Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders

Our plain-English summary of Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders, by I. Svensson, E. Artursson, P. Leanderson, et al (American Journal of Industrial Medicine, 1997).

The study

• Authors: I. Svensson, E. Artursson, P. Leanderson, R. Berglind, F. Lindgren
• Journal: American Journal of Industrial Medicine
• Published: 1997;31(3):335-43
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objectives of this work were to investigate the toxicity of silicon carbide whiskers and powders and silicon nitride whiskers and powders and to compare their toxicity with the toxicity of crocidolite. The effects studied were inhibition of the cloning efficiency of V79 cells, formation of DNA strand breaks by means of a nick translation assay, formation of oxygen radicals in three different assays, and the ability to stimulate neutrophils to produce hydroxyl radicals. All materials showed concentration-dependent inhibition of the cloning efficiency of V79 cells. The inhibition by the most toxic whiskers was in the same order of magnitude as that of crocidolite. Milled whiskers and powders were less toxic than the whiskers. There was a high DNA breaking potential for crocidolite and four of the silicon carbide whiskers and a rather low one for the other materials. Formation of hydroxyl radicals was found for crocidolite and one of the silicon carbide whiskers. In the neutrophil activation test, there was a great variation in the different materials' abilities to activate neutrophils. There was also a good correlation between chemiluminescence and H2O2 formation. The highest activation was found in neutrophils exposed to two of the silicon carbide whiskers and one milled whisker. The conclusion of the investigation is that some of the ceramic materials studied had damaging biological effects comparable to or greater than those of crocidolite. The results from the investigation clearly imply that caution is needed in the introduction of new ceramic fiber materials, so that the correct precautions and protective devices are used in order to avoid harm to the personnel handling the material.

In plain English

This laboratory (in vitro) study tested ceramic materials and compared them with UICC crocidolite asbestos. The materials were four silicon carbide and one silicon nitride whiskers, one powder of each, and one silicon carbide whisker milled for 3 or 58 hours. Tests used Chinese hamster lung cells (V79), neutrophils (white blood cells) from healthy human donors, and cell-free chemical tests. All materials reduced colony formation more as the dose rose. The dose that halved colony formation ranged from 0.9 µg/cm2 (95% confidence interval 0.8 to 1.2) to 4.2 µg/cm2 (3.8 to 4.7) across the unmilled whiskers, and was 1.4 µg/cm2 (1.2 to 1.7) for crocidolite. In this colony test, milling made the whisker less toxic and the powders were much less toxic, but 3-hour milling increased DNA breaks and one measure of radical formation. DNA strand breaks increased for all materials except two whiskers. Only crocidolite and one silicon carbide whisker significantly increased hydroxyl radical formation. Several silicon carbide whiskers caused the greatest neutrophil activation, and crocidolite caused moderate activation. The authors concluded that new fiber materials need caution until their toxicity has been carefully investigated. They noted that the DNA-break test varied between experiments.

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: In vitro laboratory study (cell culture and cell-free assays)
• Who was studied: V79 Chinese hamster lung fibroblasts (colony-forming and DNA strand break tests), neutrophils from healthy human donors (activation tests), and cell-free chemical systems (hydroxyl radical tests)
• Exposure: Four silicon carbide whiskers (SiCW-1 to SiCW-4), one silicon nitride whisker (SiNW), a silicon carbide powder (SiCP) and a silicon nitride powder (SiNP), plus SiCW-3 ball-milled for 3 hours (SiCW-3S) and 58 hours (SiCW-3L), all compared with UICC standard crocidolite
• Main results:
  • In V79 cells, the concentration giving 50% survival (EC50) ranged from 0.9 to 4.2 µg/cm2 across the unmilled whiskers (point estimates for different materials) and was 1.4 µg/cm2 for crocidolite
  • The silicon nitride whisker (SiNW) had an EC50 of 0.9 µg/cm2 with a 95% confidence interval of 0.8 to 1.2
  • SiCW-3 had an EC50 of 4.2 µg/cm2 with a 95% confidence interval of 3.8 to 4.7
  • Crocidolite had an EC50 of 1.4 µg/cm2 with a 95% confidence interval of 1.2 to 1.7
  • In the colony test, milling SiCW-3 for 3 hours and for 58 hours raised its EC50 from 4.2 µg/cm2 to 6.9 µg/cm2 and to 10.7 µg/cm2 respectively, meaning lower toxicity
  • Milling SiCW-3 for 3 hours lowered its toxicity in the colony test but increased radical formation measured by deoxyguanosine hydroxylation
  • Long milling reduced the DNA breaking potential of SiCW-3, while short milling increased it
  • Both powders (SiNP and SiCP) were much less toxic in the colony-forming test
  • DNA strand breaks increased for all materials except SiCW-2 and SiNW
  • The whiskers that significantly increased hydroxyl radical formation were SiCW-4 and crocidolite
  • In neutrophils, SiCW-1, SiCW-3, SiCW-4, SiCW-3L and SiCW-3S caused the greatest chemiluminescence, while SiCW-2, SiNP, SiCP and crocidolite caused moderate chemiluminescence
  • The silicon nitride whisker (SiNW) did not cause a significant increase in neutrophil chemiluminescence
  • Neutrophil chemiluminescence correlated with neutrophil-produced hydrogen peroxide (r = 0.87)
• The authors' conclusion: The authors concluded that a cautious attitude must be kept toward new fiber materials until their toxicity has been carefully investigated
• Limitations the authors state:
  • The nick translation (DNA strand break) technique varied more between experiments than within each experiment

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Hydroxyl Radical.

Related studies

• The toxicity, in vitro, of silicon carbide whiskers — G.L. Vaughan, J. Jordan, 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)
• Pulmonary response, in vivo, to silicon carbide whiskers — G.L. Vaughan, S.A. Trently, et al. (1993)
• The immediate effects of silicon carbide whiskers upon ciliated tracheal epithelium — G.L. Vaughan, J.R. Kennedy, et al. (1991)
• Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes — Y. Grosse, D. Loomis, et al. (2014)
• 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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