GEOCHEMISTRY IN THE LUNG: REACTION-PATH MODELING AND EXPERIMENTAL EXAMINATION OF ROCK-FORMING MINERALS UNDER PHYSIOLOGIC CONDITIONS

Asbestosis and mesothelioma are associated with fibrous mineral accumulation in lungs, where these minerals can interact with lung fluids and macrophage in ways that can dissolve and reprecipitate minerals at different rates. Thermodynamic and kinetic geochemical reaction-path modeling can be used to investigate the longevity of minerals in lungs, the reaction products as a result of mineral-fluid interactions in lungs, and the mechanisms of specific reactivity that may have direct bearing on cellular physiological responses. Reaction-path modeling for chrysotile, anorthite, K-feldspar, talc, muscovite, kaolinite, albite, and quartz under physiologic conditions in a lung-fluid simulant gives dissolution times for these minerals as: chrysotile < anorthite < K-feldspar < talc < muscovite = kaolinite = albite = quartz. For the reaction of these minerals with the lung-fluid simulant, hydroxylapatite (a mineral initially supersaturated in these lung fluids) and several other secondary minerals were predicted to form (e.g., mesolite is predicted to precipitate during dissolution reactions of other Al³⁺-containing minerals). Batch experiments using lung-fluid simulant and a brucite/chrysotile mineral mixture confirm that hydroxylapatite forms during reactions in simulated lung fluid, 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 (like hydroxylapatite). More comprehensive modeling could be done if thermodynamic and kinetic data for organic ligands and additional minerals were available, and if we knew more about the detailed aqueous composition of lung fluid and the flushing rates of that fluid across minerals lodged in lung tissue. Reaction-path modeling of minerals under physiologic conditions provides insight into mineral behavior in the body; predicted mineralization pathways associated with environmental cancers, pleural plaques, and the predicted formation of Al³⁺-bearing minerals during reaction-path modeling deserve attention when considering pathologies in the body.