Document zMvOvYeKG5D3qyEpD91gY0O3

AFFIDAVIT WASHINGTON DISTRICT OF COLUMBIA ) ) ss. ) BEFORE ME, the undersigned Notary Public, personally cane and appeared MICHAEL RHODE, a person of the full age of majority, being of sound mind and body, who, after being first duly sworn by me, did depose and say: I, MICHAEL RHODE, am an employee of the Armed Forces Institute of Pathology, Washington, D.C. I am custodian cf the original archives of Dr. Arthur J. Vcrvald. Paces 1 through ^ -- attached hereto are true, correct and authentic copies cf documents from Dr. Arthur Vorwaid's arcnives. .`he paces attached are ASBESTCSIS - Experimental Studies ;u The J 5. r5r.ic labcrarcrv , ?rl-r.2 Jc'rrs"^2n.vi'l3 Zccr2* 1 ~ 4 -s - m4 lectenber 20, 1943 Dr. Vorwald was the Director of the Saranac Laboratory cf the Trudeau Institute. Upon his death, Dr. Vorwaid's archives were donated to the Armed Forces Institute cf oathclocv tv his widow. suspi Armed Vcrvawc's archives are m such condition as to raise no n concerning their authenticity: they were received by tr.e rces Institute of Pathology from Dr. Vorwaid's widow after RHODE AFFIDAVIT - Paj 1 ol : PCC EXHIBIT MET-503 Dr. Vorvald's death; they are presently on file as authorized by law in the National Museum of Health & Medicine, Armed Forces Institute of Pathology, Building 54, Waiter Reed Army Medical Center, Washington, D.C. 20306-6000; and the archives have been in existence for 20 (twenty) or mere years. MICHAEL RHODE, -AFFIANT SWORN TO AND SUBSCRIBED before me, the undersigned Notary Public, on this the _ ~ ~ day of April, 1392. "v lomission Extires: 1? - -'s' ' RHODE AFFIDAVIT - Pile : it; r * iSENIM AS3 iSn5 I' Ebrperisicnta' Studies ^y TEE SARA3AC ElBOEATOSY sapjatac la-ts, tcee Seoort to the 'CE5S-LA5TTUE CORPORATION 7S7T TORE, '.V5X TCEZ September 30, 1948 nM i c-_ t 2. Introduction 3. Asbestos Vbor-als S'. Ib:cnriasntc.i "If thodo 6. S-pscZ.ec- Susceptibility- 7- SccZLLey Cnaracter-bot Lzz c i .abestcc 3. Hate or 'Tissus H-aaction to .-obosios libers ?. isbestosis bodies 2. UMiliTIOIi ~TT:r,ri"Wc. .ng's floats 2sbe.st.03 Oust Ousting uaterial 20 o lust 2or.car.tr3.td cn -asetien in A-- -al s 'Imres Pigs Hate ar.d Tups cf reaction Progression Infection Coir.cider.t Tith Oust Inhalation Infection after Oust Inhalation Asbestoses bodies babbits cr 25. Short-fiber Asbestos 3ast 26. Dusting listeria! 27. just Composition 2Q. Dust Concentration. 2S. Size-frequency of Dust 30. Reaction in Animals 31. Guinea Pigs 32. Rate and Type of Be 33. 3257 e 37, Progression .-.3bestosis Bodies Rats Rate and Type of Be Cats Rate and Tope of Pa 'C-rsy Char.res L:. isbestc3is Bodies ', T Babbits Ll2. Rate and Type of Fa 1a 3 Asbestosis Bodies LI*. Surmaiy and Interpretation io. ICO per Cent 3a.ll-rn.lled i.sbestoe ! 7 Dusting .'ateri&i ! -- Dust Corpositutn. o L5. Dust Concentration L9- Siss--frequency of Dust i 3"S i I, 15 -3 17 50- Reaction in Animals 51. Guinea Fipo 52. Rata and Type oi' Reaction 53. Profession 5U. Lyrph Mode Ir.voiTanent 55. Asbestosis Bodies 56. Hats ar.d Liice 5? SumarT- and Interpretation 50. bcnn-fiber Asbestos Oust 59. Dusting ''aterisl 60. Oust Composition 51. Oust 'Concentration 62. Sice-frequency of lust 63. Reaction in Animals oL. 0-uir.ea Pips - ~ Hato ar.d 2/pe of Beaction 66. Progression 67. Lymph Node Crrvolreoient 68. Asbestoses Bodies 69. Cato 70. Bate and Type of faction 71. X-ray fnarpes A. loos 73. Bate ar.d Tyne of Reaction ISS 23 23 23 2k 2k 2h 2k 25 25 26 26 26 27 27 27 27 25 29 29 30 ;C 330 Lace ara . r:r c. . ilzi L .-'jay r..C.c:*"V ?u.r- : . ^ :':icy7!r;-: rijcsn+r cr. cl' \.rous '-cvi _ . . r.irever.ccs c ;percccu'. 3 L"ocrr. :'.ec.:T3 ^.ciccn r: -.n -c rr=^.^i:r. oc .',2zes':;si3 lc.ci.3i .'9. Sr-fsciicn ?C. Scsceptibi.li.t7 i-c Tuccrrdsus Iciectccr. 91. I'csceptibiib.t7 it -cr.-tuberccl:cr l-cccticn A337HACT Asbestosis is a pulmonary disease caused by the inhalation of asbestos dust. In animals it is characterised by a peribronchiolar fibrosis which seem3 to be the result of mechanical, rather than chemical, irritation of tho tissue b7 asbestos fibers. Only the long fibers produce a typical reaction; 3hort fibers are relatively inert. The fllamented structure of the fibers is an essential factor in the mechanism of irritation. A character istic tissue response can be produced by non-silicecus as well as siliceous fibrous minerals. Inhalation of asbestos dust apparently does not alter significantly the course of experimental tuberculosis in guinea pigs. The asbestosis body, which is a specific concomitant of asbestosis ar.d forms soon after the entrance of the asbestos fiber into the lung, is believed to prevent further damage to the tissue by the fiber and thus to limit pro gression. of the reaction wren exposure ceases. Aluminum coes net exert a protective action against the tissue irritation of asbestos fibers as it does against that of quartz particles. The bulk of the asbestos oi' ccmsrc; is chry.; toils, 2 'gC.2SiC2-2H;0, which is nir.ea in the thetford regicr. of the I.-evince cl lieuec. Inocidslite and snosite are also used conr-~.rciai.2y lave- in :pueh sailer amounts. Chrysotile occurs as reins in serpenlir.s, a mineral siniia" in clerical com position to chrysotile but which exists in anrsiva bit at. i is '~3.de up of microscopic fibers without tha parallel orientation characteristic oi ahrysctile. The massive blue black serpentine, which is unooth and soapy to the touch, is traversed by vein3 oi fibrous chrysotile Tarring in width from a barely perceptible line to six or more inches. The fibers ran across the vein and not lengthwise with the formation. Attention i3 directed to the nner.nl brucite, VgC.r^O, which is often found in the sare formations with serpentine end chrysotile and nay be fibrous in structure. It has no commercial value at present because its fibers are net sufficiently flexible to be used in tertilee but they ore capable of repeated longitudinal subdivision. ' unlike other osocstifom rincrals. brucitc is not a salients and for this reason it ~.as bean a valuable tool in an exterirsr.tal :ooiGS-u> for many years studies have been carried on by tha Saranac laboratory an an investigation of the cause, nature and development of asbsstesis. The present re port is devoted to export-cental Asbestasis. In it are described the animal ex periment 3 wath various kinds of asbestos dust. Another report, to re prepared and issued later, rill be oor.cemed ruth Hu.uar. Asbestonis and will cover the he sit; aau-eccs of corkers who have beer, ertesed to asbestos dust in an. industrial .cent. Although asbestosis la 32a is a chronic disease which requires years to develop, it is possible to reproduce in one or more species of animal character istic tissue changes which are similar to the lesions of human asbestosis. Since the life-span of the experimental animal is relatively short, it is not possible to develop the characteristic lesions in animals under the usual industrial con ditions. Consequently, to obtain a complete evaluation of the tissue response to inhaled particulate and fibrous material, it is necessary to accelerate the reaction by employing higher concentrations of dust than would ordinarily be en countered in industry. Tihils conditions of exposure are thus different, the information yielded by experiments with animals is invaluable in furnishing a better understanding of the reaction of the human organism to inhaled asbestos dust. S. Experimental Methods For investigating the biological reaction of the experimental animal to the various asbestos minerals, two types of technique have been employed, namely, the inhalation method and the injection method. In inhalation experiments, groups of animals - up to ICO or more guinea pigs and sometimes smaller numbers of rabbits, cats, dogs, rate or mice - are kept for eight hours a day in a cubical dust room, eight feet in dimension, in which a cloud of asbestos Also is maintained At intervals during the experiment, a few animals are sacrificed and the tissue examined to determine the nature and extant of the dust reaction, come animals are exposed for periods up to three years, fha injection experiments, in which the dust, either dry or suspended in fluid, is introduced into the animal by the intravenous, intraperitoneal or intratracheal procedure, are 'used, to determine whether or net a particular lust has a potential capacity to produce tissue reaction lor.g-tem inhalation experiments furnish information upon which great reli ance is placet: wtan estimating "-is degree to which a dust might be hazardous to industrial -workers, 'hatha:- or not atmospheric dust, even though potentially dangerous, can bo inhaled, pass the natural defense barriers and reach the pul monary tissue in quantities sufficient to cause damage can be determined only by inhalation procedures. Infection c:r:erimcr.ts are useful because in then contact between the dust particles and tissues is assured and the potential capacity of the dust to produce reaction car. be estimated accurately. When dealing with fi brous minerals like asbestos, she intratracheal method is valuable since it per mits observing the effect of the fibers on pulmonary tissue. 