CHEMICAL CHARACTERIZATION AND REACTIVITY OF IRON CHELATOR-TREATED AMPHIBOLE ASBESTOS

Iron in amphibole asbestos is implicated in the pathogenicity of inhal ed fibers. Evidence includes the observation that iron chelators can s uppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated reactive oxygen species, Th e purpose of this study was to explore possible mechanisms for the red uction of fiber toxicity by iron chelator treatments. We studied chang es 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 so lutions. The results have been compared with the ability of the fibers to produce free radicals and decompose hydrogen peroxide in a cell-fr ee system in vitro. We found that chelators can affect th amount of ir on at the surface of the asbestos fibers and its valence, and that the y can modify the chemical reactivity of these surfaces. However, we fo und no obvious or direct correlations between fiber reactivity and the amount of iron removed, the amount of iron at the fiber surface, or t he oxidation state of surface iron. Our results suggest that surface F e3+ ions may play a role in fiber-related carboxylate radical formatio n, and that desferrioxamine and phosphate groups detected at treated f iber surfaces may play a role in diminishing and enhancing, respective ly, fiber redox activity, It is proposed that iron mobility in the sil icate structure may play a larger role in the chemical reactivity of a sbestos than previously assumed.