Despite the increase in the numbers of synthetic fibers, their pulmonary toxicity has yet to be exclusively studied. This study was designed to investigate the acute effects of TiO2 whisker, especially there related to its shape. Male rats received single intratracheal instillation of one of the following materials at doses from 0 to 2.0 mg in 0.5 ml saline (four rats/dose): (TO1) TiO2 whisker (JFM standard sample FTL-300), (TOP) nonfibrous particle TiO2, and (Ams) amosite as positive control. BAL fluid collected at days 1, 3 and 7, were subjected to cell differential (CD), measurements of LDH, and total protein (TP). The results indicated that:
1. TO1 and Ams caused significant dose-dependent increases in the numbers of neutrophils, eosinophils, lymphocytes, and monocytes, with the peak at day 1, whereas TOP caused an increase only in the number of neutrophils.
2. Following the peak, the number of eosinophils in TO1 decreased at a significantly slower rate than that in Ams.
3. Levels of both LDH and TP displayed similar patterns to those of CD in both TO1 and Ams, but no change in TOP. It was concluded that the above TO1-induced responses were neither due to its chemical composition nor its surface crystal structure (rutile), but rather due to its fibrous shape.