Scientists at the University of Iowa exposed mice to 5 nm sized particles of titanium dioxide in order to learn about the potential health impact of manufactured nanomaterials.  One group of test animals inhaled the aerosolized particles for four hours in a single day, and another group inhaled them for four hours a day for ten days.  The results of the tests were encouraging.  The first group of mice experienced no adverse effects.  The second group “showed a significant but modest inflammatory response” that resolved itself between two and three weeks after the last exposure. The study is important because some scientists theorize titanium dioxide nanoparticles exhibit novel characteristics at sizes at or below 10 nm.  Because the particles in this study fell below that size-range, the scientists were prepared for unique results – which did not occur.

The study is also noteworthy because the scientists went to great lengths to specifically characterize the nanoparticles, aerosol, exposure methods, and animals used in the experiment in great detail. It is also notable that the study used the smallest commercially available titanium nanospheres, providing a nice benchmark for future researchers.

V. Grassian, “Inhalation Exposure Study of Titanium Dioxide Nanoparticles with a Primary Particle Size of 2 to 5 nm,” Environmental Health Perspectives, Vol. 115, No. 3 (March 2007).