A recent paper published in Inhalation Toxicology suggests that reliance on ultrafine particle inhalation animal studies for nanoparticle health and safety purposes may be appropriate due to the lack of existing studies on nanoengineered particles.  The article referenced several existing health and safety studies concerning nanoparticles, and noted their sometimes differing and conflicting conclusions.  Specifically, the authors studied rat exposure to three types of ultrafine particle exposure in lab rats, and then applied a quantitative risk assessment model for "estimating human-equivalent exposure using rat does-response data."  The paper concluded by stating more research and study are necessary to determine whether this methodology can be successfully modified to apply to nanoparticle exposure.

Kuempel, E. D., et al., “Lung Dosimetry and Risk Assessment of Nanoparticles: Evaluating and Extending Current Models in Rats and Humans,” Inhalation Toxicology, 18:717-724 (2006)