Utilization of Pulmonary Bridging Studies: Lung Toxicity Studies with Triethoxyoctylsilane-coated TiO2 Particles.

The aims of this study were to assess in rats, using a well-developed, short-term pulmonary bioassay, the acute pulmonary toxicity of intratracheally instilled triethoxyoctylsilane (OTES)-coated (i.e. hydrophobic) pigment-grade TiO₂ particles relative to uncoated, hydrophilic TiO₂ particle control samples and to bridge the results of these instillation studies with data previously generated from inhalation studies with uncoated, pigment-grade TiO₂ particles, using these uncoated pigment-grade TiO₂ particles as the inhalation/instillation bridge material. Rats were intratracheally instilled with 2 or 10 mg/kg of the following TiO₂ particle types: TiO₂ with OTES, TiO₂ with Tween 80, or TiO₂ with OTES and Tween 80. Saline-instilled rats served as controls. The lungs of sham and exposed rats were evaluated by bronchoalveolar lavage and histopathology at 24 h, 1 week, 1 month and 3 months post-exposure. The results demonstrated that only the high dose (10 mg/kg) pigment-grade TiO₂ particles and those with Tween 80 produced a transient pulmonary inflammatory response, and this reached control levels within 1 month post-exposure. We conclude that the OTES coating on the pigment-grade TiO₂ particle does not cause significant pulmonary toxicity. [ABSTRACT FROM AUTHOR]