Whole-effluent toxicity testing

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. 

Chapman, P.M. Whole effluent toxicity testing - usefulness, level of protection, and risk assessment. Envir. Toxicol. Chem. 2000, 19, 3-13. 

EPA (U.S. Environmental Protection Agency) Regions 9 and 10 Guidance for Implementing Whole Effluent Toxicity Testing Programs, Technical Report Seattle, WA, 1996. 

Grothe, D.R. Johnson, D.E. Bacterial interferences in whole effluent toxicity tests. Environ. Toxicol. Chem. 1996, 15, 161-1(A. 

Whole-Effluent Toxicity Testing An Evaluation of Methods and Prediction of Receiving System Impacts. Pellston, Michigan, 16 to 21 Sep 1995. Published by SETAC, 1996. 

Grothe, D.R., Dickson, K.L. and Reed-Judkins, D.K. (eds.) (1996) Whole effluent toxicity testing an evaluation of methods and prediction of receiving system impacts, Proceedings from a SETAC -sponsored Pellston Workshop, Society of Environmental Toxicology and Chemistry, Pensacola, FL, 346 pp. 

De Vlaming V, Connor V, DiGiorgio C, Bailey HC, Deanovic LA, Hinton DE. 2000. Application of whole-effluent toxicity test procedures to ambient water quality assessment. Environ Toxicol Chem 19 42-62. 

Warren-Hicks W, ParkhurstB. 2003. Whole effluent toxicity tests using Bayesian methods to calculate model-based variability. SETAC 24th Annual Meeting, Austin, Texas. 

SETAC] Society of Environmental Toxicology and Chemistry. 2004. Technical issue paper whole effluent toxicity testing. Pensacola (FL) Society of Environmental Toxicology and Chemistry. 

The good laboratory practice criteria for whole effluent toxicity tests include species acceptability, exposure system conditions, physical and chemical conditions, and statistical data analysis methods. For instance, the test acceptability criteria for the larval fathead minnow 7 day chronic tests involves having 80% or greater survival of controls and an average dry weight of surviving control fish equal to or greater than 0.25 mg. 

Whole effluent toxicity tests may fail primarily for two reasons an aborted test due to a lack of good quality data generated (e.g., organism health or effluent sample exceeded its holding time of 72 h), or whole effluent toxicity is demonstrated to exceed permitted levels. 

We have seen that variability in toxicity testing can arise from repeat measurements made within a laboratory and also between laboratories. In reality, the variability seen between laboratories is a consequence of both within- and be-tween-laboratory sources of variability, and both are also subject to the within-test variability referred to earlier, as evident from differences between test replicates. Research based on a series of acute aquatic toxicity tests (Whitehouse el al., 1996) shows that variation between laboratories is higher than that between repeat tests in the same laboratory. This, in turn, accounts for more variability than that seen between replicates within a test. Similar findings are evident from the work of others in connection with the introduction of whole-effluent toxicity tests in the USA (e.g. Warren-Hicks and Parkhurst, 1992 Fulk, 1995). Over the years, a number of authors have examined variability in aquatic toxicity testing. Typically these describe variability in terms of the coefficient of variation (standard deviation divided by the mean) in EC50 or LC50 values that is achieved when the same toxicant is tested several times (or by several laboratories) using the same method. Table 2.3 summarises the results of a review of published data. 

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