which the original bronchial walls have become converted more or less completely into fibrous and granulation tissue. Many of the smaller arteries show obliterative end arteritis. Reversionary metamorphosis of alveolar epithelium is frequent, and such alveoli are often filled with albuminous fluid, in which clumps of "bodies" may be found. Asbestos D ost in tee Lungs Dr. W. E. Cooke has supplied (under date of June 25, 1929) details of his researches on asbestos dust in the lungs, and on the constitution of the curious bodies, which have been freely used in the followingnotes:-- Sections of lung and the results of digestion of the lung with trypsin show an enormous amount of fine black granular dust, much of which is carbonaceous. In addition, there are two striking features. The first is the almost complete absence of the fine translucent spicules of fiber which make up a great proportion of asbestos dust in factories. The second feature is the presence of large fragments vary ing in length from 10 to 360 microns. They are found in fibrotic and necrotic areas, singly and in groups. The particles are so large--masses of them are seen in some sections--that they must have occluded small bronchi and resulted in fibrosis of the surrounding area. Comparing these large particles in tho lung with those found in asbestos / dust, close resemblance in sizes, shapes, and colors is apparent. There arc the same black, blue, brown, and trans lucent fragments. In fact it is easy to take such a single particle from the lung and immediately find its brother in a slide made from the dust. Curious Bodies In addition to the fine granular dust and larger fragments of asbestos, sec tions of the lungs show curious bodies. They are found in alveoli, bronchioles, fibrous and necrotic areas, and in phagocytes in sections of both lungs. If a portion of lung is teased and extracted with water, or digested with trypsin, or, as Professor Stewart pointed out (192S), if a smear is made from the cut surface of the fresh lung, these bodies are seen in myriads. The larger bodies measure from 20 to 100 microns or more in length, and are of a golden-brown color. They may have single clubbed ends or may appear as elongated dumb-bells; some are filamentous, while others suggest a series of disks. Single coccal and spore-like forms, and aggregations of these, and strepto coccal forms are not uncommon; the color varies in the smaller types from a very pale yellow to a yellowish-brown. The bodies do not stain with any of the aniline dyes, but in chrysotile workers, they give the Prussian blue reaction for iron in varying degrees of intensity. These curious bodies have been found in every autopsy in pulmonary asbestosis. It would -be unprofitable to retrace all the steps which led down many by-lancs during the course of the work, but I will mention a few per tinent details of interest. Professor Stewart suggested to me J..H . jun*. mo 0i47 PULMONARY FIBROSIS IN ASBESTOS WORKERS 241 that a better method than simple extraction of the lungs with water or saline would bo to digest portions with trypsin. During this process it was found that if the specific gravity wa3 kept at about 1,070, the black dust and larger fragments of asbestos, as well as the partially digested lung tissue, sank to the bottom of the tube. By decanting the apparently clear supernatant liquid, and by centrifugal* izing, neutralizing, and washing the deposit, the curious bodies could be obtained in a pure state. This was done, and sufficient material for X* ray examination was obtained. The bodies were attached to a hair with gum and subjected to a seven-hour exposure by Professor Bragg's method. If the bodies were mineral, the X-ray film would have shown a definite translatable atomic pattern. The films, however, did not do so, and we were then able to exclude the sugges tion that the bodies were altered asbestos fiber. The result definitely pointed to the greater proportion of their composition being of nonmineral origin. The bulk of the curious bodies is soluble in strong acids and alkalies, and if the solution is observed under dark ground illumination, their bases are seen as extremely fine spicules some of which by transmitted light would probably be invisible. Under a dis secting microscope it is possible par tially to fracture the larger bodies and to show a central fine core. The greater portion of asbestos dust consists of slender translucent fibers. In sections and extracts of the lungs there is a remarkable paucity of these fine spicules. The end-results of diges tion show the fine granular dust and the large black, blue, and brown par ticles and what appear to be pieces of quartz. Relatively few fine spicules are found; but curious bodies of all descriptions arc present in enormous numbers. All these facts lead us to imagine the bodies to consist of a central nucleus of asbestos spicules, upon which colloidal aggregate of blood proteins plus, possibly, soluble frac tions of asbestos and, in the case of chrysotile workers, an iron salt have been adsorbed and molded by currents in the bronchi and the alveoli. The method of formation would appear to be as follows: The fine spicules of asbestos cause, by mechan ical action on the bronchioles and alveoli, either minute extravasations of whole blood, or serous exudates which envelop them. Solution of any soluble fraction of asbestos takes place. The total amount of asbestos that is soluble must be extremely small, as is proved by the X-ray pattern of the curious bodies, but in the case of chrysotile workers some solution is suggested by the free iron reaction. We must remember, how ever, that the Prussian blue reaction may be due to the iron of the hemo globin. Any surface in contact with a colloidal solution may act as an adsorbent, and in the present case the fine spicules must be considered to do so. Interaction between the soluble fraction of chrysotile and plasma proteins takes piace, syneresis occurs, and, with the loss of water, the adsorp tion is rendered irreversible. The adsorbent is permanently enshcathed with stable colloidal aggregates which become molded into the familiar Val No. t ! i I j i I 242 THE JOURNAL OF INDUSTRIAL HYGIENE shapes by alveolar and bronchial cur rents. Support for this idea is found in the fact that micro-organisms adsorb col loidal material in the presence of blood serum and colloidal asbestos. Staphy lococci so treated appear os large round yellowish-brown disks; in the process their property of staining with aniline dyes is lost. The organisms coalesce and form masses; and I think it probable that some of the coccal and spore forms are similar organisms. finally, are the curious bodies diagnostic of pulmonary asbestosis? Asbestos is unique among minerals in being brous; and its dust, generated during manufacturing processes, is also unique. As can be imagined from the formation of the curious bodies, there is no reason why, given any silicosis, afne spicule of mineral should not have colloidal matter deposited around it and become molded into a curious body. But as no other min eral dust is fibrous, this occurrence must be so rare as to be negligible from a diagnostic point of view. The con ditions which, apparently, must obtain for the formation of curious bodies are the presence of plasma proteins and fine spicules soluble only with diffi culty. These conditions are ideally found in asbestos workers; for this reason I believe that curious bodies, if found in any numbers, are pathog nomonic of pulmonary asbestosis.