Document bBdxYLw8JQdgL9NrjLxZwJb0O

^^0^S^S> .c^AN \^r' :X*S$>: Iff (T* * ^ ii j j j 539 9 Pulmonary Ferruginous Bodies ct Development in Response to Filamentous Dusts and a Method of Isolation and Concentration Paul Gross, MD; and Robert T. P. deTreville, MO. DSc, Pittsburgh; Leifis J, Cralley, PhD, Cincinnati; and J, W. G, Davis, PHD, Cambridge, England (I: itnr Formation of ferruginous bodies should not be confused with pathogenicity. Failure to un derstand this differentiation may result in the erroneous generalization that all fibrous dusts snare the ability of abestos to produce lung damage. Such materials as fibrous aluminum silicate, silicon carbide whiskers, cosmetic talc, and glass fibers produce ferruginous bodies experimentally which are indistinguishable from those produced by asbestos fibers. A method of isolation and concentration of fer ruginous bodies from lungs of animals- and humans is described. Ferruginous bodies from asbestos fibers are much more pleomorphic than has generally been described, casting further doubt on morphological distinctions used in the past in separating so-called as bestos bodies from- pseudoasbestos bodies. w,ORLDWIDE attention was refo cused on ferruginous bodies by the publirat'on of Thomson,1 who found this phenomenon in the lungs of more than 2r,'r of unselected autopsied-adult hospital patients in Capetown, South Africa. A rimilar percentage was noted in Miami,2 >3~ in Pittsburgh,3 and 48% in Mon treal.4 The higher percentages reported n. Pittsburgh and Montreal are possibly oerent in the more intensive searches rcepted for publication on Oct 17, 1967. ~'rom the Industrial Hygiene Foundation. Pitts-'Sh iDr, Gross and Dr. deTreville); the National ;er for Urban and Industrial Health (Dr. Cral' and the Department of Pathology, British -5'.osis P.esearch Council, University- of Cam* -te-, Cambridge. England (Dr. Davis), -"'tint requests to the Industrial Hygiene Foun- 4400 Fifth Ave, Pittsburgh 15213 >Dr, Gross). carried out in these cities. These bodies are similar to asbestos bodies, though the natures of the central fibers have not been identified. Asbestos bodies are golden-brown, ferro-coated formations found in the lungs of persons who have inhaled asbestos dust. They are generally described as sym metrical, segmented structures, usually with clubbed ends, 3u to 5u in diameter and 20|.i to 50u long. The core is composed of a transparent colorless asbestos fiber that is not always demonstrable. Apparently the only difference between an asbestos body and a pseudoasbestos body is that in the former, the central fi ber is composed of asbestos, and in the latter, of material other than asbestos. Since asbestos-like bodies can form in response to respirable, transparent, color less fibers deposited in the lungs and com posed of materials other than asbestos; and since basing classification of these structures upon identification of the cen tral fiber presents difficulties, a generic term, "ferruginous," has been proposed for all bodies formed in response to the presence (in body tissues) of a broad spectrum of fibers, including asbestos. Davis 3 and Collet (according to a letter in June 1966) demonstrated with the elec tron microscope that ferruginous bodies are formed within macrophages by gran ules of ferritin or a ferritin-like protein -- A iM'ii i I'MM: 'MISl-: { $&'- l:.#/ - '1 i U. Vrrooogy Arch Path--Vet 85, May 1988 r/j r.y o 540 FERRUGINOUS BODIES--GROSS ET AL do not result in the forma tion of ferruginous bodies when inhaled. Respirable fibers, how ever. are apparently ubiq uitous.0 They may be mineral, animal, or vege table in nature and of either natural or synthetic origin. They are dissemi nated by industrial proces sing, community activities, personal habits, and the action of natural forces. Fig 1.--Asbestos bodies from the lung of an asbestos worker to illustrate some of the more simple forms that may be found. In addition to some apparently naked fibers, there are pale, nonsegmented, rodlike bodies with bipolar clubbing. The dust was probably chrysotile (concentration method; smear; unstained; >' 1.100). Also, we have recently r*S5 ^ j|J ported experimental pzkgtw y duction of ferruginous^ U.T bodies with ceramic -4s bers of aluminum silicatw-' hv! that are precipitated upon and around These bodies were indistinguishable bjfc'U some foreign materials. light microscope from many of those isqt_~" An asbestos body, therefore, is only one kind of ferruginous body; one in which the central filament is an asbestos fiber. As will be seen later, the appearance and dimensions of these bodies are so varied as to defy the reasonably short description usually employed. lated from an asbestotic lung of a knowit-h asbestos worker 7 (Fig 1). Although nonC-y' segmented, they were golden-yellow, sym^-! metrical, clubbed bodies, staining dee]C/" blue with Peris' test and exhibiting central transparent filament. The present paper discusses our furthei^.