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Reprinted from American Journal or Public Health, Yol. 29, No. 3, March, 1939 Published by the American Public Health Association, 30 West 50th St., New York, N. Y. Asbestosis* R. R. SAYERS, M.D., F.A.P.H.A., and W. C. DREESSEN, M.D. . Senior Surgeon, and Passed Assistant Surgeon, U. S. Public Health Service, Washington, D. C. ASBESTOS is well "da-led far use pathological report on asbestosis pub- as a textile i.v .. ,i _ - ... '< ui .-ic! v. -,`ited States, and in the its fibrous nature. Cn acso.nt >v[ uiis, ... yea., 1930, Lynch and Smithr as well as its non-combustible and ex sported on asbestosis bodies found in cellent insulating properties, it has come the sputum of asbestos workers. to be used in ever increasing quantities, The Public Health Service" was re during the past 20 years. Hence, it quested by the State Board of Health is not surprising that Gloyne and Mere- and the Industrial Commission (Ad wether 1 should refer to pulmonary ministrator of the Workmen's Compen asbestosis as a " modem disease." sation Act) of North Carolina to-assist The first record of a case of asbesto them in making an engineering and sis seems to have been mad ' M->nt"- medical study of the health, hazards gue Murray in 1900. '".he .irst co.u lil ih. . > ` tv of that plete description of the . isease and of . ate. Y objgu study the " curious bodies " seen in lung were: tissue and sputum appeared in 1927 1. To make a medical study of the e-fects when Cooke * and McDonald3 reported of long-continued inhalation of asbestos dust 2 cases of asbestosis and listed their reasons for believing that asbestosis bodies- originate from asbestos fibers that reach the lungs. Their papers aroused general interest in the subject on the human body. . 2. To identify the manufacturing processes that create dust,- and. to recommend- practices1 for-reducing the dust exposure of workers. 3. To find out what concentrations of as bestos dust can be tolerated without injury. and numerous others appeared soon It is the purpose of this paper to review afterward. Hoffman4 appears to have briefly the principal findings of this study.8 been the first American to call atten tion to the magnitude of the asbestosis problem. In 1918 he reported that 13 deaths from asbestosis had occurred among asbestos textile workers, and about the same time Pancoast, Miller, and Landis5 reported on 17 cases of asbestosis. Mills's 6 paper was the first ENGINEERING FINDINGS The main asbestos raw material used for textiles is Canadian ebrysotile, which is a hydrated magnesium silicate containing no quartz. The textile manipulations of asbestos are very similar to the production of cotton or- woolen goods. The crude fiber is sent first to the preparation de * Retd before the Industrial Hygiene Section 'f the partment, then, in the order named, American Public Health Association tt the Sixty* to the carding machines, spinning seventh Annual Meeting in Kansas City, Mo., October 28, 1938. \ frames, winding bobbins, twisting ma- ' [2051 509*0254  ASBESTOSIS Figure I--Photomicrographs of Lung Sections Showing the Presence of Nodular Fibrosis and Emphysema in a -Silicotic Lung and Diffuse Fibrosis and Emphysema in an Asbestotic Lung. A Section of a Normal Lung Is Shown ior Comparison. Magnification 16 X. 5O9*0?55 Vol. 29 Asbestosis 207 Table I Summary of Results Showing the Exposure of Asbestos Textile Workers Under Controlled and Uncontrolled Working Conditions Equipment Willowing (opening) Piling t Picking Carding (primary) Carding (roving) Spooling Weaving (broadloom) Brasher calenderer dumber of Duct Connections *2 1 3 3 4 *1 2 3 Volume of Air Handled . rCFM) 625-1,000 1,02S 2,570 1,420 ) 1,440 ) 46.5 1,300 1,650 Dust Con centration With Exhaust (MPPCF) 3.6 2.0 6.7 2.0 2.9 .7 1.0 Dust Con centration Without Exhaust 11.1-36.0 5.4 34.3-74.3 72.3 13.1 4.7-49.7 