Chemical carcinogens in the environment: risk assessment for the environment

The high priority of chemical carcinogens in environmental monitoring programmes is primarily due to a fear of a human exposure to these chemicals. Diseases like cancer are, however, also observed in indigenous populations of e.g. fish and shellfish, although these effects in general are rare events in the environment. High levels of carcinogens seem to be required for an influence on the prevalence of cancer, and an influence has almost exclusively been detected on the prevalence of liver tumours in populations of bottom-dwelling fish. The most important ecological aspect of chemical carcinogens in the environment may be the genotoxic potential of the carcinogens. Induced mutations may result in effects on survival or growth of the exposed organisms. In germ cells induced mutations are transmitted to future generations, resulting in an anthropogenic increase in the background mutation rate. The structure and function of the ecosystem is in the long run somehow determined by the background mutation rate which raises the question whether an increase in the mutation rate is advantageous or disadvantageous from a population and evolutionary point of view. To date experimental knowledge is hardly available even on the type of changes to be expected.