Alumina nanoparticles size and crystalline phase impact on cytotoxic effect on alveolar epithelial cells after simple or HCl combined exposures

Applications using alumina nanoparticles (Al2O3 NPs) have incredibly increased in different fields of activity. In defense and aerospace fields, solid composite propellants use leads to complex combustion aerosols emissions containing high concentrations of Al2O3 NPs and hydrogen chloride gas (HCl). To better characterize potential hazard resulting from exposure to these aerosols, this study assesses cytotoxic effects of mixtures containing both compounds on human pulmonary alveolar epithelial cells (A549 cell line) after 24 h exposures. After all co-exposures cell viability was > 80%. However co-exposures decrease normalized real-time cell index. Significant decreases of intracellular reduced glutathione pool were also observed after co-exposures to gamma-10 nm or gamma/delta-13 nm Al2O3 NPs and HCl. Co-incubations with gamma/delta-13 nm or gamma-500 nm Al2O3 particles and HCl induced significant DNA double-strand breaks increases. Moreover all co-exposures and HCl alone disrupted cell cycle (increased G1 phase cells). Transmission Electron Microscopy (TEM) observations revealed gamma/delta-13 nm Al2O3 NPs adsorption and internalization in cell cytoplasm only, suggesting indirect genotoxic effects. According to our results Al2O3 particles/HCl mixtures can induce cytotoxic effects and Al2O3 size and crystallinity are two main parameters influencing cytotoxic mechanisms.