The release of iron from different asbestos structures by hydrogen peroxide with concomitant O2 generation

Our plain-English summary of The release of iron from different asbestos structures by hydrogen peroxide with concomitant O2 generation, by A.J. Ghio, D.E. Taylor, J.G. Stonehuerner, et al (Biometals, 1998).

The study

• Authors: A.J. Ghio, D.E. Taylor, J.G. Stonehuerner, C.A. Piantadosi, A.L. Crumbliss
• Journal: Biometals
• Published: 1998;11(1):41-7
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Treatment of aqueous suspensions of different asbestos fibers (amosite, anthophyllite, chrysotile, and crocidolite) at 0-4 degrees C and pH 7.2 with H2O2 results in the consumption of H2O2 with concomitant release of iron and production of O2. During incubations, [H2O2] decreased in proportion to the mass of the suspended fiber, the duration of incubation, and the initial [H2O2]. The consumption of H2O2, production of O2 and release of iron all vary synergistically with the structure of the asbestos fiber. Release of silicon during the incubation was small relative to the decrement in [H2O2], reflecting a lack of dissolution of the fiber. The data are consistent with a redox process for the release of surface bound iron and it is significant that iron release occurs in the absence of a Fe(II) or Fe(III) chelator. The implications of iron release from the asbestos surface may be important in inflammatory disorders in which both silicate bound iron and H2O2 accumulate.

In plain English

This was a laboratory chemistry study. No people or animals were studied. The authors mixed four UICC asbestos samples (amosite, anthophyllite, chrysotile and crocidolite) with hydrogen peroxide in a buffer at pH 7.2, mostly at 0 to 4°C, to see whether the peroxide frees iron from the fibers. All four fiber types used up hydrogen peroxide, produced oxygen and released iron into the liquid, and chrysotile showed the most of each. In tests with crocidolite, more fiber and more peroxide led to more peroxide being used up, and more peroxide released more iron. Silicon release was described as identical with or without peroxide, which the authors took to mean the fibers were not dissolving. Of several comparison minerals, only an iron(III) oxide produced a statistically significant decrease in peroxide in these tests. The authors concluded that the iron release was likely a reductive process involving iron bound to the fiber surface, since chrysotile has no iron in its crystal lattice, and that no chelator was needed. They described their evidence for this process as indirect.

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) chemistry experiment on asbestos fiber suspensions; no human or animal subjects
• Who was studied: Four UICC asbestos fiber samples (amosite, anthophyllite, chrysotile, crocidolite) from Duke Scientific Corporation, with surface areas provided by UICC for all four. Silica (minusil-5) and the mineral oxides FeO, Fe2O3, Fe3O4, Al2O3 and MgO served as comparison materials.
• Exposure: Hydrogen peroxide at final concentrations from 0.0 to 1000.0 µM, with 0.0 to 20.0 mg of fiber in buffer at pH 7.2, mostly at 0 to 4°C (oxygen production was measured at 30°C)
• Main results:
  • Chrysotile used up the most hydrogen peroxide and released the most iron of the four fibers. It also had the highest surface area of the four: 26.8 plus or minus 0.7 m2/g, against 5.7 for amosite, 11.8 for anthophyllite and 8.3 for crocidolite.
  • Hydrogen peroxide consumption after a fixed time increased with the amount of fiber suspended (tested with crocidolite) and with the starting peroxide concentration
  • Oxygen was produced along with peroxide consumption. The highest oxygen production rate was for chrysotile.
  • Fibers in buffer alone did not release an appreciable amount of iron. With hydrogen peroxide, all four fibers released significant amounts of chelatable iron, the most from chrysotile.
  • With crocidolite, the amount of iron released after a fixed time increased with the hydrogen peroxide concentration
  • The authors described silicon release as identical with and without hydrogen peroxide over 120 hours. In micromoles of silicon per gram of dust, without versus with peroxide: amosite 5 vs 4, anthophyllite 13 vs 14, chrysotile 65 vs 70, crocidolite 11 vs 12.
  • Among the comparison minerals (SiO2, FeO, Fe2O3, Fe3O4, Al2O3, MgO), only Fe2O3 produced a statistically significant decrease in hydrogen peroxide
• The authors' conclusion: The authors concluded that hydrogen peroxide likely releases iron from asbestos by a reductive process acting on iron bound to the fiber surface, and that this release does not require a chelator
• Limitations the authors state:
  • The authors stated that the evidence for a redox process is indirect
  • The method used to measure iron could not distinguish between the oxidation states of iron
  • Chelating agents that could detect iron(II) directly were not usable, because they stick to the fiber surfaces and also act as reducing agents
  • A role for hydroxyl radical could not be fully ruled out, because the HEPES buffer used scavenges hydroxyl radicals

Topics

Medical terms in this study, explained in our Lexicon: Amosite, Anthophyllite, Chrysotile, Crocidolite, Silicate.

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