Document aJ0DqoL6vpjBQo50rMpOE112a

TABLE OF CONTENTS JUNE, 1930 Personal Qualities in Accident Causation. E. <3. Chambers, MA, Investigator for the Industrial Health Research Board, London................................................................................................... 223 Total Heat Difference as a Measure or Wet Kata Cooling. Walter S. Weeks, Professor of Mining, University of California.. 233 The Infectiv ity or Silicotic Tuberculosis. Patrick Heffeman, MJD., Tuberculosis Officer, Derbyshire County Council................ 236 The Occurrence or Pulsionart Fibrosis and Other Pulsionart Aftections in Asbestos Workers (.Condudtd). E. R. A. Mere* wether, M.D., H. M. Medical Inspector of Factories....................239 Book Notices................................................................................... .......... 258 Abstracts or Current Literature, Domestic and Foamon, with: Industrial Medicine, Surgery, and Nursing; Industrial Acci dents and Hazards; Industrial Sanitation;Personal and Community Hygiene; Industrial Investigations andSurveys;Industrial Manage- . ment in its Health Relations; Industrial Service and Mutual Benefit Associations; Workmen's Compensation and Insurance; Rehabilita tion of Disabled Employees (Abstract Section)................................. 107 In accordance with the policy adopted in 193S, the July and August issues wtil be omitted. i m32L 01-326 THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS (Condudett) E. R. A. Merewether, M.D. B. it. Medical Inrptcior of Faclorita Morbid Axatomt Professor M. J. Stewart of Leeds has kindly supplied me with & detailed description (dated March 2S, 1929) of postmortem appearances of several cases. From this account the follow* ins points are extracted: Tie gross morbid anatomy of this lesion, ss sees in persons who have been at work for many years in tha dusty atmosphere of in asbestos factory, consists in a widespread pulmonary fibrosis affecting especially the basal region of both lungs. There are ex* tensive, densely fibrous adhesions through* oat the pleural sacs, which may, indeed, be 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 fibrocartilage. 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. The distribution of the fibrosis, sport from the extensive basal lesions, is rather irregular, the peripheral, subpleura! regions of the lungs being more aiTccted than the central areas. In one ease in which the pa tient had been away from work for four yean (following nineteen yean in the mill), the 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. The totally fibrosed areas of lung show grayish-black mottling,-owing to immobili zation of carbon. This tissue is excessively denso 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 afieeted parts are definitely tougher than normal. In none of the eases was there any evidence of an active tuberculous lesioa. Histodogt The essential lesion is a chronic interstitial fibrosis of the lung. In the earlier stages, there is fibroblastic proliferation in the alveolar walls, which become increasingly thickened in consequence; and there is catarrhal desquamation of the alveolar epithe lium. At thisstageof thediseasepeculiar golden-yellow "asbestosis bodies" are found in varying, usually con siderable numbers, both in the alveolar spaces and in the thickness of their walla. Detached portions of bodies may often be seen engulfed by alveolar phagocytes, or a large unbroken body 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 still remain embedded in the fibrous tissue. Varying quantities of carbon are also present, chiefly in little masses as though it had been contained with in phagocytes. Chronic bronchitic K'a. 01 j 4 6 240 THE JOURNAL OF INDUSTRIAL HYGIENE changes arc present and all grades of dust, close resemblance in sizes, shapes, bronchiectasis may be seen, in cases and colors is apparent. There are the of long standing, from simply bronchial same black, blue, brown, and trans and bronchiolar dilatation, with walls lucent fragments. In fact it is easy still more or less intact, to large spaces to take such a single particle from the filled with pus in which the original lung and immediately find its brother bronchial walls have become converted in a slide made from the dust. more or less completely into fibrous and granulation tissue. Many of the Curious Bodies smaller arteries show obliterative end la addition to the fine granular dust arteritis. and larger fragments of asbestos, sec Reversionary metamorphosis of tions of the lungs show curious bodies. alveolar epithelium is frequent, and They am found in alveoli, bronchioles, such alveoli are often filled with fibrous and necrotic areas, and in albuminous fluid, in which clumps of phagocytes in sections of both lungs. "bodies" may be found. If a portion of lung is teased and Asbestos Dust et the Loras extracted with water, or