FILE NAME: Owens Illinois Library (OWL) DATE: 1951 DOC#: OWL030 DOCUMENT DESCRIPTION: Article from the Archives of Industrial Health Experimental Studies of Asbestosis i : A ill® l9 A R C H I V E S OP Industrial Hygiene and Occupational Medicine EDITORIAL BOARD PHILIP DRINKER, Chief Editor 55 Shattuck Street, Boston 15 THEODORE F. HATCH, Pittsburgh ROBERT A, KEHOE, Cincinnati FENN E. POOLE, Glendale, Calif. FRANK PRINCI, Denver FRANK A. PATTY, Detroit WILLIAM A. SAWYER, Rochester, N. Y. JAMES H. STERNER, Rochester, N. Y. RICHARD J. PLUNKETT, M.D., Chicago, Managing Editor V olum e 3 1951 PUBLISHERS AMERICAN MEDICAL ASSOCIATION CHICAGO 10, ILL. 10 Nose industrial perforated ulcers of septum In glass workers, 329 Nuclear Energy: See Radioactivity Occupations: See Industry and Occupations O'Connor, R. B. Analysis of existing types of small-plant health services In northeastern United States [O’Con­ nor], *73 Odors control of, 217 O il: See also Castor Oil Bean derm atitis: from turpentine. 106 disposal: and varnish fume, 218 Osmium poisoning: by newer metals, 535 Otolaryngology work placement of persons with diminished work­ ing capacity in, 324 Oxygen: See also Respiration atomic: at surface of freshly crushed silica. 414 inhalation o f: effects. 206 poisoning: In man, 32$ Paint Industry oil and varnish fumes: disposal, 218 Paints quick-drying: white blood cell counts of sprayers using: study of health of workers using benzene solvents In modem factory, 429 Pancreas lipocalc, histopathologic modifications in experi­ mental Intoxication due to trinitrotoluene, fol­ lowing therapy with methionine a n d : behavior of kidneys, adrenals, spleen, lungs and heart, 330 Faqutn, H. 0 ., Jr. Chronic toxicity of methylpolysiloxane "DC anti­ foam* A" in dogs, *479 Paralysis of respiration: first aid service for workers with, 537 Parathlon in air samples: determination by ultraviolet ab­ sorption spectroscopy, 431 anticholinesterase: activity in vitro of Insecticide, 327 toxic effects, 213 toxicology, 213 Peptic Ulcer cement: new occupational disease due to, 417 occupational facto rs: etiology, with estimate of their incidence In general population, 520 Periodicals Industrial Hygiene Newsletter renamed Industrial Health Monthly, 541 Transactions of Association of Industrial Medical Officers, 541 Petroleum cancer: environmental, and, 441 F rench: and Its possible use In prophylaxis of benzene poisoning, 329 leaded-petrol h andlers: paranoid states occurring til, 532 Petroleum Industry atmospheric contamination by petroleum-treating establishments, 433 personnel refining or selling: comparative study, 410 shale oil: hydrogen sulfide poisoning in [Ahiborg], •247 PG U P: See Propylene Glycol Dtproplonate Phenols In Blood: See under Blood Phenyl Mercury Compounds: See under Mercury Phenylalanine ’5. >< • ! « • » . I n . « « f «m nlt Phlebitis abdominal anthracosilicotlc, 327 Phosphorus and Phosphorus Compounds phosphine poisoning, 421 phosphorus b u rn s: treatment, 437 Photofluorography: See Roentgen Rays Physicians viewpoint In Industry (Kessler], *185 workman and, 409 Pittsburgh air pollution In [Ely], *44 Plantation medicine, 426 Plastics chlorovlnyl: conditions of work and Industrial hy­ giene measures in production of and manufacture from, 324 Plotkin, T. Air flow measurements on human subjects with and without respiratory resistance a t several work rates, *461 Plutonium excretion and distribution of yttrium an d : effect of different dose levels of zirconium, 424 Pneumoconiosis advice to patients, 524 •sbestosls: contribution to study, 428 asbestos!«: experimental studies (Vorwald & oth­ ers], *1 cereal dusts: cause, 525 delayed. 418 emery dust: case due to, 525 in Germany, 419 kaolin: case attributed to, 529 mlneralogical aspects of research, 413 radiographic appearances*in coalminer's: classifica­ tion. 523 roentgen aspects of, 102 silicosis: acute, from ruck excavation, 105 silicosis: BCG vaccination in, 207 silicosis: Mood changes in slUcotuberculoals and, 418 silicosis: cardiorespiratory function In, test, 528 silicosis: compensation for change of employment in, 410 silicosis: electrocardiogram, significance, particu­ larly of chest wall leads, for evaluation of, 429 silicosis: erythrocyte sedimentation rate in stages of, 429 silicosis: freshly fractured surface, theory of, 208 silicosis: heart in, 530 silicosis medical bureau: Northern Rhodesia, 410 silicosis: In metallurglcsl Industry In France, 210 silicosis: among pottery workers In Limousin, 416 ■ silicosis: problems, 417 silicosis: pulmonary bullous emphysema as cause of spontaneous pneumothorax in patients with. 527 silicosis: report on country-wide study In metal mines of Japan [Yamamoto], *339 silicosis: roentgenological evolution of asymptoma­ tic, 211 silicosis: In sand blasters, 210 silicosis: severe complicated, diagnosed 20 years after patient had left workplace In which there had been considerable dust exposure, 530 silicosis: suppression of dusts that may produce, 539 silicosis: temporary disability and. 417 silicosis: tuberculosis and dust, 419 silicotic lung: new' tests for study of, 209 silicotic lungs: freshly broken so-called old quartz from, comparative animal experiments on effect of, 423 silicotic pneumoconioses: treatment of, 103 stllcotics: adrenocortical function tn, 320 MUcottcs •• vital capacity: Importance of methods Pneumoconiosis—Continued slllcottcs: vital capacity: mo< capacity and of other respirai pulmonary, 527 stannic oxide, 101 and 325 various form s: studied especial! pneumonoconlosls and baritot* sulfide, 526 Pneumonia metal dust pneumonitis, 211 Pneumothorax * spontaneous : pulmonary button cause In patients w ith slllcosi Poisons and Poisoning: See under ous substances, as Lead; etc. Polonium static elim inators: study of coi tla l of. 432 Polyneuritis : See Neuritis, multlp' Porphyrin and ro rp h y rtn Compoun In blood : Sec under Blood m etabolism: adverse effect of B.' acute polyneuritis with observa Postman, B. F. Engineering control of occupatlo: •169 Pottery Industry silicosis among workers In L!m<> P ratt, P . C. Experimental studies of asbestos Prlckett, C. S. Occurrence of DDT In human f. Printing Industry benzene In : toxic effects, 425 Princl. F. Study o f workers exposed to lns< aldrtn, dleldrln, *64 P ritchard, f f . H. Five cases from fluorescent lamp ment of chronic beryllium pols and cortisone, *549 Propylene Glycol Dlproplonate toxicity o f (Ambrose], *48 Proteins requirement of h ard workers: 1> extractives on ability to work. Protoporphyrin: See Blood, porphyr compounds Psychiatry: See also Mental Dise viewpoint o f psychiatrist (in sol ards) (Bow m an], *181 Psychosomatic Factors in exhaustion of executives, 204 ru b llc H ealth : See also Hygiene Industry and Occupations atomic energy : aspects, 438 Quartz: \ See Pneumoconiosis; Sill Radiations: See also Roentgen Ra\ bibliography of detection, 115 gamma-ray dose : measurements radiotherapist during radium «. hazards: In atomic energy progr injury: rases. In radiological w o. instruments fo r detection of rs; leukemia: in radiologists In 20 y< neutron cataracts, 412 photofluorographlc personnel : pr< problem of excessive: problem d restorations of heart, 115 "tolerance dose** for X and T r trial tolerance conference of ci. 439 vocational and atomic exposure l> 113 Radioactivity : See also Atomic Enctv Radioactivity—Continued blood changes: in lumtnlzers using material, 441 isotope: appraisal of detergency through, 546 isotope: planning small program, 539 Isotope: radiation-exposure purvey of x-ray and. personnel, 446 isotope studies In experimental animals, small selfcontained laboratory for [Sognnaes 4 Shaw), *316 monel metal nasopharyngeal radium applicator: exposure of personnel handling. 113 static eliminators: hazards from, 112 substances In biological tissues, 115 unite of, 114 waste disposal, 113 Radioisotope: See under Radioactivity Radium : See also Radiations; Radioactivity in exposed humans: direct method for determining. 446 Read,' H. Viewpoint of union (toward plant industrial health program), *188 Rehabilitation physical medicine and, therapy of hand Injuries [Flax], *236 vocational: of psychiatric patients, 215 Retndollar, W. F. Health and atr pollution, *399 Religion viewpoint toward plant health program (Henry], ♦192 Renner, W. F. Significance of exercise tolerance test. *129 Respiration air flow: measurements on human subjects with and without respiratory resistance at several work rates [Silverman 4 others], *461 artificial: new method and comparative study of different methods In adults, 428 cardiorespiratory function In silicosis: test, 528 paralysis o f: first aid service for workers with. 337 vital capacity of silicotics: Importance of methods of determining theoretical vital capacity of sili­ cosis, 527 ( vital capacity of silicotics: modification of vital capacity and of other respiratory indications in pulmonary silicosis, 527 Respiratory T ract: See Nasopharynx; Nose: etc. Reynolds. P. \V. Beryllium disease from ceramic Industry: report of case, *575 • Rheumatism work placement: of persons with diminished capac­ ity due to, 324 Roentgen Rays: See also Radiations aspects of anthracoslUcosls, 162 biological significance of, 222 Quartz: See Pneumoconiosis; Silicon Compounds diffraction method for finding quartz In Industrial dusts [Schmelzer], *121 Radiations: See also Roentgen Rays exposure survey of Isotope and, personnel. 446 bibliography of detection, 115 gamma-ray dose: measurements of, received by personnel monitoring, 441 radiotherapist during radium operations, 222 roentgenological evolution of asymptomatic sili­ hazard s: in atomic energy program, control, 439 cosis, 211 workers: positive cephalin-cholesterol flocculation Injury: cases, In radiological work, 223 test in, 438 Instruments for detection of rays. 114 leukem ia: In radiologists In 20 year period, 222 Safety neutron cataracts, 412 m ine: t achievements, research and problems yet to photofluorographlc personnel: protection of, 114 be solved, 336 . problem of excessive: problem during routine In­ mine: research, twenty-seventh report, 1948. Lon­ vestigations of heart, 115 don, 219 J "tolerance dose" for X and T radiation: Indus­ In water and sewage works, problems of industrial trial tolerance conference of currently accepted, hygiene and, 332 439 Sandblasting Industry vocational and atomic exposure burns: treatment, silicosis :t in sand blasters, 216 113 x . Sander. O. A. Radioactivity: See also Atomic Energy: Radiations: Pneumoconiosis—Continued silicotics: vital capacity: modification of vital capacity and of other respiratory Indications In pulmonary, 527 stannic oxide, 101 and 325 various form s: studied especially In Ita ly : thlopneumonoconlosls and baritosis due to barium sulfide, 526 , . Fneumonla metal dust pneumonitis, 211 Pneumothorax spontaneous: pulmonary bullous emphysema as cause In patients with silicosis, 527 Poisons and Poisoning: See under names of poison* ous substances, as Lead; etc. Polonium static eliminators: study of contamination poten­ tial of, 432 Polyneuritis: See Neuritis, multiple Porphyrin and Porphyrin Compounds In blood: See under Blood . . metabolism: adverse effect of BAL In case of sub­ acute polyneuritis with observations on, 428 Postman, B. F. Engineering control of occupational health hazard, *169 Pottery Industry silicosis among workers in Limousin, 416 P ratt, P. C. Experimental studies of asbestosls, *1 Prickett, C. S. Occurrence of DDT in human fat and milk, *245 ■Printing Industry benzene in : toxic effects, 425 Prlncl, F. Study of workers exposed to insecticides chlordan, aldrin, dleldrln, *64 Pritchard, W. H. Five cases from fluorescent lamp industry: treat­ ment of chronic beryllium poisoning with ACTH and cortisone, *549 Propylene Glycol Dlproplonate toxicity of (Ambrose), *48 Proteins requirement of bard workers: influence of pure extractives on ability to work, 411 Protoporphyrin: See Blood, porphyrin and porphyrin compounds .Psychiatry:. See also Mental Diseases viewpoint of psychiatrist (In solving health hazards) [Bowman), *181 Psychosomatic Factors In exhaustion of executives, 264 'Public H ealth: See also Hygiene and Sanitation: Industry and Occupations atomic energy: aspects, 438 r h r m t l o bcrvlllo«!*» In in*'*»» h!-;« In»t i-trv . **it* 428 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE ABSTRACTS A rtificial R espiration : A N ew M ethod and a Comparative S tudy of D ifferent Methods in A dults . A. S. Gordon, D. C. F aiver and A. C. I vy, J. A. M. A. 144:1455-1464 (Dec. j which asbestosis appeared, it w; asbestosis rather than to the ordì genologic examinations indicate tl these miners it develops so slov that it predisposes to tubercolosi' of experts from Saranac. , T h e E rythrocyte S edimentati F ay , Rev. Méd. Minière, 195 23) 1950. ) The relative efficiency of the pulmonary ventilation obtained by manual and by mechanical methods of artificial respiration was studied on 109 warm corpses and nine normal subjects. The manual techniques utilizing both "push and pull” principles provided about twice the minute volume obtained with only a "push” or a “pull” method. The "push and pull” techniques include the Nielsen (armlift-scapular pressure), the Schafer-Emerson-Ivy (hiplift-prone pres­ sure and hiproll-prone pressure) and the Schaffer-Neilsen-Drinker (armlift-prone pressure) methods. The simple “pull” methods of hiplifting or rolling are more effective than the "push” method of Schaffer. These procedures are compared as to ease of execution. In addition, the adequate mechanical methods of intermittent positive devices and alternating positive and negative pressure resuscitators are discussed and compared with manual pro­ cedures in regard to efficacy and relative merits. The mechanical techniques have the advantages of simplicity of proper administration, being non-fatiguing, and of supplying 100 per cent oxygen, and they may be used when patients cannot be moved because of the nature of the injury. The chief advantage of the manual techniques is the equally effective pulmonary ventilation without need of. special equipment. A rnold a ^ BostolL j 1 Using the Fuente Hita methorate in 464 cases of silicosis. Tl subjects for several years. In 30 rated sedimentation rate, which n 84 of 108 cases of the nodular ty (90) they observed two types of in those with shadows showing re were produced as in the precedin' The authors believe the erythroi of silicosis. ; » A n A dverse E ffect of BA I. in a Case of S ubacute P olyneuritis with O bservations on P orphyrin M etabolism. J ames H. S ands, B arnet B erris and L. R aymond S cherer, New England J. Med. 248:558-561 (Oct. 12) 1950. S ignificance of t h e E lectrocai ation of S ilicosis. J. Ho, I A case of arsenical polyneuritis treated with dimercaprol (BAL, British antilewisite) is pre­ sented. Marked aggravation of neurologic symptoms and signs followed the administration of dimercaprol in the usual dosage. This is believed to be the first report of such an adverse response to dimercaprol during treatment of arsenical poisoning. Possible explanations are considered. Serial urinary arsenic and coproporphyrin studies are described. The urinary type III copro­ porphyrin excretion was markedly elevated, and the erythrocyte protoporphyrin considerably elevated. Dimercaprol therapy caused a slight increase in the urinary excretion of arsenic and coproporphyrin, although the findings were not conclusive. f A daptation of A uthors’ S ummary . W ork E valuation of R ehabilitation. A. L. S tevens, Occup. Therapy 29:157 (June) 1950. A Contribution to the S tudy of A sbestosis. P. Cartier, Arch, malad. profess. 10:589-595, • 1949. For more than three years the author has been in medical charge of 3,242 men employed in mining asbestos at Thetford in Canada. At these mines over 70 per cent of the world's supply of asbestos is obtained. Forty per cent of the men have been employed for 10 to 40 years. The minerals mined consist of asbestos in the form of chrysolite and serpentine. Dust from serpentine lias been found clinically and by experiment to be a nuisance rather than a source of pneumoconiosis. But it is known that asbestos originates asbestosis, at least when its dust is generated while the mineral is being spun and woven into cloth. Cases of asbestosis were found only in those who had been employed for at least 14 years and exposed to air containing 5,000,000 or more particles of asbestos fibers per cubic foot, the fibers being from 10 to 250 microns in length. The outstanding feature of this report is the mildness of any pulmonary trouble found among the miners resulting from inhalation of asbestos dust, compared with what has been reported in the United States and Great Britain as occurring in factories where asbestos is spun and woven. Clinically none of the symptoms of pulmonary fibrosis— cough, dyspnea, cyanosis and loss of weight—were present. No case of pure asbestosis was detected in those under age 60, and most of them were carrying on their work without any physical incapacity. The mining neighborhood would seem to be unduly “infected” with tubercu­ losis, but cases of that disease were not found to be any more frequent among the miners than t \ ! ! ! • \ V According to the German law be granted in cases of pneumor provided that "the coniotic new reduced respiratory capacity an capacity of the body becomes cc patient with silicosis and reduce reaction may be determined ear decompensation has not yet rest: It also facilitates differentiation o Electrocardiographic records chest wall electrocardiograms a differentiation of myocardial lesmay be demonstrated with their by the extremity-electrocardiogra’aid in the diagnosis of the lex and the left ventricle, respective, of an increased hemodynamic b; as a "circulatory reaction” in t'. majority of cases without any <■' Myocardial lesions were deni patients, and five of the 27 pi Localization of the myocardial h the chest wall electrocardiogram instances. Extrasystoles, arrhyt addition to changes in the ST se W hite B lood C ell Counts or H ealth of W orkers U sr i and K. T- V esel£, Casopis ' Blood examinations were carrn quick-drying paint which was diss A B STR A C T S FROM CURRENT L ITE R A TU R E ■ I which asbestosis appeared, it was difficult to ascribe any cardiac affections present1to the asbestosis rather than to the ordinary wear and tear of life. Postmortem findings and roent­ genologic examinations indicate that asbestosis is undoubtedly a pathological entity; .but among these miners it develops so slowly as not to shorten working life, and there is no evidence that it predisposes to tuberculosis. The conclusions arrived at are supported by the opinions of experts from Saranac. E. L. CoLLIS [B ull H yg.]