Document J3ezqnorkLB9DJZKJ3KjZ956e

THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS.IN-ASBESTOS WORKERS* E. R. A^Mrrewztheh, MID. H. H. Medical itupeclor of FazLoritx Introd erenow He wij treated in tie Charicg Cross I::s- RIOR to the commencement of Pthis inquiry, in February, 1928, definite knowledge existed of pitsl for two months, and tben retur-ed to work. After s few months, however, he became ill again, sad w&j re-tdcit:<c 10 tie Hospital in April, 100, where he ditd Tie only two deaths of asbestos workpeorsst-mortem elimination confirmee tie about whom there was expert opinion clinical diagnosis of extensive pulmc.m.Tfibrosis. There was no evidence of pulmo that the inhalation of asbestos dust nary tuberculosis, and examination of to* had at least contributed to, if not sputum for B. tuberculosis was negative. caused, the fatal outcome. The first of these, in retrospect the most suggestive, only came to light some years after the occurrence, when The secondcase was reported by Dr. W.__ E. Coo_ke. Ln_ L9244 eighteen years later (2); full information was unobtainable. All that is known of this case, now referred to as "the Montague Murray Case," is contained in the evidence given by Dr. Montague Murray before tbe Departmental Committee on Com The deceased, a woman, sge-i 33, who died in 1924, had worked in ubestor fer la years, but intermittently for the Las*. I years, owing to periods of ill-hoslth. The post-mortem examination revealed, sot only extensive fibrosis of the lungs, but also pensation for Industrial Diseases in much change due to pulmonary tuberculoela. 190G (1). From this source, we learn that: Although. .Cooke_i3) and _S:uart _ -- McDonald (4) were cob iyely of Ehc The patient, . the care at Dr. male aged Montague M33u, rcraamyeautathde'_(ojEpimnioionTttbjiaatt iinn"tthhilsS"~` casc the lungs Charing Cross Hospital in the beginning of showed a progressive dust fibrosis, :o- 1899. He had worked with asbestos for ccther with__a chronic tuberculous in "some 14 years," 10 years &j a cardroom hand, and the remainder in some other room of the factory, "where there was much leas dust." He volunteered that, of the 10 people working in the cardroom when he went into it, he was the only survivor, and fection, ..the. etiologic relationship tye-_ tween the inhalation of asbestos cust and .fibrosis of the lungs would have been strengthened by the absence of a tuberculous infection. . that all the others had died somewhere about 30 years of age. There is no note as to the nature of his work, previous to that in the asbestos factory. ""Cooke's case is."however, of out standing importance, not only becaus-e of the discovery of "curious bodies'' in the lungs--discussed later--but also, * Received for publication Feb. 17, 1930. and of more importance generally, bc~ 198 '.V V '1. :R Ho*, ed to r, he o the The the aarjr .Intof the e. Dr. ears who >r 18 it s The not &lao >ai*. art the ags totinhe ist ve ia !t,se s" 50, >e- if. 9)0 r.i<~ PULMONARY FIBROSIS IN ASBESTOS WORKERS 199 tev jST * ^2 So..'. Wfcs-' cause its publication., again- directed This case, at that time the third of attention.to.the possibiiity.that inor- which the Factory Department had ganic dusts containing,little .or no free knowledge, was, however, the first in silica .may_.be. productive-of extensive. which the four essential' conditions, pulmonary fibrosis. Of these dusts, ^necessary to establish a relationship the silicates form a very iarge class, .between the inhalation of asbestos dust of which asbestos is but one example. and_the development of fibrosis, could Many other members of the class, be demonstrated. These conditions such as the feldspars, kaolin, French are: chalk, and pumice, are extensively 1. Work involving exposure to asbestos used in industry'. The importance, dust. therefore, of delimiting the potentiali 2. The existence, demonstrable clinically ties of the doss a3 producers of pul fed radio!ogically, of * definite pulmonary monary fibrosis is clear. Cooke's case was the first to be generally reported in the medical /bras is. 3. The absence of previous or present in fections known to cause pulmonary Eo.-osia t.ff., tuberculosis, influent*, or pneu press; the facts of the Montague monia. Murray case, although contained in the evidence presented before the Departmental Committee in 1906, and 4. The absence of previous or present work involving exposure -to other dusts, which might cause pulmonary fibrosis. published in 1907, were liable to be These conditions being fulfilled, a overlooked in the mass of important relationship between the inhalation of material on industrial diseases elicited asbestos dust and the development of by that Committee. the pulmonary fibrosis may be pre Since Cooke's case, Dr. I. M. D. sumed. Grieve ha3 made a careful study of a The importance of establishing group of asbestos workers in his prac whether the supervention of this dis tice, and has courteously allowed ease in an asbestos worker was an access to hisrecords. exceptional occurrence, .or evidence of In February, 1928, Dr. MacGregor, a grave health risk in the industry, was Medical Officer of Health for Glasgow, now apparent, and steps were taken, drew my attention to an asbestos forthwith, to obtain pri?na fade evi worker who was receiving treatment dence in proof^fljh^proof, of the exist in one of the hospitals in that city; ence of such a risk. This case, the details of which have A number of workers in asbestos been reported bj' H. E. Seiler (5), pre were selected and examined clinically sented, both clinically and radio- and radiographically. The findings logically, signs of a diffuse pulmonary invited further investigatiou'through fibrosis, with uo-evidcnce of a tubercu out the industry, with the result that a lous infection. On further investiga comprehensive inquiry involving the tion.into the patient's industrial and investigation'of the differeht processes medical history, no presumptive cause, in relation to the evolution of dust, and other than the inhalation of asbestos the examination, both clinical and ra dust-, was found to account for the diologic, of workers, was undertaken existence of the fibrosis. during the year 192S, commencing Vol. 11 No.* -a -S. "*i t..ft 448067 IIH- l* 200 THE JOURNAL OF INDUSTRIAL HTGIENE with the carding, spinning, and weav ing processes of the industry. In the meantime, in March, 192S, the death of an asbestos worker (one of Dr. Grieve's cases) o-jarred 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 I92S, also, Dr. F. W. Simson (G) 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 necessary to review the investigation made in 1910 to 1911 by Dr. Coliis and Miss Whitlock--the only previous inquiry into tbe subject. In May, 1910, the Registrar-Gen eral drew attention to a death which had been certified as "acute pulmonary phthisis in an asbestos worker," and to a statement (for which he was un able to vouch) that seven other deaths from phthisis had occurred in the same factory. Following this, extensive inquiries were made, a medical report on all the employees in the factory concerned was obtained, and Dr. Coliis and Miss Whitlock investigated generally the various processes in the industry with respect to the evolution of dust, methods of ventilation, lost time due to sickness, etc. Also inquiries were made of the Canadian government as to the conditions in the asbestos quarries and mills in that Dominion, evidence of increased sickness and mortality rates among the workers, and any methods of ventilation which had been found of especial value. The result of this investigation did not conclusively prove that asbestos possessed injurious properties, .but it pointed to the probability that such was the case. It is interesting to con sider why it was that no conclusive proof one way or the other could be obtained, then, as to tbe injuriousness of asbestos dust. Some, if not all, of tbe factors which afiected the position then are, in varying degree, continu ing factors, and have an important bearing on the present inquiry. Their operation, while providing a solution to this query, also affords an explana tion to another pertinent question: Why is it that this industry, founded in antiquity, has only recently excited attention, by reason of its raw material becoming suspected as a cause of indus trial disease? The answer appears to be that in the past it was not practicably possible to obtain proof of the injuriousness of asbestos dust, considering the limita tions imposed by tbe state of the indus try'! and the point reached by research work into the relationship between dust inhalation and diseases, of the lungs. _y^` The industry itself, not s 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 pneuruonokoaiosis must have been quite small, and dis persed over the country. Precise knowledge of the morbid affections of the lungs produced by the inhalation of dusts was more l'ragmen- l n. stu. SM V.' tv *1 I fc 448068 ' i which e.ion c. sbcstos but it it such to con clusive uld be )usness : all, of osition mtinulortant Their ffution planaestion: unded ocdted ateriai tndus- in the ble to ess of imita indus. search . tween if the large sider>egun er of ioyed ?h to finite aiosis i(dis- orbid >y the pnen- J. I. H. wr.tua . ftSJfci-'*: & iM- U:-.. b*Vsi* ` --^ -- -------- PULMONARY FIBROSIS IN ASBESTOS WORKERS 201 t&ry than it is today. The position show an excess mortality from phthisis, was clearly stated two years later in and those which do not--as well as evidence placed before the Royal Com being a comparative index of the in mission on Metalliferous Mines and dustries belonging to the former group, Quarries. This Commission, when re