Strategies to reduce the cost of mutagenicity screening with the Salmonella assay.

An extensive Salmonella assay database was analyzed in order to develop strategies to reduce costs of screening chemicals for mutagenicity. This database was obtained from testing 941 samples (representing 799 chemicals), 36% of which were judged mutagenic. Strains TA98, TA100, TA1535, and TA1537 without activation, with rat liver S-9, and with hamster liver S-9, make up the 12 strain/activation combinations considered here. The testing strategies examined consist of two or three stages; a positive result at any stage is regarded as definitive and stops the testing. Sequential testing improves efficiency by eliminating the need for further experimentation once a chemical has been found to be mutagenic. Consequently, costs and effort are reduced. For screening chemicals in the Salmonella assay, it is our recommendation that a sequential testing scheme be adopted whose initial stage consists of TA100.