digested with trypsin, or, as Professor Stewart Dr. W. E. Cooke has supplied pointed out (192S), if a smear is made (under date of June 25, 1929) details from the cut surface of the fresh lung, of his researches on asbestos dust in these bodies are seen in myriads. The the lungs, and on the constitution of larger bodies measure from 20 to 100 the curious bodies, which have been microns or more in length, and are of freely used in the following notes:-- a golden-brown color. They may Sections of lung and the results of have single clubbed ends or may digestion of the lung with trypsin appear as elongated dumb-bells: some show an enormous amount of fine are filamentous, while others suggest a black granular dust, much of which is series of disks. carbonaceous. In addition, there are Single coccal and spore-like forms, two striking features. The first is the and aggregations of these, and strepto almost complete absence of the fine coccal forms are not uncommon; the translucent spicules of fiber which color varies in the smaller types from a make up a great proportion of asbestos very pale yellow to a yellowish-brown. dust in factories. The second feature The bodies do not stain with any of the Is the presence of large fragments vary aniline dyes, but in chrysotile workers, ing in length from IQ to 360 microns. they give the Prussian blue reaction for They are found in fibrotic and necrotic iron in varying degrees of intensity. areas, singly and in groups. The These curious bodies have been found particles are so large--masses of them in every autopsy in pulmonary asbes- are seen in some sections--that they tosis. It would be unprofitable to must have occluded small bronchi and retrace all the steps which led down resulted in fibrosis of the surrounding many by-lanes during the course of ares. the work, but I will mention a few per Comparing these large particles in tinent details of interest. the lung with those found in asbestos Professor Stewart suggested to me / j. i. ft. JyiM. 1930 0iu47 PULMONARY FIBROSIS IN ASBESTOS WORKERS 241 that a better method tium simple extraction of the lungs with water or saline would lie to disrest portions with trypsin. During this process it was found that if the specific gravity was 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 ccncrifugaliring, neutralizing, and washing the deposit, the curious bodies could be obtained in a pure state. This was done, and sufficient material for Xray 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 partides and what appear to be pieces of quartz. Rclativciy few fine spicules are found; but curious bodies of all descriptions are present in enormous numbers. All these facts lead us to imagine the Ixxlics 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, aq 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 ox 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 place, syneresis occurs, and, with the loss of water, the adsorp tion is rendered irreversible. The adsorbent is permanently cnshcathcd with stable colloidal aggregates which become molded into the familiar VL IS .*te. 01,6 4 8 242 THE JOURNAL OF INDUSTRIAL HYGIENE shapes by alveolar and bronchial cur lymphatic glands; in material obtained rents. by lung puncture during life, first sug Support for this idea is found in the gested by S. A. Henry; in the sputa; fact that micro-organisms adsorb col and in smear preparations from the loidal material in the presence of blood cut surface of the lung. In smear serum and colloidal asbestos. Staphy preparations they can be readily lococci so treated appear as large demonstrated. round yellowish-brown disks; in the The importance of these findings process their property of stainins with lies in the fact that the bodies have aniline dyes is lost. The organisms never been found, as yet, in any other coalesce and form masses; and I human affection. That similar bodies think- it probable that some of the may he found to occur in the lungs of coccal and spore forms are similar workers exposed to other dusts, is orguiisos, quite possible, although they have not Finally, are the curious bodies been found in silicosis, nor were they diagnostic of pulmonary asbestosis? present, according to Simson (6), in Asbestos is unique among minerals in the fibrosed lungs of a hematite miner. being fibrous; and its dust, generated They appear within a comparatively during manufacturing processes, is short period of time after exposure to 1a unique. As can be imagined from asbestos dust; at the moment, their the formation of the curious bodies, presence in the sputa, in the absence there is no reason why, given any of clinical or radiologic evidence of pul silicosis, a fine spicule of mineral should monary fibrosis, cannot be taken os in 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 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 a diagnostic point of view. The con postmortem examination of a fibrosed ditions which, apparently, must obtain lung, has evident implications. 