not only is of little value as a means of porting in 1914 (7), stated "we do not classification in the latter group, but know whether other dusts besides those also tends to distract attention from it, containing free crystalline silica induce and to result in the associated dusts be a pathological condition in the lungs,, ing dismissed as more or less innocuous. though the experiments of Professor Evolution of dust is oniy one factor, Beattie in animals suggest that this though an important oae, which may may occur." It is only in the last year cause variations in the phthisis mor or two that research has produced some tality rate in different industries. definite evidence as to the precise Wages, hours of work, aggregation of effects of some of these dusts on the workers, amount of food, housing, and lungs (8) (9) (10) (11) (12). other social and environmental condi In 1910, radiography of the lungs, in tions are, however, powerful Influences both its technical and its interpretative in the same direction, and are not asoects, was still in its infancy aDd, necessarily comparable as between the so far from having attained its present workers in any two industries. status of being an indispensable aid to In thus reviewing some of the influ the diagnosis of the dust diseases of the ences which have retarded recognition lungs, was an unused ally. of the baneful effects of some dusts In addition, the existence of a meas upon the lungs, the singular attributes ure of exhaust ventilation in the most of pulmonary fibrosis, the most impor dusty processes of the industry, incom tant of the diseases caused by the in plete as it was, had important results halation of dust, must not be over in modifying the onset, course, and looked. duration of any pathologic lung condi This disease, insidious in its onset, tions resulting from the inhalation of stealthily advances with but faint the dust. This influence has been warnings of its progress; inexorably it much more pronounced in the period cripples the esSBhtial tissues of the intervening between 1912 and the lungs, yet for a considerable period present inquiry, and will be referred causes almost no inconvenience to the to again. worker. As time goes oo, however, Another factor which has tended and IheTungs find more and more difficulty still tends to obscure the possible in re-aerating the blood; and breathing deleterious effects of the non-silica is quickened on slight exertion*. Still dusts, is the general use of the phthisis the worker is able to remain at work, mortality rate as a comparative index but is aware of his undue shortness of of the degree of injuriousness of the breath on extra effort. Usually, how dust encountered in the various dusty ever, he ascribes it to causes other than occupations. This rate, while of great the dust he is inhaling. value in separating dusty industries As the disease progresses, if no acute into two great groups--those which illness has caused a fatal termination, Vol. u No. S Of: 448069 202 THE JOURiN/iL OF INDUSTRIAL HYGIENE a stage is reached when the luaga can asbestos dust has a totally cinereal do little more than maintain life; and physicochemical constitution from that the shortness of breath is extreme. of dusts containing much fre-e silicaaad Even in its terminal stages, the disease causing silicosis. It was felt that deceitful to the last, may masquerade although much vaiuabie guidance as chronic bronchitis, pulmonary tu could be obtained from the methods berculosis, bronchopneumonia, or the of investigation of silicious dusis, cure like. had to be taken to keep an open mind, While more or less acute cases of so as not to be unconsciously biased fibrosis closely simulating radian' in the direction of assuming that the tuberculosis have occurred, even in this effects of the dust, if any, must be com country-(13), they have all been asso parable in some degree to those of ciated with the inhalation of dense crystalline silica. concentrations of free silica dust, and are, fortunately, the exception rather than the ruie. ' The difficulty of diagnosing pulmo Asbestos and tee Asbestos LvDtrsrsr Asb&sLiis nary fibrosis, especially in its early The term asbestos is a collective stages, or if complicated by tubercu name, of no definite mLaeralogic sig losis, has been stressed by a number of nificance, which has been applied to a authorities, and has, undoubtedly, con variety of silicate minerals, which differ tributed to impede the attainment of from one another in chemical compo precise knowledge of the extent to sition and physical properties, but which the various industrial dusts which resemble one another in their affect the lungs. finely fibrous feature and flexibility Difficulties and obscurities still im (14). Their value depends on the pede, though to a less degree than in facility with which they are capable of the past, any investigation into the being split up into long and flexible effects of an industrial dust upon the fibers, which can be spun like cotton lungs of those exposed to it; but prior and woven into cloth; on their resist to the War, although there were certain ance to heat and acids; and on their slight indications that asbestos, in insulating juffifirfies with" respect to common with some other dusts, heat and electricity. might produce permanent pathologic Varieties of asbestos possess these changes in the lungs, it was not possible qualities in differing degree. Com to obtain evidence sufficient to prove mercially, therefore; selection is made or disprove this hypothesis. by the manufacturer of. that variety At the outset of the present inquiry and grade which is most suitable for into what, if any, pulmonary diseases the purpose in view, regard being paid workers exposed to the inhalation of to ordinary economic factors, such as asbestos dust are more prone to con the cost of the raw material, and the tract than the general population, it price which the finished article may be was considered essential to. view the expected to command. problem afresh, and with complete Consignments of asbestos of the detachment, because of the fact that same general variety, but with differ- j. t. it. sUr. two 1 y A'v- ir: .i a r :i -. e .[ l\ A \i v`.is >-.( t.i30l 448070 ifferenfc >m tb-T` icaa. t that lidance etbods a, care i mind, biased lat the e com* ose of os lective ic sigd to a i differ ompoi, but. their ibility a the ibie of exib. :otton resist- their jct_ to these Cornmade ariety le for ; paid ;cha3 d the .ay be f the iiffer- j. i. n. ay, 1W0 PULMONARY FIBK0SI5 IN ASBESTOS WORKERS 203 ent countries of origin, are frequently bined water, and usually more cal mixed in the preliminary processes of cium, aluminium, and iron.' Members manufacture. Thus Canadian chryso- of this group are resistant to acids, tile may be mixed with Russian, or but are more difficult to spin, 3omc Rhodesian chrysotile, and so on. Less being quite unsuitable for this purpose. frequently, totally different varieties, The most important members of this such as amosite and chrysotile, may be group are crocidoiite, amosite, and mixed. tremolito. Practically speaking, all that goes Crocidoiite 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 lavondcr-blue color, the latter fibrous mineral of the amphibole, or being brownish-gray. Both are spun hornblende, group. The former is the and the yarn is woven into doth for most important commercially; but various purposes, such as acid filter strictly, the mineralogists confine the ing, and for making into insulating TABLE X.--COMPOSITION OP SERPENTINE AND AMPHIBOLE VARIETIES OF ASBESTOS PERCENTAGE Of UXXERAXe aaoup VARIETY SiO, AijOl oo Com MgO C0 Na,0 K,0 bined Water Serpentina Chrysotile 39-42.5 0-3.7 0.7-4.4 39-43 0-0.35 , , 4 13.3-18.5 Amphibole [ Crocidoiite 50.5-52.1 0-i 35.5-37.4 0-3 0.75 a.2-9 . . . 1.6-4.5 (horn- | Amosite 48-53 1.2-9.4 34-44 0.7-8.4 0-2.5 2-3.8 blende) l Trcmolite 67.2 0.9 3.2 22.8 13.4 0.6 0.3 2.4 term asbestos to fibrous forms of horn blende. These two types are sharply . distinguishable, chemically' and miner- alogicaily. Serpentine asbestos, or chrysotile, is a hydrated magnesium silicate, con taining practically no calcium, a high percentage of combined water, and a low percentage of iron. This variety is very suitable for spinning, but is attacked by acids. Nearly SO per cent, of the world's production of asbestos is derived from Canada, and is of this .variety; the remainder comes mainly from South Africa and Russia. The amphibole, or hornblende, vari eties contain less magnesium and com- mattresses, as well as for other pur poses. Both are produced extensively in South Africa, from which quarter all required commjjpeinfiy is ^obtained. Amosite, a coift^arativelyreccnf dis covery, is found there in very' large deposits; its use is steadily increasing, the initial difficulties.associated with the manufacture of textiles from this variety haviug been overcome. Tremolilc, found in various quarters of the world, has been mined in north ern Italy since the time of thd Romans. Its chief use is in the manufacture of asbestos millboard and for filtering purposes. Tabie I, compiled from various Vol. 1J No. 4 S j i : l t *r * 'ii.' I1' i ?t 1: I! f >> 1 i X i f i- ir. t l 1 448071 W-'Xfl- TT I w.>,. frnru,-. 204 THE JOURNAL OF INDUSTRIAL HYGIENE sources, show? the main differences in reexported. Thus the consumption of the composition of these four varieties. asbestos in this country trebled within Only a very small proportion of the five years. 