Document 2qLBq3XEgwzJxBDex4VxnDMe7

PLAINTIFF'S EXHIBIT Reprinted from the .(. S( A. Archives of Industrial Hii'.th September J95_\ Voi 12. pp. 34S-360 Copyright 7955. iy American Medical Association (Cffect of Onlialed (Commercial^Jdydroua (Calcium (Silicate Cbudt on minimal CJi indues Aa CiawiBMttl SMy S. W. H. SCHEMES. M.D., D St. T. M. DUIKAN, M.t. ad A. I. MLAHANT, Seraaee Lake, N. T. .. j.ii--arim in liajagg:;,rr--<aHiaJCAAa..ii--^ *.. mmM Commercial hydrous calcit^n silicate is one of the products that have be-, 'tudied by long-term inhalation exp. intents at The Saranac Laboratory. These studies were commenced in 1943 under the direction of Dr. L. U. Gardner and with the assistance of two of us (T. M. D. and A. B. D.) who car ried the work to its completion after Dr. Gardner's death. Guinea pigs, rats, and ham sters were used, and the experiments were designed to reveal the nature of the pulmo nary tissue reaction to inhaled dust of the material in normal animals and in those har boring an experimentally induced tuberculous infection. From experience with other siliceous materials one would expect to find that a product composed only of calcium silicate would be relatively inert in its effect on tissue. Extensive clinical studies of industrial workers exposed to cement dust in high concentration have, for instance, shown that the effect of the inhaled dust of that material on the lungs is insignificant. Portland cement is composed principally of two calcium sili cates, namely, dicalcium silicate and tri calcium silicate. Recognition must be given, however, to the possibility that any poten Recorded for publication July IS, 1955. Director, (Dr. Schepers), Associate Director (Mr. Durkan), and Research Associate (Mr. Delahant). The Saranac Laboratory. tially hazardous raw materials used to make a product might not be entirely converted to a nonhazardous form during the manu facturing process and. therefore, might appear to a greater or less extent in an unchanged condition in the final product. The clay and shale used in making cement often have a quartz content of 20% to 30% or more, but chemical reactions, occurring when the raw mixture is heated, convert practically all the hazardous free-silica min eral to a relatively harmless silicate. In most samples of cement the amount of quartz that has come through the manufacturing process unchanged is less than 0.1%. The hydrous calcium silicate product used in The Saranac Laboratory studies was made irom calcium hydroxide and silica plus a moderate amount of asbestos, which was incorporated in the mixture to impart cer tain desirable physical properties to the fin ished product. Analysis of one sample of this finished product disclosed that approximately 80% of the raw mixture had been converted to hydrous calcium silicate and that about 15% was magnesium silicate (Table 1) About 1% quartz persisted in the final prod uct. Probably the greater part of the mag nesium silicate was present as the fibrou; mineral chrysotile. although a portion ma; have been in the form of serpentine, a min era! similar to chrysotile in chemical compo sition but one which is nonfibrous. EXPERIMENTAL METHOD To determine the effect of inhaled dust of th product on pulmonary tissue, an inhalation exper ment was conducted. In that experiment group of guinea pigs, rats, and hamsters were expose in a cubical dust room. 8 ft. in dimension, in whir 01 022 0610 TaOLE 1--Composition of Commercial Hydrous Calcium Siiicut Componeot Aaalysii SlOt ............. PiOe. AJiOi. TIOt...................... C0 .................................................... U(0 ................................... NaaO. KiO .................................... IfDItlOO loea................................. Total................. :........ Percent 3 31 3 31 31 19" TTl ConpOUAd Aa*l?U Urdrous etietun illicit* Cilclua cirfcooiti.................... tttf&ctlua illicit* ... Tottl................................. Per Ccot Asorox i * IS ; an atmospheric suspension of the hydrous calcium silicate product was created by the action of a paddle which rotated inside a hopper containing the material in finely divided form. The dust cloud generated in this manner floated out into the room where it was maintained for eight hours on five days of the week and for four hours on Saturday >. Some of the animals were exposed to the dust for periods as long as three years. At regular intervals during the experiment a few animals, were killed, and the organs examined grossly./ and micro scopically to determine the nature and the extent of the tissue reaction to the calcium silicate product. The tissue was also analyted chemically to estimate the amount of the inhaled dust that was retained in the lungs of animals exposed for definite periods of time. Only guinea pigs were used in the studies dealing with infected animals. The Ri low-virulence strain of the tubercle bacilli was introduced intratracheally by means of the insufflation technique. Dust counts of atmospheric samples collected in the dust room were made regularly by means of the midget impinger. The concentration