* * J The problem now confronting investi gators concerns the significance of the widespread finding of ferruginous bodies in the lungs of urban population groups. The solution of the problem is, of course, linl ed to the identity of `he central fiber about which the ferruginous body forms and which is at present unknown. It is hoped that recent analytical advances, such as electron diffraction and microprobe will provide techniques for defini tive identification of the central fiber. findings as follows: ^__ 1. --Ferruginous bodies are developed inCD* 4p the lungs of hamsters in response to thej"""" presence of "biologically inert" filament ous aluminum silicate, glass, and silicon carbide particles. 2. --A simple method is given for isolat ing ferruginous bodies and bare fibers (including asbestos bodies) from lungs. The method is given in detail and the re sults obtained are described briefly. Up to this point, the identification of ferruginous bodies in the lungs of un selected autopsied hospital patients as as bestos bodies1 has been based on the hypothesis that transparent fibers of re spirable size composed of materials other than asbestos either are not encountered in industrial and community environ ments. are not deposited in the lungs, or The Production of Ferruginous Bodies Groups of 12 hamsters each were in jected intratracheally with 3.5 mg of fibers contained in 0.5 ml of aqueous suspen sions. This was done under light ether anesthesia with the aid of an illuminated, self-retaining speculum that made the vo cal chords visible and allowed the inser- tion of a long 18-gaug vocal chords under di of the following were 1. Ceramic alumii This is an uncoated median diameter of the fibers were unde many filaments were free silica was detect 2. Silicon carbide v 99.5+% SiC. Fiber d 0.5p to 3p, and fiber from 100a to 750p. 3. Glass fibers, unci a mean diameter of length of 4.4u. 4. Cosmetic talc. I fibrous material in th< in diameter and lp i. 5. Attapulgite (fib Fifty percent of the O.lp in diameter and 6. Chrysotile (95% on this continent is < the fibers were of ; mensions. Isolation and Ct Ferruginoi Samples of lung t strips 3 to 4 mm thick 0.5 cc in volume, are or plastic containers added about 20 time; of commercial 5% s solution. This is allo\ turbed at room temp hours until all chemic More hypochlorite so at frequent intervals been digested. For small lungs, si and guinea pigs, t amount of addition o 'olution should be sue ;s digested in approxir human lungs, unless q if ferruginous bodies digestion is not nece.' In the case of hui r i.'-rn ieec ther ted. a: ^ FERRUGINOUS BODIES--GROSS ET AD 541 -.on of a long 18-gauge needle between the . neal chords under direct observation. All ; the following were injected: 1. Ceramic aluminum silicate fibers. This is an uncoated ceramic fiber with a '.-.ecian diameter of 2u. Fifty percent of r e fibers were under 75u in length, and -.any filaments were shorter than 15tt. No :ree silica was detected in the fibers. 2. Silicon carbide whiskers. These were '-4 5--ST SiC. Fiber diameter ranged from 5ii to 3u, and fiber length that ranged from lOOu to 750u. 3. Glass fibers, uncoated. The fibers had .. mean, diameter of 0.4u and a mean .e.ngth of 4.4u. 4. Cosmetic talc. Fifty percent of the -brous material in the talc was under 0.2u diameter and lu in length. 5. Attapulgite (fibrous clay mineral). F.fty percent of the fibers were under lu in diameter and lu in length. 6. Chrysotile (95% of the asbestos used n this continent is chrysotile). Most of -...5 fibers were of ultramicroscopic di- .ensions. .. Isolation and Concentration of Ferruginous Bodies Samples of lung tissue cut into thin -rips 3 to 4 mm thick, or fragments about ' 5 cc in volume, are placed in clean glass plastic containers. To the tissue is s ".ded about 20 times the tissue volume commercial 5% sodium hypochlorite ? .