-- W. E. Cooke and also Roodhouse Gloyne (20) have independently dem onstrated the presence of a mineral core, evidently derived from asbestos fibers, in the curious bodies. The bodies havo been found (Stewart and Haddow (21)) in the intrathorncic lymphatic glands; immaterial obtained by lung puncture during life, first sug gested by S. A. Henry; in the sputa; and in smear preparations from the cut surface of the lung. In smear preparations they can be readily demonstrated. The importance of these findings lies in the fact that the bodies have never been found, as yet, in any other human affection. That similar bodies may be found to occur in the lungs of workers exposed to other dusts, is quite possible, although they have not been found in silicosis, nor were they . present, according to Simson (6), in . the fibrosed lungs of a hematite miner. They appear within a comparatively short period of time after exposure to asbestos dust; at the moment, their presence in the sputa, in the absence of clinical or radiologic evidence of pul monary fibrosis, cannot be token as in dicating anything more than previous inhalation of asbestos dust. The pres ence of the bodies, however, in the sputa of persons with signs of a diffuse fibrosis, or their presence in numbers on postmortem examination of a fibrosed lung, has evident implications. Professor Stewart, who is continuing his work on this subject, has devised the following method of examining sputum for asbestosis bodies: Half an ounce or so of sputum is added to an equal quantity of undiluted aneiformin. This is gently agitated until the sputum is completely dissolved, after which it is diluted with 2 or 3 ounces of water and allowed to stand in a large test tube for three or four hours. The bulk of the super natant tluid having then been decanted, the remainder is centrifuged at a moderate speed for ten to fifteen minutes. The whole of the supernatant fluid is now poured off, and the deposit transferred to an albumin- UR. Jus*. 10 PULMONARY FIBROSIS IN ASBESTOS WORKERS 243 feed slide, by means of either a platinum loop or a pipette. After thorough drying on a hot plate and final fixation over a bunsen burner, the film is very gently washed in water, dried, and mounted in Canada bal* sam. After a little experience tho osbestosis bodies are readily picked up with the low power, and their true nature is then eon finned with tho i-inch or oil immersion lens. As a rule they arc present in very small num bers, perhaps only one or two in a wholo film. In the ease of some of the older workers, however, numerous bodies, up to one or two per field in certain portions of the film, have been found. It is obviously necessary to cleanse thoroughly all glass ware, etc., used in making these examine tions; otherwise there is a risk of contami nation of subsequent specimens. The films can be treated with hydro ehlorio acid and ferroeyanide of potash to demonstrate the Prussian blue reaction given by the bodies. Asb e sto sis a x O ccupatioxal H azard Out of a total of 374 workers examined, 105, or 28.1 per cent., were found to be affected with fibrosis of the lungs, in greater or less degree. But when these figures are corrected by the exclu sion of cases in which previous work in dusty occupations (e.g., quarrying, coal mining) may have been the prime, or a contributory, factor in the develop ment of the fibrosis, ninety-five, or 26.2 per cent., of 363 workers were found to be affected with pulmonary fibrosis due to the inbalatiou of asbestos dust, and a further twenty-oue, or 5.8 per cent., showed precursive signs of this disease. This percentage may well be com pared with the corresponding figures found by Middleton (22) in his exami nation of metal grinders (46.9 per cent.) and by Sutherland and Bryson (23) (24) in their examinations of potters (39.9 per cent.) and of sandstone workers (58.1 per cent.). 'The precise significance of the lower figure found in this inquiry is not easy to determine. At first sight it seems to indicate that asbestos dust is less potent os a cause of pulmonary fibrosis than are the dusts containing free silica. Other factors, however--such as the measure of exhaust ventilation, or other means of reducing the concen tration of dust, in the several indus tries; differences in the average length of employment of the comparable groups in the samples examined in the respective inquiries; and the relative numbers employed in the more dusty and the less dusty processes--will affect the crude incidence rates ex pressed by these percentages. From comparison of the amounts of dust evolved--determined visually and by means of dust counts--in dusty asbestos processes, uncontrolled by local exhaust ventilation, with obvi ously defective exhaust ventilation, and with comparatively good exhaust ventilation, there can be no doubt that this preventive measure, which has been applied in some degree for more than seventeen years, has been a posi tive factor in minimizing the produc tion of fibrosis--probably in the direc tion of lengthening the period before the fibrosis becomes fully developed. Consideration given to the distribu tion of the workers examined both according to length of employment, and according to age, together with the incidence rates of fibrosis in each case, indicates the outstanding importance of length of employment (and hence length of exposure to dust), and the negligible effects of age, on the produc tion of fibrosis. Thus age groups 30 to VL It No. f O i S O I 244 TH E JOURNAL OF INDUSTRIAL HYGIENE 39 and SOto 59 have incidence rates of 30 per cent, and 37.9 per cent., respee* tively--not a wide difference, since the groups include workers in various processes exposed to different concen trations of dust. Moreover, the aver age length of employment in these two groups, excluding the cases of fibrosis, fibrosis in age group 20 to 29, has been shortened by increased susceptibility a t ages under 20. As, however, the average age of this group of cases of fibrosis is 20.7 years, and also because the establishment of fibrosis does not necessitate immediate retirement from work, this is largely discounted. TABLE 5.