. T he E rythrocyte S edimentation R ate in S tages of S ilicosis. F ay, Rev. Méd. Minière, 1950, nos. 9 and 10, p, 19. F. F oubert and G, L a Using the Fuente Hita method in a sloping tube, the authors have studied the sedimentation rate in 464 cases of silicosis. They have established sedimentation curves after observing the subjects for several years. In 30 cases of silicotuberculosis they almost always found an accele­ rated sedimentation rate, which might precede the manifestation of the tuberculous process. In 84 of 108 cases of the nodular type, they observed a low rate. In cases with massive shadows (90) they observed two types of curve, high in cases with diffuse extensive shadows and low in those with shadows showing retraction. ' In 236 cases with coalescent shadows the same results were produced as in the preceding category, according to whether they were progressive or not. The authors believe the erythrocyte sedimentation rate to be useful in following the progress of silicosis. E nglish S ummary. S ignificance of the E lectrocardiogram, P articularly of C hest W all L eads, for E valu ­ ation of S ilicosis. J. H ormann , Ztschr. Kreislaufforsch. 39:624 (O ct) 1950. According to the German law of compensation for occupational diseases, compensation must be granted in cases of pneumonoconiosis associated with progressive pulmonary tuberculosis, provided that “the coniotic new growth of connective tissue within the lung tissue causes reduced respiratory capacity and circulatory reaction to such an extent that the functional capacity of the body becomes considerably impaired." Fair evaluation of the condition of the patient with silicosis and reduced functional capacity, therefore, requires that any circulatory reaction may be determined early. Observation of this circulatory reaction, particularly if decompensation has not yet resulted, may be obtained with the aid of the electrocardiogram. It also facilitates differentiation of myocardial lesions due to silicosis and those of other origin. Electrocardiographic records obtained from 107 patients with silicosis demonstrated that chest wall electrocardiograms are most useful with regard to both circulatory reaction and differentiation of myocardial lesions, because changes in the ST segment and in the T waves may be demonstrated with their aid at a time when those changes cannot yet be demonstrated by the extremity-electrocardiograms. The chest wall electrocardiograms are also of considerable aid in the diagnosis of the localization of the objectivated myocardial lesions of the right and the left ventricle, respectively. The occurrence of typical steep curves as a manifestation of an increased hemodynamic burden placed on the right ventricle may ndt yet be considered as a “circulatory reaction” in the legal sense, since a typical steep curve occurs in the large majority of cases without any clinical symptom of impairment of the heart. Myocardial lesions were demonstrated on electrocardiographic examination in 27 of the 107 patients, and five of the 27 presented a normal curve in the extremity-electrocardiogram. Localization of the myocardial lesions in the left ventricle could be diagnosed with the aid of the chest wall electrocardiogram in 11 instances, and localization in the right ventricle in nine instances. Extrasystoles, arrhythmias and one typical Wilson block could be demonstrated in addition to changes in the ST segment in the remaining pathologic electrocardiographic records. W hite B lood Cell Counts of S prayers U sing Q uick-D rying P a in t s : A S tudy of t h e H ealth of W orkers U sing B enzene S olvents in a Modern F actory. F. J indrAk , and K. T. V esel^, Casopis L6karu Ceskych 89:285-288 (March 10) 1950. 1 Blood examinations were carried out for 25 persons employed as many as 23 years in spraying quick-drying paint which was dissolved in solvents of the benzene type. Spraying was carried Al • • M ite s al Industrial Hygiene and Occupational Medicine Volume 3 JANUARY 1951 N umber 1 Copyright , 1951, by t h e A merican Medical A ssociation EXPERIMENTAL STUDIES OF ASBESTOSIS ARTHUR J. VORWALD, Ph.D.lPoth.), M.D. THOM AS M. DURKAN AND PHILIP C . PRATT, M.D. SARANAC LAKE, N. Y. A SBESTO SIS is a form of pneumonoconiosis resulting front pro^ longed inhalation of asbestos dust. The name “asbestos," literally “unburnable,” is not that of a specific mineral but is a term applied to a number of different minerals whose characteristic feature is a structure composed of long, parallel, flexible fibers. This structure is unique because the fibers are capable of repeated longitudinal subdivision to units of molecular proportions. In length the fibers vary from a few microns to 6 or more inches (15 or more cm.). Some varieties are stiffer than others, but many are sufficiently flexible to be spun into yarn and woven on modified textile machinery. The asbestos minerals are silicates of variable composition and belong to the serpentine and the amphibole groups. Listed below are the more common varieties. • Amphibole group: actinolite, amosite, amphibole, anthophyllite, crocidolite and tremolite. Serpentine group: chrysotile. The bulk of the asbestos of commerce is chrysotile, 3M g0.2Si0,.2H „0, which is mined on this continent principally in the Thetford region of the Province of Quebec, Canada, and in Vermont. Crocidolite and amosite also are used commercially but in much smaller amounts. Chrysotile occurs as veins in serpentine, a mineral of similar chemical composition, which exists in massive form and is made up of microscopic fibers without the parallel orientation characteristic of chrysotile. The massive, bluish black serpentine, which is smooth and soapy to the touch, is traversed by veins of fibrous chrysotile varying in width from a barely perceptible line to 6 (15 cm.) or more inches. The fibers run across the vein and not lengthwise with the formation. From the Saranac Laboratory of the Edward L. Trudeau Foundation. This series of studies of asbestosis, initiated at the Saranac Laboratory more than twenty years ago by the late Dr. Leroy U. Gardner, director of the laboratory, was nearly completed at the time of his death in October 1946. Although partial reports and informal reviews of some of the experiments had W n f- • ■' vi CONTENTS OF VOLUME 3 A. JUNE — C o n tin u e d PAGE Chronic Beryllium Poisoning of Long Duration from Fluorescent Lamp Manufacturing: Report of a Case. George K. Fenn, M.D., Beverly, Mass.............................................. 571 Beryllium Disease from the Ceramic Industry: Report of a Case. Preston W. Reynolds, M.D., Schenectady, N. Y................................................................................................. 575 Metabolic Study of a Oise of Chronic Beryllium Poisoning Treated with ACTH. Harriet L. Hardy, M.D.; Frederic C Bartter, M.D., Boston, and Abraham E. Jaffin, M.D., Jersey City, N. J .............................................................................................................. 579 Choice of Drugs and Dosage. Howard S. Van Ordstrand, Cleveland.......................... . M ires ni Industriai H) Vo l u m e 3 JA N C o p y r ig h t , 1951, b y ti EXPERIMENTAL ‘ 583 ARTHUR Ì . VO. Recognition and Prevention of the Complications of ACTH and Cortisone Therapy. Thomas F. Frawley, M.D., Boston............................................................................................... 587 THOM a Information Gained in Pretherapy and Post-Therapy Pulmonary Function Studies. John McClement, M.D, New York.......................................................................................... 599 PHILIP SARAN Pulmonary Function in Patients with Pulmonary Disease Treated with ACTH. B. G. Ferris Jr., M.D.; J. E. Affeldt, M.D.; H. A. Kriete, A.B., and J. L. Whittenberger, M.D., Boston ................................................................................ 603 Interpretation of Results of ACTH and Cortisone Therapy in Chronic Beryllium Poison­ ing : Data Obtained by Pretherapy and Post-Therapy Studies of Pulmonary Function. George W. Wright, M.D., Trudeau, N. Y...................................................................... 617 Minimum Observations Necessary to Advance Knowledge of the Action of ACTH and Cortisone. Anne Forbes, M.D., Boston............................................................................ 622 Current Research Problems Concerning Pulmonary Granulomatosis in Beryllium Work­ ers. Friedrich Klemperer, M.D., Trudeau, N. Y.............................................................. 625 General Discussion on the Treatment of Chronic Beryllium Poisoning with ACTH and Cortisone ........................................................................................................................... 629 Health Hazards in the Production and Handling of Vanadium Pentoxide. Sven-Gosta Sjôberg, M.D., Eskilstuna, Sweden................................................................................. 631 News and Comment.................................................... 647 Book Reviews .......................................................................................................................... 648 A S B E S T O S IS is a form oi -a x longed inhalation of asbest “unbum able,” is not th at of a sj num ber of different m inerals w! composed of long, parallel, fle> because th e fibers are capable units of molecular proportions, m icrons to 6 o r m ore inches ( stiffer th a n others, but m any a: y am an d woven on modified t t T h e asbestos m inerals are silk to the serpentine and the amphib« common varieties. • Am phibole g ro u p : actinolite crocidolite and tremolite. S erpentine group: chrysotile. T h e bulk of the asbestos of c 2 H .O , w hich is mined on this eont; of the P rovince of Quebec, Can: am osite also are used commerci Chrysotile occurs as veins in s e r composition, which exists in massiv fibers w ith o u t the parallel orienta massive, bluish black serpentine, w is traversed by veins of fibrous barely perceptible line to 6 (15 c across th e vein and not lengthwis From the Saranac Laboratory of t This series of studies of asbestosis. than twenty years ago by the late Dr. Lt was nearly completed at the time of hi.reports and inform al review.« of some of •’ 2 INDUSTRIAL HYGIENE AND. OCCUPATIONAL MEDICINE Attention is directed to the mineral brucite, MgO.HX), which is often found in the same formations with serpentine and chrysotile and may be fibrous in structure. Except for the manufacture of magnesium, brucite lias no commercial value at present because its fibers are not sufficiently flexible to be used in textiles, but they are capable of repeated longitudinal subdivision. Unlike other asbestiform minerals, brucite is not a silicate, and for this reason it has been a valuable tool in an experimental evaluation of the action of fibrous minerals on lung tissue. exper im enta l asbestosis For many years studies1 have been carried on at the Saranac Laboratory in an investigation of the cause, nature and development of asbestosis. The present paper is devoted to experimental asbestosis, Fig. 1.—Human asbestosis (P-36-144). The photomicrograph reveals a bronchi­ ole (right center) with a smooth muscle bundle at its inferior margin and with an extensive zone of collagen deposition largely obliterating the surrounding alveolar structure. The black foci are macrophages containing incidental pigment. Asbestosis bodies are present but are not apparent at this magnification (X 200). and in it are described the experiments made on animals with various kinds of asbestos dust. Another report, to be prepared and issued at a future date, will be concerned with human asbestosis and will cover the health aspects of workers who have been exposed to asbestos dust in an industrial environment. Although in man asbestosis is a chronic disease with diffuse pulmo­ nary fibrosis which requires years to develop, it is possible to reproduce 1. (a) Gardner, L. U., and Cummings, D. E.: Studies on Experimental Pneumokoniosis: VI. Inhalation of Asbestos Dust; Its Effect upon Primary Tuberculous Infection, J. Indust. Hyg. 13:65 and 97, 1931. (b) Gardner, L. U .: Chrysotile Asbestos as an Indicator of Subtile Differences in Animal Tissues, Am. Rev. Tiilmrr 4S r 7A? 104> I VORWALD ET A L —S " in one or more, species of animal c similar to the lesions of human asb< the experimental animal is relative the characteristic lesions in animal usual industrial environment. Coi ation of the tissue response to inh it is necessary to accelerate the r a ­ tions of dust than would ordinaril conditions of exposure are thus < animal experiments is invaluable it the reaction of the human organist E xperimen F or investigating the tissue rea various asbestos minerals, two ty namely, the inhalation method am experiments, groups of animals— sometimes smaller numbers of r; kept for eight hours a day in a < dimension, in which a cloud of asb paddle in a dust hopper.1* At inanimals are killed and the tissues and the extent of the dust reacti periods up to three years. The inj mine in as short a time as possible a potential capacity to produce ir contact with tissues of the body, dust, either dry or suspended in flui the intraperitoneal, the intratrachea Long term inhalation experim great reliance is placed when estimaconstitute a respiratory hazard to i atmospheric dust may be potential!} experiments, only inhalation proced lie inhaled, pass the natural defens pulmonary tissue in quantities suP methods are useful, however, bee: occurs between the dust particles accurate estimation of the dosage ; dose to produce reaction. The i valuable when one is dealing with it permits observation of the effect o‘ T îssue Si Unlike free silica, asbestos doc organs of all species of animats, table 1 are based on completed obse Ô L L bt1ALIGN AL MEDICINE of various animals (guinea pig, rabbit, rat, mouse, cat, dog, chicken and even tadpole) eventually will produce silicotic nodules but at different rates. Similar introduction of long fiber asbestos has resulted in a fibrous reaction in the lung and, to a lesser extent, in the peritoneum but not in other organs of the guinea pig, the rabbit, the cat and the white rat. In our experience the lungs of the dog and the white mouse failed to respond with fibrosis, although Schuster 2 has reported such changes in a dog that lived in an asbestos-fabricating plant. This variation in species and in organ susceptibility is yet to be accounted fo r3; it is presumed that in the susceptible animals the greater reaction of the lung to asbestos, far exceeding the reaction of other organ tissues, is due principally to the greater mobility of the lung. P eculiar C haracteristics of A sbestos Experience has demonstrated that most of the nonfibrous dust particles inhaled into the lungs of man and animal are 10 microns or less T able 1.— Reaction io Long Fiber Chrysolite in Lungs of Man and Other Species of Animal Species Mao....................... Guinea pig............. Rabbit................... C at........................ White rn t.............. White mouse......... Dog.................... . Mode ot Exposure Inhalation Inhalation and injection Inhalation and Injection Inhalation and Injection Inhalation and injection Inhalation Injection \ Fibrosis * 4+ 2-1+ -i+ 0 0 Asbestosls Bodies Numerous Moderately numerous Rare and atypical Rare and atypical Very rare Rare and atypical None VORWALD L own essential lining is ; name •implies, they act alveoli distributed along change in the character of the respiratory bronc' responsible for retention is well established are a; peripheral air spaces. 1 observation. R ate o f T i The affected tissues quartz dust. For exantj tracheal injection fibrosis one month after injection months or more. Thus, inhaled silica lags behind ; does the evolution of the < difference in the degree exposure to dust. For > nodules of silicosis become period of time, whereas t' short time. Subsequently, process often distorts the a< progressively interfere with * The symbols 0 to 4+ reler to the degree of tissue reaction. in maximum dimension. Larger particles apparently do not gain access to the lungs, because, first, large particles settle in air so rapidly that few remain suspended in the atmosphere breathed and, second, large particles are more effectively removed by the protective mechanisms of the upper respiratory tract. In the case of fibrous materials these factors have less influence and fibers 100 and even 200 microns in length have been found in the terminal air spaces of human lungs. In small labora­ tory animals exposed to asbestos dust the maximum length of fiber found in the lung rarely exceeds 60 microns. A large proportion of nonfibrous particulate dust inhaled into the lung is found in the terminal air spaces (alveolar ducts, atriums, alveoli) in all parts of the organ; in contrast, inhaled asbestos fibers are first discovered in the respiratory bronchioles. These small passages are immediately distal to bronchioles lined bv ciliated epithelium.4 Their 2. Schuster, N. H .: Pulmonary Asbestosis in a Dog, J. Path. & Bact. 34 (pt. 2):751, 1931. ' 3. Vorwald, A. J . : Variations in Individual Susceptibility to Industrial Dusts Inhaled into the Lungs, Am. Rev. Tuberc. 