Cytogenetic changes in fish exposed to water of the river Rhine.

The induction of chromosome aberrations in fishes, exposed to Rhinewater, was investigated. The mudminnow, Umbra pygmaea, was chosen for this study, because of its ideal karyotype of 22 large chromosomes. Gill cells were used for chromosome studies. Fish, kept in Rhinewater for 11 days had chromosome breaks in approximately 30% of the metaphases studied. Control fish, exposed to a very good quality of untreated groundwater had breaks in about 8% of the metaphases. Several Rhinewater extracts were tested for their mutagenic potential in the Salmonella-microsome test. The fraction of aromatic compounds was found to be positive. This may indicate that one or more of the compounds present in this fraction were also responsible for the cytogenetic changes found in the fish.