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 Professor Stewart, who is continuing his work on this subject, has devised the following method of examining sputum for asbestosis bodies: reason I believe that curious bodies, if found in any numbers, ore pathog nomonic of pulmonary asbestosis.-- W. E. Cooke and also Roodhouse Gloyne (20) have independently dem Half an ounce or so of sputum is added to an equal quantity of undiluted antifonnin. 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 onstrated the presence of a mineral core, evidently derived from asbestos fibers, in the curious bodies. The bodies have been found (Stewart and Haddow (21)) in the intrathoradc three or four hours. The bulk of the super natant lluid having then been decaated, the remainder is centrifuged at a moderate speed (or ten to fifteen minutes. The whole of the supernatant fluid is now poured off, aad the deposit transferred to an albumin- J.U. Jua. I MO 0'.J49 PULMONARY FIBROSIS IN ASBESTOS WORKERS 243 Ucd slide, by means of either a platinum loop or a pipette. After thorouch dryinc on a hot plate and final fixation over a buosea burner, the film ia very gently washed in water, dried, and mounted in Canada bal sam. After a little experience the aebeetoris bodies am readily picked up with the low power, and their true nature ia then eonfirmed with the 1-inch or oil immersion lens. As a rule they am present in very small num bers, perhaps only one or two in a whole film. In the ease of some of the older workers, however, numerous bodies, up to one or two per field in certain portions of the film, have been found. It is obviously necessary to cleanse thoroughly ail glass ware, etc., used in making these examina tions; otherwise there is a risk of contami nation of subsequent specimens. The films can be treated with hydro chloric add and ferrocyanida of potash to demonstrate the Prussian blue reaction given by the bodies. AaBESTOSIS AX OCCUFATIOXAL Hazard Out of & total of 374 workers exam ined, 105, or 23.1 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 coses in which previous work in dusty occupations (e.g., quarrying, coal mining) may have been the prime, or a contributory, factor ia the develop ment of the fibrosis, ninety-five, or 26.2 per cent., of 363 workers were found to be affected with pulmonary fibrosis due to the inhalation of asbestos dust, and a further twenty-ooc, or 5-8 per cent., showed precursive signs of thia Thia percentage may well be com pared with the corresponding figures found by Middleton (22) in his exami nation of metal grinders (4C.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 oi 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 rotes 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 v* n No.* 0 -o 0n 0 I i 244 THE JOURNAL OF INDUSTRIAL HYGIENE 39 and 50 to 50 have incidence rates of fibrosis in age group 20 to 29, has been 30 per cent, and 37.9 per cent., respec shortened by increased susceptibility tively--not a wide difference, since the at ages under 20. As, however, the groups include workers in various average age of this group of cases of processes exposed to different concen fibrosis is 26.7 years, and also because I trations of dust Moreover, the aver the establishment of fibrosis docs not age length of employment in these two necessitate immediate retirement from groups, excluding the cases of fibrosis, 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 I WAS LONGEST EMPLOYED noezu SCO* EXAJOKED casks or rta mis No. Per Cent, of Group ATOUGE LE2TOT8 OF zacnoTuxKT ne rss* Group Less Cases of Fibrosis Cases of Fibrosis L Crushing, opening, disintegrating, and mixing............ 2. Carding.................................... 3. Spinning, twisting, doubling, * plaiting, etc........................ 4. Mattress making.................... 5. Wearing and associated proc- WM.............................. a. Cloth wearing................... 23 b. Band wearing................... 21 e. doth and band and un- classified weavers............ 14 d. Warpers, headers, loom tuners, charge hands, and others associated with wearing.................. 25 6. Miscellaneous processes and 21 9 39 10 42.9 41.0 8.9 10.9 9.1 13.2 37 12 13.8 10.1 18.7 15 7 40.7 7.3 13.0 83 40 45.5 10.0 12.7 21 75.0 9.5 14.1 4 19.0 10.9 13.5 4 23.0 7.2 9.5 U 44.0 11.2 10.5 workers................................ TotaL.......... .-........................... 