COMPARATIVE-EVALUATION OF 4 BACTERIAL ASSAYS FOR THE DETECTION OF GENOTOXIC EFFECTS IN THE DISSOLVED WATER PHASES OF AQUEOUS MATRICES

The aim of this study was to evaluate the perfomance of four bacterial short-term genotoxicity assays (Salmonella/microsome assay, SOS Chrom otest, Microscreen phage-induction assay, differential DNA repair test ) that are widely used and/or have a promising potential for the genot oxicity testing of water samples. Twenty-three samples of different or igins (drinking and bathing water, surface water, municipal and indust rial wastewater, pulp mill effluents, groundwater, and landfill leacha tes) were tested in these assays. In total, 20 samples were genotoxic: 13 in the Salmonella/microsome assay, 13 in the SOS Chromotest, 8 in the Microscreen phage-induction assay, and 19 in the differential DNA repair test. Although the differential DNA repair test was the most se nsitive system, positive results were obtained also with some of the n egative control samples, and it had the least power to detect differen t genotoxic potencies. The Microscreen assay was the least sensitive s ystem due to nonlinear results and sample toxicity. The Salmonella/mic rosome assay and the SOS Chromotest were of equal sensitivity, but the variance of the results was higher in the Salmonella/microsome assay. As the Salmonella/microsome assay also lacks toxicity correction for routine applications and ordinarily utilizes two strains, the SOS Chro motest appears to be the most promising test system for routine screen ing of water samples. Based on the present experiments, the investigat ed water samples were ranked according to their genotoxic potency as f ollows: landfill leachates > effluents from pulp production > wastewat er > surface water > contaminated groundwater approximate to drinking and bathing water > control samples. The rankings obtained with the in dividual test systems were generally in good agreement. In addition, w e present data on the impact of water treatment methods (activated slu dge treatment, UV disinfection) and of alternative technologies (ozone vs ClO2 pulp bleaching) on the genotoxicity of water samples.