Results of recent experimental research on the carcinogenicity of natural and modified asbestos

Our plain-English summary of Results of recent experimental research on the carcinogenicity of natural and modified asbestos, by F. Minardi, C. Maltoni (Annals of the New York Academy of Sciences, 1988).

The study

• Authors: F. Minardi, C. Maltoni
• Journal: Annals of the New York Academy of Sciences
• Published: 1988;534:754-61
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Long-term experimental bioassays were carried out on natural asbestos of different types and origin (crocidolite, chrysotile, amosite, antophyllite), on asbestos cement, and on industrially modified chrysotiles. The materials were tested on Sprague-Dawley rats by intraperitoneal and intrapleural injection. The experiments were carried out with highly standardized procedures on all materials to enable comparative evaluation of the results. The data presented confirm that asbestos of different types produces peritoneal and pleural mesotheliomas, show that asbestos cement is also mesotheliomatogenic, and demonstrate that the peritoneum is more responsive than the pleura. Furthermore, evidence is provided that the mesotheliomatogenic effects of different types of asbestos vary with the types and origin of the minerals, and that physical and chemical modifications of the natural chrysotile can lower its carcinogenic effect.

In plain English

This was an animal experiment at the Bologna Institute of Oncology in Italy. Sprague-Dawley rats, in groups of 40 (20 males and 20 females), each received a single 25-mg injection of a test material into the abdominal cavity (intraperitoneal) or the chest cavity (intrapleural). The first experiment tested natural crocidolite, amosite, anthophyllite, chrysotile from Canada, Rhodesia and California, and asbestos cement. Every asbestos group developed peritoneal mesothelioma, from 39 of 40 rats (97.5%) for crocidolite to 21 of 40 (52.5%) for asbestos cement. None of 80 water-injected control rats did. Pleural mesothelioma developed in 26 of 40 rats given Canadian chrysotile, 18 of 40 given crocidolite and 14 of 40 given asbestos cement. The second experiment was run with the samples coded and tested chrysotile treated with POCl3 at 300°C. Untreated short chrysotile caused peritoneal mesothelioma in 29 of 40 rats, and the treated version in 3 of 40, the same count as rockwool. Kevlar caused none. The authors concluded that, under their experimental conditions, effects varied by asbestos type and origin and could be lowered by modification. The materials were injected, not inhaled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment: long-term carcinogenicity bioassays in which rats received a single injection of each test material and were observed for mesothelioma. The two experiments reported here were part of a larger testing project.
• Who was studied: Eight-week-old male and female Sprague-Dawley rats at the Bentivoglio Experimental Unit, Bologna, Italy. Groups had 40 rats (20 males, 20 females) per material and route. The intraperitoneal water control group in experiment BT 2101 had 80 rats. The project started in January 1981. Rats were observed until spontaneous death, except in experiment BT 2106, which lasted two years before survivors were killed.
• Exposure: A single 25-mg injection, given intraperitoneally or intrapleurally. Experiment BT 2101 tested crocidolite (UICC), chrysotile from Canada (UICC), Rhodesia (UICC) and California, amosite (UICC), anthophyllite (UICC) and asbestos cement. Experiment BT 2106 tested chrysotiles untreated and after treatment with POCl3 at 300°C: commercial Paperbestos No. 5, Paperbestos fibers extracted from asbestos-latex paper, short chrysotile (Grade 7) and UICC Canadian chrysotile. It also tested rockwool and Kevlar fibers. BT 2106 samples were supplied with only a sample number.
• Main results:
