Biological reactivity of calcium silicate composites--in vitro studies

Our plain-English summary of Biological reactivity of calcium silicate composites--in vitro studies, by J. Hunt, F.D. Pooley, R.J. Richards (Environmental Research, 1981).

The study

• Authors: J. Hunt, F.D. Pooley, R.J. Richards
• Journal: Environmental Research
• Published: 1981;26(1):51-68
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The biological reactivity of three samples of manmade calcium silicate composites (A-C) was compared with chrysotile asbestos and titanium dioxide in simple in vitro test systems. Like chrysotile, composite A was actively hemolytic and its hemolytic potential was increased upon sonication. Heat treatment, coincidental with color changes, produced alterations in their hemolytic potential. All the composites were equally active in reducing alveolar macrophage viability and, like chrysotile, calcium silicate B interfered with collagen deposition in lung fibroblast cultures. Composite A produced little effect on fibroblast cultures except at high doses. The composites were all less reactive than chrysotile but more reactive than titanium dioxide. The order of reactivity of each individual composite was different in the test systems employed which may be related in part to their different physical nature but also to their different surface chemistry.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This laboratory study compared how three man-made calcium silicate composites (A, B, C) from the Royal Navy reacted with living cells. The main comparisons were chrysotile asbestos (UICC Rhodesian) and titanium dioxide; the macrophage tests also used crocidolite asbestos and Brazilian silica. The tests used rabbit red blood cells, lung macrophages and lung fibroblasts, plus abdominal injections in rats. Breaking open 20% of red cells took 0.4 mg of chrysotile but 2.8 mg of crushed composite A, 25.0 mg of B and 15.0 mg of C. A 'respirable' preparation of A was about as active as chrysotile. At 5 mg, each crushed composite left only 60% of macrophages surviving after 60 minutes, similar to 1 mg of chrysotile. Crocidolite (5 mg) left less than 20%. Composite B lowered fibroblast protein and collagen (hydroxyproline) like chrysotile, but needed at least 500 micrograms versus 250. Under the microscope, it interfered with collagen deposition only at four to eight times chrysotile concentrations. The authors concluded that in every test the composites were less reactive than chrysotile but more reactive than titanium dioxide, in an order that varied between tests.

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 (in vitro) experiments on cells, with one additional experiment injecting dust into the abdominal cavity of rats
• Who was studied: Three man-made calcium silicate composites (A to C) supplied by the Royal Navy, tested on rabbit red blood cells, rabbit alveolar macrophages, primary rabbit lung fibroblast cultures, and rats injected intraperitoneally (Cardiff, Wales)
• Exposure: Calcium silicate composites A, B and C in crushed, sonicated and 'respirable' preparations. They were compared with UICC Rhodesian chrysotile A (three preparations) and titanium dioxide (anatase). UICC crocidolite asbestos and Brazilian silica were also used in the macrophage tests.
• Main results:
  • To produce 20% red cell breakdown (hemolysis), 0.4 mg of chrysotile was needed, versus 2.8 mg of crushed calcium silicate A, 25.0 mg of B and 15.0 mg of C
  • Sonication increased the hemolytic activity of the crushed composites, and a respirable preparation of composite A had approximately the same hemolytic activity as chrysotile
  • After heat treatment, composites B and C showed increased hemolytic activity above 300°C, together with a color change
  • At 5 mg, each crushed composite left only 60% of alveolar macrophages surviving after 60 minutes, an effect similar to 1 mg of UICC chrysotile
  • With 5 mg of UICC crocidolite asbestos, less than 20% of macrophages survived
  • Macrophages treated with 5 mg of titanium dioxide, like untreated control cells, stayed nearly all viable
  • In rats, 48 hours after injection into the abdominal cavity, 10 mg of calcium silicate A raised the number of peritoneal cells to a similar degree as 1 mg of UICC chrysotile
  • In the chemical study of lung fibroblast cultures, calcium silicate B reduced protein and hydroxyproline (a collagen measure) as chrysotile did, but needed a minimum of 500 micrograms, compared with a minimum of 250 micrograms for chrysotile
  • Calcium silicate A, by contrast, led to higher protein levels in fibroblast cultures and hydroxyproline levels similar to normal cultures
  • In the microscope (cytological) fibroblast studies, only composite B interfered with collagen deposition, and only at four to eight times the concentrations used with chrysotile
  • Order of activity reported by the authors:
• Hemolysis: chrysotile, then A (much more than the rest), then C, then B, then titanium dioxide.
• Macrophage mortality: chrysotile, then A, B and C equally, then titanium dioxide.
• Lung fibroblast reaction: chrysotile, then B, then A.
• The authors' conclusion: The authors concluded that in each test system the calcium silicate composites were less reactive than chrysotile but more reactive than titanium dioxide, and that the order of reactivity among the composites differed between test systems
• Limitations the authors state:
  • The 'respirable' preparation did not contain the same proportions of materials as the original composites
  • The highly variable physical nature of the composites made a particle size distribution study practically impossible
  • It was unknown whether the different crystalline phases detected were present on the mineral surface
  • The physical characteristics of the composites could not be assumed to be identical

Topics

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

Medical terms in this study, explained in our Lexicon: Silicate, Chrysotile, Alveolar Macrophage, Collagen, Deposition, Fibroblast.

Related studies

• The biological reactivity of calcium silicate composites: in vivo studies — R.J. Richards, T.D. Tetley, et al. (1981)
• Cytotoxic and genotoxic effects of calcium silicates on human lymphocytes in vitro — M. Aslam, N. Fatima, et al. (1993)
• Rat lung reactivity to natural and man-made fibrous silicates following short-term exposure — I. Lemaire, P.G. Dionne, et al. (1989)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• Relative effects of asbestos and wollastonite on alveolar macrophages — W.H. Pailes, D.J. Judy, et al. (1984)
• Genotoxicity of dimethylnitrosamine in the presence of chrysotile asbestos UICC B and xonotlite — F. Denizeau, M. Marion, et al. (1985)

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