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 The Industry On considering the uses of asbestos one is astonished, not only at the wide rangp of articles manufactured from 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 trial uses for these very short fibers, 1. Proceues involving the tnanipuLtioa 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 of ubeetos, either pure, or tdrnued with & smell proportion of cotton, or other vege table fiber. 2. Processes involving the msnipulstion of asbestos together with other dusty ma terial*. the yam and cloth in the manufacture 3. Processes involving the a aLing up of of steam packings, insulating mat asbestos cloth into other articles. tresses, brake linings for motor cars, Group 1 entails exposure to asbestos fireproof curtains, and the like. dust mainly, and toWUah, or Other In 1S80, three years after the dis vegetable dust, very slightly;-group' covery of the large Canadian deposits, 2 entails exposure to asbestos dust in the world production of asbestos was very varying amounts, and also expos little over 500 short tons; by 1900 it ure to divers other dusts, such as brick had risen to about 35,000 short tons, dust, magnesia, kiesciguhr, fossil meal, by 1920 to over 230,000 short tons, and and cement; in group 3 the exposure to by 1925 to over 330,000 short tons (15). asbestos dust--provided no other as The imports of asbestos (all grades) bestos processes arc being carried' on into the United Kingdom rose from in the vicinitj---is, in the majority of IS,591 tons in 1922 to 33,520 tons in cases, negligible. Processes belonging 1927 (16). The figures for 1927 refer to all three groups may be carried on in to Great Britain and northern Ireland- ChTlame'factorj-T^and workers may r only. Of these quantities S,S44 tons traDsfcrTfromybhc/;department to , and 3,794 tons, respectively, were another (30). (L . -Ia-AA 7 tOtr IV fl- <r-\ Sm. 1 i; .J .V f-r. : l. c: L c. t r 448072 nption of sd within "S'* asbestos the wide red from 3 proporof Indus* its use f the raw articles, ne multi* encoun?e indusve to be t to the ry. Vnay be ipulition ed with a bar. rege- ipulation ujtj m*> ag ur asbestos or other L group ' dust_in o exposas brick si! meal, osure to ther asrried on , ority of longing ed on in :rs may .ent to fife PULMONARY FLUiiUSIS IN ASBESTOS WORKERS 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 coroiiary, would lose much of its value into ropes for use us steam packings jMZ. 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 Seder's cases keting steam engines, and for other YtV i*/- 5.:- 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 kicselguhr with a small per x*(. groups I and 3. centage of asbestos fiber. The man The processes included, therefore, ufacture of mattresses filled with BirE'' are 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, slipperincss, and lack operations incidental thereto. Also of strength of the individual asbestos f.ff T.. j? Included is mattress making, whereTSe filling is asbestos, and the manufacture .of some insulating materials, where the fiber, as compared with cotton, flax, wool, silk, and other textile fibers, have 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 variations in the physical properties of cotton industry, but with essential the raw materiaLare_reflected in the modifications and restrictions caused methods cmph^aJoy each., JFor these by the different physical characters of reasons, and because of the great num the asbestos fiber. These processes ber of patented and special products are aided by an admixture of cotton, manufactured, one finds considerable or other vegetable fiber, and usually differences in detail in the processes in from 2 to 10 per cent, by weight of use. cotton is added. More rarely, and for The majority of the processes men L2S--J- special purposes, long-fibcred.asbestos tioned result in the evolution of dust, is carded and spun with no admixture although by no means to the same of vegetable fiber, but usually asbestos extent, differences in plant, quality yarns contain a core of either cocton of asbestos used, methods of manufac or metal wire. ture, type of finished article, and extent Asbestos yarns are not only used for of application of exhaust ventilation, >4? , rtf:- I ^5 448073 206: THE JOURNAL Oi- INDUSTRIAL HYGIENE all result in variations in the evolution of dust in similar processes in different factories. Variations in the evolution of dust in different processes being of outstanding importance, a scries of samples of dust from the air of workrooms was col lected, by means of the Owens jet apparatus. ' PopulationalRisL--A calculation of the"total number of workers employed in the processes already enumerated as TABLE 2.--DISTRIBUTION', ACCORD ING TO LENGTH OF EMPLOYMENT, OF (A) 775 WORKERS ENGAGED IN ASBESTOS PROCESSES AND ` " (B) SELECTED SAMPLE OF 363 WORKERS (A) (B) | PERCENT. TBJJ. EUFLOTED uVHZ z6 utu zo 0-4.............................. 4S3 62.3 89 24.5 5-9.............................. 200 25.8 141 38.8 10-14............................ 51 6.6 84 23.2 15-19............................. 24 3.1 2S 7.7 20 and over.................. 17 2.2 21 5.8 Total......................... 775 100.0 363 100.0 included in this inquiry, but excluding those engaged in processes included in group 3 in which the exposure to as bestos dust is negligible, gives a figure of approximately 1,600; if we could add to this the number of workers engaged in handling pure asbestos fiber only, in the preliminary stages of the processes included in group 2, we should obtain the total population at risk from the effects of asbestos dust it self. Unfortunately, this latter figure is unobtainable; but a rough estimate, and' most probably an overestimate, is 600. Thus, about 2,200 appears to be the total population at risk in this country, for the purposes o'; this in quiry. This figure, however, docs not include the large number o; workers engaged in the processes in group 2 which involved exposure to the influ ence of mixed dusts, of which asbestos is but one, and commonly not more than 20 per cent, of the mixture. This estimate of the population at risk, although it may be excessive, is useful, since it enables us to judge of the adequacy of the sample o: workers examined, and to apply more correctly the incidence rates of any pulmonary affections disclosed by the examination of the sample (30). The sample examined (after eieven cases are excluded of fibrosis and prefibrotic conditions due to causes otaer than the inhalation of asbestos dust) numbered 363, representing 16.5 per cent, of the population at risk, esti mated as above. The manner of selection of the sample must be referred to, since just interpretation of the results depends upon a due apprecia tion of the relationship of the sample to the whole population at risk. The principle of seating primarily those longest employed was-adopted;* but regard was also paid to the other end of the scale, so os to obtain infor mation as to the length of exposure to dust necessary before effects are mani fested, and also as to the particular process in which the worker was engaged. It was felt that, in this way, the maximum information would be obtained in the shortest time. Table 2 shows the distribution, according to length of employment (not necessarily in one factor}'). , estimate, ppear*-to sic in s :* this indoes not workers group 2 the influasbestos iot more -e.'iation at essive, is judge of workers. correctly ilmonary ruination :r eleven and preses other os dust) 16.5 per sk,' estiuner of referred of ppreciaample to rimarily tdopted; he other in iaforosure to re maniirticular .er was .t his way, ould be ibution, ioyment ary), of j. i. n. Ur. leu ", f M ./A -'51 A PULMONAHY FIBROSIS IN ASBESTOS WORKERS 207 775 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 of workers employed under five available. Furtncrmorc, it must not years in these processes is striking, as be overlooked that such examinations is also the very low percentage of are voluntary, and not, p-s 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 that 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 empioyers 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. With a soli ent function in these inquiries, than tary exception, all those examined were when it is applied to individual cases 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 foreshadowed (IS, effects of dust upon the lungs, has been p. 40), but primarily that 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 determination of complicating lesions, sation for Silicosis (17). A high in measuring the extent and progress standard of radiography is essential; of the disease, in locating the point at as Watkins-Pitchford phrases it, the which the earliest radiographic signs radiograms must be "technically satis appear, and finally, as a check upon factory." Indifferent films are useless, the human factor presented by the since it is the fine detail of the lung examiner himself. which is being studied; The examiiffifom (except one) were In a general inquiry, such as thiss,, Vs carried ouUoUea^h factory^/tn a room hich Involves the examination of set apart for the" purpose, suitably workers iff'factoriesDarge and smal1, warmed, and with the necessary altered over*the~~countrv, 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-were exam the absence of a number of hands for ined by the writer. At three factories, this purpose, cannot be viewed with however, a number of workers were unconcern, especially when, as js not examined jointly with Dr.E. L. Middle- infrequent, the factory is remote from ton. IIi3 far-reaching experience of the 448075 208 THE JOURNAL O' INDUSTRIAL HYGIENE pathologic changes in the lungs, pro these, it diminishes in intensity, but duced by the inhalation of various still persists. In other words, we find