  • Experiment BT 2101, peritoneal mesothelioma after intraperitoneal injection (males and females combined), with average time from treatment to death:
• crocidolite: 39 of 40 rats (97.5%), 59.5 weeks
• amosite: 36 of 40 (90.0%), 66.7 weeks
• Rhodesian chrysotile: 33 of 40 (82.5%), 89.7 weeks
• Canadian chrysotile: 32 of 40 (80.0%), 92.2 weeks
• Californian chrysotile: 29 of 40 (72.5%), 85.3 weeks
• asbestos cement: 21 of 40 (52.5%), 99.7 weeks
• water controls: 0 of 80
  For anthophyllite the table prints 35 of 40 but also 82.5%, which do not match.
  • Experiment BT 2101, pleural mesothelioma after intrapleural injection:
• Canadian chrysotile (UICC): 26 of 40 rats (65.0%)
• crocidolite: 18 of 40 (45.0%)
• asbestos cement: 14 of 40 (35.0%)
• water controls: 0 of 40
  • The authors reported that crocidolite appeared to be the most potent material tested, and asbestos cement the least carcinogenic.
  • The authors reported that the peritoneum responded more than the pleura to asbestos.
  • Experiment BT 2106, short chrysotile (Grade 7):
• untreated (sample 5): peritoneal mesothelioma in 29 of 40 rats (72.5%)
• treated with POCl3 at 300°C (sample 6): 3 of 40 (7.5%)
• neither sample caused pleural mesothelioma (0 of 40 each)
  The authors said sample 6 had by far the weakest potency, in the same range of risk as rockwool.
  • Experiment BT 2106, UICC Canadian chrysotile:
• untreated (sample 7): peritoneal mesothelioma in 30 of 40 rats (75.0%) and pleural mesothelioma in 13 of 40 (32.5%)
• after treatment (sample 8): peritoneal mesothelioma in 20 of 40 (50.0%) and pleural mesothelioma in 0 of 40
  • Experiment BT 2106, Paperbestos No. 5 chrysotile, peritoneal mesothelioma:
• commercial grade, untreated (sample 1): 33 of 40 rats (82.5%)
• commercial grade, treated (sample 2): 17 of 40 (42.5%)
• fibers extracted from asbestos-latex paper, untreated (sample 3): 17 of 40 (42.5%)
• fibers extracted from asbestos-latex paper, treated (sample 4): 15 of 40 (37.5%)
  • Experiment BT 2106, other fibers:
• rockwool: peritoneal mesothelioma in 3 of 40 rats (7.5%) and pleural mesothelioma in 1 of 40
• Kevlar fibers: no mesotheliomas
• water controls: no mesotheliomas
  • Mesothelioma was rare in untreated rats of this breed observed until death (historical controls):
• among 1179 males: 3 peritoneal, 0 pleural and 1 pericardial
• among 1202 females: 0 peritoneal, 1 pleural and 0 pericardial
  • The authors reported that the mesotheliomas showed tubular, papillary, solid and spindle-cell patterns, and often spread to other sites.
• The authors' conclusion: The authors concluded that asbestos of different types and origin causes peritoneal and pleural mesothelioma in this model, and that the peritoneum is more responsive than the pleura. They also concluded that, under their experimental conditions, effects vary with type and origin and can be modified by changing the mineral's physical-chemical properties. In their view, POCl3-treated short chrysotile was by far the weakest carcinogen among the asbestos materials tested.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Amosite, Asbestos-Cement, Pleural Mesothelioma, Peritoneum, Pleura, Carcinogenic.

Related studies

• The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research — J.G. Hogervorst, B.J. Baars, et al. (2010)
• A reappraisal of the carcinogenicity of surface modified asbestos fibres — P. Carthew, R.E. Edwards, et al. (1993)
• Detection of mineral fibre carcinogenicity with the intraperitoneal test--recent results and their validity — F. Pott (1995)
• Experimental studies on asbestos carcinogenicity — L.M. Shabad, L.N. Pylev, et al. (1974)
• Natural fibrous zeolites and their carcinogenicity-a review — K.R. Spurny (1983)
• Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals — P. Huttenloch, K.E. Roehl, et al. (2001)

Browse more research in Annals of the New York Academy of Sciences, or return to medical research.