Document G6jZw31jg0zbZpxZz7Jxro8pY

ROCZNIKI AKADEMII MEDYCZNEJ In. JULIANA MARCHLEUSKIEGO In BIALYSTOK Supplement 24 INFLUENCE OF POLYVINYL CHLORIDE (PVC) DUST ON RAT RESPIRATORY SYSTEM by J. Popow /o y BIAiYSTOK 1969 TW& pv.v 'v, .-r *v* .! 11 V __ __: ..... -****"__. _._--<,, . rw- \ ... . :v . V ucc 065192 ROCZNIKI AKADEMII MEDYCZNEJ la. JULIANA MARCHLEUSKIEGO in BIALYSTOK Supplement 24 INFLUENCE OF POLYVINYL CHLORIDE (PVC) DUST ON RAT RESPIRATORY SYSTEM by J. Popov BIALYSTOK 1969 This pv cs ~ ** * wN / I IAA 065193 Telephone Welwyn Garden 23400 (STD Cod* 07073). STD Cod* from London Ar*a M Ttlax 264251 lelplaxt Welwyn y tnuuairit^ Limited Plastics Division Kr IN Vhaalar Jr _ Project Manager Environaental Protection and Occupational Health Union Carbide Corporation P0 Box 8361 South Charleston ' Vest Virginia RECSVES AUG 6 1979 , . .. ,, an whs? .% * Your ref. Our ref JS/AH/DSO-107 Tal ext 3162 Date 20 July 1979 Dear Nick PVC'DQST Thank you very much for your letter of July 6* I have pleasure in enclosing our translation of the paper by Popow which you requested. I do not know whether this will be of any interest to you in the liability case which you have. As you will see when you read it, Popov's experimental conditions were utterly extreme. X think any biological system will be overwhelmed by 97 g/m* of FVC or any other fine dust. These conditi ns are a long way from our TLV of 10 mg/oK. I have just got back from my annual vacation and your letter was on the top of my pile. X have not given copies of this Popow translation to Ted Torkelnon. Maurie Johnson or any of my other American friends. Xt may be some little time before X get around to doing this. Xf you could run off some quick copies for them, X would be grateful. With best wishes Tours slneerely J Stafford Division Manager Health and Environment Protection Ene ucc 065194 COSTENTS I. INTRODUCTION " II. PURPOSE OF THE WORK AND ASSUMPTIONS III. RESEARCH TECHNIQUE IV. RESULTS OF INVESTIGATIONS 1. Control group 2. Group I. Early changes 3* Croup II. Inter changes A. Croup III. Changes after cessation of exposure to PVC dust V. INTERPRETATION OF RESULTS AND DISCUSSION VI. CONCLUSIONS VII. SUMMARY VIII. REFERENCES 3 (5) (8) * (8) 10 (10) 10 (10) 12 (U) 15 (16) 20~ (25) 25 (32) 35 (38) (39) (45) ucc 065195 1. INTRODUCTION Ths pathological changes occurring in tha raspiratory aystem under the influence of inspiration of air contaminated with particles of various dusts have been -described for about 100 years a* dust disease - pneuooconi sis. Initially pathogenic action was only ascribed to silicon dust. Therefore the investigations undertaken mainly concerned silicosis. On the basis of ellnical studies (Levin [73], Sokolov et al. [109], Vlglianl et al. [122]) and experimental studies (Cabafiskl et al. [13], Cross et al. [37], P Heard et al. [95]) it was found that in the lungs silicon dost causes formation of fibrous nodules, composed of thick strands of collagenous fibres, undergoing hyalinlzatlon. Sometimes there ere necrotic masses at the centre of such e nodule. The discovery of the pathogenic properties of silicon dust had the result that many authors turned their attention to the problem of dust diseases. Clinical and exparimental investigations made it possible to determine the action of individual types of dust. As a result of this research it was established that coal duat accumulates in the lungs, damages * the pulmonary alveoli end causes formation of dust nodules with the character of giant-cell granulomas. These nodules ere of e constant character vith $ susceptibility to fibrous atrophy (Nlepobomakl at al. [80], Schepars [106], Worth at al. [121], Soinlerz at al. [110-112]). However, tale dust causes so-called lntraparanehymatous focal pneumonia. In which collagenous fibres appear at a vary lata stage in the inflammatory foci and there la no forma tion of pneumoconiotic nodulgs (Rakovski [100]). In the course of asb stosis ve can distinguish an early stags, called the vaso-histiocytic stage, and a lata etaga, called the flbroblastlc-collagenic stage (Avril [3]). A charac teristic feature of this conlosls la diffusa fibrosis and hyallnlzatlor. without f rmaeion of nodular lesions. Sometimes so-call i a'bcst s bodies OCC 06^ 96 can b datacted among the atriaa ' eonnactlva tiasua (Hamas [40]). Cott n duat eausaa chronic bronehitia (Fatiaova [25]), whereas camant duat cauaaa acute tracheitia and bronehitia, and than chronic atrophic inflamation of these ragiona. In tha lunga there ia development of what ia known as catarrhal-intraparanchymatoua inflaaraation, leading to atrophy of tha inter alveolar septa. Fibrosis is not vary pronounced and is of a constant nature (Niepolomskl at al. [81]). Berylliosis is included among the toxic dust diseases in view of the mechanism of Its development, and in the early stages there is exudative pneumonia, which quite quickly changes to a productive phase. There is formation of nodules composed of histiocytes end lymphocytes. These nodules ere often surrounded by striae of collagenous fibres, undergoing hyallnizatlon. 'Sometimes giant cells, similar to > Langhans N cells, are to be found in the centre of such e nodule CMarehand [75], Ruttner at el. [104], Stofer [114]). There is no doubt concerning the existence of.^conlosis ks a distinct nosologic unit (Kleczedski [61], Zahorskl [123]). Research undertaken so far has endeavoured to establish the mechanism of its genesis (Aaoudru [1], Ottovic: [93]). Many authors (Ebert et al. [24], Hames et al. [40], Heppleston [44], Folicard [95]) consider that pneusoconiotlc changes in the lungs only develop with participation of living cells. In the opinion of the above authors these cells absorb many particles of dust end then carry them to the connective tissue around the vessels, to the well of the bronchi and alveoli end to the lymphatle vessels, however, there ere those (Cross [36, 37]) who assert that the dust particles reach tha counactive tissue without the participation of living cells, as * result of the resplrat ry movements of the lungs. In recent years the literature has contained reports on the possibility of pathologic changes developing in the respira tory system reminiscent f e nlosis, but caused by the ecti n f plastics OCC Q65A91 (Boltsov [10], Roussel [102]). That* rep'rts draw ay attantl n to plastics which ara now In general uea and have antarad many apharaa of dally Ufa (Markiewlcx [76], Kaatlerlna at al. [57], Forejko at al. [97], Schlldknacht [107]). On account of thalr plaatlelty, roalatanca to the action of aclda and alkallaa, aaaa of ahaplng and relatively low production costa, plaatlca products have also found application in biology and medicine [Frankowskl [29], Jasldskl at al. [53], Kavecki [58], Kavecki at al. [59], Ku6 at al. [69, 70], Nowak [83,. 84, 85, 87], Olefisld at al. [89], Kob at al. [101], Rzepecki [105], Stanlszawska [113], Szymaska at al. [116], Grabowski at al. [35], Kpdra. [60], Komezyfiskl at al. [64]). One of xbe aort. important and first synthetic thermoplastic macromolecular compound produced on an industrial scale was polyvinyl chloride (PVC) (Franty at al. [30], Vandarberg [119]). Pure polyvinyl chloride has the form of a white, tasteless and odourless powder. In industrial produc tion, material made from It can be given various forms, with varying elasti city and hardness. Therefore these polyvinyl chloride products have found application in the meat Industry (Bohoslewlcz [9]), pharmaceuticals (Chviaikowska at al. [15]), in sport (Kopczydski [65]) and in medielne (Goetzen [34], Horarowski at al. [47, 48], Jankowska [52] and othera). The introduction of various new chemicals and various products made from them In daily use has given rise to the problem of the action f these compounds on the human body, both of the producers snd of the users. This problem has been dealt with in many works In the national and foreign literature (Crlstea at al. [16], Bartenov at al. [4], Hervieux [45], Kalinin [54], Kallftska [56], Koelsch [62], Laehnlt [71], Lefaux [72], Markicvlcz [76], Moeschlln [78], Kowalska at al. [66], Kallnovska at al. [55], Smollk [108], Trosfin [117], Colow at al. [17], Bayanova et al. [20]). The pr blen f the t xicity f plastics, and especially polyvinyl chi ride, is ucc 065198 still open, despite the feet that, various lnvestlgatl ns In this direction have been