A comparative study of the effects of inhaled cadmium chloride and cadmium oxide: pulmonary response

The effects of aerosols of cadmium chloride (CdCl2) and cadmium oxide (CdO) on pulmonary biochemical function were compared. Rats and rabbits were exposed to 0.25, 0.45, or 4.5 mg Cd/m3 for 2 h. Pulmonary toxicity was determined histologically and biochemically. Cadmium chloride and CdO showed a deposition response that was linearly related to the chamber concentration. Both compounds caused multifocal, interstitial pneumonitis 72 h after exposure, but the CdO lesion was more severe with proliferation of fibrocytic-like cells as well as pneumocytes. Comparing the two Cd compounds at the highest concentration (4.5 mg Cd/m3), the biochemical responses in the rat were similar. The majority of the effects occurred 72 h after exposure, with significant increases in lung weight, lung-to-body weight ratio, GSH reductase, GSH transferase, and G-6-PDH. However, GSH peroxidase was inhibited immediately after the CdO exposure. Cadmium oxide-related alterations in the parameters studied could easily be distinguished from those of CdCl2 at the exposure concentration of 0.45 mg Cd/m3. The response pattern in the rabbit resembled that of the rat. In both species Cd had a consistent inhibitory effect on pulmonary GSH peroxidase, even at the lowest concentration of 0.25 mg Cd/m3. Based on these findings, inhaled CdO appeared to be more toxic to the lung than inhaled CdCl2.