Whole-effluent toxicity approach

Whole mixture approach for unique mixtures. This is an option if dealing with a mixture of completely unknown or unique origin and composition. In this case, results of previous effect studies cannot be used to assess the effects of the mixture of concern. Determination of a safe concentration level or a dose-response relationship for these mixtures is inefficient, as the effect data cannot be reused to assess the risks of other mixtures. The mixture of concern has to be tested directly in the field or the laboratory, like in the whole effluent toxicity (WET) test, resulting in a direct indication of the potential effects. 

Johnson, I., Pickup, J.A. and van Wijk, D., A perspective on the environmental risk of halogenated by-products from uses of hypochlorite using a whole effluent toxicity based approach. Environ. Toxicol. Chem., 25, 1171, 2006. 

The biological approach (whole effluent) to toxics control for the protection of aquatic life involves the use of acute and chronic toxicity tests to measure the toxicity of wastewaters. Whole effluent tests (WET) employ the use of standardized, surrogate freshwater or marine (depending on the mixture of effluent and receiving water) plants (algae), invertebrates, and vertebrates. 

Species sensitivity approach If the suspected toxicant(s) has been correctly identified, effluent samples with different LC50, IC25 or IC50s for one species should have the same ratio for a second species with different sensitivity. When two or more species exhibit different sensitivities to the suspected toxicant during single chemical testing, and the same pattern is observed in the whole effluent, this provides supporting evidence that the chemical tested is the cause of effluent toxicity. 

The concept of ecological disturbance evaluations (EDEs) is another approach to address causation. EDE is conceptually comparable to TIE and BDF. As with TIE and BDF, which are used to identify chemicals responsible for toxicity in whole effluents and contaminated sediments, an EDE is applied after an impact has been detected in a community. The EDE uses an integrated index (e.g., index of biotic integrity), or other metric, allowing the researcher to extract information that might represent a response signature for the suspected cause of the impact. 

Case study Whole effluent assessment using a combined biodegradation and toxicity approach... 

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