6. Species Suscentibiliw Unlike free silica, asbestos does not exert its specific effect in el 1 organ of all species of animal (labia 1). Injection of fine quartz into various organs of the guinea pig, rabbit, rat, cat, dog, chicken and even tadpole -rill urcducs silicotic nodules. However, similar injections of long or short fiber asbestos have res-ultad in a fibrous reaction in the lung urn, to a lesser extent, m the peritoneum but not in other organs. 7. ?ecu'1 fan Characteristics of Asbestos experience has demonstrated that most of the particulate natter inhaled into the lungs of can and animal is 10 nierms or less in maximum diameter. Larger particles apparently are excluded by the protective mechanise of the upper respar atory tract. In the case of fibrous materials, however, this restriction does r.o arrly and fibers ICO a no ev:r. 20C microns in length have been four.o in tr.e teroun al air spaces of human lungs. Ir. small laboratory animals exposed to asbestos oust the maximum length :f fiber found in the lung rarely exceeds iC rioror.3. Pot ever-/ kind of fibrous material is inhaled with equal readiness; for example, the synthetic liters if glams nccl upparer.ily are too inflexible to pa3s easily through the nose, pharynx, trachea and bronchi and nelcon rsach the terminal bronchioles and alveoli. Inhalec particnl-.ta natter cor.ss to rest throogncut the terminal air spaces (alveolar duct, atria, alveoli) in all pane if the lanes; inhaled asbestos fibers are drat retained in the respiratory bronchioles. Those vary snail tubes are immediately distal to bronchioles lined by ciliated epithelium. Their otto essen tial lining is a lor cuboids! type of epithelium but, as their rums implies, they actually function in respiration through lateral alrecli given off as pouche3 along their Trails. Either these pouches, or the abrupt c.nange in the character of the lining epithelium, or the decrease in diameter of the tubo, or perhaps oha combination of all three factors is responsible for local retention of -.he inhaled fiber. Only after asbestosis is erell established are appreciable combers of fi bers carried into the more peripheral air spaces. 3. late of Tissue P.saction to asbestos Fibers The rata of tissue reaction to asbestos is much core rapid -.hem to m active dust like quartz. Evidences of tissue response appear as soon as fibers have localized in sufficient concentration in spscilic areas. In rats receiving asbes tos fibers by intratracheal injection this evidence is risible us early as tiro weeks after injection; fer quartz dust the latent period night be two rcv.tns or more. The behavior of the tissue reaction to inhaled dust after the termination of exposure is net the same in silicosis as in asbestcois . In siliocsir, the young nodules become larger; in aso-esto3is, young scar tissue.that may have fo-.nted,contracts ar.d becomes mere danse but the area of irvciv-nenl decreases _m sioc. If exposure to asbestos dust is terminated after a brief period, the recer.tly-iothaied fibers la the lung nay cause the fibrous tissue response to continue ;'or a short tine, until the fibers hare been coated, lids progression is of only a slight degree and of little significance. ;. asbestosis Hedies fee peculiar structure imsm as the asbestosis body or curious body is a specific concomitant of asbestosis. The typical bed;-' is a golden-pellnr, bsadad or haustrated rod rhich may be either straight or curved. Often one or both ends are bulbous like a dumb-bell. The bodies vary considerably in length, and di mensions up to 250 microns have been recorded. It is believed that asbestosis bodies are cue to a deposit of protein and iron pigment upon the surface of inhaled fibers. In guinea pigs they form after about 60 dav3 of contact with the tissue. They are abundant in ran ar.d the guinea pig (see Table 1) but are much larger in the former, probably because the largersized air tubes admit fibers of greater dimension. In cats, rabbits ard mice there is an atypical coating of a few of the fibers after much longer residence in tbs lungs. In rats ar.d dogs r.o bodies could be discovered. Although the evidence is incomplete, it appears that the formation of die asbestosis bony prevents damage to the tissue by the fiber. I. HHAiiTiiN ~.x ,'^p. rvrvyrs Tour comprehensive inhalation experiments have been conducted at the Saranac Laboratory with various forms of oa'oestcs du3t. In sach of these investigations more than ItO animals were used and the experiments were carried on for o-arioas ranging from 2 to mars than o yearm. The four kinds of asbestos dust emclcy-cc are identified as "lag's floats, short finer, ICO per osnt ball--till sc, and long-fiber asbestos dust. 3honn by an average count of 0.5 sillion for particles 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 roaain- t Ing 5 or 10 months of the experiment considerably more c uow VS CXSw* S00. the atoaosphere. Average dust counts for ixpinger samples collected after this change were 53.7 ah 111 on for the usual light-field method, and 1.6 trillion fer particles larger than 10 microns. 15. Reaction in Animals to Iranied "King's Floats* asbestos Oust. Results of the investigation, briefly summarised in Table 3, show that inhala tion of King's floats asbestos dust produced a oypioal peribronchiolar fibrosis in guinea pigs but not in rabbits or rata. 16. Guinea Pigs. Seven groups of guinea pigs were used. In threa groups the effect of a continuous ar.d of an interrupted dn3t exposure was studied; in two other groups the relationship between infection and dust exposure was investigated. The remaining two groups were infection controls. 1?. Rate ar.d Type of Reaction. Guinea pig3 inhaling this dust for periods up to 33 months developed a characteristic fibrosis occurring in conical patches about the respiratory bronchioles, fixing this exposure the peripheral alveoli were not involved. The particulate elements in the dust were transported to the lymphatic system where they caused no signi ficant reaction; the fibrous elements reefiined fixed at the site of original localisation and were seldom detected in the lymphoid tissue. Pleurisy and flb--si3 in ihe sepia vers observed only when infection complicated the process. After exnosurs of npprcximsteiy a vbar, a small amount of cellular reaction had been produced about many respiratory bronchioles. As more dust was inhaled, it continued to accumulate in the same location and later stages of the disease consisted of ante ns ions of tha original lesions. raw areas rare net involved. Apparently, the inhaled fibers mere caught in the pockst-lilca alveoli .hat arc given off from the lateral rails of the respiratory bronchioles. There they Tere phsgocytiscd and cany of then were carried into the rail by migratory cells. Toncnucieer leucocytes attracted to the area caused an appreciable thickening of the bronchial rail. After 16 nontha a delicate fibrosis made its appearance. The process errolvod so gradually that mitotic division of fibroblasts could rarely be discovered: nevertheless, the number of fins intercellular collagcno ir fibers (fibrosis) steadily increased. As this fibrosis contracted, it partially closed the alTeoli, and with this atelectasis the lining epithelium assumed ito embryonic cuboidal form. The result was the adenoma-like appearance that ~iliis described in guinea pigs inhaling silicon carbide. Tha longer exposures resulted only in more thickening of the walls of the air spaces, largely due to an in crease in the amount of fibrosis. The fibrous tissue always remained cellular and never shewed the hyulinisatioa characteristic cf silicosis. It. Progression. The reaction produced in exposed guinea pigs did act orcgre33 significantly during a subsequent rsrioc of 3? months wh.cn the animals lived in a normal atmosphere. 