The immediate effects of silicon carbide whiskers upon ciliated tracheal epithelium

Our plain-English summary of The immediate effects of silicon carbide whiskers upon ciliated tracheal epithelium, by G.L. Vaughan, J.R. Kennedy, S.A. Trently (Environmental Research, 1991).

The study

• Authors: G.L. Vaughan, J.R. Kennedy, S.A. Trently
• Journal: Environmental Research
• Published: 1991;56(2):178-85
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Considering the relationship between toxicity of dust and particle geometry, as exhibited by asbestos, we have examined short-term biological effects of SiC whiskers (SiCW) in vitro and in vivo. Cultured explants of tracheal epithelium were exposed to a range of SiCW concentrations. There were no dramatic effects on ciliary function as measured by an optical spectrum analysis system that provided discrete ciliary frequencies. Particles were swept by ciliary activity into nonciliated regions where foci of extensive cell damage and death were observed with whiskers penetrating epithelial layers into the underlying tissues. Similar necrotic foci were observed in tracheae from rats exposed by intratracheal instillation to SiC whiskers in vivo.

In plain English

This laboratory study looked at silicon carbide whiskers, fine crystals used to reinforce ceramics and other composites. Asbestos was not tested; the authors mentioned it as an example of how fiber shape relates to harm. Cultured lining tissue from dog windpipes (tracheas) was exposed to three whisker samples at 5.0 to 100.0 micrograms per square centimeter. The beating of the cilia, the hair-like structures that sweep particles out of airways, was measured over 72 hours. Even at the highest dose, ciliary beating showed no measurable change after 72 hours. The authors noted a possible slight slowing in the first 24 hours that was gone by 48 hours. However, the cilia swept whiskers into areas without cilia, where whiskers pierced and killed cells. This formed patches of dead tissue reaching into the connective tissue below. Rats given whiskers directly into the trachea showed similar patches, and whiskers stayed in the tissue, apparently unchanged, for at least 1.5 years. The authors concluded the whiskers could cause extensive immediate damage to the pulmonary system and suggested safeguards for people handling them.

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: Laboratory experiment: cultured animal tissue (in vitro) plus an animal experiment in rats (in vivo); described by the authors as the first phase of a broader study
• Who was studied: Tracheal (windpipe) lining tissue from dogs euthanized for other reasons, grown in culture (ciliary beating measured in 10 randomly selected cells from each of three donor tissues), and tracheas from Sprague-Dawley rats given whiskers by intratracheal instillation (number of rats not stated); University of Tennessee, Knoxville
• Exposure: Three silicon carbide whisker samples: SiCW-1 (Tateho, Japan), and SiCW-2 and SiCW-3 (American Matrix, Inc.). Cultured tissue received 5.0 to 100.0 micrograms per square centimeter for 24, 48 and 72 hours. Rats received 5.0 mg per 100 ml of minute respiratory volume according to the methods section, and 1.0 to 5.0 mg per 100 ml according to the results section. No asbestos was tested.
• Main results:
  • In cultured dog tracheal tissue, whiskers at the highest dose studied (100 micrograms per square centimeter) had no measurable effect on ciliary motility, even after 72 hours of exposure
  • The authors stated there may have been a slight inhibition of ciliary function in the first 24 hours, but motility was back to normal by 48 hours
  • In cultured tissue, cilia swept whiskers into nonciliated areas, where the whiskers penetrated and killed cells, producing necrotic (dead-tissue) foci extending into the underlying connective tissue
  • In rats, three days after instillation of SiCW-1, multiple necrotic foci were seen in relatively nonciliated regions of the trachea, with large numbers of whiskers piercing the epithelium
  • In exposed rats, whiskers penetrated to the lamina propria beneath the tracheal lining and remained there, apparently unchanged, for at least 1.5 years after exposure
• The authors' conclusion: The authors concluded that silicon carbide whiskers have the potential to produce extensive immediate damage to the pulmonary system and remain in tissue for extended periods. They suggested that care and adequate safeguards be provided to protect those handling the material from pulmonary exposure.

Topics

Medical terms in this study, explained in our Lexicon: Epithelium.

Related studies

• 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)
• Pulmonary response, in vivo, to silicon carbide whiskers — G.L. Vaughan, S.A. Trently, et al. (1993)
• Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders — I. Svensson, E. Artursson, et al. (1997)
• The carcinogenicity of WHO fibers of silicon carbide: SiC whiskers compared to cleavage fragments of granular SiC — K. Rödelsperger, B. Brückel (2006)
• 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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