Geochemistry in the lung: Reaction-path modeling and experimental examination of rock-forming minerals under physiologic conditions

Abstract

A novel and promising application of a geochemical tool adapted to medical science is the thermodynamic and kinetic modeling of the behavior of minerals in fluids similar to lung fluids (or simulated lung fluids, SLF). Reaction-path modeling for chrysotile, anorthite, K-feldspar, talc, muscovite, kaolinite, albite, and quartz under physiologic conditions in SLF gives dissolution times for these minerals as: chrysotile < anorthite < K-feldspar < talc < muscovite = kaolinite = albite = quartz. For the reaction of these minerals with SLF, hydroxylapatite (a mineral initially supersaturated in SLF) and several other secondary minerals were predicted to form (e.g., mesolite is predicted to precipitate during dissolution reactions of other Al 3+ -containing minerals). Batch experiments using SLF and a brucite/chrysotile mineral mixture confirm that hydroxylapatite forms during reactions in SLF, potentially a function of having a seed crystal in the brucite, chrysotile, or hydromagnesite (predicted to form from brucite dissolution) present. Moreover, SEM analysis of lung tissue also confirms the formation of calcium phosphates (e.g., hydroxylapatite). Reaction-path modeling of minerals under physiologic conditions provides insight into mineral behavior in the body; predicted mineralization pathways associated with pleural plaques and the predicted formation of Al3 + -bearing minerals during reaction-path modeling deserve attention when considering pathologies in the body.