11.1 * Equipped with pneumatic conveyor, t Exhausted bin or compartment. t Individual cone for each spool and connected to exhaust manifold. chines, spooling frames, and finally to the looms and miscellaneous fabricat ing devices. "' ' In all,' 242 dust counts were made in estimating the exposure of these asbestos workers. Only summary en gineering findings, or dust concentra tions as they relate to medical find ings, will be discussed. Summarized results of dust concentrations under controlled and uncontrolled conditions appear in Table I. It will be noted that 74.3 million particles per cubic foot (m.p.p.c.f.) is the maximum concen tration of dust encountered. Even this maximum figure is much lower than is frequently encountered in other silice ous trades where it has not been un common to encounter maximum dust concentrations of 1,000 m.p.p.c.f. The dust in asbestos plants is made up of particulate, matter and fibers. The median size in microns of particu late matter ranged from l.SS to 2.40. Particles were smallest in the carding and preparation processes, and largest in weaving. The median length of fibers in microns ranged from 7 to 16.3. As might be expected, the long est (400 n) were noted in case of weav ing and the shortest in preparation. Table II Median Length of Fibers Sampled With an Owens Jet Apparatus - Activity Mediant KLength of Fiberr-itcMicrons Willowing Picking Carding Twisting Weaving (broadloom) 7.0 .9.5 8.8 12.8 16.3 Table III She Frequency Distribution of Particulate Dust Suspended in the Air of Asbestos Textile Plants Percentage Frequency of Each Particle Size Croup (in Microns) Nature of Process Where Sample Was Taken Median Geometric Size (in Standard Microns) Deviation. r 0 0.5 to to 0.49 0.99 1 to 1.49 1.5 to 1.99 2 to 2.49 s 2.5 3 3.5 4 4.5 5 to to to to to or 2.99 3.49 3.99 4.49 4.99 More Total Preparation Carding Mule spinning Twisting Weaving (broadcloth) Weaving (tape) 1.85 1.35 1.80 1.22 1.55 2.40 1.56 1.57 1.33 1.74 1.31 1.64 3 21 37 21 10 4 2 1 0 0 0 100 1 9 24 25 9 16 4 5 1 3 3 100 0 1 25 38 23 4 1 1 1 0 I 100 5 30 24 14 9 5 i 5 0 1 3 100 1 4 43 27 10 3 2 3 4 0 3 100 0 3 11 24 14 12 7 13 7 3 6 100 509'025f> ,208 American Journal of Public Health Mar., mo The significance of dust concentra tions and physical characteristics of these air contaminants will be referred to in the course of subsequent discussion. The workers who were found par ticularly liable to develop severe forms of asbestosis were the widowers; pick ers, carders, mule and ring spinners, twisters, and cloth weavers. Their ex posure was found to be as follows: Dust concentration MPPCF Willowers.............................. Pickermen............................. Carders and tenders.......... Mule spinners...................... Ring spinners...................... Twisters................................ Cloth weavers Dry.................................... Wet.................................... 11.1-36.0 34.3-74.3 29.1 2.6-7.9 3.2- 8.3 3.2-13.2 4.7--49.7 4.7-11.1 MEDICAL FINDINGS Medical examinations were made of 541 men and women representing prac tically all the employees at the time of study. Five-sixths of them were native bom Americans of Anglo-Saxon stock and the remainder were Negro males. The three factories studied had been in operation from 6 to 16 years. About 15 months before the study, approxi mately 150 workers were replaced by new ones with little or no asbestos ex perience. As a consequence, there was an abnormally large percentage of work ers with less than 5 years' employment in the asbestos textile industry and an abnormally small percentage who had worked 10 years or more in the indus try. More than 200 had worked at comparable occupations in cotton or woolen textile plants, but exposures to pneumoconiosis producing dusts were inconsequential. Characteristics of asbestosis--Pulmo nary asbestosis was the principal