Environmental Health Perspectives 105, Supplement 5, September 1997

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Chemical Characterization and Reactivity of Iron Chelator-treated Amphibole Asbestos

Julie Gold, 1 Helena Amandusson, 1 Anatol Krozer, 1 Bengt Kasemo, 1 Tore Ericsson, 2 Giovanna Zanetti, 3 and Bice Fubini 3

1 Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden
2 Institute of Earth Sciences, Uppsala University, Uppsala, Sweden
3 Department of Inorganic Chemistry, Chemical Physics, and Chemistry of Materials, University of Torino, Torino, Italy

Abstract
Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated reactive oxygen species. The purpose of this study was to explore possible mechanisms for the reduction of fiber toxicity by iron chelator treatments. We studied changes in the amount and the oxidation states of bulk and surface iron in crocidolite and amosite asbestos that were treated with iron-chelating desferrioxamine, ferrozine, sodium ascorbate, and phosphate buffer solutions. The results have been compared with the ability of the fibers to produce free radicals and decompose hydrogen peroxide in a cell-free system in vitro. We found that chelators can affect the amount of iron at the surface of the asbestos fibers and its valence, and that they can modify the chemical reactivity of these surfaces. However, we found no obvious or direct correlations between fiber reactivity and the amount of iron removed, the amount of iron at the fiber surface, or the oxidation state of surface iron. Our results suggest that surface Fe 3+ ions may play a role in fiber-related carboxylate radical formation, and that desferrioxamine and phosphate groups detected at treated fiber surfaces may play a role in diminishing and enhancing, respectively, fiber redox activity. It is proposed that iron mobility in the silicate structure may play a larger role in the chemical reactivity of asbestos than previously assumed. -- Environ Health Perspect 105(Suppl 5):1021-1030 (1997)

Key words : asbestos fibers, iron chelators, iron mobilization, free radical release, hydrogen peroxide, electron paramagnetic resonance spectroscopy, surface analysis, X-ray photoelectron spectroscopy, Mössbauer spectroscopy

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 26 March 1997; accepted 29 May 1997.

The authors thank H. Riedl, Chalmers University of Technology, Sweden, for his assistance with the atomic absorption spectroscopy analysis. This research was carried out within the Swedish Biomaterials Consortium, which is financed by the Swedish National Board for Industrial and Technical Development and the Swedish Natural Science Council. Support was also received from Partek Insulation AB, Sweden and Finland.

Address correspondence to Dr. J. Gold, Department of Applied Physics, Fysikgränd 3, Chalmers University of Technology, S-412 96 Göteborg, Sweden. Telephone: 46 31 772 3369. Fax: 46 31 772 3134. E-mail: f7xjg@fy.chalmers.se

Abbreviations used: AAS, atomic absorption spectroscopy; at%, atomic percent; CO 2 - · , carboxylate radical; CS, centroid shifts; DMPO, 5,5'-dimethyl-1-pyrroline-N-oxide; EPR, electron paramagnetic resonance; HRTEM, high resolution transmission electron microscopy; ICP-AES, inductively coupled plasma-atomic emission spectroscopy; MS, Mössbauer spectroscopy; · OH, hydroxyl radical; QS, quadrupole splittings; UICC, Union Internationale Contre le Cancer; XPS, X-ray photoelectron spectroscopy.

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Last Update: October 17, 1997