The in vivo biological activity of ceramic fibres

Our plain-English summary of The in vivo biological activity of ceramic fibres, by R.C. Brown, J.A. Hoskins, L.R. Glass (The Annals of Occupational Hygiene, 1995).

The study

• Authors: R.C. Brown, J.A. Hoskins, L.R. Glass
• Journal: The Annals of Occupational Hygiene
• Published: 1995;39(5):705-13
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The well-known health effects following exposure to amphibole asbestos have led to some concern about the potential for other fibrous materials to cause similar diseases. This paper presents a summary of some of the inhalation experiments conducted with ceramic fibres in both rats and hamsters at the Research and Consulting Company, Geneva. One ceramic fibre (designated RCF1) was tested in rats at four exposure levels, this fibre was also tested in hamsters. Three other fibres were only tested in rats at the highest level--30 mg m-3. The increased incidence of tumours in these experiments has been contrasted with the negative results obtained with glass or mineral wools. However, there is evidence that the ceramic fibres were longer than the glass fibres and that long ceramic fibres were retained in lung tissue to a greater extent. This is sufficient to explain the results without recourse to explanations based on chemical differences between fibres.

In plain English

This article was a review by the authors, not a new experiment. It summarized inhalation experiments with refractory ceramic fibres (man-made glass fibres used in high-temperature insulation, not asbestos). The experiments were carried out in male rats and hamsters at the Research and Consulting Company in Geneva. Animals breathed fibre dust 6 hours a day, 5 days a week. Thirty-eight per cent of hamsters exposed to kaolin ceramic fibre (RCF1) at 30 mg per cubic metre had mesothelial tumours, mostly very small. Rats exposed at 30 mg per cubic metre to four ceramic fibre types had a statistically significant increase in lung tumours. They also had several microscopic mesotheliomas, which did not reach statistical significance. At lower doses (3, 9 and 16 mg per cubic metre) there was no excess of lung tumours, and one rat at 9 mg developed a microscopic mesothelioma. The authors reported that the ceramic fibres were longer than the glass fibres and that more long fibres stayed in the rats' lungs. They concluded that fibre length and lung 'overload' could explain the rat results, but that the hamster results could not yet be interpreted.

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: a summary and discussion of inhalation experiments in rats and hamsters carried out by others at the Research and Consulting Company (RCC), Geneva, with comparison to RCC experiments using glass and mineral wools
• Who was studied: Male Fischer 344 rats (two separate experiments) and male hamsters (one experiment), in groups of over 100 animals, at RCC in Geneva
• Exposure: Refractory ceramic fibres (vitreous aluminosilicate fibres). Kaolin RCF (RCF1) was given at 30 mg per cubic metre (approximately 200 fibres per ml) to rats for 24 months and to hamsters for 18 months, 6 hours per day, 5 days per week. Three other ceramic fibre types were given to rats at 30 mg per cubic metre only. A later rat experiment used RCF1 at 3, 9 and 16 mg per cubic metre (approximately 25, 75 and 115 fibres per ml). Results were compared with glass fibres (MMVF10 and MMVF11).
• Main results:
  • Hamsters exposed to kaolin RCF: 38% had mesothelial tumours at microscopic examination. Most tumours were very small and did not affect survival. There was some interstitial and pleural fibrosis but no lung tumours.
  • Rats exposed at 30 mg per cubic metre to the various ceramic fibres: a statistically significant increase in lung tumours and several microscopic mesotheliomas. The incidence of these pleural tumours did not reach statistical significance.
  • Rats in the lower-dose (multidose) experiment: no excess of lung tumours at any dose. One rat exposed to 9 mg per cubic metre developed a microscopic mesothelioma. Pleural and parenchymal fibrosis occurred at 16 mg, mild parenchymal fibrosis at 9 mg, and no irreversible effects at the lowest dose.
  • Based on published size data, median fibre lengths were about 30% higher for the ceramic fibre than for the glass fibres. More fibres longer than 20 micrometres were retained in the lungs of rats exposed to RCF1 than in rats exposed to either glass fibre.
• The authors' conclusion: The authors believed the rat results with ceramic fibres could be understood in terms of retention of long (over 20 micrometre) fibres and lung overload. They said the carcinogenic effects in rats were similar to those of many inert particles. They also said the hamster results could not be interpreted until further points were examined and more data were available.
• Limitations the authors state:
  • Size measurements of what should have been the same fibre samples did not agree from one determination to another.
  • More work is needed on fibre dissolution and clearance before firm conclusions can be drawn.
  • The range-finding experiments do not allow identification of a disturbance in lung clearance (overload).
  • In hamsters, the effects of overload are not known.

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: Amphibole Asbestos.

Related studies

• Health effects of refractory ceramic fibres: scientific issues and policy considerations — L.R. Glass, R.C. Brown, et al. (1995)
• Biological activity of respirable industrial fibres treated to mimic residence in the lung — K. Donaldson (1994)
• Biological effects of naturally occurring and man-made fibres: in vitro cytotoxicity and mutagenesis in mammalian cells — R. Okayasu, L. Wu, et al. (1999)
• Free radical activity of synthetic vitreous fibers: iron chelation inhibits hydroxyl radical generation by refractory ceramic fiber — D.M. Brown, C. Fisher, et al. (1998)
• Clinico-pathological features and somatic gene alterations in refractory ceramic fibre-induced murine mesothelioma reveal mineral fibre-induced mesothelioma identities — P. Andujar, C. Lecomte, et al. (2007)
• Exposure to refractory ceramic fibres in the metal industry — M. Linnainmaa, J. Kangas, et al. (2007)

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