Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres

Our plain-English summary of Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres, by G. Monchaux, J. Bignon, M.C. Jaurand, et al (Carcinogenesis, 1981).

The study

• Authors: G. Monchaux, J. Bignon, M.C. Jaurand, J. Lafuma, P. Sebastien, R. Masse, A. Hirsch, J. Goni
• Journal: Carcinogenesis
• Published: 1981;2(3):229-36
• Cited by: 79 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The carcinogenicity of untreated UICC chrysotile A, of acid (oxalic and hydrochloric)-leached UICC chrysotile A, of crocidolite and of JM 104 glass fibres has been studied by intrapleural injection into rats. This experiment, carried out on 304 animals, demonstrated that when more than 80% of the Mg had been leached from chrysotile fibres by either hydrochloric or oxalic acid, the proportion of pleural mesotheliomas was either nil or dramatically lower than that obtained with untreated chrysotile. The carcinogenic effect of crocidolite was higher than that of 43.7% oxalic acid-leached chrysotile. The proportion of mesotheliomas observed in animals injected with JM 104 glass fibres was similar to that in animals injected with fibres from which 63.8% had been leached with oxalic acid. These results indicate that with regard to the induction of pleural carcinogenicity by chrysotile fibres, not only size characteristics but also parameters such as chemical composition and physiochemical properties must intervene.

In plain English

This was an animal experiment. 304 male Sprague-Dawley rats each received a single injection into the chest cavity (intrapleural injection) of 20 mg of fibres in saline, or saline alone. The fibres were UICC chrysotile A asbestos, either untreated or treated with oxalic acid to remove 10.2%, 43.7%, 63.8% or 89.1% of its magnesium, or treated with hydrochloric acid to remove 80.6%. Other groups received crocidolite or JM 104 glass fibres. Rats lived until death or until they were moribund. Thoracic tumours, mostly pleural mesotheliomas, occurred in 45% of rats given untreated chrysotile and 47% given 10.2%-leached chrysotile. The figures were 15% and 16% for 43.7%- and 63.8%-leached chrysotile, and 3% for 89.1%-leached chrysotile. No tumours occurred with hydrochloric acid-leached chrysotile or saline. The figure was 54% with crocidolite and 13% with glass fibres. Heavily leached fibres were shorter and thicker. A pneumonia outbreak about 400 days after injection caused early deaths. The authors judged that it prevented some cancers. The authors concluded that fibre size is not the only factor in pleural cancers caused by mineral fibres.

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 (lifetime carcinogenicity study using intrapleural injection in rats)
• Who was studied: 304 SPF male Sprague-Dawley rats, three months old at injection, divided into groups: 32 saline controls, 33 unleached UICC chrysotile A, 32 10.2% oxalic acid-leached chrysotile, 39 43.7% oxalic acid-leached chrysotile, 32 63.8% oxalic acid-leached chrysotile, 36 89.1% oxalic acid-leached chrysotile, 16 80.6% hydrochloric acid-leached chrysotile, 39 crocidolite, 45 JM 104 glass fibres. Some animals had been transferred from a fibre translocation study.
• Exposure: A single intrapleural injection of 20 mg of fibres in 2 ml saline. The fibres were unleached UICC chrysotile A; chrysotile leached with 0.1 N oxalic acid to remove 10.2%, 43.7%, 63.8% or 89.1% of magnesium; chrysotile leached with hydrochloric acid to remove 80.6% of magnesium; crocidolite; or JM 104 glass fibres. Controls received saline.
• Main results:
  • Table III gives the percentage of rats with thoracic tumours in each group, in row order: controls 0, unleached chrysotile 45, 10.2% oxalic acid-leached 47, 43.7% leached 15, 63.8% leached 16, 89.1% leached 3, 80.6% hydrochloric acid-leached 0, crocidolite 54, JM 104 glass fibres 13.
  • Table III gives tumour counts, in the same row order: 0, 14, 15, 6, 5, 1, 0, 21, 6.
  • No cancer occurred in rats given hydrochloric acid-leached chrysotile.
  • Most thoracic tumours were pleural mesotheliomas. One lung carcinoma occurred, in the unleached chrysotile group.
  • Nine peritoneal mesotheliomas were observed, either alongside pleural mesotheliomas or on their own.
  • The percentage of mesotheliomas with crocidolite was similar to that with unleached or slightly leached chrysotile, but survival times were longer.
  • The percentage of mesotheliomas with JM 104 glass fibres was similar to that with chrysotile leached to 43.7% or 63.8% with oxalic acid.
  • Using Pike's model, the estimated carcinogenic insult was greatest for unleached chrysotile and 10.2%-leached chrysotile, and it fell as more magnesium was leached.
  • Using the same model, the carcinogenic insults of crocidolite and JM 104 glass fibres were higher than those of chrysotile leached to 43.7% and 89.1% with oxalic acid.
  • The authors state that unleached or poorly leached chrysotile was more carcinogenic than heavily leached chrysotile.
  • Maximally leached fibres, whether leached with oxalic or hydrochloric acid, were shorter and thicker than the other fibres.
  • In rats given chrysotile, survival time increased with the proportion of magnesium leached. Rats given JM 104 glass fibres survived longer than controls (513 versus 469 days).
• The authors' conclusion: The authors concluded that fibre size is not the only factor in how mineral fibres cause pleural cancers. Other parameters, such as chemical composition and physicochemical properties, are also involved.
• Limitations the authors state:
  • Intrapleural injection may be criticized as unrealistic compared with human exposure.
  • A subacute pneumonia outbreak about 400 days after injection caused early deaths. The authors judged that the infection prevented some cancers, especially in the unleached and 10.2%-leached chrysotile groups.
  • The biological activity of the fibres in vitro was not tested in this study.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Chrysotile, UICC, Crocidolite, Pleural Mesothelioma, Carcinogenic.

Related studies

• Mesotheliomata in rats after inoculation with asbestos and other materials — J.C. Wagner, G. Berry, et al. (1973)
• Mesotheliomas in rats following inoculation with asbestos — J.C. Wagner, G. Berry (1969)
• Analysis of amphibole asbestos in chrysotile and other minerals — J. Addison, L.S. Davies (1990)
• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• Review of the significance of fibre size in fibre-related lung disease: a centrifuge cell for preparing accurate microscope-evaluation specimens from slurries used in inoculation studies — V. Timbrell (1989)
• A study of the length and diameter of fibres, in lung and in broncho-alveolar lavage fluid, following exposure of rats to chrysotile asbestos — E. Kauffer, J.C. Vigneron, et al. (1987)

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