dusts, was of great value, and his tacked on to the paravertebral aulncs3 assistance was much appreciated. an area, above and below, of impaired Every effort wa3 made complete resonance, which is much more exten the clinical examination of toe workers sive than that usually associated with before the onset of winter introduced old inactive hilar tuberculosis. difficulties due to ephemeral bronchitis, Impairment of the percussion note colds, and influenza, which would tend was found to be constantly more to obscure the main issues. Thus the marked in the right side; in fact, at first clinical, and two-thirds of the radio- it was thought that in the earliest graphic examinations were completed degrees of fibrosis it was confined to by the middle of November, 1928, prior that side, but later, and more extended to the commencement of the influenza observations lead to the conclusion epidemic early in 1929. that the earliest detectable cases are bilateral, although the signs on the'left t Clinical Examination side are tenuous. Percussion This change is so constant that it has been adopted as the most reliable single The inhalation of asbestos dust clinical sign presented by this type of originates changes in the lungs, which pulmonary fibrosis, and no case hah may be looked upon as a measure of been classified as fibrotic in its ab the efforts of the living tissues to repel, sence. or incarcerate, the irritant particles of Considering the frequency with du3t. These changes modify the per which signs indicating what may be cussion note. It is true that the note termed "enlarged roots" were found in elicited may be similar on both sides, asbestos workers, it may be that para but the note is not normal. It is vertebral dulness i3 one of the earliest thinner and higher pitched than nor signs produced by the inhalation of mal, and there i3 a sense of resistance asbestos dust, indicating congestive imparted to the plexor finger. In changes in the root areas and a choking other words there is a diffuse, but of the lymphatics with dust. Refiex slight, impairmentof resonance. impairment of notejJR'to irritation of This alteration in the percussion the lung tissue by dust, Is, however, an note, however, is more difficult to attractive explanation. It docs not recognize because it is bilateral, and follow, of course, that workers present extends over a wide area; consequently ing these signs will ever develop a defi the aid of contrast percussion is denied. nite-asbestos fibrosis. It is best elicited by rapidly, and Clearly, the physical signs presented very lightly, percussing the back of the by any case of diffuse pulmonary fibro chest from apex to base on each side. sis not only may be modified by It will be found that the extreme changes produced by some interctirrent apexes remain clear, but below the lung disease, but, ab ir.ilio, will vary' apexes the impairment is general. It according to the state of the lungs be increases over the root areas; below. fore the onset of the fibrosis. Thus, j. t. n. K*r. Iii3 S *- 448076 yr but re findnln paired exteni with i note more it first axlieat led to ended iuaion as are ae left it has single pe of e has s ab* with iy be md in para* .rlie in ot jstive oking teflex lo'&oP ;r, an ot sentdefi- nted ibroi by rrent vary ;s beThus, i. h. .r. KM ii.mii PULMONARY FIBROSIS IN ASBESTOS WORKERS 209 the fibrosis may be implanted upon a to healed tuberculosis. That there is perfectly normal chest, in which case an extensive fibrosis is clear enough, the problem of diagnosis Is straight and that most of it is not due to asbes forward. In other cases, however, tos is strongiy suggested-when examin preexisting root changes, so common in ation of the lower portions of the lungs an industrial community, may be pres shows that they are comparatively ent, or the lungs may be already the slightly affected. Further help in seat of emphysema and chronic .bron these cases, of course, may be obtained chitis, or of definite old tuberculous from the history and symptoms. lesions, or there may be a massive The third type, also rare, is that in pleural thickening, the result of an old which changes following an old massive pleural effusion. All these examples pleural effusion on one side so obscure have been noted in tbe present investi the physical signs of any dust fibrosis gation, and others will readily come to as to render that side useless ciioicaily mind. for diagnostic purposes. If the side ' Although in most of these cases the affected by the pleurisy happens to be dust fibrosis, if moderate in degree, can the right, the radiographic picture i3 be confidently diagnosed, especially also curtailed by the normal partial with the aid of radiography, it must be ' obscuration of the left lung base by the admitted that the problem becomes heart shadow. very difficult when the dust fibrosis is These three types were, with the comparatively slight, and the changes possible exception of the first, uncom produced by other conditions are pro mon, and are mentioned merely to call nounced and diffuse. Three types of to mind some of the ways in which an these cases have caused most difficulty asbestos fibrosis may be masked, in among those examined; fortunately, greater or less degree, by changes due numerically they were few. to other disease. The first of these is where the dust Only passing reference need be made fibrosis has been implanted upon lungs to the other physical signs found in the already emphysematous. It seems asbestos fibrosis, since they do not that, at any rate in the case of the differ materially from those presented asbestos fibrosis, until the fibrotic by silicosis. Cjjgjt expansion is dimin changes get the upper hand, clinical ished and reduced to one-haif diagnosis of the fibrosis in these cases inch or even less in advanced cases. i3 impossible. Nevertheless, although Retraction of the apexes is common, the problem of the diagnosis of a and sometimes shows a peculiar feature fibrosis implanted upon an emphy differentiating it from that found in sematous chest has caused some diffi fibroid phthisis. Instead -of tbe im culty in this inquiry, it seems likely mobile and sunken apexes seen in the. that it can arise only under exceptional latter disease, the apexes are seen to circumstances. descend during inspiration* and to rise The second type of case which has again during expiration. This seems been a source of difficulty in clinical to indicate the anchoring of normal diagnosis is that in which there are apexes by fibrous tissue in the lower extensive bilateral fibrotic changes due portions of tbe lungs. Some confir- Vol. 12 No. 4 !>. '-v 210 THE JOURNAL OF INDUSTRIAL HYGIENE malion of this was obtained, radiologically. A uscultaiion In the majority of the cases of fibrosis, the respirator}' murmur is weakened, much or Little, generally, more.-on the right side, and often still more at the base; the expiratory sound is weaker than the inspiratory, and often becomes less and less audible as one approaches the bases. Transitional phases between this and harshened breath sounds and pro longed expiration are not uncommon, even in the same chest. The latter may be noticeable in the upper por tions of the lungs, but progressively diminish toward the bases. Other combinations were also noted, how ever. The dry character of this type of fibrosis during most of its course i3 rather striking. Scattered fine rdles and clicks in the root areas, axillae, and bases were not infrequent; slight edema of the lower halves of the lungs was noted in one of the more advanced cases; but in a number, no adventitious sounds at all were heard. Pleural crepitations, and rarely a slight pleural rub, were noted--these attacks seem to cause little pain--and in one case a little'fluid at the right base. ~ No doubt this variability in the sounds heard on auscultation reflects underlying changes, temporary or permanent, in the lung, and is depend ent, inter alia, on the extent of the fibrosis with its associated pleural thickening--changes due to past dis ease, "catarrh, or other intercurrcnt affection, and to the degree of compen satory emphysema present. tsym plains The symptoms exhibited by these cases of fibrosis, as might be expected, closely resemble those of silicons. The "stribution of the main symp toms, and of one sign, cyanosis, which is included with the symptoms for con venience, is given in Table 3. A few cases have been excluded on the grounds that one or other of the symp toms complained of might be assigned to causes other than the fibrosis, such. TABLE 3.--DISTRIBUTION' OF FOUR COMMON SYMPTOMS, AND OF CYANOSIS, AMONG CASES ' OF FIBROSIS STU7TOU Cough............................. Cytnosis........................ Dvspno*............... ......... Expectoration............... Pain.............................. a cases is fti z VHlctt STMPTO* < was present y u ` oX No. Per Ccat. ' 91 54 59.3 93 52 55.9 91 47 51.6 91 31 34.1 94 10 10.6 1 Excluding those in which the presence of the symptom is referred to other causes. as a complaint of shortness of breath in a case wiE"~a nast-jyionr of nSld thyroid intoxication, oc 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 onetenth of pain, or discomfort, in the chest. Also, while 14.6 per cent, of the cases had no complaints and showed no cyanosis, and only 3.4 per j. i. it. Hi.), ucs - X\ ?f i3 Hh 4 p vu-} !. r*:? r * 448078 w '.r>- --"i^Ssksss^*tLff- <--a. : :y' th^e ixpected, silicosis, a sympis, which i (or con' A few oa the ie sympassigned sis, such. F FOUR D OF 5E3 . 3. Per Cent. t 59.3 7 55.9 T . 