[Effects of chromium compounds on the respiratory system. Part 4. Long-term inhalation of chromic acid mist in electroplating to ICR female mice].

In order to determine the effect on the respiratory system of long-term inhalation of chromic acid in electroplating, histopathological examination was performed on mice (ICR, female, n = 50) exposed to chromic acid mist for 12 months (30 min/d, 2 d/wk), by using the authors' miniaturized chromium electroplating system. After 12 months' exposure, the mice were kept for 6 months without exposure. In the upper respiratory tract, round perforations were found in the nasal septum in 6 mice that were sacrificed or died after 10 months' exposure. The perforations were located near the point of the septum, the thinnest part of the nasal septum, and were of pin-hole sige. On the epithelium of the trachea and bronchus, loss of cilia, proliferation of goblet cells or basal cells, and squamous metaplasia were observed in almost all of the exposed mice. These changes appeared to be more advanced in mice exposed for a longer period. In the lung, development of benign adenoma was observed in one mouse in the 6- to 9-months' exposure group, in three in the 10- to 14-months' exposure group and in one in the group examined after 15 to 18 months. Furthermore, adenocarcinomas were found in two mice, one of which died at 17 months and the other was sacrificed 18 months after initiation of exposure. In conclusion, the finding that adenomas and adenocarcinomas were observed in mice exposed to chromic acid mist suggests the need to give careful attention to the possibility of respiratory cancers in chromium electroplating workers.