of the hydrous calcium silicate aerosol to which the uninfected animals were exposed was generally within the range of 100.000,000 to 125.000.000 particles per cubic foot of air by light-held count, and the over all average was 115,000,000. In the studies on in fected animals the concentration was higher, the average being 205.000,000. EXPOSURE OF UNINFECTED ANIMALS Three species--guinea pig. rat. and ham ster--were employed in this phase ot the investigation. Summaries ot the findings are given in Tables 2, 3, and 4. Attention should first be drawn to the relatively high mortality rate reflected in Table 2. That these deaths were due to intercurrent epizootic inieciion was almost certain in the case ot the guinea pigs and is emphasized the more torceiully by the fact that the animals died not only of pneumonia but also of pericarditis, peri tonitis, and cervical adenitis with abscess formation. That all the hamsters which died did so within the first year may also have some bearing on the question. In the case of the rats, on the contrary, no animals died within the first year, and the rate at which animals succumbed increased with the pas sage of time. In view of the progressive nature of the pulmonary disease which en sued as a result of the exposure to the dust of the hydrous calcium silicate product, there is some presumptive evidence that the deaths and dust exposures bore some relation to each other in this instance. Taile 2.--Biological Action of Commercial Hydrous Calcium Silicate Dust Guinea Pigj. Hamsters, and Rati Were Expoied by Inhalation to an Aerosol oi Commercial Hydrous Calcium Silicate Dust Until Death Record of Animals. Exposed to the Dust Alone. Which Died Spontaneously Cause ol Death Species Guinea Plf....................... Hatnatar.......................... Ret......................................... Pneumonia Par So. Cent SI* *0.9 to* 30.0 JOt 50.0 Pericarditis Par So. Caot :M Perltooltla Ptt No, ClAt tt 9.4 Cervical Adeoltte Per No. Cent S 1i Total Per No. Croc T3 US 121 600 70 ( * Id.5% died wlthlb first rear ol experiment. * 100 0% died witbln first rear ol experiment. : 0 0% died wlthlb first year o( expanmeet. I Two deaths from otber causee. 01 022 0611 ` I t i- *| | :tiu||.i4j |U4|(l|4t>i jo man* *| ^haj 4 The three species of experimental animals reacted somewhat differently to the dust, though the difference was more one of degree than of quality. The most marked lesions were provoked in the guinea pigs, but this was probably largely due to the fact that dusting was carried on for a total of 36 months in the case of this species, while the procedure was terminated at the end of the 18th month in the case of the rats and hamsters. When cognizance is taken of this fact, it appears that, stage for stage, the latter two animal groups actually suffered greater pulmonary damage sooner than did the guinea pigs. This difference is brought out by a compari son of Tables 3 and 4, in the construction of which the same scales of values were used. Pigmentation of the pulmonary tissue or of pulmonary lymph nodes never became prominent features in these anirpals. It in creased diffusely as a light brown discolora tion which was most marked along the anterior margins of the lungs in the guinea pigs. As it became macroscopically detectable at the 12th month of exposure only, its absence in the case of the rats or hamsters before the 18th month may have no true significance. It would seem that the pigment was almost entirely due to hemosiderin, as shown by Prussian blue staining. Pigmented koniophores and giant cells became a promi nent feature toward the terminal phase of the experiment on guinea pigs, and clusters of such cells could even be found in rat lungs where they were grouped around the smaller blood vessels. Lymphoid hyperplasia was a prominent and persistent feature of the reaction in the guinea pigs. There was mild hyperplasia about the main bronchi in some of the rats, but this was not an impressive observation for this species. No lymphoid hyperplasia was seen in the hamsters. The hyperplasia consisted almost entirely of lymphoid cell proliferation without any evidence of central macrophage accumulation such as may occur as a result of exposure to certain amorphous siliceous dusts. Mostly the lymph deposits remained spherical in shape and were thus well defined from sur rounding structures. Occasionally, however, there was some lymphoid invasion of the walls of adjacent alveoli. At a later stage macrophages tended to accumulate around these lymph foci. In spite of this tendency toward intrapulmonary lymphoid hyperplasia, the pulmo nary lymph nodes showed no consistent corresponding change. In some of the an imals there was early lymphoid hyperplasia, but in the majority the nodes enlarged slightly or moderately only at the start. After the animals had been in the dust atmosphere for two years, the nodes became more con sistently enlarged, and in the instances in which this occurred the cause was almost always infiltration of the medullary zones by macrophages, which no doubt migrated thence from the pulmonary tissues. The