24 274 u 95 45.3 34.7 8.8 13.8 9.0 13.5 Is also similar, but considerably less than the average length for all the eases 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. Tabic a shows the distribution of 274 workers examined, and of those with fibrosis, according to the process UK. t JlUM. ISM i 0 j. o o 1 PULMONARY FIBROSIS IN ASBESTOS WORKERS 245 in which they were longest employed. remains longer in the milder, and This was a compromise necessitated radiologically linear stage. by the common customs in the indus This view is evidently of consider try of having several different processes able practical importance since it sug going on in the same room, and of gests that in such cases, the rate of workers transferring from one process accumulation of dust in the lung has to another. Since the intention was not greatly exceeded the rate of elim to obtain some measure of the relative ination, the changes still being centered incidence of fibrosis in workers in the in the main lymphatic system. various processes enumerated, and If this hypothesis is accurate, it since no case of fibrosis clearly due to should follow that in order to prevent asbestos dust was found among eighty- the full development of, the disease, nine workers examined, who had been among asbestos workers, within an employed for less than five years, in average working lifetime, it is neces clusion of this group of workers would sary to reduce the concentration of only have introduced a varying source dust in the air of the workrooms to a of error. figure somewhat below that pertaining The processes differ, some very to spinning at the present time. materially, in the amount of dust Fortunately, also, the spinning which they cause, and consequently in group is the largest individual group the amount inhaled by the operators in this section of the industry--e.g., (30). The outstanding point brought out of over 400 workers employed by out by Table 5 is the relatively low one firm, this group accounts for more incidence rate of fibrosis in "spinners" than one-third. (group 3), as compared with each of Although all workers examined who the other groups. They are corrobo have been included as spinners have rated by counts of the dust particles been engaged in spinning, or in simi in samples of air, a number of which lar processes for convenience termed have been taken and are discussed "spinning," for a longer time than on under Dust Risk. any other process, only a few have been There is also some indication in these employed solely on spinning, and in figures that not only arc "spinners" workrooms where no other, and more less likely to develop fibrosis, but when dusty processes, were being carried on. they do, it takes longer to develop. These two factors, prior work in Study of the radiograms suggests that more dusty processes and present in such cases (t.e., in the less dusty work in proximity to more dusty proc processes) the resulting fibrosis is, for a esses--especially the latter--have had, considerable period, much more linear it is believed, some effect in raising the in its radiologic features, and shows incidence rate of fibrosis for this group. less mottling. The iiistory and clinical features in these cases, and the com Dust Risk parative dust counts, all contribute to In an effort to obtain additional data the view that with comparatively low on the influence of concentration of concentrations of dust, the resulting dust in workrooms, a number of sam fibrosis is longer in developing and ples of air were taken and the dust eon- VoL n s. i 0 o D .. 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 are opening (with old-fashioned teasers), sieving (with no local exhaust ventilation), and shoveling, or otherwise handling asbes tos fiber. The heaviest counts of all were found 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. Further counts are necessary to estimate this. Weaving cloth wet, not merely damp, reduces the dust count to a remarkable degree. The figure for band (La, narrow) weaving, wet, is not accurate since it was raised by dust from a neighboring dry doth loom; still the improvement due to wet methods is 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 conics mattress making, without any precautions such as ex haust ventilation, or damping floors, doth, and tables. Application of ex haust ventilation and damping reduce the count considerably, but it is be lieved that the figures are too low, since counts for some subsidiary processes such as buttoning, sewing, and cutting out are not available. The figures for spinning, plaiting, and braiding ore 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 aeicular 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 80 per cent.; in ten, SO to 90 per cent.: and in six, 90 per cent, and upward. When the counts were analyzed ac- vt a fU. OiJuC I 250 THE JOURNAL OF INDUSTRIAL HYGIENE cording to the 7.5-micron standard, all the cases of fibrosis found, thirty-six twenty showed 90 per cent, or more of had been employed in asbestos for the particles to be of this size or less. periods ranging from a to 10 years; With regard to the effect on the two of these cases, one employed for 9 lungs of different varieties of asbestos, years and the other for 7 years, show