Oral toxicity of indium in rats: single and 28-day repeated administration studies.

Indium is widely used in the electronics industry to make semiconductors, liquid-crystal panels, and plasma display panels, and its production is increasing. However, it is necessary to handle it more cautiously than before, because the pulmonary toxicity of inhaled indium has been identified. The present study aimed to characterize the potential toxic effects of indium through oral administration and observation for fourteen days following a single dose of 0 or 2,000 mg/kg (acute oral toxicity study), and repeated oral administration for 28 days at dose levels of 0, 40, 200, or 1,000 mg/kg daily (28-day repeated oral dose toxicity study) to male and female Crj:CD (SD) IGS rats (SPF). No deaths and no abnormalities in clinical signs, body weights, and necropsy findings were observed for any of the animals in the acute oral toxicity study. Furthermore, no changes related to indium were also observed in the dose groups up to 1,000 mg/kg of the 28-day repeated oral dose toxicity study. From the results described above, the lethal dose 50% (LD(50)) of indium is greater than 2,000 mg/kg under these study conditions, and the no-observed-adverse-effect-level (NOAEL) is considered to be 1,000 mg/kg for males and females under these conditions.