3etveen 2 ar-d 11 months after exposure ceased, the cellular reaction had been completely replaced by thin strands of fibrous tissue. Observed still longer, the scar tissue decreased in amount but in the last animal sacrificed, 37 months after discontinuing dust exposure, some fibrosis was still risible. 15. Infection coincident with just Inbr-lvtim. if the group of LC y tinea uated tubercle bacilli (?.]_ strain) ji died or mere sacrificed before tra ysarc of dust exposure and rare reported in the paper bv Gardner and Turnings mentioned above. Seventeen of theca riiec from ir.tercurrs.rt noeur-onia. Briefly, the re sults were as follows: 10 revealed sc-.o oviaar.ce of spread of the tuberculous process; in 6 of these it was confined to the lungs and in the other Lt the abdominal viscera also vers involved, b'susily a slight local extension of the tuberculous infection had occurred but subsrpcsnt healing had resulted in fi brosis of both the pulmonary lesions and the secondary lesions in other organs. The healed pulmonary lesions showed nore fibrosis than is characteristic of either tuberculosis or asbestosis alone: The 9 a.-vi-aT s which were still alive after tro years of dust exposure were sacrificed at intervals during tho follc-ang year. In ii of then the primary foci of infection had healed irUh fibrosis arc even calcification and there was ho evidence of progression. In the other 3 the tub-ercnious foci shewed evidence of having previously spread locally: in L of then it had healed, by the tine of autopsy, with excessive fibrosis; in the other animal there was a ger.eraiiad chronic tuberculous pneumonia in cr.s lota and isolated prisary tubercles, icicn ware still active but had not spread, it the other lobes. evidence of extension of the infection was first seen after 7 tenths of rust inhalation; during the .text 20 months tore than half of the ar.itai? shewed an actively spreading tuberculosis and in 3 of then snail cavities had developed, luring the last 3 tenths no animals exhibited any evidence of active infection although in half of them the healed fibrous 3cars of previous extensions were ob vious. Sixty per cent of the guinea pigs with opreading pulmonary tuberculosis shewed tuberculosis cf the spleen and liver. 20. Irfsenior. m-arirocsed Torn an established uabegtosts. Twelve --itea pigs, after in haling asbestos dust for nearly 26 norths, were infected with tubercle bacilli and then recurved to r.cmal air. The subticuri tubercles in the dusted animals were Hi. Suurasuy and In tertr cation of Inhalation ngperiment with King13 r*lcata Erst. b'ne findings in ft? cr:=ruer.t >c.tn fang's floats oust can cs smir- iced under three headings. i. affect of the inlvaLed dust cn normal animals. Tha king's floats dust caused a charac teristic peribronchiolar fibrosis in guinea ?ig3 but not La rabbits or rats. lie fibrosis did not progress after the dust exposure was discontinued and the guinea pigs transferred to normal air. 3. Iffect of the inhaled bur, or. t-.berculosis in guinea nigs. In guinea pig3 in fected with attenuated tubercle -cciili and then placed in the dust rocs, the results were more variable char. in usual in ar. experiment of this type. few animals showed uo sign of progression; ir. .cost of then there was evidsnee of tem porary progression -rich subsequent healing; io one animal there was continuous progression to beach. Ir. contrast, w.an guinea pigs, after being infected, are exposed to quarts instead of asbestos bust, cne infectious process continues to orogrsss and eventually cartes t.-.e beat", cf tte animals. In the other hard, ax- rosure cf infected anunals cc a nau~ilcss rust like calcit-a cr gypsum ices not lead to ary progression of the infection, fumes. pigs infected with attenuated tubercle bacilli following tne termination of about two years' exposure to asbesto3 dust did not develop progressive disease. The only modification of the infection was in its localisation, a few bacilli being retainac in the fi'or'Ous terminal brcr.chioles and forming tubarcles `.'are in addition to the usual foci beneath t'.ia pleura. In view cf this "in: --icy vie unusual nature of the response and tha high treporticn. cf deaths from -r.Cercumr.c pr.e'coanis it is feit that oaf irate ccrcuu- aior.s as to the influence of this dust on the course of tuberculous infection are r.ot "ratified. C. Effect of tuberculous infection on the reaction to inhaled dust. dust to produce fibrous tissue. This change occurred rhsfhcr or cot the bacterial lesion ran in contact frith the area of dust reaction. 2$. Inhalation Excericer.t frith Short--fiber Asbestos Trust. Since hazardous dusta lik9 quartz are most effective in producing fibrosis vhen the particles are 3 microns and less in size, an inhalation experiment was carried on to detersir.6 whether this condition in trto also for asbestos dust. It was thought that by using a short-fiber asbestos dust consisting almost entirely of fibers and particlo6 smaller than 3 microns an accelerated tissue response night be initiated and ar, advanced reaction obtained in a snort tine. The previous inhalation erperir.er.t with King's floats asbestos, which contained fibers from 1 esc. to 1 micrcn or lass in length as well as a great caal of particulate natter and whies produced a typical peribronchiolar fibrosis in seposse gui.tea tigs, served as a basis of oonparison. 15. The rusting naterial for this experiment was ferwardsd iron the uanrille plant of the lohns-Hanvilla Corporation. It vras the rerears of fibers collected in dust bins after a carding operation and screened so pass ICC nson. Since the naterial as received contained tarry long fibers, it was ground in a Jteel ball elll to reduce practically all the particles to 3 microns cr ies3 m size. When used alone in a standard dusting rschine, this fir.ely-grourd asbestos handed to pack in the hopper and it became necessary po mis arse velum of toe -onground material with t.vree volumes cf the ground to generate a satisfactory fust cloud. The adiitior. of the s-vu.I quantity of ungrcur.a esusstos was unfortunate because if confused t.-.e ir.terprefaticn of results. Ircbably tho merer coon: of reaction that developed was due to the long fibers in the .mirt-cre although tbs data of this experiment do root prove tnc pcirrt. 27. Tha composition of the shart-fiber asbestos as received la disclosed 07 the chemical aid petrographic analyses given in Table 1. Samples taken before and after grinding yielded about the same values on analysis, indicating that there tras no contamination from the mill or loss of water content. 23. The dust concentration varied somewhat during the experiment and light field counts for atmospheric samples collected inside the animal cages with tha impinger apparatus ranged from 83 dllicn to 132 million. The average of counts was 130 million for the first pear of the experiment, 131* million for the second pear and ILC million for the third pear. 2?. Sime-fresuar.cp measurements of air-floated dust from inside the cages at a magnification of UCCX revealed a great preponderance of fir.a can ticles sTable 0). hearIp 50 per cent of the particles seen rere smaller than 3 tiorons. ;C . Reaction in AnJ-r.l s to Inhaled Short-fiber As best cs lust. leer re 3 ci e 3 of animals - guinea pigs, white rats, cats and rabbits - were used in this experiment. The results of t.te dust exposure, which are s'---a-- ?d in Table 6, will bo considered more in detail below. 