Deposition and pulmonary effect of nanoparticle in whole body inhalation study and in nose only inhalation study

For assessing the pulmonary effect of inhaled particles, inhalation study has been frequently performed. Recently nose only inhalation study become widely used because of the possibility of high exposure concentration and less waste. But it is not certain whether the nose only inhalation study and whole body inhalation study result the same pulmonary effects at the same experimental conditions. In this study, therefore, we performed inhalation studies of the two systems and compared the results. 15 Fischer 344 male rats (12 weeks old) were divided into 3 groups. 5 rats are for whole body inhalation and 5 for nose only inhalation group. These 10 rats were exposed to TiO₂ for 6 hours. The rest 5 rats were exposed to fresh air. The average exposure concentration were 4.10±1.07 mg/m³ in the whole body chamber and 4.01±1.11 mg/m³ in the nose only chamber. The geometric mean diameters were 230nm and 180 nm, respectively. After 6 hours inhalation, TiO₂ amounts in lungs measured by ICP-AES were 42.6±3.5 mg in whole body inhalation group and 46.0±7.7 mg in nose only inhalation group. No statistical difference is existed between 2 groups. Histopathological results showed no significant PMN influx and fibrosis in both groups. Our results suggested that both inhalation studies result the similar deposition amount and histopathology at almost the same exposure concentration. This work is on the research program of “Development of innovative methodology for safety assessment of industrial nanomaterials" supported by Ministry of Economy, Trade and Industry (METI) of Japan.