The role of mutagenicity testing in the ecotoxicological evaluation of industrial discharges into the aquatic environment.

An important task of ecotoxicology is to provide data for use by governments as a scientific basis for regulating the discharge of potentially hazardous substances into the environment. The criteria on which such regulations are based include biological and chemical degradability, bioavailability (accumulation) and toxicity, the latter manifesting itself in a reduced ability of organisms to survive and reproduce. There are also arguments for including the mutagenicity of chemicals in these criteria. In the past decade many studies have revealed the contamination of water and the atmosphere by mutagens originating in human activities and having observable effects on organisms in these environments. The extent to which this mutagenic stress can alter ecosystems as a whole is not yet known, but if mutagens are shown to cause major changes, mutagenicity is clearly an important ecotoxicological criterion. In the meantime its use must be based on the actual damage caused to organisms by mutagens and on the rising concern over a novel ecological phenomenon that might be named 'increased mutagenic stress'. A detailed report on the ecotoxicological case history of the discharge from a nitrofuran factory demonstrates the role of mutagenicity tests in the evaluation of effluents. As well as being toxic to algae, the discharge was found to be mutagenic in the Ames test. Toxicity and mutagenicity were used as criteria in studies of the biodegradability of the offending substances in a chemostat, as well as in studies to monitor the success of detoxification attempts. In the chemostat the mutagens did not appear to be very degradable but the algal toxicity decreased by 90%. Detoxification was reasonably successful for the mutagens in contrast to the algal toxicants.