undertaken (Quooss [99], Russel [103], Pennarola et al. [94]). The opinion expressed In the vast majority of published works Is that polymers are physiologically Inert compounds, and the harmful effects are caused by auxiliary chemicals In the polymer manufacturing process (initia tors, catalysts, emulsifiers) or taking part In forming the physical proper- * ties of the polymers (stabilizers, plasticizers) (Danlshevskil et al. [19], t Novak [S2]). Some authors (Filatova [26, 27], Gervals [32], Witnauer et al. [120]) ascribe harmful action to vinyl chloride, the toxic propertie f which are already recognized and measures to prevent poisoning have already been taken in many factories (Beusnel 17], Broltman [11], Bugajska [12], Saltreva [21], Gabor [31], GUnther [39], Krivoglaz et al. [63]). However, many authors consider that certain plastics may have pathogenic properties and as confirmation of their viewpoint they cite the harmful effects f massive inhalation of polyamide dust. This dust causes acute catarrhal pneumonia with formation of granulomas of the type around foreign bodies (Clovacchini [33]), and sometimes even changes of the nature of storage disease (Medve et al. [77]). There are also those who ascribe carlnogenic action to plastics (Fitzhugh [28], Hueper [51], Novak [88], Kesswetha et al. [79], Oppenheimer et al. [90], Russel et al. [103], Bates et al. [5], Druekrey et al. [22, 23], Oppenheimer at al. [89]). As a result of these Investigations it was found that after Implantation of plates there Is nearly always appearance of neoplasms [Guess et al. [38]), after Implanta tion of a thread they only develop occasionally (Kogan et al. [63]), and neoplasms are never found after implantation of powder (Oppenheimer et al. [92]). Although most authors are of the opinion that polyvinyl chloride Is a physl logically neutral comp und, in recent years the literature has UCC 065199 A ' c stained ccasional rap rta n tha ccurrenee of various bodily dlsordars and changes la tha organs f vorkar* employed la factorlas manufacturing polyvinyl chloride or products made from this material, viz: la the llvar (Pushln [98]), especially la older women (Troshlaa [117], la the phalangeal bones of the heads and la the skla (Harris sad Adams [42]), and la tha vas cular and narvous system (Suciu at el. [115]). Bugajska at el. [12] have drawn attention to the possibility of toxic action of PVC. Roussel at al> [102] found posthumous atypical changes la the lungs and were unable to assign these changes to a set of known nosologic units. These authors assume that these changes should perhaps be associated with work done for many years by this worker in a PVC factory. In addition to descriptions f clinical observations, the literature also contains experimental works conducted with polyvinyl chloride. Bemt (quotedJbyDanishevskil [6]), _f r example, fed animals an oily suspension of ground FVC and shoved that it does not have any toxic properties, but he also ascertained that the material Is soluble in the gastric and intestinal Juice. Boltsov [10], however, mentions the possibility of development of conlosis In animals after Intra tracheal administration of PVC resin. He found that In their lungs, there is thickening of the Interalveolar septa and also peribronchial and perivascular inflammation. My preliminary Investigations on rata (Popov [96]) submitted to the action of polyvinyl chloride also indicated that this dust Is a noxious agent for tha lungs. Lymphocyte-Ilka cells multiply under the influence of inspiration of this dust. They accumulate In the form of cuffs around the blood vassals, and thara Is also intumescence of the muscles and proliferation of collagenous fibres in tha wall of tha bronchi, and pulmon ary emphysema. ucc 065200 II. PURPOSE OF THE WORK AMD ASSUMPTIONS Am follows from chls rsvlcw of the lltsracurs, th problem of Che offset of plasties on tha living organism has not pot boon solved completely. Because polyvinyl chloride la one of the most frequently used plastics, ve decided to conduct investigations of the respiratory system after long term action of polyvinyl chloride and establish the nature of the resulting pathomorphologlcal changes. Moreover, ve tried to determine whether the changes in the lungs after cessation of exposure to PVC dust recede, whether they stop developing, or whether they still occur. Another interesting problem worthy of consideration is whether the changes occurring in the lungs promote the development of complications, as occurs for example in the course of silicosis. In the literature available to me 1 have n t come * across reports on this kind of experimental investigations on animals. III. RESEARCH TECHNIQUE The experiments were conducted on 60 white rats of both sexes of the Wistar strain. A control group comprised 10 rats. The age of the animals at the start of the experiment ranged from 3 to 4 months. The rats weighed from ISO to 220 g. The animals remained in separate cages. In a well-lit room which was aired every day, with its temperature maintained in the range from 16* tro 20*C. The animals were given mixed, nonstandard food regularly. The test animals were divided into three groups. Croup I comprised 16 animals exposed to PVC dust from 1 to 4 months. In this group I observed the picture of all pneumoconlotic lesions. Croup II comprised 22 rats, exposed to the dust from 3 to 12 months. In this group I observed the picture f late pr.cumoeonl tic lesions. Cr up III o cocipriAid 22 rnts which, after 12 months of exposure to the dust, were kepr^ A'n^rv.itlon for a nerlod f 8 months. This group was employed for 6S20f A. - ' Investigating the behaviour of the pathologic ehang s that arose und r the lnflu nee of p lyvinyl chloride after Its action had ceased. The c ntrol group comprised 10 animals. They were kept under observation for 20 months, 2 rats being killed by decapitation every 4 months. Exposure to polyvinyl chloride dust was affected in the following way: the rats were placed in a special chamber with dimensions 1.46 a x 0.56 m x 0.38 a and were submitted to the action of polyvinyl chloride dust every day for 1 hour. A rubber hose was led into this chamber, and the other end of the hose was in a glass vessel with capacity of 2000 ml (mixer). Every day 30 g of PVC powder was poured into the mixer once. The mixer was connected by another rubber hose to an electric blower. Wien the blower was switched on, the PVC powder was mixed with air. Then using the outg ing rubber hose, the PVC-air mixture wes led into the chamber where the nlmals were. The concentration and size of the PVC dust particles were monitored with a Zeiss conioBater during exposure to the action of the dust. At the start of the experiment, on average about 9000 dust particles were found 3 in 1 mm . As time passed, this figure gradually fell, ms follows (figures given after rounding off): 7000 dust particles after 15 minutes, 5000 dust particles after 30 minutes and about 1000 dust particles in the final phase of dust exposure. The size of the dust particles was as follows: small r than 1 wo - 1Z, lass than 5 ym - 92%, from 5 pm to 10 pm - 4Z, larger than 10 pm - 3Z. The concentration by weight was 97 g/m^. After exposure to the dust for 1 hour the rets were put beck in the cages, where they remained for the rest of the time. The control group of animals was placed in the chamber for 1 hour every day* and movement of air was created with the aid of the electric blower, but PVC was not introduced. All the animals vara killed by decapitation. ucc 065202 Fr eaeh animal lung segments wara taken from the perihllar and subpltural region for mlerosc pie Investigation. The sagnants taken vara fixed In Camoy fluid, embedded in paraffin blocks and stained: hematoxylin and eosln, orcein according to Welgert's method for elastic fibres, accord ing to Goaorl's method for argentafflne fibres, according to Heldenhaln's modification of Mallory's method (with "assn") for collagenous fibres, according to Turnbull's method for divalent Iron and Peris' method for trlvalent iron and with mudcarmln for the presence of mucus. In additl n the following histochemical tests were effected: paS for neutral mucopoly saccharides (supplementing it with control acetylation according to Gersh and employing blocking with dimedon), trlpaS for acidic protein end Male's test for