The UK has adopted a broader approach to the introduction of Environmental Quality Standard (EQS) for the aquatic environment than many other jurisdictions around the world, with a greater focus on the implementation of scientifically derived standards. This follows the publication of a report by the Royal Commission on Environmental Pollution in 1998 which drew attention to the need to recognise that whilst an EQS is often just viewed as a numerical value, it also has other important characteristics that need to be recognised if it is to be a practical and effective regulatory tool. One of the aspects that has not always been recognised was that of implementation assessment, i.e. the steps needed to ensure that a standard actually delivers environmental benefit or improvements. In many jurisdictions, there is considerable technical and sometimes political emphasis on the numerical value of the EQS (e.g. the critical concentration in an environmental matrix like water), including the method of derivation, the scrutiny of the reliability and relevance of the ecotoxicity test data and extensive deliberations of unquantified uncertainties in relation to the choice of assessment factor. The regulatory value of an EQS only comes through a comparison against a measured environmental concentration, yet only relatively limited regulatory effort has historically been expended on this component of the classic environmental risk assessment paradigm. For example, there needs to be an acceptable (i.e. small) uncertainty in the EQS, an appropriate analytical method and detection limit in the correct matrix, a method to deliver a comparison with the EQS and a robust statistical method to draw unbiased conclusions about environmental risk. In addition, we argue that there is a case for checking the consequences of introducing a standard against field data, wherever possible. This validation of the EQS rarely happens currently. We explain what implementation assessment is and why it is needed. We give examples of how implementation assessment can be integrated with EQS derivation and also present examples of what happens when the focus is only upon the derivation of a numerical value. It is clear from this evidence that advances in derivation methods need to be coupled with practical solutions of implementation if we are to realise environmental benefit from an EQS in a cost-effective manner.
Keywords: Ecotoxicity; Environmental Quality Standards; Environmental benefit; Implementation assessment.