cor tical follicles did not enlarge and often showed signs of atrophy. In both the rats and hamsters the reaction in the pulmonary lymph nodes was even less marked. Undoubtedly the most prominent lesion discovered in this series of animals was pres ent as chronic bronchiolitis and bronchial ulceration, with emphasis on the former. The disease was progressive in nature and de structive in its effects, although the tendency to epithelial desquamation, so characteristic of the reaction to quartz dust, was not present. The bronchiolar lesions commenced early in the guinea pigs and hamsters but were delayed in the rats. In neither of the latter groups were the severe grades of obliterative bronchiolitis or bronchiolitis deformans, which characterized the guinea pig response, observed. In the rat the stress was rather on bronchiolar ulceration and peribronchi olitis. As the dusting proceeded beyond the first year of experiment, the inflammatory re action in the bronchioles gave way to pro gressive distention and distortion. This change was brought into sharp focus by the increasing cellular deposits around the air passages. Toward the end of the second year the crenated outlines of the bronchiolar lumina were thrown into sharp relief by a 01 022 0613 marked tendency to peribronchiolar atelec tasis, with epithelialization of the walls of the shrinking alveoli and cellular infiltration among these minute cystic spaces. This change produced a microscopic sectional effect resembling multiple adenomatosis, but as there is no lack of differentiation of the cellular components, no neoplastic change could be postulated. This adenomatoid pat tern was seen only in the guinea pigs, but as its evolution was in the nature of a Re layed phenomenon, it is possible that it would also have appeared in the rats and hamsters had exposure been continued in their cases beyond the 18th month. Phagocvtosis of the inhaled dust could be demonstrated in all animals from the com mencement of the experiment. It was most marked in the case of the guinea pigs and least prominent as a feature iij the case of the hamsters. The phagocytes were domi nantly mononuclear macrophages until about the end of the first year of the exposure when multinudeated giant cells commenced to be substituted in progressively greater numbers. At the same time these giant cells grew in size so that they often filled the alveoli completely, and toward the end of the third year of exposure the giant cells replaced the mononuclear cells almost completely, especially around the distorted bronchioles. As time passed, their cytoplasm became in creasingly more acidophilic and their centers more charged with ingested particles. There was no evidence of necrosis of these cells, such as occurs in experiments with finely divided quartz dust and silica fume, which provoke similar giant cells. Interstitial cellular proliferation and infil tration are a late sign in all three species. It commences first toward the end of the ninth month of exposure, and for the suc ceeding six months it is almost entirely lim ited to macrophage accumulations around smaller blood vessels and bronchioles, at the angles between adjacent alveoli, and in the interlobular septa. Among these macrophages may be found isolated eosinophiles and plasmacytes. Fibrocytes first make an appearance between the 15th and the 18th month of dust inhalation, and soon after this strands of collagen may be perceived among the cells Fibrosis proceeds slowly, however, before the end of the 30th month of dust exposure. Thereafter it is detectable in increasing amounts, particularly in relation to the ade nomatoid areas around the bronchioles. Fibrosis also appears prominently in local areas of consolidation, which become pro gressively commoner toward the end of the third year of exposure. In animals killed, respectively, at 33 and 36 months from the start of the dusting, extensive areas of lobu lar consolidation could be found, and similar consolidation associated with cystic disten tion of trapped bronchi could be seen in sev eral of the rats killed at the 15- and 18-month periods. No acute inflammatory process was demonstrable to account for these results. Asbestos bodies of an elongated, slender, tapering, minute variety were demonstable by oil-immersion microscopy from about the 15th month onward in rats and hamsters and from the 18th month onward in the guinea pig. Occasionally opaque clubbed bodies could be found, but in most instances the bodies were difficult to bring into focus and tended to be curved and spindle-shaped. Often they were intracellular, being partly engulfed by one or more macrophages. None were found lying free within alveoli. They were so constantly found in association with the areas of fibrosis that the conclusion of a causal relationship between these phenomena is almost inescapable. Emphysema of the hypertrophic variety appeared as an early sign in the hamsters, in which it was present to a quite marked and widely distributed degree at the end of the 18 months of dust exposure. In the rats the lesions were also consistently present from an early stage but to a lower degree than in the hamsters. In the guinea pigs, on the contrary, hypertrophic emphysema was contrastingly absent during the first two years of the experiment. In the final 12 months, compensatory emphysema was man ifested as a prominent lesion silhouetted against the foci of cellular proliferation and peribronchiolar atelectasis. 