Asbestos health hazard: a spectroscopic study of synthetic geoinspired Fe-doped chrysotile

Our plain-English summary of Asbestos health hazard: a spectroscopic study of synthetic geoinspired Fe-doped chrysotile, by E. Foresti, E. Fornero, I.G. Lesci, et al (Journal of Hazardous Materials, 2009).

The study

• Authors: E. Foresti, E. Fornero, I.G. Lesci, C. Rinaudo, T. Zuccheri, N. Roveri
• Journal: Journal of Hazardous Materials
• Published: 2009;167(1-3):1070-9
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The chrysotile fibres toxicity appears correlated to the redox activity of iron present in the chrysotile structure. In fact the generation of reactive oxygen species and other radicals appears catalyzed by iron ions and closely related to Fe ions organization in specific crystallographic sites having a capability to activate free radical generation. The Fe substitution to Mg and/or Si in the chrysotile structure appears important for asbestos health hazard investigation. Infrared and Raman spectroscopic analyses have been utilized to investigate Mg and/or Si ions replacement by Fe ions in chrysotile structure as a function of the Fe doping extent. Geoinspired synthetic chrysotile at different Fe doping extents has been obtained as unique phase by hydrothermal reaction in the presence or not of metallic Fe in the synthetic environment. The results highlight that Fe can replace both Mg and Si, differently modifying the chrysotile structure as a function of the Fe doping extent and the Fe doping process. The contemporary iron substitution into the octahedral and tetrahedral sheets reveals an appreciable increase of the dehydroxylation temperature which occurs at higher temperature than for iron-free sample. The results highlight the role of Fe substitution in the asbestos structure influencing the health hazard of biological systems.

In plain English

This was a laboratory study of man-made (synthetic) chrysotile, not a study of people, animals or cells. The authors, working in Italy, grew chrysotile nanotubes in a heated pressure reactor, either iron-free or doped with iron at 0.29% to 1.78% by weight. One series, marked (*), was made in a vessel of an alloy containing 6.5% iron. The other, marked (X), was made in a stainless steel vessel, which the authors treated as equivalent to having metallic iron present. They used infrared and Raman spectroscopy to see where the iron sat in the crystal structure. In the (*) series, iron appeared to replace magnesium in the octahedral sites. In the (X) series, iron also replaced silicon in the tetrahedral sites, especially at 0.94% iron or more, flattening the structure toward that of the mineral lizardite. In heating tests, the water-loss event occurred at 615 °C for iron-free chrysotile. For samples with 0.67% iron, it occurred at 620 °C in the (*) series and at 608 °C in the (X) series. The authors concluded that this effect of iron on structural stability must be considered when judging the hazard of iron in asbestos fibres. No toxicity testing was done in this study.

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 synthesis and spectroscopic study of synthetic chrysotile (infrared and Raman spectroscopy, plus differential thermal analysis); no human, animal or cell testing
• Who was studied: Synthetic ('geoinspired') chrysotile nanocrystals made at the University of Bologna, Italy. One sample was iron-free. The (*) series contained 0.67, 0.81, 1.67 and 1.78% wt Fe and was made in a vessel of alloy C-276 (6.5% wt Fe). The (X) series contained 0.29, 0.67, 0.71, 0.94 and 1.37% wt Fe and was made in a T316 stainless steel vessel, described as 65% wt Fe.
• Exposure: Iron doping of synthetic chrysotile at different extents, made with or without metallic iron present in the synthesis environment (no biological exposure was studied)
• Main results:
  • Infrared spectra: in the (*) series (made without metallic Fe), the band shifts were consistent with iron in octahedral (magnesium) sites. In the (X) series (made with metallic Fe available), they supported iron in tetrahedral (silicon) sites, flattening the curved layers.
  • Raman spectra of the (X) series: up to 0.71% wt Fe, the shifts reflected magnesium-iron substitution in octahedral sites. At 0.94% wt Fe or more, the silicate bending modes also shifted (from 392 to 389 and from 348 to 345 cm-1), indicating iron-silicon substitution and a flattened, lizardite-like morphology. Crystallinity was strongly affected at the higher doping.
  • Raman spectra of the (*) series: the authors hypothesized that iron preferentially replaced magnesium in octahedral sites, increasing sample crystallinity.
  • Thermal analysis: the dehydroxylation event occurred at 615 °C for iron-free chrysotile. For samples with 0.67% wt Fe, it occurred at 620 °C in the (*) series (iron replacing magnesium) and at 608 °C in the (X) series (iron in both octahedral and tetrahedral sheets).
  • For the (X) series with combined octahedral and tetrahedral substitution, the article body describes a decrease in dehydroxylation temperature to 608 °C, which the authors ascribed to destabilization of the structure.
• The authors' conclusion: The authors concluded that Fe can replace both Mg and Si. How it modifies the chrysotile structure depends on the extent of doping and on whether metallic Fe was present during synthesis. They stated that this effect on structural stability must be considered when evaluating the hazard of iron in asbestos fibres on living systems.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Reactive Oxygen Species (ROS), Crystallographic Site, Dehydroxylation.

Related studies

• Adsorption of bovine serum albumin onto synthetic Fe-doped geomimetic chrysotile — A. Adamiano, I.G. Lesci, et al. (2015)
• Spectroscopic characterization of Fe-doped synthetic chrysotile by EPR, DRS and magnetic susceptibility measurements — E. Borghi, M. Occhiuzzi, et al. (2010)
• Iron-loaded synthetic chrysotile: a new model solid for studying the role of iron in asbestos toxicity — E. Gazzano, F. Turci, et al. (2007)
• International symposium on the health hazard evaluation of fibrous particles associated with taconite and the adjacent duluth complex. Introduction — R.P. Nolan (2008)
• Adsorption of human serum albumin on the chrysotile surface: a molecular dynamics and spectroscopic investigation — R. Artali, A. Del Pra, et al. (2008)
• Interaction of bovine serum albumin with chrysotile: spectroscopic and morphological studies — G. Falini, E. Foresti, et al. (2006)

Browse more research in Journal of Hazardous Materials, or return to medical research.