Fig. 4

Hematoxylin and eosin staining of lung sections following inhalation exposure of polypropylene at each time course (A), and comparison of polarized light observation in the lung at 3 months after exposure in the high concentration group (B). Persistent mild inflammation, mainly neutrophils and alveolar macrophages, was observed until 1 month after exposure. Aggregation of inflammatory cells was observed at 3 months after exposure in the high-concentration group (Black arrow). (Scale bar: 100 µm)