Thousands of tonnes of chemical warfare agents south of Gotland

27 October, 2020

The Second World War is still going on in the Baltic Sea, with significant risks for animals and the marine ecosystem. At the bottom, some 15,000 tonnes of mustard gas and other toxic warfare agents are rotting. “Chemical warfare agents should not be allowed in fish or shellfish,” says Fredrik Lindgren at the Swedish Agency for Marine and Water Management.

That history sometimes meets the present becomes clear in the case of chemical warfare agents from the Second World War. And not least, it also shows that for a very long time in human history, the sea has acted as a dustbin.

At the end of the war, hundreds of thousands of tons of chemical weapons from the German war industry ended up in the hands of the Allies. These were lethal and potent weapons that had never been used, but were still active. Somehow the weapons have to be managed. The solution was to lower the toxins in the sea. The British, Americans and Russians together dumped hundreds of thousands of tonnes of active munitions in selected locations in the Baltic Sea: the Little Belt, east of Bornholm and the Gotland Deep. And there they still are.

More than 60 years later, three women are walking among the raucous people in the southernmost part of Gotland and wondering how things could have turned out this way. That seals might have been visiting the decomposed remains of poisons that were meant to kill humans. That man has thrown these weapons into the sea.

– It’s so amazing that this has happened. It’s really deeply disturbing,” says Cecilia Åsberg, Professor of Gender, Nature and Culture at Linköping University.

Cecilia and her two research colleagues Astrida Neimanis and Aleksija Neimanis had read a report on dumped chemical weapons. They had also heard of seals with strange lesions on their faces. Some scientists had been struck by the idea that seals swimming in areas with thousands of chemical toxins might have gotten too close in their curiosity.

They came to Gotland to see if they could find any physical traces of the dumped weapons. But also to try to understand the threads between the past chemical industry, war and mindless environmental aspects that still haunt our waters. – Decades after the weapons were supposed to be rendered harmless, they are reactivated, both literally in fishermen’s nets and perhaps in seals’ faces, as well as in people’s minds,” Cecilia continues.


The background can be traced back to 1935 when Germany began to rearm its chemical weapons arsenal. They would certainly come in handy in a coming great war, Hitler thought. But it didn’t work out that way. Chemical warfare agents were hardly used at all during the Second World War.

In the final stages of the war, the German war command ordered that the chemical weapons must not fall into enemy hands. This was especially true of those varieties that were thought to be unknown to the Allies, such as Tabun nerve gas. However, the Germans decided not to destroy the weapons because the handling could be misinterpreted as a prelude to using them. Several magazines were evacuated under strict secrecy and the weapons were transported to various depots in Germany.

After the end of the war, the Allies settled the future of Germany. They set guidelines for the total disarmament and demilitarisation of Germany. Some 305,000 tonnes of chemical weapons were found and it was decided that all munitions would be destroyed. At that time, dumping at sea was the only known way to get rid of the chemical warfare agents.

mustard gas

The initial plan was to dump the ordnance in the Atlantic, but both technical and economic problems prevented this and areas closer to hand were chosen. A total of five dumping areas were used. The Americans and British loaded ships with chemical munitions and sank them in the Skagerrak. The Russians suffered from a shortage of ships and therefore dumped the ammunition directly from the ship’s deck at two locations in the Baltic Sea. They were simply thrown overboard. As a result, the means of combat are spread over a very large area. The exact positions are also not certain.

East of Bornholm, 32,000 tonnes of mustard gas, Clark I and Clark II, chloracetophenone, phosgene, nitrogen mustard gas and tabun were dumped. Approximately 50 miles south of Gotland, 2,000 tonnes of various chemical warfare agents were dumped, such as mustard gas, adamsite, and others (see glossary).

Years went by, but eventually it was realised that this might not have been a very bright idea, as it could actually be a danger to both humans and animals. But who should bear the responsibility was a difficult question to answer because it had been carried out when it was not contrary to any applicable international law. Dumping at sea was only completely banned by the London Convention in 1972.

second war
Tre bomber

In 1974, the Baltic Sea countries signed the Helsinki Convention, committing themselves to take the necessary measures against marine pollution and to protect and improve the marine environment of the Baltic Sea.

Salvage of the wrecks was discussed for a long time. But the arguments against salvage were many. The wreckage and ammunition had been heavily corroded. The danger to the environment and the salvors was imminent. The depths are great and the whole thing is a project that would cost billions. Then there is the problem of dealing with the chemical weapons once they have landed.

