Aquatic genotoxicity testing with rat hepatocytes in primary culture. II. Induction of micronuclei and chromosomal aberrations

River water samples with varying degrees of contamination by municipal and industrial effluents were analyzed for their potential to induce sister chromatid exchanges, micronuclei and chromosomal aberrations in the primary rat hepatocyte assay. The direct comparison of these three parameters showed that SCEʹs are the most sensitive genotoxic endpoint induced by contaminated water samples, followed by micronuclei and chromosomal aberrations. The dose response curves are comparable, although shifted to higher concentrations for the latter two endpoints. No linear dose response was observed, indicating either concentration-dependent increases in toxicity, saturation of drug metabolizing enzymes, induced expression of detoxifying enzymes or the induction of repair functions. The analysis of the data also showed that contaminated surface water samples contain unstable or highly volatile compounds leading to a storage time-dependent decrease in the micronucleus frequency accompanied by an increasing mitotic index. Therefore, genotoxic potential should be determined as rapidly as possible after sampling. Additionally, since the samples vary according to their potential to induce specific genotoxic endpoints, all three parameters should be determined simultaneously to obtain a more reliable estimation of the genotoxic potential of the samples.