31. Ouinea Pigs. light/ guinea pigs were originally placed in the dust oocm 32. late ar.d T;~ne :f Teacticr. The type of tissue react!1 0 s_ec short-fiber asbestos men essentially the same as that already observed la the experiment with Kiev's floats asbestos. The rate of reaction al30 was approxi mately the same but the extent of involvement Tri.th the shcrt-fiber dust was very much les3 sod after 16 to 2L months of exposure only a very Terr snail foci of reaction, which generally required microscopic sxamination for detection, were produced in the guinea pigs. Until exposures had continued for approximately ona year, there was little tendency for dust-containing phagocytes to collsct into clumps. By 16 months phagocytes had begun to collect about the walla of a fax of tha respiratory bron chioles with a little proliferation or infiltration of mononuclear cells in these wails. There rare also soae mltinucisated cells but they were always of tha inert forsign-bccy type. At 20 to 2d months the cellular clumps were sonatinas quite marked ard 3cmetincs charges in the epithelium resulted in the nbsma-lihe or "'adenomatoid'' aepearance previously described in Section 17. in nnst of the subsequent manners cf the series, the reaction remained cellular an type. In a few, however, fibrous elements dominated the picture. In the latter ruse, tr.e collagen was ;ale in color ar.d tenuous with no heavy swollen hyal: niciticr. -s in the rats described below, the alveolar walls might be nade up of a 'sand of collagen supporting a layer cf epithelium, but with no contained capillaries. In the tracheobronchial lynch nodes the reaction wma more pronounced cn this expertrent than in the previous or.e with King's floats asbestos, probably because of tha transportation cf an excess of fine particles to the nodes in annals inhaling inert-fiber asbestos. Th.e reaction was essentially am ir.crease or. rsitrslun, rate. reticular fibers. I if fuse chronic pleurisy without eviier.ee cf p-cinerary -electee aras present in a few animals. 33. Progression . L-. the 13-3A norths fol7.3rh.ns tho cessation of 20 months' exposure tc cunt, progression of disease was not definitely demonstrated but neither could it be absolutely disproved. owing to the varia bility of the response in difiarer.t animals. It the end of the dust exposure of 20 months two pigs were rend as + arc one os 2->. .'unong the 13 removed from dust the findings rare variable: in 2 tne reaction vrs o; in li it wan +: in 3 it was 3+; in 3 it was k+j and in one animal it -mas 5*. It is quite possible that those rrith the most narked changes had already developed aore reaction than the remain der by the tine exposure ceased. Since the more severe reactions occurred spora dically and bore no relationship to the length of tine after cessation of exporare the differences were attributed to variation in individual susceptibility. This rierw received support from the chemical analyses (Table 73, which often re vealed comparable amounts of ash and silica it lungs with widely different amounts of tissue change, for example, ths ash arc silica values vers quite sinuiar for three animals in dust 2C months and then ir. normal air 13--3/li months, yet the tis sue reaction fer one animal was u*; for sr.c tier, *: and for the third, only . 3k. Asbestoais todies. The formation of tsbestosis bodies was at first ex tremely limited, liter 5 months' exposure only a vary rare short body could be found, usually inside of calls, around the finest intracellular particles there were yellow deposits haring the same color as the asbestosis body, exposure of one year had permitted an accumulation of many longer fibers about which the ssbestosis-body coating developed, lest ;f these ware still short enough to be partially or entirely withit pmagocr-ti: cells. 3y the 2-th month and thereafter, tier ^-ere --mparatirely numerous altncugh stall rare 0 TThite Hats 5eventy-tfaree white rats ware exposed to atmospheric short -fli1'1'** 3 rKo *ZT V** er months. Sacri- fioi.ngs curing the first 10 months sere made bimonthly and for the remainder of tha experiment at less frequent intervals. 2-5. Hate and Tyre of Reaction. The dust cells until 3 months were Tddeljseattered and existed in foci only sporadi cally. Reaction wa3 limited to occasional slight thickenings of the septa about small accumulations of dost colls. In a few rats at 10 months, there mas a sug gestion of early fibrosi3 but the charge was so slight chat it would probably oe overlooked without the clump of dust cells to attract attention to tha area. Only 10 animals were exposed from 12 to 32 months. In each of them the lungs shewed minute patches of well-defined fibrosis distributed like that of asbestoses cut without asbestesis bodies. The lesions, visible only at a magnification of IrC diameters rr more, consisted of patches along alveolar ducts in vnich the walls of the air staces were vert thick, due to swollen collagen framework, loutsctime tissue and, foct-- Sielscncwski silver preparations revealed complete lc33 of capil lary bed locally, Cutside the collagen was a thin layer of epithelial cells. Teds bid not resemble tha 'adenomatoid" change characteristic of gucr.ea pig acoostosis. Nc pleurisy was present. Near tha lesions the air spaces were filled with phagocytes containing gray to yellow particulate) dust and a rare long naked a3be3to3 fiber. Careful search failad to reveal even a suggestion of ar. asbestosi3 body'. The tracr.eocrcr.c.v. al n.oces snowed compact focal cc_lecticra of mor.ocytic cells at If months arc, ao If months, some diffuse thickenarg of tr.e retirulur.. Ir. a few rats there was nefimite fibrosis along the msrgins of the node and extending into the ncbcAstinal areolar tissue. Compared with tr.e response to active dusts like quart:: ar.d chert the reaction to 3hort-fiber asbestos was negligible. Jesuits of chemical analyses mace cn the write rats ore given ir. Table 0 mi the average values have been tabulated in Table 9 for comparison rith similar values for rats inhaling other dusts. The concentration cf atmospheric particles to which. the animals were exposed' ins apcrcxinatalj the sene for asbestos ar.c quartz; Tor the gypsunt-quartz mixture. it was about trice as high anc far chart five tinss as high. It -rill be noted that the percentages for asbestos are lever than those for quartz or chart but are similar to those for the gyy.sua-quartz mixture, in which atmospheric agglutination tended to reduce the scene of dust irraisd. It might be inferred that the total quantity of asbestos dust inhaled was low or that it had beer eliminated from or dissolved rithir. t.-.e lungs. In the present state of our knowledge evaluation of these hypotheses is r.st possible. s. Twenty cats were 'isec in this inhalation short-fiber asbe3to3. eighteen were hapt death, tho urxnro period ranging from one month to nearly after a c ust exposure of 31-1/2 months, -era removed to nor was sacr iicec o acr.tns, and t.ne other cl months, later. 3:. rate and Tyre of Reaction. The reaction was essentially via. to an inert dust, e-er. after more than 1 pears of expo sure. The tissue response in this species was confined to microscopic foci of fibrosis in the walls of groups of sukpleural alveoli, rather than it the terirrcnchiolar areas. In one arena! the change was extensive enough to be visual iced on gross --rsoccnon of the section. o V.1T' S me C313 in -he subpleuraJ. zcr.s plus heavy lyrphocptis infiltration about seal! bronchioles. uC. Asbestosis foci". Cn erelong::u search a fax yellox atypical asbestosis bodisSj sccoth and rithcut haustrations, vere found in tro affinals exposed for sore than a year. hi. Rabbits. Eight rabbits srere exposed to dust for periods extending from one ->o ncra than fire years. The last animal -was reseved fraa the dust roon and loft in dorsal air 6 tenths before being sacrificed. 12. Rate ar.d Type of Reaction. There ras r.ev3r enough fibrosi3 to be dew8':ted grossly and there was no chronic adhesive pleurisy. I'icroscopio evidence of alveolar -wall thiclcening xas first detected after about 3 years of eorpcsvre arc vas seen in all five arinais examined thereafter. In one aninal that died of ::aral~i3 after nearly four years of axcor-zre the re^-rtion xzz e^terj3ire enc'j_g'n to be - siblo on .gross inspection of tissue sections. The possibility of puleoonar;.