Ecotoxicological thresholds

Chemical analyses are an indispensable complement to ecotoxicological investigations, but they are not directly integrated in the application of the pT-scale for industrial effluent assessment. Performed in parallel, assessment of chemical substances is governed by a set of criteria, which are derived from ecotoxicological threshold (NOEC) values, in order to derive quality objectives or standards. When bioassay and chemistry results are both available for effluent assessment, they should be ranked equally. For determining the overall hazard of wastewaters, the most conservative information with respect to aquatic health will serve as the yardstick to ensure environmental protection. 

Aquatic toxicologists are still struggling to develop proper test methods to determine ecotoxicological threshold concentrations. The harmfulness of a sub-... 

Apart from the use of this approach to study the ecotoxicology of neurotoxic pollutants in the field, it also has potential for use during the course of environmental risk assessment. An understanding of the relationship between biomarker responses to neurotoxic compounds and effects at the population level can be gained from both field studies and the use of mesocosms and other model systems. From these it may be possible to define critical thresholds in biomarker responses of indicator species above which population effects begin to appear. In the longer term, this approach... 

Van Wijngaarden RPA, Brock TCM, Van den Brink PJ (2005) Threshold levels of insecticides in freshwater ecosystems a review. Ecotoxicology 14 353-378... 

The studies of SeKT have the objective of testing the applicability of sediment contact tests with a possibly wide range of different sediments. This means primarily determining the variabihty of the test results with the aim of improving the reliability of the tests. The project plan comprises i) the application of the sediment contact tests with different sediments in order to identify the influences of natural sediment properties on the test systems ii) the definition of reference conditions, including the standardisation of negative controls iii) the determination of toxicity thresholds for the individual sediment contact tests. Further, iv) the test systems should be validated with contaminated natural sediments and by means of dose-effect relations with sediment samples that were spiked with selected contaminants. The results obtained within the project should serve as a data base for improved interpretation and evaluation of ecotoxicological sediment analyses. 

A single component, such as contaminated sediments, may have an episodic release of toxics that could push an entire system beyond its resihency. Ecotoxicological tests in microcosms and/or mesocosms can reduce uncertainty about this threshold. 

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