Document vmkLRk9vnr3pxv1jpaK5beXb

i Vl. 12/1406 i ' >ii '} M| 5. * i l 1i I * .i J < 4 ** `> *1 i.tii l-i >' ! t v . ;j .H . i -i. f`; ' v,: >. t 4 f. , ! 4 4t \ pufmonaru ^jbiiabifitu in ^^llbeltod l/Uorb onciry. cJLsuaoiucy. erd i MHNITH W. SMITH. M.D, Hvm Tri Asbestosis has been described in detail in numerous published articles and texts. While it is true that cases oi tar-advanced asbestosis -nay have severe pulmonary disability, relarively iew ot the oeoole exoosed to rhe nr>^neveioo the mwxse. ihereiore. >t is the intent in tms paper to mention asbestosis only briefly and then to outline various other pulmonary disabilities seen among asbestos workers. The word "asbestos" is generally used to describe several fibrous magnesium silicates which are different in their chemical compo sition and physical properties. The most important types oi fibers are chrysotile. amosite. croddolite.-anthophyllite. acnnolite, and tremolite. Total world production oi all fibers last year amounted to slightly more than 1.300.000 tons. Approximately 95`fo of the fibers produced were oi the chrysotile variety. ,3fo croddolite, and 2% amosite. Deposits oi various types oi this mineral are found in many countries, but the largest mines are located in Canada and Africa. Asbestos fibers are highly resistant to heat and adds. They have great tensile strength and large surface areas. Because of these properties as well as their filamented struc ture, industrial use of these fibers through out the world is increasing. The textile in dustry has used them for many years to produce blankets, clothing, threads, ropes, apes, braided tubing, and filters. In recent years, however, there has been an increasing use oi asbestos in the insulation, building, and friction-material trades. In addition, the Recorded for publication April 7. 1955. Medical Director, Johne-Manville Corporation. fibers can be found in paper. wallboard._ shingles, pipe covering, floor tiles, brake linings and brake blocks, cements, putties, and plastics. It should be noted that the iacts presentee here apply to those persons who have Ue-n exposed only to asbestos fibers and to no other dusts. .As previously indicated, industry today is finding many new uses for the fibers when they are mixed with other dusts. It is an established fact that when asbestos fibers are mixed with silica, diatomaceous earth, or other potentially toxic dusts, the pulmonary changes -esulting from the ;niialabon oi these mixtures are not typicai oi asbestosis. The x-ray pattern may be differ ent. the clinical course changed, or the sus ceptibility to imercurrent infection increased or decreased. Thus, in making a diagnosis oi occupational pulmonary disease, it is highly important to obtain a detailed occupa tional history, so that asbestosis, silicons, or mixed pneumoconioses can be differentiated. The statements and observations reported here concern several thousand men and women employed in the asbestos industry in Canada and the United States. In this industry the various mining, milling, and manufacturing operations create some dust containing asbestos fibers. If the fibers up to 50m in length are inhaled continually in sufficient quantities over a period of several years, a typical pulmonary fibrosis wii! develop. It has been demonstrated that this fibrosis is due not to the chemical but rather to the mechanical action oi the fibers.1 The asbestos fibers are deposited in the terminal bronchioles, initiating a tissue response which coats the fiber and eventually produces what is known as the asbestos body. This appear* to be a defense mechanism oi the lung N"* merous asbestos bodies can be found in the 198 ? n s ti si U 41 01 ar in A A i DISABILITY IS ASBESTOS WORKERS jpurum of persons who have had only short ard sporadic exposure to the dust. These persons are healthy and have no demonstra te signs or symptoms of asbestosis. There10re. it seems more appropriate to use the ion> "asbestos" bodies rather than "asbestofts" bodies, signifying exposure to the libers but tsot necessarily indicating disease. If increasing quantities of the fibers are cocnnuaily inhaled, the tissue reaction pro gresses. and a generalised, diffuse fibrosis gradually appears throughout the lower lobes oi the longs. With additional exposure, this ated with this disease, which may account for the "ground glass" partera which has been used to describe the typical x-ray picture. In moderately advanced, or second-stage, asbestosis (Fig. 2), the infiltration has in creased but still is confined to the lower lung fields. The "ground glass" pattern is Fif. 1.