--DISTRIBUTION OF WORKERS EXAMINED WHO HAD BEEN EMPLOYED FOR FIVE YEARS OR OVER, TOGETHER WITH CASES OF FIBROSIS, ACCORDING TO PROCESS IN WHICH WORKER WAS LONGEST EMPLOYED m oexss no. EX AMINES cassa or raaosis No. Per Cent, of Group AVESAGS LEJTOTH OV EMPLOYMENT IS TBS. Group Less Cases of Fibrosis Cases of Fibrosis 1. Crashing, opening, disintegrating, and mixing............. 2. Carding..................................... 3. Spinning, twisting, doubting, plaiting, etc................ 4. Mattress making..................... 5. Weaving and associated proe- eases............. .................... a. Cloth weaving.................... 28 b. Band weaving................... . 21 o. Cloth and band and un- classified weavers............. 14 d. Warpers, bcamers, loom tuners, charge hands, and others associated with weaving................. 25 8. Miscellaneous processes snd remaining unclassified workers................................. 21 9 42.9 39 18 41.0 87 12 13.8 IS 7 46.7 88 40 45.5 21 75.0 4 19.0 4 23.8 11 44.0 24 11 45.8 8.9 9.1 10.1 7.3 10.0 9.5 10.9 7.2 11.2 8.8 10.9 13.2 18.7 13.0 12-7 14.1 13.5 9.5 10.3 13.8 Total............ r ............................ 274 95 34.7 9.8 13.5 is also similar, but considerably less than the average length for all the cases of fibrosis (13.5 years). No special susceptibility to the development of fibrosis is shown by young persons, unless it is considered that the figure of S.7 years, the average length of employment of the cases of The effects of length of employ ment arc such that after five years' exposure, the incidence rate of fibrosis mounts rapidly, and after ten years increases almost in geometric progres sion. Table 5 shows the distribution of 274 workers examined, and of those with fibrosis, according to the process J.I. H. Ju n e, 1030 PULMONARY FIBROSIS IN ASBESTOS WORKERS 245 in which they were longest employed. This was a compromise necessitated by the common customs in the indus try of having several different processes going on in the same room, and of workers transferring from ono process to another. Since the intention was to obtain some measure of the relative incidence of fibrosis in workers in the various processes enumerated, and since no case of fibrosis clearly due to asbestos dust was found among eightynine workers examined, who had been employed for less than five years, in clusion of this group of workers would only have introduced a varying source of error. The processes differ, some very materially, in the amount of dust which they cause, and consequently in the amount inhaled by the operators (30). The outstanding point brought out by Table 5 is the relatively low incidence rate of fibrosis in "spinners" (group 3), as compared with each of the other groups. They are corrobo rated by counts of the dust particles in samples of air, a number of which have been taken and are discussed under Dvst Risk. There is also some indication in these figures that not only are."spinners" less likely to develop fibrosis, but when they do, it takes longer to develop. Study of the radiograms suggests that in such cases (i.i., in the less dusty processes) the resulting fibrosis is, for a considerable period, much more linear in its radiologic features, and shows less mottling. The history and clinical features in those cases, and the com parative dust counts, all contribute to the view that with comparatively low concentrations of dust, the resulting fibrosis is longer in developing and remains longer in the milder, and radiologicaliy linear stage. This view is evidently of consider able practical importance since it sug gests that in such cases, the rate of accumulation of dust in the lung has not greatly exceeded the rate of elim ination, the changes still being centered in the main lymphatic system. If this hypothesis is accurate, it should follow that in order to prevent the full development of the disease, among asbestos workers, within an average working lifetime, it is neces sary to reduce the concentration of dust in the air of the workrooms to a figure somewhat below that pertaining to spinning a t the present time. Fortunately, also, the spinning group is the largest individual group in this section of the industry--e.?., out of over 400 workers employed by one firm, this group accounts for more than one-third. Although all workers examined who have been included as spinners have been engaged in spinning, or in simi lar processes for convenience termed "spinning," for a longer time than on any other process, only a few have been employed solely on spinning, and in workrooms where no other, and more dusty processes, were being carried on. These two factors, prior work in more dusty processes and present work in proximity to more dusty proc esses--especially the latter--have had, it is believed, some effect in raising the incidence rate of fibrosis for this group. Dust Risk In an effort to obtain additional data on the influence of concentration of dust in workrooms, a number of sam ples of air were taken and the dust con- Yol. tl No. $ i 0 id 5 246 THE JOURNAL OF INDUSTRIAL HYGIENE TABLE .-SUM M ARY OF DETERMINATION OF DUST CONTENT OF ATMOSPHERE OF WORKROOMS AND OTHER PLACES * sam ple NO. process and source or SAMPLE LOCAL EXHAUST VENTILATION TO PROCESS OR NOT OTHER PROC ESSES IN SAME ROOM no. or PAR TICLES PER C.C. PERCENT* PERCENT* AGS AGE 2m AND 7.5m and UNDER UNDER 1 . 1/2 Carding; passageway between Yea cards 2. 1/5 Spinning No 3. 1/3 Cloth weaving, dry No 4. 1/7 Opening Yes 5. 1/6 Sieving; shoveling fiber on to No sieve 6 . 1 /8 Plaiting No 7. 1/1 Office 8. 2/11 Office 9 . 2/1 Cloth weaving No 10. 2/14 Spinning No 11. 2 /1 0 Mattress making; filling Yes 12. 2/8 Mattress making; beating, Yea damp 13. 2/7 Mattress making; beating, dry Yes 14. 2/9 Mattress making; after filling Yea 2 mattresses 15. 3/1 Band weaving, wet No 16. 3/4 Opening Yea 17. 3/3 Carding; between cards Yes IS. 3/5 Carding; feeding card Yea 19. 3/2 Office ... 20. 4/1 Mattress making; filling No 2 1 .4 /1 Mattress making; filling No basket 22. 4/3 Emptying settling chamber No 23. 4/4 Same No 2 4.4/5 Insulating sections; leveling No fiber 25. 4/5* Carding; side of dirty card Yea 26. 4/6 Carding; end of clean card Yea 27. 4/7 Carding; feeding card Yea 28. 4/9 Cloth weaving, very slightly No damp 29. 4/10 Cloth weaving, damp No 30. 4/11 Braiding No 31. 4/12 Spinning No 32. 4/13 Office ... 33. 5/1 Band weaving, dry No 34. 6/2 Cloth weaving, dry Yea 35. 6/3 Band weaving, dry Yea 36. 6/9 Opening Yea 37. 6/6 Carding; feeding card Yes Yea 2,139 81.3 95.1 Yes 1,456 * 95.9 100.0 Yes 1,756 84.1 96.7 Yea 2,384 80.9 93.7 Yes 2,829 83.0 97.6 No 1,687 99.0 99.0 901 98.8 100.0 1,480 98.7 100.0 Yea 1,788 88.9 98.6 Yea 1,073 96.2 100.0 No 985 92.5 98.1 No 970 8S.9 95.8 No 1,629 86.9 96.6 No 1,204 96.6 99.4 No 80S No 2,313 Yea 1,528 Yea 1,321 ... 1,049 Yes 1,858 Yes 1,390 96.6 77.7 82.5 82.9 96.3 60.1 .... 