51 * t. 3 ) 10.o ireath'in of mild dyspnea. j. i. it. Mx. iuo PULMONAIIY FIBilOSIS fN ASBESTOS IVOlUEEilS 211 . cent, presented all four complaints and werecyanosed, 60.6 percent, presented two, three, or four of the five items. Clearly, none of the four complaints, or the presence of cyanosis, can be an .. infallible indication of the existence of fibrosis; but the presence of two of them, shortness of breath on slight exertion, and cyanosis in some degree,' in an asbestos worker, is highly sugges tive, in the absence of other evident cause. Nevertheless an advanced degree of fibrosis may be present, and little com plaint made. Symptoms, unless dis tressing, are so often a function of the introspectiveness of the patient. Slight degrees of fibrosis, too, give rise to no symptoms, in the absence of an intercurrent bronchitis, since the remaining sound lung tissue is still amply sufficient for all purposes. Cough was the most frequent symp tom, and was of two types. For a few weeks after commencing work in a dusty process, asbestos workers often find the dust irritating, and cough while in the dusty atmosphere; this lasts for a few weeks, and then usually disappears. The writer has noticed this effect pn himself, but only while in a very heavy cloud of asbestos dust. The dust seems to he only slightly irritant in this way. One or two men who had previously worked in cotton card rooms, or blow rooms, and were, affected by that dust, stated that they were unaffected by asbestos dust. .Certainly asbestos dust docs not cause :asthmatic attacks like those seen in cotton card room workers. One man, wiio migrated from a cotton card room '("hard waste") nine years ago^to an asbestos card room, on account of the irritating effect of the dust, does not i Vol. u No. 5 ;n find asbestos dust irritating, but to this day cannot work with a cotton scutcher (as he occasionally docs) with out precipitating a coughing attack within an hour or two. Although he suffers from winter cough and some shortness of breath, he stated that his health lias been much better since the change. Asbestos dust, therefore, has only very mild power? as a reflex irritant of the upper respiratory tract, and is, in this respect, comparable to free silica. This is an unfortunate attribute, since it leads to the assumption that the dust is more or less innocuous. The second type of cough is more intimately associated with the develop ment of fibrosis, and occurs, or perhaps is noticed, after a varying number of years' work. Usually it is present only in the morning on getting up, when after rather a sharp attack of coughing, a little viscid sputum "like an oyster" is brought up. A similar bout may occur at night after ceasing work; at times it is sufficiently sharp to cause retching. It is generally rather worse in winter, and may be noticed only then. Although it closely resembles smokers' coug^-its features are pre cisely the same-in nonsmokers. , Persons giving a history of cough dating from an attack of pneumonia or other illness in childhood, ulmost in variably state that the cough ho3 not become worse since working with asbestos. One worker succinctly de scribed the cough as "first in the throat; later catches the chest." Generally, this cough causes very little inconvenience and may pass un noticed until the development of some other symptom directs attention to the general state of health. Thus, out of kS-H.** 212 THE JOURNAL 01 INDUSTRIAL HYGIENE sixty-six cases of fibrosis, in thirty- and. in the remainder of the casts, three (50 per cent.) the cough was good. stated to have preceded the onset of shortness of breath, in twelve (18.2 per Radiography cent.) to have developed contempo Radiograms of the chest were ob raneously, and in twenty-one (31.8 per tained of 133 workers, or 35.5 per cent., cent.) was either not noticed until after of the number examined clinically. the' onset of shortness of breath, or, Of these, over 100 wore taken by Dr. although the latter was complained E. W. Twining of Manchester, and of, cough was not admitted. Dr.' N. Tattersall of Leeds, and the Complaints such as "colds go to the remainder (except one) by Dr. F. L. chest," and "frequent colds on the Henderson of Glasgow. To all three, chest," were not uncommon. Com I am much indebted. Dr. Twining plaint of spitting of blood was excep and Dr. Tattersall have devoted many tional; and in all cases in which this hours to the joint study with the writer complaint was mentioned, the exciting of the radiograms, and have drawn cause was, primarily, some disease freely on-their wide experience of radi other than the fibrosis--e.g., in one, it ography of the chest in furthermg'the was due to pulmonary tuberculosis; purpose of the investigation. in another, it occurred only during a Dr. R. S. Paterson of Manchester, prolonged attack of pleurisy; and in a too, added his experience to a final third, the hemorrhage, was gastric in renew of the films, and Dr. E. Barclay, origin. Cyanosis, a valuable sign now of Cambridge, lent his assistance when present, rarely amounts to more in interpreting some difficult films; than a duskiness, or slight blueness, of to both, grateful acknowledgment is the lips; it contrasts, however, with the made. general pallor of the face with which The standard of radiography wa3 it is often associated in these cases. very high; indeed, a high standard is Cyanosis in some degree was noted in indispensable, if it is desired to trace 56 per cent, of the cases. It may be the cause of such a fine and diffuse absent even when there is a consider fibrosis as that produced by asbes able degree of fibrosis, or it may come tos. - . and go. The films are supccfiSally, but. only . Pain in the chest is rarely com superficially, comparable to silicosis. plained of, and then it is usually de In the earliest negatives studied with scribed as "tightness of the chest," Dr. Tattersall, a characteristic slight "soreness," or "aching." It was noted obscuration of the lung fields', a general in 10.6 per cent, of the cases. lack oT transluccncy, was noted. This Well-marked clubbing of the fingers appearance, for want of a better termy- was noted in a feweasea. The general was denominated os "veiling." Dr. nutrition is hardly affected, except in Burton Wood has independently no.ted the latest stages. Only ten (10.5 per (19) and confirmed this, referring to it cent.)' were noted as being thin. In as the "ground glass appearance." one, the nutrition was very poor; in Dr. Tattersall also drew attention to twenty-one (22.1 per cent.), fair; the more or less rounded "whorls" of .cases, lester,i final trclay, stance films; ent is ;'onIy~ 3. I. H. ir. ma >m-- IW*' iii ii iTw- PULMONARY FIBROSIS IN ASBESTOS WORKERS 213 V &.'av.- M*' $sfV' (0:. cl varying size seen in the striation in the. The radiographic appearances in the mid-zones in some of the films. earlier stages arc most marked on the There was general agreement as' to right side at the base or in the central the fine and delicate nature of the zone. This corresponds with the clin characteristic mottling. Dr. Twining ical findings. This preference for the (in a personal communication dated right side has been noted aiso in Aug. 2, 1929)--while lamenting that silicosis, by the South African ob there has been, as yet, neither time nor servers. The cases showing radio- opportunity to study the changes from graphic signs of a dust fibrosis have every aspect, and therefore his present been classified in three broad groups. views may be modified on considera This grouping, although unscientific, tion of all the evidence--states: is convenient practically, considering the main purpose of this investigation. In genertl my opinion i* that tbe earli Indeed more precise classification est stages are not characteristic radio logical! y, but that the stage of fine dusty stippling is almost certain to be eventually provable as an early asbestos lesion. tVe saw it constantly in a large series of films, and alter a little experience it is quite easy to detect it. Some of tbe otber cases showed a few grouped lesions, like rosettes or leopard markings, each component being about tbe size of a primary lobule. These are similar to lesioos sometimes seen in tuberculosis. In tbe asbestos cases I regard them as being based on the particular radiographic changes noted might well be mislead ing at tbe present time. Much combined clinical, radiologic, and pathologic study is required into the whole subject of these fine typ.es of dust fibrosis, which have been noted in workers exposed not'Shly to silicate dusts other than asbestos, but also to other inorganic dusts containing no silica, before it will be possible to groups of primary lobules peeking up a lobule, tbe walls of wbicb are infiltrated. They certainly seem to correspond in size with the macroscopic-lesions seen in the pathological specimen. Tbe advanced case* show heavy basal and classify the radiologic changes os hss been doae so successfully by the South African workers in respect to silicotic fibrosis. The hypothesis that, because asbes mid-field mottlings, common in pneumonoconiosis, with a tendency to avoid the apices. On tbe whole the lesions are distinctly lest dense than those of silicosis, and are less easy to group into well-defined stages, but tos dust produces a pulmonary fibrosis with consequenlgdeviations-from the normal in tbeTCfng skiagram, the de gree and potentialities of this fibrosis can be assessed by comparison of its I think we can recognise: 1. A very doubtful stage of increased linear striations. 2. Fairly definite fine dusty stippled ' appearance. 3. Coarser mottling with increased linear Btriations. 