Incidence of various types of thoracic malignancy induced in rats by intrapleural injection of 2 mg of various mineral dusts after inhalation of 222Ra

Our plain-English summary of Incidence of various types of thoracic malignancy induced in rats by intrapleural injection of 2 mg of various mineral dusts after inhalation of 222Ra, by J. Bignon, G. Monchaux, J. Chameaud, et al (Carcinogenesis, 1983).

The study

• Authors: J. Bignon, G. Monchaux, J. Chameaud, M.C. Jaurand, J. Lafuma, R. Masse
• Journal: Carcinogenesis
• Published: 1983;4(5):621-8
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

After inhalation of 222Ra at equilibrium with radon daughters, male Sprague-Dawley rats were inoculated intrapleurally with 2 mg of unleached or acid-leached asbestos fibres or glass fibres or quartz. The additive co-carcinogenic effects of this type of insult were demonstrated by the increased incidence of malignant thoracic tumours. In rats given mineral materials, bronchopulmonary carcinomas and mixed carcinomas were observed, as well as typical mesotheliomas and combined pulmonary pleural tumours, whereas in control rats inhaling radon alone, only bronchopulmonary carcinomas occurred. No significant differences in tumour incidence were observed between the groups of animals given the different types of dusts, but statistically significant differences were noted in survival times, according to the histological type of tumour. The co-carcinogenic effects of an insult of the pleura by mineral dusts following inhalation of radon are discussed in relation to a possible tumour-promoting effect by these agents.

In plain English

This was an animal experiment on male Sprague-Dawley rats. All rats first inhaled radon with its decay products, to a cumulative dose of 6000 working-level-months over 10 weeks. About two weeks later, 100 rats, in groups of 10, had 2 mg of one of ten dusts injected into the pleural (chest) cavity: untreated or acid-leached chrysotile, crocidolite or amosite asbestos, JM 104 glass fibres, or two kinds of quartz. Another 60 rats inhaled radon only, and no rats received dust alone. Of 97 dust-injected rats examined, 66 (68%) developed malignant chest tumours, compared with 17 of 60 (28%) radon-only rats. Radon-only rats had no pleural tumours. Typical mesotheliomas occurred only in asbestos-injected rats. Glass-fibre and quartz rats also had combined pulmonary pleural tumours, which the authors could not classify as starting in the pleura or as lung tumours spreading to it. Rats with mesothelioma survived for shorter times than rats with the other tumour types. The authors said the groups were too small to compare fibre types statistically. They concluded that the results confirmed the radon inhalation model for showing a promoting action of agents such as asbestos.

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 (radon inhalation followed by intrapleural injection of mineral dusts in rats, observed for their lifespan)
• Who was studied: Male SPF Sprague-Dawley rats, three months old at the time of radon inhalation. 100 rats were in 10 dust groups of 10. Three were cannibalized, leaving 97 analysed. A further 60 rats inhaled radon only as controls. The authors' laboratories were in France; the article does not give dates for the experiment.
• Exposure: All rats: radon at equilibrium with its decay products, to a cumulative 6000 working-level-months (3000 WL/day, 10 h a day, 4 days a week for 10 weeks). Dust groups: about two weeks later, 2 mg in 0.5 ml saline injected into the pleural cavity. The dusts were UICC chrysotile A, oxalic acid-leached chrysotile, hydrochloric acid-leached chrysotile, UICC crocidolite, oxalic acid-leached crocidolite, UICC amosite, oxalic acid-leached amosite, JM 104 glass fibres, DQ 12 quartz and BRGM quartz.
• Main results:
  • Malignant thoracic tumours occurred in 17 of 60 radon-only rats (28%) and in 66 of 97 rats given radon plus an intrapleural dust injection (68%).
  • No pleural tumours were seen in rats that inhaled radon only.
  • Typical mesotheliomas occurred only in rats injected with asbestos fibres.
  • Acid-leached chrysotile groups: there were no mesotheliomas with oxalic acid-leached chrysotile. With hydrochloric acid-treated chrysotile there were two pleural tumours, one mesothelioma and one combined pulmonary pleural tumour.
  • JM 104 glass fibre group: no typical mesothelioma, but 2 combined pulmonary pleural tumours.
  • Quartz groups: no typical mesothelioma. There were 2 combined pulmonary pleural tumours with DQ12 quartz and 3 with BRGM quartz.
  • Rats with typical pleural mesothelioma had shorter survival times than rats with combined pulmonary pleural tumours or with bronchopulmonary carcinomas.
• The authors' conclusion: The authors concluded that the results confirmed the validity of the radon inhalation model for demonstrating a promoting action of agents such as asbestos and tobacco in respiratory cancer. They suggested a synergistic effect between radon and dusts, whether fibrous or not.
• Limitations the authors state:
  • The groups were too small for statistical comparison of carcinogenic effects by fibre type.
  • The small number of rats per dust group made survival comparisons between these groups unreliable.
  • No control rats were given the dusts without radon.
  • For combined pulmonary pleural tumours, the tissue appearance did not allow the authors to tell primary pleural tumours apart from lung tumours extending to the pleura and mimicking mesothelioma.
  • The suggested tumour-promoting mechanism acting at a distance from the lung was not tested, and the authors said it needs a further experiment.

Topics

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

Medical terms in this study, explained in our Lexicon: Carcinogenic, Carcinoma, Mesothelioma, Pleura.

Related studies

• Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure — C.H. McMillan, A.D. Jones, et al. (1989)
• Mesothelioma in rats following intrapleural injection of chrysotile and phosphorylated chrysotile (chrysophosphate) — A. Van der Meeren, J. Fleury, et al. (1992)
• Inhalation and injection studies in rats using dust samples from chrysotile asbestos prepared by a wet dispersion process — J.M. Davis, J. Addison, et al. (1986)
• Evaluation of the tumorigenic potential of vermiculite by intrapleural injection in rats — B. Hunter, C. Thomson (1973)
• Epithelial outgrowths from lung tissue following intrapleural injection of asbestos dust in experimental animals — J.M. Davis (1971)
• Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres — G. Monchaux, J. Bignon, et al. (1981)

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