Surface interaction between chrysotile and solutions (dissolution and adsorption): systematic x-ray photoelectron spectroscopy studies

Our plain-English summary of Surface interaction between chrysotile and solutions (dissolution and adsorption): systematic x-ray photoelectron spectroscopy studies, by J.H. Thomassin, J.C. Touray, P. Baillif, et al (IARC Scientific Publications, 1980).

The study

• Authors: J.H. Thomassin, J.C. Touray, P. Baillif, M.C. Jaurand, L. Magne, J. Goni
• Journal: IARC Scientific Publications
• Published: 1980:105-12
• Read it: PubMed

Abstract

To test the reactivity of asbestos in relation to its physical and structural properties, surface analysis was made by X-ray photoelectron spectroscopy. The dissolution kinetics of chrysotile in strong reagents demonstrate two rate-limiting steps for the reaction: Mg2+ diffusion and chemical reaction. In some components of the Krebs cycle and in dilute hydrochloric and in oxalic acids, the reaction is limited by the exchange of Mg2+ in the first mineral layer. The interaction of model phospholipid membranes with chrysotile fibres was also studied; the results are in good agreement with the hypothesis of bilayer adsorption. Photoelectron data for adsorption of ghosts indicate that both proteins and phospholipids must be adsorbed onto chrysotile fibres.

In plain English

This was a laboratory study of fibres, not of people. The authors used X-ray photoelectron spectroscopy, which measures a surface's chemical makeup, to examine how chrysotile asbestos fibres react with liquids. In dissolution experiments, chrysotile from Thetford, Canada was placed in acids at 40°C. These included oxalic acid, dilute hydrochloric acid and acids involved in the Krebs cycle, a set of chemical reactions in the body's cells. In 10-2 N hydrochloric acid, the dissolution curve levelled off from 4 to 25 hours. The authors linked this plateau to leaching of magnesium from the first mineral layer. The Krebs cycle acids were always less reactive than oxalic acid at the same concentration. With UICC chrysotile A, a phosphorus-to-silicon surface signal tracking phospholipid adsorption levelled off at a starting concentration of about 200 micrograms per millilitre. The authors found this compatible with a phospholipid double layer on the fibres. Data for red blood cell membranes indicated that both proteins and phospholipids must be adsorbed. The authors concluded that it is difficult at present to relate these processes to biological explanations of cancer.

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 experiments: surface analysis of chrysotile fibres by X-ray photoelectron spectroscopy after dissolution in acids and after adsorption of biological molecules
• Who was studied: No human or animal subjects. Materials studied: chrysotile from Thetford (Canada) for the dissolution experiments, and UICC chrysotile A with human red blood cells, red cell membranes (ghosts) and liposomes made of dipalmitoyl phosphatidyl choline for the adsorption experiments. The work was done in Orléans and Créteil, France.
• Exposure: Chrysotile fibres of centimetre length were placed in 25 ml of reagent at 40°C. Reagents included oxalic acid (0.1 N and a dilute concentration), 10-2 N hydrochloric acid, and Krebs cycle compounds (pyruvic, oxaloacetic, malic, succinic, lactic and others; the list is partly unreadable). Separately, UICC chrysotile A was exposed to red blood cells, red cell ghosts and phospholipid liposomes.
• Main results:
  • In 10-2 N hydrochloric acid, the dissolution curve was mainly a plateau from 4 to 25 hours. The authors said this corresponds to leaching of magnesium from the first mineral layer, followed by a change in mechanism.
  • In dilute oxalic acid, leaching of magnesium from the first mineral layer was not completed under the experimental conditions.
  • Assuming dissociation of chrysotile is the rate-limiting step, the authors estimated the leaching rate of the fibres at 0.3 nm/hr (22°C) to 25 nm/hr (80°C).
  • Reactivity of the Krebs cycle acids was variable and always less than that of oxalic acid at the same concentration. The authors said pyruvic and citric acids probably play some part in altering chrysotile.
  • Phospholipid adsorption was followed through the phosphorus-to-silicon photoelectron peak ratio, plotted against the initial concentration of dipalmitoyl phosphatidyl choline. A plateau was reached at an initial concentration of about 200 micrograms per millilitre.
  • Assuming the plateau corresponds to complete coverage of the chrysotile surface, the calculated area per phospholipid molecule was compatible with adsorption of a bilayer.
  • For red blood cell membranes (ghosts), the nitrogen peak indicated that both proteins and phospholipids must be adsorbed onto chrysotile fibres.
  • In preliminary experiments, phospholipid adsorption on leached fibres was much lower than on unleached fibres (the sentence is partly unreadable).
• The authors' conclusion: The authors concluded that unleached or first-layer-leached chrysotile surfaces are especially suitable for adsorbing proteins and phospholipids. When leaching is great enough, molecules become incorporated inside micropores. They said it is difficult at present to relate these physicochemical mechanisms to biological explanations of cancer, but that there is an interplay between physicochemical processes, haemolytic activity and cytotoxicity of fibres.
• Limitations the authors state:
  • For red cell membranes (ghosts), results varied, and the authors said no simple model could yet explain the data.

Topics

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

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