acidic mucopolysaccharides. In addition, atalnlng with xoluldlne blue at pH 3.4 and 5.6 was effected for the purpose of investigating metachrocasia and detection of mast cells. Polyvinyl chloride, designated by the symbol ED, was obtained from the Zaklady Chemiczny (Chemical Works) In Ofwifcir.. The results of the microscopic investigations relate to lung segments taken exclusively from animals that were killed at the scheduled tine. IV. RESULTS OF INVESTIGATIONS 1. CONTROL-GROUP Macroscopic picture. The animals in this group were killed at 4-monthly Intervals. On dissection, in all the rats the lungs collapsed slightly after opening the thorsx, and they were pele pink and airy on the external surface and on section. During cutting they crackle in the characteristic ucc 065203 x- way. K bronchiectasis and no nodular foci vara found in tha lungs f chasa animals. Mlcr scoplc nletura. Tha pulmonary alvaoli ara fairly regular, tha Interalveolar sapta ara of identical thickness with occasional slander elastic fibres (orcein staining). Around the thin-walled capillary vassals in tha interalveolar sapta wa observed soma' lymphocyte-like calls (Fig. 1). * Tha basement membrane of tha capillary vassals contains slender thread-like collagenous fibres (staining with Azan) and slander argentaffins fibres (staining by Comori's method), but do not contain paS-posltive bodies, and stain yellow in the tripsS test. The lobar bronchi are lined with simple cylindrical epithelium, which is multlrowed with occasional beaker cells, and the ciliary apparatus 1 retained. In the cytoplasm of the beaker cells there are occasional, extremely minute mucus granules (staining pink with mucicarnin) and als paS-positive bodies (staining reddish-violet). Neither the cytoplasm f the cylindrical cells nor of the beaker cells contains acidic mucopoly saccharides (Bale's test proves negative). In the wall of these bronchi the muscle fibres run across circuitously in bundles and are separated by collagenous fibres (staining with Azan). The elastic fibres also run circuitously, slightly undulating (staining with orcein), and argentaffine in the form of tanglus (staining by Comori's method). Furthermore, In the wall of the bronchi there are a few lymphocyte-like cells and histl cytea. In the submucous membrane wa can obsarve occasional glandular tubas with narrow luoah, containing ntither mucus nor mucopolysaccharides (staining with mucicarnin; paS, tripaS and Bala's taata prova negatlva). The lumen of the segmental bronchi and bronchioles is lined with eyllndric calls, but basksr calls ara not found among them (Fig. 1). The cytoplasm of the eyllndric cells stains yellow in tha tripaS test and does ucc 065204 not c ntain any granules: nalehar of mucus, nor f mueop lysaccharldcs (staining with mudcarmln and tha paS and Hal 'a tests prove negative). The wall of the segmental bronchi has structure similar to the lobar bronchi. Ko phagocytes with granules of haemosiderln were found in the cytoplasm in the rats of the control group. Occasional mast cells appear under the pleura (having fine-granular, reddish-violet cytoplasm when stained with toluidinc blue). 2. CROUP I. EARLY CHANGES (HATS Nos. 1-16, PERIOD OP EXPOSURE 70 DUST - A MONTHS) Among the 16 animals in this group, 2 rats (Nos. 1 and 2) died at the start of the 4th month of experiment. Pulmonary emphysema and a con siderable degree of passive congestion are found id all internal organs n dissection. A further 2 rats (Nos. 3 and 4) died in the last days of the 4th month of exposure to the dust. The macroscopic picture was similar to thot of the 2 previous rats. The surviving 12 rats (K6s. 5-16) were killed at 1-month intervals (3 rats at a time). Mnrronconlc picture. After opening the thorax, in all the rats of this group the lungs do not collapse but fill the whole thorax, and they are fluffy and pale. During cutting, they do not crackle as characteristically as normal lungs. On the cut surface they ere pale pink end dry. A small quantity of mucous mass is discharged from the large bronchi on compression. Microscopic picture. The pulmonary alveoli arc inflated like ball ons, the septa between them are of reduced thickness, are disrupted in plac s, as a result of which there is formation of large cysts, and the residues f the septe pr ject In the form f spines int their lumen. In the first ucc 065205 few months f experiment the lnteralve lar septa are f und to have aggregates f histl cyte-like cells, the cytoplasm of which possesses minute, diffuse golden-brown granules f haemoalderln containing trlvalent Iron (they stain greenish-blue secordlng to Peris' method. Fig. 2). Sometimes In the vicinity pf the blood vessels in the locally thickened Interalveolar septa there are aggregates of cells of this kind, profusely charged with haeoosiderln (Fig. 2). Towards the end of the 4th month of exposure to dust, cells with haeoosiderln granules are seldom found. However, thicken ing of the septa persists. In the first few months of this period the lobar bronchi, lined with cylindrical epithelium, have an irregular lumen. On the surface of the epithelium there are scant, amorphous, pink mucous masses (which stain pink with mucicarmin), containing minute granules of mucopolysaccharides (which stain reddish-violet in the paS test). Between the cylindrical cells there are occasional beaker cells, the cytoplasm of which contains mucus (which stains pink with mucicarmin) with a few, fine granules of neutral muc poly- saccharides (staining reddish-violet in the paS test). In the final phase of this period of the investigations the lumen of the lobar bronchi becomes roundish. * In some places the cylindrical epithelium undergoes flattening, and in some places there is even complete destruction (Fig. 3). This destructl n is not restricted to the epithelium, but affects deeper layers of the bronehus. Between the lymphocyte-like cells filling such a defect in the bronchial wall there ere no elastic fibres, or they have undergone frag mentation and have the form of fine, very thin brown filaments in rceln staining. On the other hand the argentaffine fibres undergo thickening r fragmentation as well (staining according to Coaorl's method). The rather *aall number of lymphocyte-like cells in the wall of the lobar bronchi in ucc 065206 the initial phase increases a* time passes, and by the end of the f urth month such cells are quite numerous. In this period there is also an Increase in the number of beaker cells among the cylindrical cells of the epithelium of the lobar bronchi (Fig. 4). The cytoplasm of the beaker cells contains mucus In the form of spherical pink granules when stained with muclearnln. The composition of this mueus Includes neutral mucopolysaccharides (staining reddish-violet In the paS and trlpaS test). Ihese granules are located in the basal part of the beaker cells, near the nucleus. In addition, the cylindrical cells lining the lumen of the lobar bronchi undergo mucous degeneration and exfoliate int the linen of these bronchi, which Is filled with mucous mass (Fig. 5). The mucous masses mentioned above are stained pale pink by muelcamin, but the paS and trlpaS test proves negative. In the submucous membrane there are occasional glandular tubes, which have a narrow lumen end contain neither mucus nor mucopolysaccharides (staining with muclcarmln, and the paS, trlpaS and Kale's tests prove negative). In the initial phase of the period of investigation, with staining with Azan, a small nunber of slender, bluish collagenous fibres ere noted In the vail of the lobar bronchi. The reddish-violet striae of muscle fibres are fairly wide in comparison with the control group. By the end of the f urth month, here and there the bluish collagenous fibres In the wall of the lobar bronchi have become "scattered", and nearby there are agglomerations of lymphocyte-like cells. On tht other hand the muscle fibres are tumefied. The vail of the blood vessels located near the lobar bronchi has focal thickening as a result of considerable swelling of the muscle fibres, which is revealed by intense reddlsh~violct coloration in staining with "Azan". However, the adventitia appears as a very thin blue stripe. In places in the wall of these vessels we can see small amorphous, violet calcic lamellae. uce 065206.01 In the peripheral part of the lung Juat under the pleura, ar und