Comparative pulmonary responses caused by exposure to standard cobalt and ultrafine cobalt

The aim of this study was to compare the pulmonary toxicity after exposure to standard cobalt (Std-Co) and ultrafine cobalt (Uf-Co), Rats were intratracheally instilled with 1 mg of Std-Co and Uf-Co, and wet lung weight and bronchoalveolar lavage fluid (BALF) profiles were analysed 1, 3, 7, 15 and 30 d later, The effects of Std-Co and Uf-Co on indices that can be presumed to reflect epithelial injury and permeability (lactate dehydrogenase (LDH) and total protein (TP)), and release of proinflammatory cytokine (tumor necrosis factor-alpha (TNF-alpha)) were increased throughout the 30 d post-exposure period. The results showed that the effects of Std-Co and Uf-Co on these indices were significantly higher than those of control. The results also showed that the effects of Uf-Co on indices were significantly higher than those of Std-Co from 1 to 15 d after instillation. Moreover, the number of neutrophils and LDH activity in BALF in rats after exposure to Uf-Co were significantly greater than those of Std-Co-exposed rats up to 30 d after instillation. Our findings suggest that Uf-Co has a much more toxic effect on the lungs than Std-Co, but the mechanism remains to be elucidated.