Long-term health effects in hamsters and rats exposed chronically to man-made vitreous fibres

Our plain-English summary of Long-term health effects in hamsters and rats exposed chronically to man-made vitreous fibres, by D.M. Smith, L.W. Ortiz, R.F. Archuleta, et al (The Annals of Occupational Hygiene, 1987).

The study

• Authors: D.M. Smith, L.W. Ortiz, R.F. Archuleta, N.F. Johnson
• Journal: The Annals of Occupational Hygiene
• Published: 1987;31(4B):731-54
• Cited by: 81 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

As part of a comprehensive inhalation study, groups of Osborne-Mendel rats and Syrian golden hamsters were exposed to several types of airborne man-made vitreous fibres (MMVF). Exposure protocols were "nose-only" 6 h per day, 5 days a week for 24 months, with surviving animals maintained for the rest of their lives. Challenge aerosols consisted of four types of fibrous glass, one refractory ceramic fibre (RCF) and one mineral (slag) wool fibre. UICC crocidolite asbestos and clean air served as positive and negative controls for the inhalation groups. Groups of additional controls were unmanipulated caged animals, intraperitoneally (IP) injected animals, and intratracheally (IT) instilled animals. Animals, after their deaths, were examined macroscopically and microscopically. Fibre lung burdens were significant for the inhalation exposures and related to the mean diameters of the fibrous challenge aerosols. The inhalation exposures with MMVF did not result in any adverse effects except for a mesothelioma of the lung in one hamster exposed to the RCF, not a statistically significant finding. Consistent with other reported work, abdominal mesotheliomas were induced in the groups of hamsters and rats injected IP with 0.5-µm mean diameter fibrous glass, RCF and crocidolite asbestos. With IT instillations, primary lung tumours were found only in hamsters and rats receiving UICC crocidolite; no lung tumours occurred in animals instilled IT with two types of MMVF.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

In this animal experiment, male Syrian hamsters and female Osborne-Mendel rats inhaled man-made vitreous fibres through the nose 6 hours a day, 5 days a week, for 24 months. The fibres were four types of fibrous glass, a refractory ceramic fibre (RCF) and a mineral (slag) wool. UICC crocidolite asbestos was the positive control and clean air the negative control. The only lung tumour in any group inhaling man-made fibres was a mesothelioma in one RCF-exposed hamster, which was not statistically significant. Three of 57 rats inhaling crocidolite for 24 months developed lung tumours. Fibrous lung lesions were significantly more common than in controls among hamsters and rats exposed to crocidolite for 24 months and hamsters exposed for 30 days. When fibres were injected into the abdomen, abdominal mesotheliomas occurred in 8 of 25 rats given the finest glass fibre and in 80% of rats given crocidolite. Abdominal tumours occurred in 19 of 23 rats given RCF. When fibres were placed directly into the windpipe, only crocidolite produced lung tumours. The authors concluded that inhaling these man-made fibres posed minimal risks to the animals in this study.

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: Lifetime animal experiment: chronic nose-only inhalation for 24 months, plus groups given fibres by injection into the abdomen (intraperitoneal) or by instillation into the windpipe (intratracheal), all followed for life
• Who was studied: Male Syrian hamsters and female Osborne-Mendel rats, about 100 days old at the start of exposure; approximately 1900 animals in the inhalation experiments
• Exposure: Four types of fibrous glass (0.45, 3.1, 5.4 and 6.1 micrometre mean diameter), one refractory ceramic fibre (1.8 micrometre mean diameter) and one mineral (slag) wool, with UICC crocidolite asbestos as positive control and clean air as negative control. Injection groups received 25 mg of fibre and windpipe-instillation groups received 10 mg in total, using the finest glass fibre, RCF or crocidolite.
• Main results:
  • Inhalation: one hamster exposed to RCF developed a mesothelioma of the lung; this was not a statistically significant finding
  • Inhalation: no other animals exposed to man-made vitreous fibres developed primary lung tumours
  • Inhalation: 3 of 57 rats exposed to crocidolite for 24 months developed lung tumours (one fibrous mesothelioma and two broncho-alveolar tumours)
  • Inhalation: fibrous lung lesions (early asbestosis) were statistically more frequent than in controls among hamsters and rats exposed to crocidolite for 24 months and hamsters exposed for 30 days (Table 8: 14/58 hamsters, 30/57 rats, and 14/64 hamsters, respectively)
  • Inhalation: no rat or hamster inhalation group had a mean lung lesion grade above 4, the grade at which collagen deposition is first seen
  • Finer-diameter fibres were recovered from the lungs in larger quantities than thicker fibres
  • Abdominal injection: 8 of 25 (32%) rats injected with the 0.45 micrometre glass fibre had abdominal mesotheliomas; saline-injected controls had 0/25 in both species
  • Abdominal injection of RCF: in the first group of 36 hamsters, 21 died within 30 days of acute hemorrhagic peritonitis, and in a second group of 36, 15 died
  • Abdominal injection of RCF: abdominal tumour incidence was 13% and 24% in the two hamster groups (among survivors of the first 30 days) and 19/23 (83%) in rats
  • Abdominal injection of crocidolite: 40% of hamsters and 80% of rats had abdominal mesotheliomas
  • Windpipe instillation: no animals given the two man-made fibres developed primary lung tumours
  • Windpipe instillation of crocidolite: 74% of hamsters (20/27) and 8% of rats (2/25) developed primary lung tumours, all epithelial
• The authors' conclusion: The authors concluded that exposure to significant concentrations of the man-made fibres tested posed minimal risks to the animals in this study, citing the animals' long lifespans
• Limitations the authors state:
  • The authors noted that the single mesothelioma in an RCF-exposed hamster may have been a spontaneous event
  • The authors suggested that the crocidolite lung tumour incidence might have been higher had a longer fibre been used, because the UICC crocidolite was a short-fibred material
  • All exposure aerosols contained more non-fibrous particles than fibres, which the authors noted could matter when assessing effects because high particle concentrations can influence lung clearance
  • Cyclone measurements of the 'respirable' fraction measured total aerosol mass, not only fibrous mass

Topics

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

Medical terms in this study, explained in our Lexicon: Vitreous, UICC, Crocidolite, Mesothelioma.

Related studies

• Differences in the sensitivity of hamster and rat lung cells exposed in vitro to natural and man-made fibres — M. Aufderheide, J.W. Knebel, et al. (1996)
• Relationship between lung biopersistence and biological effects of man-made vitreous fibers after chronic inhalation in rats — T.W. Hesterberg, W.C. Miiller, et al. (1994)
• Biopersistences of man-made vitreous fibers and crocidolite fibers in rat lungs following short-term exposures — R.P. Musselman, W.C. Miiller, et al. (1994)
• Comparison of cytotoxicity of man-made vitreous fibres — K. Luoto, M. Holopainen, et al. (1997)
• Persistence of man-made mineral fibres (MMMF) and asbestos in rat lungs — B. Bellmann, H. Muhle, et al. (1987)
• The chronic effects of exposure of rats to sized glass fibres — R.T. Drew, M. Kuschner, et al. (1987)

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