-tion. This is allowed to stand undist-rbed at.room temperature for several -rs until all chemical action has ceased. 1- re hypochlorite solution is then added frequent intervals until the tissue has " -r. digested. F ,v small lungs, such as those of rats guinea pigs, the frequency and mi of addition of fresh hypochlorite -".on should be such that all lung tissue rested in approximately 24 hours. For an lungs, unless quantitative recovery rruginous bodies is desired, complete 'ion is not necessary, the case of human lungs, the fer ruginous bodies and bare fibers are often associated, with a sticky lipidic film ad herent to the bottom of the container. The stickiness allows one to pour off all the fluid and 'undigested lung tissue without loss of the bodies and fibers. Because of the presence of anthracotic pigment, the film is usually gray in color. The film is dissolved by vigorously washing with a mixture of one volume of chloroform and two volumes of approximately 50% ethyl alcohol; the total volume should be the minimal amount needed to remove all the1 film. The wash fluid is centrifuged at 2,000 rpm for about five minutes. Because of their high specific gravity, the fer ruginous bodies and the insoluble mineral particles settle to the bottom of the tube. On the other hand, most of the carbonace ous material collects at the interphase be tween the chloroform and the aqueous alcohol. If too mucn alcohol is used, the carbonaceous material will lose some of the water that lowers its specific gravity. As a result, there will be no separation between the anthracotic material and the ferruginous bodies. In such cases, rehy dration followed by the addition of chloro form will usually effect a good separation. :-/ J.v ?... . i 'Tjr~[ , i' All of the fluid and the carbonaceous, more viscid material above the. sediment at the bottom of the tube are discarded, and the walk of the tube are cleaned of the adherent anthracotic material. The sediment is washed several times with water to remove all hypochlorite and other water-soluble materials. It is then stored in an aqueous or alcoholic medium. When smears are made of the suspen sions, it may be advisable to dehydrate the smear and use a mounting medium to render much of the mineral dust associ ated with the ferruginous bodies less con G.. < u-' l spicuous. The naked fibers remain visible. In the case of small animal lungs, chloroform and the supernatant fluid were poured into centrifuge tubes in a propor tion of 1;2. After centrifuging, the super natant fluid vcas carefully removed and discarded xcept for about 1 ml left un- Arch Path--Vo! So, May 1963 OG MGS -- . V . - - . -v* ".' 542 FERRUGINOUS BODIES--GROSS ET AL disturbed on the bottom. The film on the bottom of the original container in which the lung tissue was digested was then re moved, as in the case of human lungs. This fluid was added to a pool of whatever sediment was obtained from the super natant fluid. The subsequent procedure was the same as -with human lungs. We have worked with formalin-fixed tissue only, but there appears to be no reason why this method should not work equally well with fresh lung tissue. \ Results Paraffin Sections.--Initially the fer ruginous bodies were sought only in paraffin sections that had been stained with hematoxylin and eosin or Peris' test for iron. Because of the paucity and small size of these bodies in the sections, the hematoxylin made the search more diffi cult. Subsequently, replicate sections that were given the Peris' test only, or also lightly counterstained with eosin and cleared, proved to be satisfactory. The injected fibers generally were con fined to the air spaces, where they were associated with free macrophages. Some of the filaments passed through the bodies of one to three, and even four, macro phages so that these cells appeared to be impaled as though upon a spit (Fig 3 bot tom left). When the sections had been stained for iron, the dust-containing areas, under low magnification, were usually marked by a granular deep blue colora tion. In sections of lungs of hamsters killed one month after an intratracheal injection of aluminum silicate and glass fibers, oc casional ferruginous bodies were fourd. These were non-segmented, light-yellow structures with bipolar clubbing and a transparent central filament (Fig 2 top left, and 3 top left). These, subsequent to the Peris' test, took on a deep blue color that often obscured the central filament. Very similar