Abstract
The United Nations Environment Programme (UNEP) is currently coordinating negotiations to develop a binding global agreement by late in the year 2000 to prohibit, restrict or reduce the production, use or release of certain persistent organic pollutants (POPs). POPs are a small subset of organic chemicals whose characteristics of persistence in the environment, accumulation in biological organisms and toxicity make them priority pollutants and environmental risks to humans and ecosystems. Under the UNEP negotiation, a criteria expert group (CEG) has been established to develop criteria and procedures for the addition of substances, guided by the initial list of twelve substances selected for global action. 

It is therefore timely to investigate the scientific foundation for POPs screening criteria that have been used in other international, regional and national programs, focusing on the properties of persistence, bioaccumulation, toxicity and long-range transport in the policy context. The theoretical, empirical and multimedia modelling approaches used reveal that guidance for setting POPs screening criteria can be developed using a combination of science and policy input. These approaches suggest that criteria adopted under the NAAEC-CEC and UNECE-LRTAP regional agreements are reasonable and tend to isolate a limited number of clearly hazardous POPs from the majority of organic chemicals, while not being so stringent that the ability to respond to as yet unidentified risks is seriously compromised.