- infection in this aninal could non be ex- --d. .-.cv.'ever, 'n another a- - -a. tying tve years later the focal fibrosis *as not nearly as ccvious or as advanced,. .-reas of involvement, xhich xere largely visualized because of phagocytic reaction xithir. the air spaces, tended dcros(topically to becora core fibrous xi.th t'.-.s passage of tine but there was cover cuch encroachrent ncor. the liner. oi' air scacs3 ana the architectura of the lung 133 prase-re-d. Li. Inbestosts oo hcs. Asbestos b:acies veto not detected m raotits that 'iic-d ?zr'~ ir. ".he l hu wer seer, m eil andralo that had been centred to the cust; for core than three years. Stcxsarv- and ion The original, purpose of the experiment wa3 to evaluate the chemical theory of the pathogenesis of as'oe3tosia. It was felt that if the tissue reac tion to asbestos ire re chemical in origin an accelerated or accentuated response would result from ezposure to finely-divided asbestos, as is the case with quartz. This experiment, in which the reaction was slorer and less extensive than with King's floats. Indicates that the reaction probably is not primarily chemical in nature. Of the four species exposed In this experiment only the guinea pig rat reacted with characteristic peribronchiolar fibresis. The cat reacted with atypical sub-pleural fibresis and in the rabbit the fibrosis which occurred could not be positively attributed to the dust because of a strong possibility of pulmonary infection. d'ust cloud. 'Tr.en evidence of a dust reaction appeared in one guinea oi;s iurimg the expertmejit, it was not clear whether this was a tissue response .0 t.ns small number of long fibers in the uaground asbestos or was a delayed effect of the core abundant fine dust. Consequently, another inhalation experiment won started in which no onground oiaterial was usod. uc. The dusting material, rus the ground snort-fiber asbestos .sou or. or.a o apparatus was changed to an open type of hopper ana fresh oust was auded daily. -21- I I Cwing to the t-r.dsr.cr of the zazeri?! tc lore, r-'l crhtruio.o -- ich zeeh of the fibrous portion iron floating out of the hopper, the cicptrcal of the dust to: r.ot er.tirelp satisfactory and after 7 months of operation. the durtins mchins iss rscccrcrtsti to its original deszzr.. To prscene "pillinr'' or z.v fom-ution of spherules cf asbestos, steel wiro brashes -ere attached to the In side surface cf the hopper and to the rotating panels, "has ucvangeiv.c-r.h pare satisfactory results and was used for the remaining Z1 months of the er~jrlne:it. u7. The 'cccncsioicr. of the r.trr material i snort-fibor asbestos. e.:..i of cor. spheric erst liberated fron the ball-allied product in tbs dusting ma chine is given in Table 10. These values are based upon cetro--ap.-ao cvcdv and .7-rap diffractlcr. analysis. The atmospheric sample rc3 collected --.oh an elec t-static prsco.pioatcr after rare brushes had teen installed in the dusting o machine. Previous to this, the chrysotile content of the air-suspended ..caterial ass undoubtedly less than the 15 per cent value given in Taels IT. 7u an orb tr im retort, at nao stated that the alr-bcrr.e dust contained sren f par oor.. :f oarcsotlie before the wire trua-.es were msec and up to d pen cent aft .----nut:. ---- t.-.esa values were trctably low. quantitative estimates cm call-mlloa isoesToo dust map be somewhat inaccurate because it is difficult tc deter-ame he.: much cf a dust sample is fibrous chrpsotile and how much is rer.-fibreus cert cat its . Lifl. The d'ust concentration fer the first 7 months of the exp about ICG million particles par cubic foot of air. .-fee brusr.es had beer, mst ailed. the oust courts mere a little mm.cur a average for tr.e first pear ras lit tillicr.. The average cf omt; 'TZ o C<- -ISi-'-' .e ------.silts of atr.-omherle bust collected inside ths ;'r'~ ~>3~- czr^? with the electrostatic apparatus is reported in Table 11. ~~o carries rare r.a_\-.j, sue before the hire brushes rare installed -./.at altar the airs bruises trera is use a --saber proport: on of ver" Tine p. -Tt-ciss and also of icnrsr fibers was released into tiie air. Tutr.aa ripe. ran: e/ii .v re ~:re used in the inhalation a.--srirent with the ICO per sent bcil-roillcd. sacertss bust. The results are sums.--set in Table 12. --~e. - _'_d. 32 of -neur.r: pair.sa sits r rrscris:sr. ras started with ICC guinea pi at arsssu-s proceeded, thare were 3? acsid ric. .star T3 tenths of dusting the li su la the or or.e sirs: r.e enlr reac eer.ee of scattered phagcc;~tas and an occasions! ni.nute asbestesis zzij. it 15 and 2C sstths r.o gross response mas -.-Isibis on the tissue section but sicro3copies peribronchiolar foci of --aC --.a^r- sells could be seer., it 21 norths ther9 was still no charge large enoupr to oe -:;er with a hand lens eithergh rteroaccpic o 53. ffczrcsaion. The longs of uni-tnlr. exposed for the full crusting period (23 months) and than living in normal air for 2 months repealed the changes described above and also very slight peribronchiolar fibro sis. After 0 months in normal air the findings rare similar ant at 12 months 3 of !; arimls showed grc3siy-visibls characteristic peribronchiolar fibrosis with adenomatoid change. 3b. iTCoh gcd9 I.-.volmcxcr.t. rho tmchcobror.cbial rodo3 cs&ue td.crr.hiall/ asgativa uiil cucpc?vr3 had been continued for iorr than a /ear and a half. Ari,r..)s sacrificed at 12 xoaths and 15 concha revealed a few ainite collections of phagocytes containing particlas but prac tical!/ in fibers large enough to be recognized as such, .`after 2C months of exposure xany monocytes filled with /p] 1 o-- granules --are present, it 3C oentits fhars bad beer, a slight increase in reticulum but r.o fibrosis. So further changes occurred in the nodes, <' sbsstosis bodies ere not seen in the nodes of anr uf tbs guinea pig3. 35. iabestcais 3cdiss. himute asbestesis bediss rers observed as ;arl/ as 3 tenths after arposure began, cut the/ did .ot be- ccbs numerous until 15 months had elapsed. The bodies -mere short srd practioall/ all mere intracellular, although at 20 months sere -rere long enough to project beyond the cell borders. It is ixtorbaat to note that in the later moot-is of sxpasvxe tn.sre ran a dis ard that after exposure ceased characteristic long -csbestcsis bediss rare 3ssn. 56. Thlta Hats and "ice. In this experiment 10 rats uere exposed for peri:Is up to 20 months and 2l rice for periods up. to 12 It z.\2 3^th north, it had famed out :t ins paramhri~:. .'.-.2 Issio.ts -ere rather sharply localized ar.d the extensions iron cifiarcr.t bronchioles showed no tendency to fuso, even in anirals exposed for the mximun period (3 pears]. Although the ~wtra-nn'.-rr --r .'suction sosss-inss rsaenri .he tle'oru, iter." vus involvement of that acr.b'rnns. ''o enphyseva was visr.'o.'s 0.0 any point. lore thickening of the larger bror.chi rith a chronic inulannatcry ieflltruticr was re vealed, but it probably eras no rare than would be prcdv.ccd by a similar exposure to any dust,. For the first ; months the phagecyder consisted of r:r.:oP:s or 7ery or.all giant cells; Later, giant ceil forest ion --as - ors crcnir.snt. Ift=r 15 norths the giant cells were Large, filled with vu'.Lowisi-orcTm rogncr.t and sonatinas vacuolated- An occasional animal shored or. .\dnl:cturs of col,-r.crrh.c-- nuclear leukocytes and, in guinea pigs exposed for a non.'.'.:cranio coruc-d, eosinephiles. The reaction ras at first entirely cellular hut 'ey Id norths fi brous tissue formation was definite. Inrever, it never a the. r.c-d a s~ste of - necers- end of exposure. lesions and tr. the ctage of davolotnant attar,-ei at the Analyses of the-lungs (Table Id) disclosed that although the tissu. response was each greater in these guinea pigs than in those exposed to either she:t-fiber or bail-stilled asbestos, the amount of nir.eral natter in the lung ash was 1 c:. r.ea otss exoco&d o 2'13 v_ss\:e, rrcloped trap a outset,ion of .mL'cstcsis -.r.d reaction ras lirited to -theugocvtosi, ; of irt-aTpd particles by rrioely-scattersd dust cell3 uhich retained free ir. sir spaces or rare transported to the tracheobronchial Inroh nodes, "o ashes ioni. '.'Cdie3 rara found in the rats bvt in `ho nice .nr: -rere a very ferr snail ccn-h3.ustra.ied iorns riihin phagocytes. In 21 nouse lungs sectioned there were 3 instances of pnTranary ar.aucun (lii,l;. 