The use of animal models for studies on asbestos bioeffects

Our plain-English summary of The use of animal models for studies on asbestos bioeffects, by J.M. Davis (Annals of the New York Academy of Sciences, 1979).

The study

• Author: J.M. Davis
• Journal: Annals of the New York Academy of Sciences
• Published: 1979;330:795-8
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This short workshop paper reviewed animal inhalation studies of asbestos to judge which species best reproduces human disease. The author reported that guinea pigs, rabbits, hamsters, gerbils, cats and vervet monkeys developed lung fibrosis but no tumors were reported. Only rats developed fibrosis, bronchial carcinomas and occasional mesotheliomas, though one pleural mesothelioma was apparently found in an unpublished baboon study. Rats rarely form asbestos bodies; the author was unsure whether this matters. The paper also summarized an Edinburgh study in which rats breathed UICC chrysotile, amosite or crocidolite for one year. Both chrysotile groups had more fibrosis than the amphibole groups, and all malignant lung tumors (8 and 2 bronchial carcinomas) were in chrysotile-treated rats. The text said about 7% of chrysotile fibers exceeded 20 micrometres, though the printed table lists more than 20%; amphibole clouds had under 0.5%. The author concluded that the rat is the best available model, and that the data strongly support the idea that long fibers are much more dangerous than short ones. The author said further work is needed on whether fibers under 5 micrometres are harmless.

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: Review and commentary (workshop paper) on animal models for asbestos research, including a summary of the author's group's earlier rat inhalation study (Davis et al. 1978)
• Who was studied: Published inhalation studies in rats, guinea pigs, rabbits, hamsters, gerbils, mice, cats, vervet monkeys and baboons, plus rats in an Edinburgh inhalation study (number of rats not given in this text)
• Exposure: Various asbestos types in the reviewed studies. In the Edinburgh study, rats inhaled UICC chrysotile, crocidolite and amosite for one year: all three at 10 mg/m3, plus chrysotile at 2 mg/m3 and crocidolite at 5 mg/m3, so that fiber numbers matched the amosite cloud
• Main results:
  • Of the species reviewed, only rats were shown to develop interstitial pulmonary fibrosis, bronchial carcinomas and occasional mesotheliomas after inhaling asbestos, as humans do
  • In the reviewed studies, rabbits developed marked pulmonary fibrosis, but the dust caused no pulmonary tumors or mesotheliomas
  • In the reviewed studies, cats and vervet monkeys developed pulmonary fibrosis, but no tumors were found in either species
  • In an unpublished baboon inhalation study, one pleural mesothelioma had apparently been found five years after inhalation began (personal communication)
  • Asbestos bodies, common in human lungs, occur only very rarely in rats
  • In the Edinburgh rat study, both chrysotile groups had more interstitial fibrosis at 29 months than any amphibole group. Fibrosis as a percentage of lung volume was 9.15 for chrysotile at 10 mg/m3, 3.86 for chrysotile at 2 mg/m3, 2.58 for amosite at 10 mg/m3, and 1.38 and 0.76 for crocidolite at 10 and 5 mg/m3
  • In the Edinburgh rat study, all malignant lung tumors occurred in chrysotile-treated rats: 8 bronchial carcinomas in the 10 mg/m3 chrysotile group and 2 in the 2 mg/m3 chrysotile group, with 0 in the amosite and crocidolite groups (group sizes not given)
  • For both fibrosis and malignancy, the two chrysotile clouds showed a marked dose-response effect
  • Disease levels in the Edinburgh study did not match fiber numbers counted by optical microscopy
  • By scanning electron microscopy, the text says the chrysotile clouds had about 7% of fibers longer than 20 micrometres, while Table I as printed lists more than 20% for both chrysotile clouds. The crocidolite and amosite clouds had less than 0.5%
• The authors' conclusion: The author concluded that the rat is the best available animal model for asbestos studies and the best that can be used in large numbers worldwide. The author also concluded that the Edinburgh data strongly support the idea that long asbestos fibers are much more dangerous than short ones, and that fiber mass is unimportant in determining asbestos effects
• Limitations the authors state:
  • It is uncertain whether the rat's inability to form asbestos bodies is a serious disadvantage for modelling human tissue reactions
  • The lowest dose used in the intrapleural injection studies discussed, 0.5 mg, is large compared with what a human lung could accumulate from the urban environment
  • It is not yet known whether fibers shorter than 5 micrometres are completely harmless or only relatively so

Topics

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

Related studies

• Animal models of malignant mesothelioma — A.B. Kane (2006)
• Epithelial outgrowths from lung tissue following intrapleural injection of asbestos dust in experimental animals — J.M. Davis (1971)
• The use of wild animal models to detect evidence of environmental contamination by asbestos-like substance — R. Puleio, M.R. Schiavo, et al. (2013)
• Development of an animal model, techniques, and an exposure system to study the effects of asbestos cement dust inhalation — A.P. Wehner, G.E. Dagle, et al. (1978)
• Effect of NSAIDS and COX-2 inhibitors on the incidence and severity of asbestos-induced malignant mesothelioma: evidence from an animal model and a human cohort — C. Robinson, H. Alfonso, et al. (2014)
• Electron-microscope studies of asbestosis in man and animals — J.M. Davis (1965)

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