01 022 0611 6 L'niike in many other dust experiments, there was no marked tendency toward subpleural congregation ot the hydrous calcium silicate dust. Consequently the reaction at this site was minimal and delayed. The most conspicuous changes occurred in the rats where there were occasional subpleural cellu lar condensations and a recurrent tendency to the formation of interlobular adhesions. In some of the guinea pigs which outlasted three years of exposure to the dust, foci of subpleural cellular proliferation attended by giant-cell accumulation were demonstrable. The relatively marked macrophage infil tration of the pulmonary lymph nodes con trasted sharply with the paucity of giant cells among them, with the minimal amount of interstitial fibrosis which ensued, and with the absence of asbestos bodies. Periadenitis of a mild degree became a insistent finding in a majority of animals beyond the end of the first year of dust inhalation. Deposition of fibrous strands around the lymph nodes followed successive phases of afferent lym phangiectasia and macrophage transportation along these channels, with littoral arrest of increasing numbers of these cells. The lack of fibrosis, except at sites where asbestos bodies occur with greatest preva lence, is indeed remarkable, the more so when regard is had to the dense cellular in filtrations which ultimately ensue. One is led to the conclusion, therefore, that the hydrous calcium silicate dust alone, except for its chrysotile component, is nonfibrogenic though it provokes a cellular reaction. EXPOSURE OF TUBERCULOUS ANIMALS There are three types, or phases, of in vestigation that have been found invaluable for studying the effect of inhaled dust on the course of experimentally induced tuberculosis in animals. These three types of experiment are sometimes called the simultaneous phase, the reactivation phase, and the predisposi tion phase. In the simultaneous phase, nor mal animals are infected with attenuated tubercle bacilli of the Ri strain by an inhala tion method and then are immediately transferred to the dust room. Thus the tuber culous disease and the tissue reaction to the inhaled dust will develop simultaneously In the reactivation-phase experiment, the animals, after being infected with the tubercle bacilli, are allowed to live in a normal at mosphere for several months before being exposed to dust. During this period the tuberculous lesions generally regress, and in some instances complete healing by reso lution may take place. Following this inter val, the exposure of the animals to some dusts has no significant effect on the usual course of the tuberculous process, and the lesions continue to regress, while exposure to other dusts may cause the tuberculous process to become active and to spread. A predisposition-phase experiment is one in which animals are exposed to dust for several months, are then iniected with the tubercle bacilli, and are immediately returned to the dust room where their exposure to dust is continued. In this phase the effect of a pre vious dust exposure on the early course of a tuberculous process can be studied. Simultaneous Phase : Reaction in Guinea Pics Infected with Tusexcle Bacilli at Onset or Dust Inhalation In the first experiment in which animals were infected with tubercle bacilli at the time that their exposure to the dust was started. 25 guinea pigs were used, but an epidemic of pneumonia during the first 10 months re duced to 16 the number of animals available for study. Two of these died at fourteen months, apparently from progressive tubercu losis, and two others died from undetermined causes but not from tuberculosis. In the re maining 12 animals the course of the tubercu lous disease was followed by killing 1 or 2 animals at 1, 6, 9, 12, 15. 18, and 24 months after infection. In 9 of the 25 animals the le sions were multiple, isolated, and healed, often with central calcification. In six of the remaining animals the lesions were still circumscribed but showed neither a tendency to heal nor to spread even at the end of 18 months. In six other animals there was a moderate tendency to local spread of the tuberculous process, while in the remaining 01 022 0615 Tisle Causes of Death m Guinea Pigs Exposed by Inhalation to Comuur;uti Hydrous Calcium Silicate Dust and Also Infected utrfc Tubercle Bacilli of the Rt Strain Type of Eipenmeot SlBUltAOMUA pBAM....... RaACUTACIOO pP AM ........ Predtepoeicloo pBM............ Coatrol. Group A........ Group B ........ pBftunoAii AONlBoA.lA. D*Na(oB. 30 * S9 : 30 i 3* 4 IS 3 CPeeort SI so SI it. r 1*0 Caum of Diata_____ _______ PeritArdlua fthtoaiuA OtMrC*viM Toiaj oAta. No. Ceot DeNaota. e. CPAeOrt OANAotb. A. CPeBrl No.DaacBa, CPAeOrt 3 10.0 1 1.1 i SO U *4 4 1 40 l 4.0 4 16 0 9 me iI 40 0 i :i r 9 u0 animal, which was killed at 15 months, the lesions were widespread throughout the lung but nbrosis had been produced. In an at tempt to develop a strain of guinea pig re sistant to the infection that had caused the pneumonia, some of the animals were used for breeding during this experiment. The two animals that died from progressive tu berculosis (at U months) and the single animal (killed at 15 months) that exhibited widespread lesions were all used as breeders during the experiment, as were also tour other animals in the experiment, which had failed to show extensive disease. Owing to the element of uncertainty introduced by this factor of breeding, and also because of the high mortality from pneumonia and to verify the suggestive evidence of stimulating action of the inhaled dust upon tuberculosis, the experiment was repeated. Table 6,--Course of Tuberculosis Induced m Guinea Pigs by Infection with Tubercle Bacilli of the R\ Strain Control Study: Infection Only; No Dust Exposure Surrlrii After GutOAA iDfACtlOB. Plf. No. Dayi a. ST ...... 6500 120 S3 64 IK 73. ..... 196 *7 * M. . ... 61 ..... S3. ...... * 2SJ 300 315 6? ...... 6700 n 430 ?T6S ...... 77 71 7SO1 n 6M6 SI 540 fit* DM KKiilltteedd Kilted Kilted KKiilltteedd Did DM K11M Kilted DM KKiilltteedd DM KKUiltMed KKiilltteedd KKiilltteedd KKiIl1teMd Kilted KJUed Kilted KK1il1MM KKKiiilltlMeMd KKiUlteMd KilM PuiaoetiT T--low RtictLiormo pLaaMNoadoMoirr TAurbreertetteede. STpurbeeardeiun*g Cam** NO. lOAll Boa Cotelft* CAtioo T\j&rtte XXsMmiaAdoa PleurltU CalArve* meat Forma* LlTtr Spleen s TT---- TT--* 4~f 4-4- +4- 0 Symbole: 4-. iliiBt rteetioa; 4-+, moderate reoetioa; I | |, tdraoMd naetloa; T, toberete formation. 01 022 0616 6 Table 7.--Influence of InJialed Commercial Hydrous Calcium Silicate Cust oh :he Course of Experimentally Induced Tuberculosis m Guinea Pigs simultaneous Phase Animals Received Their Tuberculous Infection and Started Thetr Period of Dust Exposure Simultaneously Exposure ;u.oA to Dust, P!f, So. Dam 1 *0 l 00 z 00 4 111 1 130 } 130 34 tat 2i 100 to IT* r 100 i 110 30 m 14 304 22 zx 0 240 13 240 .1 35* It 300 11 300 t7 415 30 430 ti 400 l 430 17 517 n 500 H 000 21 000 10 730 23 730 2* no riu DM Kilted DM DM Kilted Kilted DM DM DM Kilted Kilted DM DM DM Kilted Kilted DM Kilted Kilted Olid DM Kilted Kitted DM DM DM DM Kilted Kitted Kilted PulSOflirr LmJou uretud Tuoemee. So. i *4 10 1 i 3 Tuber- ' CUIO0I0 Cavitation Pteuntla r + yy ----+ +-r -r-- 7+ l fri. *i T---- Diueautuoa PoUnooAry KoIatt** <aat yy cutout _ -- 44. 4. 4*. y+ _ --4 4. y Liver Nt 4.-4. 7T 5 + / ++-T TT f 4 -- -4- -- 4.4. 4. -- -- 4.. 4. T-rT-r 3 5 4--h 4 -H- m t>r ++ -M- -H- 4--fc44-4. 4.4. 4-4. 4. 4. -- y S*4a r-4 FF^ T -- CUlOSAtrAt.oboU: t, lUfbt r*Action; modmt* reaction; -H-. marked reaction; F. Ibrous: N, oecroiti; T. tuber- When conducted a second time, 30 guinea bacilli was used but the animals were not pigs, instead of 25, were used in this simul exposed to dust. taneous infection experiment. The animals As may be seen in Table 5, the mortality were killed in pairs for study at 2, 4, 6, 8, 12, rate among the control group was but \\.7% * 15, and 24 months after infection. Again the as against the high rate of 46.6% found in incidence of pneumonia was unusually high, the animals which were caused to inhale six of the animals dying from that cause dur ing the first 8 months of exposure and two more during the following 16 months. An additional three died of pericarditis, one of peritonitis, and two more of other causes (Table 5). This left a balance of 16 animals which were killed as planned. The results are assembled in Table 7 dust. As these experiments were conducted simultaneously and in the same laboratory, except that the animals receiving dust ex posure were even better protected from out side contacts, the different death rates may have some significance after all. The numbers of tubercles which developed in the control series did not differ materially from those which were discovered in the which should be compared with the control animals exposed to dust alter infection. In study recorded in Table 6, in connection with one control animal there was a marked which the same culture batch of tubercle spread which caused the death of the guinea 01 022 0617 pig. Massive caseating lesions were t'ound in the lungs, the liver, and the spleen. It was suspected that this animal may have been accidentally infected with virulent human tubercle bacilli. Consequently, bacilli were recovered, cultured, and subinoculated into the groins of four healthy guinea pigs. These animals developed local abortive lesions char acteristic of the Ri bacillus, and no systemic tuberculosis ensued. By this study it was fairly satisfactorily demonstrated that Guinea Pig 73 was unduly susceptible to tubercuibsis. In the guinea pigs which were caused to breathe the hydrous calcium silicate dust after infection, localized spreads of the tu berculosis occurred in 13 out of the 30 cases. In four of these the tuberculous process was quite advanced, and in four others it was