Impacts after inhalation of nano- and fine-sized titanium dioxide particles: morphological changes, translocation within the rat lung, and evaluation of particle deposition using the relative deposition index

A 3-week inhalation study with nano-and fine-sized titanium dioxide (TiO2) with 3, 28, and 90 days recovery time was performed in female Wistar rats. Lung volume measurements, histology, electron microscopy, hematology, and bronchoalveolar lavage (BAL) fluid analyses were conducted and the relative deposition index (RDI) was calculated. Minimal inflammatory changes in the lungs, leucopenia, and a decrease in beta-glucuronidase were observed. Particles were mainly deposited in alveolar macrophages and, to a lesser extent, in type-I pneumocytes, and this was quantified using the RDI. Rarely, particle-laden cells were observed inside capillaries. Therefore, minimal translocation of particles into the bloodstream has to be considered. Significant changes, e.g. in elicited effects or translocation behavior, between nano-and fine-particle-treated groups were not observed.