This International Standard specifies a method for the determination of the genotoxic potential of water and waste water using the bacterial strains Salmonella enterica subsp. enterica serotype Typhimurium TA 98 and

TA 100 in a fluctuation assay. This combination of strains is able to measure the genotoxicity of chemicals that induce point mutations (base pair substitutions and frameshift mutations) in genes coding for enzymes that are involved in the biosynthesis of the amino acid, histidine.