Document 2JJ0dwjp3GBQ7je15o5EQ4317

Med. L-woro. 4. 394-407, 1982 Ctirdc* rf* Uwro *'L lametSdna del (worn) WIm San BtrmkM 3, Ulfano, fitly THE RELEVANCE OF THE EXPERIMENTAL APPROACH IN THE ASSESSMENT OF THE ONCOGENIC RISKS FROM FIBROUS AND NON-FIBROUS PARTICLES. THE ONGOING PROJECT OF HIE BOLOGNA INSTITUTE OF ONCOLOGY C. MaJtoni, F. Minardi and L. Morisi L'importanza del metodo sperimentale neila valutazione del rischi oncogeni da particelle fibrose e non fibrose. Progetto in corso dell'Istituto di Oncologia di Bologna. E stato presentato il progetto di saggi di canccrogenicita a lungo termine di particeUe fibrose e non fibrose, organiche e inotganiche, naturali e arti ficial, in atto presso l'lstituto di Oncologia di Bologna. I dati preliminari dimostrano cbe: 1) 1'crionite e l'agente cancerogeno sperimentale piu potente che si conosca per il mesotelio pleurieo del ratto; 2) sul ratto 1'erionite e piu cancerogena per la pleura, e I'asbesto piu cancerogeno pet il pcritoneo; e 3) asbesti di diverse tipo ed origine mostrano nette difierenze neila loro capacita di produrre mesoteliotni del peritoneo, nel ratto. 11 contribute dell'approccio sperimentale nell'idcntificaziooe e quantificazione dei rischi oncogeni di materiali particolati e stato breveinente discusso. In our opinion, there is an urgent and growing need for the oncogenic risk asses sment of the inorganic and organic, non fibrous (amorphous 'and crystalline) and fi brous, natural and man-made particles, pre sent in the work-place and in the general human environment. The avadable data are far from correspon ding to the diffusion, the industrial and com mercial impact and the growing utilisation of the above-cited materials. The problem can be faced both from an experimented and, when possible, from an epidemiological approach. Institute of Oncology - Viale Ercolani, -4/2 - Bo logna - Itdy. Supported in part by EEC, contract No. ENV/ 347/I-(S). Long-term experimental bioassays, in the present situation, may provide different types of important information, i.e. they can: -- identify new potential carcinogenic risks; -- assess, in quantitative terms, the level of risk of a given agent, and compare the risks represented by different agents (as sessment of the relative carcinogenic risks); -- evaluate the possibility of additive and multiplicative effects of simultaneous or random exposures to other agents; -- help to predict the target organs; -- define the role of the physical and che mical characteristics of the test-com pounds, and of different biological and experimental factors which affect neo- 1 Vol. 73. n. 4,1982 EXPERIMENTAL RISKS ASSESSMENT OF PARTICLES 395 plastic response and, consequently, shed some light on the pathogenesis of the possible oncogenic effects; and finally, -- help to reconstruct the natural history of the tumors which may be induced by the test-compounds. A vast and systematic project of interrela ted long-term bioassays on several types of particles, has been started in the experi mental Bentivaglio (BT) Laboratories of the Institute of Oncology of Bologna. At present, the project includes the study of several types of asbestos (Exp. BT 2101), of kaolin, talc, crystalline silica, amorphous silica, alumina, bentonite and carbon fibers (Exp. BT 2102), of several sedimentary na tural zeolites (Exp. BT 2103), of several hy drothermal natural zeolites (Exp. BT 2103), and of several industrial zeolites (Exp. BT 2104 and BT 2103). Each compound is always tested by intraperitoneal injection, and often by intrapleu ral and subcutaneous ones, on groups of 40, 60 or 80 animals, of both sexes. The animals are treated by a single 23 mg injection of the test-compound, in 1 ml of H2O. Only carbon fibers have been tested by subcuta neous route alone (implantation of discs of preg-preg , 2 cm in diameter). Animals treated with H2O serve as controls. The procedures of the experiment are hi ghly standardized. The animals are kept un der observation until spontaneous death, and