Histopathological changes in the lungs of rats instilled with Korean chrysotile.

To evaluate the pulmonary toxicity of Korean chrysotile (KC), 1 or 2 mg of KC (low- and high-concentration groups, respectively) was instilled in the lungs of Sprague-Dawley rats by a single intratracheal instillation. The lungs were examined using a light microscope at several time points (5 days, 5 weeks, and 10 weeks). Up to 10 weeks after KC instillation, differences were observed in the pathological reactions and ultimately in lung recovery between the two groups. At 5 days after KC instillation, lung weight increased and severe bronchiolitis obliterans developed in proportion to the KC concentration administered. From 5 to 10 weeks after KC administration, the lung weight of the low-concentration group increased and bronchiolitis obliterans worsened. In the high-concentration group, the lung weight and the severity of bronchiolitis obliterans at 10 weeks after administration of KC declined compared to those at 5 weeks. In conclusion, the effects of KC on lung tissue were initially found to be more influenced by the amount of fiber, but over time, the effects were influenced by the residual fibrous material in the lung tissue and its biodurability.