62: (IB) 13, 1950. 4. Miller, W. S .: The Lung, Springfield, 111., Charles' C Thomas, Publisher, 1937. The peculiar structure body” is a specific concern golden yellow, beaded or h; or curved (fig. 2 ). Often o. The bodies vary considera. microns have been recorded It is believed that asbest tein and iron pigment of tis observed reproduction of the sulicutaneous injection of fil abundant in man and in the in the former, probably bo fibers of greater dimension. » 5. Gloyne. S. R .: (a) The : Tubercle 12:398, 1931; (b) The . ner and Cummings.1“ 6. Lynch, K. M., and Smith, J. A. M. A. 9S:659 (Aug. 30) Asbestosis Bodies in the Sputum : Asbestos Mill, J. Path. & Bact. 34 filoviie.5a- b VORWALD ET AL.—STUDIES OF ASBEST0S1S 3 in one or more, species .of animal characteristic tissue changes which are similar to the lesions of human asbestosis (fig. 1). Since the life spart of the experimental animal is relatively short, it is not possible to produce the characteristic lesions in animals under conditions identical with the usual industrial environment. Consequently, to obtain a complete evalu­ ation of the tissue response to inhaled particulate and fibrous material, it is necessary to accelerate the reaction by employing higher concentra­ tions of dust than would ordinarily be encountered in industry. While conditions of exposure are thus different, the information yielded by animal experiments is invaluable in furnishing a better understanding of the reaction of the human organism to inhaled asbestos dust. E xperimental Methods For investigating the tissue reactions of experimental animals to the various asbestos minerals, two types of technic have been employed, namely, the inhalation method and the injection method. In inhalation experiments, groups of animals—up to 100 or more guinea pigs and sometimes smaller numbers of rabbits, cats, dogs, rats or mice—are kept for eight hours a day in a cubical dust room, 8 ft. (2.5 M.) in dimension, in which a cloud of asbestos dust is maintained by a rotating paddle in a dust hopper.1" At intervals during the experiment a few animals are killed and the tissues examined to determine the nature and the extent of the dust reaction. Some animals are exposed for periods up to three years. The injection experiments are used to deter­ mine in as short a' time as possible whether or not a particular dust has a potential capacity to produce inflammatory reaction when in direct contact with tissues of the body. The method involves injecting the dust, either dry or suspended in fluid, into the animal by the intravenous, the intraperitoneal, the intratracheal or another route. Long term inhalation experiments furnish information on which great reliance is placed when estimating the degree to which a dust might constitute a respiratory hazard to industrial workers. Even though an atmospheric dust may be potentially dangerous, as indicated by injection experiments, only inhalation procedures will reveal whether the dust can be inhaled, pass the natural defense barriers of the body and reach the pulmonary tissue in quantities sufficient to cause damage. Injection methods are useful, however, because they make certain that contact occurs between the dust particles and tissues and because they allow accurate estimation of the dosage and of the potential capacity of that dose to produce reaction. The intratracheal method is particularly valuable when one is dealing with fibrous minerals like asbestos, since it permits observation of the effect of the fibers on pulmonary tissue. T issue S usceptibility Unlike free silica, asbestos does not produce specific effects in all organs of all species of animals. The comparative data presented in table 1 are based on completed observations and therefore differ slightlv VORWALD ET AL.—STUDIES OF ASBESTOSIS 5 own essential lining is a low cuboidal type of epithelium but, as their n am e‘implies, they actually function in respiration through lateral alveoli distributed along their walls. Either these alveoli or the abrupt change in the character of the lining epithelium, or the small diameter of the respiratory bronchiole, or the combination of all three factors is responsible for retention of the fiber at this site. Only after asbestosis is well established are appreciable numbers of fibers seen in the more peripheral air spaces. Further explanation is required to clarify this observation. R ate of T issue R eaction to A sbestos F ibers The affected tissues react much- more rapidly to asbestos than to quartz dust. For example, in ratsireceiving asbestos fibers by intra­ tracheal injection fibrosis of a characteristic type is visible as early as one month after injection; for quartz dust the latent period is two months or more. Thus, the development of nodular fibrosis due to inhaled silica lags behind the deposition of dust to a greater extent than does the evolution of the diffuse reaction to asbestos. This results in a difference in the degree of progression which follows termination of exposure to dust. For example, on discontinuance of exposure the nodules of silicosis become larger, to a limited extent, for a considerable period of time, whereas the fibrosis of asbestosis increases for only a short time. Subsequently, the asbestotic fibrous tissue contracts; this process often distorts the adjacent pulmonary tissue and may, as a result, progressively interfere with cardiorespiratory function. A sbestosis Bodif.s The peculiar structure known as the asbestosis body or “curious body” is a specific concomitant of asbestosis.56 The typical body is a golden yellow, beaded or haustrated rod, which may be either straight or curved (fig. 2). Often one or both ends are bulbous like a dumbbell. The bodies vary considerably in length, and dimensions up to 250 microns have been recorded. It is believed that asbestosis bodies are inhaled fibers on which pro­ tein and iron pigment of tissue origin have been deposited.* Gloyne5b observed reproduction of these bodies in guinea pigs nine months after sulxrutaneous injection of fibers rendered free of iron. The bodies are abundant in man and in the guinea pig (table 1) but are much larger in the former, probably because the larger-sized air passages admit fibers of greater dimension. In guinea pigs they form after about 70 days 5. Gloyne. S. R .: (a) The Formation of the Asbestosis Body in the Lung, Tubercle 12:398, 1931; (b) The Asbestosis Body, Lancet 1:1351, 1932. (r) Gard­ ner and Cummings.'“ 6. Lynch, K. M., and Smith, W. A .: Asbestosis Bodies in Sputum and Lung, J. A. M. A. 95:659 (Aug. 30) 1930. Simson, F. W., and Strachan, A. S .: Asbestosis Bodies in the Sputum: A Study of Specimens from 50 Workers in an Asbestos Mill, J. Path. & Bact. 34:1, 1931. Gardner and Cummings.'“ Gardner Glovne.““" *> 6 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE of contact with the tissue. In cats, rabbits and mice a few of the fibers show an atypical coating after much longer residence in the lungs. In rats the bodies are rarely seen, and in dogs none could be found. Although the evidence is incomplete, it appears that the formation of the asbestosis body prevents the fiber from damaging the tissue. Many of the points mentioned above will be elaborated on in subsequent para- VORWALD E T A L .-. INHALATK Four large scale inhalation e: laboratory with various forms of gâtions, more than 160 animals carried on for periods ranging f; four kinds of asbestos dust eni* short fiber, 100 per cent ball-mi K ing ’s F lo.\ T he first inhalation experime: with asbestos dust was begun ii T able 2. — Chemical Anah Type of Asbestos SIOs King's floats............. 39.32 Short fiber............. .. 37.17 Long fiber............. .. 38.40 FesOa AlsOt CfsO: s— "’ "V • 9.00 5.32 1.40 0.78 0.14 • * Not determined. T able 3.—Petrographic Ana King’s Rosts *: The approximate eomp> than 10 microns and reported as percents? serpentine 40, magnetite 12, carbonates is, t 200 microns long were included. Short fiber t: The material, before bell chrysolite and piaty (nonflbrous) serpentine chrysotile 17, serpentine 55, magnetite 10, qi aetinolite and tremolite, 11. Long fiber t: The m aterial consisted v Shreds of nonseparated fibers S to IS micro present. The approximate composition, by netite 5, brueite 2, other minerals, amom minerals, 3. Only a traee of quartz was ot •T h e analysis of the King’s floats asL University, has been reported elsewhere (li eralogy of Asbestos Dust, 3. Indust. Hyg. t For the short fiber asbestos and the supplemented with x-ray diffraction examh; Fig. 2.—A , human asbestosis bodies. This collection of asbestosis bodies was found in the lung shown in figure 1. The usual variations of size and configuration are represented ( x 400). B, guinea pig asbestosis body. This one is similar to some of those shown in A (X400). i graphs dealing with the actual experiments. •••■ ......... rK.-wWI For presentation our .-r-r'iirmc ntv> rlnnlimr yvitli inbnlntion periods up to 33 months. Some exposure lived for an addition: exposure. A preliminary repor months of exposure. A t that tin’ 2)4 years and the conclusions : asbestos dust were provisional, results of the completed study, w Composition and Atmospheric Cone a commercial variety of asbestos kn laboratory with various forms of gâtions, more than 160 animals carried on for periods ranging fi four kinds of asbestos dust emj short fiber, 100 per cent ball-mi K ing ’s F loa The first inhalation experime; with asbestos dust w as begun ii T able 2.— Chemical Analy. Type o i Asbestos StOs King’s floats........... .. 39.32 Short fiber............. .. 37.17 Long fiber............. .. 38.10 Fe=Oa AlsOs Cr-Oa 8*84 9 J0 9 5.32 1.40 0.78 • 0.14 • - Not determined. T able 3.—Petrographic Ana! King’s floats *: The approxim ate eotnpt. than 10 microns and reported as percentage serpentine tf , m agnetite 1 2 , carbonates 18, ti 200 microns long were included. Short flber ): The m aterial, betore beta chrysotile and p la t; (nonflbrous) serpentine, chrysotile IT, serpentine 55, m agnetite 10, qu-. nctinolite and tremolite, 11. Long fiber): The m aterial consisted pri Shreds of nonseparated fibers 5 to 15 micro: present. The approxim ate composition, by netlte 5, brucite 2, other minerals, amonp minerals, 3. Only a trace o f q u a rtz was ob*Thc analysis of the King’s floats act» University, has been rrported elsewhere (II i eralogy of Asbestos Dims, J . Indust. H yg. .' t For the sh o rt liber asbestos and the .. supplemented with x-ray diffraction examln Fig. 2.—A , human asbestosis bodies. This collection o{ asbestosis bodies was found in the lung shown in figure 1. The usual variations of size and configuration are represented (X 400). > B, guinea pig asbestosis body. This one is similar to 7some of those shown in A (X 400). graphs dealing with the actual experiments. For presentation our investigation is divided into two sections, one dealing with inhalation experiments and the other with injection experiments. periods up to 33 months. Some ; exposure lived for an additiona exposure. A preliminary repor months of exposure. A t that tim< 2'/\ years and the conclusions ; asbestos dust were provisional, 'i results of the completed study, wi Composition and Atmospheric Cone. a commercial variety of asbestos kno' fibers, ranging in length from 1 nun. also varied in size. I t was obtained Asbestos Corporation of America, an<< amount of fibrous chrysotile was only t % VO RW ALD ET A L .— S T U D I E S . O f A X B h à W à là / IN H A L A T IO N . E X P E R IM E N T S * F o u r large-scale inhalation exp erim en ts have been conducted in this laboratory w ith various form s o f asb estos dust. In each of these in vesti­ ga tio n s, m ore than 160 anim als w ere used, and the experim ents w ere carried on for periods ranging from tw o to m ore than five years. T h e fou r kin d s o f asbestos dust em ployed are designated as K in g's floats, sh o rt fiber, 100 per cent ball-m illed, and lo n g fiber asbestos dust. K ing ’s F loats A sbestos D ust T h e first inhalation experim ent conducted at the Saranac L aboratory w ith a sb estos dust w as begun in 1928. A n im als inhaled the d ust for T able 2.— Chemical A nalysis o f A sbestos D usting M aterials Type of Asbestos SIOs FesOa AlsOs CrsOs MnO V J * • 8.84 King’s B oats........... .. 39.32 9.09 1.40 Short fiber.............. .. 37.17 0.14 0.09 * Long fiber.............. .. 38.40 5.32 0.78 0.03 CaO 0.67 0.85 0.31 MgO 35.56 35.96 40.18 NasO K ;0 • • • 0.14 0.06 0.20 0.06 0.98 0.57 CO* Igni­ tion Loss T otal 12.74 14.09 14.00 97.13 100.11 99.76 • Not determined. T able 3.— Petrographic Analysis of A sbestos D usting M aterials King’s Boats *: The approxim ate composition, based on particles (except chrysotlle) smaller th a n 10 microns and reported as percentages obtained from particle counts, was chrysotlle 14, serpentine 40, m agnetite 12, carbonates 18, talc 12, other m inerals 4. F or chrysotlle, fibers up to 200 microns long were Included. S hort fiber t: The m aterial, before being ball milled, contained a preponderance o f fibrous chrysotlle and p laty (nonfibrous) serpentine. The approxim ate composition, by percentage, was chrysotlle 17, serpentine 55, m agnetite 10, quartz 2, brucite 5, other minerals, including dolom ite, actinolite and trem ollte, ll. L ong fib erf: The m aterial consisted principally of the fibrous asbestos m ineral chrysotlle. Shreds .of nonseparated fibers 5 to 15 microns in diam eter and up to 50 microns In length were, present. The approxim ate composition, by percentage, was chrysotlle 75, serpentine 15, mag* netlte 5, brucite 2, other minerals, among which were calclte and ehloritlc and micaceous minerals, 3. Only a trace of q uartz was observed. • T h e analysis of the King’s floats asbestos, m ade by Dr. O. 8. Ilurlbut J r., of H arvard University, lias been reported elsewhere (U urlbut, C. 8., J r ., and Williams, C. R.: The Mlu* eralogy o f Asbestos Dust, J . Indust. Hyg. & Toxicol. 17: 292, 1935). t F o r the sh o rt fiber asbestos and the long fiber asbestos the petrographic analysis was supplemented with x-ray diffraction exam ination. period s up to 3 3 m onths. S om e guinea p igs w ith six and nine m onths' ex p o su re lived for an additional three years after cessation o f their ex p o su re. A prelim inary r e p o r tla presented observations after 2 9 m on th s o f exp osu re. A t that tim e observations covered a period of only 2 % y ears and the conclusions as to the ultim ate effects of inhaled asliestos d u st w ere provisional. T h o se conclusions are substantiated by resu lts o f the com pleted study, w hich is reported as follow s. Composition and Atm ospheric Concentration of the Dust.—T he dusting m aterial, a com mercial variety of asbestos known as K ing’s floats, was composed of sh o rt fibers, ranging in length from 1 mm. to 1 m icron o r less, and of particles which also varied in size. I t was obtained from the Thetford, Quebec, plant of the Asbestos C orporation of America, and analyses (tables 2 and 3) reveal th a t the am ount of fibrous chrysotile was only 14 per cent, a rath er low value.- 8 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE Impinger samples taken soon after the experiment was started indicated that the dust concentration was at first quite low, the average dust count being only 6.0 million particles per cubic foot of air by the standard light field technic and 0.8 million for particles and fibers greater than 10 microns. After the inhalation experiment had been under way for about two years, the speed of the rotating paddle in the dusting machine was increased and for the remaining 10 months of the experi­ ment considerably more dust was dispersed into the atmosphere. The average dust count of impinger samples collected after this change was 53.7 million by the usual light field method and 1.6 million for particles and fibers larger than 10 microns. It is probable, however, that the true values of the dust concentration were higher than the counts given in this paragraph. The impinger samples for the King’s floats experiment were collected in water, but later studies7 have shovim that counts of impinger samples of asbestos dust taken in water are not reliable. Ethyl alcohol instead of water was used as the collecting fluid in all subsequent experi­ ments. VORWAL were phagocytosed, ai cells. Mononuclear lei ing of the bronchiolar v The process evolved fibers steadily increase- T able 4.—Summary of Inhalation Experiment with King’s Floats Asbestos Dust Nature of Experiment Dust exposure continuous throughout life Dust exposure followed by prolonged residence in normal air Tuberculous infection * a t sta rt of dust exposure Controls to Infection: no dust cximsurc Tuberculous Infection * after 2B mo. of dust exposure, then residence in normal air Controls to Infection: no dust exposare Animals 54 guinea pigs Urabbits 18 rats 23 guinea pigs 25 guinea pigs l rabbit 1 rabbit to guinea pigs Maximum Maxi- Survival mum After Dust Ex- Dust Ex­ posure, posure, Mo. Mo. 33 0 19 0 0 6 6 35 » 37 30 f 6 34 j 19 35 0 * Résulta Typical peribronchiolar fibrosis after 16 months Foreign body bronchitis Little or no reaction Nonprogressive fibrosis Nonprogressive fibrosis Absorption of foreign body reaction Temporary progression of Infection, followed by healing with fibrosis .Healing by resolution (one exception) 22 guinea pigs 0 35 f 12 guinea pigs 26 14 No appreciable Increase In susceptibility to tuberculous infection; healing with fibrosis 12 guinea pigs 0 i# t Healing by resolution • The guinea pigs were infected with tow virulence Ri strain of tubercle bacillus, t This means the survival period following infection. Results of the investigation, briefly summarized in table 4, show that inhalation • of King’s floats asbestos dust produced a typical peribronchiolar fibrosis in guinea pigs but not in rabbits or rats. Reaction in Normal Guinea Pigs.