Representative transmission electron microscopy images of lungs 24 h after instillation of ZnONP at 15 cm2 to C57BL/6 mice. (A), vehicle control; (B - D), ZnONP treatment group. Bar scale: A = 10 μm; B = 5 μm; C and D = 2 μm. Eosinophils (arrow) were infiltrated in the alveolar interstitium. Macrophage (arrowhead) was severely vacuolated.