non-segmented bodies were seen in suspensions of isolated and con centrated human asbestos bodies derived from an asbestotic lung of a worker known to have been exposed to chrysotile asbestos dust for 30 years (Fig 1). The ferruginous bodies that formed in response to chrysotile asbestos were smaller than those that formed in response to aluminum silicate and glass, and also different from the latter two in being seg mented (Fig 4 bottom left). The ferrugin ous bodies were more readily found in the lung sections of hamsters injected with aluminum silicate filaments than in lung sections of animals injected with filament ous glass or chrysotile dust. No ferrugin ous bodies were found in the lung sections of hamsters injected with silicon carbide filaments at this time (one month after the injection). Examination of lung sections of ham sters killed six months after the intra tracheal injection of the filamentous dusts revealed no more ferruginous bodies than were encountered five months earlier. No segmented forms were found except in association with chrysotile dust. No fer ruginous bodies were seen in lung sec tions of hamsters injected with silicon carbide. Dust-containing alveoli found in sections of lung from a hamster injected with talc were easily identified because of the blue coloration caused by the presence of iron; however, ferruginous bodies could not be identified. Similarly, no ferruginous bodies were found in lung sections from hamsters injected intratracheally with attapulgite. Lung Digests.--The smears of the sediment derived from the digestion of the lungs from hamsters injected six months previously with aluminum silicate, glass, and chrysotile, respectively, consisted largely of naked filaments, but many ferruginous bodies were also seen. Although most of the ferruginous bodies that had formed in response to aluminum silicate and glass fibers were non-segmented, a number of segmented forms were also found (Fig 2 top right, bottom left, bottom right: and 3 fop right, bottom left, bottom right). A more prolonged search of the , | i ,* -- | , l i - .* j I j Arch Path^Vol 85. Mat/ J95$ 5 15 O ,< i r sediment from lungs c with silicon carbide w several ferruginous be This search was faci Peris' test for iron to ies were mostly nonse for the clubbed ends, filaments was thin. ( fiber was found with ing at one end, a fu. the other end, and a ing near the middle ( segmented ferruginoi formed around silicon observed. Unfortunat the blue pigment of th outline indistinct (Fi The sediment from jected with talc was < crystalline plates; but a number of non-seg bodies were also four transparent central 1 left, and 3 top left), T! action for iron had al smear, and the outli were indistinct becau; the pigment (Fig 4 bo Unexpectedly, fern, more difficult to find i "hrysotile injections t silicate injections. Th observed with the co Although few in numt ies were segmented ( One of the most intt was that, when staine that passed through t more macrophages s` ferritin or ferritin-lil the intracellular port (Fig 3 bottom left). The sediments fron sters injected with att ferruginous bodies. ' ferruginous bodies in be interpreted as a indicate that our po. not attributable to th nr, ms ? "** J 5 n L* LJ FERRUGINOUS BODIES--GROSS ET AL 542 iediment from lungs of hamsters injected with silicon carbide was necessary before -everal ferruginous bodies could be found. This search was facilitated by applying Peris' test for iron to the smear. The bod ies were mostly nonsegmented, and except :or the clubbed ends, the coating on the filaments was thin. One silicon carbide fiber was found with a club-shaped coat ing at one end, a fusiform coating near ;he other end, and a very slight thicken ing near the middle (Fig 4 top left). Two segmented ferruginous bodies that had formed around silicon carbide fibers were observed. Unfortunately, the diffusion of the blue pigment of the body rendered its outline indistinct (Fig 4 top right). The sediment from a hamster lung in jected with talc was composed largely of crystalline plates; but upon careful search, a number of non-segmented ferruginous bodies were also found. These too had a transparent central filament (Fig 2 top left, and 3 top left). The Prussian blue re action for iron had also been used in this ?mear, and the outlines of these bodies were indistinct because of the diffusion of the pigment (Fig 4 bottom left). Unexpectedly, ferruginous