—Guinea pigs inhaling this dust for periods up to 33 months hadja characteristic fibrosis occurring in conical patches about the respiratory bronchioles. During this exposure the peripheral alveoli were not involved. The particulate elements of the dust were transported through the lymphatic system to the bronchial nodes, causing no significant reaction in either site; the fibrous elements remained fixed at the points of original localization and were seldom detected in the lymph nodes. After exposure of approximately a year a small amount of cellular reaction had been produced about many respiratory bronchioles (fig. 3 A ) . As more dust was inhaled, it continued to accumulate in the same location, and later stages of the disease (fig. 3 B ) consisted of extensions of the original lesions. Apparently, the inhaled fibers were caught in the pocket-like alveoli that are given off from the lateral walls of the respiratory bronchioles. There they 7. Fulton, W . B.; Houtz, R. L .; Dooley, A., and Mathews, J. L .: Asbestosis: I. The Collection and Counting of Asbestos Dust Encountered in Asbestos Fabri­ cating Plants, Special Bulletin 37, Pennsylvania Department of Labor and Industry, Harrisburg, 1934. Fig. 3.—King's floats i months' exposure. It inch becoming an alveolar duel wall of the bronchiole am. with 28 months’ exposure peribronchial fibrosis extern epithelium lining these al (X 200). d isto rte d the rdveolî -»»»-* VORWALD' ET AL.—STUDIES OF ASBESTpSIS 9 were phagocytosed, and many of them were carried into the wall by migratory cells. Mononuclear leukocytes attracted to the area caused an appreciable thicken­ ing of the bronchiolar wall. After 16 months a delicate fibrosis made its appearance. The process evolved gradually, and the number of fine intercellular collagenous fibers steadily increased. As this fibrous deposit contracted, it partially closed and Fig. 3.—King's floats inhalation experiment: A , lung of a guinea pig with 12 months' exposure. It includes a respiratory bronchiole, at the left, branching and becoming an alveolar duct, at the right. Note the accumulation of cells in' the wall of the bronchiole and in adjacent-alveoli (X 130). B , lung of a guinea pig with 28 months’ exposure. The field includes a bronchiole, at the center, vvith peribronchial fibrosis extending into the walls of adjacent alveoli. Note the cuboidai epithelium lining these alveoli. This is the so-called “adenomatoid” appearance (X 200). distorted the alveoli -'-’'t chronic pulmonary inflammation resulting from many causes. Willis * described a similar structure in the lungs of guinea pigs inhaling silicon carbide. The longer asbestos exposures resulted only in more thickening of the walls of the air spaces, largely due to an increase in the amount of fibrosis. The fibrous tissue always remained cellular and failed to show the hyalinization characteristic of silicosis. Fig. 4.—King’s floats inhalation experiment: A , lung of a guinea pig with six months’ dust exposure followed by 35 months’ inhalation of normal air. The reaction is rather slight, but distinct fibrosis is present ( X 200). Note tliat 28 months of continuous exposure (fig. 3 B ) produces much more extensive reaction. B, lung of a guinea pig exposed to the asbestos dust for nine months and liv in g th e r e a fte r in n o rm a l a ir fo r 37 months. The reaction shown is more than that in A but much less than the reaction in figure 3 B ( x 200). 8. Willis, H . S., and Brutsaert, P .: Tumor-like Structures in the Lungs of Guinea Pigs Artificially Exposed to Silica Dust, Am. Rev. Tuhcrc. 17:268, lO-’.o V01erc. 54:51, 1946. 12 IN D U S T R IA L H Y G IE N E AND O C C U P A T IO N A L M E D IC IN E VORW ALD ET A t, months, lived in normal air for more than two years. A t autopsy neither animal showed any evidence of cellular reaction or fibrosis in the terminal bronchioles, nor were there any asbestosis bodies. their lungs. In a few of the rats, but there was no fibrosis. T his pi cessful. Reaction in W hite R ats.—All the rats had acquired an infection, resulting in the formation of pulmonary abscesses, before they came to autopsy. Apparently, so much heavy mucus obstructed their bronchi that very few fibers could have entered • S u m m a ry and Interpretatio F loats D u st.— T he findings in t be sum m arized under tw o hea< 1. Effect of the inhaled « floats dust caused a charactei pigs but not in rabbits o r rats, in extent after the dust exposur 2. Effect of the inhaled dust pigs infected with attenuated d u st room, the results were m m ent of this type. A few anin infection; in most of them ther w ith subsequent healing; in on< active to death. In contrast, v exposed to quartz dust instear continues to progress and eve: O n the other hand, infected ani oxide do not show any proginfected with attenuated tuber years’ asbestos dust exposure only modification o f the infect: being retained in the peribn form ing there in addition to In view of the variability < response and the high proport monia, it is felt that only tern asbestos dust on the course of experim ent. S hort F r _ Fig. 5.—King’s float inhalation experiment: A , lung of guinea pig infected with Ri tubercle bacilli and then exposed to dust for 24 months. A bronchiole is shown just above center. Surrounding it is some collagen deposition, together with typical epithelioid cell infiltration of the wall. Note the lack of encapsulation and the peripheral epithelioid cell pneumonia, which illustrate a spreading tuber­ culous process (X 2 0 0 ). B, lung of a guinea pig infected with Ri tubercle bacilli and then exposed to dust for 35 months. _Note the subplcural distinctly encapsulated caseous focus, the calcification at the right border of the lesion and the absence of cells in adjacent alveoli, all of which illustrate a healing tuberculous process (x 2 0 0 ) . Since hazardous dusts like fibrosis when the particles are experim ent was performed to for asbestos dust. It was th consisting almost entirely of fil would initiate an accelerated t reaction in a shorter time thai tained fibers from 1 mm. to 1 r particulate m atter. Composition and Atmospheric C. for this experiment was the remain fabricating plant after a carding o]10 10. Vorwald. A. J . ; P ratt, P . C .. D. A .: Siderosis: A Benign Pneutni Indust. Afed. * Surg. 19:170. 1<)?0. VORWALD ET At..—STUDIES OF ASBESTOSIS 13 their lungs. In a few of the rats, an occasional asbestosis body was discovered, but there was no fibrosis. This phase of the experiment was considered unsuc­ cessful. • Summary and Interpretation of Inhalation Experiment with King’s Floats Dust.—The findings in the experiment with King’s floats dust can be summarized under two headings: 1. Effect of the inhaled dust on normal animals. The King’s floats dust caused a characteristic peribronchiolar fibrosis in guinea pigs but not in rabbits or rats. The fibrosis did not increase significantly in extent after the dust exposure was discontinued. 2. Effect of the inhaled dust on tuberculosis in guinea pigs. In guinea pigs infected with attenuated tubercle bacilli and then placed in the dust room, the results were more variable than is usual in an experi­ ment of this type. A few animals showed no sign of progression of the infection; in most of them there was evidence of temporary progression with subsequent healing; in one animal the tuberculous process remained active to death. In contrast, when guinea pigs after being infected are exposed to quartz dust instead of asbestos dust, the infectious process continues to progress and eventually causes the death of the animals. On the other hand, infected animals exposed to a harmless dust like iron oxide do not show any progression of the infection.10 Guinea pigs infected with attenuated tubercle bacilli after the termination of two years’ asbestos dust exposure did not show progressive disease. The only modification of the infection was in its localization, a few bacilli being retained in the peribronchiolar fibrous tissue, with tubercles forming there in addition to the usual tubercles beneath the pleura. In view of the variability of the results, the unusual nature of the response and the high proportion of deaths due to intercurrent pneu­ monia, it is felt that only tentative conclusions as to the influence of asbestos dust on the course of tuberculous infection aire justified by this experiment. S hort F iber A sbestos D ust Since hazardous dusts like quartz are most effective in producing fibrosis when the particles are 3 microns and less in size, an inhalation experiment was performed to determine whether this condition is true for asbestos dust. It was thought that a short fiber asbestos dust consisting almost entirely of fibers and particles smaller than 3 microns would initiate an accelerated tissue response and produce an advanced reaction in a shorter time than did the King’s floats dust, which con­ tained fibers from 1 mm. to 1 micron and less in length as well as much particulate matter. Composition and Atmospheric Concentration of the Dust.—The dusting material for this experiment was the remains of fibers collected in dust bins of an asbestos- • fabricating plant after a carding operation and screened to pass 200 mesh. Since10 10. Vorwald. A. J . ; Pratt, P. C .; Durkan, T. M .; Delahant, A. B„ and Bailey, D. A.: Siderosis: A Benign Pneumoconjosis Due to the Inhalation of Iron Dust, Indust. Med. & Surg. 19:170. 1950. VORWALD Ei 14 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE Only after exposures ha< appreciable tendency for du 16 months phagocytes had < bronchioles which revealed cells. There were also son foreign body type. A t 20 ti prominent, and sometimes cl o r “adenomatoid’’ appearance ing the experiment with the ! of the series the reaction development of fibrous tiss iagen was pale in color an< Diffuse chronic pleurisy wa the material as received contained many long libers, it was ground in a steel ball mill to reduce practically all the particles to 3 microns or less in size. When used alone in the standard dusting machine, this finely ground asbestos tended to pack in the hopper, and it became necessary to mix one volume of the unground material with three volumes of the ground to generate a satisfactory dust cloud. It is pertinent to mention here that the addition of the small quantity of unground asbestos was unfortunate, because it confused the interpretation of results. The composition of the short fiber asbestos as received is disclosed by the chemical and petrographic analyses given in tables 2 and 3. Samples taken before and after grinding yielded about the same values on analysis, indicating that there was no contamination from the mill or loss of water content. The dust concentration varied during the experiment, the light field counts for atmospheric samples collected inside the animal cages with the impinger apparatus ranging from 83 million to 182 million. The average of counts was 130 million for the first year of the experiment, 134 million for the second year and 140 million for the third year. Size-frequency measurements of air-floated dust from inside the cages at a magnification of 1,300 X revealed a great preponderance of fine particles, nearly*10 T able 6.— Analyses o f Lu- s Exposure to Dust, Mo. Period in Normal Air, Mo. 12 0 15 0 20 0 24 0 30 ° T able 5.—Summary of Inhalation Experiment witk Short Fiber Asbestos Dust Mature ot Experiment Dust exposure continuous through­ out life Animals 46 guinea pigs 73 rats 18 cats 7 rabbits Dust exposure followed by prolonged residence In normal air 13 guinea pigs Scats 1 rabbit Maximum Maxi- Survival mum After Dust Ex- Dust Ex­ posure, posure. Mo. Mo. Results 34 Rate of reaction about the same as in experi­ 0 ment with King's floats asbestos but extent of involvement very much less t 32 0 Characteristic patches of peribronchiolar fibro­ sis; no asbestosis bodies 54* 0 Subpleural reaction only No fibrosis seen grossly; microscopic evidence 47* 0 of alveolar wall thickeniug after 46 months’ exposure 20 14 Progression after removal from dust doubt­ ful—neither clearly established nor definitely excluded 31 24 Same as for continuous exposure 62* « Similar to continuous exposure; evidence of slight regression 34 * After 33 months the animals were exposed to 100 per cent hall-milled asbestos. t The reaction was probably due to long fibers in the unground material which was mixed with the ground asbestos dust to produce a satisfactory dust cloud. 90 per cent of the particles seen being smaller than 3 microns. It was estimated that approximately 1 per cent of the dust was in the form of fibers greater than 10 microns in length. ! Four species of animals—guinea pigs, white rats, cats and rabbits—were used in this experiment. The results of the dust exposure, summarized in table 5, are presented in greater detail below. ' Reaction in Guinea Pigs.—Eighty guinea pigs were originally placed in the dust room, hut 21 of them were later eliminated from the experiment and killed because of enlargement of the cervical lymph nodes thought to be due to intercurrent infection of the upper respiratory tract. Of the other 59 animals, 46 remained in the dust room until they were killed or died at periods up to 34 months, and 13 animals were transferred to normal air after being exposed to the dust for 20 months. The type of tissue reaction provoked by the inhaled short fiber asbestos was essentially the same as that already observed in the experiment with King’s floats asbestos. The rate of reaction also was approximately the same, but the extent of involvement was very much less. After 16 to 24 months of exposure only a very r . . n f .r . < " •. • • • | j , I> Dust ; ° Dust Exposure Fo) 20 • 20 10 20 A ! ' ( M 1 * The symbols averaging the ti the relative degree o t reaction, raexperiment). The relationships a symbols In other tables. monary infection. This sugg asbestosis, but the evidence is of the tracheobronchial lympli experiment with King’s floats been transported to the nodes reaction was essentially an in< original cells being preserved i In the group removed to no: sion of disease was not definit disproved, owing to the vari. reactions, from mild to sever» the length of time after cessa to- variation in individual sus chemical analyses (table 6 ), wh in lungs with widely different VORWALU ET AL.—STUDIES OV ASBESTOSIS 15 Only after exposures had continued for approximately one year was there an appreciable tendency for dust-containing phagocytes to gather into clumps. By 16 months phagocytes had collected about the walls of a few of the respiratory bronchioles which revealed a little proliferation or infiltration of mononuclear cells. There were also some multinucleated cells, but they were of the inert, foreign body type. At 20 to 24 months the cellular clumps were sometimes quite prominent, and sometimes changes in the epithelium resulted in the adenoma-like or “adenomatoid’’ appearance (fig. 3 B ) previously described in the section review­ ing the experiment with the King’s floats dust. In most of the subsequent members of the series the reaction remained cellular, but a few exhibited pronounced development of fibrous tissue. In these few members of the series the col­ lagen was pale in color and tenuous, with no appearance of being hyalinized. Diffuse chronic pleurisy was present in a few animals without evidence of pulT able 6.—Analyses of Lungs of Guinea Pigs After Prolonged Inhalation of Short Fiber Asbestos Dust Exposure to Dust, Mo. 12 IS 20 24 30 34 20 20 20 Period In Normal Air, Mo. Amount of Total Total SIO-, Ash, % of 810s, % of Tissue % ot Ash Reactlo Dried Lung Dried Lung Dust Exposure Continuous During Life 10.23 0.61 5.02 10.08 0 0.46 4.53 10.54 0414 5.16 ± 9.96 0.49 5.00 9.00 4.76 0.43 0 ± 0.53 10.60 4.05 14.46 0.85 5.86 0 14.07 2+ 0.90 6.43 14.48 ' 0.78 5.42 0 3+ 14.20 0.78 5.50 17.89 5.35 0.96 0 4+ 19.46 ; 6.55 1.27 12.37 6.06 0.75 A V 4+ 6.35 15.11 0.96 Dust Exposure Followed by Prolonged Residence In Normal Air 9.30 0.48 1 5.16 4 7.16 2+ ! 5.11 0.36 1 6.11 10.21 0.62 10 8+ 0.34 8.51 t 3.98 5.31 4.77 0.25 14 5.00 ! 6.18 0.26 2+ 4.77 0.22 4.60 * The symbols averaging the tissue reaction In each group ot guinea pigs represent merely the relative degree of reaction, ranging from ± (questionable) to 4+ (the maximum for this experiment). The relationships apply only within this table and cannot be compared with symbols In other tables. monary infection. This suggests that pleurisy may be a specific concomitant of asbestosis, but the evidence is not adequate to establish this point. The reaction of the tracheobronchial lymph nodes was more pronounced than in the previous experiment with King’s floats asbestos, probably because more fine particles had been transported to the nodes in animals inhaling short fiber asbestos. The nodal reaction was essentially an increase in reticulum, rather than a fibrosis, with the original cells being preserved between the thickened reticular fibers. In the group removed to normal air after 20 months’ inhalation of dust, progres­ sion of disease was not definitely demonstrated, but neither could it be absolutely disproved, owing to the variability of the response in different animals. The reactions, from mild to severe, occurred sporadically and bore no relationship to the length of time after cessation of exposure. The differences were attributed to' variation in individual susceptibility. This view received support from the chemical analyses (table 6), which revealed comparable amounts of ash and silica in lungs with widely different amounts of tissue change. For example, the ash 16 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE and silica values were quite similar for three animals living in dust 20 months and then in normal air for 14 months, yet the tissue reaction was severe in one animal, mild in another and only doubtful in the third. The formation of asbestosis bodies was at first extremely limited in both groups. After five months’ exposure only a very rare short body could be found, usually inside a cell. Some of the finest intracellular particles were surrounded by yellow deposits having the same color as the asbestosis body. One year’s exposure had per­ mitted an accumulation of many longer fibers, a number of which were coated and seen as typical asbestosis bodies. Most of these were still short enough to be partially or entirely within phagocytic cells. By the twentieth month and thereafter they T able 7.