Lung clearance of65Zn post-IT instillation of65ZnO and SiO
-coated65ZnO NPs. The percentages of instilled 65Zn measured in the whole lungs are shown over a period of 28 days. The clearance of 65Zn was rapid with only 16-18% of dose remaining at 2 days. By day 7, only 1.1% (SiO2-coated 65ZnO NPs) and 1.9% (65ZnO NPs) were measured in the lungs. And by the end of experiment, 65Zn was nearly gone (less than 0.3% of dose). Although statistically higher levels of 65ZnO NPs than of SiO2-coated 65ZnO NPs remained in the lungs at 7 and 28 days, the graphs show nearly identical clearance kinetics. (n = 8 rats at 5 minutes, 2 days, and 7 days, n = 5 at 28 days).