Inhalation Toxicity of Ultrafine Zinc Oxide Particles n Spontaneously Hypertensive Rats

Zinc oxide (ZnO) nanoparticles have been widely used commercially for rubber, paint, and cosmetics. With the advent of nanotechnology, the potential health effects of novel technology have raised concerns. The toxicity of ZnO nanoparticles has been studied using intratracheal instillation. However, the exact particle size was not clear. Thus, inhalation exposure was proposed to overcome this problem.n our previous inhalation studies, ZnO nanoparticles were produced by a furnace tube airflow system, but there are still some deficiencies. The system took long time to become stable, and the exposure and control groups could not be exposed at the same time. In this study, we improved the ZnO nanoparticle generator and animal exposure system, then we used this device to test the toxicity of ZnO. or particle generation and exposure system, we designed a smaller mixing chamber between the generator and exposure chamber, and this reduced the time for nanoparticles to become stable. In exposure chamber, particle number concentration reached 106 #/cm3, and geometric mean diameter was about 12-15 nm. pontaneously hypertensive rats (SHR) were exposed by this system to assess lung toxicity. SHR were exposed to ZnO nanoparticle in whole body exposure chamber for 1 day (1X, n=6), or for 3 successive days (3X, n=6) for 6 h/day. SHR (n=6) were also exposed to clean filtered air as controls. We collected the tail-blood to analyze the cytokines at 3 h postexposure to ZnO, and sacrificed the animals to obtain the whole blood and perform bronchoalveolar lavage at 24 h postexposure. The whole blood were tested for CBC/DC and cytokines TNF-α and IL-6. The lavage supernatants were analyzed for total protein and lactate dehydrogenase activity for lung injury while total cells and neutrophils were determined for lung inflammation.he percentage of neutrophils in exposure groups increased significantly as compared to the controls after 1 day of exposure (p<0.05), while there was no difference after 3 days of exposure. Cytokine IL-6 in peripheral blood expression was similar to neutrophils (p<0.05). But the systemic inflammation and TNF-α were not different from controls after 1 day or 3 days exposure. ur study has demonstrated that ZnO nanoparticles may cause lung inflammation after 1 day of exposure, but not after 3 days of exposure. This suggests lung inflammation tolerance may develop after repeated exposure to ZnO.