—Analyses of Lungs of While Rats That Had Inhaled . Short Fiber Asbestos Dust Duration of Exposure, Mo. Amt. ot Ash, % ot Dried Lung 3.9 4.3 0* 2.9 3.6 3.3 3.9 3.4 '3.5 3.6 4 2.9 U .2 3.3 3.« L3.4 Total SIOs, % of Dried Lung 0.00 0.00 0.00 0.00 0.00 0.00 0.00 o.os 0.13 0.0» 0.05 0.08 0.11 oxn Total 8102, % Of Ash 0.0 : * 0.0 > Duration of Exposure. Mo. 0.0 2.1 8 0.0 0.0 0.0 0.0 6 f 3.9 3.3 3.2 1.5 2.3 3.0 2.2 Amt. of Total Ash,% StOî, % of Dried of Dried Lung Lung f 8.3 0.07 { 3.4 0.03 [ 3.7 )' 0.04 10 { 3.5 4.4 1 3.7 0.08 0.18 0.15 0.17 0.16 (4.0 I 4.8 1 5.3 1.4.7 0.18 0.15 0.15 0.13 8.6 1 Total 8 IO2, % of Ash 2.1 1.5 i.i 2.2 5.5 3.4 4.0 4.2 3.8 3.3 2.8 2.8 * Normal controls (no dust exposure). T able 8.—Average Values of Ash and Total Silica for Lungs of White Rats Inhaling Various Dttsts for Various Periods (Lungs Only, Without Included Lymph Nodes) Amt. ot Ash, % ot Dried Lung Total SiOi, % of Dried Lung Total SIOs, % of Ash Dura­ tion Short Gypsum- Short Gypsum- Short Gypsumof Ex- Fiber Ferra- Quartz Fiber FerruJ , Quartz Fiber Ferru- Quartz posine, Asbes­ ginous Mix­ Asbes­ ginous ’ Mix­ Asbes­ ginous Mix­ tos Quartz Chert ture Mo. tos ture tos Quartz Chert ture Quartz Chert 3.3 4.3 2 0.09 051 . 0.25 0.06 11.7 5.» :, 2.» 2.6 3.9 2.6 4 3.4 3.8 0.51 0.32 0.07 3.6 4.5 0.09 2.5 11.4 2.0 8.» 34.4 3.5 3.4 3.45 1.6 41.5 6 7.1 0.05 2.94 0.11 3.4 9.» 26.5 29.4 9.0 0.15 0.32 3.9 8 4.6 3.6 9.1 3.8 1.44 2.40 43.2 0.15 4.40 6.09 0.23 3.2 56.6 10 4.9 6.7 7.8 14-1 , 4.1 were relatively numerous although still rare in comparison with the findings in the King’s floats experiment. Reaction in White Rats.—Seventy-three white rats were exposed to atmospheric short fiber asbestos dust lor periods up to 32 months. During the first 10 months animals were killed bimonthly and for the remainder of the experiment at less frequent intervals. Up to eight months the dust cells were widely scattered and existed in foci only sporadically. Reaction was limited to occasional slight thicken­ ing of the- septums about small accumulations for periods up to 20 months a: species did even a suggestion phagocytosis of inhaled partic free in air spaces or were tra asbestosis bodies were found small, nonhaustrated forms wi; T able 10.—Analyses of Lun< Experiment with 1< Exposure to Dust, Mo. Period Id Normal Air, Mo. i 0 2 0 3 0 6 0 8 0 12 o ; 16 ° i 20 0 ! ° ; A Di D ust f 1 24 i Dust Exposure Fol 28 28 28 2 ) 8 1 12 | * The symbols averaging the degree of reaction, ranging from o experiment). The relationships at symbols in other tables. Summary and Interprc Cent Ball-Milled Asbestos Fig. 6.—Ball-milled asbestos inhalation experiment: A , lung of a guinea pig w ith 24 m o n th s’ du st exposure. A bronchiole is show n a t th e c en ter, w ith a slight accumulation of phagocytic cells but without the formation of collagen ( x 200). B, lung of a guinea pig with 28 months’ dust exposure and then 12 months’ inhalation of normal air. The reaction is much like that shown in A , but there is a slight deposition of collagen, most apparent at the left ( x 200). value for total silica, per cent of ash, was 25.37. This should be contrasted with the average value of 14.34 (table 6) for animals exposed 24 months to the short fiber asbestos dust. experiment was not as int< short fiber asbestos. The e x te n s iv e e v e n th o u g h m o r were fewer fibers longer experiment, the results tei summary of the previous primarily chemical in natir tion in size of asbestos fib«., asbestos inhaled into the lut VORWALD ET AU.—STUtìlES OF AS B EST OS IS 21 In view of the high values for silica obtained with the animals exposed to 100 per cent ball-milled dust, it is important to note that their pulmonary response was much less than that of animals exposed for 24 months to the short fiber asbestos in the previous experiment. This again indicates that the biologic activity of asbestos inhaled into the lung is not increased by a reduction in size of the fibers. Reaction in White Rats and Mice.—In this experiment 40 rats were exposed for periods up to 20 months and 24 mice for periods up to 12 months. In neither species did even a suggestion of asbestosis develop, and reaction was limited to phagocytosis of inhaled particles by widely scattered dust cells which remained free in air spaces or were transported to the tracheobronchial lymph nodes. No asbestosis bodies were found in the rats, but in the mice there were a very few small, nonhaustrated forms within phagocytes. T able 10.—Analyses of Lungs of Guinea Pigs Exposed to Dust in Inhalation Experiment with 100 per Cent Ball-Milled Asbestos Dust Exposure to Duet, Mo. 1 Î s 5 8 12 16 20 24 28 28 Period Amt. of Total Id Normal Ash, % of SIOs, % ot Total SlOt, Tissue Air, Mo. Dried Lung Dried Lung % of Ash Reaction * Dust Exposure Continuous During Life 4.85 0.21 4.26 4.30 0 0.30 7.05 4.35 0.24 6.60 0 4.60 0.23 4.90 0 4.60 0.34 7.40 0.61 $.05 12.01 0 0.70 5.60 12.47 5.07 0.32 0 6.38 0.56 5.74 ».77 0 0.38 5.10 7.51 5.08 0.38 7.17 0 0.3» 7.72 0 5.02 11.86 0 4.35 0.52 0 3.65 1.25 22.16 6.24 1.45 0 23.28 0 1.02 5.40 18.96 + 1.11 21.95 5.01 0 22.00 5.65 1.28 ± 1.28 5.20 24.61 6.30 1.85 20.06 " t 5.56 1.21 21.70 Dust Exposure Followed by Prolonged Residence In Normal Air i 7.25 1.57 21.63 » 8.07 2.19 + 25.24 i 5.25 0.68 12.99 , 0.87 ! 5.96 14.55 + \ 6.38 0.84 13.08 12 6.17 2+ 0.61 12.41 * The symbols averaging the tissue reaction In each group represent merely the relative degree of reaction, ranging from O t o ± (questionable) to 2+ (the maximum observed In this experiment). The relationships apply only within this table and cannot be compared with symbols in other tables. Summary and Interpretation of Inhalation Experiment with 100 per Cent Ball-Milled Asbestos Dust.— The tissue reaction observed in this experiment was not as intense as that in the previous investigation with short fiber asbestos. The reaction was slower in development and less extensive even though more dust accumulated in the lungs. Since there were fewer fibers longer than 3 microns in the material used in this experiment, the results tend to confirm th e in te rp re tatio n made in the summary of the previous short fiber experiment that the reaction is not primarily chemical in nature, and to support the impression that reduc­ tion. in size of asbestos fibers does not increase the biologic activity of asbestos inhaled into the lung. 22 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE The finding of long asbestosis bodies in animals that had inhaled the ball-milled material is an example of the difficulty of completely eliminat­ ing long fibers from a large volume of asbestos as required for an inhalation experiment. In regard to the progression of the tissue reaction after the animals had been removed from the dust, observed in this experiment but not in the others, the following interpretation is offered: When the reaction is well developed at the termination of exposure, the contraction of the fibrous tissue obscures any progression that may have occurred; in this experiment, however, since the reaction observed was less mature, its subsequent progress was more readily apparent. L ong F iber A sbestos D ust Since inhalation of short fiber and of 100 per cent ball-milled asbestos dust did not result in acceleration of the tissue reaction in comparison with that produced by King’s floats, the hypothesis that short fibers of asbestos were of minor importance in the etiology of asbestosis was given added support, and attention was directed, to the view that the long fibers were of primary significance in that etiology. The King’s floats asbestos used in the first inhalation experiment had a rather low content of fibrous chrysotile and contained considerable serpentine and other impurities. Therefore, it was decided to conduct a new inhalation experiment with a purer form of chrysotile which would be richer in long fibers. ( •m position ami Atm ospheric Concentration of the Dust.—The dusting m aterial employed in this investigation was obtained front an asbestos fabricating plant. Samples of several varieties of long fiber asbestos dust were first submitted to the Saranac Laboratory for examination, and one of these, which was low in magnetite and chromite and had a fibrous content estimated to be about 75 per cent, was selected as most suitable. Steel wire brushes, fastened to the inside surface of the hopper and to the rotating paddle as in the preceding inhalation experiment, were used to open up the bundles of asbestos and liberate more fibers into the atmosphere. T he composition of the long fiber asbestos used is indicated by the chemical and petrographic analyses given in tables 2 and 3. Analysis of air-suspended m aterial from the dust room disclosed that about 60 per cent of the long fiber dust was chrysotile and about 20 per cent serpentine; as already noted, the composition of a sim ilar air-floated sample of ball-milled, short fiber dust was 15 per cent chrysotile and 60 per cent serpentine. T he dust concentration as revealed by impinger samples taken inside the animal cages was much lower than the concentration for the experiments with short fiber o r ball-milled dust. F o r the first year of the experiment with long fiber asbestos the average of the light field counts was 32 million particles per cubic foot of a i r ; for the second year, 48 m illion; for the third year, 39 million, and for the fourth year, 43 million. / T he size-frequency of atm ospheric samples of the long fiber asbestos dust and of the ball-milled dust is shown in table 11. Both samples were collected w ith the electrostatic precipitator. I t will be noted that there was far more fibrous m aterial in the long fiber dust. Guinea pigs, cats, rats and mice were employed in this inhalation experiment. UPATIONAL MEDICINE 1 animals that had inhaled the fliculty of completely eliminatasbestos as required for an -sue reaction after the animals 1 in this experim ent but not in offered : W hen the reaction is ■osure, the contraction of the iat may have occurred; in this )bserved was less mature, its parent. VORWALD ET A L .S T U D I E S OF ASBESTOSIS 23 Reaction in Guinea Pigs.—The experiment was started with 100 guinea pigs. After exposure had been carried on for a year, a severe epidemic of pneumonia arose in the dust room and about one third of the animals died or were killed. To replace them, 38 more guinea pigs were added to the surviving group. Histological examination revealed lesions in the lungs after eight months of dust exposure, consisting of cellular connective tissue about the terminal bronchioles (fig. 7 A ). At 12 months there were adenomatoid changes in the adjacent parenchymal areas, and by the sixteenth month (fig. 7 B ) definite fibrosis was present in these areas as well as around the bronchioles. The fibrous lesion could be seen macroscopically at 20 months. From this time on the reaction increased in extent and in the amount of collagen, and by the thirty-fourth month, it had fanned out T able 11.—Size-Frequency of Atmospheric Long Fiber and 100 per Cent Ball- Milled Asbestos Dust Collected Inside Cages s D ust JO per cent ball-milled asbestos tissue reaction in comparison hypothesis that short fibers of lie etiology of asbestosis was directed^ to the view that the in that etiology. The K ing’s experiment had a rather low d considerable serpentine and d to conduct a new inhalation which would be richer in long ■/ the Dust.—The dusting material om an asbestos fabricating plant. >s dust were first submitted to the these, which was low in magnetite ted to be about 75 per cent, was fastened to the inside surface of e preceding inhalation experiment, and liberate more fibers into the used is indicated by the chemical nd 3. Analysis of air-suspended 60 per cent of the long fiber dust : as already noted, the composition short fiber dust was 15 per cent er samples taken inside the animal >r the experiments with short filter -eperiment with long fiber asbestos lion particles per cubic foot of a ir; ear, 39 million, and for the fourth I ■ of the long fiber asbestos dust 11. Both samples were collected noted that there was far more •ved in this inhalation experiment. Grains, % Fibers, % ,------------- *------------- ,,---------*---------, Type of Asbestos Long «ber................... Ball-milled ................. < 3 Microns «5.4 *0-6 8-10 > 10 < 10 Microns Microns Microns 1,1 0.0 25.8 4.8 0.0 0.8 > 10 Clumps, Microns % 6.7 1.0 0.6 3.2 Total 100 100 T able 12.—Summary of Inhalation Experiment with Long Fiber Asbestos Dust Nature of Experiment Dust exposure con­ tinuous throughout life Dust exposure loJlowed by pro­ longed residence in normal air Animals 117 guinea pigs 4 cats 20 rats 20 mice 12 guinea pigs Maximum Maxi­ Survival After mum Dust Dust Expo­ Expo­ sure, sure, Mo. Results Mo. 0 Definite fibrosis In 16 mo. 36 0 Slowly developing fibrosis first seeo 42 a t 24 mo. 0 Marked peribronebiotar fibrosis first 2» seen a t 24 mo. 0 Limited reaction; no fibrosis 25 14 Clearing of inflammatory reaction 20 and definite contraction of fibrous 9 guinea pigs 27 9 Scats 18 24 tissue C'earing of inflammatory reaction and slight contraction of fibrous tissue Similar to continuous exposure group; suggestion of progression in one of tbe two animals considerably into the parenchyma (fig. 8 A ) . The lesions were rather sharply localized and the extensions from different bronchioles showed no tendency to fuse, even in animals exposed for the maximum period of three years. Although the intrapulmonary reaction sometimes reached the pleura, there was no involve­ ment of that membrane. Emphysema was not detected at any point. Some thicken­ ing of the larger bronchi with a chronic inflammatory infiltration was revealed, but it was considered no more than would be produced by a similar period of inhalation of any dust. In guinea pigs exposed to the dust for 20 months and then removed to normal air, there was a marked tendency for cellular inflammatory reaction to clear. This effect, accompanied by contraction of the fibrous tissue, resulted in a diminishing size of the focal lesions. None of these animals, killed at various periods up to 14 months after exposure, revealed lesions as large as those in the group killed at the end of the 20 month exposure period or those in animals which remained in the dust room for more than 20 months. Fourteen months after dust exposure ceased. 1he fori in four of the six rem aining guinea pies were so small that thov were In the group exposed for 27 months and then transferred to a normal atmosphere the response was quite similar to that in the 20 month exposure animals mentioned above. Small foci were always visible on gross inspection of sections of all guinea pigs of the 27 month series, but in no instance was there evidence of the reaction. Fig. 7.—Long fiber asbestos inhalation experiment: A , lung of a guinea pig with eight months’ dust exposure. The bronchiole at the center already shows an accumulation of phagocytic cells, and there is a slight deposition of collagen. Com­ pare with figure 6.4, showing the reaction to ball-milled asbestos after 24 months ( X 200). R, lung of a guinea pig with 16 months’ dust expbsure. Again note a bronchiole with its surrounding reaction, consisting of fibrosis and adenomatoid change. Col­ lagen deposition is now seen in the w alls of adjacent alveoli, a t the rig h t ( x 200). In the tracheobronchial lymph nodes reaction was first visible at the third month of exposure. By the eighth month patches of cellular connective tissue * l/JW* . H - ---O i O l / i L J u/i . JOULatJ i tVJJw) began to appear in the medulla, and by the fourteenth month most of the node had been replaced by cellular connective tissue. This picture, which resembled that in early silicosis,-persisted to the end of the experiment. Some animals showed, as a variant, heavy sheets of diffusely distributed monocytes and large active giapt cells, but there was never any necrosis or hyaline formation. The spindle-shaped i fh ^ w ■ £ '4 B i A Fig. 8.—Long fiber asbestos inhalation experiment: A, lung of a guinea pig with 34 months' dust exposure. A bronchiole is seen at the lower center; the large area above it represents the involvement of alveolar walls. Compare with figure 7 B and note the increased extent of reaction (X 200). B , lung of a guinea pig with 20 months’ dust exposure and then 14 months’ living in normal air. The reaction is essentially like that shown in figure 7 I t : The bronchiole at the right center is surrounded by fibrous tissue with adenomatoid change at the right. There is residual scarring in the walls of adjacent alveoli at the left. It is apparent that no progression has occurred (X 200). new cells were yellowish from fine pigment granules that stained for iron. fibers or asbostosis bodies were seen. No ¿o INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE Although asbcstosis botties were found in the lung as early as one month after exposure began, they were rare and hard to find. At five months more were visible, chiefly coiled inside giant cells, and at eight months many bodies T able 13.—Analyses of Lungs of Guinea Pigs Exposed to Dust in Inhalation Experiment with Long Fiber Asbestos Dust Exposure to Dust, Mo. 1 2 8 S 8 12 IS 20 24 27 30 34 86 20 20 20 20 27 27 27 27 Period la Norms! Air, Mo. Amt. ot Total Tissue Ash, % ot SIOs, % Of Total SIOs, Dried Lung % o t Ash Dried Lung Reaction * Dust Exposure Continuous During Lite 4.35 1.10 0.04 0,09 4.33 0 2.11 0.04 . 