Inhalation Carcinogenicity and Chronic Toxicity of Indium-tin Oxide in Rats and Mice

Inhalation Carcinogenicity and Chronic Toxicity of Indium-tin Oxide in Rats and Mice: Kasuke Nagano, et al. Japan Bioassay Research Center, Japan Industrial Safety and Health Association—

Objectives

Carcinogenicity and chronic toxicity of indium-tin oxide (ITO) were examined by inhalation exposure of rats and mice to ITO aerosol.

Methods

Fifty mice of both sexes were exposed to ITO at 0 (control), 0.01, 0.03 or 0.1 mg/m³for 6 h/day, 5 day/wk for 104 wk, and 50 rats of both sexes were exposed to 0, 0.01 or 0.03 mg/m³ITO for the same time period. The repeated exposure of 50 rats of both sexes to 0.1 mg/m³ITO was discontinued at the 26th wk, followed by clean air exposure for the remaining 78 wk.

Results

In rats, incidences of bronchiolo-alveolar adenomas and carcinomas, bronchiolo-alveolar hyperplasia, alveolar wall ibrosis and thickened pleural wall, alveolar proteinosis and iniltrations of alveolar macrophages and inlammatory cells were significantly increased. Combined incidences of malignant lung tumors in male rats and total lung tumors in male and female rats were significantly increased at exposure to 0.01 mg/m³ITO. In mice, no carcinogenic response occurred, but thickened pleural wall, alveolar proteinosis and alveolar macrophage iniltration were induced. Mice were less susceptible to ITO than rats. The lung content of indium was the greatest, followed by the spleen, kidney and liver. Blood indium levels increased dose dependently.

Conclusions

There was clear evidence of carcinogenicity of inhaled ITO in male and female rats but not clear evidence in mice, together with occurrence of the chronic pulmonary lesions in both rats and mice.