100.0 96.6 97.4 96.4 1C0.0 90.1 Yes 3,401 Yes 4,711 Yes 1,838 .... .... .... No 1,402.' No 1,092 No 1,689 Yea 3,033 .... Yea 758 _ Yes 506 _ Yea 954 _ ... 689 Yes 2,202 No 885 No 701 Yes 643 Yes 562 .... i . I. H. )M. 1(30 0io5 o \ ] PULMONARY FIBROSIS IN ASBESTOS WORKERS 247 TABLE 6.--Continued SAMPLE NO. process a nd source o r SAMPLE local exhaust VENTILA TION TO PROCESS OB NOT OTHER PJIOC. ESSES IN SAUS ROOM no. o r PAR TICLES PER C.C. PERCENT PERCENT AGE AGE 2a ano 7.5a and UNDER UNDER 38. 6/4 39. 6/5 Carding; center of room Carding; grinding rollers Yea Yes Yea Yes 620 540 .... 40. 6/7 41. 6/8 Spinning Oilice . No Yea 620 eoo 666 e e 42. 7/2 Cloth weaving, dry Yes Yes 4,683 a e. 43. 7/1 Opening; shoveling fiber into Yes Yes 4,880 .... 44. 7/3 45. 7/4 46. 7/3 47. 7/6 box Opening Band weaving, wet Spinning Carding; between cards Yes Yea 6,324 .... No Yea 5,353 .... No Yea 6,044 .... Yea Yea 4,607 .... 48. 7/7 Office 3,413 ... 49. 8/2 Cloth weaving, dry No Yea 1,287 88.6 94.9 50. 8/3 Band weaving, dry No Yea 1,233 73.2 93.7 51. 8/5 Carding Yes Yea 1,193 67.2 94.9 tent was determined by means of Owens' jet apparatus. Here also the. undetermined effect of dust from neighboring processes must be noted. Nevertheless some information of prac tical value was obtained. Reference to Tabic 6 shows that the counts ranged from 506 to 6,324 particles per cubic centimeter in the air of workrooms, and from 666 to 3,413 per cubic centimeter in the air of offices associated with the factories. In some cases there was a smaller count in a workroom than in an office of the same factory; this was due either ta there beingmuch fewersmoke particles in the air of the workroom, or to adher ence of the smoke particles to the inorganic dust in the workroom. The character of the dust in the two cases is, however, entirely different. In the air of the office almost all the particles arc black, or brownish, and amorphous, evidently smoke; in the air of the workroom, the majority of the particles are, just as clearly, crystalline particles of asbestos, to gether with, frequently, some cotton fibers and numbers of black and brown ish particles, some adherent to asbestos spicules and some free. Most of the latter are iron containing and are derived from the asbestos, and there are relatively few smoke particles. Iso lated golden-brown scales or plaques, also derived from the asbestos, are scattered about the field. The asbestos fiber first fragments longitudinally, and apparently this process can go on indefinitely, since there is no ultimate fiber comparable to a vegetable fiber such as cotton. The dust collected in the Owens appa ratus contains numbers of these very fine fibers--some about 0.5 micron in transverse diameter, many less--which have fragmented transversely. Thus spicules of very diverse length--up to Vol Me. 4 0a o5 248 THE JOURNAL OF INDUSTRIAL HYGIENE about SO microns--but about 0.5 micron broad, arc found jn numbers on the sample, together with the black, brownish, and yellow particles already mentioned. The great majority of the spicules are found broken down into particles of the order of 2 microns and less, many being about 0.5 micron and more or less rounded. The proportion of elongated to rounded particles seems to vary in the different processes; for example, a greater proportion of elon gated particles is found in the air near dry cloth weaving than near a spinning frame. Weaving damp reduces the proportion of elongated particles. This variety of microscopic spicules, particles, and frequently some cotton fibers, found in the samples of dust col lected in the Owens apparatus, results in a tendencyto clumping on the cover dip, making counting, especially of the higher concentrations, a matter of extreme difficulty. Occasionally, also, part of the slot of the apparatus choked up with dust. The effect of the clump ing is to reduce the counts of all except the low concentrations. Furthermore, this apparatus is much influenced by local air eddies and cur rents. It takes a grab sample, which is accurate enough as an indicator of the local conditions at the moment of sampling, but does not give a picture of the average state of the atmosphere during a period of time, as does a gravimetric apparatus. Moreover, with high concentrations of dust, accurate counting becomes impossible. The apparatus has, however, many advantages, including those of con venience, quickness in operation, and direct examination of the nature of the dust. By serial observations, too, temporary and local large increases in the dust content of*the atmosphere-- such as that produced by shoveling asbestos fiber into a sack--can be detected and estimated. This is of great importance since short, but repeated, exposure to massive concen trations of dust is agreed to be very harmful. Counts Nos. 5, 22, 23. and 43 in Table 6 are examples. Much useful work can be done by means of serial dust counts in various dusty processes in the same factory, and by comparison of the results. The counts set out in Table 6 ore derived from eight different factories,. and it is a matter of interest to con sider whether counts from different factories con be directly compared with one another. Strictly they cannot, since the content of smoke particles varies in each group. The difficulty might be obviated by counting only the particles derived from asbestos. The method has been applied success fully to counts of crystalline silica dusts; but it is not so easily applicable to counts of asbestos dust, which con tains numbers of black and brownish iron containing particles, many of which are not quickly distinguishable from smoke and tarry particies. To classify the processes accurately on the basis of amount of dust evolved, it is necessary to take serial samples at intervals corresponding to the details and complexity of the processes. With some straightforward processes, such as spinning, few samples will be necessary; but in others, such as mat tress making, mixing, grading and opening--especially with old-fashioned plant--in which the evolution of dust rises and falls rapidly in a compara tively short space of time, many more observations are necessary throughout j.i.n. Jun*. IMO OJLOSS \ 4 t ; ; i I j > J 1 iI i PULMONARY FIBROSIS IN ASBESTOS WORKERS 249 a shift, to determine the average con centration of dust. Repeated controls are also required. Comparative data show that the dustiest processes arc opening (with old-fashioned teasers), sieving (with no local exhaust ventilation), and shoveling, or otherwise handling asbes tos fiber. The heaviest counts of all werefound in this group, in fillingsacks, by hand, with disintegrated fiber in a settling chamber. The visual cloud of dust was intense, and irritating enough to provoke immediate coughing on the part of the observer. The clumping of the dust particles of the sample on