4. Gross lesions with pleural changes and ' displacements due to the pull of tbe fibros ing lesions. The few tuberculous lesions we have come across have boen easily distinguishable. radiologic picture with those of stand ard silicotic films, i3 untenable. At least two general types of pul monary fibrosis_caused by inorganic dusts can be recognized. A third, representing the purely peribronchial variety of fibrosis, might be added; or it may be that all dust fibrosis will be found to approximate more or less closely one or the other of these two ~s "x\v: h~. .it .1; i -ui; h f >: jj( ' i' /-s 448081 2U .. THE JOURNAL OF INDUSTRIAL HYGIENE types. These types arc (1) that pro On study.:.:: the dcvci'.-rcncst c-f duced by combined silica dust, an asbestos fibrosis os displayed is a scries example of which is seen in asbestos of radiograms, and especially in the few fibrosis, and (2) that produced by free available taken a year or more before a silica dust, represented by silicotic fatal termination, one cannot help fibrosis. asking the question, "What is there These two types, while resembling here which could have tins 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 attempts to weigh, consciously or were, crisscross throughout the lung, unconsciously, asbestos fibrosis, or any enveloping and eventually strangling dust fibrosis other than silicosis, by the ultimate lobular structure, rather means of the standard radiographic than depositing itself in numerous changes found in 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 Mewing it from the standpoint source of error in reporting the unex of silicosis. pectedly early death of a man affected The radiographic picture may show with a fine fibrosis caused by an ortho- soft and fairly coarse nodulatioa, 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 *iiio*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 develop ment of fibrous tissue was greater in a nodular fibrosis as silicosis than in a general geneous stipphng^.the skiagram; all are fragments-afUfli entitjy-uamistakable when assembled, but enigmatic when divorced. Only two references to the radio- ised fine fibrosis caused by silicates. To me it appears that the mechanical damage to the lung is greater in a fine fibrosis thanin a coarse fibrosis when both are well developed. graphic appearances of the ciicst in asbestos workers have been traced: one in a report by Pancoast and Pendergrass (10), and the other in an article by Burton Wood (19). Pancoast and Pendergrass together with Miller and Landis examined "IT asbestos workers, 2 of whom showed j. i. n. My. 1910  V-- lopment of ' xi m a series lyin' few ore L-orea annot help tat is- there ais effect?" nage to the - appears to :otic stand* nuch more web, as it t the lung, strangling ore, rather numerous in silicosis, iadvanced ire of the ye, unconstandpoint may show ion, but it modulation :tive feailogir "y, fifon*...,/. oou; the pairment e homo grain.; all nmistaknigmatic le radiochest in traced: ast' and-' ter in an together ined "17 showed j. i. n. May. 1930 N M W1Tnt,t PULMONARY IIDROSIS IN ASBESTOS WORKERS 215 first stage changes and the other and by the time the stage is reached 15 definite second stage appearances, when the features discussed above are Of the men longest at work, one after in varying degree, positive, and the seventeen years' occupation showed radiologic picture is recognizable, the very definite diffuse, 'soft' spot3 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, recognise 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 convcn- indicating a persistence of free drainage iently as the prefibrotic stage, hilumward. In all instances the nodu- The indications of this, stage are lar shadows were characteristically indefinite, and some, at any rate, not `soft' and varied considerably in size." specific. If, however, they can be Their first stage appears to correspond determined and applied with only a with Btage 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 363 exam- original rock--a view difficult to sub- ined (5.8 per cent.) were so classified: stantiate. Burton Wood (19) in a series Of fif- Clinical Examination* . Per teen skiagrams of asbestos workers notes: "The most noticeable feature of skiagrams of workers exposed longest to asbestos dust is the presence of shadows suggesting a diffuse fibrosis affecting chiefly the lower two-thirds --; , , '. , ,, of .the lungs. The fine quality of the shadows is worthy of note. Some of the cases exhibit a 'ground glass' Prefibrotic conditions.......21 Radiologic Examinations (/) Fibrosis.............- 52 Suggcsuvejaogcs _a?t definitely diffuse fibrosis........................ 22 5.8 33.1 16 5 Many of these cases present a slight appearance, though on close inspection diffuse impairment' of percussion note fine mottling is evident. . . . when --perhaps bett er described as a slightly more definite mottling is present it increased sense of resistance felt on lacks the coarse quality described in percussion, mostly of the right lung, the skiagrams of chests showing pneu- at least as contrasted with the left, moconiosis, e.g. South African gold and associated with some weakening miners............... " of the respiratory murmur. Prob- Clcarly, the maturation of asbestos ably this early stage could be detected fibrosis is spread over a period of years, radiographically, but only by means of Vol. 12 Ho. i /s 448083 : fev^': . > , -. . ,, V . * -c. " a'. ..<* y. *%-*<*`^`-* C'*?: '-' ft'J f| C) 216 THE JOURNAL OF INDUSTRIAL HYGIENE comparison with a radiogram taken group is dismissed from any further prior to commencing work with asbes consideration. tos. By such means the earliest A general summary of .the Endings in stages of silicosis have Seen worked the 374 workers who were examined out by the South African observers. clinically, classified under the most im There, the radiograms taken at peri- portant lesion, is presented in Tabic 4. "odic six-monthly medical examinations can always be compared with initial Iu-cstiutive Cases radiograms taken before the employees The salient points of a few cases are are permitted to work underground. set out below to illustrate elinip.i.1 and . TABLE 4.--GENERAL SUMMARY OF FINDINGS CLASSIFIED UNDER THE MOST IMPORTANT LESION *[ . -w o4fa au fesi H CASES OF TIBBOSIS PREflBROTIC CONDI TION'S PULBONART TCBEBCO- LOSI5 5*1Ka c2_ 0u (* u5 oZ Due to O ther Causes Due to Asbestos Due to Other Causes W ith Evidcuco of a Dust Fibrosis O ther A ctive Lesions o0 wa 2 Va<f u a (J < wO 6z 3 Q :< 3O s ^ o> w so : s JC e Hz Os c e oo fa J* 2 w C2 -.2 o * is o (C wc c o4 5 <4 J foa oo 4< * = H2 OTHER* pcLuoNiar LESIONS 0* 2o 52 a 2# << > * e *el Q f! 1< fa w _o fea;* * H >% a r" c Q 4 4< a c z 23H* 0-4................... 92 0 3 5 0 0 0 0 5-9................... 142 36 l 12 0 1 1' 4 10-14................. 89 27 5 3 0 3 0 3 15-19................. 30 15 1 1 1 0 0 l 20 and over.... 21 17 0 0 0 1 0 0 13. 3 5 0 0 7 i 0 1 C2 3 5 2 n 72 0 3 o 0 3S 2 l10 7 1 .0 1 0 1 TotaL............ 374 95 10 21 1 5 1 8 Percentage... 100 25.4 2.7 5.6 0.3 1.3 0.3 2.1 21 5.6 13 10 6 3 ISO l.J -2.7 O.S 43.1 1 One case of thickened pleura due to old gunshot wound. 1 One esse of emphysema due to getting. In other cases included in this group, diffuse weakening of the respiratory murmur was noted, with fine sticky riles in the root areas. At present no stress can be laid upon this group. The clinical changes are so slightly marked that until comparative radio grams are available it would be unsafe to draw any deductions. For the pur poses of this inquiry*, therefore, this other features. Five- radiograms are "reproduced to illustrate the radiologic appearances of some of the cases. There are insuperable difficulties, however, in reproducing the finer changes depicted in the original nega tives. Case 1.--This worker, a female, aged 24, has been employed in astwsloa for ten and one-half years--ag a card Untcr_one year, J. I. n. lUr. isjo .\'.*-.y * * any.farther hefir ' 'gsia . .% V ,1v: .: re ex~iiined the most imd in Table 4. . -> . k3ES few cases are J clinical and .r- IDER THE THSK UOMA&T SIONS ` SCJ QO >t j3 UV a JwS Cd o H a 3 j< aa o z 7. a* 5 01 22 20 1.- r 1 62 ' 72 38 7; 1 fi 3 180 ' 1.6 0.8 48.1 * ' lOgrams are ie radiologic the cases, difficulties, ; the finer iginal nega- male, aged 24, a for tea and ter oae year, j. i. n. Uat, 1930 .5 - ( PULMONARY ITBUMSIS IN ASBESTOS WORKERS ' | 217/ \ //,. andns ji doubler ninc.and.onc-hnlf years. Her family and personal mzdical history contain nothing of note. She has no com plaints and feels quite well. Her nutritioa yiid tuuercuio-is of tin: iutig roms ami gencral increased striation, especially m the lower half of the right lung, suggesting cariy fibrosis. is good. She is pale, but shows no cyanosis. . Chest.--She lias a chest expansion of 1} inches. No impairment of the percussion Case 4;--This worker,'' a 'male, aged 23, has been employed in asbestos for nine years, mostly mattress making..' His family note is detected. The breath sounds in the fight lung are weaker, generally, than those in the left. Expiration is prolonged at the right root; no added sounds arc heard. A skiagram showed some very slight and doubtful chnngcs in the direction of in creased strialion. Case Ji.--This man, aged 24, has been employed in asbestos for five years, carding and'mixingT*reviously he workecTfo?'fou'r yrara in tile cotton trade, yarn weighing. His"fami)y and personal medical history contain nothing of note. He has had a slight morning cough and expectoration for a year. His nutritioa is good. Ilis color is fresh, and there is no cyanosis. CTicxl.