Dye-sensitized nanocryst. TiO2 solar cells are currently under development. Since these cells contain an electrolyte soln. we reviewed the health and safety aspects in view of indoor applications, where personal contact cannot be excluded. Only small amts. of chems. are present in each cell and so there is no danger of acute toxicity. However, long-term effects often can be caused by incidental contact with minute amts. For this reason we have tested cis-di(thiocyanato)-bis(4,4'-dicarboxy-2,2'-bipyridine)Ru(II), the sensitizer dye in the Ames test. The dye was not mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia coli reverse mutation assay.