TIE and TRE: An abbreviated guide to dealing with toxicity

The UK environmental regulator, the Environment Agency, is at present in th e process of introducing a revision to the effluent discharge consenting sy stem based on the assessment of whole effluent toxicity - so called Direct Toxicity Assessment (DTA). The concepts of the most 'sensitive' species and of risk assessment based on estimation of Predicted Environmental Concentr ation (PEC) form the basis of the proposed consenting structure. The object ive is to control the toxicity of point source discharges to riverine, estu arine and coastal waters and it raises the need for understanding of the na ture and expression of toxicity in such discharges. Internationally recognised toxicity test protocols are well established, en abling the quantitative measurement of toxicity with levels of confidence s imilar to the more traditional physical and chemical determinands, such as individual organic solvents, COD or metals. However, traditional protocols are seen as resource intensive and as involving high cost. This paper prese nts some experiences from the Zeneca Brixham Environmental Laboratory in th e characterisation of the toxicity expressed to freshwater and marine speci es by several chemical manufacturing effluents and in the conduct of a numb er of Toxicity identification Evaluations (TIE) using both standard and enh anced protocols for toxicity testing. (C) 1999 Published by Elsevier Scienc e Ltd on behalf of the IAWQ. All rights reserved.