Figure 1.

Pathological features of lung tissue in rats after intratracheal instillation of nanoparticles. Magnification 100×. (A) 1mg-crystalline silica-exposed lung at one week; (B) 1mg-TiO₂ nanoparticle-exposed lung at one week; (C) 1mg-crystalline silica-exposed lung at six months; (D) 1mg-TiO₂ nanoparticle-exposed lung at six months. Pulmonary inflammation in TiO₂-exposed lung was more severe than that in crystalline silica-exposed lung at one week following intratracheal instillation. However, pulmonary inflammation in TiO₂-exposed lung disappeared at six months and the inflammation in crystalline-exposed lung severely increased.