no evidence was found to indicate that that a considerable degree of fibrosis any one of its varieties is more potent may occur with less than 10 years' in producing fibrosis than the others, exposure. other factors, such as concentration of F. W. Simson (6) examined the lungs dust, being equal. There is now no of a guinea-pig which had been experi doubt, however, that both chrysotile mentally dusted by Mavrogordato for and crocidolite will produce fibrosis; two hours a day on each of fifty days while the third, the comparatively between February and April, 1925, newly discovered amosite, resembles and which died from other causes in crocidolite so closely in its chemical December, 1927. He states that his constitution, and in the characteristics tologic sections showed a slight gen of the dust, that there can be no eralized fibrosis: This observer also reasonable donbt, also, with respect examined portions of the lungs of two to it. native asbestos mill workers; one had Length of Dust Exposure been employed for twelve months and hod died from a miliary tuberculosis, No case of diffuse fibrosis clearly and the other, employed for two years, due to asbestos was discovered with had apparently never recovered from under 5 years' employment Three on attack of lobar pneumonia a year cases were found with 3, 3}, and 4} before death. years' work, respectively, who showed In commenting on the amount of clinical signs of fibrosis. Definite fibrosis found, he states that "a com confirmatory radiologic evidence was parison between the human cases and obtained in the first, definite but the experimental animal showed that slighter radiologic changes in the sec the fibrosis was more rapid and exten ond, and indefinite suggestive changes sive in the human cases than in the in the third. The previous occupation experimental animal." and, again, in the first case was fins weaving for 18 that "the amount of fibrosis in two of years; in the second, coal hewing for the human cases .... was quite 16 years; and in the third, work in an definite, and. if due to the presence of iron foundry for 1 year. All these asbestos dust, the initial rate of pro occupations are dusty; and in the last duction was rapid when compared with two there may be some exposure to present-day noo-infective silicosis on free silica. Also increased silica con the Rond." tent has been found in the lungs, after Experiments by Professor Beattie, incineration, of flax dressers. For in 1912. demonstrated that the lungs these reasons, these three cases could of guinea-pigs exposed to asbestos dust not be certainly ascribed to asbestos for forty-three and sixty-seven hours dust, although it was, probably, at showed "definite cellular proliferation, least a contributory factor. Among though not very extensi ve, and this is ;. t. h. Jun*. 1U0 0iC37 PULMONARY FIBROSIS IN ASBESTOS WORKERS 251 certainly a preliminary stage in the production of fibrosis." These pathologic and experimental findings suggest that the inhalation of asbestos dust rapidly causes some changes in the lungs. But no evidence was obtained that asbestos dust can produce an acute type of fibrosis com parable to that formerly noted in South Africa after repeated exposure to massive concentration of free silica, a few cases of which have occurred recently in Great Britain, causing death 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. The nature of the work, however, in the majority 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 at work --with occasional intermissions, lat terly, due to exacerbations of bron chitis--until the condition is advanced, although he suffers increasing incon venience from shortness of breath on the slightest exertion. Usually these cases cease work a year or more before death, but sometimes a terminal bronchopneumonia, or other acute infectioa, commences while they are still at work, and there is no long period of invalidism. PolaUlies Particulars of eight deaths have been collected, and arc summarized in Table 7. Ia six of these, advanced pulmonary fibrosis was the primary cause of death. In the remaining two cases, pulmonary tuberculosis was a contributory factor. In six of the eight cases the diagnosis was verified by postmortem examination; in the other two cases, confirmatory radiographic evidence was obtained. Information has recently been ob tained in regard to three other cases, in which death occurred in 1929. The details of one have been published by Wood and Page (25). Postmortem examinations have been made in all three cases, and in all, $he presence of pulmonary asbestosis, without tuber culosis, was verified. In one case, the pulmonary fibrosis was the primary cause of death; in one, information as to the extent of the fibrosis has not yet been obtained; and in the third case, a lobar pneumonia was superimposed on the fibrosis. It is not suggested that these few fatalities, in