Iron-induced hydroxyl radical generation from the surface of volcanic ash particles is a possible mechanism of respiratory toxicity in addition to crystalline-silica induced pathogenicity. Here we show that volcanic ash generates hydroxyl radicals, with greater reactivity in iron-rich, silica-poor samples, such as basaltic ash. Basaltic particles expose at the surface high levels of poorly-coordinated iron ions in both Fe(II) and Fe(III) oxidation states which are likely to be the cause of such reactivity. Hitherto, basaltic ash has been disregarded as a hazard due to the lack of crystalline silica particulate but future hazard assessment should consider its toxic potential.
Horwell, C., Fenoglio, I., & Fubini, B. (2007). Iron-induced hydroxyl radical generation from basaltic volcanic ash. Earth and Planetary Science Letters, 261(3-4), 662-669. https://doi.org/10.1016/j.epsl.2007.07.032