Pulmonary Toxicity of Ceria Nanoparticles in Mice After Intratracheal Instillation

Ceria nanoparticles (nano-ceria) are widely used for various applications such as catalytic converters for automobile exhaust, ultraviolet absorber, and electrolyte in fuel cells. Their potential impacts on the environment and human health have also drawn people's attention. The present study was designed to explore the pulmonary toxicity of nano-ceria in mice after an acute intratracheal instillation. CD-1 mice were exposed to 0.04, 0.4, 4 and 40 microg nano-ceria (corresponding to 10, 100, 1000 and 10000 times of the maximum exposure dose, respectively) and sacrificed at 1, 7, and 28 d post-exposure. Lung injury was assessed by bronchoalveolar ravage fluid (BALF) analysis, cell counts, biochemical analysis of lung homogenate, and histopathology. Cell differential analysis of the BALF show that the numbers of neutrophils and lymphocytes increased significantly in the mice exposed to 40 microg nano-ceria at 1 d after instillation, and returned to control levels by 7 d. The lactate dehydrogenate activity in the BALF from the 40 microg group increased significantly during the whole experimental period. Pathological changes were only found in the lung tissues from the mice of 40 microg nano-ceria group. The changes were most obvious by 7 d post-exposure, and returned to normal by 28 d. No other changes were found. The results of the present study suggest that exposure to nano-ceria at the current levels in the ambient air may not cause respiratory toxicity.