Iron topochemistry and surface reactivity of amphibole asbestos: relations with in vitro toxicity

Our plain-English summary of Iron topochemistry and surface reactivity of amphibole asbestos: relations with in vitro toxicity, by A. Pacella, G.B. Andreozzi, J. Fournier, et al (Analytical and Bioanalytical Chemistry, 2012).

The study

• Authors: A. Pacella, G.B. Andreozzi, J. Fournier, L. Stievano, F. Giantomassi, G. Lucarini, M.R. Rippo, A. Pugnaloni
• Journal: Analytical and Bioanalytical Chemistry
• Published: 2012;402(2):871-81
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Chemical reactivity of asbestos tremolite from Italy and USA localities and Union Internationale Contre le Cancer (UICC) crocidolite was studied in relation to Fe content, oxidation state, and structural coordination. Direct correlation between amount of Fe(2+) at the exposed M(1) and M(2) sites of the amphibole structure and fiber chemical reactivity was established. The in vitro toxicity of the same samples was investigated on human alveolar A549 cell line. Relationship between crystal-chemical features and cell toxicity is not straightforward. UICC crocidolite has Fe content and chemical reactivity largely higher than that of tremolite samples, but all show comparable in vitro toxic potential. Results obtained evidenced that Fe topochemistry is not a primary factor for induced cell toxicity, though it accounts for asbestos chemical reactivity (and possibly genotoxicity).

In plain English

In this laboratory study, not a study of people, the authors tested four fibrous tremolite asbestos samples, three from Italy (Ala di Stura, Mt. Rufeno and Castelluccio Superiore) and one from Maryland, USA, plus a reference sample of UICC crocidolite. They measured hydroxyl radical production by each sample. They also measured fatty-acid breakdown (lipid peroxidation) for every sample except Castelluccio Superiore tremolite, of which too little was available. They related these results to the iron in the fibers. They also exposed human A549 lung cells to 50 μg/ml of the samples. The crocidolite contained about 10 to 20 times more iron than the tremolites and was more reactive. Hydroxyl radical production tracked the ferrous iron at exposed sites in the fiber structure. In a cell viability test, all samples except Mt. Rufeno tremolite significantly reduced viability, and Ala di Stura tremolite was more toxic than crocidolite. The authors reported that overall, tremolite toxicity was not markedly different from crocidolite toxicity. The authors concluded that iron chemistry accounts for chemical reactivity but is not a primary factor in cell toxicity. They proposed that iron chemistry may relate more to genetic damage.

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 study: chemical surface-reactivity tests on fiber samples (hydroxyl radical production measured by EPR, and lipid peroxidation) plus in vitro toxicity tests on a human cell line
• Who was studied: Fiber samples: four fibrous tremolites and one reference sample. Three tremolites came from Italian ophiolitic outcrops (Ala di Stura, Mt. Rufeno, Castelluccio Superiore) and one from Maryland (Montgomery County), USA. The reference sample was UICC crocidolite. The cells tested were the human alveolar A549 cell line.
• Exposure: Tremolite asbestos and UICC crocidolite. Cells were exposed at 50 μg/ml for 24 and 48 h, and for 96 h in the hypodiploid nuclei analysis. Chemical tests used 25 mg of ground sample.
• Main results:
  • The tremolite samples contained about ten times less iron than crocidolite (10 to 20 times less, per the conclusions). The Maryland tremolite had almost double the iron of the Italian tremolites.
  • UICC crocidolite produced much more hydroxyl radical than the tremolite samples, and Maryland tremolite was slightly more reactive than the Italian ones. Radical production correlated with the amount of Fe2+ at the exposed M(1) and M(2) sites.
  • All samples tested for lipid peroxidation were active in it (Castelluccio Superiore tremolite was not tested). UICC crocidolite showed the highest malonaldehyde (MDA) formation, and the tremolites were markedly lower. Monoaldehyde results were less systematic: Mt. Rufeno tremolite was as reactive as crocidolite.
  • In the MTT viability test, all fiber-treated cells showed significant decreases in viability compared with control cells, except those treated with Mt. Rufeno tremolite. Ala di Stura tremolite was more toxic than UICC crocidolite.
  • Ki-67 detection showed marked decreases in cell proliferation for all fiber-treated cells compared with controls, with no significant differences among the samples.
  • Signs of cell stress were strongest in cells treated with Ala di Stura and Maryland tremolites. These signs were pycnotic nuclei, hypodiploid nuclei and a depressed G1 cell-cycle phase. Hypodiploid peaks were not seen with Mt. Rufeno tremolite.
  • Overall, the in vitro toxicity of the tremolite samples was not markedly different from that of UICC crocidolite.
• The authors' conclusion: The authors concluded that there is a direct correlation between iron topochemistry and fiber chemical reactivity. They found the relationship with in vitro cell toxicity was not straightforward: all samples had comparable toxic potential despite crocidolite's much higher iron content and reactivity. They proposed that iron topochemistry should be related more to genotoxicity than to cytotoxicity.
• Limitations the authors state:
  • Lipid peroxidation data are not available for Castelluccio Superiore tremolite because there was not enough of the sample.
  • No correlation was found between hydroxyl radical production and monoaldehyde generation; the authors described this as an open problem.
  • For the pycnotic nuclei and FACS analyses, standard deviations were not shown because the values came from two experiments.

Topics

Medical terms in this study, explained in our Lexicon: Surface Reactivity, Amphibole Asbestos, Tremolite, UICC, Crocidolite, Amphibole Group, Genotoxicity.

Related studies

• Surface chemistry and surface reactivity of fibrous amphiboles that are not regulated as asbestos — M. Fantauzzi, A. Pacella, et al. (2012)
• Thermal inertization of amphibole asbestos modulates Fe topochemistry and surface reactivity — A. Pacella, M. Tomatis, et al. (2020)
• Cyto-genotoxicity of amphibole asbestos fibers in cultured human lung epithelial cell line: role of surface iron — R.K. Srivastava, M. Lohani, et al. (2010)
• Chemical characterization and reactivity of iron chelator-treated amphibole asbestos — J. Gold, H. Amandusson, et al. (1997)
• In vitro determinants of asbestos fiber toxicity: effect on the relative toxicity of Libby amphibole in primary human airway epithelial cells — K.E. Duncan, P.M. Cook, et al. (2014)
• Using in vitro iron deposition on asbestos to model asbestos bodies formed in human lung — Z. Shen, D. Bosbach, et al. (2000)

Browse more research in Analytical and Bioanalytical Chemistry, or return to medical research.