A comparison of the predictive values of the Salmonella/microsome mutation and BHK21 cell transformation assays in relation to dyestuffs and similar materials

A group of 22 dye-related compounds were selected for testing in two short-term predictive tests for carcinogenicity. The group of compounds was made up of nine established animal carcinogens and 13 chemicals for which there was substantial evidence of non-carcinogenicity. The materials were coded and used to assess the predictive value of the Salmonella/microsome reverse mutation assay and the BHK21 cell transformation test. The overall predictive value with these compounds obtained for the Salmonella microsome reverse mutation assay was 86% and it is concluded that because of the good predictive value and the relative ease of experimental procedure, the Salmonella mutation assay is a useful first step in any proposed series of toxicological bioassays for the identification of genotoxic agents in the dyestuffs industry.The cell transformation test on the other hand was difficult to conduct and interpret. The interpretation of the coded data as judged by the IRI scientists was that of the 22 'unknown' compounds, eight results were judged to be correct, six were wrong and seven were doubtful. However, when the same data were re-evaluated uncoded by ICI staff, 15 results were judged to be correct and six were wrong. These results serve to exemplify the difficulties encountered with cell transformation assays and it is concluded that the system should not be used as a routine test for dyestuffs and related compounds.