Application of bioassays for ecological assessments

3 Application of bioassays for ecological assessments The evaluation of threats posed to ecological receptors or functions is probably the most significant reason for the application of biological test methods. There exist different approaches for using bioassays to perform risk assessments and to draw conclusions for risk management decisions. 

The extrapolation of test data includes uncertainty, in particular, if measurement and assessment endpoints are not identical. However, this source of variation is even more pronounced when using chemical concentrations for the prediction of field effects. It has to be emphasised that the use of bioassays represents one line of evidence, which together with chemical analysis and/or biological field data should be used for a reliable ecological risk assessment. 

Calculating effect levels for polluted soils rather than for chemical concentrations is another option and would generate results such as the LC50 for earthworms in the tested contaminated soil/reference soil mixture amounts to 30% of the contaminated soil and 70% reference soil. However, this approach also requires dilution with a reference soil and it may be questioned for its practical relevance. Effect levels may be useful for the evaluation of mobile media such as effluents that are subject to dilution in the environment. However, 

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