bodies were more difficult to find in lung sections after chrysotile injections than after aluminum -hlicate injections. The same finding was observed with the concentration method. Although few in number, all asbestos bod ies were segmented (Fig 4 bottom right). One of the most interesting observations was that, when stained for iron, filaments 'hat passed through^the bodies of one or ".ore macrophages showed a coating of : rritin or ferritin-like material only on `he intracellular portions of the filament 1 Pig 3 bottom left). The sediments from the lungs of ham`-rs injected with attapulgite revealed no -wuginous bodies. The failure to find '--ruginous bodies in these sediments may interpreted as a negative control to cicate that our positive findings were attributable to the accidental inhala tion of fibers in the ambient laboratory air. The sediment from the human asbestotic lung was a rusty, red-brown color. In the smear, a wide variety of asbestos bodies were seen in addition to innumer able naked fibers. As previously indicated, a large number of the asbestos bodies were pale, thin, and nonsegmented. Also of interest was the fact that many of the largest bodies did not have smooth stirfaces, but were spiculated. The spicules Fig 2.--Ferrug.nous bodies formed in response to aluminum silicate filaments in a hamster Killed five months after an intratracheal injection of 3.5 mg of the dust. Bottom right, naked filament (concentration method; unstained smear; x 1,100). hir Pi!. f u<- * *t `Wit;, i : 111: i ilii til:: F*?wi = rv-t<t'1. MH;: r jjihlj .(rf*i-a, Mff; `itr i A id: Arch Path--Vol 85, May i968. ,i ur ..VH i__B_B___0_0__05456 | $44 FERRUGINOUS BODIES--GROSS ET AL were often coarse with squared ends, A few of the bodies lacked symmetry. Some pear-shaped bodies without a central fila ment were also seen. Although most of the bodies were more or less rectilinear, many curvilinear forms were also present. Some of the latter appeared to measure between 180: to 270 \ In the larger spicu- protein at either end with relatively long stretches of naked fiber in between. In an attempt to free asbestos bodies from adherent fine carbon particles in an otherwise `'clean" suspension, it was sub jected to ultrasonic vibrations for a few seconds. Unexpectedly, only naked fibers remained, and no asbestos bodies could 1Vt 1 Il i represent a general particles and are n asbestos fibers. To ings may have a ruginous bodies th increasing prevale remains to be dete ity depends, of cou lated forms, the central fiber was often be found in the suspending fluid. the central fiber in obscured by the thick, dense, red-brown coating. Some of the very long thin fibers (50u to lOOu) often had segments of ferro- The distinction heretofore made be tween asbestos bodies and pseudo-asbestos bodies may have been based in part on The method of isol of uncoated fibers from human lung; what the observer believed to be an ap this paper may ht Fig 3.--Ferruji.ious bodies formed in response to Filamentous glass dust. Bodies (top, left and right, and bottom right) are unstained. Four macrophages are pearance consistent or inconsistent with that of asbestos bodies. More often, how nature, identity, ar filamentous partic faintly outlined. Only the intracellular portions of the filament are coated with iron (Peris' stain, x 1,100). ever, this distinction was based on the observer's knowledge that the host had monary ferruginoc It is highly pro! or had not been exposed to respirable tion of the ferrugi: asbestos fibers. the method used Regardless of the nature of the central is not likely that fiber, the bodies that result in response to proteins leading t( the presence of filamentous dust in the tissue elements in i 3 lung have as a common feature a coating of iron-containing protein (ferritin or fer ritin-like). Furthermore, it appears, from the ferruginous bi In all likelihood, of the bodies is c a study of the pleomorphism of human iron and other in- asbestos bodies, which was so well illus main to retain an- trated by Gloyne and Merewether,8 that the bodies. The fra differences in size, segmentation, or other altered ferruginou morphologic features of the ferruginous 1 the ease with whi J' coating probably would not serve to dis I subjected to ultras tinguish between ferruginous bodies of rendering the cei asbestotic origin and those of nonasbes- ! may further facili totic origin. these fibers. Thomson has proposed