Flow-through dissolution of mineral fibres under lysosomal conditions

Mineral fibre toxicity is widely considered to depend on their residence time in the lungs, and therefore on their biodurability. However, fibre dissolution is typically examined in closed batch systems, which evolve toward saturation and do not reproduce the continuous renewal of lung fluids. In this study, for the first time the dissolution behaviour of fibrous antigorite, chrysotile, and crocidolite was investigated in a flow-through system to better constrain their expected persistence in vivo. Flow-through experiments were conducted in simplified artificial lysosomal fluid (sALF) at pH 4.5 and 37 °C, with a flow rate of 0.047 mL min-1. The concentrations of dissolved elements were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), while the incubated samples were analysed by powder X-ray diffraction (PXRD). Released Si was used to derive steady-state dissolution rates normalised to specific surface area. Fibrous antigorite and chrysotile show comparable Si-release rates of 1.03±0.02∙10-10 mol m-2 s-1 and 1.09±0.11∙10-10 mol m-2 s-1, one order of magnitude higher than that of crocidolite (1.22±0.06∙10-11 mol m-2 s-1). When differences in specific surface area are considered, the biodurability of fibrous antigorite is only slightly lower than that of crocidolite, and therefore, both fibres are expected to persist significantly longer in vivo compared to chrysotile.