periodically weighed and controlled during all the experiments. A complete autopsy is car ried out on each dead animal, and systematic histopathology is performed. The plan of the started experiments is shown in tables 1-3. Table 1 - Long-term carcinogenicity bioassays of asbestos of different types and ori gins, by intraperitoneal, intrapleural and subcutaneous injection, on 8 weeks old Sprague-Dawley rats. Size of the experimental groups: 40 rats (20 M and 20 F). Treatment: 1 injection of 25 mg of the test compounds in 1 ml of HO. Duration of the experiments: life-span. Start of experiments: 77 weeks ago(-). 55 weeks ago(**). Exp. BT 2101 Compounds Intraperitoneal Croddolite (UT.CC) (*) Chrvsotile (Canada) (UICC}{*) Chrysotile (Rhodesia) (UICC) (*:) ChrysotiJe (California) (*) AmositeC1) Anthophyllitei*) Asbestos-Cement l ** 1 HiO (Controls) (x) ILO (Controls) (**) 4- 4*r + + + Routes Intrapleural T* -l- + Subcutaneous + + T 4- Total No. of animals: 680. -0 other samples of asbestos of different types and origins will be tested. Vol. 73, n. 4,1982 EXPERIMENTAL RISKS ASSESSMENT OP PARTICLES Table 4 - Long-term carcinogenicity bioassays of various hydrothermal natural zeolites, by intraperitoneal, intrapleural and subcutaneous injection, on 8 weeks old SpragueDawle`i rats. Size of the experimental groups-. 40 rats (20 iVl and 20 F). Treatment: 1 injection of 25 mg of the test compounds in 1 ml of H:0. Duration of the experiments: life-span. Start of experiments: 45 weeks ago. Exp. BT 2103 Compounds Mordenitc Heulnndite Mesolite Natrolite Scolecite Stilbtte Thompsonite HiO (Controls) Intraperitoneal 4+ 44+ 44+ Routes Intrapleural 4- Subcutar + + + + + + 4- Total No. of animals: 640. Several other samples of various hydrothermal natural zeolites of different types and origins will be tested. 397 Table 5 - Long-term carcinogenicity bioassays of industrial zeolites, by intrapcritoneal, intrapleural and subcutaneous injection, on 8 weeks old Sprague-Dowley rats. Size of the experimental groups: 40 (*) or 60 (**) rats (20 or 30 M and 20 or 30 F). Treatment: 1 injection of 25 mg of the test compounds in 1 ml of EhO. Duration of the experiments: life-span. Start of experiments: 55 weeks ago(*). just begun {**). Exp. BT 2104 - Exp. BT2105 Compounds Intraperitoneal Routes Intrapleural Subcutaneous MS 4A (*) ~h + + MS 5A() + 4- + MS 13X() 4- 4- -f* 21s and correlated compounds (correlated compounds (17 sampIcsK**) + *1" f H2O (Controls) (*) 4- IIzO (Controls) (**) 4- 4- + Total No. of animals: 3,640. Other samples of industrial zeolites of different types and origins will be tested- wjaVirJ>TT'-',-v"n 398 MALTONT, MINABDr, MORISI Med. Lavoro The project has utilized 6,580 animals, compound has produced an high onset of so jar. pleural mesotheliomas following intrapleural The study will he extended in the near injection. 21 out of the 22 dead animals future to other types of asbestos, of natural (over 40 treated ones) within 67 weeks died and industrial zeolites, and of carbon fibers, from pleural mesotheliomas, i.e. 52.5% of and to other inorganic and organic particles all treated animals (table 6). (glass fibers, plastic fibers, vegetal fibers, The induced pleural mesotheliomas arc etc.). In particular, a series of 40 samples equivalent to the most frequent sub-istoty- of asbestos of different types and origins will pes of the human ones. Characteristic pictu be tested. The samples are being collected by res are shown in figures 1-7. gently shaking the natural minerals in order These results show that erionite is the to avoid the possible physical and chemical most potent known experimental carcinoge modifications produced by rough manipula nic agent for the pleural mesothelium. tion, which is the common procedure when obtaining sufficient amounts of short fibers 2. Assessment of the relative onco for bioassays. genic RISK OF ASBESTOS OF DIFFERENT After 15 months (67 weeks) three sets TYPES AND ORIGINS of results seems particularly important and prove the utility