57. Sumaary and Interpretation. fee tissue reactions observed in this erper''r.~at rare iruch lass ixuacciru and sierrar in csveloprnnt than in tha previous investigation -.-ith shori-^Tibor asbasocs. 5ir.ee presumably there vero ferer fibers iongar than 3 uicrocs an '.he natarial 'usee in this exparinsnt, uhe results herd tc cor.fim the interarotation uade in Section LL of the short-fiber a:--sriccnt that the reaction probably is net o priuarily cherical in nature. sarved in this expaninert rut cot in the others, tha foil mint; ir.ierp rotation ra offered: TT-.er. the reaction 13 Trell-cevaiopcd at the tcmir-aticr. ra' exposure.t.te contraction of the fibrous tissue mould otcc-ure any possible progrossion. Ir. true exeerioent, horrever, sir.ee orJ.7 the earliest stage of reaction r-a- -resect at the tics of renoval free dust, its sucsequent progress ras appareet. It acoulc he acted that the degree of progression m3 so s.'lgnt that it car. have little, _i O < Sraxtrlnant with -orur-fibar Asbestos Host ATtsr animals inhaling short--fiber asbestos dust for acre than a year had failed to develop significant reaction, the hypothesis that asbestosis is pro duced by the icscnanicoi irritation of lor.- fibers as given aided support. Since the Kins's floats asbestos used in the first inhalation stperimer.t had a rather low content of fibrous clm-ysctils and contained considerable serpentina and other impurities, it was decided to conduct a nett inhalation experiment with a purer fora of chrysotile Tillich Mould be richer in long fibers. o'?. The dusting material employed in this investigation was obtained iron the Kanviile plant of the fohns-iianville Corporation. Samples of se veral varieties of asbestos dust were first submitted to the 3arar.se -atcrraicry for emanination ar.d one -mind, identified as lot D, which was low in rap-petite and chromite and had a fibrous content estimated to be about 7? per cent, was selected as host suitable, Iteol wire brushes were fastened to '.no inside sur-- face of the hopper and to the rotating paddle in order to .open up the miles of asbestos and liberate more fibers into the atmosphere. bd. The cocmositicn of the long-fiber asbestos used in this experiment is indicated by the clerics! and petrographic analyses given In facie la. ft appears that this material was a much purer fora of asbestos than the shortfiber dust U3ed in other eoeperimants. This is borne out by comparing the approx imate analyses of the long-fiber and shGro-iiber idu3t in Table 1J. cl. The bus t concentration 3.3 revcaled by i-.pLn.ger samp *-3 s e r lie ' e animal 'TB-3 'TOZr. 1 rarer than the concentration for the emu an ins r. ts srvert--fi-er or illlec 0'03Z. ?cr the firct year of ire errer:_rar.r mi lore-fiber asbestos the average of the light field counts was 32 million; for the second rear, ao million; for :'h; thi-d ;-==r, 35 ail-ion; and for the fourth year, Ii3 million- Hxaainaticn of the i--pinger samples irith dark field illuninatioa disclosed thet nany fine ncrticlso less than one micron in sd.se accc--anied the larger particles ana dark field ccun,ts =re, on iiiG onerage, about 5 cr 6 tinss larger than the light field counts 62. The sina-frequency of atmospheric samples cf the long-fiber asbestos dust and of the tall-millad dust is shewn in Table 16. Both samples were collected with the electrostatic precipitator. It trill be noted that there was far acre fibrous material in the long-fiber cunt. 63. Reaction in IninaLs to Inhaled Icng-Tiber .-.sbestos fist, luir.ea pigs, cats, rats arid mnee ware e-Tnlo/sd in the irivalstion experiment with Long-liber asbestos. Results of the e:.-perinerrt, sumtariced in Table 17, are described in greater detail below. :ent isa V .ea ri^s* tUw'jC 3 of rreunonia arose in the dust room ar.d about or.e-third of the animals tied or were -cLlLed. To replace them, 36 none guinea pips were added to tte surrirtrg group in the dust roca. 65. Rate and Tvte of Reaction, Histological enaninatioa revealed grossly risible lesions in the lurgs after 3 tor. is bronchioles, it If ncr.t.ts, thars were ader.onatoid or.angos in the air spaces and by tie 16th aor.th a definite fibrosis was ireser.t m tress areas t_t half tr.e o aninals. The fibrous lesion could to seer, macro sc opica.Ily at fC norths, from thi3 tins on the reaction increased In extent and in the nnctrnt of collagen and 3oif these anirrsall.s, bullai at curious periods op to 111 tenths alter exposure, revealed lesions as large as those in the group sacrificed at the end of the 20-nonth exposure period or those in anlrnal s which regained in the duet rooa in four of the six re-mining guinea pigs trere so snail that thc7 were visible onl- wit;; a hand lens. .Reaction in the group ezcposed Tor 27 months and then t ransierred to a noma! atnosphare was quite siodlr.r to the response in the 20--nonth exposure anizals mentioned move, nevrmer. oo-ail foci were al-warps visible cn gross inspection of sections .of all guinea pigs of tha 27-ccr.th series but in no Instance was there evidence :of extension of the reaction. 47 Ivnrh lode Involvement. Reaction in the tracheobronchial lymph nodes was first visible at the third north of ex- CCS `iCT S -t the rtn nrntn "atones of cellular connective tissue began to arc-ear in. 1 9 re-.rilSLz oj~.c th.2 ilicd ~or.t,h nest of the code b-id esar: rerLicec by -receive tissue. -hi3 ci-rire, which resana-sd that in ear_v si_iccuin persisted to tbs er.d of the accoox -er.t. oc-e animals, as a variant, shewed teavv 3r.eet3 cf iiff'ise mcr.3c7t.3s and large active giant ceils but there was ne-rsr anj r.ecresi.3 :r hyaline formation. The spindle-shaped new cells were vailcrvish in color fro;: fra pigment granules that 3tained for iron. >fo fibers or asbestosis oocias ware seer.. . J isbostesis 3<r ` rs. Althcugn asbe3tc3i3 'oc~-es ware seen as sarlv as :r.e - rfc.o-- crr-vi <*< i- rar-7? ar.d r__rd it ; months tore were, visible, chieflv coiled inside giant ceils,- arse it t --ntt3 - bocias 77973 Ct2,2 Lr. 7cr.r.3C-ive tis3ue. They became dearly a^-r.a-Lr." as zxtcsSt'j_jL,rTe9 nremessed although in c;oorr,ee later ar.innls t,hhes assbbeessttoossi.i3s bocdi.e3s3 waeere 59. Cats . four cats inhaled the lor.g-fLber asbestos dust for periods of lit, 2?, 33 and 02 months, respectively, and were immediately sacrificed. Two ether cats, after bains; emposed to dust for IB months, lived in a corral atmosphere for an additional 2li norths. 70. Hate and T'.pe of Reaction. Exposure for lit months ru sufficient to produce cellular accunulationa of phagocytes arouai terminal bronchioles and peripheral arterioles together with coapact col lections cf similar cells in '.he trac'neobronchiai lyru:h nodes. At that tine there wars no typical asbestoses bodies, but smooth pointed Tallow fibers were seen very rarely. Tilth continued exposure, up to L2 months, reaction in the locations noted crogressed to the formation of cellular comecti-:e tissue which made weli^defined sheaths about the respiratory bronchioles and arterioles, cached lympr.cid hyperpla3ia and lymphoid infiltration of bronchiolar walls. The bror.chiolar epith elium was low ar.d flattened, giving the tubas a smooth contour. fpgrioal as'cesto-- sis bodies were not formed although there was an occasional yellow, smooth, pointed fiber. .Vo pleurisy was present. The reaction was similar in location to t.tat in the guinea pigs, but fibrosis was rich slower in development, and had not reached the sane degree of maturity. fi. l--tay charges. Roentgenograms of three cat3 ware made after sxpesure periods of 2?, 33 and L2 nenth.s, but tissue changes were cot dense enough to be seen or. an X-ray film. 72. Hat3. Although 22 rats wane placed in the dus ccrda and were not suitable for study, was exposed for 1? months and four for 25 souths. were ticn and offer a 'oasis for conclusions. 