to differentiate between asbestotic and nonasbestotic fer ruginous bodies on the basis of the trans parency or opacity of the central fiber.2 This proposal seems inappropriate, inas much as we have demonstrated that a number of transparent fibers of respirable size other than asbestos are capable of producing ferruginous bodies that are in distinguishable from those produced by asbestos. There appears to consider all fil ` same category as their pathogenic p is probably based cept of the patho in general, and asi Such a mechanist: , pulmonary fibrosi j sue response to 1 j duced when puln At any rate, it is obvious from the pro ated or impaled h duction of ferruginous bodies in hamsters asbestos fibers. in response to respirable, colorless, trans parent filaments of aluminum silicate, glass, and silicon carbide, that such bodies It need only bt mechanistic conct , of crystalline silic Arch Path--Vol 85. May 1968 I s | ' J r*" t \ ji Vi f l-'-Cb : _ ^ i ir, j long in an ; suba few fibers could urnan FERRUGINOUS BODIES--GP.OSS ET Ah 545 represent a general reaction to filamentous particles and are not a specific reaction to asbestos fibers. To what extent our find ings may have application to the fer ruginous bodies that are being found with increasing prevalence in human lungs l"* remains to be determined. The applicabil ity depends, of course, upon the identity of the central fiber in the ferruginous bodies. The method of isolation and concentration of uncoated fibers and ferruginous bodies from human lungs which is described in this paper may help in the study of the nature, identity, and prevalence of inhaled filamentous particles and associated pul monary ferruginous bodies. It is highly probable that the composi tion of the ferruginous body is altered by the method used for isolating it, since it is not likely that with the destruction of proteins leading to the liquefaction of all tissue elements in the lung, the protein in die ferruginous bodies should be spared. In all likelihood, the protein constituent of the bodies is destroyed, and only the iron and other inorganic components re main to retain and maintain the form of the bodies. The fragility of this chemically altered ferruginous coating is indicated by the ease with which it is removed when subjected to ultrasonic vibrations, thereby rendering the central fiber naked. This may further facilitate the identification of these fibers. There appears an increasing tendency '> consider all filamentous dusts in the same category' as asbestos with regard to their pathogenic-potential This reasoning .s probably based on a mechanistic con cept of the pathogenicity of fibrous dust .n general, and asbestos dust in particular, huch a mechanistic concept holds that the ..Imcnary fibrosis in asbestosis is the tis-e response to mechanical trauma proiced when pulmonary cells are perfor``sd or impaled by the fine points of the cestos fibers. It need only be recalled that a similar '-hanistic concept of the pathogenicity -rystalline silica was abandoned many years ago because of overwhelming evi dence against its validity. Just as the proven biologic "inertness" of diamond dust was the coup de grace for the mecha nistic pathogenetic concept of silicosis,a so should the proven biologic "inertness" of filamentous aluminum silicate 10 have dis credited the mechanistic pathogenetic con cept of asbestosis. Extremely thin flakes of glass may also be considered to have sharp cutting edges; yet, glass has also been found biologically fig 4.--Ferrug.ious bodies formed in response to other Filerrer.tous dusts and stained for iron (Peristest). The central fiber (top, left and right) is silicon carbide; and (bottom left) tremolite (talc) (x 1,110). 10m A *V i.-ii * i i ;' : 1-.. I- - n-4il aflHitt! -m j. (trti' * :->hi -l'|f I (b*it4 ? I Hu: ritbsit SnJtJJj fiHJOi;- L,y;- a k.B Suiit-!p*HB- BMUilII- %' F k: ft'' mt (iPOC- j_BB 0005458 T 1* Arch Path--Vo2 85, May 10Si * , i i Hj W i 1 - w .j 11 . ) -I* > i J 4iV '' -A yfrisSf I I. Il 1 f i 546 FERRUGINOUS BODIES--GROSS ET AL `"inert"" when inhaled or injected into the lungs of animals. Silicon carbide is noted for its hardness, sharp edges, and points, which make it an ideal abrasive. When inhaled as a fine dust or injected intratracheally. it has caused a pulmonary re sponse likewise classified as biologically "inert." 