the capillary vess la with softened and thickened wall, we can detect "cuffs** with nusier us snail, r unded cells with a dark nucleus and a narrow fringe of eytoplasm (Fig. 6)* The endothelium that was tiaefled at the start exfoliates Into the lumen of the vessels in the final phase, and sobs times closes It completely. The cytoplasm of the cells lining the lumen of the segmental hr nehl and bronchioles, which for the most part Is not widened. Is not found t contain granules of mucus, neither after 1 nor after 4 months of dust exposure. Also no beaker cells appear between the cylindrical cells f the epithelium of these bronchi, as of the bronchiole*.. In this period f the investigations, under the pleura we observe e few. Isolated mast cells, which have reddish-violet, fine-granular cytoplasm In staining with toluldlna blue. 3. CROUP II. LATER CHANGES (RATS Nos. 17-38, PERIOD OF EXPOSURE TO DUST - 8 MONTHS) Among the 22 rats in this group, 2 died (Nos. 17 and 18) In 6 months of exposure to FVC dust. On dissection they were found to have pulmonary emphysema and bronchlectasla in a suppurative stete, end in e further 4 rate whleh died In 7, 8, 9 end 10 months of exposure to the dust (Nos. 19-22) there were small, scattered foci of suppurative pneumonia. Two rat died in each of the 11th and 12th months of exposurs to the dust (Nos. 23-26) ss e result of bronchlectssla and pulmonary suppuration. The surviving rats were killed in two's st monthly Intervals, starting from the 5th month of observation. ucc 065207 Macroscopic picture. In the rats aftsr 5 and 6 months of xposura to th* dust (N a. 27 to 30), after ptning the thorax the lungs do not collapse but protrude from Che thorax, they are nodarately fluffy but do not crackle during cutting as markedly as normal lungs. Minute slate-like specks show through the "pleura. On cutting the lungs are pale pink, and dry. Br nchl with widened lumen protrude from the cut surface, and on compression the * ropy contents are discharged from them. In the lungs of rats after 7, 8, 9 and 10 months of observation we found nodular foci protruding above the surface, which had a honeycomb appearance on the cut surface. These f cl contain a ropy, milky-opalescent fluid. In addition to these foci there vert large formations, with the features of single-cell cysts filled with mucoatheromatous mass. These large cystold formations were surrounded by a distinct undulant reddish fringe. Sometimes the cystold formations were so large that they occupied the entire lobe of the lung. In rats after 11 and 12 months of exposure to FVC dust the nodular foci had enlarged to such an extent that sometimes they occupied the entire lobe. On the other hand there were fewer large cystold formations, and they were also smaller. Microscopic picture. Marked pulmonary emphysema Is noted, more pro nounced than in the animals of group I. Howevsr, In places the Interalveolar septa are thick, and the blood vessels in them have Irregularly thickened wall and tueafled endothelium. In the wall of those vessels, after 9 months of exposure to the dust, collagenous fibres appear instead of the muscle fibres, which is Indicated by blue coloration of the vessel vails as a result of the action of Azan and orange coloration when the trlpaS test la carried out. Cuff-llke aggregations of lymphocyte-like cells and histiocytes are observed around these vessels. Sooatlmes these aggregations are connected to the aggregations of such cells around the segmental bronchi, forming a single complex. The 1 bar bronchi have a widened lumen nd ere filled with UCC 065208 mucous mini With numerous granulocytes submerg d la them. Th nuc us masses give a strongly p sltlvs psS rssetl n (latsos* rsddlsh-violat staining) and ara elostly adjacent to ths surface of the epithelium. Between the cylindrical cells lining the lumen of these bronchi there are very many beaker cells. Their cytoplasm gives a weak reaction with muclcaruln: pale pink, but the reaction of paS and tripaS is very strong: intense reddish- violet. After blocking with dimedon, there was no change In the col ration of these masses in the paS test. Furthermore, in the cytoplasm of the cylindrical cells there are minute paS-positive granules. As time passes, the collagenous fibres in the wall of the lobar bronchi become thicker thicker (staining blue with Azan), and the elastic fibres undergo fragmenta tion and are visible as short, thin brown filaments (staining with rcein). In addition. In some bronchi there is metaplasia of the cylindrical epi thelium to stratified pavement eplthellua (Figs. 7 and 8). In the immediate vicinity of the bronchi we can see aggregations of lymphocyte-like cells end histiocytes. Sometimes we gain tha impression that the cylindrical epithelium of the lobar bronchi forma In layers r grows in the shape of a tongue deep into the wall (Fig. 9). In 11 and 12 months of exposure to FVC dust, the epithelium of the dilated lobar bronchi is low and flattened. Tha collagenous fibres In the vail of these bronchi have the appearance of thick, broad, uniform blue stripes (stained with Azan). Tha submucous membrane la greatly widened. The glandular tubes located in it ere either dilated like cysts (Fig. 10) and filled with pala-pink contents, giving a weak reaction with muclcarmin, and stronger paS reaction, or have the appearance of solid tubular f ei without a listen, composed of malleolar epithelium (Fig. 8). Sometimes the dilated, cyst-llke tubes are filled with paS-positlvemasses located just under the eetapisStic, stratified squamous epithelium. Into which their / duct is probably set (Fig. 7). ucc 065209 Between these Cubaa wa find quite numerous scattered lymphocyte-like calla and histiocytes (Flga. 8 and 10) and qulca vlda banda f c llagenous fibraa, which acaln blua with Azan. Tha changes deacrlbad abova ara obaarvad atarting from 7 months of axposurc to tha duet. The segmental bronchi undergo dilatation after 8 months of experiment. In this period tha calls of their epithelium undergo flattening, and beaker cells appear between them. The cytoplasm of these beaker calls gives very weak reaccl n j* with mucicarmin, but tha paS test Is strongly positive - there Is Intense reddish-violet coloration of the cytoplasm. paS-poslclve granules also appear in tha cytoplasm of the cylindrical cells. In addition the epithelium nf.these bronchi becomes stratified (Fig. 11), and sometimes even undergoes metaplasia into stratified squamous epithelium (Fig. 12). Then in the Isredlate vicinity we can see aggregations of histiocyte-like cells and occasional bands of hyalinizing connective tissue. As tine passes, the collagenous fibres in the wall of the segmental bronchi become thicker and thicker and have the appearance of broad blue . stripes in staining with Azan. By the end of 12 months of experiment, the collagenous fibres undergo hyalinization (Fig. 13), and the epithelium undergoes atrophy. There is also atrophy of the glands located in tha sub mucous nembrane. Starting from 8 months of exposure to the dust, round some segmental bronchi ve observe profuse cuff-llke aggregations of lymphocyte-like cells. Pathologic changes do not appear In the bronchioles until 9 months f experiment. They result from enlargement of histiocytic and lymphocyte-like cells towards their lumen and intussusception in the vail of the bronchi le in the form of varts. Some wart-like formations are deprived of br nchlal epithelium. As time passes, around the bronchioles there Is accumulation of more and more lysphocyte-llke cells and histl cytes (Fig. 14), which ucc 065210 fill defects In tha epithelium f tha bronchioles (Tig. 15)* The slsstie fibres in the wall of the br nchlolas in dafactive regions undergo dis integration, and when stained with rcein they are visible as slender, short. Isolated brown filaments. The microstructure of the nodular foci with honeycomb appearance, which was found In rats after 7-12 months of exposure to PVC dust, can be described as follows: they contain eystoid formations lined with cylindrical epithelium. In places we can see wart-like protuberances, composed of connective-tissue stroma (thick blue stripes when stained with Azan) e vered with cylindrical epithelium, which creates the impression of focal strati fication or undergoes metaplasia into stratified squamous epithelium (Tigs. 16 and 17). Squamous-epithelial