Controlling persistent organic pollutants - what next?

Within the context of current international initiatives on the control of p ersistent organic pollutants (POPs), an overview is given of the scientific knowledge relating to POP sources, emissions, transport, Fate and effects. At the regional scale, improvements in mass balance models for well-charac terised POPs are resulting in an ability to estimate their environmental co ncentrations with sufficient accuracy to be of help for some regulatory pur poses. The relevance of the parameters used to define POPs within these int ernational initiatives is considered with an emphasis on mechanisms for add ing new substances to the initial lists. A tiered approach is proposed for screening the large number of untested chemical substances according to the ir long-range transport potential, persistence and bioaccumulative potentia l prior to more detailed risk assessments. The importance of testing candid ate POPs for chronic toxicity (i.e. for immunotoxicity, endocrine disruptio n and carcinogenicity) is emphasised as is a need for the further developme nt of relevant SAR (structure activity relationship) models and in vitro an d in vivo tests for these effects. Where there is a high level of uncertain ty at the risk assessment stage, decision-makers may have to rely on expert judgement and weight-of-evidence, taking into account the precautionary pr inciple and the views of relevant stake-holders. Close co-operation between the various international initiatives on POPs will be required to ensure t hat assessment criteria and procedures are as compatible as possible. (C) 1 998 Elsevier Science B.V. All rights reserved.