of the experimental ap proach in helping to clarify some areas of the problem of carcinogenesis from particles. Asbestos of different types and origins, when injected intraperitoneally, show sharp differences in their capability of producing peritoneal mesotheliomas (table 7). l 1. Carcinogenicity of erionite These results stress the need for further studies in order to have a more precise, quan Erionite has been suspected of being afthe titative risk assessment in the area of asbe causative agent of environmental pleural me stos carcinogenesis, and for comparative quan sotheliomas in Turkey (Baris et al., 1979). titative data on the possible carcinogenic po Under our experimental conditions, the tential of proposed asbestos substitutes. Table 6 - Incidence of pleural mesotheliomas in Sprague-Dawley rats treated by a single intrapleural injection of 25 mg of sedimentary erionite in 1 ml of HiO, and then kept under observation until spontaneous death. Results after 67 weeks. Exp. 3T210? ' Compounds Erionite (sedimentary) HtO (Controls) Animals (Sprague-Dawley rats, 8 weeks old at start) Sex M F M+F M M+F No. at start Survivors 20 7 20 u 40 18 20 20 20 20 40 40 Tumours at the site o injection Latency time No. % (weeks) 12 60.0 56 9 45.0 57 21 52.5 56 _0 ____ 0-- ____ 0 -- -- The incidence of mesotheliomas oyer untreated Sprague-Dawley tats of the Institute of Oncology of Bologna, kept under observationuntil spontaneous death (Historical controls) was the following: Peritoneal mesotheliomas :3 out of 1,179 males and 0 out of 1,202 females Pleural mesotheliomas : 0 out of 1.179 males and 1 out of 1.202 females Pericardial mesotheliomas:1 out of 1,179 males and 0 out of 1202 females .oro of ural ;ds lied of arc otyctu- ihe >ge- .cof.NT ins, arp ing her i/jtjbeanpo- n > .1 VoUl n. 4,1982 EXPERIMENTAL RISK ASSESSMENT OF PARTICLES 399 Table 7 - Incidence of peritoneal mesotheliomas in Sprague-Dawley rats treated by a single intraperitoneal injection of 23 mg of asbestos of different types and origins in 1 ml of HiO, and then kept under observation until spontaneous death. Results after 67 weeks. Exp. BT 2101 Compounds Animals (Spraguc-Dawlcy rats, 8 weeks old at start) Mo. Sex at start Survivors Tumours at the site of injection Latency time Mo. % (weeks) Crocidolite Amosite Anthophyllite Cluysotile (California) Chrysotile (Rhodesia) Chrvsorile (Canada) HjO {Controls) M F M+F M F M+F M F M+F M F M+F M F M+F M F M+F M F M+F 20 20 40 20 20 40 20 20 40 20 20 40 20 20 40 20 20 40 20 20 40 3 8 1.3 9 10 19 11 16 27 13 16 29 18 18 36 18 19 37 20 20 40 14 12 26 11 10 21 7 4 11 5 2 7 0 1. 1 l 0 t 0 0 0 70.0 60.0 65.0 55.0 50.0 52.5 35.0 20.0 27.5 25.0 10.0 17.5 5.0 2.5 _5.0 2.5 __ _ --- 50 56 53 59 56 58 53 55 54 55 51 54 49 49 _65 65 ____ -- The incidence of-mesotheliomas over untreated Sprague-Dawley rats of the Institute of Oncology of Bologna, kept under observation until spontaneous death (Historical controls) was the following: Peritoneal mesotheliomas: 3 out of 1.179 males and 0 out of 1,202 females Pleural mesotheliomas : 0 out of 1.179 males and 1 out of 1,202 females Pericardial mesotheliomas: 1 out of 1,179 males and 0 out of 1,202 females 3. Importance of the physical-chemi cal CHARACTERISTICS OF THE TEST-COM POUNDS AND OF THE BIOLOGICAL AND EXPERIMENTAL FACTORS The data reported in table 7 paint out the primary role of the physical-chemicd cha racteristics of the test-compounds in the de termination of their carcinogenic potency. They also underline the need to avoid rough manipulation of test materids which may change their physicd-chemical characte ristics. Moreover, the data obtained at present in dicate that the tumour response (production of mesotheliomas) depends both on the type of the compound and on the exposed serosa (table 8). Erionite, which is the most effica- T able 8 - Comparative incidence of peritoneal and pleural mesotheliomas in Sprague-Dawley rats treated by a single iutraperitoneal and intrapleural injection of asbestos oi different types and origins and sedimentary erionite (25 mg in 1 m l of H ,0 ), and then kept under observation u n til spontaneous death. The experiments are carried out in a strictly standardized way. Results after 67 weeks. >100 MALTONX, MINARDI, MORISl Med. Lavoro 12 ua t iI -a 3 85 tx. S-J fX< tn *"5 + 2 a .2 JSj S a oU 5 to !1 !