metaplasia of this kind also occurs In e lobar and segmental bronchi. Between the cylindrical cells without cilia there are quite numerous beaker cells, the cytoplasm of which giv a strongly positive paS reaction - it has intense reddish-violet staining. paS-positive masses also fill the lumen of these eystoid formations and are stained pale pink by muclcarmln. However, the large eystoid formations filled with "mashy" masses, in rots with the same period of exposure to dust, have a different microstruc ture. These are large thin-walled cavities, end the well Is composed of hyallnlzed connective tissue, without epithelial ependyma. In the lumen f these cevlties there ere amorphous, fine-granuler masses, end granul cytes ere only seen among them in a few pieces. Hsle's test proved negative in ell the animals. The number of mast cells, the cytoplasm of which is stained reddish-violet by toluidlne blue, does not increase; only e few f them arc encountered under the pleura or near the dilated bronchi. The granules in the cytoplasm of the phagocytes, located in the lnteralvc lor septa near the blood vessels, contain neither divalent nor trivalcnt iron (staining according t the method of Turnbull and Tori* prove* negative). ucc 065211 A 4. CROUP III. CHANCES AFTER CESSATION OF EXPOSURE TO PVC DUST (RATS Nos. 39-60, OBSERVATION FROM 1 TO 8 MONTHS) Of the 22 rsts In this group, by ths end of tha first month of observation after cessation of exposure to PVC dust, 6 rats died (Nos. 39 to 44). Upon dissection, in the lungs of all the rats in addition to emphysema and bronchiectasis we detected the presence of numerous nodular or cystold formations filled with thick, creamy, ropy contents mixed with "mashy" masses. Sometimes the entire lung was composed of thin-walled, cystold formations. The surviving 16 rats (Nos. 45-60) were killed at monthly Intervals (2 rats at a time). Macroscopic picture. .Among the surviving 16 rats, during dissection of 8 animals killed at the scheduled time we determined the presence of apneusatie, fine-lobular, hard nodular foci (Fig. 18), as in the lungs of the animals in Croup II. In addition, we observed large, quite soft cystold formations (Fig. 18), and when cut they were found to have a thin wall and were filled with "mashy" masses mixed with mucilaginous, partially creamy contents. The changes described above were observed in rsts both 1 month and 8 months after cessation of exposure to the dust. In the other 8 rats, after opening the thorax the lungs do not collapse, they are excessively fluffy, pale pink, and during cutting they do not crackle as characteristically as normal lungs. Tha surface of the cut is pale pink, and dry. Bronchi with widened lumen and roller-shaped wall project from the cut surface. Mucila ginous contents are discharged from them on compression. Scattered slatelike and dot-like foci show through the pleura. Microscopic picture. Pulmonary cmphyscea is found in all the animals in this group, chough with less intensity than in the rats of Croup It. As time pass s, blood vessels surr unded by s cuff f lymph cyte-like cells VJCC 065212 arc observed less sod less frequently In the Interalve lar septs. In the eighth month of observetlon sfter the end of the experiment, only Is lsted lymphocyte-like cells ere to be seen sround the bl d vessels. The lumen of these vessels Is brosd, the endothella ere flattened. In the wall ve can see thinner (in comparison with Group II) -thread-like blue collagenous fibres (staining with Azan). The lobar bronchi have a much widened lumen and f r the most part filled with coagulated albuminous, acidophilic fluid, with numerous neutrophilic granulocytes. The albuminous fluid contains mucus (distinctly pink in staining with mucicarmin) and a much smaller amount of paS-positive substances in comparison with group II (in the paS test it is pale reddish-violet). These bronchi are lined by a low cylindrical epithelium with numerous beaker cells, 1 month after cessation of exposure to the dust. Minute paS-positive granules appear in the cytoplasm of the cylindrical cells. As time passes there is a gradual decrease of the number of beaker cells, and there are only Isolated ones by the end of 8 months f observation. Ac first the cytoplasm of the beaker cells contains very little mucus (it is stained pale pink with mucicarmin), but a large amount f paS- positive substances (it is stain* ed Intense reddish-violet). However, by the end of observation there is a pronounced mucus reaction, whareas the paS reaction is weakly positive (staining pale reddish-violet). At this time the minute paS-positive granules also disappear from the cytoplasm of the cylindrical cells, and their squamous-epithelial metaplasia is rarely encountered. In two rats (Kos. 59 and 60) killed 8 months after cessatl a of exposure to the dust, it was found that there were numerous greenish-blue granules of acidic mucopolysaccharides (Hale's test) in the cytoplasm f the cells of the epithelium of the lobar and segmental bronchi and also In the glandular tubes of the submucous membrane of these bronchi. Similar granules were present in the epithelium of the microlobular nodular foel. Hale's test pr veJ negative in the chef animals. ucc 065213 The c llagenous fibres in the wall f the lobar bronchi are chick, homogeneous, and stain dark blue with Azan throughout the period f observa tion. Staining according to Comorl'e method indicates inspissatlon of argentafflne fibres - thick black bands. On the other hand there are fev elastic fibres, in the form of thin, discontinuous brown threads (staining with orcein), or they are completely lacking in the regions of defects In the bronchial vail. The submucous membrane is vide, in it there are numerous glandular tubes with a vide lumen, filled with contents giving a weak reaction with mudcarmin, and strongly paS-positive (staining intense reddish-violet), hetween the glandular tubes there are extremely numerous lymphocyte-like cells. After 5-3 months from the time of cessation to exposure to the dust, the lumen of the glandular tubes seems to collapse. Cells of new connective tissue and numerous collagenous fibres appear between the tubes (with Azan, staining in the form of broad blue bands, which surround these tubes) (Fig. 19). In places the connective tissue grows as broad bands, and between them there are numerous lymphocyte-like cells and histiocytes, either scattered or in aggregates. Among the bands of connective tissue there are argentaffine fibres (staining black according to Comorl's method), and there are no clastic fibres (staining with orcein). Some glandular tubes are enlarged In cystoid manner and filled with pale pink, homogeneous masses, giving a weak positive reaction with mudearmin (they stain pale pink), and negative pr.S reaction (they do not stain). One month after cessation of dust exposure, the rounded or oval lumen of the segmental bronchi is lined with cylindrical epithelium with Quite numerous beaker cells. Indicating excessive secretion of mucus. This mucus contains a large amount of neutral mucopoly saccharides (Intense raddlsh-violet staining In the paS reaction). Thar arc ol;u> minute paS-positive granules in the cyt plasm f Che cylindrical ucc 065214 / ." . cells. A broad band f flbr sing connective tissue is evident in the wall of the segmental bronchi (stains blue with Azan, and black according t Gomori's method) (Fig. 20). As time passes, in the epithelium of the segmental bronchi there la a fairly rapid decrease of the number of beaker cells containing paS-p sltlve . bodies; these cells are no longer visible 4 months after cessation f exposure to the dust. At this time the minute paS-positlve granules als disappear from the cytoplasm of the cylindrical cells. Fight months after cessation of dust exposure, the broad band of connective tissue Is still present In the wall of the segmental bronchi and does not display signs of hyalinizatlon. Between the cylindrical cells of the epithelium, the cytoplasm of which is stained yellow in the trlpaS test, only isolated beaker cells are visible, with their cytoplasm containing mucus (stainspink with muclcertain), but not containing paS-positive bodies. In 1 rat (No. 53) ve observed several segmental bronchi alongside one another with cystold enlargement, which were lined with considerably flattened epithelium. Around these bronchi there was growth of fibrous connective tissue, still containing quite a number of lymphocyte-like cells and histiocytes^ The lumen of these bronchi is empty. The pulmonary alveoli in the vicinity of these enlarged bronchi are apneuoatlc, often copiously infiltrated with granulocytes, sometimes occupying some 10-20 alveoli each. Decay is found in the centre of thess infiltrates. In all tha animals vs observed slight, gradual decrease of the number of lyapltoeyte-llke cells surrounding these bronchi like a cuff. By the end of the experiment (in 12 months of sxposure to ths dust), numerous histio cytes and lymphocyte-like cells had accumulated round the bronehl les, t such an sxtent that in places they lntussus'cepted the vail of the br nchi le In the form of a wart. Two months after cessation f dust exposurs, ths above-rationed cells arc still suit Iplyir.;: and now intussus.