the cover slip was very marked, with the result that the total dust count arrived at was undoubtedly too low. With counts of asbestos particles of this order, however, the precise count is of little practical importance, since the dust concentration is far beyond the safe limit. Next in order is cloth weaving, dry and without the application of local exhaust. This is undoubtedly a dusty process, and although local exhaust reduces the count at the breathing level of the weaver, much dust still escapes into the workroom. Furthcr counts are necessary to estimate this. Weaving cloth wet, not merely damp, reduces the dust count to a remarkable degree. The figure for band (t.e., narrow) weaving, wet, is not accurate since it was raised by dust from a neighboring dry cloth loom; still the improvement due to wet methods is noticeable. One asbestos weaver, who was formerly a cotton weaver, and who has to wear glasses, stated that whereas he used to clean his glasses about three times a day when cotton weaving, he has to dean them about five times a day when asbestos tape weaving dry, and only once a day when weaving asbestos wet. Next in order comes mattress making, without any precautions such as ex haust ventilation, or damping floors, cloth, and tables. Application of ex haust ventilation and damping reduce the count considerably, but it is be lieved that the figures arc too low, since counts for some subsidiary processes such as buttoning, sewing, and cutting out are not available. The figures for spinning, plaiting, and braiding are believed to be rather too high, owing to contamination of dust from neighboring and more dusty processes, and further investigation is required here. A number of the samples taken with the Owens apparatus were examined to determine the size of the particles, and the percentages of particles -2 microns and under, and 7.5 microns and under, were ascertained. The 2micron standard was retained for purposes of comparison, and because of its accepted importance in silicosis. The 7.5-micron figure was also adopted because of the pronounced acicular character of much of the asbestos dust, and because, representing the diameter of the human red blood corpuscle, it is a standard easily distinguishable, and may conceivably represent the limit size of particles which can be con veniently engulfed by phagocytic cells, which are somewhat larger. Among twenty counts from various processes (Table 6), in two, between 60 and 70 per cent, of the particles were of sizes 2 microns and under: in two, 70 to SO per cent.; in ten, SO to 90 per cent.; and in sue, 90 per cent, and upward. When the counts were analyzed ac- Veltt No. 0 kd5C ! / 250 THE JOURNAL OF INDUSTRIAL HYGIENE cording to the 7.5-micron standard, all tw enty showed 90 per cent, or more of th e particles to be of this size or less. W ith regard to the effect on the longs of different varieties of asbestos, no evidence was found to indicate th a t an y one of its varieties is more potent in producing fibrosis than the others, other factors, such as concentration of dust, being equal. There is now no doubt, however, th a t both chrysotile and crocidolite will produce fibrosis; while th e third, th e comparatively newly discovered amosite, resembles crocidolite so closely in its chemical constitution, and in the characteristics of the dust, th at there can be no reasonable doubt, also, w ith respect to it. Length o f D ust E xposure N o case of diffuse fibrosis clearly due to asbestos was discovered w ith under 5 years' employment. Three cases were found w ith 3, 3$, and 4$ years' work, respectively, who showed clinical signs of fibrosis. Definite confirmatory radiologic evidence was obtained in the first, definite but slighter radiologic changes in the sec ond, and indefinite suggestive changes in the third. The previous occupation in th e first case was flax weaving for 18 years; in the second, coal hewing for 16 years; and in th e third, work in an iron foundry for 1 year. All these occupations are dusty; and in the last two there m ay bo some exposuro to free silica. Also increased silica con ten t has been found in the lungs, after incineration, of (lax dressers. For these reasons, these three cases could not be certainly ascribed to asbestos dust, although it was, probably, at least a contributory factor. Among the cases of fibrosis foqnd, thirty-six had been employed in asbestos for periods ranging from 5 to 10 years; two of these cases, one employed for 9 years and the other for 7 years, show th a t a considerable degree of fibrosis m ay occur w ith less th a n 10 years' exposure. F. W . Simson (6) examined the lungs of a guinea-pig which had been experi mentally dusted by M avrogordato for two hours a day on each of fifty days between F ebruary an d April, 1925, and which died from other causes in December, 1927. H e sta te s th a t his tologic sections showed a slight gen eralized fibrosis: This observer also examined portions of the lungs of two native asbestos mill workers; one had been employed for twelve m onths and had died from a miliary tuberculosis, and the other, employed for two years, had apparently never recovered from an attack oi lobar pneumonia a year before death. In commenting on the am ount of fibrosis found, he states th a t "a com parison between the human cases and the experimental animal showed that the fibrosis was more rapid and exten sive in the human cases than in the experimental animal," and, again, th at " the am ount of fibrosis in two of the human cases . . . . was quite definite, and. if due to the presence of asbestos dust, the initial rate of pro duction was rapid when compared with present-day non-infective silicosis on the Rand." Experiments by Professor Beattie, in 1912. demonstrated that the lungs of guinea-pigs exposed to asbestos dust for forty-three and sixty-seven hours showed "definite cellular proliferation, though not very extensi ve, and this is I. a . Jan#, 1930 Q1C57 PULMONARY FIBROSIS IN ASBESTOS WORKERS 251 certainly a preliminary stage in the production of fibrosis." These pathologic and experimental findings suggest th a t the inhalation of asbestos dust rapidly causes some changes in the lungs. But no evidence was obtained th at asbestos dust can produce an acute type of fibrosis com parable to th at formerly noted in South Africa after repeated exposure to massive concentration of free silica, a few cases of which have occurred recently in G reat Britain, causing death in from two to four years. The amount of disablement pro duced by the development of pulmo nary fibrosis in these workers is surpris ingly slight for a number of years, even more so than is generally the case in silicosis. T he n atu re of th e work, however, in the m ajority of the proc esses does not involve much physical exertion--in fact, in this respect it is "light work." The