Surface charge heterogeneity in amphibole cleavage fragments and asbestos fibers

Our plain-English summary of Surface charge heterogeneity in amphibole cleavage fragments and asbestos fibers, by J.E. Schiller, S.L. Payne, S.E. Khalafalla (Science, 1980).

The study

• Authors: J.E. Schiller, S.L. Payne, S.E. Khalafalla
• Journal: Science
• Published: 1980;209(4464):1530-2
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aspect ratio and electrophoretic mobility data for amphibole particles reveal that short fibers and blocky cleavage fragments have a smaller net charge than highly elongated particles. Asbestos fibers and cleavage fragments of the same dimensions exhibit the same net negative surface charge but positively charged ends and negatively charged lateral surfaces.

In plain English

This laboratory study came from the U.S. Bureau of Mines Twin Cities Research Center. It did not study people or disease. The authors measured how fast single mineral particles moved in an electric field (electrophoretic mobility, a measure of surface charge). They photographed each particle to find its length-to-width ratio (aspect ratio), which ranged from 1 up to 40. Four amphibole samples were tested: crocidolite and grunerite asbestos from the International Union Against Cancer, acicular tremolite, and riebeckite. Blocky particles had lower mobility, which rose rapidly as particles became more elongated. All four samples behaved the same way. No difference in mobility was seen between particles from asbestiform and nonasbestiform minerals. A control test indicated that the lower mobility of blocky particles reflected a smaller net negative charge, not only their shape. The authors concluded that amphibole particles appear to carry opposite charges on their long sides and their ends. Short fibers and blocky cleavage fragments therefore carry less net charge than elongated ones. The authors noted large measurement uncertainties.

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 experiment: microelectrophoresis of individual mineral particles, each photographed to measure its aspect ratio, with a mathematical model fitted to the data
• Who was studied: individual amphibole particles (fibers and cleavage fragments) suspended in water, with aspect ratios from 1 up to 40. No human subjects. The number of particles is not stated.
• Exposure: four amphibole samples: crocidolite and grunerite asbestos (UICC samples), acicular tremolite (from Canaan, Connecticut) and riebeckite (from El Paso County, Colorado). The study measured particle surface charge, not human exposure.
• Main results:
  • Across the samples, electrophoretic mobility was lower for blocky particles and rose rapidly with increasing aspect ratio.
  • All four samples behaved alike. No difference in electrophoretic mobility was seen between particles from asbestiform and nonasbestiform minerals.
  • In a control test with grunerite asbestos and crocidolite, blocky particles had relative mobilities of 0.57 and 0.63 (compared with elongated particles moving parallel to the field). Shape alone predicted 0.85 and 0.87. The authors concluded that the lower mobility of blocky particles reflects a smaller net negative charge.
  • For all points combined, the fitted limiting mobilities in Table 1 were -2.7 (lateral surfaces) and +4 (basal surfaces, the particle ends), in (micrometers per second) per (volt per centimeter).
• The authors' conclusion: The authors concluded that amphibole particles appear to have opposite surface charge on lateral and basal surfaces. As a result, short amphibole fibers and blocky cleavage fragments have a smaller net charge than elongated fibers and cleavage fragments.
• Limitations the authors state:
  • The data points showed considerable scatter because both the mobility and the aspect ratio measurements had rather large experimental uncertainties.
  • Aspect ratios measured from often blurred photographs had a standard deviation of 15 percent. Individual mobility values had a standard deviation of about 10 percent.
  • The fitted limiting value for the basal (end) surfaces was somewhat imprecise because the curve is very steep at low aspect ratios.
  • Particle shape may have contributed somewhat to the lower mobilities of the particles with the lowest aspect ratios.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Cleavage Fragment, Aspect Ratio (Length-to-diameter ratio).

Related studies

• An inter-laboratory study to determine the effectiveness of procedures for discriminating amphibole asbestos fibers from amphibole cleavage fragments in fiber counting by phase-contrast microscopy — M. Harper, E.G. Lee, et al. (2012)
• Asbestos surface charge heterogeneity and biological effects — W.G. Light (1981)
• An evaluation of the risks of lung cancer and mesothelioma from exposure to amphibole cleavage fragments — J.F. Gamble, G.W. Gibbs (2008)
• Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments — V.L. Roggli, C.L. Green (2019)
• The carcinogenicity of WHO fibers of silicon carbide: SiC whiskers compared to cleavage fragments of granular SiC — K. Rödelsperger, B. Brückel (2006)
• Assessment of the pathogenic potential of asbestiform vs. nonasbestiform particulates (cleavage fragments) in in vitro (cell or organ culture) models and bioassays — B.T. Mossman (2008)

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