Whole Effluent Toxicity WET

The United States is the leader as regards the integrated assessment of the quality of effluents introduced into aquatic environments. In 1984, the United States Environmental Protection Agency (US EPA) introduced the notion of Whole Effluent Toxicity (WET). WET assays may involve the following samples 79... 

Apart from the 1-sample case, natural pollution gradients, for example, in a stream below a point pollution source or in whole effluent toxicity (WET) testing,... 

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. 

USEPA] US Environmental Protection Agency. 2004. National whole effluent toxicity (WET) implementation guidance under the NPDES program [Draft]. EPA 832-B-04-003. Washington (DC) US Environmental Protection Agency. Office of Wastewater Management. 

To ensure that waters are free from toxics in toxic amounts and to help control discharges of a complex nature, whole effluent toxicity (WET) testing was added to the US NPDES under the CWA (Heber et al 1996). 

US Environmental Protection Agency (1994) Whole effluent toxicity (WET) control policy (EPA 833-B-94-002). US EPA, Washington, DC, p 241... 

Whole effluent toxicity test species are generally not the same as the resident species that the results of WET testing are aimed at protecting, particularly where nontemperate environments (e.g., tropical and Arctic environments) are concerned, or for estuaries [177]. Also, not all resident species have the same sensitivities to individual or combined contaminants in effluents. Further, differences exist between sensitivities and tolerances of WET species. Such differences are not unexpected hence, it is desirable to use more than one toxicity test organism and endpoint to assess effluent toxicity. 

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. 

WET Whole effluent toxicity. The total toxic effect of an effluent measured directly with a toxicity test or bioassay. 

SETAC (1998) WET (Whole Effluent Toxicity) Toxicity of Complex Effluents, short course developed by SETAC Foundation for Environmental Education. Society for Environmental Toxicology and Chemistry, Pensacola, FL. 

A related general weakness in WET testing schemes involves the natural variability of effluents, and whole-effluent tests, which may be unrelated to the actual effluent toxicity but related to short-term spatial, temporal, and seasonal variation at a site. Interpretation of WET data is therefore complicated, as one may not be able to easily compare to the reference values like one can with chemical analyses. More frequent effluent testing may identify these atypical toxicity responses. 

---