--Early ubestotis. librosis will spread to the other lobes, even:uailv causing respiratory embarrassment and anally cardiac failure. The pulmonary fibrosis resulting from prolonged inhalation of asbestos fibers will produce a typical x-ray pattern. In early, or nrst-sage. asbestosis (Fig. 1), the x-ray rnous a fine, diffuse, homogeneous infiltra tion throughout both lower lung fields. It should be noted that this infiltration is bi metal. that it is generalized at both bases, *d that the nndnlae conglomerate patterns of other pneumoconioses, such as silicosis, ar not seen in asbestosis. There is a con querable amount of pleural reaction associ 199 w, %1-1 a. a. a. ARCHIVES OF INDUSTRIAL HEALTH more apparent, and the hart borders are Gregoire * has reported that pulmonary becoming indistinct or shaggy. There is some function studies on asbestos workers have irregularity of the diaphragmatic outlines shown that the chief physiological problem and beginning obliteration of both the cardio* is that of a "tight'' lung. The vital and phrenic and the costophrenic angles. maximum breathing capacities are lowered, In far-advanced, or third-sage, asbestosis (Fig. 3), the infiltration still is homogeneous and bilateral, has spread to the middle and possibly the upper portion of the lung fields, but the apices remain clear. The cardiac out line is almost completely obliterated, as are the domes oi the diaphragm and the costo phrenic sold. With this picture in mind, it is advisable to reiterate the observations oi many physicians, namely, that the x-ray pictore should never be used to estimate the expansion of the lung is difficult, and arterial oxygen saturation of the blood is diminished in some cases, indicating an impairrirent ot gas transfer through the lung. Diffuse ob structive emphysema, so commonly seen in silicosis, is not apparent in asbestosis. These pulmonary function studies are of imporunce in the proper diagnosis ot pulmonary fibrosis and the estimation of pulmonary disability. Of more importance is the fact that these tests can often help the clinician in directing presence or the extent of impaired pulmonary the treatment of the case. Umortunate.y, function or disability. Many cases with x-ray there are too few persons who are proper!/ evidence of third-stage asbestosis have been qualified today to carry out these tests known to carry on their usual work and live interpret the results. fairly comfortable lives for several years. An x-ray survey was made oi ooe group On the other hand, no case of definite dii - ot 708 employees working in an asbes"'* bility has been seen unless there was me mill where the ore was dned. crusned. se* typical x-ray pattern. arated and gTaded. packed, and then shier There is no typical clinical picture for asbestosis. The disease is insidious in its onset and slowly progressive with continued inhalation of the fiber. There is a gradual increase in cough and expectoration, some anorexia and weight loss, then slowly in creasing dyspnea. Cyanosis and dubbing of the fingers are rare findings. There is evi dence that asbestosis will not progress after exposure ceases, but this seems to be true only if the worker does not develop an intercurrent pulmonary infection. It will be shown that asbestos workers are not predisposed to develop more intercurrent pulmonary infections than are found in other workers. However, when an acute pneu monitis develops in the presence of an estab lished asbestodc fibrosis, the infection is slow to heal, relapses are frequent, and the patient may be more susceptible to subse quent pulmonary infections. While it is true that the disease is slow and insidious Operations in this plant required the r ployees to rotate through various jc hence it was impossible to relate any x changes to a particular job or to a specne. dust concentration. At the same time it couid be assumed that all members oi the group had been exposed to varying concentrations of the dust. The chest x-rays oi these em ployees were divided into three broad groups: (a) essentially normal lungs; (b) marked linear exaggeration fp-2) but no typical pattern of asbestosis. and \c) desinite asbestosis. Table 1 shows that of the 708 employees studied 649. or 91%, had normai x-ra>. This is of interest because 204 employees, or 29% of the total group, had 10 or more yean of service, and 2 men actually bad wonted more than 40 yean in the dust. Table 2 indicates that 52 of the 708 em ployees showed a marked increase of ail peri bronchial markings, although none had dea- in its onset and that people with advanced asbestosis may lead relatively normal lives, eventually the heart begins to (ail, and death from cor pulmonale rapidly follows. Grrfoirt, F : Pulmonary Function Snjeie Men Exposed for Ter or More Year* -o 'r.m*o< of Asbestos Fibers, read before the levrntn SW' nac Symposium, 195? (aapaoliated.