| *; &etJ iCs5 -a C3 O O O rv j O ir\ O O IT, Op* o'vlAo J>OAOir* <vN\ J v\cdm h(N tfioV v\ | *T\ fN I Tv o v\ 'A <N h- i--i ] \r\ m r*. Oh. OhhIoeo CoN <oN <41 OCN o<v| Q^ is? 38? (oNoMot to sSu.4- & 5^ C5> -f s n< to fn **3 *"3S& + 22 SCL.+ 2 -jj 3 . U 1 TcC3j U to a <o . o c o too CJ u. 'O a aO < a> l1 cs < CJ jj jj o3O _&q 0 ona. _toc V g t.oM2 Ho U O rit Fig. 1 - Pleural mesothelioma from crionite: tubular pattern. H. E. x 200 Fig. 2 - Pleural mesothelioma from erionite: tubular-Dapiilarv pattern. H. - E. x 200 " :i i i < I i1 MALTONI, MINARDI, MORISI AW. Uvoro HS V ^(xf1 mesotiieIioma from erionitc: papillary pattern (serous effusion). ! 1 U?'. e'AoQ111 mesothelioma from ebonite: solid ftrabeailar) pattern. Lavoro Vol. 73, it. 4, 1982 EXPERIMENTAL RISK ASSESSMENT OF PARTICLES 403 Fig. 6 - A detail of fig. 3. H. - E. x 200 Fig. 7 - Pleura] mesothelioma fro--m er.i.o..n..it*e: sDpuinSdtHleScvell type with sarcomatous pattern H. - E. x 200 Fig. 8 - Pleural tubular mesothelioma associated to fibrous nodules and plaques, from erionite. H. - E. x 80 Lavoro Vd. n, n. 4. mi EXPERIMENTAL RISK ASSESSMENT OP PARTICLES -(05 Fig. 9 . Peritoneal fibrous plaque from croddolite: asbestos deposits can be seen within the plaque. H. - E. x 200 Fig. 10 - Peritoneal cellular (active) plaque from croddolite. H. - E. x 80 J06 MALTONT, MIN-Aanr, MOMSI Med. Lavoro Fig. 11 - A detail of fig. 10. H. - F.. x 200 3 ayoro Vol. 73, n. 4, 1982 EXPERIMENTAL RISK ASSESSMENT OP PARTICLES 407 clous in producing pleural mesotheliomas, when injected intrapleurally, has a far lower potency in producing peritoneal mesothelio mas when injected intraperitoneally. The op posite has been observed in the bioassays of different types of the tested asbestos. productive collaborations may take place among researchers concerned with this pro blem, working in experimental laboratories and in epidemiological units. SUMMARY 4. Natural history of mesotheliomas WITH REFERENCE TO PRECURSORS Some early observations of ours show that mesotheliomas often arise in correspondence with and within pleural and peritoneal loca lized fibrosis (plaques and nodules) (figures 3-12). The matter of plaques as precursor lesions of human pleural mesotheliomas is contro versial. The experimental data can help to clarify the role of the plaques as a precursor, and the degree of their potential to undergo mesotheliomatous transformation. We expect that, from the progress and expansion of our project, clarifications may be produced on the carcinogenicity of parti cles with some direct contribution to the most urgent current public health problems, particularly dealing with asbestos and its sub stitutes. Furthermore, we hope that closer, more The project of long-term carcinogenicity bioassays of fibrous and non-fibrous, organic and inorganic, natural and man-made parti cles, which is going on at the Bologna In stitute of Oncology, is presented. The up-to-date results show that: l) erionite is the most potent known- experimental carcinogenic agent for the pleural mesothelium, in rats; 2) on the rat, erionite is more carcinogenic for the pleura, and asbestos mo re carcinogenic for the peritoneum; and 3) asbestos of different types and origins show sharp differences in their capability of pro ducing mesotheliomas of the peritoneum, in rats. The contribute of experimental approach to the identification and quantification of the oncogenic risks of particles is briefly di scussed. REFERENCES Basis Y.I., Artvinli M. and Sahin A_A.: Envi ronmental mesothelioma in Turkey. In: I.J. Selikoff and E.C. Hammond: Health hazards of asbe stos exposure. Annals N.Y. Acad. Sdcnc., 330, 42J (1979). Accettato i! 17/5/1982.