30- Rate and Tore Reaction. All Tour animals sacrificed at 2; months showed a wall-marked peribror.chi.oIar fibrosis. Li the 19-onth animal, reaction was ju3t beginning. Asbestosis bodies were Toractioaiiy absent at booh 19 and 25 norths although two snail smooth bodies wire found in the 19-month anicial after a long search. Thus, these anlnats exhibited fibrosis without asbestosis bodies. 7lt. Itice. Out of 20 white nice used in this experiment, 11 lived a /ear cr mere in dust and died or were killed without showing an appre ciable degree of pulmonary infection. 75. Rate and Type of .Reaction. Reaction was limited to phagocytosis by mononuclear cells. Usually these rere wide ly scattered through the air spaces; a limited number were grouped about the ter minal bronenioiss producing some thickening of their walls. There was r.o sug gestion of fibrosis. The striking feature of the experiment was that ? out of t'-.e 11 mice ;d2 o-er cent, exmosed to dust for a year or more shewed pulmonary turners, usually adenomatous in type". Th.ese lesicr.3 did not contain dust or asbestoais bodies. 'h-aroi-i asbestoais bodies wore observed in an-!-a-! n killed late in the experi ment. Thus, these animals exhibited asbestosis bodies without fibrosis. of this ecccerirer.t ras to evaluate the lttortar.ee :f l:rj; fibers in me tissue 'estrnse to tr-calec ashes toe. Jhe results t.tL: ate strong!/ tr. at . - r r_r - -- c^rs ar e rr.si'cle for the thus, ir. ^uurea rt;s reaction devc-orec e cate -ore extern '3 t.ian m ceres exoerccents in spite of a 5r.aJ.le: cor.cnrr cr, of atr.cspher: dust and a lower mineral con- in cats although in a previous experiment -with short-fiber dust it did not develop in this species. The cause of the cellular fibrosis ia the lymph nodes of the guinea pigs is not tloar. it ill :.o. t-c-oia c-icr inhalation eotreri.tents ascestes. L30C7H. EJECTION EZFERHENTS In order to determine to That extent the various fibrous minerals possess the capacity to produce tissue damage, numerous injection experiments were per formed. In these experiments guinea pigs and rabbits were used and the mineral dust was injected by the intratracheal, intraperitoneal and intraxer.cus tech niques. Tor the purpose of simplification the findings in each series of test* hare bean condensed and reported in tables, to which reference will be' cade Later. 72. sxugriner.ts -sing Intratracheal Technique. 3ir.ee the asbestos minerals do not cause a typical advanced fibre a 13 La extra-pulmonary tissue, the intratracheal technique is the serfarrec way of in troducing fibrous dust into the experimental animal. In this method the dust suspension is Injected by means of a special needle or catheter deep into the trachea, from which it flows into the lungs. 75. Tomcarison of fibrous and ren-ribrous Tusta. To demonstrate that the ability of aace3tcs to produce fibrosis resides in its fibrous character, the series of injection exp-er menta reported in Table 19 were t-;ricrre-d. Th.e tests were made -tth irheatod long-fiber cirrsotile and 'fith chi-ysotile that had been ignited to destroy its f flexible structure or ic.H-tillid o v rgoi'c > ; jury-' oi Tibor' ; m.irons arc less. At the sane tins icr-trol Vs^.r -or-; -ace Till carruntme, las one sans chemical composition as c.hryrotils :u; is ncr.-fibriit-;. -% rotier jf the fibers subjected to ignition or shor-sra:! by bail^niil.ir. raid Iron iheir capacity to cause serious tissue dasnge. Tgnitior. grx'uced .iranrtar.t changes in the chrysotila fibers, among them ceir.g loss of ornater. an c.Vo.eratr.ou frer. a flexible to a brittle structure and mo:sibly other chant os. 30. Ccmarf son of ~-irt:u3 lorg-Tiber inio-c. Soooe -r=rr; interesting firdmas ire disclosed 07 the results of the experiments included ir. Table TO. first, oil. ode iocg-fibe: asbestos minerals tested, with the exception of anthcpryllite. pr-cduced a tyrtea:, fibrosis. It 13 not entirely clear n/ anthophyiiiie bevaTed iifierantiy- from oho oo.-.sr asbsstor minerals. Ttif ortur.ateiy, ref? animals lied of rreur.ar.ia within oho first ixo wee-3 of tho experiment sr.c. the renaming animals wore sac-ifii-i ai 1. : and 12 decora, with the mineral br unite, nr.iob is rot 1 silicate out ir a olerous minerals was obtained, lince the brucito 'used contained 3ni/ C.JC per ccmt silica (as an Impurity), it is obvious that a siliceous component is not an essential factor in the development of anbestosis. Third, no fibrosis resulted from the injection of glass mooi fibers, even though glass wool resembles asbestos ir. stem rays. There are f r.bia-or.tal niff in shore lengths, is fairly ro.gid, wmaic er. asbestos fiber of t.-.e oame uursoet 1= a O ability. It i.-ould seem th.it tb.13 structure and the associated .lexiciliiy are -3L- UJ. nroeriraents Using Intraneritcneal Technique. the results of injection experiments with the Lntraperitoneal technique are given in Table 23. It will be noted that the long-fiber dusts produced a fibrous reaction while dusts composed of particles 3 aicrona and la63 in sice caused only an inert type of response. These experiments indicate al30 that the fibrosis initiated by the irritation of asbestos libers is not restricted to the lungs, as was fonnarly assumed, bat can be produced in the peritoneua as well. IXCTlV. OTHER SIF^ BESTS TTITH ASBESTOS HIK5RALS A number of additional experiments wars conducted to throw more Light on specific phases of the asbestosis problag. 3J. Protective Action of Alumina Cbonpcunds. Intratracheal injection cf a suspension of long-fiber chryuotile to which colloidal aim*, nun hydroTila had been added revealed that the addition, of the A'.-ord compound did not prevent the tissue irritation produced b/ cbrysctile. If ary-hing, the acute itflarnatcry response to the iuject-ed fibrous rinsrsi was accelerated. One month after the last Injection of the dust suspension the bronchiolitis was becoming fibrous. 36. Pomation of Asbeetosis 3edias. The iron in the coating of the asbestosis body appears to b e d-erived fron blood or tissue elements and not, as has been suggested, iron the mineral fiber, following subcutaneous injection of two binds of chrysotile into the --tin of guinea pigs - one bind containing 2 per cent and the other C.2 per cent rejCo-- the asbestosis bodies were equally numerous at both sites of injection. _-,c_ 4r An attempt to produce asbestosis bodies in guinea/pigs by implantation of three ailk bags containing fibrous chrvsotile was \1nsucces3ful. One bag planted ~---------- / subcutaneously in the abdominal Trail disappeared; the other tan bags, placed in the peritoneal cavity, produced a little foreign body reaction but no asbestosis bodies in a year. Intratracheal injection into guinea pigs of asbestosis bodies recovered from human lung tissue failed to produce the typical tissue reaction to asbestos fibers. The injected material was obtained by digesting with sodium hycochlorlte solution lung tissue removed at autopsy from an asbestos worker. The asbestosis bodies could be seen in the guinea pigs for at least a year after injection. This experiment shows that the asbestosis body has a rather resistant coating which is not destroyed by moderate hypochlorite treatment and may be -air in vivo for a year or longer. IZZX7~. TS5CRT Of Z^P-ITAl.T ACTION 0? ASBESTOS MUIZSALS Two hypotheses have been proposed to explain the tissue Irritation and reac tion rmwd by asbestos fibers: the chemical and the mechanical. In the chemical theory, which is based upon experience with quarts, it is assumed that the as bestos minerals dissolve in the body fluids and that in this process their bases are leached away to leave silica in a form capable of iriltatlng tissues. Accord ing to this hypothesis, asbestosis would be merely an indirect silicosis, uevaral facts T-atu cha chemical theory untenable (1) intratracheal injections of brucite fibers, which had a silica content of only 0.50 per cent, caused a typical fibrosis like that produced by the asbestos minerals; (2) free--eilica particles increase