affected person may, and often does, continue a t work --with occasional intermissions, la t terly, due to exacerbations of bron chitis--until th e condition is advanced, although he suffers increasing incon venience from shortness of breath on the slightest exertion. Usually these cases cease work a year or more before death, but sometimes a terminal bronchopneumonia, or other acute infection, commences while, they are still a t work, and there is no long period of invalidism. Falalilies Particulars of eight deaths have been collected, and arc summarized in Table 7. In six of these, advanced pulmonary fibrosis was the prim ary cause of death. In the remaining two cases, pulm onary tuberculosis was a contributory factor. In six of the eight cases the diagnosis was verified by postmortem examination; in the other two cases, confirmatory radiographic evidence was obtained. Information has recently been ob tained in regard to three other cases, In which d eath occurred in 1929. T he details of one have been published by Wood and Page (25). Postmortem examinations have been made in all three cases, and in ail, the presence of pulmonary asbestosis, w ithout tuber culosis, was verified. In one case, the pulm onary fibrosis was the prim ary cause of death; in one, information os to the extent of the fibrosis has not yet been obtained; and in the third case, a lobar pneumonia was superimposed on th e fibrosis. It is not suggested that these few fatalities, in which the cause of death has been verified by strict inquiry, are any criterion of the true effect of the disease on the mortality rates of asbestos workers. Others are known to have occurred in which the exist ence of the asbestos fibrosis has been determined in life, but no postmortem examination has been possible. Difficulties in Diagnosis M any factors have contributed to impede both the recognition of indi vidual cases of this disease, and the establishment of asbestos dust os the determining cause. These factors are consequent, partly on the nature of the disease, partly on the nature of the dust, and partly on the industry itself, its rapid growth and internal condi tions. Difficulties in diagnosing the disease, its points of resemblance, in its latest stages, to fibroid tuberculosis, and the liability of those affected to be Vol 11 No. ( 0 id 58 7 i / THE JOURNAL OF INDUSTRIAL HYGIENE T A B L E 7.--PARTICULARS OP FATAL CASES tOol to NO. t CASE DATS o r D E A T H *1 SEX aos THE. EM * PLOYED m a in p r o c e s s CONDITION o r M INO S POST MORTEM EXAM I N A T IO N IN QUEST REM ARKS 1 . M ontague 6/13/1000 M 34 14 C ard room 10 yra. Advanced pulm onary Yes No M urray fibrosis; no tuber- CM 8 2 . Cooke's case 3/11/24 F 33 18* Spinner la tte rly culosis Extensivo pulmonary Ves No Exposed to dust fibrosis and tuberculosis from othar proocaaes. 3. If. S. 1027 F 48 24* M attress m aker Pulm onary fibrosis No No Two radiograms con- and tuberculosis firm diagnosis of imlmonary fibrosis. 4. M. 8. 3 / 7/27 F 34 20+ M attress maker Chronic pulmonary Yes No fibrosis; no tuber- culosis S. Grieve* 3/24/28 M 34 13* M attress beater Advanced pulmonary Yes Yes case (W. fibrosis; terminal L.) o b ro nchopneum onia; no tuberculosis H* 6. M. M. 8/25/28 F 34 18-16 M attress m aker Advanced pulmonary Yes Yea Worked for less than C- fibrosis; no tidier- the period staled, CJ culosis as a mattress maker. 7. J. C. 10/13/28 M 38 18 Weaving 1 y r.j m at- Advanced pulmonary No trees dept. 7 yrs. fibrosis; no tuber- No Two radiograms confirm diagnosis. v 8. L. II. and 2 moa. 2/ -/20 F 41 10 M attress m aker culosis Advanced pulmonary Yes Ves fibrosis; no tuber- 1 culosis L. Arrangement of d ates follows th e American custom --i.e., month, d ay of inontli, year, i ?5 * E stim ated. L mi. PULMONARY FIBROSIS IN ASBESTOS WORKERS 253 carried off by some intercurrcnfc dis ease--which alone is noted on the death certificate--are ail of importance. A concrete example encountered during the inquiry will illustrate one of these points. J. C., Cose No. 7 in Table 7, was known by his own doctor and by the Chief TuberculosisOfficer of the town to be affected with advanced fibrosis of the lungs. Four or fire months before his death it was thought that a change of air would be of advantage to him. Through the gen erosity of the firm with which he had been employed, he was transferred from the town to a farm in the country, where he died. The death certificate, given locally, stated that pulmonary tuberculosis was the cause of death. In another case chronic bronchitis was given as the cause of death. . In the less advanced stages of the. disease, the symptoms are so unob trusive that the worker rarely consults his doctor. In the later stages, bron chitis, or the supervention of acute bronchopneumonia, pulmonary tuber* culosis, or other acute infection, all so much more common, masks the under lying fibrosis; and the terminal condi tion is noted as the cause of death. In the second place, the silicate dusts --of which asbestos dust is one--repre senting silica in the combined form as opposed to free silica, have naturally been overshadowed by the silica dusts, since they do not produce the picture of silicosis and have not been shown to be associated with an increased mor tality from pulmonary tuberculosis. Moreover, although the asbestos in dustry has very rapidly expanded, it is still comparatively small, and scattered over the country. A large proportion of the workers have been employed in asbestos only for comparatively short periods, and of the processes considered so far, the less dusty spinning group is at the samo time the largest. Thus only now the existence of a health risk in tho industry is beginning to be recognized. Docs Asbestos Dust Predis pose to Other P ulmoxaby Diseases? The important question as to whether asbestos workers show on in creased liability to other diseases of the lungs, such as pneumonia, pleurisy, and pulmonary tuberculosis--espec ially the latter--requires further in vestigation. A history of pleurisy was given by ten workers, in eight since commencing work in asbestos; in addition, one worker had a slight pleural effusion at the time of examination, and one showed signs of old pleurisy, but no history was obtainable. Of the two with attacks prior to work in asbestos, one had normal lungs, and the other showed signs of a bronchiectasis. Of the eight giving histories of pleurisy, three showed signs of fibrosis, four showed signs of the old pleurisy only (one being due to a gunshot wound during the Wax), and the eighth showed signs of an old inactive tuber culous lesion of the right upper lobe. A history of pneumonia was ob tained in sixteen workers--in ten prior to commencing work in asbestos, and in six since. Of these six, two showed signs of a thickened pleura only, one showed merely enlarged lung roots, two had diffuse fibrosis, and