-ept the vail ucc 065215 of the br nchlolee in numer ue plec s (Fig. 21). Among th lymph eyte-like cells end histiocytes there ere oecsslonsl thin collagenous fibres (they stain blue with Azan and brown according to Coaorl's method). After 7 months from the end of the experiment, the lumen of the bronchioles is markedly constricted and distorted as a result of intussusception of the wart-like formations described above. In their subepithellal layer the connective tissue undergoes hyalinlzation (stains a uniform blue with Azan), and the surface is partially covered with flattened epithelium. In addition to the changes described above, 1 month after cessation of exposure Co the dust we may. find, bands of partially fibrosing connective tissue around some bronchioles, with lynphocyte-like cells and histi cytes between these bands (Fig. 22), or profuse aggregations of lymphocyte-like cells filling the defect in their wall. Four months after cessation of the experiment, sometimes the bronchioles have an irregular, stellate lumen and are lined with low epithelium (Fig. 23). Into these bronchioles there is intussusception of bands of connective tissue containing collagenoue fibres (staining blue with Azan) and argentaffins (staining black according t Goaori's method). Moreover, we often observe proliferation of connective- tissue fibres (staining blue with Azen) in the vicinity of the bronchiole . By the end of 8 months froo cessation of the experiment, the picture is similar, but the new connective tissue gradually transforms into fibrous tissue (uniform dark blue staining with Azan). The mlerostructure f the mlcrolobular nodular foci, observed both 1 month and 8 months after cessa tion of exposure to FVC dust, is similar to that described in Group II, and the lumen of these cystoid formations is filled with granulocytes immersed in mucus, which is stained pink with muelcarvin. However, the mlerostructure of the large, soft cystoid formations and their contents are the same as described in Croup II. ucc 065216 In the first month f bservatlon after cassation of axposurc t the dust* undar the plaura there is accumulation f* in each case* a few r about a dozen large phagocytes with scattered golden-brown* minute granule in the cytoplasm. These granules do not give positive paS and trlpaS reac tion* do not stain with mudcarmln* and also do not contain divalent or trivalent iron (staining according to the method of Turnbull and Peris). Only toluldlne blue stained them golden-yellow. The appearance of fibro blasts and occasional very thin collagenous fibres (filaments staining blue with Aran) between these phagocytes was only determined after 8 months of observation. Throughout the period of observation the asst cells behave as la Croup XI. V. INTERPRETATION OF THE RESULTS AND DISCUSSION The results obtained in my investigations indicate that FYC dust is not a physiologically neutral compound. Long-term inhalation of it leads to the development of a variety of pathologic changes In the respiratory apparatus. At the earliest* after just one month of exposure to this dust* there is development of cetarrhal inflammation of the lobar bronchi with mucoid degeneration of the cells of the epithelium and focal pulmonary emphysema. The development of focel emphysema even in the first month f exposure to PVC dust dapenda moat probably on mechanical obstruction f the small bronchi in the form of a valve. The muscle fibres end collagenous fibres of the bronchlsl vail undergo tumefaction* end the lymphatic f Hides undergo focal hyperplasia. In this period the segmental bronchi es well as the bronchioles do not exhibit catarrhal lesions* but the basement membrane f the capillary blood v ssels in the interalveolar septa undorg es ucc 0652^ X compounds have been explained by Oppenhelmer *t *1. [90]. They e nslder that free radicals ara ralaasad and react with the call constituents. These free radicals repeatedly lead to depolymsrlzatlon of nucleic adds and so have an Influence on the enzymatic processes of the cell. Bedrl et al. (cited.by Homrovski [43]) and Kowalski at al. [67] demonstrated that If dlbutyl phthalate Is used as a plasticizer In the production of PVC, the finished PVC has marked toxic properties, probably as a result of Insufficient polymerization. The investigations of Novak [86] and Bober [8] showed that dlbutyl phthalate can cause inflammatory reactions. However, Smollk 1108] considers that the toxic properties of vacroaolecnlar compounds are associated with monomer -residues. In his opinion they cause, acuta and chronic disorders of the respiratory passages. On the basis of ay rastareh I cannot say with complete certainty whether the PVC molecule undergoes depolymerization and becomes associated with protein, or whether free radicals react with the constituents of the serous fluid of the bronchi, or whether the residues of monomers perhaps exert en action. It is a fact, however, that postpositive bodies sppear in the cells of the epithelium of the bronchi, in their lumen and in the bronchial glands under the influence of PVC Uu.-iC, and the number of such bodies increases as time passes. Aft r exposure to the dust has ceased, the paS-positive bodies gradually disapp at This might indicate that PVC dust irritates the bronchial epithelium, causes en Increase of the number of beaker cells and promotes their secre tion. This-secretion does not have the typical natur* of mucus (slightly positive result of staining with muelcarmin), but it contains psS-positlv bodies. This is emphasized by the fact that with the passage of experiment time, this secretion becomes more and more deprived of the constituents that are characteristic of mucus (staining with muelcarmin is almost nega tive), but it c stains more and more paS-posltlva bodies. After cessatl n ucc 065218 X. f exposure to FVC dust, the paS-positive bodies disappear quits quickly fr a this secretion, and tha constituents that are characteristic of mucus appear instead (staining with nucicarmin is strongly positive). It is significant that FVC administered perorally does not cause any syaptoas of toxic lesion of internal organs (Homrovski at al. [46, 49]). Research by Hervioux, Tessier [45] and Truffert [118] showed that macromolecular coopounds that are derivatives of vinyl possess toxic properties. Toxie action of polyvinyl chloride is Indicated by investigations of the liver of rats exposed to Inhalation of FVC dust, undertaken by Cylvlk [18]. In addition to far-advanced degenerative lesions of the liver cells and reac tive hyperplasia of the cells of the reticuloendothelial system, he noted that paS-positive bodies appear in the liver cells during the experiment, but disappear when exposure to the dust ceases. Appearance of paS-p sitive bodies in the bronchial epithelium and in the lymph nodes of test animals exposed to polyvinylpyrrolidone dust (a vinyl derivative) is also described by Lousma et al. [74], who also note that these paS-positive bodies are also found in the lymph nodes of people employed in the production of this polymer. The reports of Lachnlt [71] and Lefaux [72] show time nontoxic cacronolecular compounds administered perorally may prove highly toxic n Inhalation to the respiratory system. It seems that polyvinyl chloride can be included among the macromolecular compounds with such properties. Comparing tha morphologic pictures in coniosis caused by FVC dust with the pictures of conloses that have already