physi cal defect found on examining the 541 persons. ' This disease, a form of pneumoconiosis caused by long con tinued inhalation of asbestos dust, is characterized pathologically by diffuse interstitial pulmonary fibrosis and the presence of asbestosis bodies in the lungs. Clinically, the chief symptoms are progressive dyspnea, variable cough, substernal chest pain, blood streaked sputum, decreased chest expansion, emaciation, weakness, clubbed fingers, or curved nails. Late in the disease, the dyspnea becomes distressing, cyanosis may occur, and there may be severe paroxvms of coughing productive of tenacious sputum. The characteristic chest X-ray shows granular or ground glass markings with more or less obliteration of usual linear pulmonic markings, localized in mid-lung and bases. The grainy appearance may become quite generalized with evi dence of emphysema usually in the apices. Nodular or nodulo-conglomerate shadows of silicosis are not observed, but whether this is due to a peculiarity of asbestos dust or to rare occurrence of extremely high dust exposures, it is impossible to say. Shag giness of the heart shadow is not in frequently observed and seems to be most common in workers exposed to a high proportion of fiber (e.g., twisting, broadcloth weaving). By fluoroscopy, diminished excursion of diaphragm is seen. Peaking deformities of dia phragm, however, occur less frequently than in silicosis. Asbestosis bodies found in the lungs and sputum are characteristic. There is good evidence that these bodies origi nate as a cellular response to inhaled fibers.0 Asbestosis bodies consist of a core of asbestos fiber surrounded by iron-containing protein deposits. They are golden yellow in color, and do not stain with ordinary histologic stains, but become brilliant blue when treated with potassium ferrocvanide. They are " variable in form and size and charac teristically are slender, elongated, seg mented structures with bulbous ends which give them a dumbbell or drum- Vol.29 Asbestosis 209 Ficure II--Photomicrographs of Asbestosis Bodies Found in Sputum. Enlarged S30 Times (Except E, Which Is Enlarged 310 Times). A-Scale; Ruled in Units of SO Microns. Has Been Drawn Beside Each Asbestosis Body. stick shape (Figure II). Occasionally a forked or Y-shaped bodv is observed. They range from 10 to 180 ft in length, averaging about 35 /t. It has been suggested that damage to the lungs occurs while the body is being formed, but once the body is formed the fiber in the core is rendered inert by its coating of iron.10 The find ing in the sputum of clumped asbes tosis bodies in radial pattern or rosette (Figure HE), which is common in lung sections, has been suggested by Stewart, Tattersall, and Haddow11 as a clear indication of disintegration of lung tissue whether by a process of simple suppurative broncho-pneumonia, or as a result of secondary tuberculous infec tion. In either case, they feel that it strongly indicates a definite underlying asbestosis. On single sputum specimen analysis 210 American Journal of Public Health Mar., 1939 NO DUST EXPOSURE AGE AGE i,a,. .,. .,, O IO 20 30 40 50 60 70 80 90 100- PERCENT ________ KAOLIN________ 50 -59 40-49 30-39 20-29 UNDER 20 0 10 20 30 40 50 60 70 80 90 100 PERCENT . . , j ASBESTOS i 50-59 40-49 30-39 20-29 UNDER 20 iiii. . .i . ., 0 10 20 30 40 50 60 70 80 90 100 PERCENT AGE SECOND DECREE GROUND CLASS FIRST DEGREE CROUNO CLASS SECOND DECREE LINEAR FIRST DECREE LINCAR Figure III--Percentage of Males, Classified by Age, Who Had Certain Lung-Field Markings; 229 Men Had No Previous Industrial Dust Exposure, 80 Had Been Exposed to Kaolin Dust, and 3S7 Had Been Exposed to Asbestos Dust. 509*0259 Vol.29 Asbestosis 211 of each case, the incidence of asbestosis bodies increased with increasing dust exposure. They were found in sputum of 46.9 per cent persons whose condition was diagnosed as asbestosis, whereas 