moderately marked at the time of autopsy. It should be noted too that rfse of these spreads occurred during the second year of the experiment, i. e., long after the tubercles should have been arrested and healed. At tention should also be drawn to the presence of cavitation within two tuberculous pneu monic areas in Guinea Pig 25. Pleural adhesions of a chronic tough va riety were also quite common in the animals receiving the dust exposure. The pulmonary lymph nodes showed a greater prevalence of late active tuberculous foci, such lesions in the control animals having usually disap peared from the nodes before the end of the first year. From this simultaneous phase experiment it would seem, therefore, that the hydrous calcium silicate had a mild to moderately ad verse effect on the course of the R, tubercle infection. Reactivation Phase: Cocuse or Tuieecuujms in Guinia Pics Which Wiu Exrosro to Hydrous Calcium Silicate Dust Sevieal Months Aetie iNncriON with R, Tuieiclx Bacilli Infected guinea pigs were placed in the dust chambers at intervals of two months, i. e., 10 at two months, 8 at four months, and 8 more at six months after infection. In order to follow the course of the tissue reac tion, a pair of animals oi the rirat subgroup (two months in normal air} was killed aiter only 2 months of dust exposure, and, m ad dition, animals from ail groups were killed in pairs after 4, 8. and 12 months of exposure to the dust. Examination of the tissue of the dusted animals failed to reveal a significant reactivation oi the tuberculous disease by the inhaled dust (.Table S). Only live animals show-ed evidence of spreading pulmonary tu berculosis. In three the disease was minimal in extent, and in two others there was moderately extensive local spread. Casea tion persisted in one animal to the end of a year, and slight to moderate foci of fibrosis could be discerned in a few animals, suggest ing that not all the tubercles healed by resolu tion. Chronic pleuritis and pleural adhesions were present in 10 of the guinea pigs, which was considerably in excess oi what is cus tomarily found in a typical reaction to the introduction of Ri tubercle bacilli. Dissemin ation of the tuberculous process to abdominal organs and to the pulmonary lymph nodes did not occur in any but exceptional cases. Guinea Pig 52 was probably one of these "spons." The term "sport" is given to a guinea pig in which the inhalation infection with the attenuated bacilli is not confined principally to the lungs and pulmonarylymph nodes but extends also to other organs and produces in them tuberculous changes of sufficient extent to be recognized macroscopically. Since "sports" represent a de parture from the normal pattern of tissue reaction to attenuated tubercle bacilli, whether the infection is combined with dust exposure or not, such animals must be ex cluded in assaying the effect of an inhaled dust upon a tuberculous infection. It is be lieved that "sports" are animals whose na tive resistance to the attenuated Ri organ ism is unusually low. Support for this beliet is given by experience with quartz dust, a definitely hazardous material which reacti vates an inhalation infection produced by attenuated Rt bacilli but ordinarily is not as sociated with tuberculous extension to organs other than the lungs and pulmonary lymph nodes. 01 022 0618 10 TaJLC 8.--Influence of (nkaied Commercial Hydrous Calcium Silicate Cusi jm the . -"'.v j; Experimentally Induced Tubercuionj in Guinea Pigs Reactivation Phase Animali, After Reeeivinj Their Tuberculous Infection Were Allowed to Live in a Normal Environment for a Period of Two to Six Months Before They Were Exposed to Oust Pulaassrr Letiou Etpoturt (juioaa to Ouai. PIC. No. Dim rtta Spread. Armtad Totorttei. Tutor* No. tfuKMti Caaaa. uoa fibroala Pteumia Eipoaur* to Dutt Wu ftunrt Too Hoatto Altar lateetioa ? * Dted 3 -- *r u Dted H 40 DM 3 n 40 IIM *- + ,, + s 40 Kilted 1 is 130 Kilted 3 36 130 Kilted 3? 340 Kilted 4 ? 4* 31 340 KUted 3 33 m KUted 3 346 Kilted 19 -- .* ** 40 344 Eipoiurt to Duat Kilted 9 ---- Starred Four tfootiu A fur (ofaetioo ii 130 Kilted * 4-4- 44 130 Kilted 41 340 KUted T 4 43 340 Kilted a 349 KUted 44 314 KUted i j rtf Etpoiut* to Dut Waa Startad Six Xoatto After tofacUoo (t 117 ZMad 4 SO 130 KUted 3 r 4- 4*+ S3 ISO KUted 7 f S3 340 EQM 1 H-- 14 340 KUted 9 36 346 KUted 34 344 KUted i + *H" OtSMOmtt:OS rtlaoBin Irmoo >odc EoJart- Tutor- sadc CUlOtif L-rar -- r- -- ---- -- -- ---- -- -- fr ------- - 4. -W- - -t-4* 4* -- >4 *r4- +~r- -H- JrmtoU: f, Slliht; +-r. medenta: i i t. sdTtased; T. tubMmJoW*. Spteatt t-N T-+ PxEotsrosiTtoN Phase : Reaction in Guinea Ptcs Infected with Tueeecle Bacilli Thiie Months Amt Theie Exfosuee to Dust Was Staetxs An experiment of this type is a severe test, because a dust that is only very slightly toxic may produce tissue changes which, though minor in character, may be sufficient to alter profoundly the development of a fresh tuberculous infection. In this experi ment, which was designed to study the ef fect of the dust accumulated in the lung upon a newly developing tuberculous disease, 30 