Chemical weapons dumped in Baltic Sea

Approximately 32,000 tonnes of chemical weapons were submerged by the Soviet Union in the Bornholm Basin after 1945, according to HELCOM, the commission responsible for protecting the Baltic Sea's marine environment. These weapons include agents like mustard gas and were mostly stored in 250-kilogram bombs and shells.

Uncertain quantity of dumped weapons

Some estimates suggest the total amount of chemical weapons may be higher, ranging from 34,000 to over 50,000 tonnes. The exact number remains unclear due to logistical challenges and incomplete Soviet records.

Chemical weapons mistaken for natural objects

Mustard gas, the most common agent, forms compact blocks due to marine corrosion. These blocks are sometimes mistaken for amber or caught in fishing nets. Between 2000 and 2005, up to 1,110 kilograms of chemical weapons were caught annually by fishermen near Bornholm.

Contamination spreads beyond weapons

The contamination extends more than 250 meters around each chemical object, with traces of agents found in sediments and fish. A study titled Exposure status of sea-dumped chemical warfare agents in the Baltic Sea highlights how contamination spreads beyond the weapons themselves, including arsenical agents and mustard gas degradation products.

Chemical weapons found on shore

A 250-kilogram mustard gas bomb was discovered on Dueodde beach in Bornholm in 1992, a popular tourist spot. This shows the danger is not limited to the open sea, as these remnants can occasionally wash up on shore.

Ongoing monitoring and awareness efforts

Danish authorities and organizations like HELCOM continue to monitor the area, raise awareness among fishermen, and document discoveries. The exact period of weapon immersion is uncertain, with some studies suggesting it may have continued until 1965. As long as these weapons remain in the Baltic Sea, the sea will continue to return its dangerous legacy.