The effects of inhaled crocidolites from Transvaal and North-west Cape mines on the lungs of rats and guinea-pigs

Our plain-English summary of The effects of inhaled crocidolites from Transvaal and North-west Cape mines on the lungs of rats and guinea-pigs, by S.K. Botham, P.F. Holt (British Journal of Experimental Pathology, 1972).

The study

• Authors: S.K. Botham, P.F. Holt
• Journal: British Journal of Experimental Pathology
• Published: 1972;53(6):612-20
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

A group of guinea-pigs and another of rats were successively placed for 400 hours in an atmosphere containing a high concentration of North-west Cape (NWC) crocidolite fibres. A further group of guinea-pigs inhaled Transvaal (TVL) crocidolite for an equal time. Guinea-pigs that inhaled NWC crocidolite were substantially outlived by animals of the other 2 groups, of which the longest survivors were 2 guinea-pigs. No mesotheliomata were found but in all the lungs cellular proliferation of the septa caused a reduction in alveolar space. Giant cells were common and asbestos bodies developed in guinea-pigs, but in rats only a very few, atypical asbestos bodies were seen, and giant cells were rare. All lungs contained uncoated fibres, long fibres (occasionally exceeding 50 μm) being seen in subpleural regions in older animals and in peribronchiolar accumulations. NWC fibres reached the muscular coats of larger bronchioles of guinea-pigs sooner than TVL crocidolite. Proliferation of bronchiolar epithelium was produced in guinea-pigs and 2 rats by NWC crocidolite, but not by TVL crocidolite. Guinea-pigs dying over 3 months and rats over 18 months after inhalation of NWC crocidolite had several small emphysematous regions at the lung periphery, but only one small area was seen in each of the last 2 guinea-pigs that inhaled TVL fibres. Thus, NWC crocidolite produced greater disruption of the respiratory surfaces. Severe lung fibrosis was not seen, although fine collagen strands were found in interalveolar septa of animals dying at over 5 months after dusting began. Dense subpleural areas of collagen produced by TVL crocidolite were, however, found in the 4 oldest guinea-pigs. Inhalation of these 2 crocidolites results in different pathological responses, although no difference in distribution in the lung were found to explain differences in survival time, bronchiolar epithelial proliferation or subpleural collagen formation.

In plain English

This was an animal experiment. Fourteen male albino rats and 13 male albino guinea-pigs breathed a high concentration of crocidolite asbestos from North-west Cape (NWC) mines. Twelve guinea-pigs breathed crocidolite from Transvaal (TVL) mines. Each exposure lasted 400 hours over 4 weeks, and a few unexposed animals served as controls. The authors aimed to produce mesotheliomas and to compare the two dusts. No mesothelioma was found in any animal. All NWC guinea-pigs were dead by 273 days; one had been killed while apparently healthy at 129 days for examination. The last NWC rat died at 668 days and the last TVL guinea-pig at 848 days. Some early deaths in both guinea-pig groups involved pneumonia. All groups had thickened air-sac walls, but scarring (collagen) was never severe. Thick collagen bands under the lung lining appeared only in TVL guinea-pigs. Growth of cells lining small airways appeared in some NWC guinea-pigs and a few rats, not in TVL guinea-pigs. Asbestos bodies were common in guinea-pigs but very rare in rats. The authors concluded that the two crocidolites had different effects, TVL crocidolite appearing less severe in its lethal effect.

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 inhalation experiment comparing two crocidolites, with unexposed control animals
• Who was studied: 14 male albino rats and 13 male albino guinea-pigs exposed to NWC crocidolite; 12 guinea-pigs exposed to TVL crocidolite; 4 control rats and 3 control guinea-pigs (Department of Chemistry, University of Reading)
• Exposure: Finely divided airborne crocidolite dust from North-west Cape or Transvaal mines in a dust tunnel, for 400 hours in 4 weekly periods of 100 hours; NWC fibres were predominantly finer than TVL fibres
• Main results:
  • No mesothelioma was found in any animal.
  • Some animals were killed while apparently healthy for histological examination rather than dying or being killed when dying. In the table these were TVL guinea-pig 6 at 220 days, NWC guinea-pig 5 at 129 days, and NWC rats 1 and 2 at 164 and 365 days.
  • All guinea-pigs that inhaled NWC crocidolite (Group B) were dead within 273 days. This includes one apparently healthy animal killed at 129 days for histological examination.
  • The last rat that inhaled NWC crocidolite (Group C) died at 668 days. According to the table, the first rat death that was not a scheduled killing for examination came at 501 days.
  • Among guinea-pigs that inhaled TVL crocidolite (Group A), apart from the initial deaths in the first 66 days and one animal killed for examination at 220 days, all survived 493 days or longer; the last died at 848 days.
  • Collagen (scarring) in the lungs never became severe fibrosis, even in the oldest animals.
  • A thick band of collagen under the pleura formed, at intervals, only in animals that inhaled TVL crocidolite.
  • Proliferation of the epithelial cells lining terminal bronchioles was seen in some guinea-pigs and a few rats that inhaled NWC crocidolite, but not in guinea-pigs that inhaled TVL crocidolite.
  • Small areas of emphysema under the pleura were seen in NWC guinea-pigs surviving more than 91 days and NWC rats surviving more than 547 days; only very small areas were seen in the final 2 TVL guinea-pigs.
  • Asbestos bodies were very rare and atypical in the rats.
• The authors' conclusion: The authors concluded that survival times confirmed a difference between the effects of the two crocidolites, with TVL crocidolite appearing less severe in its lethal effect.
• Limitations the authors state:
  • Early deaths among guinea-pigs in both groups involved pneumonia, which the authors said may have been infective or dust induced.
  • The guinea-pigs that inhaled NWC crocidolite may have died before pleural thickening could develop.
  • Differences in survival could not be entirely accounted for by differences in the lung tissue.

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Transvaal, Asbestos Bodies, Epithelium, Fibrosis, Collagen.

Related studies

• Asbestos-body formation in the lungs of rats and guinea-pigs after inhalation of anthophyllite — S.K. Botham, P.F. Holt (1972)
• The development of glass-fibre bodies in the lungs of guinea-pigs — S.K. Botham, P.F. Holt (1971)
• Development of asbestos bodies on amosite, chrysotile and crocidolite fibres in guinea-pig lungs — S.K. Botham, P.F. Holt (1971)
• The calcification of fibrous pleural lesions produced in guinea-pigs by the injection of chrysotile asbestos dust — J.M. Davis (1971)
• Biochemical changes and pulmonary response of guinea pigs to asbestos dust — J. Singh, M.U. Beg, et al. (1976)
• Lung cell reactions in guinea pigs after inhalation of asbestos (amosite) — M. Sjöstrand, R. Rylander, et al. (1989)

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