guinea pigs were exposed to the dust for three months and then were infected with at tenuated tubercle bacilli. The dust exposure was immediately resumed and carried on for another 21 months. The over-all death rate in this series of animals was relatively low (Table 5). It may be of some significance that the majority of the eight animals that died from pneumonia did so during the latter half of the dusting phase. It is also significant perhaps that local and diffuse spreads of the tuberculous process had occurred most commonly in these animals prior to their terminal fatal illness. The prevalence of such spreads in this series of guinea pigs does indeed appear to be significant (Table 9). Six animals showed marked local or diffuse extension of the dis ease, and in seven more this spread was of moderate severity. In an additional 9 cases there was slight spread of the process, so that a total of 22 animals reacted unfavorably. Cavitation occurred in 2 instances, and pleural extension in 10 of the 30 guinea pigs. One animal died from a pneumonic tubercu lous process. 01 022 0619 11 Tails 9--Induence of Inhaled Commercial Hydrous Calcium Silicate Oust -n the Course or Experimentally Induced Tubernlosu < Guinea Pigs Predisposition Phase: Animals, Alter Being Exposed to the Dust for Three Months. Were Injected *ith Tubercle Bacilli ot the R, strain and Then Were Immediately Returned to the Dust Room Where Their Dust Exposure Was Continued L'ntil Death Eipoeure to Dual After ''UiOftft lofettioo. Pic. No. Dor* 107 0 i0 90 10 0 11 0 u * 40 n 40 * 120 iio f7 110 114 210 104 230 U1 240 m :o n 300 104 300 m 344 99 366 too 364 119 +06 117 04 ICS 440 101 66 lift OO 120 oo 101 630 102 630 lift 430 FftU KUM Killed Kilted Kilted Kilted Dted Kilted Kilted Killed Killed Kilted Dted Dted Kilted Kilted Killed Kilted Died Kilted Killed Died Dted Dted Dted Kilted Kilted Killed Kilted Kilted PuixDoatr? Leeioac lfiie(eu A Tuberuee. Tuber- No. cuioete Cftelte* UOft PtourUU OieeemiaeiMa Puiaodbry Eatert* Tuber- seat nuoesi Liver SiMB 4 IT :t -- \6 14 r r ---- n -r ti ---- 1 *-- 4 V +--r 3 -- * 4 -T**-- -H- +H-+ 4-+- T-- ---r + -- w---- -- --- -- ---- --.<* 4 -r-M- 4+ 3-- 3 ++ -Hf r ---- -- -- -- -- - -- -- -- -- -- * -- T-r Symbol*: -e. lUtOt or tuelpieut nactloa; -t--p. modeeasa nicttoa; s t"h. manad raactioa; T, cubaseuloata. It is of interest to note that the extension ot the disease was almost entirely confined to the pulmonary tissues, tuberculous ioci being detected in the spleen of one animal only. The reaction in the pulmonary lymph nodes was not of a significant nature or de gree. These findings indicate that a tuberculous infection which originates in guinea pigs several months after a prolonged exposure of the animals to dust of the hydrous calcium silicate product was initiated may be unfa vorably influenced by the inhaled dust. A separate control experiment was set up, us ing 25 guinea pigs, as the predispositionphase experiment was started at a later stage than the preceding studies so that a fresh Rt culture had to be employed. The results ob tained were so similar to those given in Table 6 that the latter may suffice for the purpose of this paper. ANALYSIS OF TISSUE OF EXPOSED ANIMALS Chemical analysis of lung tissue of unin fected guinea pigs that had inhaled the hy drous calcium sihcate dust for periods up to 36 months yielded the data reported in Table 10. It will be noted that as the period of ex posure became longer the values for the tis sue ash gradually increased, thus showing that mineral matter was accumulating in the lungs. There was a pronounced increase in the silica component up to about 30 months and then a slight decrease. This phenomenon is illusory, as it is due to the relatively rapid rate at which inorganic matter was deposited 01 022 Ob'20 12 in the lung at this stage when the tissue reac tion suddenly blossomed forth into the full blown disease process. Comparable results have been obtained in The Saranac Labora tory in inhalation experiments with other dusts. The total amount of silica which accumu lated in the lung was about a third of that which may be demonstrated in the pulmonary tissue of guinea pigs exposed to quartz dust for a comparable period. ( COMMENT The first point which may be considered is that the commercial hydrous calcium sili As the chrysotile dust is capable or pro voking hbrosis in guinea pigs, :t may also in the case of the present study have been the cause of the focal hbrogemc response, so that the hydrous calcium silicate component may have to be exonerated. It seems likelv that the giant-cell reaction was largely an effect provoked by the latter component. At tention should be directed to the lack of ob vious necrosis in these cells. In this respect the dust differs quite markedly from quartz dust and silica fume. Indeed, necrosis was seldom a feature in this experimentally in duced disease even in the presence of tuber culosis. It is possible, therefore, that al- Taile 10-- Analysis of the Lungs of Guinea Pigs Exposed to Commercial Hrdrous Calcium Silicate Dust Ptnod of Expoeur*. *0. j 4 6 4 10 i: ia ii u rt 30 33 36 Aib, Per Coat of Deeleetttd Luo* 4.96 4 *3 4.44 4 46 4.47 4.9! 