MAMPEC (Marine Antifoulant Model to Predict Environmental Concentrations) is a commonly used model in EU antifouling (biocidal product type 21) exposure assessment. Several scenarios, e.g. EU regional marina scenarios (Excel Tool scenarios) and the EU fishnet scenario, have been developed in MAMPEC in order to harmonize the environmental risk assessment of antifouling products in the EU.The aim of the project was to determine representative values for certain input parameters in the Excel Tool Baltic and the Excel Tool Baltic transition scenarios. In addition, it was decided to evaluate the suitability of the EU fish net scenario for risk assessment in the Baltic Sea area. The project was conducted in cooperation between Nordic biocide authorities from Finland, Denmark Sweden and Norway.