This research project focuses on the role of physical-chemical characteristics of nanoparticles in their interactions with cells, organelles, and organs after in vivo exposure via the inhalation route. During the first year, we will assess the biokinetics and toxicity of 3 selected nanoparticles under three different physical-chemical states. An important goal of our research will be the evaluation of acute vs. chronic toxicity of inhaled nanoparticles. We propose to compare the acute and chronic toxicity in test animals exposed by inhalation to cerium, nickel, and silver nanoparticles. Each of these commercially-important nanomaterials (and other Consortium-selected nanomaterials) will be dynamically generated for these inhalation studies. The nose-only exposure system has been constructed and the nanoparticle generation system is almost complete (as of 2/11). Tasks completed include: 1. testing of furnace system to fully oxidize aged nanoparticles 2. construction ofthe aging system in the animal housing facility 3. ordering of test material for nanoparticle generation 4. recruitment of an exposure assessment student to participate in the research for his Master's thesis