On the relevance of genotoxicity for fish populations II: genotoxic effects in zebrafish (Danio rerio) exposed to 4-nitroquinoline-1-oxide in a complete life-cycle test.

In order to characterize the impact of genotoxic potentials on populations of aquatic organisms in surface waters, zebrafish (Danio rerio) were exposed to the model genotoxicant 4-nitroquinoline-1-oxide (NQO) in a complete life-cycle test. Fish exposed to mean NQO concentrations of 0, 0.1, 0.3, 1.1, and 2.9 microg/l were examined by several genotoxicity assays with different endpoints. Assays included the unscheduled DNA synthesis (UDS) test, the comet assay, the alkaline filter elution, and the micronucleus test. The genotoxicity assays revealed an increasing genotoxicity, ranging from induction of DNA repair (even at the lowest concentration tested) to primary and secondary DNA alterations at higher concentrations of 1.1 and 2.9 microg/l NQO. Whether the lowered reproductivity observed in the life-cycle test is caused by genotoxic pathways of NQO, remains unclear. However, the results indicate a contradiction to an earlier assumption that genotoxicants as found in the environment are likely to not impact natural populations. Copyright 2004 Elsevier B.V.