Comparison of cytotoxicity of man-made vitreous fibres

Our plain-English summary of Comparison of cytotoxicity of man-made vitreous fibres, by K. Luoto, M. Holopainen, M. Sarataho, et al (The Annals of Occupational Hygiene, 1997).

The study

• Authors: K. Luoto, M. Holopainen, M. Sarataho, K. Savolainen
• Journal: The Annals of Occupational Hygiene
• Published: 1997;41(1):37-50
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The purpose of the study was to compare the cytotoxicity of man-made vitreous fibres (MMVFs): four refractory ceramic fibres (RCFs 1-4), two glasswool fibres (MMVF 10 and 11), a rockwool fibre (MMVF 21) and a slagwool fibre (MMVF 22). The ability of the fibres to induce haemolysis in sheep erythrocytes, to release lactate dehydrogenase (LDH) from rat alveolar macrophages (AM) and to increase the production of reactive oxygen metabolites (ROMs) in human polymorphonuclear leukocytes (PML) was studied. To assess the relative cytotoxicity of MMVFs, their toxicity was compared with that induced by quartz, chrysotile or titanium dioxide. MMVFs induced a modest, but dose-dependent, increase of haemolysis at doses of 0.5, 2.5 and 5.0 mg ml-1. The amount of haemolysis and LDH release induced by MMVFs was generally similar to that induced by titanium dioxide. Glasswool fibre MMVF 10 induced less LDH release from rat AM than rockwool MMVF 21 or slagwool MMVF 22 fibres, whereas glasswool fibre MMVF 11 induced less LDH release than slagwool fibre MMVF 22 (P < 0.05). All fibres also dose-dependently increased the production of ROMs at doses between 25 and 500 micrograms ml-1. The shapes of the time-courses of MMVF-induced production of ROMs suggest that the mechanisms whereby the different fibres induce ROM production may exhibit similar features. There are clear-cut differences in the potency of various MMVFs to induce cytotoxicity and oxidative burst. The present results also emphasize the importance of using several measures of toxicity when assessing the biological activity of various fibres in vitro.

In plain English

This Finnish laboratory study compared how damaging eight man-made vitreous fibres were to cells. The fibres were four refractory ceramic fibres (RCF 1 to 4), glasswool fibres MMVF 10 and 11, rockwool MMVF 21 and slagwool MMVF 22. Quartz, titanium dioxide and, in one test type, chrysotile served for comparison. The tests measured damage to sheep red blood cells, enzyme (LDH) release from rat lung macrophages, and reactive oxygen production by human white blood cells. Red blood cell damage from the man-made fibres was small, similar to titanium dioxide and much less than quartz. The fibres released less LDH than quartz, and both glasswool fibres released less than the slagwool fibre. Reactive oxygen production rose with dose for all materials. At one dose, chrysotile produced less than RCFs 1 and 3 and the slagwool fibre. The authors concluded that the fibres' cell toxicity was relatively mild and close to that of titanium dioxide, though the fibres clearly differed. This applied at these doses and cells, comparing equal masses. Comparing by surface area or particle number might, they noted, give somewhat different results without markedly changing the conclusions.

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 of cell toxicity
• Who was studied: Laboratory cell systems: sheep red blood cells (erythrocytes), alveolar macrophages from adult male Han:Wistar rats (University of Kuopio, Finland), and polymorphonuclear leukocytes from the blood of healthy adult human donors
• Exposure: Four refractory ceramic fibres: RCF 1 (kaolin), RCF 2 (zirconium), RCF 3 (high purity kaolin) and RCF 4 (RCF 1 heated to 1300°C). Also glasswool fibres MMVF 10 and 11, rockwool MMVF 21 and slagwool MMVF 22, all from the TIMA repository. Quartz (positive control) and titanium dioxide (negative control) were used in the haemolysis and LDH tests. Quartz and chrysotile were used in the reactive oxygen tests. Doses were 0.5, 2.5 and 5.0 mg per ml for haemolysis, 1.0 mg per ml for LDH, and 25 to 500 micrograms per ml for reactive oxygen production.
• Main results:
  • Haemolysis rose with dose for all tested dusts and fibres. Haemolysis caused by the man-made fibres was small, at the level of titanium dioxide. Quartz greatly exceeded the man-made fibres. RCFs 1 and 3 were slightly more haemolytic than the other man-made fibres. These results were not analysed statistically.
  • At 1.0 mg per ml, LDH release from rat macrophages was lower for the man-made fibres than for quartz. RCF 1 caused the least LDH release of all the fibres, less even than titanium dioxide.
  • Glasswool MMVF 10 caused less LDH release than rockwool MMVF 21, slagwool MMVF 22 or RCF 3. Glasswool MMVF 11 caused less than slagwool MMVF 22. Slagwool MMVF 22 caused more than RCFs 1 to 4. All of these differences were reported at p less than 0.05.
  • At 400 micrograms per ml, the man-made fibres generally produced less reactive oxygen than quartz in human leukocytes. Slagwool MMVF 22 produced more than all the other man-made fibres. Chrysotile produced less than RCFs 1 and 3 or slagwool MMVF 22.
  • Reactive oxygen production rose with dose for all the man-made fibres, quartz, titanium dioxide and chrysotile.
  • In most cases the man-made fibres' reactive oxygen production fell between that of quartz and chrysotile. Only RCF 4 and glasswool MMVF 11 equalled chrysotile.
  • Haemolysis caused by the man-made fibres did not generally correlate with LDH release or reactive oxygen production.
• The authors' conclusion: The authors concluded that the cellular toxicity of the man-made vitreous fibres was relatively mild and close to that of titanium dioxide. This applied at the doses and cells used, with fibres and dusts compared on a mass basis. There were nonetheless clear-cut differences between fibres. They also concluded that the relative toxicity of mineral fibres should be explored by combining several test systems.
• Limitations the authors state:
  • The haemolysis test for the man-made fibres was carried out only once, in duplicate, because little fibre sample was available. Its results were not analysed statistically.
  • The fibres and dusts were compared by mass. The authors noted that comparison by surface area or particle number might give somewhat different results, though they judged this would not markedly change their conclusions.
  • The reactive oxygen response of leukocytes varied widely between blood donors.

Topics

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

Medical terms in this study, explained in our Lexicon: Vitreous, Lactate Dehydrogenase (LDH), Alveolar Macrophage, Chrysotile, LDH Release.

Related studies

• Production of reactive oxygen species by man-made vitreous fibres in human polymorphonuclear leukocytes — M. Ruotsalainen, M.R. Hirvonen, et al. (1999)
• Activation of alveolar macrophages and peripheral red blood cells in rats exposed to fibers/particles — F. Afaq, P. Abidi, et al. (1998)
• Mechanism of refractory ceramic fiber- and rock wool-induced cytotoxicity in alveolar macrophages — K.A. Kim, W.K. Lee, et al. (2001)
• Long-term health effects in hamsters and rats exposed chronically to man-made vitreous fibres — D.M. Smith, L.W. Ortiz, et al. (1987)
• Biological effects of naturally occurring and man-made fibres: in vitro cytotoxicity and mutagenesis in mammalian cells — R. Okayasu, L. Wu, et al. (1999)
• Refractory ceramic fibers activate alveolar macrophage eicosanoid and cytokine release — G.D. Leikauf, S.P. Fink, et al. (1995)

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