4.3Ì 0.93 0 0.05 4.» I 1.23 4.48 0.06 1.18 0 0.06 4.35 1.46 ± 0.06 4.38 1.20 0.05 1.13 4.38 0 ± 0.06 1.48 4.51 0.08 4.77 1.75 0.12 4.63 2.67 0 0.09 1.77 5.(18 ± 4.72 0.10 2.21 0.09 4.92 1.90 0 + 4.34 0.07 1.58 0.25 5.20 4.87 0.20 4.09 5J» 0 + 0.31 5.99 5.16 0.38 12.70 2.98 0.35 12.25 ' 2.83 0 10.91 2+ 0.34 3.16 0.43 12.22 3.54 0.49 13.63 3.60 0 0.52 14.59 2+ 3.58 0.35 10.18 3.42 0 8.29 3+ 0.29 8.52 3.40 0.39 11.51 0 13.15 3+ 0.49 3.74 10.55 0.87 3.53 0.31 11.22 3.03 0 0.24 6.10 8.88 4+ OSO 5.85 8.60 0 4+ 0.84 12.47 8.70 037 9.11 4.10 0 4+ 0.35 12.89 2.74 Dust Exposure Followed by Prolonged Residence In Normal Air 0.43 12.23 3.54 3.60 0.49 ; 13.63 0 0.52 2+ 14.59 3.58 2.92 0.21 7.23 4 231 0.27 9.60 2+ 4.18 0.24 5.78 » 4.30 0.22 5.07 Ï+ 5.01 0.21 '4.19 14 5.04 0.18 3.56 + I 0.39 3.40 11.51 Ol 3.74 0.49 13.15 8+ 1 3.5« 0.31 8.59 S 2.54 0.18 6.94 2+ 0.25 3.19 / 7.99 7 0.28 8.72 3.18 *+ 0.29 3.21 8.96 » 2.75 0.23 8.31 Í+ * The symbols averaging the tissue reaction In each group represent merely the relative degree o t reaction, ranging from o to ± (questionable) to 4+ (the maximum to r this experi­ ment). The relationships apply only within this table and cannot be compared with symbols In other tables. - I were free in connective tissue. They became fairly abundant as exposure con­ tinued, although in some later animals the asbestosis bodies were only moderately numerous. It is important to note from analyses of the lungs (table 13) that even though the tissue response at any given period of time was much greater in the guinea i VORWALD E pigs of this experiment tha: asbestos, the amount of mini Reaction in Cats.—Four 14, 25, 33 and 42 months, r cats, after being exposed to an additional 24 months, i cellular accumulations of p1 arterioles together with com; lymph nodes. A t that time pointed, yellow fibers were : months, reaction in the local nective tissue which made •> and arterioles, marked lymphs walls (fig. 9 ). Typical asl Fig. 9.—Long fiber asbesti months’ dust exposure. Two l> and collagen deposition ( X 200 an occasional fiber, smooth, yi reaction was similar in location slower in development. Roetv 25, 33 and 42 months, respecti' lesions. Reaction in Rats.—Althougl from pneumonia and were not ?• exposed for 19 months and four a n d offered a basis for tentative was ju st beginning. All four peribronchiolar fibrosis. After bodies were found in the 19 mi animal. Thus these animals exl accompanied by only a very infri VORWALD ET AL.—STUDIES OF ASBEST0S1S 27 pigs of this experiment than in those exposed to either short fiber or ball-milled asbestos, the amount of mineral matter in the lung ash was much less. Reaction in Cats.—Four cats inhaled the long fiber asbestos dust for periods of 14, 25, 33 and 42 months, respectively, and were immediately killed. Two other cats, after being exposed to dust for 18 months, lived in a normal atmosphere for an additional 24 months. Fourteen months’ exposure was sufficient to produce cellular accumulations of phagocytes around terminal bronchioles and peripheral arterioles together with compact collections of similar cells in the tracheobronchial lymph nodes. At that time there were no typical asbestosis bodies, but smooth, pointed, yellow fibers were seen very rarely. With continued exposure, up to 42 months, reaction in the locations noted progressed to the formation of cellular con­ nective tissue which made well defined sheaths about the respiratory bronchioles and arterioles, marked lymphoid hyperplasia and lymphoid infiltration of bronchiolar walls (fig. 9). Typical asbestosis bodies were not formed, although there was Fig. 9.—Long fiber asbestos inhalation experiment: Lung of a cat with 42 months’ dust exposure. Two bronchioles are shown with adjacent cellular reaction and collagen deposition (X 200). an occasional fiber, smooth, yellow and pointed. Pleurisy was not present The reaction was similar in location to that in the guinea pigs, but fibrosis was much slower in development. Roentgenograms of cats made after exposure periods of 25, 33 and 42 months, respectively, failed to demonstrate evidence of pulmonary lesions. Reaction in Rats.—Although 20 rats were placed in the dust room, many died from pneumonia and were not suitable for study. Five animals, of which one was exposed for 19 months and four for 25 months, were free from pulmonary infection and offered a basis for tentative conclusions. In the 19 month animat, the reaction was just beginning. All four animats killed at 25 months showed a well marked peribronchiolar fibrosis. After a long search, only two small, smooth asbestosis bodies were found in the 19 month animal and none was found in the 25 month animat. T h u s these animals exhibited fibrosis without asbestosis bodies'or fibrosis accompanied by only a very infrequent asbestosis body. AS INDUSTRIAL HYGIENE AND OCCUPATIONAL. MEDICINE Reaction in Mice.— O u t of 20 w hite m ice used in this experim ent, 11 lived a y ear o r m ore in du st an d died o r w ere killed w ithout show ing an appreciable degree of pulm o n ary infection. T h e reaction to the inhaled du st w as lim ited to phago­ cytosis by m ononuclear cells. U sually these w ere w idely scattered th ro u g h the a ir sp a c es; a lim ited n um ber w ere grouped about the term inal bronchioles, producing som e th ickening of th e ir w alls. T h ere was no suggestion of fibrosis. N u m ero u s asbestosis bodies w ere observed in anim als killed late in the experi­ m ent. T h u s these anim als exhibited asbestosis bodies w ithout fibrosis. S u m m ary and Interpretation oj Inhalation E xp erim en t with Long Fiber A sbestos D ust.— T he purpose of this experim ent was to evaluate the importance of long fibers in the tissue response to inhaled asbestos. T he results, in com parison w ith those of previous investigations, indicate strongly that long fibers are chiefly responsible for asbestosis. Thus, the reaction in guinea pigs developed earlier and became m ore extensive in this experim ent than in previous experim ents in spite of a smaller concentration of atmospheric dust and a lower m ineral content of the lungs. F urtherm ore, typical peribronchiolar fibrosis was produced in cats, although in a previous experim ent with short fiber dust peribron­ chiolar fibrosis did not develop in this species. T able 14.—Comparison of Peat Dosage: Each animal was given an int of the dust. Two weeks later soothe injected was 50 me. Animals used: Six groups of 0 guinea , Periods a t which animals were killed: 1 months after la s t injection. Preparation of dust: Cbrysotile (bait reground in agate m ortar. Chrysotfle (ball milled) ignited: Ball i ground in agate m ortar 2 or 3 min. t'hrysotlle (fibrous) unheated: (¡round Chrysolite (fibrous) ignited: 200-mesh i grinding. Serpentine (ball milled) unheated: Bail Serpentine (ball milled) ignited: Ball r ground in agate m ortar 2 or 3 min. Mineral Chrysotile (hall milled) unheated Size of Dust Particles 3 microns and less ph th> Chrysotile (ball milled) ignited 3 microns and less INJECTION EXPERIMENTS Chysotile 20-50 microns approx. * (fibrous) unheated eh: br( Rcai pn A diet ab< Oot spa Re» new sbi. In»; at : occt E xperiments U sing I ntratracheal T echnic A s the asbestos m inerals do not cause typical advanced fibrosis in extrapulm onary tissue, the intratracheal technic is the preferred way of introducing fibrous dust into the experimental animal. In this method the dust suspension is injected by means of a special needle o r catheter deep into the trachea, from which it flows into the lungs. Comparison o f F ibrous and N o n fibrous D usts.— T o dem onstrate that the ability of asbestos to produce fibrosis resides in its fibrous character, the series of injection experim ents reported in table 14 w ere performed. COI tioolr at T he cause of the cellular fibrosis in the lymph nodes of the guinea pigs is not clear. I t did not occur in other inhalation experim ents with asbestos. Since the inhalation experim ents reported above strongly suggested that long fibers of asbestos are the significant factor in th e causation of asbestosis, a series of injection experim ents was inaugurated wherein the dosage and the length of the fibers could be controlled m ore precisely. Also, by the use of controlled dosages, the relative capacities of various asbestos minerals to produce reaction could be com pared. In these injection experim ents, guinea pigs, rabbits, rats and dogs w ere used, and the m ineral dust was injected by the intratracheal, the intraperitoneal and the intravenous technic, b u t not all the technics w ere used for each species. F o r the purpose of simplification the findings in each series of tests, except for dogs, have been condensed and reported in tables, to which reference will be m ade later. In the case of dogs, only one test was made, and since the findings were negative, no detailed report is included. Grind Chrysolite (fibrous) Ignited 20-50 microns approx. Serpentine (ball milled) unheated 3 microns and less rear and tlor that’ tlssi react vlel: tlgftl aettAsl» well mat tort with trap curwall React I prol: brltt re a r Dust r eyto excelSligtl Serpentine (ball milled) Ignited 3 microns and less pnci Dust for ' tend T a b l e 14.—Comparison of Reactions to Chrysotile and Serpentine Injected Intratracheally Dosage: Each animal was given an intratracheal injection of 0.5 cc. of a 5 per cent suspension o t the dust. Two weeks later another similar injection was given. T o tal am ount of dust injected was 50 mg. Animals used: Six groups of 9 guinea pigs each (one group for each type of dust). Periods a t which animals were killed: One o r two animals in each group a t 1, 2, 6, 8% and 12 months a tta r la s t injection. Preparation o t dust: Chrysotile (ball milled) unheated: Ball milled for 1,176 hr., dried and reground in agate m ortar. Chrysotile (ball milled) ignited: Ball milted chrysotiie heated for 2 hr. a t ab o u t 700 C., then ground in agate m o rtar 2 or 3 min. Chrysotile (fibrous) unheated: Ground in agate m o rtar to pass 200 mesh. Chrysotile (fibrous) ignited: 200-mesh m aterial heated for 2 hr. at about 700 C. No further grinding. Serpentine (ball milled) unheated: Ball milled for 1,488 hr., dried and regronnd in agate m ortar. Serpentine (ball milled) Ignited: Ball milled serpentine heated for 2 hr. a t ab o u t 700 C., then ground in agate m ortar 2 or 3 min. Mineral Chrysotile (hall milled) unheated Si2 e o t Dust Particles 3 microns and less Chrysotile (ball milled) ignited 3 microns and less Chysotlle (fibrous) . unheated 20*50 microns approx. Chrysotile (fibrous) Ignited 20*50 microns approx. Serpentine (ball milled) unheated 3 microns and Serpentine (ball milled) ignited 3 m icrons a n d less Results Grinding destroyed capacity to cause fibrosis. At l mo. considerable inflammatory edema and cellular prolifora* tion and localization of dust particles ab o u t bronchi* oles; a t 2 mo., only a very slight proliferative reaction; at 0, S h i and 12 mo., widely scattered small mononuclear phagocytes. A t 12 mo., a lew microscopic patches of thin alveolar wall thickening with some adenomatoid change In portion of air spaces ab u ttin g on thickened bronchi. No asbestosis bodies seen. Reaction limited to large foreign body g ian t cells without production of fibrous tissue. A distinct fibrosis. Reaction localized to connective tissue about term inal bronchioles; little within those tubes. Contraction caused adenomatoid appearance o f air spaces given off directly from term inal bronchioles. Reaction area became smaller with progress o f time: no new regions involved. No chronic pleurisy even a t polots abutting intrapulm onary change. A t l mo. considerable Inflammatory edema and foci of cellular proliferation; a t 2 mo. well marked cellular proliferation and fibrosis occurring locally about respiratory bronchioles. This reaction developed before asbestosis bodies had formed and was as advanced as th a t produced by 2 yr. inhala­ tion of asbestos dust. At 6 mo., reaction less extensive than a t 2 mo., apparently due to contraction of fibrous tissue; asbestosis bodies were abundant. A t 8% mo., reaction still less extensive, confined to the immediate vicinity o f the small terminal bronchioles, where the scar tissue was quite dense and was becoming hyaline Id char* actcr. Sometimes it even obliterated th e bronchiole. Asbestosis bodies had become scarce. A t 12 mo., the well developed peribronchial and intrabronchlal adenoi m atoid areas of fibrosis had produced considerable dis­ tortion. More peripherally were patches of pneumonitis with eosinophilic Infiltration, some of which was being transform ed into fibrous tissue. These seemed to be pre­ cursors of the localized, diffuse patches o t thin alveolar wall fibrosis seen elsewhere. Reaction limited to large foreign body g ian t cells without proliferation. H eating the fibers, which made them brittle, destroyed their capacity to produce significant reaction. Dust relatively Inactive. At 1 and 2 mo., simple phago­ cytosis w ithout proliferation; a t G mo., no change except possibly lymphoid cell Infiltration; a t 8% mo., a slight chronic pneumonitis: a t 12 mo., only a little pneumonitis w ithout suggestion of fibrosis. Dust relatively Inactive. Reaction essentially the same as for unheated serpentine. With ignited serpentine, less tendency fo r d u st to be carried to bronchial nodes. òU INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE I VORWALD E The tests were made \ chrysotile that had been milled to reduce the lenj. time control tests wen chemical composition as findings reveals that on) typical peribronchiolar l only fibers less than 3 i 10 and 11). Fibers su to cause serious tissue • in the chrysotile fibers, from a flexible to a brittl is shown at the left center the bronchiole and collagen ■ mental studies concernim> publication. Comparison o f Vario t F*K- 10.—Comparison of reactions provoked by injected long fiber and ballmilled asbestos dusts: A , lung of a guinea pig which four months before had received an intratracheal injection of long fiber asbestos dust. Note the peri­ bronchiolar accumulation of cells with collagen deposition. The bronchiole chiefly involved is in the midst of the reaction ( x 200). , . B,\ung of a guinea pig which four months before had received an intratracheal injection of ball-milled asbestos dust A bronchiole is shown at the right. In contrast with A, note that only a few cells have accumulated about the bronchiole and that collagen deposition is absent ( x 200). it i findings are disclosed by 15. First, all the long fil of anthophyllite, prodw broncliiolar reaction can minerals—chrysotile, anv and 12. Why anthophyl minerals is not entirely < Second, with the mi fibrous form of magne VORWALD E T AL.—StVD i'E S OF ASBESTOSIS 31 T h e te s ts w e re m a d e w ith lo n g fib er c h ry s o tile , u n h e a te d , a n d w ith c h ry so tile th a t h a d b e en ig n ite d to d e s tro y i ts flex ib le s tr u c tu r e o r ball m illed to re d u c e th e le n g th of fib er to 3 m ic ro n s a n d less. A t th e s a m e tim e c o n tro l te s ts w e re m a d e w ith se rp e n tin e , w h ich h a s th e sam e ch em ical co m p o sitio n a s c h ry s o tile b u t is n o n fib ro u s. A re v ie w o f th e fin d in g s re v ea ls th a t o n ly th e u n h e a te d , lo n g fib er c h ry s o tile p ro d u c e d ty p ic a l p e rib ro n c h io la r fib ro sis a n d th a t b a ll-m ille d m a te ria l c o n ta in in g o n ly fib ers less th a n 3 m ic ro n s in le n g th fa ile d to c a u s e fib ro sis (fig s. 1 0 a n d 1 1 ). F ib e rs s u b je c te d to ig n itio n a ls o h a d lo st th e ir c a p a city to cau se se rio u s tis su e d a m a g e. Ig n itio n p r o d u c e d im p o r ta n t c h a n g e s in th e c h ry so tile fibers, a m o n g th e m b e in g lo ss of w a te r, a n a lte ra tio n fro m a flexible to a b rittle s t r u c tu r e a n d p o ssib ly o th e r c h a n g e s. E x p e ri­ m e n ta l stu d ies c o n ce rn in g th is o b s e rv a tio n w ill b e r e p o rte d in a s e p a ra te p u b licatio n . Comparison of Various Long Fiber Dusts .