in one the lungs were normal. Of the remaining ten, one had a thickened pleura, two bronchiectasis, two diffuse fibrosis, one Vol. 12 No. 4 254 THE JOURNAL OF INDUSTRIAL HYGIENE commencing fibrosis, and in four the lungs were normal. With regard to evidence of bron chitis, and bronchial and pulmonary catarrh, fifty-eight of the 363 workers (16 per cent.) showed signs of one or other of these conditions, all being quite mild. Of these, thirty-one also showed signs of diffuse fibrosis, repre senting 32.6 per cent, of the fibrotic group, and eight were in the prefibrotic stage (3S.1 per cent, of that group). The fact that the clinical examinations were conducted during the warmer months of the year, no doubt operated to reduce the incidence of these com plaints. Under the circumstances, the preponderance among the cases of fibrosis is the more noteworthy, as in dicating persistent irritation resulting from the dust. Of other diseases, eight gave his tories of rheumatic fever, and of these, two had definite valvular disease of the heart. In addition, valvular disease of the heart was noted in one worker, but no history of rheumatic fever was ob tained. With regard to pulmonary tubercu losis, so definitely an added risk in sili cosis, this disease group has been drawn up to include all workers pre senting signs indicating a past or pres ent pulmonary tuberculous infection, but excluding cases of old inactive hilar tuberculosis. *Under this heading are included not only workers with definite clinical signs of active tuberculous lung infections, or of old inactive lesions, equally definite, but also those workers showing signs of old apical col lapse, usually attributed to a past tuberculous infection. Signs of the latter arc not uncom monly found in quite healthy persons, and arc of no importance unless* it is shown that the inhalation of asbestos dust is associated with pulmonary tuberculosis to an increased degree, when such cases, as indicating a group of workers with a latent infection, would assume a greater significance. No close association is apparent, how ever, since only thirty-seven, or 9.9 per cent, of the 374 examined, showed evidence of this disease, excluding cases of old inactive hilar tuberculosis, even when those showing the minor changes mentioned above are included. In only four was there a family history of pulmonary tuberculosis; and three out of four active cases belonged to this group. Thirty-three cases were inac tive, of which twenty-one presented no evidence of dust fibrosis, and twelve presented evidence. Out of the 374 persons examine^, fourteen, or 3.7 per cent., gave a family history of tuberculosis. Evi dence of active pulmonary tubercu losis was present in three; in two of these three the source of infection appears to have been a near relative. Thus, no outstanding susceptibility to pulmonary tuberculosis was dis closed, either among asbestos workers as a class, or among those with fibrosis, considering the frequency of old healed apical lesions among the general population. We have, however, by no means dis posed of the question. The superven tion of a tuberculous infection on a lung already the subject of fibrosis pro duces an increase in symptoms, pre viously unnoticed or disregarded, and causes the worker to seek his doctor's advice. He is then appropriately advised to give up his dusty employ ment, migrates from the industry, and J. I. H. June. 1010 0 AJ 6 i. PULMONARY ITBROSIS IN ASBESTOS WORKERS 255 may or may not accept sanatorium produce a serious and even fatal degree treatment. Thus there tcmls to be a of pulmonary fibrosis. drift of such eases from the fibrosis 2. The type of fibrosis produced, producing industry. however, exhibits a number of diverg During tho course of the inquiry, ences from that caused by the inhala information ivas obtained of a number tion of free silica dust, and the outcome of persons, previously employed in of these variations is not yet apparent. asbestos, who were either at home or in 3. Tho divergences noted so far are sanatoriums, suffering from chest com exhibited in the radiologic picture, plaints. Where an examination of and on postmortem examination of workers is confined to those at work, a the affected lungs, both in the gross certain number of advanced eases of morbid anatomy and in microscopic fibrosis, and a certain number of cases sections. of pulmonary tuberculosis, with or 4. In the latter case the appearances without an asbestos fibrosis, in persons of the asbestos fibrosis seem to be who have either given up work, or who sufficiently distinctive not to permit are off. work temporarily, will be of confusion between it and silicosis. missed. 5. The radiologic appearances of the I t is necessary, therefore, to leave asbestos type of fibrosis, even in the this question of increased susceptibility more developed stage, are more deli to pulmonary tuberculosis in abeyance, cate, softer, and more diffuse than the pending further investigation. silicotic fibrosis. With respect to any increased suscep 6. I t follows, therefore, that an tibilityto the supervention ofother lung opinion as to the degree and intensity diseases in workers with an asbestos of an asbestos fibrosis, based on a com fibrosis, the data obtained were insuffi parison of the radiologic changes with cient to lead to any conclusion, except those shown in standard silicosis films, as to bronchial catarrh. There are in will be an underestimate. dications, however, that when pneu 7. In the absence of a full medical monia or bronchopneumonia super and industrial history, possibilities of venes on a fibrotic lung, the prognosis confusion of the two types of fibrosis is grave. will arise in the interpretation of radio Ashestosis and S ilicosis C ontrasted grams. 8. There is evidence that other in In view of the relationship between organic dusts, containing no free silica, the asbestos fibrosis and silicosis, since may bo productive of this fine type of they ar both varieties of fibrosis of fibrosis in varying degree. the lungs caused by the inhalation of dusts, it seems desirable to summarize SmniART shortly the main points of similarity 1. There is a definite risk of tho and dissimilarity between tiie two dis development of a diffuse pulmonary eases, so far as has been ascertained. fibrosis in persons exposed to the in 1. Inhalation of asbestos dust, underhalation of asbestos dust. favorable conditions of concentration 2. This risk varies directly as the of dust and length of exposure, will length of employment (and hence v*i. No. * 0 i ii 6 ; ^ ______ "V. 250 THE JOURNAL OF INDUSTRIAL HYGIENE length of exposure to dust), and, is unaffected by the age of the worker. 3. There is a considerable difference between the least dusty and the most dusty processes investigated, and there is a corresponding variation in th e rela tive risk of the development of fibrosis in the workers in these processes. 