Pulmonary response, in vivo, to silicon carbide whiskers

Our plain-English summary of Pulmonary response, in vivo, to silicon carbide whiskers, by G.L. Vaughan, S.A. Trently, R.B. Wilson (Environmental Research, 1993).

The study

• Authors: G.L. Vaughan, S.A. Trently, R.B. Wilson
• Journal: Environmental Research
• Published: 1993;63(2):191-201
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fischer rats were exposed to silicon carbide whiskers (SiCW), boron carbide whiskers (BCW), silicon carbide platelets (SiCP), or crocidolite asbestos separately administered by intratracheal instillation. SiCW proved to be the most toxic material within the test group. Dramatic increases in alveolar macrophage populations within 1 week of exposure to SiCW persisted for at least 28 days, evidence of the chronic inflammation observed in necropsies during the first months of the study. The most common finding in histological preparations of tissues taken from animals 18 months after exposure to SiCW was a high incidence (frequency > 0.85) of multiple pulmonary granulomas which occasionally occluded airways. Lesions associated with crocidolite were similar to those found with SiCW. Equivalent treatment with BCW and SiCP produced no significant histological changes within 18 months of exposure.

In plain English

This was an animal experiment in Fischer rats exposed to silicon carbide whiskers (SiCW-1, SiCW-2), boron carbide whiskers (BCW), silicon carbide platelets (SiCP), or crocidolite asbestos, with phosphate-buffered saline controls; table footnotes record a low and a high dose (printed as 1 mg/100 ml MW and 5 mg/100 ml, with the footnote cut off in this scan), and a separate group was exposed by intraperitoneal injection to PBS or SiCW-2. In the legible portions of the article, the most notable finding at the end of the 18-month exposure was a high incidence of granulomas in the SiCW treatment groups; these nodules were numerous, often large, and obstructed airways. No nodules were found in BCW- or SiCP-exposed animals. Fibrosis, interstitial pneumonia, alveolitis, hyperplasia and squamous metaplasia were associated with SiCW-1 and, to a lesser extent, crocidolite, and SiCW and asbestos were distributed throughout the pulmonary system; no ferruginous bodies were seen. After intraperitoneal injection, peritoneal fibrosis occurred in 90% of animals exposed to SiCW-2. The authors reported no mesothelioma or other malignancy attributable to whisker treatment, while noting the study duration.

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 in rats, with materials given by intratracheal instillation and, in a separate group, by intraperitoneal injection, with follow-up to 18 months
• Who was studied: Fischer rats; group sizes are given in the tables but are largely illegible in this scan
• Exposure: silicon carbide whiskers (SiCW-1, SiCW-2), boron carbide whiskers (BCW), silicon carbide platelets (SiCP) and crocidolite asbestos, with PBS controls; a table footnote records a low dose (LD) printed as 1 mg/100 ml MW and a high dose (HD) printed as 5 mg/100 ml, the footnote being truncated in this scan
• Main results:
  • At the end of the 18-month exposure the most notable histopathological finding was a high incidence of granulomas in the SiCW treatment groups; the nodules were numerous, often large, and obstructed airways
  • No nodules were found in the BCW- and SiCP-exposed animals
  • Other pathological conditions reported included fibrosis, interstitial pneumonia, alveolitis, hyperplasia and squamous metaplasia, associated with SiCW-1 and to a lesser extent crocidolite
  • SiCW and asbestos were distributed throughout the pulmonary system, with highest concentrations in pulmonary granulomas
  • No ferruginous bodies were seen in this study
  • In the animals injected intraperitoneally, peritoneal fibrosis occurred in 90% of those exposed to SiCW-2, with abdominal organ adhesions and, in two instances, lethal intestinal obstruction
  • The authors reported elevated neutrophils as part of the initial response to whisker instillation, with macrophage levels remaining high over the first month
  • Regional lymph nodes contained fiber-laden macrophages, indicating fibers had been mobilized from the lungs
• The authors' conclusion: The authors concluded that, although significant tissue damage and a high incidence of benign tumors were produced, no mesothelioma or other malignancy was observed that could be attributed to whisker treatment in this study
• Limitations the authors state:
  • The authors noted that the time course for development of malignancy in response to mineral fibers equals or exceeds the rats' life span, and that a longer study might have given different results
  • The authors noted the rat as an experimental model for pneumoconiosis differs from other species, including in the absence of ferruginous body formation

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Alveolar Macrophage, Chronic Inflammation, Granuloma.

Related studies

• The immediate effects of silicon carbide whiskers upon ciliated tracheal epithelium — G.L. Vaughan, J.R. Kennedy, et al. (1991)
• In vitro activity of silicon carbide whiskers in comparison to other industrial fibers using four cell culture systems — N.F. Johnson, M.D. Hoover, et al. (1992)
• The toxicity, in vitro, of silicon carbide whiskers — G.L. Vaughan, J. Jordan, et al. (1991)
• Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders — I. Svensson, E. Artursson, et al. (1997)
• Pulmonary effects and biopersistence of deposited silicon carbide whisker after 1-year inhalation in rats — I. Akiyama, A. Ogami, et al. (2007)
• Histopathological changes in rat lung following intratracheal instillation of silicon carbide whiskers and potassium octatitanate whiskers — A. Ogami, Y. Morimoto, et al. (2007)

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