24.3 per cent of essentially normal as bestos-exposed persons had bodies in the sputum. They were not observed in any of the persons surveyed with less than 3 months' exposure. Since they may be found in the sputum be fore significant fibrotic changes have occurred, their presence is interpreted as merely showing evidence of exposure. X-ray interpretations--During the de velopment of a typical pneumoconiosis, the lung field appearances of chest roentgenograms pass through a series of rather well defined phases. Begin ning with the normal adult film with its linear pulmonic markings, the first next appreciable change is an exaggera tion of these markings. Then a ground glass or granular appearance is noted which gradually obliterates the linear markings, followed by nodular and nodulo-conglomerate markings. The lung field appearances in asbestosis do not appear to proceed beyond the ground glass or granular phase. Classification of all films was made according to phases. The apparent small amount of involvement of lungs makes it diffi cult to evaluate the severity of the case from an X-ray film only. The difficul ties of interpretation of the chest films' emphasize the importance of careful technic. As a form of pneumoconiosis, asbestosis strikingly indicates the neces sity for clinical study of a case before diagnosis can be made. The film of a patient severely ill with asbestosis may have markings which would appear in significant alongside a typical silicotic film of a man who is actively at work. In the interpretation of asbestotic films the physician must be aware of exaggerated markings attributable to advancing age. This is illustrated in Figure III. One group comprising 229 men had never been employed in a dusty trade; the other included 80 men en gaged in mining and refining of kaolin by wet methods... The percentage of men who have second degree exaggera tion of linear lung markings in creases with advancing age. It is significant that in this entire group of 309 men there were no cases of ground glass lung field markings, even though this change is observed in the asbestos workers. It appears that the reason why the incidence of the ground glass type of pulmonic marking is correlated with age is that older people have been exposed to dust for the longest time. Occurrence of asbestotic lung changes --In Figure IV the heights of vertical bars represent the percentages of asbes tos workers in different exposure groups who had ground glass lung field mark ings of either first or second degree. Seventy-six controls have been excluded from this tabulation and a number of workers whose dust .exposure was not known have also been omitted. . Considering the four dust exposure groups, one at a time, there is a con sistent and regular increase in the per centage of persons with these ground glass markings with increasing length of employment. Age, of course,.also increases with length of employment, but these fibrotic changes cannot be ascribed to advancing age because the previous figure (III) showed that fibro tic changes of this degree are not to be expected in workmen of comparable age who are not exposed to siliceous dusts. Note the absence of cases with ground glass markings in the group exposed to less than 5 m.p.p.c.f. Obviously, there are great differences between individuals in the time that elapses from their first exposure to asbestos dust and the time fibrotic evi dence is observed in the X-ray film. In some persons this was much less than 5 years and in others it appears to be more than 10. Some of the difference SQ&q&rGD 212 American Journal of Public Health Mar., 1930 Figure IV--Percentage of Asbestos Textile Workers, Classified by Average Dust Concentration (Measured in Million Particles per cu. ft.) and Duration of Exposure, Found to Have Ground-Glass Lung-Field Markings. is probably due to total amount of asbestos dust