Dissolution and surface chemical modifications of mineral fibres in artificial lysosomal fluid

The long-term toxicity of mineral fibres is closely related to their biodurability and surface reactivity, which are in turn strongly influenced by mineral dissolution and surface alteration in lung fluids. We investigated dissolution rates and nanoscale structural, morphological and surface chemical modifications of fibrous antigorite, a non-regulated serpentine polymorph of uncertain pathogenicity, amphibole asbestos (crocidolite and tremolite) and chrysotile, after incubation in artificial lysosomal fluid at pH 4.5, simulating the acidic environment of alveolar macrophages. Fibres were incubated at 37 °C for up to 4 weeks; elemental release was quantified by ICP-OES, and recovered fibres were characterized by PXRD, XPS, FE-SEM, AFM, and TEM. All fibres dissolved incongruently, with preferential leaching of octahedrally coordinated cations and Fe mobilization promoted by citrate complexation. Chrysotile dissolved extensively and became progressively amorphous, consistent with its high specific surface area and preferential removal of Mg from outer octahedral layers. When Si-based dissolution rates are normalised to specific surface area, fibrous antigorite displays biodurability comparable to chrysotile and at least one order of magnitude lower than amphibole asbestos. Among amphiboles, tremolite dissolves more slowly than crocidolite, for which surface erosion exposes underlying Fe(II)-rich layers. Despite the simplified, acellular nature of the ALF model, our results show trends in incongruent dissolution, Fe mobilisation and surface amorphization consistent with in vivo toxicological observations. Integration of ALF-based mineralogical and geochemical data with targeted cellular and in vivo studies may provide a more robust mechanistic framework for understanding the long-term toxicity of both asbestos and currently unregulated fibrous minerals.