11-1- Gaining increased attention is a newer concept that the potential of extraneous trace metals and other materials associ ated with fibrous minerals can cause the injury previously attributed to fibers. The respirable fibers may provide a transport mechanism for dosing tissues with injuri ous materials associated with the fibers. Cralley et al13 have shown that asbestos textile workers in the past have been ex posed to appreciable concentrations of nickel, chromium, and manganese associ ated with the fibrous mineral, and abraded from the alloy metal in asbestos process ing equipment. They state further that there is evidence that this phenomenon exists in relation to a number of other fi brous minerals. There is also some indi cation that the biological response in the formation of ferruginous bodies may be related to the nature and extent of the layer of metal solute surrounding the fi ber. Additional research needed in these areas is currently underway. Unless the above facts are kept in mind, the finding that ferruginous bodies are formed in response to aluminum silicate, silicon carbide, and glass filaments in the lungs, may be used as still another reason for erroneously classifying these dusts with asbestos in their ability to produce lung damage. This investigation was sponsored by JohnsManville Corporation, New York, and supported in part by Public Health Service research grant UI 86-66-156 from the National Center for Urban and Industrial Health. All experimental materials used, except chrysotile (supplied by Johns-ManviUe Corporation. New Yorkl were obtained from and analyzed by the US Department of Health, Education and Welfare, Public Health Service Center for Urban and In dustrial Affairs, Occupational Health Program. References 1. Thomson, J.G.; Kaschula, R.O.C.; and Mac Donald, R-R.: Asbestos as a Modern Urban Hazard, S Air .Med J 37:77-81 (Jan) 1963. 2. Thomson. J.G.; Path, F.C.; and Graves, W.M.: Asbestos as an Urban Air Contaminant Arch Path 81:458-464 Olay* 1966. 3. Cauna. D.; Totten, R.S.; and Gross, P.: As bestos Bodies, in Human Lungs at Autopsy, JAMA 192:371-373 (May) 1965. 4. AnjilveL L., and Thurlbeck, W.M.: The Inci dence of Asbestos Bodies in the Lungs at Random Necropsies in Montreal. Canad Med Assoc J 95: 1179-1182. 1366. 3. Davis. JM.G.: Electron-Microscope Studies of Asbestosis in. hlan and Animals, Ann NY Acad Set 1323S-LL1. 1365. 6. Cralley. LJ.. et al: Source and Identification of Respirable Fibers, read before the annual meet ing of Ai.-.eiican Industrial Hygiene Conference, Chicago, May 1967. JA1HA, to be published 7. Gross. P.: Cralley. LJ.; and deTreville, R.T.P.: "Asbestos- Eodies: Their Nonspecificity, JAIHA 25:541-542 `Nov-Dee. 1967. 8. Glcyr.e. SXL. and Merewether, E.R.A.: "As bestos," International Labour Office Supplement, p 7 (Jan) 1938. 9. King, E.J.; Yoganathan, M.; and Nagelschmidt G.: The Effect of Diamond Dust Alone and Mixed With Quartz on the Lungs of Rats, Brit J Industr Med 15:92-95, 1958. 10. Gross, P., et al: The Effect.of a Synthetic Ceramic Fiber Dust upon the Lungs of Rats, Arch Indust Health 13:161-166 (Feb) 1956. 11. Gardner, L.U.: Studies on the Relation of Mineral Dusts to Tuberculosis, Part n; The Rela tively Early Lesions in Experimental Pneumoconio sis Produced by Carborundum Inhalation and Their Influence on Tuberculosis, Am Rev Tuberc 7:344. 1923. 12. Gross, P.; Westrick. MX..; and McNemey, JM.: Experimental Tuberculopneumoconiosis, Arch Indust Health 19:320-334 (March) 1959. 13. Cralley, L.J.; Keenan, R.G.; and Lynch, J.R-: Exposure to Metals in the Manufacture of Asbestos Textile Products, read before the annual meeting of American Industrial Hvgiene Conference, Chicago, May 1967, JAIHA 28:452-461 (Sept-Oct) 1967. i r I I I NOTE- this DOCUMENT DIO NOT COME fROM PPG NLE T Y ting adult fern, stock were fed a h' fat (28%. lard) and for I to 11 weeks. N the atria within four with a progressive f peaked at nine we normochromic aner weeks. Hematocrit counts decreased !r paralleled lesion on and white blood cell able change from i dot retraction time cantly; neither die changes which occti induction of atrial t independent respor C ARDIAC d atrial thrombosis, a semipurified dit lard) and low in p Thrombosis occur within five weeks may reach an in weeks. Time of o; a definite strait Accepted for public From the Departmt Mississippi School of Read in part at th Federation of Americ Biology, Chicago, Apr Reprint requests Medical Center, 2500 `Dr. Balli. Arch Path--Vol 85, Mat/ 2968 | ,4 ry | J-2.