been described, it must be stated that the changes produced by polyvinyl chloride dust ere somewhat similar to the changes In berylliosis, though to s slight degree. This ' comparison is based on identical cells in the inflammatory Infiltrates, however, in berylliosis thert is formation of granulomatous nodules, but pronounced grnnul mas were n t observed In FVC coniosis. In FVC coniosis UCC 0652A9 X / Chickening end ftaning, end the endochellel cells undergo Cuaefeccl n. Around the blood vessels there Is eccumulstion of lymphoeyce-lika cells, which surround then like e cuff. Here end there in the lncerelveoler septs neer the blood vessels we encounter lsolsted or smell groups of phsg cytcs, ** leden with-granules of pigment contelnlng trlvslent Iron. After 2, 3 end 4 months of exposure to the dust we observe greeter dllstetion of the lumen of the lober bronchi end Intensification of the degenerative changes of the epithelium than after 1 month. The muscle fibres of the bronchial well are more thickened end swollen than after 1 month, whereas the collagenous fibres undergo disintegration. Development of defects was observed In places in the wall of the lobar bronchi. Than in this region there wes intensive proliferation of lymphocyte-like cells and histiocytes, which filled the defect. In this stage of the experiment, lymphocyte-like cells accumulate in large foci around the segmental bronchi. The epithelium lining the segmental bronchi and bronchioles maintains its height, but it is covered with a thin layer of mucus. In this period we did not observe accumulation of lymphocyte-like cells near the bronchioles. However, they surround small blood vessels in the Interalveolar septa like a cuff. The excessively-inflated pulmonary alveoli exhibit the typical characteristics of tmphysema. On the basis of the picture of pathologic changes In the first 4 months of exposure to FVC dust It can be stated that PVC dust reaching the respl- ratory system causes mucoid catarrh of the lobar bronchi and pulmonary emphysema in the early stage. Aa time passes, mucoid degeneration gradually affects the segmental bronchi end bronchioles, but Is only slight. In parallel with the degenerative changes in the bronchi, we observe e marked reaction on the pert of the lymphatic system. Lymphocyte-like cells accumulate n t nly around the blood vessels in the Interalveolar septa, V.it nV - in the bronchial wall. ucc 065220 Among the changes bserved In animals exposed to PVC dust fra further 8 months on top of the first schedule, hyperplastic and metaplastic lesions appear, in addition *o intensification of the degenerative changes. They affect the epithelium of the lobar bronchi and of the segmental bronchi, and even appear in the epithelium of the bronchioles. Against a backgr und * of hyperplastic lesions of components of the bronchus, there Is development of cystoid foci, with wart-like protuberances covered with cylindrical or squamous epithelium. The epithelium lining these foci exhibits muc id degeneration. The excessive quantity of mucus accumulates In the linen of Chase wart-like foci, often there is secondary Infection, which leads to suppuration. The microscopic picture of these foci is similar to the pic ture of a eystoadenoma. In the vail of the lobar and segmental broncbl, with widened lumen, wc find broad bands of connective tissue with lymphocyte-like cells between Its fibres. The muscle fibres in the wall of these bronchi undergo atrophy. The resulting dilatation of the bronchi often leads to secondary infection. Then their lumen Is filled with mucopurulent fluid, and the epithelium undergoes atrophy. In the final stage of exposure to the dust, l.e. after 12 months, granulocytes and histiocytes accumulate around the bronchioles. S oetimes the granulocytes and histiocytes intussusccpt the wall of the bronchi les like warts Into the lumsn, distorting and constricting It. There is often mucus with granulocytes in the lumen. Pulmonary emphysema, developing in the initial period of axpoaure to the dust, most probably depends n mechanical obstruction of the bronchi. The emphysema Increases as time passes. Its development In the later stage is associated with degenerativelnflatnatory lasions in the bronchi and bronchioles; large bullae f ra, in which an exudate accumulates, mainly composed of neutrophils. The vsi's ucc 065221 of the number of beeker colls In tbo vuc us membrane of these bronchi end decline of metaplasia f the pavement epithelium. Metaplasia of the pavement epithelium deserves further consideration. In the rats of Croup II this metaplasia was very pronounced. In Croup III, however, either It was not very marked, or It was completely absent. It would be difficult to accept that the 16 rats in Group III would react so very differently to exposure to PVC dust, l.e. that their reaction charac- teristics would differ markedly from the reactivities of the rats in Group II. I assume that in these animals, which after all are derived from Inbreeding, there cannot be marked differences in reactions. Then we should amaune that metaplasia of the pavement epithelium alee occurred la the bronchi in these 16 rats, hut after cessation of exposursto PVC dust the oetaplastic epithelium gradually exfoliated and normal epithelium was com pletely restored. The validity of this idea is supported by the fact that there is metaplasia of the pavement epithelium in`8 rats out of 16, though this metaplasia was of a low level of intensity. As follows from 8 months of observation after cessation of exposure to PVC dust, some of the pathologic changes in the lungs recede, but som show no significant signs of receding. It can therefore be concluded that the pathomorphologlc changes in the lungs, produced ss a result of the action of PVC dust, persist even after its action has ceased. Va must then ask what happens to the PVC dust. Is it deposited In the lungs, or la it dissolved in the body fluids? It la not easy to answer this question, f r it turns out that PVC dust probably has the same refractive Index as Canada balsam and therefore it cannot ha detected. Moreover, PVC dust particles do not retain any pigments which are employed in the research. It eould be assumed that these dust particles dissolve In the tissue fluid in the lungs. That this p saibility conn t be rejected is demonstrated by th nhrtorv.-'rtons of Herat 16], Cylwik p..), Ijivlmlt f71 j and rt!.--.;., ucc 065222 Tha results of invastlgstions^f rat lungs aftar axp sura to pv dust indicate that this dust produces lasl ns f the natur of coni sis. Hemes [AO] and Harris [A1J e nsider that the type and nature f the pathoaorphologle changes developing In the lungs during conlosls depend not only n the biological activity of the dust Introduced* but also on the size f the dust particles. Khukhrina [14] proposed a classification of dusts Into 7 types* placing highly toxic dusts in first place. Danlshevskll [19] con siders that primarily macromolecular eoapounds (polymers) are toxic to the a organise. They are precisely characterized by biological activity. Th toxic action of polymers is also reported by Hopkins et al. [50]. The* .authors described poisoning with acrylamide, which took place with symptoms oT toxic lesion of the nervous system. My Investigations seem to show that particles of PVC dust* 92Z of which are amaller than 5 urn* reach tha respiratory system and also have a toxic effect* though an influance also results from their mechanical action* by obstruction of the small bronchi. The toxic action of PVC Is mainly Indicated by dilatation of the bronchi and their suppurative inflammation. According to Ashbel [2]* development of dilatation of the bronchi and their suppurative inflammation are charac teristic features of toxic conloses* defined by French authors as t xle bronchopathles (Marchand [75]). The mechanism of the toxic action of macromolecular compounds was explained by Hueper [51] In the following way: aftar coming in contact with body fluids s maeromolecule stay undergo degradation (depolymerization - my comment) and than be Incorporated in protein of nucleoprotelns ea pathologic granules. A new polymer-pro tain combination la formed* which may have toxic properties. On the other bend* Fltzhugh [26] easoeiatea tha toxic action of polymers with free radicals* being tha residues from Initiators. These groupe are able