*. *i LXCSARY DISABILITY IS ASBESTOS WORKERS Tailx l.--Emflcytti wuh SormwJ X-Rajt m -- n............................................................. v* m i*>u imi |M| i| M................................ ....... w ui m e site asbestosis. Inasmuch as the majority o< these men had essentially normal x-ray p>>m early in their employment history, it u assumed that most of the later increased Inst markings were associated with their subsequent dust exposures. Further indica non oi the length art exposure necessary to develop x-ray changes is seen when it is noted that 69% oi this group had 10 or more years of exposure. Table 3 shows that of the 708 employees T had developed definite x-ray evidence of asbestosis. These men exhibited various stages oi pulmonary involvement, but all were working steadily at their accustomed ob- 'nth no signs of disability. It is of interest to note that none had developed x-ray evidence of asbestosis with less than 30 years of exposure. Frequently it has been stated that it takes from 5 to 10 years of exposure to develop asbestosis. The survey reported here con cerned mill employees. It is possible that ther operations might have different expo sures with other disease experience. Factors which might influence this experience are not oniy the length oi exposure or the concentranon of dust in the air but also the fan that there is probably an individual suscep tibility to the development of pulmonary fibrosis. Medical literature has given considerable mention to occupational pulmonary disease, ton ven- little has been reported on the oc currence of nonoccupahonal respiratory dis ease among those employed in the dusty trades. The following survey was made in order to determine the incidence of nonoccupational respiratory disease in another group, of 1561 men and women, working in the asbestos industry. A review of absentee records indicated that no valid conclusions could be obtained from this source, because the reason for absence was given by the employee himself. Sickness often was used as an excuse to cover short absences for a variety of personal reasons. It then was decided to study the claims submined for sickness and accident insur ance. All employees in the survey participated in a plan operated by an independent insur ance company. Indemnification was made oniy after the nature of the illness had been certified by the treating physician. The study included claims submitted over a three-vear period for such illnesses as the common cold, sinusitis, pharyngitis, grippe, bronchitis, pneumonia, asthma, and pleurisy. Occupational respiratory diseases and pul monary tuberculosis were excluded in the report. Table 4 shows that of the 1561 employees in the survey group there were approxi mately equal numbers in dusty and nondusty occupations. Of all claims filed for respira tory diseases. 45% were for employees with dust exposure. Clinical observations for many yean had given the impression that a dusty occupation in itself would not predispose a person to more nonoccupational respiratory disease than would a dust-free job. This survey shows that the rate of disease over TaSLZ 2,--Emflay/rj with P-2 X-Ray Rrodmfi |T............................................................. 14 M ISIS k IMI mo* to-M IM r--urt. m........... .......................... I U I i u * i 1 0 1 Tails 1--Emyloytu wuk Artxjtaru rr-- 14 M u isis imi mu m-m -m m it t i i l i i 201 r A. it. A. ARCHIVES OF INDUSTRIAL HEALTH a three-year period wu approximately the same ia the two groups. In addition, there was no appreciable difference in the duration of illness in either group. Animal experiments and clinical observa tions have shown that asbestosis does not predispose a person to the development of pulmonary tuberculosis, nor does it aggra vate an apparently healed tuberculous lesion. In two isolated oneModustry towns in the Province of Quebec where asbestos was mined and processed, the incidence of tuber culosis over a period of many years was no greater than in other isolated towns with comparable populations but without a dusty Fig. 5.