Hazardous substances are one of environmental problems of the Baltic Sea. Recently 11 hazardous substances and substance groups have been taken into consideration in the area and a specific programme established for these substances (HELCOM Baltic Sea Action Plan BSAP, hazardous substances segment). Project Control of hazardous substances in the Baltic Sea region – COHIBA focused on these eleven substances and groups, with the following main objectives: - identification of sources in countries around the Baltic Sea - development of innovative toxicity based cost-effective monitoring - analysis of flow patterns to the Baltic Sea - development of recommendations for management measures - knowledge transfer of best practices and capacity building. The main project website: www.cohiba-project.net www.environment.fi/syke/cohibaThis project gave methodological support to the implementation of the BSAP. The products of COHIBA are also applicable in the implementation of the EU Water Framework Directive and the EU Marine Strategy Framework Directive. COHIBA is one of the flagship projects of the EU Baltic Sea Region Strategy.The project had 22 partners in 8 Baltic Sea region (BSR) countries: Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland and Sweden. Finnish Environment Institute (SYKE) was the lead partner. Partners presented various branches including national authorities, municipalities, research institutes, NGOs and an intergovernmental organisation - HELCOM. The duration was 2009 – 2012. Activities of the project included development of wastewater control methods, and a new application of the Whole Effluent Assessment approach based on use of biological tests. Furthermore identification of sources of the target substances, assessment and models of discharges and flows, and informing and capacity building of stakeholders and end-users, especially in the eastern Baltic Sea area, were important parts of project plans. Main outputs included 3 large work package reports, a summary report and fact sheets on the target substances including information of measures and management, and several workshops and seminars, several times also in Russia, and a wide training programme in the eastern Baltic Sea Region (BSR). The project will also participate to the cluster 'Baltic Impulse - save the Baltic Sea waters' consisting of environmental projects in the BSRP.Results were produced on various levels: - increased awareness of the target substances among policy makers - contribution to joint assessments in the BSR on the substances - efficient exchange of information among stakeholders of HELCOM countries - information is targeted also to the general public and forwarded outside the BSR. Achievements: Baltic Sea is at present loaded by hazardous substances (HSs) in addition to the well-known impacts of nutrients and eutrophication. In the BSR a group of HSs has been recently selected for prioritised interest (substances and substance groups of the HELCOM Baltic Sea Action Plan BSAP). These prioritised substances have been also targets of the COHIBA project.COHIBA produced data and advanced information on these substances. Majority of the substances have been vaguely studied and comprehensive information has been lacking in the BSR as well as elsewhere. Use and occurrence of the substances can be related both to industrial sources and be residues from consumers' daily life. Thus the project increased the understanding of importance of various sources for emissions of the substances.Protocols to assess emissions were developed. Protocols can more generally be adapted for many HSs. Knowledge of emission sources and dimensions of emissions is needed at present frequently.A first comprehensive emission survey though the Baltic Sea region was carried out. Country studies on emission sources and on substance flow analyses (SFAs) were carried out. The project elaborated a summary of sources and emissions for the BSR. Modelling produced further information, i.e. inputs to the Baltic Sea. Local examples of Stockholm and of Copenhagen studied more deeply these regions.Also biological methods for wastewaters formed an integral part of the project's analyses. Biotesting widens the knowledge of quality of wastewaters, and it can build a better and sustainable basis to assess significance of discharges to water environment and to the Baltic Sea.More detailed project's work included a devoted concerted effort of case studies in all participating countries, for effluents of municipal and industrial wastewaters, stormwaters and landfills.In addition to screening of occurrence of the target chemicals, also biotests provided basis to develop a Whole Effluent Assessment approach for the Baltic Sea Region and a proposal of limit values for toxicity for HELCOM's use was provided.Management methods to decrease emissions and discharges of these substances were evaluated to recommendations. Methodological guidance documents provide a wide resource both for authorities, municipalities and industries.Information exchange especially in the eastern parts of the Baltic Sea region was vivid. Project information was discussed in 40 events with ca. 1100 participants.All these parts of the project are building blocks, which contribute to the development towards cleaner Baltic Sea.Project's outputs are available on the project website.