Pollution refers to pressures that spread through the marine ecosystem, where they can have major and widespread impacts. Eutrophication, hazardous substances, marine litter, underwater noise and the introduction of non-indigenous species add to the pressures exerted on the Baltic Sea ecosystem. These pressures originate from societal and economic activities, both terrestrial and maritime. For most of these pressures, reaching sustain- able levels in the Baltic Sea is ultimately dependent on successful actions to restrict and limit their initial inputs, as subsequent remedial action is generally problematic, costly or impossible.

State of the Baltic Sea 2023 — The third HELCOM holistic assessment (HOLAS 3)

State of the Baltic Sea 2023 is a synthesis report that builds on, and integrates, results from a wide range of assessment products produced within the third HELCOM holistic assessment. Its role is to link information from the underpinning assessment products together, thus highlighting the holistic aspects. With this in mind, the summary report focuses on presenting the results and on an in-depth look at why we are seeing these results, providing over-arching context and analysis. The report helps develop a clearer picture of where we are and how things are connected, supporting coordinated and effective measures to strengthen the Baltic Sea environment.

Thematic assessment



The thematic assessment report on eutrophication (HELCOM 2023b) describes the changes occurring in the Baltic Sea relating to eutrophication, reflecting both the physicochemical and biological changes in the environment covering the period 2016-2021. The report presents a description of the methods, data and results on nutrient levels, as well as direct and indirect effects of eutrophication. 

The current assessment builds upon previous thematic assessments by improving methodologies, expanding the spatial coverage of existing indicators and including new indicators and threshold values for evaluating eutrophication status. 

Thematic assessment

Hazardous substances, Marine litter, Underwater noise, Non-indigenous species


The thematic assessment report on hazardous substances, marine litter, underwater noise and non-indigenous species (HELCOM 2023c), addresses each of these topics collectively regarded as pollution within the HELCOM framework. 

The report provides insights into the latest developments and current state-of-the-art evaluations for pollution. It builds upon initial progress started by HOLAS II (2011-2016) and corresponding work under aligned processes (e.g. EU level and MSFD relevant developments), moving towards indicator-based assessments for all mentioned topics. Additionally, areas of ongoing development, including those lacking fully operational indicators, are incorporated to present a broader picture of key pollution-related issues.