— S o m e v e ry in te re s tin g fin d in g s a re disclosed by th e r e s u lts o f th e e x p e r im e n ts re c o rd e d in tab le 15. F ir s t, all th e long fib er a s b e s to s m in e ra ls te s te d , w ith th e ex ce p tio n o f an th o p h y llite , p ro d u c e d ty p ic a l fib ro sis. The c h a ra c te ris tic p e r i­ b ro n c h io la r re ac tio n c au sed b y th r e e re p re s e n ta tiv e lo n g fib e r a sb e sto s m in e ra ls— ch rysotile, am o site a n d c ro c id o lite — is s h o w n in fig u re s 10 A a n d 12. W h y a n th o p h y llite b e h a v e d d iffe re n tly fro m th e o th e r a sb e sto s m in e ra ls is n o t e n tire ly c le ar. S eco n d , w ith th e m in e ra l b ru c ite , w h ic h is n o t a silic a te b u t is a fib ro u s fo rm of m ag n e siu m h y d r o x id e , a c h a r a c te ris tic fib ro sis like ««/ K'ifò Lo tu j liü c r D u sts i n j e c t e d Intratrachcady VORWALD ET D osage: Two injections of 0 3 cc. o f a 5 per cent suspension given tw o weeks a p a rt. T o ta l dose w as 50 mg. Animals used: From 6 to 9 guinea pigs fo r each d u st. P eriods a t which anim als were killed: Usually a t 1, 4, 8 aod 12 m onths a fte r la s t injection. Size o f d u st particles: S eparated so th a t m ost fibers were from 20 to 50 microns long. Mineral O hrysotile (T h etlo rd ) ChrysotUe (Arizona: lowiron eon ten t, 0.2% FesOa) Amoelte CrocldoUte (Bolivia) Oroeidolite (8. A frica) A nthophylllte Trem olile Bruche Glass wool Results D istinct fibrosis. A dditional in fo rm atio n given opposite cbrysotlle (fibrous) unheated, in table 14. Reaction v irtually identical w ith th a t to T hetford ohrysotile. Both fibrosis aud asbestosis lu>dics produced w ith an asto sto s containing very little iron. Fibrosis occurred as plugs w ithin term inal bronchioles and as finer deposits a t periphery. Fibrosis developed before asbestosis bodies were seen and was in cellular sta te well formed u t one m onth. W ith age. fibrous tissue contracted and occupied smaller area b u t was more dense. Adenomatoid changes sim ilar to those with T hetford ehrysotlle. Pleurisy limited to Iminedlutc vicinity of early reaction ab o u t areas of massive localization. Asbestosis bodies formed but were few. A t 1 mo. after injection, m inute foci of m ononuclear proliferation ab o u t bronchioles and in areas of atelectasis: a t 1% mo., heavy peribronchiolar patches of fibrosis often with papillary projections partially closing lumen of bronchiole; adenom atoid appearance m arked; connective tissue reaction showed heavy collagen but n o hyaiinizution: a t 2 mo., m inute foci of well m atured fibrosis ab o u t bronchioles;' a t 6 m o., m ature asbestosis fibrosis w ith evidence of co n tractio n ; considerable chronic pneumonitis w ith infiltration o f lym phocytes and eosinophils. A t 9 mo., sm all intrabronchiolar fibrous plugs w ith foci o f more delicate fibrosis a t periphery. Typical fibrous endobronohlolitls and peribronchiolitis w ith form ation of atypical asbestosis bodies. H a u stra tio n of bodies began before 4th mo. a fte r injection, well developed by sth mo. Bodies persist afte r 12th mo. Reaction a t i mo. heavy endobronchlolitls and peribronchiolitis already showing fibrous changes; atelectasis and fibrosis w ith some necrosis at site of massive localization of dust. At 4 mo., heavy, widely scattered endobronehiolitts and peribronchiolitis, now fibrous, w ith m arked defor­ m ity of bronchioles and with an adenom atoid appearance. At 8 and 10% mo., reaction in lung essentially the same as a t 4 mo. A t 12 mo., foci of fibrous endobronchiolttis and peribronchiolitis still large, w ith m ore dense sear tissue and m ore deform ity o f bronchial tubes b u t no extension into, o r atelectasis of, peripheral parenchym a. ^ Advanced fibrous endobronchlolitls and peribronchiolitis. Beaded asbes­ tosis bodies noted a t 8 mo. A t 1 m o., early fibrous endobronchiolitig and peribronchiolitis: m ao y g ia n t cells and some lymphocytic reaction. A t 4 m o., small are as o f endohronchiolitis scattered th ro u g h o u t the lung: cellular fibrosis. At 8 and 12 mo., areas of bronchiolitis sm aller bceause of cootraetion o f dense scar tissue; a t 12 mo., m arked lymphocytic infil­ tratio n and adenom atoid appearnnee. Typical advanced fibrous endohronchiolitis and peribronchiolitis produced by 0.5% suspension (1 ce. to ta l dose); m ost anim als would n o t tolerate usual 5% suspension. Fibrosis well developed before asbestosis bodies seen. At 4 mo., well developed fibrous bronchiolitis w ith lymphocytes and g ia n t cells and adenom atoid change. A t $ mo., typical bronchiolitis n o t quite as extensive o r a s heavily fibrous as with a 5% suspension, other­ wise the same. Many deeply stained fitters with a good proportion of h au stra te d asbestosis bodies. At 12 mo., heavy fibrous bronchiolitis, m ore peribronchiolitis an d endobronchlolitls, w ith lym phocytes and g ia n t cells: very m arked adenom atoid appearance. Lymphocytic Infiltration and g ia n t cells b u t no fibrosis. A very few atypical asbestosis bodies. A t X m o., m any scattered foci o f intrabronchiolar d u st w ithout m assive localization; lymphocytic infiltration of walls and a few g ia n t cells. A t 8 an d 12 m o., little evidence o f d u st: a few bronchioles and bronchi w ith g ia n t cells in ad jac en t alveoli and w ith lymphocytic infiltration o f walls. Fibrosis ab o u t bronchioles. A t 1 mo., areas of d u st localization with col­ lapse o f alveoli and infiltration w ith a ru te Inflam m atory cells, m acro­ phages and g ia n t cells. W ithin th e area were a few foci o f fibrous tissue and numerous areas o f h y pertrophy o f alveolar epithelium. Many bron­ chioles packed w ith fibers. A t 4 m o., general appearance of lesion unchanged: pleura slightly thickened over heavy localizations of dust. An occasional segmented asbestosis body seen. At s mo., m any foci of fibers in bronchioles and alveolar duets with cellular reaction as before: also, soim* foci showed d istin ct collagen deposition. At 12 and 18 mo., reaction a s before w ith fibrosis ab o u t bronchioles more ap p aren t because of con­ traction and decrease o f inflam m ation. Giant cells prominent. Fleura m arkedly involved. . Typical fibrous eodobronehtolitts and peribronchiolitis like reaction to asbestos m inerals. A t 1 m o., extensive endohronehloMtl* and peribron­ chiolitis w ith g ia n t cells: dense fibrous loops within bronchioles and cellu­ la r fibrosis ab o u t them : adenom atoid change present. A t 2 mo., heavy intrabronchiolar and peribronchiolar fibrosis producing m arked deform ity w ith distortion o f tubes and obliteration o f surrounding air spaces: fibrosis pale w ithout hyalinisation b u t with few nuclei: no necrosis. Typi­ cal asbestosis bodies seen. A t 4 and a mo.. Ht tie change; fibrous tissue contracting. At 10% m o., dense fibrous bronchiolitis with asbestosis bodies. Ko pleurisy. Ko extension to surrounding lung. Ko fibrosis w ithin a year. A t 1 m o., n o reaction Inside bronchioles; in peripheral a ir spaces clumps o f g ia n t cells pocked with fine spicules of glass w ith lym phocytic infiltration of adjacent walls: no asbestosis bodies. At 2 mo., reaction less Intense th a n a t l m o.: fair-sized clump« of »don .• that produced by the asbesto the brucite used contained o obvious that a siliceous coi development of asbestosis. \ H g . 12.— A m o site and crocido’ p ig four m ouths a fter an intratr; reaction ex h ib its pronounced accun B , lu n g o f a gu in ea p ig four m lite- A s in A , p eribronchiolar a c c show n ( X 2 0 0 ). Third, no fibrosis resulte< (fig. 13 B ) t even though glas 4• « VORWALD ET AL.—STUDIES OF ASBEST0S1S 33 that produced by the asbestos minerals was obtained (fig. 13 A ). Since the brucite used contained only 0.90 per cent silica as an impurity, it is obvious that a siliceous component is not an essential factor in the development of asbestosis. F ig . 12.—Am ositc and crocidolite injection ex p erim ents: A, lung of a guinea pig four m onths after an in tratrach eal injection of amosite. T he inflam matory reaction exhibits pronounced accum ulation of cells and collagen deposition ( X 200). B, lung o f a guinea pig fo u r m onths a fte r an in tratrach eal injection of crocido­ lite. A s in A, peribronchiolar accum ulation of cells and deposition of collagen are show n ( X 200). Third, no fibrosis resulted from the injection of glass wool fibers (fig. 13 B), even though glass wool resembles asbestos in many ways. J-* VU U Ò I K I A L H H jlh i\E AND OCCUPATIONAL MEDICINE VORWALD ET in diameter is a solid rod which in short lengths is fairly rigid, while an asbestos fiber of the same diameter is a bundle of extremely fine filaments which impart to the fiber a high degree of flexibility. It would seem that this structure and the associated flexibility are important factors governing the capacity of a mineral to produce peribronchiolar fibrosis. Experimental si reported in a separate public T a b l e 16.—Comparison of /?. Dusii Dosage: Two Injections ot O.S ce. • dose was SO mg. Animals used: Six groups ot gutnei Periods at wblcb animals were itlllei Mineral Chrysottle (Thetford) Amoslte Size of Dust Particles Long fiber, 20-50 microns Short fiber, 3 microns and less Long fiber, 20-50 microns Short fiber, 20 microns and less Crocidollte (Bolivia) Long fiber, 20-50 microns Short fiber, 20microns and less AntbopbyDIte Long fiber, 20-50 microns Short fiber, 3 microns and less Tremollte Long fiber, 20-50 microns Short fiber, 20microns and less Brucite Long fiber, 1 20-50 microns Short fiber I (made by crushing long fibers with rubber police­ man) \ F fo 13.—Brucite and glass wool injection experiments: A , lung of a guinea pig which four months before had received an intratracheal injection of brucite. Even with this nonsiliceous fibrous mineral there is peribronchiolar accumulation of cells and deposition of collagen similar to that shown in A and B of figure 12 ( X 200). _B, lung of a guinea pig which four months before had received an intratracheal injection of glass wool. Two bronchioles are shown, one in cross section and the other in longitudinal section. Below the latter is a thick-walled blood vessel. The bronchioles are without reaction and can be considered normal for comparison with other figures. Glass wool fibers are present in this field but cannot be seen at this magnification (X 200). \ Compari.inn of T ono Fib VORWALD ET AL.—STUDIES OF ASBESTOSIS 35 fibrosis! Experimental studies concerning this observation will be reported in a separate publication. T a b l e 16.—Comparison of Reactions Produced by Long F iber and S h ort Fiber D u sts Injected Intratracheally Dosage: Two injections of 0.6 cc. o f a 6 per cent suspension given tw o weeks ap a rt. T otal dose was 50 mg. Animals used: Six groups of guinea pigs. Periods a t which animals were killed: 1 , 2, 6, 8% and 12 m onths afte r injection. Mineral Uhrysotile (Thetford) AroosJte Size of D ust Particles L ong fiber, 20*50 microns Short fiber, 3 microns and less L ong fiber, 20-50 microns S hort fiber, 20 microns and less Crocidolite (Bolivia) Long fiber, 20-50 microns S hort fiber, 20 microns and less Anthopbyllite Long fiber, 20-50 microns S hort fiber, 3 microns and less V Tremoli te Brucite \ L ong fiber, 20-50 microns S hort fiber, 20 microns and less Long fiber, 20-50 microns S hort fiber (m ade by crashing long fibers with rubber police­ m an) Results A distinct fibrosis. Refer to chrysotUe (fibrous) un­ heated in table 14. No fibrosis. Refer to ebrysotile (ball milled) unheated in table 14. Typical fibrous endobronebiolitis and peribronchiolitis. Refer to table 15. Reaction limited to phagocytosis with lymphocytic infil­ tratio n of adjacent walls. S h o rt fibers packed inside swollen phagocytes: longer ones free; some coated to form typical asbestosis bodies. A t 1 mo. after Injec­ tion, alveoli contained good-sized g ia n t cells, m ost phagocytes were within air spaces and had n o t m igrated to walls. At 4 mo., free extracellular fibers had worked themselves into interstitial tissue, where there was extensive proliferation of lymphoid cells and monocytes b ut no fibrosis. A t 8 mo. foreign body reaction with some pneumonitis, no bronchiolitis. Typical asbestosis bodies present. Advanced fibrous endobronebiolitis and peribronchio­ litis. Refer to table 15. No fibrosis. At l mo., air spaces compressed and largely filled with g ian t cells packed with d u st needles. Walls heavily Infiltrated with monocytes and lymph­ oid cells. A t 4 mo., a m oderate degree o f cellular infiltration of walls; small g ia n t cells packed with dust spicules. A t 6 an d 8 % m o., masses o f g ian t cells, containing mineral particles, in sm all bronchi b u t n o t in respiratory bronchioles; sm aller ones widely scat­ tered In terminal air spaces. Numerous asbestosis bodies. No reaction to connective tissue. No endo­ bronchial proliferation. A t 12 m o., m any scattered small monocytes packed w ith d u st. No endobronchitls. No peripheral fibrosis. In lym ph node, slight reticulosis; no fibrosis. Lymphocytic infiltration and g ia n t cells b u t no definite fibrosis. Refer to table 15. No fibrosis and practically no asbestosis bodies. A t 1 mo., focal collections of dust-filled monocytes and a few giant cells; a t 4 mo., some adenom atoid epithelial reaction; a t 8 mo., simple pneum onitis with phago­ cytosis of short fibers; a t 12 mo., isolated and sharply localized collections o f d u st cells Inside a ir spaces about term inal arterioles. Reaction in walls limited to lymphoid cell infiltration. No fibrosis. In lymph node, reaction limited to slight prominence o f reticu -: lum. Fibrosis about bronchioles. Refer to tab le 15. Simple foreign body reaction. No acute Inflammation. No accumulation of d u st In o r ab o u t term inal bron­ chioles. No eodobronchitls. A t 1 m o., scattered small giant cells and considerable infiltration o f adjacent wans with monocytes and lymphoid cells. A t 4 mo., little change except more cellular Infiltration o f con­ nective tissue. At 8 mo., lymphoid Infiltration and thickening of walls about some b u t n o t all term inal bronchioles. Typical fibrous endobronebiolitis an d peribronchiolitis like reaction to asbestos minerals. Refer to table 15. In ert type of reaction. A t 1 mo. a fte r injection, small monocytes widely scattered through a ir spaces; focus of atelectasis with lymphoid Infiltration o f compressed air-space walls. No endobronchial reaction a s with chrysotUe. At 2 mo., reaction sim ilar to th a t a t l mo.; typical asbestosis bodies seen. A t 12 m o., small clumps of loactive dust-filled phagocytes; no fibrosis. No reaction in lymph nodes. C o m p a ris o n o f J.nnn F ih rr m id S h o r t F ib e r D v s f x — W i t l i nnort-r intense is the tissue reaction and that particles larger than 3 microns in diameter cause little reaction. In the case of asbestos, however, the reverse is true and apparently only long fibers have any specific effect, as was suggested by the inhalation experiments. This is confirmed by the data of table 16, in which a series of tests with fibrous minerals is reported. When the injected dust consisted of fibers 20 to 50 microns long, all the fibrous minerals tested except anthophyllite, as noted in the preceding section, produced fibrosis; when the material was prepared by first grinding the fibrous dust until the length of fibers was reduced to 20 microns and less or, in some cases, to 3 microns and less, none of the injected dusts caused fibrosis. These results differ from those of King, Clegg and Rae,u who reported the production of reticulosis comparable to the experimental silicotic nodule in rabbits receiving monthly intratracheal injections of 100 mg. of Rhodesian asbestos fibers, 15 microns long, and the produc­ tion of diffuse interstitial fibrosis in rabbits receiving similar injections of short fibers, 2.5 microns in length. We believe this dose, especially in the long term rabbits, is highly excessive. In our experiments the dosage was kept low in order to minimize untoward reactions which might obscure the peribronchiolar type of fibrosis which characterizes early human asbestosis. E xperiments U sing I ntravenous T echnic The experiments summarized in table 17, in which the intravenous method of injection was employed, show that the asbestos minerals are far different from quartz in their action on tissue. It has been repeatedly demonstrated that intravenous injection of quartz particles 3 microns and less in diameter will cause a typical tissue reaction with the development of hyalinized fibrotic lesions in extrapulmonary sites, such as the liver and the spleen. Asbestos minerals, however, on intravenous injection generally produce only an inert type of reaction, as is revealed by the results given in the table. The reason for the early deaths in the experiment with chrysotile particles is not clear. E xperiments U sing I ntraperitoneal T echnic The results of injection experiments with the intraperitoneal technic are given in table 18. It will be noted that the long fiber dusts produced a fibrous reaction while dusts composed of particles 3 microns and less in size caused only an inert type of response. These experiments indi­ cate also that the fibrosis initiated by the irritation of asbestos fibers is not restricted to the lungs, as was formerly assumed, but can be pro­ duced in the peritoneum as well. OTHER EXPERIMENTS W ITH ASBESTOS MINERALS A number of additional experiments were conducted to throw more lig h t on specific phases of the asbestosis problem . 1 11. King, E. J . ; Clegg, J. W., amt Rae, V. M.: Effect of Asbestos, and of -I.,,! M',m i n i m i mi T i i ‘ i<> I*-.U .it,- Tin ,r*i i- 1 »1eQ mil- . .,1 ....... T able 17.—Summary of Injection Experiments by Intravenous Technic 36 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE T able 17.—Summary of Injection Experiments by Intravenous Technic D osage: T o ta l am o u n t o f d u s t w as 1.0 Gm., divided in to 20 equal doses (each dose w as 5 cc. o t a 1 per cent suspension) which were given twice a week fo r 10 weeks. Maximum Survival After L ast Injection, Mo. Size of Dust P articles 3 microns and less (hall milled 132 hr.) R abbits Used 6 Amosite 3 microns a n d less (g ro u n d In a g a te m o rta r) & 17 Crocidoltte 3 microns an d less (g round in a g a te m o r ta r) 4 72 Anthophyllfte 3 m icrons an d less (hall milled 1,400 hr.) 4 24 T rem ollte (soda-iron) 3 microns an d less (hail milled 140 hr.) 3 microns an d loss (hall milled 4$ hr.) 4 19 4 24 Mineral Chrysotfle (T hetford) Trem olite (soda) Results The ra b b its did n o t to le ra te Intravenous injections o l finely ground chrysotlle an d 5 o f the 3 died a fte r 1 to 5 injections o f even diluted suspensions; th e o th e r anim al died a fte r 27 injections o f one* q u a rte r stre n g th suspension (GO d a y s a fte r first in jection). Reaction lim ited to few la rg e g ia n t p h ag o ­ cytes o f inactive type in liver, spleen a n d lungs. No throm bi o f d u st cells seen in pu lm o o ary capil­ laries. No definite ex p lan atio n lo r fa ta litie s discovered, b u t m aterial m a y h av e been reta in ed in h e a rt, causing local th ro m b i. .Advanced pu lm o n ary infection killed 3 an im als a t 9, 11 an d 17 m o. a f te r la s t in jectio n , sho rten in g Intended d u ra tio n o t experim ent an d com plicating picture. However, r a b b its killed earlier (3 and 3 m o.) showed only Inert phagocytosis w ith n o progression in th e 6 mo. an im al. T h e la s t tw o (11 an d 17 m o.) were p ro b ab ly th e sam e alth o u g h lo c al necrosis of th e liver an d am yloid o f th e spleen made In terp reta tio n difficult. R eaction w as th a t to a n in ert substance w ith n o change In 12 m o. (O ther o b serv atio n s a t 3, 4 an d 3 m o.) Simple phag o cy to sis o f particles. No tendency to agglom erate an d n o change In ad jac en t tissues. G rinding th e d u s t to sizes o f 3 m icrons an d under destroyed th e fibrous stru c tu re o f th is m ineral, an d th e injected m a teria l resembled p lates ra th e r th a n fibers. R eaction essentially t h a t o f an in e rt m ineral. O bservations m ade a t 3, 6, 12 an d 24 m o . Only sugges­ tio n o f irrita tin g p ro p erties m anifested in spleen an d lym ph nodes, b u t n o t liver, of th e 24 m o. ra b b it. I n th is an im al th e re h a d been p ro liferatio n o f m ononuclear an d g ia n t cells th a t w as n o t p resen t in eith er spleen o r lym ph node o f 12 m o. anim al. T he absence o f associated fibroblastic reaction in these o rg a n s an d o f an y change in th e liver condition justifies th e classification o f an th o p h y lllte a s a n in e rt silicate. No fibers were retain ed In lu n g to d e m o n stra te w hether asbestosis bodies would develop. Reaction essentially th a t o f an Inert m ineral. L ast anim al killed showed a little p ro liferatio n an d lym phocytic in filtratio n in liver, n o t seen earlier ( a t 3, 3 and 12 m o.). No evidence o f an y a c tiv ity in lesions in o th e r o rg an s. An in ert foreign body reactio n w ith n o change in 24 m o. O bservations m ade a t 3, 0, 12 and 24 mo. T a b l e 18.