Genotoxicity of sludges, wastewater and effluents from three different industries.

Many surface waters in Europe, Asia and South America have been reported to be contaminated with genotoxic substances. Therefore, it is important to establish strategies for identification of the most critical sources. In this study, we used a battery of four genotoxicity assays namely chromosomal aberration, DNA strand break, DNA laddering and P53 accumulation tests in mononuclear blood cells. Before cleaning of wastewater high levels of genotoxic contamination could be observed. For instance, we observed an increase in chromosomal aberrations from 2.6 +/- 1.1 (aberrant cells in %; control), to 33.6 +/- 6.6 in a petrochemical plant, 29.4 +/- 3.3 in a petroleum refinery and 14.4 +/- 1.8 in a coke plant of steel industry. A good correlation between the four assays was found. The most sensitive and reproducible results were obtained with the chromosomal aberration assay. Interestingly, clear differences in the efficiency of wastewater cleaning in three different treatment plants were observed. The first and second treatment plants in petrochemical industry and coke plant of steel industry completely eliminated genotoxicity of the wastewater. However, the third plant in petroleum refinery could achieve a reduction in genotoxicity but significant genotoxic contaminations were still present. In conclusion, our battery of genotoxicity tests allows the identification of critical sources contributing to contamination of surface waters.