--There is some impairment of the percussion note over the middle third of the right luug, behind, and slightly at the right base. The breath sounds are harsh, and expiration is prolonged in the upper half of the right lung, behind; expiration is also prolonged over the left upper lobe, behind. The respiratory murmur is weakened at the right base, and the breath sounds are of a "whiffing" character. There are no added sounds. A skiagram showed enlargement of the right root, ami slight haziness and striation in the central zones in both lungs, suggesting early fibrosis. Case 3.--This man, aged 32, has been employed in asbestos for six years in the card room, anil"ns a stripper and "grinder. P-rcviously he was employed in a cotlon card epom.for.nine years.'" Hc'ha'tf army"scrvicc for five years, but was not gassed. He gives a fninilv history of asthma; otherwise there is nothing of note in his family or personal medical history, lie has no complaints and feels quite well. His musculnlurc is very good. His color is pale, but he shows no cyanosis. Chc^t.--There is slight impairment of the percussion note generally, particularly at the right base. The respiratory murmur is a little weakened generally. No added sounds arc detected. A skiagram showed and ;icrsonal medical history contain noth ing of note. He complains of occasional pain in both sides of the chest, and perhaps a little uoduc shortness of breath on oxcr- Fig. t.--Cases: Moderate fibrosis. Un due degree of striation and fine mottling in central zones of both lungs; calcified glands in mats, with rather coarse striation in upper lolies; ? interlobar pleurisy on right side, between the. Wtoer and middle lobes; emphysema at CSSS: -- tion. His color is normal. His muscula ture and nutrition ore good. Chest.--'There is no retraction of the apexes. Imt there is a slight llattemog below the right clavirle. The percussion note is slightly impaired generally, behind, partic ularly uu the right side. The bn-uth soumis nre-wenk. generally, and expiration is pro longed. No added sounds are delected. The skiagram (Fig. 1) shows ar. undue degree of slriatioo anil fine mottling in the ccnlrul zoncM of b.o.h lungs; calcified gluodn in the roots, with rather coarse striation in Vol. a No. 5 v*im *"** lr.* *% r j ftr F t \ 448085 ve---**"* ^iO* THE J0 UIIX \ L~ 0FrIXDU3T1U A L HYGIENE the upper lobes; ? interlobar pleurisy on the right side, between the lower and middle, lobes; and emphysema at tho bases. The case was diagnosed as moderate fibrosis. Case 5.--This woman, aged 40, has been employed for eleven years in asbestos, for most'of the period mattress making. Pre viously she was employed in a laundry. She has recently been ill for three months with pleurisy (no history of tapping); other wise her family and personal medical history* r* ..* I.* i~>CTTTT.^*- *. * mooerstc f.brc.7..-, 3u.-; f.jrl.vc toward the bases. JCa'e G,.--This worker, s forr.:.;?. &gcd 31, has been,employed in ast'estos for seven years, ^opening, sod has. Loco exposed* to much dust. Her previous employment &s non-ciusty. Her iatr.ily and personal history disclose nothing o: note, .line com plains of having had a eo-git (or five years, and of shortness of h.-eatn oa hurrying. She is thin and undcraourisncc. and pale. Fig. 2.--Case 6: Moderate, hut fully developed, fibrosis. Enlarged glands in both roots; diffuse fine mottling in both lungs, especially the rignt. Ftc. 3.--Case 7: General .e.bro*i*. mostly linear, but with little mottling of right lung. Old puerile tuberculous scars at apexes. are negative. .She complains of having had Oust is present o^*r-hair aad in her a winter cough for three or four years, and nostrils. --nn, -- ' of shortness of lireath on exertion since her Chctt.--She has a chest expansion of one- attack of pleurisy. Her nutrition is good; fourth inch. There is slight g-neral impair her weight is stationary. She has normal ment of the percussion note.,' definite at the color, and no cyanosis. apexes and the bases. The breath rounds Chat.--There is some general impairment are weak; expiration is slightly prolonged. of the percussion note over both lungs, be N'fi added founds,are heard. Her ;.rart is hind, more noticeable at the bases. The not enlarged, and no murmurs are d/ ireted. respiratory murmur is wrnkened generally. The skiagram (Fig. 2) shows a number of Persistent crepitations and medium riles enlarged elands in both root*, anti a diffuse arc noted low down in the right axilla. A fine mottling in both lung*. esporU.'Iy the it' skiagram showed diffuse fine striation anil right. This is a ease of moderate, but fully fine nodular mottling, with light opacity at developed, fibrosis. the bases. The case was diagnosed as Case 7.--This woman, aged 4S, his been J. I. ft. Xxy. twa 448086 "E larked toward the a fern aged 31, ibeitos .or seven been expo'H to oua employment dly and personal f note. She comigh /or five years, ith on hurrying, riihed, and pale. fibrosis, mostly igo/ right lung. > at apcxca. tir and in her nansion of oncgrnpral impair(iefinite at the breath sounds illy prolonged. Her heart is s are detected, s a number of i, and a diffuse especially the rate, but /ully d 43, has been J. I. II. 1930 1 PULMONARY FIBROSIS IN ASBESTOS WORKERS employed in asbestos for_thirty-two years--- cmployrd for twenty years in adicstns in about three_^years on _cards,., and the" re many capacities.. There is notiung of note mainder as a_sj)jnner. She has done no in his family history. He gives a history of other factory work. Her family medical pneumonia a number of years ago. His history discloses nothing of note. She has :omp!.-.:nts are: a little shortness nf breath a personal history of nephritis seven or eight on exertion for the last two or three years; years ago, causing three months' illness. otherwise none. His nutrition is-fAir only. Her complaints arc: shortness of breath on His color is fresh, but there is slight cyano hills, and winter cough for about years. sis of the lips, at times. Her nutrition is fair. She is rather pale. Chf.it.--The skin is poorly elastic; there Cheat.--She has a chest expansion of one- is some retraction of the a;>e\cs. There is half inch. No retraction of the-apexes is an impaired, rather "boxy," note on percus noted. There is general slight impairment sion, generally, especially over the upikt of the percussion note, behind. Breath half of the left lung, and over the upper two- sounds arc harsh and expiration is pro thirds of the right lung, behind, and io longed. No added sounds are heard. No front. Respiratory murmur is generally gross enlargement of the heart is noted, but weak. Expiration is slightly prolonged, the second sound is found to lie accentuated but diminishing toward the bases. Pleural over the aortic area. The skiagram (Fig. 3) crepitations are noted low down in the right shows a general fibrosis, mostly linear, but axilla. A skiagram showed a. definite fine with a little mottling of the right lung. diffuse fibrosis. Neither lung lights up very There are also very old pucriie tuberculous well, snd throughout both there is a very scars at the apexes. The case was diag fine diffuse reticulation and mottling-- nosed as general fihrosis. moderate, but fully developed, - fibrosis. This, case,^hould-bc.compared.-with..Ca5e The fine diffuse character of the radiologic Casc.6.lherc.waa aicavy-exposure. to appearances is particularly noticeable here. dust extcnding.oyer a.fc?y_ye_ar_s;.in the prrs- _Ca.se 10.--This man, aged 46, has been cnfccasc there was exposure to a very much employed for twenty-five years in asbestos, lcs3.conccntration.of,dust,_except.possibiy during nine"years of which lie wasnotex- in the first three years, but extending over _posed to- dust. For eleven years of {he nanv years. remainder he was employed in the card CaseS.--This worker, a male, aged 62, room, and mattress making. His family lias bce.iT employed in asbestos (or .twenty and personal medical history" disclose noth years as "a~*wcavcr. Hc__was. previously a ing of note. Ilis complaints are: shortness cotton~and* silk~weaver. His family'aod of breath on exertion for three months; personal medical'History show nothing of cough after a few hours' work in dust during note, except that he was regarded as a deli the last two or three years, with little or no cate child. His complaints are: shortness expectoration;Rt piia in the left side of of breath on exertion, and on going upstairs, the ehest fflTflle -last three" inont-hs. His for three years; morning cough and a little nutrition is good. He is pale; with slight expectoration for the last three winters. duskiness of the lips. He is thin and pale, with some cyanosis. Chat.--There is some retraction of the Chat.--Chest expansion is 1 inch; there apexes. The percussion note generally is retraction of the a[>xes. The percussion is impaired, and of a "boxy'' rhararter. note is impaired over both upper lobes, in Hreath sounds arc harsh and expiration is front, and over the upper two-thirds of (he prolonged over the right upi>er lobe; rise, right lung, behind. Expiration is pro where the respiratory murmur is a little longed at the bases. Pleural rub and inenn- weakened and expiration is not materially atant rules arc noted at the loft base, and a prolonged. No added sounds are heard. few rales at the right base. A skiagram The heart is normal. The skiagram (fig. showed a definite diffuse fibrosis with nodu- 4) shows diffuse striatum ami fine speckled lation. This is a case of fibrosis in the early mottling throughout both lungs--fihrusis, advanced stage. fully developed. Case 0.--This man, aged 41, has been Case 11.--This worker, a male, agnl 40, Vnl. 12 No. A 063 IQ 448087 220 THE JOURNAL OF INDUSTRIAL HYGIENE has been employed for twenty-two years in asbestos--during the first eleven years on cards,and.aa.a weaver, during which he was exposed to a considerable concentration* of _duat.