1.66 3.16 4.at 1.96 3.57 554 5.47 Mloertl Compootota of Dtekvoted Luo* SIO.J PtrCfit 0.25 0.50 0 25 0 29 0 43 0.3* 0 7i 05* 063 0.64 1.11 0.71 0.66 CeO. Per Ceflt 0 07 006 006 0.12 0 14 0.15 0.10 0.17 0.13 0.15 0.14 0.12 0.14 MfO. Ptr Ctal 0.07 0.06 0.06 00* 0.1* 0.15 0.29 0.10 0.07 0.1T 0.06 0.19 0.16 XlMral Compooeau of Lais* ai* 9lO. Per Cent 4.51 466 3.5* 6.66 6.2T io.it 10.46 U.41 12.61 12.74 19.91 14.06 114* C*0. Per Cest 1.34 1 94 *54 23* 2.62 2.96 1.96 3.29 2.76 2.4* 2.41 2.56 2At MfO. Ptr Ctat 1.60 1.94 2.0* tio 3.66 1.16 LIS 1.74 1.46 6.41 0.9! 3 31 2.94 cate product, studied in the experiments just described, really provoked two underlying pathological processes ascribable, respec tively, to the calcium silicate and to the chrysotile components. The terminal syn drome of peribronchiolar atelectasis, fibrosis, and adenomatoid change was, in fact, of the same kind as that which has been repeatedly produced in The Saranac Laboratory by means of inhaled asbestos dust. The lesion of experimental asbestosis has somewhat more fibrosis to it and shows less of a cellular reaction and the giant cells seen in the pres ent case are less commonly observed. In character with the asbestos lesion is the ab sence, in the present experiments, of fibrosis of the pulmonary lymph nodes in which no asbestos bodies could be found either. though the hydrous calcium silicate dust stimulated the proliferation or local accumu lation of cells it did not kill these cells. This point is well illustrated in the case of the bronchial epithelium, which proliferated as part of the process of chronic bronchiolar in flammation but did not readily necrose or be come desquamated as in animals exposed to quartz dust. In many of the worst seeming adenomatoid or cystic lesions, the bronchial epithelium even retained its ciliated epithelial surface. The evolution of the adenomatoid reaction is dearly revealed to comprise cryptic dis tention of the bronchioles, secondary papil lomatous ingrowths into these distended lumina, and peripheral epithelialization of atelectatic alveoli. 01 022 0621 15 Why the alveolar ducts and bronchioles should have dilated at an early phase in the rats was not clearly revealed. No proximal obstruction could be displayed which could account for the distention on mechanical principles. Possibly the cause may be re lated to the tendency to peribronchiolar atelectasis. Perhaps a neurogenic mechanism was at the root of it all. To be true, the larger cystic distentions were usually found within areas of chronic diffuse consolida tion, and it is possible that in such instances the distention of the trapped air passages resulted mechanically from cicatricial' con traction. The origin of two types of emphysema which were discovered may have similar ex planations. While that which developed in the guinea pigs was definitely compensatory to the foci of atelectasis and fibrosis which it surrounded and the emphysema found in the rats and hamsters was of tfie hyper trophic variety, both may have had a com mon origin in the damage to the bronchioles. The mild to moderate tuberculogenic ef fect of the hydrous calcium silicate dust mani fested itself in local or even diffuse spreads, delayed healing, and dissemination to other organs. It is not yet possible at this stage to attribute this phenomenon definitely to either the chrvsotile or hydrous calcium silicate components. The fact that the tuberculous process did not persist in the pulmonary lymph nodes, whereas it was activated in the lungs, parallels the observation that only in the lungs were asbestos bodies found. It must be presumed that the hydrous calcium silicate dust was transported irom the lungs to the lymph nodes, to judge by macrophage accumulation at the latter sites, and it is probable that the dust was more densely con centrated in the lymph nodes than in the pul monary tissues. This suggests that the stimulation to perpetuation and spread at the tuberculous process may have derived from the chrvsotile fibers rather than from the hydrous calcium silicate. Such a con clusion naturally requires further confirma tion through experimental investigation. SCMMAll Inhalation studies have been conducted using a commercial product composed of hydrous calcium silicate and chrysotile on normal guinea pigs, rats, and hamsters and on guinea pigs infected with tubercle bacilli of the Rt strain. The dust caused marked chronic bronchio litis, with terminal peribronchiolar focal fibrosis, bronchiectasia. and epithelialization of atelectatic alveoli. The final lesions closely resembled those, jounH in_vp*rimntal aj. bestosis and included asbestos bodies. The course of experimentally induced tu berculosis was mildly to moderately ad versely affected by the prolonged inhalation of the dust. It seems likely that the chrysotile compo nent of the commercial product, rather than the hydrous calcium silicate, was the cause of the deleterious effects on the tissues of the experimental animals. Printed and Pubtifhed Mr L'mfed States of .4nt<neo Of 022 0622