--Electron micrograph, amotiu aibcs* to*: x 4000. Fig. 4.--Electron micrograph, chrysodle asbes tos: x 4000. rrade.f In addition, the incidence of tuber culosis among asbestos workers was lower than that among the general population c.' these mining towns. Cnorlj^ne r>T'.<nu'T>t -*1^ -lirF----i-Tnt --non> make u evrremelv dif^fult to connrm or ucnv conclusively the causal reiationsnio asoestosis ana ornnorm o the lune. T*-otten a common conclusion is drawn :ro> observations and experiences wuh differe racial groups, living m different parrs "oi the world under vanable socioeconomic condi tions and working in diverse occupation!' exposures. To these variables shouia ix added the tact that there are various types of asbestos ribers. Fig. 6.--Electron micrograph, croadolite aiocetot: x 4000. t Parrot. P.: Personal comnranicaaon to the author. TaBLX 4.--Nonotc*ftioal Durajt Esfmmec taWiiw, MUl m................................................. Eapiereee *itt trpeeuie............................. trename eita bo dan czpoeuie........................ Clua* lor raewreiorr dleeew.............................. Otlm* for reeptreiorr -Hot-- vita >tuat * poeure .............. ~CI*rou for rNerretorf .lUaea* >tn eo Juai tipoion ............................................... Vjc m ru JT U l limn Inift of *fte >iu<t poeure. ............................................................... SJ Artriffi iHin of sliMan rill ad liuil resown. *e........................................... SI jCSARY disability /.v asbestos workers BadoiUrt Z has reported that there axe ^crai oinerent types of asbestos fibers used ; industry today, and these fibers have rent physical and chemical properties. . ,,ures 4. 5. and 6 are enlarged electron micrographs of three types ot fibers used toast commonly in industrial processes. The long, sort, and silky chrysohle fibers are iound chiefly is Canada, while the amosite ind crocidolite fibers which are shorter, ,nner. and brittler come from Africa. Canadian experience with asbestosis has cn limited to the chrysorile fiber. The maorry oi industrial processes in the United rates use this fiber, but in recent years there , increased use of the amostte and crocidolite bers. The British and European industries se greater quantities of these harsher fibers. Tiereiore. in trying to clarify the causal eianonshtp of asbestosis and bronchogenic arcmoma. many variable facts should be .eariv identified, especially the type of fiber sed and whether or not other dusts were resent in the industrial and environmental -nosphrre. SVSIMAEY Respiratory disease experience among thousand male and female asbestos v .a in the United States and Canada reported. Of all wnrU-- ----vised to the ers. verv few aeveicro asbestosis -ooestosis is msioious m unset and proesses slowly with continued exposure, jsing respiratory embarrassment and carx failure. Z Rnrrcnctt 2 and 3. Physiologically, asbestosis is the problem of the "tight'* lung. Expansion of the lung is difficult, and there is impaired gas trans fer through the lung. Diffuse, obstructive emphysema is not common. There is a typical x-ray pattern which can not be confused with other pneumoconioses. An x-ray survey of 708 employees in a milling operation showed that the majority had normal x-ray patterns, that 10 or more years of exposure were necessary to pro duce x-ray changes, and that no cases of asbestosis were found who had worked less than 20 years in the dust. The incidence of nonoccupabonal respira tory disease was not increased, nor was the illness more prolonged among workers ex posed to asbestos dust than among nonex posed workers. Asbestosis does not predispose to the development of tuberculosis, nor does it aggravate an apparently healed lesion. There are several reasons for different opinions expressed concerning the relation ship of asbestosis and bronchogenic carci noma. Differences in asbestos fibers are noted. REFERENCES 1. Vorwald. A. J.; Durkan, T. iL, sod Pratt, P. C: Experimental Studies of Asbettosu. A. M. A. Arch. Indust. Hyg. 1:1*43 (Jan.) 1951. Z Badollet. M. S.: Asbestos: A Mineral of Unparalleled Properties. Canad Mite 5c MetaL April. 1951. 3. Badollet. M. S.: Asbestos Fibers: Produc tion and Usage. Canad Min. At MetaL Aug., 1953. 203