The purpose of this report is to enable the Substances of Concern (SOC) Working Group to select the "substances of concern" and EFR instruments for detailed economic and policy analysis. Selection is based on previous analysis, meeting discussions and input from the SOC Working Group: In November 2001, a "Scan of EFR Instruments for Managing Substances of Concern" was presented to and discussed within the Working Group; In February 2002, the Working Group met to discuss the potential for both positive and negative EFR instruments to manage SOCs and to understand the appropriate points for applying potential instruments (i.e. to Schedule 1 substance, PSL substance or as early as "candidate for assessment" substance); and - In April 2002, the Working Group reviewed a range of Substances of Concern to select for potential case study topics. They focused in on three for further consideration: Mercury; Short chain chlorinated paraffins; and Smog precursors (nitrogen oxides and volatile organic compounds).