Surface charge and asbestos toxicity

Our plain-English summary of Surface charge and asbestos toxicity, by W.G. Light, E.T. Wei (Nature, 1977).

The study

• Authors: W.G. Light, E.T. Wei
• Journal: Nature
• Published: 1977;265(5594):537-9
• Cited by: 102 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This was a short laboratory report. The authors studied whether the surface charge of asbestos fibres is related to their ability to burst red blood cells (haemolytic activity). They tested two reference samples of the International Union against Cancer: chrysotile A and the amphibole crocidolite. The fibres were soaked (leached) in Tyrode's solution, a physiological buffer, or in dilute hydrochloric acid. They then measured surface charge and tested the fibres on sheep red blood cells. Before leaching, the zeta potential at pH 7.4 (the authors' measure of surface charge) was +44.5 mV for chrysotile A and -43.5 mV for crocidolite. With leaching, its absolute size fell for chrysotile A and rose for crocidolite. Haemolytic activity shifted in proportion, with a correlation the authors reported as significant (P<0.01). The authors concluded that surface charge matters for haemolytic activity and that fibre dissolution can activate or inactivate fibres. They suggested this could explain why the two asbestos classes differ in short-term laboratory effects but not clearly in long-term toxicity. The study measured laboratory red cell damage, not disease in people or animals.

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) experiment on asbestos fibres and red blood cells
• Who was studied: Two International Union against Cancer (UICC) reference asbestos samples, chrysotile A and the amphibole crocidolite, tested on washed sheep red blood cells (erythrocytes)
• Exposure: Fibres were leached as 0.5% suspensions in Tyrode's (physiological buffer) solution, 0.01 M HCl or 0.1 M HCl. The HCl leachings lasted 1 day, and the Tyrode's leaching was followed for 21 days. For the red cell tests, samples of equal surface area (20 mg crocidolite, 7.7 mg chrysotile A) were used.
• Main results:
  • Before leaching, at pH 7.4, the zeta potentials (used to represent surface charge) were similar in size but opposite in sign: +44.5 mV for chrysotile A and -43.5 mV for crocidolite
  • With leaching, the absolute size of the zeta potential decreased for chrysotile A and increased for crocidolite
  • After 21 days of leaching in Tyrode's solution, the absolute zeta potential values were 34.0 mV for chrysotile A and 58.5 mV for crocidolite
  • For fibres leached in HCl and Tyrode's solution, the absolute zeta potential was correlated with haemolytic activity for both types of asbestos. The authors called this correlation highly significant (P<0.01). The figure legend gives r = 0.96 for chrysotile A and r = 0.97 for crocidolite.
  • The positively charged chrysotile was initially more haemolytic than the negatively charged amphibole
• The authors' conclusion: The authors concluded that the results confirm the importance of surface charge to haemolytic activity. They also concluded that fibre dissolution can change surface charge and so activate or inactivate fibres. They suggested that continuous leaching in the body could make the biological activities of chrysotiles and amphiboles converge. This could explain why the two classes differ in short-term in vitro effects but not clearly in long-term toxicity.

Related studies

• Surface charge and hemolytic activity of asbestos — W.G. Light, E.T. Wei (1977)
• Asbestos surface charge heterogeneity and biological effects — W.G. Light (1981)
• Iron topochemistry and surface reactivity of amphibole asbestos: relations with in vitro toxicity — A. Pacella, G.B. Andreozzi, et al. (2012)
• Surface charge heterogeneity in amphibole cleavage fragments and asbestos fibers — J.E. Schiller, S.L. Payne, et al. (1980)
• Ascorbic acid modifies the surface of asbestos: possible implications in the molecular mechanisms of toxicity — G. Martra, M. Tomatis, et al. (2003)
• Adsorption of proteins by chrysotile and crocidolite: role of molecular weight and charge density — F. Valerio, D. Balducci, et al. (1987)

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