which the cause of death has been verified by strict inquiry, are any criterion of the true effect of the disease on the mortality rates of asbestos workers. Others are known to have occurred in which the exist ence of the asbestos fibrosis has been determined in life, but no postmortem examination has been possible. Difficulties in Diagnosis Many factors have contributed to impede both the recognition of indi vidual 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 tfe.4 0 id 58 / 252 THE JOURNAL OF INDUSTRIAL HYGIENE 0 i <J 5 9 Arrangement of dales follow * tlie American custom --i . t . , m antli, day of m onth, yoar. * Estimated. PULMONARY FIBROSIS IN ASBESTOS WORKERS 253 carried off by some intcrcurrent dis ease--which alone is noted on the death certificate--arc all of importance. A concrete example encountered during the inquiry will illustrate one of these points. J. C., Case No. 7 in Table 7, was known by ills own doctor and by the Chief TubcrculosisOfficcr of the town to be affected with advanced fibrosis of the lungs. Four or five months before his death it was thought that a change of air would be of advantage to him. Through the gen erosity of the firm with which he had been employed, he was transferred from the 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 ease chronic bronchitis was given as the cause of death. In the less advanced stages of the disease, the symptoms arc so unob trusive that the worker rarely consults his doctor. In the later stages, bran* ehitis, 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 os 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 same time the largest. Thus only now the existence of a health risk in the industry is beginning to be recognized. Does Asbestos Dcst Predis pose to Other Pcliionary Diseases? The important question as to whether asbestos workers show an in creased liability to other diseases of the lungs, such as pneumonia, pleurisy, and pulmonary tuberculosis--espec ially the 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 War), 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 hod diffuse fibrosis, and in one the lungs were normal. Of the remaining ten, one had a thickened pleura, two bronchiectasis, two diffuse fibrosis, one vt. 13 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 dinuse fibrosis, repre senting 32.6 per cent, of the fibrotic group, and eight were in the prenbrotic stage (33.1 per cent, of that group). The fact that the clinical examinations were conducted during the wanner 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 post 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 are not uncom monly found in quite healthy persona, and are of no importance unless it is shown that the inhalation of asbestos dust is associated with pulmonary tuberculosis to an increased degree, when such cases, as indicating a group of workers with a latent infection, would assume a greater significance. No dose 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 examined, fourteen, or 3.7 per cent., gave a family history of tuberculosis. Evi dence of active pulmonary tubercu losis was present in three; in two of these three the source of infection appears to have been a near relative. Thus, no outstanding susceptibility to pulmonary tuberculosis was 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 1.1 H. JilM, 1930 0 j. 6 G - PULMONARY FIBROSIS IN ASBESTOS WORKERS 255 may or may not accept sanatorium produce a serious and even fatal degree treatment. Tlius there tends to be a of pulmonary fibrosis. drift of such cases front the fibrosis 2. The type of fibrosis produced, producing industry. however, exhibits a number of diverg During the course of the inquiry, ences from that caused by the inhala information was obtained of a ntuttber 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. The divergences noted so far are s&natoriums, 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 It 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. It follows, therefore, that an tibilitytothe supervention of other 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 arc 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 grams. Asbestosis aj.t> Silicosis Contrasted 3. 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 be productive of this fine type of they are both varieties of fibrosis of fibrosis in varying degree. the lungs caused by the inhalation of dusts, it seems desirable to summarize SuiOlART shortly the main points of similarity 1. There is a definite risk of tho and dissimilarity between the 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, under halation 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 wa No. 0 xJ G 25G THE JOURNAL OF INDUSTRIAL HYGIENE length ol 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 & corresponding variation in the rela tive risk of the development of fibrosis in the workers in these processes. 