Information Obtained from Animal Experiments

Our plain-English summary of Information Obtained from Animal Experiments, by J.C. Wagner, G. Berry (1973).

The study

• Authors: J.C. Wagner, G. Berry
• Published: BIOLOGICAL EFFECTS OF ASBESTOS (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 8, PP. 285-288 (1973)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This paper was a review, not a new experiment. The authors summarised animal experiments on asbestos reported since 1964, grouped by how the dust was given: into the chest cavity, into the abdomen, into the windpipe, or by breathing. Most work used rats. In one cited study (Wagner, 1972), 20 mg placed in the chest cavity produced mesotheliomas in 61% of rats for crocidolite, 36% for amosite, 34% for anthophyllite and 10% for Canadian chrysotile. The figure for Rhodesian chrysotile is garbled in the scanned text. In the same work, samples with their oils removed produced 58 mesotheliomas, compared with 56 for untreated samples. Gross and colleagues (1967) reported carcinomas in 24 of 72 rats that survived 16 months of breathing chrysotile dust. Fibre-glass and other non-asbestos materials also produced mesotheliomas. The authors concluded that the cancer-causing effect of asbestos was unlikely to be due to oils, waxes or trace elements, and that fine fibres appeared to matter. They noted that placing dust directly in the chest may be criticised as unrealistic.

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• Design: Review of published and unpublished animal experiments on asbestos, grouped by route of administration
• Who was studied: Laboratory animals in experiments reported from 1964 to the early 1970s, mainly rats; hamsters, rabbits and mice were also used
• Exposure: Asbestos given into the chest (pleural) cavity, into the abdomen (peritoneal cavity), into the windpipe, or by inhalation. Fibre types included crocidolite, amosite, anthophyllite, and Canadian and Rhodesian chrysotile, including the five UICC standard reference samples. Some experiments also used non-asbestos materials such as fibre-glass.
• Main results:
  • In a cited study by Wagner (1972), rats given 20 mg into the pleural cavity developed mesotheliomas in 61% for crocidolite, 36% for amosite, 34% for anthophyllite and 10% for Canadian chrysotile. The percentage for Rhodesian chrysotile is garbled in the scan.
  • In a cited study by Stanton and Wrench (1972) using 40 mg, the UICC crocidolite, amosite and Rhodesian chrysotile samples all produced mesotheliomas in rats. The exact proportion is garbled in the scan.
  • In Wagner (1972), the five UICC samples with their oils removed produced 58 mesotheliomas, compared with 56 for the identical untreated samples
  • Davis, cited as a personal communication, produced peritoneal mesotheliomas in 17 of 25 rats and 23 of 50 mice injected with crocidolite
  • In a cited inhalation study (Gross et al., 1967), 24 of 72 rats that survived 16 months of chrysotile exposure developed lung carcinomas, and one developed a mesothelioma
  • In the Wagner (1972) inhalation experiment with the five UICC samples, two mesotheliomas occurred after the shorter exposure (1 day, 7 hours) and one after the 3-month exposure. No explanation was offered for this.
  • In a follow-up inhalation experiment with exposures of up to 2 years, all fibre types produced asbestosis, and the fibrosis progressed after exposure ended. All samples produced an excess of lung tumours, and a few mesotheliomas occurred with Canadian chrysotile.
  • Stanton and Wrench (1972) reported mesotheliomas with silicon dioxide, glass-wool and fibre-glass. The finer fibre-glass samples produced the highest incidence (18%).
  • The authors noted that the experiments associated mesothelioma development with fine fibrous material in the pleural cavity
• The authors' conclusion: The authors concluded that the carcinogenic effect of asbestos was unlikely to be due to the oils and waxes in asbestos or to trace elements. They also stated that there were indications that fibre size and shape were important.
• Limitations the authors state:
  • Placing asbestos directly into the pleural cavity may be criticised as unrealistic
  • In the grinding comparison, a different mill was used, so factors other than particle size could not be ruled out
  • Contamination of the fibre may have played a part in the Gross et al. inhalation results

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Crocidolite, Amosite, Anthophyllite, Chrysotile, Carcinoma.

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