Levels of chromosomal damage in hepatocytes of wild rats living within the area of a waste disposal plant

Genetic damage induced by ionizing radiation or chemical mutagens/carcinogens has been shown to persist over periods of months in rat hepatocytes, implying that continual exposure to low levels of mutagens will cause an accumulation of damage. Thus, it was assumed that hepatocytes of wild rats could be useful as ‘biological indicators’ for the exposure to mutagens/carcinogens in the environment. To test for this hypothesis house rats (Rattus rattus) were trapped at a waste disposal site and the levels of micronuclei and chromosomal aberrations determined. The results indicate that the frequency of chromosomal aberrations increases with the weight (age) of the animals, while micronuclei did not significantly differ from the level found in laboratory rats. For comparison Norway rats (Rattus norvegicus) trapped at the same site were analyzed for the same cytogenetic endpoints. We note a less pronounced weight dependent increase of chromosomal aberrations, most probably reflecting the different residence time at the waste disposal plant, an age dependent decrease of chromosomal aberrations of the F1-generation housed in the animal facility, indicating that the offspring had been exposed transplacentally and an age independent level of chromosomal aberrations in the F2-generation not significantly different from that of the Fischer 344 laboratory rat.