Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 2: Oxidant activity of the fibers

Our plain-English summary of Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 2: Oxidant activity of the fibers, by F. Turci, M. Tomatis, E. Gazzano, et al (Journal of Toxicology and Environmental Health. Part a, 2005).

The study

• Authors: F. Turci, M. Tomatis, E. Gazzano, C. Riganti, G. Martra, A. Bosia, D. Ghigo, B. Fubini
• Journal: Journal of Toxicology and Environmental Health. Part a
• Published: 2005;68(1):21-39
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The asbestiform mineral balangeroite [(Mg,Fe2+,Fe3+,Mn2+)42Si16O54(OH)36], whose toxic potential is unknown, is associated with chrysotile asbestos in the western Alps (Balangero mine, Piedmont, Italy). In order to examine whether such fibers may contribute to the oxidative damage produced by local asbestos dusts when inhaled, balangeroite was studied by means of both cell-free and cellular tests, comparing the results with those concerning the most pathogenic asbestos form, crocidolite. Similarly to the crocidolite surface, iron was mobilized from balangeroite by chelators, to a different extent: deferoxamine > ascorbic acid > ferrozine. Poorly coordinated surface ions, as evaluated from the adsorption of NO as a probe molecule (by both calorimetry and infrared spectroscopy), are even more abundant on balangeroite than on crocidolite. The spin trapping technique shows that surface iron-derived Fenton activity (HO* from H2O2) is similar for the two fiber types, while a pretreatment in ascorbic acid, by reducing previously oxidized surface iron, activates the potential to cleave a C-H bond (yielding *CO2- from formate anion). Balangeroite, like crocidolite, produces nitrite accumulation, lipid peroxidation, and NO synthase activation in a human lung epithelial cell line (A549). All these findings, regarded as features related to the toxic potential of asbestos, suggest that balangeroite may be a potentially hazardous fiber per se and could be partly responsible for lung diseases reported in epidemiological studies in exposed miners.

In plain English

This laboratory study, involving no people or animals, tested whether balangeroite, a fibrous mineral found with chrysotile asbestos at Italy's Balangero mine, shows effects linked to asbestos toxicity. It was compared with UICC crocidolite in cell-free tests and in human lung cells (A549). With hydrogen peroxide present, both fibers produced very similar amounts of hydroxyl radicals. Balangeroite alone made almost no carbon-centered radicals, but it did after ascorbic acid treatment. After 7 days, chemical agents released similar amounts of iron from both fibers. Per unit of surface, balangeroite bound more nitric oxide than crocidolite. After 24 hours at the highest dose (12 µg/cm2), both fibers significantly raised nitric oxide production. At that dose, a marker of lipid damage (TBARS, picomoles per milligram of cell protein; n = 12 each) rose significantly from 11.3 ± 0.36 in control cells to 70.47 ± 3.92 with balangeroite and 44.45 ± 2.1 with crocidolite. Lower balangeroite doses did not significantly change this marker. The authors concluded that balangeroite appears a good candidate for initiating oxidative damage in living cells. Balangeroite's surface area was twice crocidolite's, they noted.

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) study: cell-free chemical tests and cell-culture tests, comparing balangeroite with UICC crocidolite as positive control
• Who was studied: A sample of balangeroite from the Balangero mine (Piedmont, Italy), compared with UICC crocidolite; cell tests used the human lung epithelial cell line A549. No human subjects or animals.
• Exposure: Balangeroite fibers (mostly respirable: diameter less than 3 µm, aspect ratio at least 3:1; surface area 16 m2/g) and UICC crocidolite (surface area 8 m2/g). In cell tests, cells were exposed for 24 h to 0.24, 2.4 or 12 µg/cm2 balangeroite or 12 µg/cm2 crocidolite.
• Main results:
  • With hydrogen peroxide, hydroxyl radical generation was very similar for balangeroite and crocidolite, and it stayed steady over the 1-hour test
  • Untreated balangeroite produced minimal or no carbon-centered radicals from formate. After ascorbic acid treatment it did, and longer ascorbic acid incubation made the fibers more reactive.
  • After 7 days, iron released (nmol/mg of solid) was 150 with deferoxamine, 4 with ferrozine and 27 with ascorbate for balangeroite. For UICC crocidolite the figures were 180, 10 and 30.
  • Nitric oxide uptake per unit surface was higher on balangeroite than on crocidolite: total 2.6 vs 1.9 µmol/m2, and the irreversibly bound part 2.1 vs 0.9 µmol/m2. The authors read this as more reactive surface iron on balangeroite.
  • In A549 cells, 12 µg/cm2 of either fiber significantly increased nitrite accumulation and NO synthase activity compared with unexposed cells. For balangeroite the NO synthase increase was smaller but still significant at 2.4 µg/cm2, and absent at 0.24 µg/cm2.
  • Lipid peroxidation markers (TBARS, pmol/mg cell protein) were 11.3 ± 0.36 in control cells (n = 12). After 24 h at 12 µg/cm2 they rose significantly to 70.47 ± 3.92 with balangeroite and 44.45 ± 2.1 with crocidolite (n = 12 each). At 2.4 µg/cm2, balangeroite did not significantly change TBARS, although it still significantly increased NO synthesis.
• The authors' conclusion: The authors concluded that balangeroite appears a good candidate for initiating oxidative damage in living cells. The fibers were active in all tests, with results similar to crocidolite even after allowing for the difference in surface area.
• Limitations the authors state:
  • The balangeroite sample had twice the surface area of crocidolite, and tests used equal masses. The authors state that where balangeroite was more reactive, the excess must first be attributed to its larger surface area.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Balangero mine, Balangero, about 20 km north of Turin, Piedmont

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestiform, Balangeroite, Chrysotile, Balangero Mine, Crocidolite, Infrared Spectroscopy (IR).

Related studies

• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 3: Depletion of antioxidant defenses — E. Gazzano, C. Riganti, et al. (2005)
• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 1: Identification and characterization — C. Groppo, M. Tomatis, et al. (2005)
• The effect of weathering on ecopersistence, reactivity, and potential toxicity of naturally occurring asbestos and asbestiform minerals — S. Enrico Favero-Longo, F. Turci, et al. (2009)
• N-acetyl L-cysteine attenuates oxidant-mediated toxicity induced by chrysotile fibers — F. Afaq, P. Abidi, et al. (2000)
• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• Iron-loaded synthetic chrysotile: a new model solid for studying the role of iron in asbestos toxicity — E. Gazzano, F. Turci, et al. (2007)

Browse more research in Journal of Toxicology and Environmental Health. Part a, or return to medical research.