—Sum m ary o f In jection E xperim ents b y Intraperitoneal Technic Dosage: Each anim al# received a single Intraperitoneal Injection o f 2 cc. o f a 10 per cent dust suspension. T otal am ount o f du st Injected was 0.3 Gm. Maximum Survival A lter Size of Guinea Pigs Injection, Mineral Dust Particles Used Mo. Results 36 No fibrosis o r asbestosls bodies. D ust particles ingested by phagocytes, chiefly multlnudeated ChrysotUe 8 microns and less 16 variety. Six mo. alter injection fibrous elements of d u st appear to have dissolved leaving only (Thetford) (ball milled the Insoluble magnetite, a contaminant. No reaction in surrounding 1st o r areolar tissue. No 216 hr.) -----transporting o l dust to regional lymph nodes. Observations made a t Intervals from 1 to 36 mo. a lte r injection. Cbrysotile Long fiber 4 2 Definite fibrous reaction produced, delicate and nonhyaline. Atypical asbestosls bodies developed, (Thetford) (through lOOmesb) b u t all were unusually small. No evidence o l ex tra long fibers seen. Observations only a t 2 mo. Amosite 0 3 microns and less 12 Inlection interfered with interpretation. Dust reaction appeared to be o l inert type and limited to (ground in agate phagocytosis with a moderate tendency to lymphocytic Infiltration. Observations a t 1, 4, 8 and mortar) 12 mo. Crocidolite 3 microns and less; 7 12 Dust loci consisted only ol large mononuclear and giant phagocytes surrounded by a minimum also some long am ount o l cellular connective tissue. The injected d u st contained n o t only fine material th a t spicules (ground in grinding had been mashed Into irregular plates but also many long spicules io microns o r more in agate m ortar) In length. No asbestosls bodies seen, although the longer spicules appeared slightly swollen and greenish. Observations a t 1, 4, 8 and 12 mo. Anthophyllite 3 microns and less 5 25 Essentially inert loreign body reaction. In early animals (1, 4 and 8 mo.) locus of monocytes and (ball milled small giant cells and a little central necrosis. In th e 4 mo. animal there was also slight peripheral 1,400 hr.) fibrosis. A t 12 and 25 mo., nonprogressive mass o l monocytes and giant cells; no fibrosis. Mostly 3 microns Anthophyllite 5 12 Reaction, which consisted ol very large giant cells surrounded by a variable number o l lympho­ (originally and less; some cytes, was much heavier to these unintentionally long fibers th an to the fine du st in the experiment labeled talc) fibers 30 microns above. There was more or less proliferation of fibroblasts producing cellular connective tissue or more long visible in areas where the quantity of loreign particles was n o t so great th a t i t obscured the (ground in agate reaction. Observations a t 1, 4, $ and 12 mo. mortar) Tremolite 3 microns and less 5 12 Inert type of response never progressing beyond the stage o f very slight lymphocytic reaction about (soda-iron) (ball milled masses o l dust-filled phagocytes. No fibrosis. Observations a t l, 4, S and 12 mo. 15 hr.) 6 Tremolite 3 microns and less 18 In ert nonprogressive foreign body type o f reaction. No fibrosis. Observations a t 1, 4, 8, 12 and (soda) (ball milled 18 mo. 48 hr.) 6 100 microns and Anthophyllite 12 Distinct early fibrosis produced by anthophyllite and fibrous pyrophyllite with subsequent regres­ less sion; crystalline pyrophyllite inert throughout. A t 1 mo., g ian t cells about long thick splinters; 6 100 microns and Pyrophyllite 12 a t 4 mo., definite fibrosis replacing giant cells o f anthophyllite and fibrous pyrophyllite reaction; (fibrous) less a t 8 mo., fibrosis which started a t 4 mo. had decreased, especially with fibrous pyrophyllite. A t 6 100 microns and Pyrophyllite 12 12 mo., reaction to all three dusts consisted of foreign body giant cells with lymphocytes b u t leu (crystalline) w ithout necrosis o r fibrosis. No asbestosls bodies. * Each animal receiving long fiber chrysottle was given an injection '1 2 ce. of a 0.5 per cent dust suspension. < CL S.SS 1A i : fP CL > * 3 P £ CL 2 n «° a CL 0 *3 a> X p 11 8 ? irt> H a> as <^ n o o r ? o 5* £ § . 3 *0 "V (/» o> I 8 .8 S J-. 3 3* 3* ~ c ST P r* § f 30 . it3* ^ ST ** OfQ ÏV S g t * i-H 3 n * 5 ffw £1 8vo I9 » 1 P ^ 2S3. C ST ceO P St o * s g *- P < S * g .» g lJ CO cr a < ^ g f 3* R £? 3 2 . g R s * w Z n* 2 . cr £ 2 . | f 3* e g P cr 3 c r 3 •—* op 0fQ ° co « M W <> j r £ . w ? 3 R . i f » O r* 2 . 3* P c r «-► Z 3 £• g «T it n 8« p ? I o 3 *-1 a 3 ? 8 cco 3 3* it O S i< ^ —. o H ■S. 2 ? g*I §• 3 *D Si "3 • 3 3 3* S. 3 a __ cr n> -i p n i3 . fco 0 O 3. i = 5 ?T £ n *o O o 3 (o ^ 3* E —s P rotective A c *■? 3 * 53 3 105 O. Total % % 0.66 0.32 0.27 0.53 4« 0.02 0.34 % 5.28 3.60 4.08 26.« 14.99 2« 2.78 asbestos fibers into the peritoneum, where there is also a degree of mobility, but not by injecting them into other extrapulmonary organs such as the liver, the spleen and subcutaneous tissue. COMPLICATIONS The experimental investigations with asbestos minerals were con­ cerned primarily with the effect of the dust on normal tissue, but some attention was given to other phases, such as susceptibility to infection. The only experiment in which the effect of asbestos dust on a pulmonary infection was studied was the first inhalation experiment, carried on with King’s floats dust. It is unfortunate that, owing to the lack of adequate facilities at that time, infection studies could not be made in the other inhalation experiments also. S usceptibility to T uberculous I nfection t The development of a tuberculous process initiated at the beginning of exposure to dust, and also of a tuberculous infection superimposed on an established asbestosis, was described in preceding sections of this paper. It may be stated that asbestos when classified according to the effect of a dust on tuberculous infection would be placed below an active 99.97 99.77 99.52 99.7? 99.89 99.03 99.82< There was no sp< asbestos dust on nont rather common amon in guinea pigs expose 16 to 39 per cent. 1 an effect of asbestos since such epidemics : other dusts and even inhalation of asbestos susceptibility to nontu Owing to the vast seems most convenient the various observatio follow each with a brii A. Various species of rabbit, but not tlfibrosis of the lun by inhalation or ii. fibers. Both inhalation an for this statement. Fi in guinea pigs followin the fibrosis caused in . Similar but less extet (table 1). Mice and d of different species to i B. Long asbestos fiber chiolar fibrosis; slv t VORWALD ET A L . S T U D I E S OF ASBESTOSIS 41 dust like quartz but above an inert dust such as iron oxide. In animals infected with attenuated tubercle bacilli, quartz causes the infectious process to progress until the animal dies of tuberculosis. Inert dusts have no effect on the infection, and the lesions usually heal and the disease disappears. Asbestos dust is in a different category. In the experimental investigation, when the fibrous dust was being inhaled dur­ ing the evolution of the infection, there was spreading of the tuberculous process for a time, but usually the stimulus for continued proliferation of the tubercle bacilli was not sustained, the progression was arrested and healing followed. In guinea pigs infected with attenuated tubercle bacilli after being exposed to asbestos dust for slightly more than two years, progressive disease did not develop. The only modification of the infection was one of localization, a few bacilli being retained in the fibrous terminal bronchioles and forming tubercles there, in addition to the usual foci beneath the pleura. Such tubercles healed in a few months. S usceptibility to N ontcberculous I nfection There was no specific experiment concerning the effect of inhaled asbestos dust on nontuberculous infection. Intercurrent pneumonia was rather common among animals exposed to asbestos dust, the frequency in guinea pigs exposed in the four inhalation experiments ranging from 16 to 39 per cent. This incidental evidence suggests the possibility of an effect of asbestos dust on nontuberculous infection. Nevertheless, since such epidemics are not uncommon in inhalation experiments with other dusts and even in the colony of normal animals, it is felt that the inhalation of asbestos dust does not exert a significant effect on the susceptibility to nontuberculous pulmonary infection. COMMENT AND SUMMARY Owing to the vast amount of data included in this investigation, it seems most convenient to summarize and to state as concisely as possible the various observations which emerged from the experiments and to follow each with a brief resume of the evidence. A. Various species of animals, including the guinea pig, the rat and the rabbit, but not the mouse and the dog, develop peribronchiolar fibrosis of the lung similar to human asbestosis after being exposed by inhalation or intratracheal injection to long chrysotile asbestos fibers. Both inhalation and injection experiments provide ample support for this statement. Figure 8 A reveals the cellular fibrosis that occurs in guinea pigs following inhalation of long fiber asbestos; figure 9 shows the fibrosis caused in the cat by inhalation of long fiber asbestos dust. Similar but less extensive fibrosis occurred also in rats and rabbits (table 1). Mice and dogs failed to respond. This variation in response of different species to identical dust exposures is still to be accounted for. B. Long asbestos fibers are essential in the production of the peribron­ chiolar fibrosis; short fibers are incapable of producing this reaction. 42 IN D U S T R IA L H Y G IE N E A N D O C C U PA TIO N AL M E D IC IN E Inhalation experiments with asbestos dust suggest, and intra­ tracheal injection experiments confirm, that peribronchiolar fibrosis is produced by asbestos fibers between 20 and 50 microns in length but not by particles shorter than 20 microns (tables 16 and 18). This indicates that the minimum length of fiber possessing the capacity to produce the typical peribronchiolar fibrosis in animals is somewhere between 20 and 50 microns. Pointed studies have not been carried out to determine the upper limit of effective fiber length. I t appears, however, that that limit will be determined by the inhalability of the fiber. C. The mode of action of the long asbestos fiber in the production of asbestosis is primarily mechanical rather than chemical in nature. The evidence for this conclusion has been reviewed in a preceding section, page 39. The flexible filamented structure of asbestos fibers plays an essential part in the irritating action, since the solid, inflexible fibers of glass wool do not produce fibrosis (fig. 13 B ) . D. Typical experimental asbestosis was produced by the inhalation of an atmospheric suspension containing an average of 138 million asbestos particles per cubic foot of air by light field count, of which less than 1 per cent consisted of fibers longer than 10 microns. In the inhalation experiment with 100 per cent ball-milled asbestos dust containing 0.6 per cent of fibers longer than 10 microns (table 11) typical fibrosis was obtained (table 9). The evidence presented shows at least that an atmospheric concentration of asbestos dust containing less than 1 million (0.6 per cent X 138 million) fibers longer than 10 microns p<-r cubic foot of air is capable of producing experimental asbestosis in guinea pigs. The actual lower limit of concentration of long fibers necessary to produce asbestosis in animals cannot be estab­ lished from these studies. E. The duration of exposure required to develop the pulmonary reaction to inhaled asbestos dust is inversely proportional to the concentration of long fibers in the atmosphere; as the concentration is increased, . the reaction develops in shorter time. The basis for this statement appears in the data of the inhalation experiment with long fiber asbestos. For that experiment the average concentration of the atmospheric dust was about 40 million particles per cubic foot of air, and size-frequency determinations disclosed that 6.7 per cent of the air-suspended material consisted of fibers longer than 10 microns (table 11). Thus, by calculation, it is estimated that the con­ centration of the longer fibers was 2.7 million (6.7 per cent X 40 mil­ lion). The lungs of animals exposed to the long fiber asbestos dust revealed that the pulmonary reaction developed in approximately onehalf the exposure time required for its development in animals inhaling the ball-milled product, for which the concentration of the longer fibers was only 0.8 million (0.6 per cent X 138 million). F. Established experimental asbestosis ceases to progress on discon­ tinuance of dust exposure. The experimental investigation shows, in fact, that on discontinuance of exposure there was an appreciable clearing of the mature nulmnnnrv VORW ALD ET lesions, due to contraction ture tissue response, evid fibrosis, continued to progof fibrotic maturity, the sa noted for the mature lesior G. The formation of asbe by blood and tissue ei fiber to produce fibro? Intratracheal injection typical asbestotic tissue re of progressive reaction ob due to the formation of as H. Aluminum hydroxide long fiber asbestos. Aluminum hydroxide • prior to intratracheal injec of asbestosis in rats. I. Inhalation of asbestos <: of experimental tuberc the dust. The apparently mild i to the stimulating effect process in the lung. The since it is based on an in' exposed to only one kind shows that when the inf< exposure, there was tern with subsequent healing; ■ dust exposure, the course The latter finding is quite dust or with mixed dusts c of quartz on a tuberculou infection is initiated after on a background of estah' sensitive test, when appli the latter had an advert inability of asbestos dust tuberculous process fum. inhaled asbestos dust has pulmonary tuberculosis. This investigation was ngroup of companies of the a VORWALD E T AL.—STUDIES OF ASBESTOSIS 43 lesions, due to contraction of the fibrous tissue. In contrast, an imma­ ture tissue response, evidenced primarily by cells with little or no fibrosis, continued to progress. It is assumed that, following attainment of fibrotic maturity, the same process of contraction would ensue as was noted for the mature lesion. G. The formation of asbestosis bodies represents a coating of the fibers by blood and tissue elements, which results in loss of ability of the fiber to produce fibrosis. Intratracheal injection of asbestosis bodies failed to produce the typical asbestotic tissue reaction in experimental animals. The cessation of progressive reaction observed soon after exposure terminates may be due to the formation of asbestosis bodies. H. Aluminum hydroxide failed to neutralize the fibrosing action of the long fiber asbestos. Aluminum hydroxide added to the suspension of chrysotile asbestos prior to intratracheal injection did not retard or prevent the development of asbestosis in rats. I. Inhalation of asbestos dust did not alter significantly the final outcome of experimental tuberculosis in two series of guinea pigs exposed to the dust. The apparently mild influence of asbestos dust is in distinct contrast to the stimulating effect exerted by inhaled quartz on a tuberculous process in the lung. The interpretation must remain tentative, however, since it is based on an investigation limited to two series of guinea pigs exposed to only one kind of asbestos, namely, King’s floats: Table 4 shows that when the infection was coincidental with the onset of dust exposure, there was temporary progression of the infectious process, with subsequent healing; when infection was initiated after 26 months of dust exposure, the course of the tuberculosis was not appreciably altered. The latter finding is quite different from our usual experience with quartz dust or with mixed dusts containing quartz, wherein the adverse influence of quartz on a tuberculous infection is manifested most strikingly when infection is initiated after a period of dust exposure, viz., superimposed on a background of established silicosis. As indicated above, this more sensitive test, when applied to asbestos dust, failed to demonstrate that the latter had an adverse influence on a tuberculous infection. The inability of asbestos dust in that experiment to affect unfavorably the tuberculous process furnishes strong support for the interpretation that inhaled asbestos dust has no more than a mildly unfavorable effect on pulmonary tuberculosis. This investigation was made possible by the generous financial support of a group of companies of the asbestos industry.