__ During the remainder of. ihe time he was emqlqy.ed_.on. a non-dusty process, but was exposed to a less concentration of efust tidtiVedTrafn--bCher processes. His'family and personal medicnl history give nothing of note. His complaints arc: shortness of breath on climbing stairs for the last five years; slight morning cough and expcctors- Fxo. 4.--Case 10: Fully developed fibro sis. Diffuse striation and fine speckled mottling throughout both Jungs. tion for about tho same time; and slight aching of the chest in front, below the left clavicle. His nutrition is good. There is slight cyanosis of the face. Chest.--Chest expansion is 1 inch; there is retraction of the apexes. There is im pairment of the percussion note generally, most evident over the -whole of the right lung, behind, and over the right upper lobe ia front. The note is "boxy" over the remainder of the chest. The breath sounds are slightly weakened generally, except at the right apex, but there is no gross change. Expiration is prolonged ccocrnlly. Fine crepitations arc heard in both axillae, and over tire right up;"-r lobe, in front. The heart is normal, Sputum is mucoid, hut is negative for Bacillus tuberculosis. Club bing of the fingers has licrn noted for about two years. A skiagram showed &a exten sive diffuse fibrosis--fibrosis in a fairly advanced stage. .Case J3.--This worker, a male, aged Co, has been employed in asbestos for twmtyjsix.years.in the card room. Previously he was a-sawver's laborer. There is nothing of note ia his family and personal medical history. He complains of slight shortness of breath oa exertion of recent years, and of winter couch for the last three or four years; expectoration is stated to bo nil. His musculature and nutrition are fair. There is siicat cyanosis of the face. Chat.--Heha.; a chest expansion of threefourths inch. The percussion note is im paired generally, especially over the le'ft upper lobe in front. The respiratory mur mur is weakened over the whole of the chest except the left upper lobe, where there are whistling breath souads, and medium rdie*. The hear: is normal. A skiagram showed very extensive changes throughout the chest of a coarse type without fine stippling. The roots showed a choked appearance. There was heavy mottling at the base. One old tuberculosis focus was noted at the left base, and some calcified glands in the left hilum. The diagnosis was fibrosis in the advanced stage. .Case, 13.--This mao, aged CG,- lias been employed in asbestos for twenty-one years as a weav^rj_For about sixteen years pre viously he-was-a cotton and siik weaver. His father died of "chest tr.tjB8fe,rat the age of 43; his sister died agc3 to of pulmonary tuberculosis. He has oolv been away sick a week or two in twenty-one years, .and has never had asy serious illness. His com plaints are: undue shortness of breath t>n exertion "during the last two years; cough for the las: two or three winters. Expector ation is creamy, and occurs a fair amount of times. He has I<xst weight, and is thin. He is pale, but with some cyanosis of the face, and with a malar flush. Chest.--Chest expansion is li iaches; there is retraction of both apexes. Duines; is .detected o:i ['reunion over tho upper two-thirds of the right lung ami over the left 1 t. Th*1, but CIu*. ir about i extcn, fairly iged 60, twentyualy ho nothing medical ortacss rs, and or four be nil. -0 fair. f threci* irnne left y mure chest ere are n riles, showed e chest . The "There 'ne old 't base, hiluc vanccu a been year* ca .pro. eaiar- he age lonary sick a nd has 3 com-. . ath on_ poofth _ >ctoriunt of u He e face, chcs; uincss upper, he left J. i. it. ay, 1930 Ilia U I lul iiia. uti -i- O1 -<--j leul-le- ul uj CO^ j ljetiii la^ 1,. 1 it)i , UbU-- ^vmi r--* mi i 41 * i H urn 1111111 ---------' PULMONARY FIHK0S1S 'IN ASULSTOS WORKERS upper lobe, behind, and over both upper1 the sputum had remained .small in amount, lobes in front. Breath sounds are rather and its appenranee did not suggm tubercle. weak, with prolonged expiration. Scat "My diagnosis from tire bogituiitig was tered variable rhonchi and rales arc heard one of pulmonary asbestosis uuii possibly over the right lung, behind, over the left added tubercle. upper lobe in front, and over the left root. "f took two X-ravs of him, noithcr of The skiagram showed a definite diffuse which showed appearanres suggestive of "fibrosis plus tuberculosis. Sputum was tubercle, everything pointing to a very negative (one examination). The diagnosis extreme degree of fibrosis." was dust fibrosis in the advanced stage, with* lie died on Oct. 13, 1923. So postmortem tuberculosis, probably active. examination was obtained. Case 14.--This worker, a male, aged 36, commenced_work_. in an asbestos . piant ;rlfTr.4 l-.-Ac. irfTOlO, but was employed on other work untiLJanuary, _fQU._ .During.the next five IXnrs,. until_eariy_inJ919j about thrce_ycars and nine months were spent in army serv- iec^for_ninc_months_of _uduch .bc.was a-pcis- oner_of war,..but he had.,two.short periods of.wor_k in asbestos--eleven months in die weaving,, and six months in~~fhe mattrcls, departments. From early in 1919 ..to Xoj Comber, 1927, he worked In asbestos proc esses, but for only'Mx'yc'ars'ancftenmontTis ijTTaust/bno'fmattresslnaking);*-He then ceased work. He was rcferredlo a tubercu losis dispensary on Oct. 19, 1927, when he gave a history of bronchitis in 1916 and 1917 during the War, and of never being very well since; complaining of dyspnea, pain in the right side, and a slight cough of only about six months' duration, with a small amount of grayish sputum. Dr. N. Tattersall states that at that time: ___ "Dvspnoca was very marked, oven on Fig. 3.--Case 14: Massive fibrosis, wit It talking, and there was-definiU-cyanosis___ plcural.tliickcning, retracted apexes, and TT , , . ., pneumothornx on left side with incomplete He had marked hollowing and respiratory collapse of lung. .*' ~ retraction at both apices, especially the --rm* right; loss of note over most of the right lung and the upper half of the left; bronchial breath sounds at both apices; fairly numer ous crepitations, mostly on the right side, and a pleural rub at the right base, a systolic bruit at the apex and pleuro pericardial friction. "I examined him a number of limes, the last.occasion being April 20, 192S. In that time lie bad lost 9 pounds, felt very weak, and the dyspnoea was increasing. The signs remained much the same, I hough occa . _It will he noted that the length of exposure to asbestos dust is unlikely to have been more than about ten years and two months, and of this time he was employed `only about eight and one-half years in a dusty process." ""'tVar'service, of course, may have reduced Ids resistance. The .skiagram (Fig. 5) shows a massive fibrosis w itli pleural thickening, retracted a;x-.vcs, and pneumo thorax on the left side with incomplete col lapse of the lung. sionally, if lie got a cold, the moist sounds were more numerous, especially at' the bases. Seven sputum examinations were negative, and up to the time I last saw him N'o doubt, fibrosis of (be type pro duced by asbestos dust can of itself lead to complete disablement, and Vet. 12 Ho.J .* ihXr.v. "v 222 THE JOURNAL 01' INDUSTRIAL HYGIENE finally to a fatal termination, even in the absence of a superaddod tubercu lous infection. The primary cfTcct 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 are avoided. Ultimate! v, however, the margin of safety, already diminished, is lost and the circulation slowiv 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, and results in a fatal termination. (To be concluded) BOOK REVIEWS BtnivBiioirrtoor:. By Prof. Dr. Paul Schmidt, Director des Hycirnischcn InstitutK dor Univrrsitat Halle a. d. S.; Priv.-Doz. Dr. Adolf Scircr, Oberassis- lent am Hygionischcn Institut Halle a. d. S.; und Priv.-Doz. Dr. SlillfricH Lilsncr, Assistent an der Medizinischrn Klinik Hallo a. d. S. Paper. Pp. 79 u'i(h index, illustrations, and bibliocraphy. Berlin and Vienna: Urban <t Schwarzenberg, 1930. larly apposite. It brings the literal urc of the subject down to tbc prrsenr date and represents the mature thought of an investigator who has long made this field particularly his own. The discus sion of the diagnostic features of lend poisoning is especially clear and to the point. In this connection it is of in This monograph is divided into a terest to note that emphasis is placed short introductory or general section on the- importance of the determina and a special section. The first part tion of lead in the blood. is devoted principally to a discussion No attempt is made to discuss the of the outstanding diagnostic symp details of technic. The monograph toms of lead poisoning and of the work presents instead a critical review-of the done by Dr. Schmidt-and his collabora- more- recent experimental, work relat- lors in the microchcmical determina ing to lead poisoning and will, in con tion of lead in blood, urine, and feces. sequence, doubtless have a wide ap The second part discusses in detail the peal to all in--tiCij^ri. in thisdicid. usual..sources of lead'poisoning; the The bibliography ;*rrhieh- contains 2DS absorption, distribution, and excretion references to the recent work and of lead; the pathology' and clinical findr.--brings the literature of the subject ings associated with lead poisoning; down to 1930, is parttemariy valuable, and, finally, the diagnosis, prophylaxis, "Blgivergif-tung'' may well be reenm- and therapeutic treatment of lead poi- mended as a valuable addition to the soning. ---- -- library of stirrientsmf pubtiirtrcanii.-- Dr. Schmidt's monograph is particu- L. T. Fairhall. i. t. it. ; l`r.5> *- 448090