4. W ith continued exposure to high concentrations of dust, the disease may be fully developed in seven to nine years, and m ay cause death after about thirteen years' exposure, exceptionally inashorter period. 5. Fibrosis as it occurs in asbestos workers differs considerably from the disease as it occurs in workers exposed to free crystalline silica dust; it differs in the radiologic picture, and also on postmortem examination of the affected lungs. 6. The more dusty processes are those involving the preparation and manipulation of the raw asbestos (other than crushing), dry cloth weav ing, and mattress making. 7. The less dusty processes are spin ning and similar processes, and proc esses, other than dry weaving, in volving the manipulation of the spun yam. 8. Further investigation is required to determine whether there is any in creased susceptibility to the superven- tion of pulmonary tuberculosis asso ciated with the development of the asbestos fibrosis. Much generous assistance has been re ceived from many sources during the course of this inquiry, and for this acknowledgment Is gratefully tendered. In addition to those already referred to, the writer is beholden especially to Dr. 3. A. Henry, who did much to facilitate the investigation, particularly by hia detailed reports on various relevant matters, and by much organization and liaison work; to many others of his colleagues in the different dis tricts, to a number of directors and officials of various firms, foremen, and employees; to Dr. \V. E. Cooke of Wigan and Professor M. J. Stewart of Leeds for pathologic mate rial and for much information as to the progress and results of their own researches into the gross anatomic and the histologic features of the asbestos fibrosis, and the constitution and location of the curious bodies; to Dr. MacGregor, Medical Officer of Health for Glasgow, for various clinical and radiologic facilities, and for his ever present readiness to lend the aid of his Department, and especially to Dr. H. E. Seiler of his staff; to Dr. J. C. Robertson for the loan of a radiogram, together with detailed clinical notes of one patient and other valuable information; to Dr. W. H. Bateman for the loan of a radiogram, for some clinical histories, for obtaining and examining several specimens of sputum, and for other aid; and to Dr. J. Rennie, Chief Tuberculosis Officer at Sheffield, for a series of radiograms showing various stages of silicosis. BIBLIOGRAPHY 1. Departmental Committee on Compen 4. McD o.vald, S.: Histology of Pulmo sation for Industrial Diseases. Min nary Asbestosis. Ibid., p. 1025. utes of Evidence, Appendices and In 5. Seiler, H. E .: A Cose of Pneumoconio dex, 1907. Cd. 3496, p. 127; Report, sis. Result of the Inhalation of 1907. Cd. 3495, p. 14. Asbestos D ust. Ibid., 1023, S, 932. 2. Cooks, \V. E.: Fibrosis of the Lungs 6. S m so x , F . W.: Pulmonary Asbestosis Due to tho Inhalation of Asbestos in South Africa. Ibid,, 1923. t, S35. 3. CoDoukset,. WB.riEt..:MPeudl.mJoonuarr.,y 1A92s4b,eJs,to1s4i7s.. 7. RoMyainlesCaonmd mQiusasirornies.onSeMcoentdalRlifeeprooruts, I! Ibid., 1927, S, 1024. 1914. Cd. 7476, p. 146. J. I. H. Juiw. 1930 0 Ao G PULMONAllY FIBROSIS IN ASBESTOS .WORKERS 257 8 . B a d h a m , C . : N o tes on a Fine T y p e o f 21. Stewart, M . J ., and I I addow, A. C .: Fibrous Pneumonokoniosis Produced D em onstration of the Peculiar Bodies by Silicates and O ther M inerals. of Pulm onary Asbestosis ("Asbestosis S tudies in In d u st. liv e . No. 13, R ep. Bodies") in M aterial O btained by Dtr.-Gcn. Pub. H ealth, New South Lung Puncture and in the Sputum. W ales, fo r 1937, Section I.-E , In d u st. J o u r. P a th , an d B act., 1929,3 2 ,172. H yg., p. 103. Sydney, 1929. 22. M acklix, E . L ., and M iddleton, E . L -: 9. C l a r k , W. I.: The D ust H azard in the R eport on the Grinding of M etals and Abrasive Industry: Second Study. Cleaning of C astings w ith Special T h.is J o t n . , 1929,11, 92. Reference to the Effects of D ust In 10. P axcoast, H . K ., and P en d er g ra ss, E . halation upon tho Workers. London, P .: Pneumoconiosis (Silicosis). A H . M . S tatio n ery Office, 1923. Roentgenological Study. New York, P au l B . H oeber, In c., 1926, p . 133. 11. T hompson, L . R ., Brdxoage, D . IL , R u s s e l l , A . E ., a n d B l o o m fie l d , J . J .: The H ealth of Workers in D usty Trades. I. H ealth of Workers in a Portland Cement Plant. U. S. Pub. H e a lth B ull. N o. 176, 192S. 12. Goadbt, K . W .: Fibrosis of th e L ung in Iron M iners. Jour. Roy. M icr. Soc., 1925, p . 432. 13. A nnual R ep o rt of th e Chief Inspector of F actories an d W orkshops for 1923, p. 04. L ondon, H . M . S tatio n ery Office, 23. SuniXKLAXD, C. L ., AND BrTSOX, S..* R eport on the Incidence of Silicosis in the Pottery Industry. London, H . M . S ta tio n e ry Office, 1926. 24. Sutherland, C . L ., and Bryson, S .: R e p o rt or th e Occurrence of Silicosis among Sandstone Workers. London, H . M . S ta tio n e ry Office, 1929. 25. Wood, W . B ., and P age, D . 3 .: A C ase of Pulm onary Asbestosis. Tubercle, 1929,10, 457. F or the geologic and the m anufacturing and industrial aspects of asbestos, see: 1929. 28. Cirsel, F .: Chrysotile-Asbestos, its 14. P e n n y , F . W .: In "In d u strial an d ' Occurrence, Exploitation, Milling, M anufacturing Chemistry" by G. and Uses. Second edition. Ottawa, M artin . ,1917, P a rt 2, p. 231. G o v t. P rin tin g B ureau, 1910. 15. Compiled by A sbaioa, a m onthly trade journal published in Philadelphia, Pa. 16. Annual S tatem en t of the T rad e of the U nited Kingdom , for 1922 an d 1927. London, H . M . S tationery Office. 17. D epartm ental C om m ittee on Compen sation for Silicosis dealing w ith the Refractories Industries (Silicosis) Scheme 1919. F irst R eport, 1924, p. 29. 18. S u rra , A. R .: Silicosis am ong Rook Drillers, Blasters, and Excavators in New Y ork C ity . T his J our., 1929, 11, 39. 27. Asbestos, its Sources, E xtraction, P rep aration, M anufacture and Uses in Industry and Engineering. Berlin, B ecker a n d H aag, 1923. 2S. T horpe, E .: A D ictio n ary of A pplied Chemistry. London, Longmans, G reen & Co., 1912. 29. Asbestos, a m onthly trade journal pub lished in Philadelphia, Pa. F or description of processes, and further discussion on the incidence rate of fibrosis, and effect of work in different processes and also preventive measures, see: 19. W o o d , W. B .: P ulm onary A sbestosis. 30. M erewether, E . R . A., and P rice, C. Tubercle, 1929,10, 353. W.; R eport on Effects of Asbestos 20. G l o y k e , S. R .: The Presence o f th e D ust on the Lungs and Dust Suppres Asbestos Fibre in the Lesions of sion in the Asbestos Industry. Lon Asbestos W orkers. Ibid., p. 404. don, H . M. S tatio n ery Office, 1930. V el. No. t 0 i . <j (3 4