in potency as the particle size becomes less, but asbestos fibers shorter than about 10 to 20 nucroc.c a-c relatively im.ociocc; (j) clurioun hydroxide neutralizes the irritating effect of cruartz but net of asbestos: (1) serpentine has the sane chemical composition as lens-fiber chrysotila but it does not produce the sane kind of tissue reaction; (?) there is a Triidde raanng/ e in the chemical corpcsiticr. the nicer a Is Tfnicr. do 0 csbe -bests 'flse Table 2h). In view of this evidence it seers mere 1 that asbestesis LS caused by an unusual mechanical irritation froa Ions asbestos fibers. Probably this irritation is related to the peculiar filaxsnted structure of the fiber ar.d the associated flexibility, -which are possessed by no other foreign body I For example, ignition of chrysotile fibers changed their structure and cade then inert while the sane fibers, before being heated, would produce fibrosis (see Table by). Further support for the theory of aechanlcal irritation is that asbestesis occurs in an organ of udgh nobility - the lung - and that a fibrous reaction can be produced by injection of asbestos fibers into the pent.or.eun, rhere there is also a degree of nobility, but not in other eortrapulncrary organs. * ,, L_r____. _ _ o The experimental investigation with !st-eatC3 numerals was rornemac pruraril, with the effect of the dust on ncrral tissue but sera attention was given to other phases, such as susceptibility to infection and occurrence of nalignar.cy. 2?. Infection. The only experiment in which the effect of inhaled asbestos oust ;n a ril- JO. Susceptibility to Tuberculous Infection. The darelopnant of a tuber culous process initiated at the beginning of exposure to asbestos dust, and also of an infection superimposed upon an established asbostosic, was described ia Sections 1? and 20 of this re port. It -will be noted that asbestos, whan classified according to the effect of a dust on tuberculous infection, norId be placed beio-- an actire dust ~HWn quartz but abore inert dusts, such as calcite and gypsum. In animals infected with attenuated tubercle bacilli, quarts will cause the infectious process to progress until the animal dies of tuberculosis. Inert custs Trill hare no effect on the infection and the lesions will usually heal and the disease disappear. Asbestos dust is in a different category* f^hen the fibrous dust wa3 being in haled during the evolution of the infection, there was a spreading of the tuber culous process for a' oina but usually the stimulus fer continued proliferation cf the tubercle bacilli was not sustained, the progression ras arrested and healing followed. In guinea pigs infected with attenuated tubercle bacilli following the completion of nearly three years of exposure to asbestos dust, progressive disease did not develop. The only nodificaticn of the infection was one of localisation, a fr bacilli being retained in the fibre'is terminal bronchioles and forming tubarclae there in addition to the usual foci beneath the pleura. Such tubercles healed in a few months and there was nothing to suggest any influence on the course of the disease. JL. Susceptibility to hon-Tnberrulcns Infection. There was no pointed ax- effect of inhaled asbestos dust on non--tuberculous infection. Inter current pneu monia among an 1.oval s exposed to asbestos oust wus rather ccnxncn, the frequency in guinea pig3 exuosed ia the fo'*- nhalation exuerinents ranging froa 16 to 35 per cent. This incidental evidence suggests the possibility of an effect of asbestos exist on non-tuberculcus infection. Nevertheless, since such epidend.es 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 dees net exert a significant effect on the susceptibility to non-tuberculous pulmonary infection. 92. NeooLassi. No specific experiment was conducted to determine whether the inhalation of asbestos favors the development of neoplastic disease but certain observations on this subject were recorded in the outline of the proposed aenneraph on asbestosis submittad by the late Dr. 1. 1. Gardner in February 19li3. In iv he tailed atten tion to the high incidence of lung cancer among mica inhaling I:tg-fibsr asbestos. In his experimental notes, hcvsver, he referred to these lesions is adenomas. There is an imeortar.t distinction between adenoma and cancer itch should c-a mace clear. A cancer is a tumor, or neoclasm, capable of local Lncsttn and de struction of tissue, which can distribute cells through, the lymphno.cs :r blood stream to produce isolated foci, from which new tumors here Ire. lit; -_t.cncr-c-n:n of dim semination is Irniown as oKtastasis and any tumor which exhibits it is a malignant growth, of which cancer is one type. An adenoma, cn tne : tar r.and, 13 a so--oallod benign or non-callgrant tumor (neoplasm) which may or mi r r.ct be capable of local invasion but which does not metastasise. In order to clarify the exact nature of these Lesters the path 'logical mater ial is being carefully examined. Gince it is felt desirable to is-- the tenet it pcr.ed until alter his return iron furore. lather tear, telrr the err. r? report, further discussion will be reserved for a suupleme.nt to be tented lat . . _',o_ Trisg to the vast cr.z-z'.t : i it.tr. included in this report :'.t seems cast convenient to state tie ucr.clusior.t derived fres the investigation and. Then r.-ecossarv, foiler each or.'-. .rath a 'or~s reruns of the evidence. i. "arsons forms of. csbeotcs fibers produce a peribronchiolar fibrosis lungs of guinea pigs, rots, cats ana rabbits bat not of mice and dogs. Both inhsiaticr "-si injection u-rmrcdunsivts provide ample rapport for this conclusion. Tit ires t autd show the reaction to tvo different hinut- of asbestos mineral. 5. The node of actios appears to bo nvirarilp mechanical rather titan chemical in nature. 7se evider.ee is given in section IXTT7IT. Figures 1, 2, 3, u and illustrate -ha orient points - The fibrous filanenid irritating action. nr.ee tre solid fibers cl" glass rod do sat produce fibrosis .so-t TL-_r = f. Tirort asbestos fliers :o sot produce fibrosis. The conclusion is ir.riu.od is ibo tridenoe mentioned in saragreph 3 aoove. Freerizests *hich further support thi3 findiru. are reported it Tar is s fl r.r.d 2;. Tr-pical fibrosis cm bo produced cr an atmospheric suspension of asbestos dust csssc-ir.ir.c mlp m. -vttro.seIp small properties of long fibers. asbestos dust _ tjsnoal, trough delupod, fibrosis rras obtained see.- riel- 12). altiio-jrh ioc? -rr :r'- ._* the cuaoaphsric dust, consisted of fiber? lon-rer th.s;u 11 microns, ss is shown in 'ir-bis H. I;; ccslrsjA, the- intra- tracresl injection irgeciusnt rd.tr. fire cbb.-v.ss oust :or.- tainir-u nc long fibers failed to product fibrosis, (see Table 21). Ini-.alati.cn of asbestos riuat apparent1/ does not altar significantly l.-.s course of experimental tuberculosis in guinea piss. This conclusicn is tentative since the evid-ancs or. which it is based does not conform with cur usual experience, lafar- er.ee to Table 5 will shew that Then infection eras coincident with onset of dust exposure there tts.3 tenporary pro--??ricr. of the disease with subsequent healing; when infection was initiated after 2o 3 A norths of dust exposure the course f.-.e tuberculous disease rus not appreciably altered. In contrast, at has been ooserred in experiments wit-, rinse ousts cor.uuurto: quartz that if there is a slight progression of the tuberr-- losis when infection ar.d dust eoeposure are coincident, trie effect is tore narked ) instead of les3, -is wn.th asbestos v.r-r. infection is initiated after a neriod of dust exposure. This ccuclusio:' concerning the effect of inhaled asbesio'dust on tuberculosis seers justified because in the rors s = mtice test ^infection initiated after a roariod of dust exposure. -rsvsr, since the findings in fra dm with previo;i3 experience, ar.d -lil- Lurv- '.er i" r,hr. iTc-TO rr.d :-ov:T.t3 in j.oss or '>;= fibill'jj ;.o rrc.'.oc' ir.;'':cn.on o.` nsba jtc-s:\3 oodior f .il "-'co ics t..ie ^rpioai tioouo ro.'.c nor. (323 scc-ior. ) Tin Torsiti"/!'. or ;o:.> .0 iri'.ai.'.d ssbcti.os dvoi ;:o--n oi'ton o'.oo:v.-a toninatcs ns-r nr 0: