Surface and bulk modifications of amphibole asbestos in mimicked gamble's solution at acidic PH

Our plain-English summary of Surface and bulk modifications of amphibole asbestos in mimicked gamble's solution at acidic PH, by A. Pacella, P. Ballirano, M. Fantauzzi, et al (Scientific Reports, 2021).

The study

• Authors: A. Pacella, P. Ballirano, M. Fantauzzi, A. Rossi, E. Nardi, G. Capitani, L. Arrizza, M.R. Montereali
• Journal: Scientific Reports
• Published: 2021;11(1):14249
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This study aimed at investigating the surface modifications occurring on amphibole asbestos (crocidolite and tremolite) during leaching in a mimicked Gamble's solution at pH of 4.5 and T = 37 °C, from 1 h up to 720 h. Results showed that the fibre dissolution starts with the release of cations prevalently allocated at the various M- and (eventually) A-sites of the amphibole structure (incongruent dissolution). The amount of released silicon, normalized to fibre surface area, highlighted a leaching faster for the crocidolite sample, about twenty times higher than that of tremolite. Besides, the fast alteration of crocidolite promotes the occurrence of Fe centres in proximity of the fibre surface, or possibly even exposed, particularly in the form of Fe(II), of which the bulk is enriched with respect to the oxidized surface. Conversely, for tremolite fibres the very slow fibre dissolution prevents the underlying cations of the bulk to be exposed on the mineral surface, and the iron oxidation, faster than the leaching process, significantly depletes the surface Fe(II) centres initially present. Results of this work may contribute to unravel possible correlations between surface properties of amphibole asbestos and its long-term toxicity.

© 2021. The Author(s).

In plain English

In this experiment, the authors placed two amphibole asbestos samples in an artificial lung fluid (a mimicked Gamble's solution) at pH 4.5 and 37 °C for 1 to 720 hours. The samples were UICC crocidolite from Koegas Mine, South Africa, and fibrous tremolite from Montgomery County, Maryland. No people, animals or cells were studied. Per unit of fibre surface area, silicon was released about 19 times faster from crocidolite than tremolite. Crocidolite lost at most about 2% of its silicon and 7% of its magnesium. Tremolite lost well below 0.5% of its silicon, magnesium and calcium, although the silicon and magnesium figures may be slightly overestimated because of a serpentine impurity. At the crocidolite surface, the Fe(II) share of iron rose from 20% to 30% within 48 hours. At the tremolite surface it fell from about 30% to about 11% in the first hour. The authors, noting that conditions were far from a real cellular environment, concluded that the fibres' different biodurability may lead to different behaviour in the body and that their toxic potential should be compared.

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 (acellular, in vitro) dissolution experiment on mineral fibre samples, analysed with several techniques (electron microscopy, ICP-OES, XPS, X-ray powder diffraction)
• Who was studied: Two mineral samples: UICC crocidolite from Koegas Mine, South Africa, and a fibrous tremolite from Montgomery County, Maryland, USA. No human or animal subjects.
• Exposure: Crocidolite and tremolite fibres (20 mg in 40 mL) incubated in a mimicked Gamble's solution at pH 4.5 and 37 °C for 1, 24, 48, 168 and 720 hours
• Main results:
  • Silicon release rate, per equivalent surface area, was about 19 times larger for UICC crocidolite than for tremolite (0.007 versus 0.0004 micromoles per hour per square metre)
  • Crocidolite: estimated maximum release was about 2% of the fibres' total silicon and about 7% of their total magnesium
  • Tremolite: release of silicon, magnesium and calcium was well below 0.5% (0.09%, 0.12% and 0.28%, respectively). The silicon and magnesium amounts may be slightly overestimated because they include release from a serpentine impurity.
  • Crocidolite surface: the Fe(II) signal rose from 20% of total iron in the untreated sample to 30% after 48 hours, then stayed unchanged
  • Tremolite surface: the Fe(II) component fell from about 30% to about 11% of total iron in the first hour of incubation
  • Microscopy showed less marked surface alteration for tremolite than for crocidolite
• The authors' conclusion: The authors concluded that the different biodurability of crocidolite and tremolite may be responsible for possibly different behaviour of the two fibres in the body, and that their toxic potential should be compared
• Limitations the authors state:
  • The experimental conditions were far from mimicking a real cellular environment; they were chosen to speed up dissolution
  • Silicon and magnesium release from tremolite may be slightly overestimated because it includes release from a serpentine impurity
  • Sodium release could not be measured because the test solution itself contained a high amount of sodium

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Asbestos, Crocidolite, Tremolite, Cation, A-site, Amphibole Group.

Related studies

• Dissolution Reaction and Surface Modification of UICC Amosite in Mimicked Gamble's Solution: A Step towards Filling the Gap between Asbestos Toxicity and Its Crystal Chemical Features — A. Pacella, P. Ballirano, et al. (2023)
• Thermal inertization of amphibole asbestos modulates Fe topochemistry and surface reactivity — A. Pacella, M. Tomatis, et al. (2020)
• Surface chemistry and surface reactivity of fibrous amphiboles that are not regulated as asbestos — M. Fantauzzi, A. Pacella, et al. (2012)
• A study of surface property changes in rat mesothelial cells induced by asbestos using aqueous two-phase polymer solutions — M.M. Lee, F.H. Green, et al. (1993)
• Asbestos surface provides a niche for oxidative modification — H. Nagai, T. Ishihara, et al. (2011)
• Synthetic chrysotile nanocrystals as a reference standard to investigate surface-induced serum albumin structural modifications — P. Sabatino, L. Casella, et al. (2007)

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