inhaled. Difference in amount of physical exertion may play an important role--a person in a seden tary job having a smaller need for oxygen inhales less air and consequently fewer particles of asbestos. It was noted that the relation between dust exposure and the incidence of ground glass lung field markings was not a simple one. Even when length of employment was disregarded, it was found that incidence of these markings' was proportionately lower at 10 to 19.9 m.p.p.c.f. than it was at the next higher or next lower concentrations. Although it is probable that these differences rep resented sampling errors due to small numbers of exposed persons, it may be that asbestos fiber excites a different and possibly more severe reaction than asbestos particles. , On account of large labor turnover, as well as the short time that ,th$ plants had been in operation, no exact estimate of incidence of asbestosis can Table IV Occurrence of Asbestosis in Relation to Dust Concentration and Length of Employment Percentage With Asbestosis Years in Asbestos Industry Dust Exposure, Million Particles per Cubic Foot f Affected 0 to 4.9.......................................... < Exposed [ Percentage f Affected 5 to 9.9.................... '..................... ) Exposed [ Percentage f Affected Over 10.......................................... ( Exposed [ Percentage 0 to 4.9 2 84 2% 0 70 0Jo 8 134 6% 5 to 9.9 1 19 s% 6 37 16% 22 43 51% Over 10 0 5 0% 13 19 <53% 21 36 58% * 509*0261 214 American Journal of Public Health Mar., 1939 evidence of asbestosis is observed in exposed persons after 5 to 10 years of work in ex posures exceeding 5 m.p.p.c.f. 7. It appears that if asbestos dust concen trations in the air breathed arc kept below 5 m.p.p.cX new cases of asbestosis will not appear. S. Methods for controlling the dust below this tentative threshold are already available for most of the processes in the industry. REFERENCES 1. Gtoyne, S- R., and Merewether, E. R. A. .tiieitos. Occupation and Health (Suppl.), Inter national Labour Office. Geneva. 1938. 2. Cooke, W. E. Pulmonary Asbestosis. Brit. M. /.. 2:1024-1025. 1927. 3. McDonald, Stuart. Histology of Pulmonary As bestosis. Brit. M. J.t 2:1025-1026. 1927. * 4. Hoffman. F. L. Mortality from Respiratory Dis eases in Dustv Trades (Inorganic Dusts), Bull. U. S. Bur. Lab. Slat. No. 231, 1918, pp. 176-180. 5. Pancoast, H. K., Miller, T. G., and Landit, H. R. M. A Roentgenologic Study of the Effects of Dust Inhalation Upon the Lungs. TV. A. Am. Physicians, 32:97-108. 1917. 6. Mills, R. G. Pulmonary .Asbestosis: Report of a Case. Minnesota Med.. 13:495-499, 1930. 7. Lynch, K. M., and Smith, W. A. Asbestosis Bodies in Sputum and Lung. 1.AM.A95:659-665, 1930. 8. A Study of Asbestosis in the Asbestos Textile Industry. Pub. Health Bull. No. 241. Aug.. 1938. 9. Gloyne, S. R. The Atbestosis Body. Lancet. 1:1351-1356 (June 25). 1932: Sundius, N.. and Bygden, A. Der Staubinhalt einer Asbestosislunce und die Beschaffenheit dcr sogenannten Asbestosis* korperchen. Archiv. /. Gcxotrbepatk. u. Gexocrbchyt., 8:26-70, 1937; `Gloyrie, S. R. The Morbid Anatomv and Histology ol Asbestosis. Tubercle, 14:445-451*: 493-497; 550-558. 1933. 10. Kettle, E. H. The Interstitial Reactions Caused by Various Dusts and Their Influence on Tuberculous Infections. J. Path. & Bad., 35:395 405. 1932. 11. Stewart. M. J., Tattersall. N,, and Haddow, A. C. On the Occurrence of Clumps of Asbestosis Bodies in the Sputum of Asbestos Workers. /. Path. & Bad.. 35:737-741. 1932. 12. Lanza. A. J., McConnell. W. J.. and Fehncl. J. W. Effects of the Inhalation of Asbestos Dust on the Lungs of Asbestos Workers. Pub. Health Kt:p,, 50:1-12. 1935. Reprint No. 166S. 13. Page, R. T.v and Bloomfield. J. J. A Study of Dust Control Methods in an Asbestos Fabricating Plant. Pub. Health Rep.. 52 (Nov. 26), 1937. Reprint No. ISS3. 