4. With continued exposure to high concentrations of dust, the disease may be fully developed in seven to nine years, and may cause death after about thirteen years' exposure, exceptionally in a shorter period. 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 ore 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 gratciully tendered. In addition to those already referred to, the writer is beholden especially to Or. 3. A. Henry, who did much to facilitate the inves tigation, particularly by his 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. W. E. Cooke of Wigan and Professor if. J. Stewart of Leeds for pathologic mate rial and for much information as to the progress and results of their own researches into the grass 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 lead the aid of his Deportment, 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 sation for Industrial Diseases. Min utes of Evidence, Appendices and In dex, 1907. Cd. 3490, p. 127; Report, 1907. Cd. 3193, p. 14. 2. Cooks, W. E.: Fibrosis of the Lungs Duo to tho Inhalation of Asbestos Dust. Brit. Med. Jour., 1921, 3, 147. 3. Cooxx, W. E.; Pulmonary Asbestosis. Ibid., 1927,3, 1024. 4. McDomau), S.: Histology of Pulmo nary Asbestosis. Hid., p. 1025. 5. Seiixr, H. E.: A Case of Pneumoconio sis. Result of the Inhalation of Asbestos Dust. Ibid., 1923, 3, 932. 8. Snisox, F- W.: Pulmonary Asbestosis in South Africa. Ibid., 1923. /, S35. 7. Royal Commission on Metalliferous Mines and Quarries. Second Report, 1914. Cd. 7478, p. 146. i. it. Jurn. 1930 0 a3 G PULMONARY FIBROSIS IN ASBESTOS WORKERS 257 8. Baouam, C.: Notes on a Fine Type o( Fibrous rnoumonokoniosis Produced by Silicates an<l Other Minerals. Studies in Indust. live. No. 13, Rep. Dir.-Gen. Pub. Health, New South Wales, for 1937, Section I.-E, Indust. Hjrg., p. 102. Svilney, 1929. 9. Claus, W. I.: The Oust Hazard in the Abrasive Industry: Second Study. This Jocr., 1929, ff, 92. 10. Pancoast, H. K-, A.NO Pendergrass, E. P.: Pneumoconiosis (Silicosis). A Roentgenological Study. New York, Paul B. Hoeber, Inc., 192G, p. 153. 11. Thoumon, L. R., Brunoage, D. IL, Russell, A. E., and Blooueielo, J. J.: The Health of Workers in Dusty Trades. I. Health of Workers in a Portland Cement Plant. U. S. Pub. Health BulL No. 176, 1923. 12. GoADa-r, K. W.: Fibrosis of the Lung in Iron Miners. Jour. Roy. Mier. Soc., 1925, p. 432. 13. Annual Report of the Chief Inspector of Factories and Workshops for 1923, p. 94. London, H. hL Stationery Office, 1929. 14. Pxsnt, F. W.: In "Industrial and Manufacturing Chemistry" by G. Martin. .1917, Part 2, p. 2S1. 15. Compiled by AtbtaUn, a monthly trade journal published in Philadelphia, Pa. lft. Annual Statement of the Trade of the United Kingdom, for 1922 and 1927. London, H. M. Stationery Office. 17. Departmental Committee on Compen sation for Silicosis dealing with the Refractories Industries (Silicosis) Scheme 1919. First Report, 1924, p. 29. 18. Stars, A. R.: Silicosis among Rock Drillers, Blasters, and Excavators in New York City. This Joint, 1929, It, 39. 19. Wooo, W. B.: Pulmonary Asbestosia. Tubercle, 1929, 10, 333. 20. Glotnz, S. R.: The Presence of the Asbestos Fibre in the Lesions of Asbestos Workers. Ibid., p. 404. 21. Stewart, M. J, as# IIaooow, A. C.: Demonstration of the Peculiar Bodies of Pulmonary Asljcstosis ("Asbestosia Bodies") in Material Obtained by Lung Puncture and in the Sputum. Jour. Path, and Beet, 1920, 33,172. 22. Macslin, E. L, and Midoleton, E. L.: Report on the Grinding of Metals and Cleaning of Castings with Special Refcrcnc# to the Effects of Dust In halation upon the Workers. London, H. M. Stationery Office, 1923. 23. S<mrERLA.vD, C. -L, and Bryson, S.: Report on the Incidence of Silicas is in the Pottery Industry. London, H. M. Stationery Office, 1926. 34. Sctkehland, C. L, Ajrp Brtjon, S.: Report on the Occurrence of Silicosis among Sandstone Workers. London. H. M. Stationery Office, 1929. 25. Wooo, W. B, arm Pace, D. 3.: A Case of Pulmonary Aabestoaia. Tubercle, 1929, 10, *37. For the geologic and the manufacturing and industrial aspects of asbestos, tee: 28. Chisel, F.: Chrysotile-Asbestos, its Occurrence, Exploitation, Milling, and Uses. Second edition. Ottawa, Govt. Printing Bureau, 1910. 27. Asbestos, its Sources, Extraction, Prep aration, Manufacture and Uses in Industry and Engineering. Berlin, Becker and Haag, 1923. 23. Thome, E.: A Dictionary of Applied Chemistry. London, Longmans, Green & Co^ 1912. 29. Ae6te(oe, a monthly trade journal pub lished in Philadelphia, Pa. For description of processes, and further discussion on the incidence rate of fibrosis, and effect of work in different processes and also preventive measures, ir: 30. MncwESHEH, E- R. A., an Price, C. W.: Report on Effects of Asbestos Dust on the Lungs and Dust Suppres sion in the Asbestos Industry. Lon don, H. M. Stationery Office, 1930. Tel. a He. t 0iJ(3