Advanced Ceramics Report (ACR) recently ran an article about a Swiss-based nanotoxicity experiment using cerium oxide nanoparticles. According to the article, the researchers selected cerium oxide for the test because it is heavily used in the semiconductor industry as an abrasive to etch computer chips. The scientists simulated aerosol exposure of lung epithelial cells by spraying the particles on cells for 10, 20, and 30 minute intervals. "The longer the cultures were sprayed . . .  the more nanoparticles were deposited on the lung cells. The scientists observed that the cells did not die. However, the permeability of the cell layer increased." Additionally, the cells apparently produced a precursor indication of potential oxidative stress.

ACR, June 1, 2009, "Cerium oxide nanoparticles toxicity on lungs examined."