At the end of World War II it was necessary to dispose of large quantities of conventional and chemical munitions left over from German and allied stocks. Dumping at sea was considered the most appropriate solution at the time. Thus, somewhere around 50,000 tonnes of chemical munitions were dumped in the Baltic Sea (mostly bombs and shells). Some of these were disposed of in official dumpsites but there is evidence that these munitions are also present in other areas. For example, during transport to official dumping areas, munitions were thrown overboard while ships were en route.
The chemical warfare agents (CWAs) contained in these munitions include so-called blister gases like mustard gas (also known as sulphur mustard, the most widely produced during WWII) or nitrogen mustard, tear gases (like chloroacetophenone), nose and throat irritants (such as Clark I, Clark II and Adamsite), lung irritants (like phosgene or diphosgene) and nerve gases (such as tabun). These dumped chemical munitions may also contain certain amounts of explosives. It is assumed that the chemical munitions dumped in the Baltic Sea contained roughly 15,000 tonnes of CWAs.
These munitions pose a threat if the warfare agent inside is released. This can occur as the walls of the metal shells corrode. The extent of corrosion and the rate at which it is taking place are unknown, which raises concern among Baltic countries. The corrosion rate depends on various factors such as the material from which the munition is made, the wall thickness and the nature of the dumping ground (for example whether the munition is on solid ground and thus exposed to water or buried in mud and thus cut off from oxygen supply). Also limited is our knowledge about the ecological effects of the dumped CWAs on the marine environment.
The possibility that chemical munitions or their solidified contents can be washed ashore is extremely unlikely, so the threat to coastal areas around the Baltic Sea is not significant. However, pressure to exploit Baltic Sea resources is growing, with powerful new technologies enabling activities in more remote areas, including the deep-sea regions where dumpsites are located. Unaware of this risk, construction projects such as installation of wind farms or laying of cables and pipelines, as well as other sea-bottom activities such as trawler fishing are increasingly claiming space within the contaminated areas. Fishermen may be especially at risk since they can come into direct contact with dangerous toxins. Each year about 10 incidents of fishermen catching CWAs are reported. Furthermore, in the event of a mechanical disturbance, a large-scale leakage could pose a serious biohazard.
At the moment, safety recommendations regarding CWAs are regulated by a number of national legislations, as well as HELCOM recommendations. National governments around the Baltic Sea Region lack unified guidelines and contingency planning on what to do in case of a CWA-related accident.
CHEMSEA (Chemical Munitions, Search and Assessment) is a flagship project of the Baltic Sea Region Strategy, financed by the EU Baltic Sea Region Programme 2007-2013. The project was initiated in autumn 2011 and will last through early 2014. It has a budget of €4.5M, which is part-financed by the European Union through the European Regional Development Fund. The project is under the leadership of the Institute of Oceanology of the Polish Academy of Sciences (IOPAN).