The carcinogenicity of indium and its compounds is of concern, and so the Ministry of Health, Labour and Welfare specified these as chemicals which may be carcinogenic to humans by ministerial ordinance. Many carcinogens act on DNA and cause mutation, leading to cancerization. Accordingly, mutagenicity is closely involved in carcinogenicity. We extracted each component from alloy powders of prototype indium-containing silver alloy, alloy for porcelain bonding, and gold-silver-palladium alloy, and investigated their mutagenicity using the umu-test, which is a mutagenicity screening method. This test method utilizes expression of the SOS genes which repair injured DNA in bacteria, and the mutagenicity of many chemicals can be detected, similarly to the Ames test. A positive reaction was detected in the prototype Ag-indium alloy, but the alloy for porcelain bonding and gold-silver-palladium alloy were negative. It was clarified that close investigation of metal indium and commercial indium alloys is necessary.