14. Lynch. K. M., and Smith, W. A. Pulmonary Asbestosis II. Am. Rev. Tuberc., 23:643-660. 1931. 15. Egbert. D. S. Pulmonary Asbestosis. Am. Rev. Tuberc..' 31:25-34, 1935. 16. Stock. G. A, Pulmonary Asbestosis. 3/. Bull. Vet. Admin., 10:126-129, 1933. 17. White, T. P. Pulmonary Asbestosis. Tr. Med. Soc. North Carolina, 1935, pp*. 259-262. 18. Lynch, K. M,, and Smith, W. A. Carcinoma of Lung in Asbesto-silicosis. Am. /. Cancer, 24: 56-64, 1935. t\ 509*.Q22 Vol.29 Asbestosis 213 be made. Table IV shows, however, were found in dust concentrations ex that the percentage of persons with ceeding 5 m.p.p.c.f., and because they asbestosis increases greatly with increas were not found at lower concentrations, ing length of employment. Lanza, 5 m.p.p.c.f. may be regarded tentatively McConnell, and Fehnel12 reported a as the threshold, value for asbestos-dust similar trend. The incidence also in exposure. creases with increasing dust concentra A supplemental engineering study 13 tion. For the reason that there are was made in an asbestos textile factory but few cases with more than IS years' in which dust control equipment had exposure, the percentages in Table IV recently been installed. This showed are necessarily minimal estimates, of that means are already available for prevalence of asbestosis even though reducing the dust exposure of a majority several of the former employees are of asbestos textile workers to less than included. 5 m.p.p.c.f. The basis of this control was exhaust ventilation near source SAFE LIMITS OF EXPOSURE TO ASBESTOS of dust. ' DUST For practical purposes it is useful CONCLUSIONS to have a definition of safe_.working. - As in other'forms of pneumoconiosis, conditions. Ideally, a threshold con occupational history, and clinical and centration of dust should be the highest X-ray (or pathologic) findings must dust concentration that would not be in harmony before a sound diagnosis produce pneumoconiosis .ia originally can be made. The occupational history healthy workmen during their entire should be a reflection of manufacturing working life. Below 2.S m.p:p.c.f. the processes since the job designation re interpretation of Table IV offered no fers to a stage in manufacture. The difficulties, since none of 39' persons occupations which were found particu exposed to that concentration had as larly liable to induce severe forms of bestosis, although only 6 had been em asbestosis were willow, pick, card, spin, ployed more than 5 years. Three twist, and cloth weave. Confirmation of doubtful cases of asbestosis fell in range the hazardous nature of some of these 2.5 to 4.9 m.p.p.c.f. occupations is the frequency with which Because clean-cut cases of asbestosis the occupational designation of carder, Table V . - _ Percentages of Workers-Exposed to Certain Concentrations of Asbestos Dust, in Asbestos Textile Factories Wherer- Dust ~ Control~ Measures Are Used to a Limited Extent and in Factories Where Effective Dust Control Is Practised weaver, or spinner is encountered in autopsy, reports of cases.14-18 The fol lowing are the outstanding findings determined in this study: 1. In a study of 541 employees of North Carolina textile mills, pulmonary asbestosis was the principal physical defect found. Limited Use Dust Concentration of DustMillion Particles Control per Cubic Foot Measures * Over 10 5 to 9.9 2.5 to 4.9 Under 2.5 48 28 15 9 Data from Table IV. t Data from reference 13. Extensive Use . of DustControl Measures f 7 17 32 44 2. The most serious forms of the disease were observed in carders, spinners, weavers, twisters, willowers, and pickers. 3. Exposures ranged from 0.10 to 76 m.p.p.c.f. 4. Bust contaminants of air in asbestos textile plants are both particulate and fibrous. 5. It is imperative that findings of occupa tional history, clinical examination, and X-ray film all be considered in making diagnosis of a case. 6. Definite clinical and roentgenagraphic 509*0263