to combine with protein. The resultant combination la toxic and can even cause tissue t undergo neoplastic pr Ilferstion. Such toxic pr pcrtics of macromolecular ucc 065223 of those large bullae undart fibrosis, and than hyallnlxstl n, and tha axudate accumulated In their lumen undertoes dee mp sltlon ("meshy" mess s). In addition to the hyperplastic and metaplestle lesions of the epithelium. In this period ve also observe frovth of the glands in the vail of the lobar bronchi. Npw solid glandular foci develop, containing high epithelium or typical glandular tubes. Then some of these tubes underwent eystold dilatation. In their lumen we detected mucus containing neutral mucopoly- t saccharides. Between the glandular tubas there were disseminated inflamma tory cells, such as lymphocytes and histiocytes. On the basis of analysis of the microscopic Images of the lungs of animals exposed to polyvinyl chloride dust from 5 to 12/months It can be stated that rhe pathologic changes produced In this time are more Intense than after 4 months of exposure to the dust. During exposure to the dust from 5 to 12 months, bronchiectasis develops, with proliferation and meta- * plasia of the bronchial epithelium. These lesions, are often supplemented by an inflammatory reaction, which affects not only the dilated bronchi, but also the bronchioles, and sometimes even the pulmonary alveoli. To general lie, this period can be called the hyperplastic-inflammatory stage. The animals In Group III were kept under observation for 8 months from cessation of exposure to tha PVC dust. (The animals In this group had previously been exposed to the dust for 12 months). It was found that despite cessation of exposure to the dust, the pathologic changes in the respiratory system display varied development. Some of them continue developing, but others recede. In the dilated bronchi the epithelium undergoes atrophy, but ths inflammatory process already In progress er und them does not recede. The thick bends of connective tissue in the br nchial wall only undergo partial hyallnlxation, end the catarrhal lesions In the epithelium lining their lumen remain even after 5 months of observation. ucc 065224 In the lumen o a* dilated br nchi there ara copious granulocytes, a metlocs exhibiting signs of decay. The lnflasnat ry pr cess ften also affects the nearee-c pulmonary alve 11. In the wall f the dilated 1 b r bronchi, the lymphecyts-llke cells remain in the form of a fairly vide ridge up o the end of observation. Only, a few glands in the wall of the lobar bronchi undergo atrophy and then connective tissue grows focally between them. Inflammatory Infiltrates mainly of histiocytes also remain in the bronchial wall and between the glandular tubes. The connective tissue around the bronchioles behaves differently. In the first months of observation this tissue grows repeatedly, leading to considerable constrietion of their lumen. It is transformed to fibrous connective tissue only by the end of the 7th month of observation. However, the inflamiatory infiltrates mainly of histiocytes remain between the bands of connective tissue. Moreover, bronchioles in a state of exfoliating catarrh are observed. After cessation of exposure to PVC dust, accumulation of a number of phagocytes with golden-brown granules in the cytoplasm was observed under the pleura. These granules contained neither divalent nor triveleht iron. Toluidlne blue stained them golden-yellow. It follows that these granules are not heemoslderin in the strict meaning of this word. They can be regarded as so-called old haemoalderin, which is not synonymous with true hacaoslderin. My opinion in this matter is confirmed by the result of e stslnlng with toluidlne blue. By the end of 8 months of observation after cessation of exposure to the dust, fibroblasts appear between the phago cytes. The following lesions undergo regression: disappearance of the cuff-like aggregations of lymphocyte-llke cells around the blood vassals in the interalveolar septa, regression of mucoid degeneration of the bronchi disappearance of paS-posltlve granules from ths cytoplasm of the beaker rclli; :*..! cylindrical cell* of tlw* Jpbir and augment.il hron.-M, decrease ucc 065225 there is nclchcr formation of fibrouu-hjMl Ine mmJu]<*k, an 1* .l.:.crvi-d j silicosis, nor formation of ginnt-rrll crnnulorwifi, unJrrKilnj: flhrouU *r>4 atrophy, which are characteristic of nnthmrosln. We altto lt<l nt oh*.rrvi the diffuse fibrosis and hyalinlzatlon that occurs in Aabcntruitn. Aftrr long-term application of FVC dust there is development of atrophic bronchitis like that observed in cement pneumoconiosis. Mention should nlno he made of the differing behaviour of the pathomorphologlc changes In the respira tory system upon cessation of exposure to the dust. In pneumoconiosis caused by polyvinyl chloride the connective tissue in the vail of the dilated bronchi is not cicatrized, and does not hyalinlze around the bron- infiltrates of .lyiaphoeyte-like cells and hir.tloryt-i r'wnl In the vail of the lobar and segmental bronchi. All this indicates a repair reaction. In pneumoconiosis caused by PVC dust, proliferation of lympho- --t cytes and growth of bronchial glands is more intensive than in berylliosis* It follows from all these comparisons that pneumoconiosis caused by PVC dust has a distinct morphologic picture. This is further emphasized by the fact that the pathomorphologlc changes described in the respiratory system in the course of pneumoconiosis caused by polyvinyl chloride dust develop e re slowly. According to Pushin [98], this is typical of dlsaases caused by aacronolecular compounds. Comparing the results of the changes eaustd by PVC dust in the respira tory system of rats, the opinion may be expressed that this dust causes pneumoconiosis of e toxic nature. It is also necessary to discuss the fairly large group of animals which died in the course of exposure to the dust. Pour rats died in Group I - in >U of them, in addition to pulmonary emphysema end bronchial catarrh, we found a marked degree of passive hypereeala in the Internal organs. This might indlcata circulatory insufficiency, probably existing prior to the commencement of exposure to the PVC dust. ucc 065226 . . Lncr * -.".o', under the Influence of the mechanic*; id t xle action *c id led Co the animals' deaths. Ten an is died In Group II. ' spsrt fr a che eigne f circuit' 1 sufficiency we onchiectasis in a suppurative state < ulmonnry suppurati n. six rats died In the first month . " ^station of the action The pathomorphologlc changes in s determined during ere similar to the changes described oup II. All the live survived for a further 7 months- In my opinion the M before the intended time of on can be explained eoce of lesions which were intensii' .er the influence of nyl chloride dust. It would have bee . .cult for me to notice :ing lesions prior to commencement of iperlments. '.owing conclusions can be drawn on -Is of these experiments . , Is of the pathomorphologlc changes prod . i In the respiret ry rats exposed to polyvinyl chloride dust, ,vi chloride dust introduced into the esplratory system is c ,lcally f civa, exerting mechanical on* toxic < ctioa, and producing (he nature of toxic pneumoconiosis xneumoconiotic lesions ere based on: . /elopnent of bronchial catarrh a' chiectasia with the <* earance of paS-positive bodies In the cells of their epithelium, -like hyperplasia of component t* e bronchial wall with o tion f nodular f cl similar to cysiaden mas. ucc 065227 'k * e) multiplication f lymphocyte-like Mils and hlstlocytaa In the bronchial vail and aggregation of thasa calls in tha fora of cuffs around tha blood vassals in tha intaralvaolar septa, d) development of pulmonary eaphysaaa and chronic lnflaaoatlon around tha bronehloli* 3. Development of pneumoconiosis caused by polyvinyl chloride can be ' divided into two stages: catarrhal-degenerative and hyperplasticinflammatory. 4. The pnaumoconiotic lesions develop very slowly, are different from other fcnown conloses and create -favourable conditions for suppurative complications, which mainly affect bronchiectasis. 5. Some of the pathomorphologlc changes in the lungs arising In the c urse of experimental coniosis caused by polyvinyl chloride dust do not display any marked tendency to recede after cessation of exposure to this dust. ucc 065228