Fig. 8

Representative microscopic photographs of female rat lungs after inhalation exposure to TiO₂ NP (50 mg/m³). Representative loupe photograph (A) and magnified images of the area surrounding a lesion (B) and TiO₂ NP-induced multifocal lesions (C, D) are shown. Formalin was injected into the right lung through the bronchus and the tissue was stained with hematoxylin and eosin (HE). TiO₂ NPs phagocytosed by macrophages were observed throughout the alveolar region and were black in HE staining or birefringent using polarized light microscopy. A typical macrophage phagocytosing particles until the nucleus was not visible is shown on right side of panel B. Representative histological images of multifocal lesions in the area just below the pleura C and around the Bronchiolo-alveolar duct junction D are shown. Histopathologically, in each lesion particle-laden macrophage agglomeration was observed, and in many foci, alveolar epithelial proliferation and inflammatory cell infiltration was also observed (magnified right side of panels C and D).