Russian scientists put forward an idea to cover the wrecks. Another suggestion was a method, also proposed by the Russians, of building a sphere over the wrecks at the bottom. Through a tube in the sphere, various substances are injected to neutralize the chemical warfare agents, and through another, the neutralized water is sucked out. Finally, the chemical waste that has been released is recovered. But none of these ideas were developed further.

Today, several different cooperation bodies are working on the issues of the dumped chemical warfare agents. The most important for Sweden is the Helsinki Commission, HELCOM, which in 1993, on Sweden’s initiative, set up a committee to investigate dumping in the Baltic Sea area. In their report, they recommend further research on the environmental impact of arsenic compounds and the guidelines that should apply to fisheries.

It has been found that all chemical warfare agents have a density greater than seawater and therefore remain on the seabed after the munitions have disintegrated. The water pressure also prevents the vapours from becoming airborne. At the same time, the report notes that there are major gaps in knowledge about the impact of chemical warfare agents on the marine environment. The studies carried out on various marine organisms have almost exclusively concerned mustard gas. But even there, knowledge is not great.

Another risk factor is that fishing gear can carry “lumps” of chemical warfare agent lying on the bottom. Danish fishermen in the Baltic Sea have reported hundreds of cases of mustard gas in their fishing gear, probably because the ammunition is scattered directly on the seabed.

And this has been going on for decades. But no one seems to be any the wiser about what needs to be done. However, everyone agrees that some form of monitoring must be introduced. As mentioned above, knowledge about the degradation time and impact of chemical warfare agents on marine life is very limited.

The next major step was taken in 2014 when a report was compiled by CHEMSEA (Chemical Munitions, Search and Assessment), a stakeholder group composed of authorities and actors from the countries around the Baltic Sea. It was this report that Cecilia and her colleagues had read. And it was frightening reading.

During the investigations in the Gotland Deep area, researchers found an estimated 8,000 objects suspected of being war material potentially containing chemical warfare agents. After analyses on cod from the area with chemical warfare agents, and comparisons with fish from other locations in the Baltic Sea, researchers recorded no obvious visible differences. But at the cellular level, they could see abnormalities. Tests on mussels also show such tendencies. The report suggests that this research needs to be continued and expanded.

The degradation of chemical warfare agents works differently for different poisons, but should be considered as persistent poisonings. The contamination is most evident in the Bornholm Basin, where analyses showed that virtually all samples contained contamination that can be traced back to the weapons. It looks a bit different in other places, the bottom samples show different responses. Sometimes there was no trace, sometimes there was. This may be due to local differences in the environment. However, in all areas surveyed, there is a clear relationship between the total concentration of arsenic and the presence of chemical weapons.

It is also believed that corrosion and leakage from the containers containing the chemical warfare agents will increase over time. It is therefore necessary to monitor and continuously carry out pollution controls in these areas.

Although the areas are marked on charts, fishing activities continue in these places and over the decades there have been accidents when the chemical warfare agents have become entangled in fishing gear and ended up on board vessels. Chemical warfare agents thus continue to be a threat to people on board fishing boats.

weapon experts

In the last twenty years alone, 115 incidents involving chemical weapons have been reported to the authorities. The deadly objects in the Baltic Sea are found both inside and outside the known dumping areas, which leads to the conclusion that there is a clear risk of exposure to hazardous substances that extends far beyond the official dumping sites.

The same problem also applies to other activities carried out on the Baltic Sea floor, such as the construction of wind farms or the laying of pipelines, cables and other equipment. It also needs to be borne in mind that the impact of the environment where chemical warfare agents are present can cause damage that we cannot predict – chemical warfare agents stay at the bottom longer than previously thought.

But it’s not just activities at sea that are at risk. Recent decades have also shown that chemical warfare agents can easily reach land by washing containers of the poisons ashore along the coasts. And if these are handled incorrectly, they can pose a great danger to people.

Another aspect is marine activities that stir up the seabed. Such activities risk releasing toxins embedded in the sediment, thus directly causing threats to both humans and the environment. The most dangerous situation is when sediment from excavation operations is lifted onto ships for disposal.

CHEMSEA’s overall conclusion on chemical warfare agents on the Baltic Sea floor is that the dumping sites do not pose an acute threat, but that they will continue to be a problem that needs to be addressed. On the one hand, the warfare agents represent sources of poisoning whose extent we cannot know and which are also difficult to control. On the other hand, they also represent an economic risk from the perspective that the Baltic Sea is an uncertain place. Hence a potentially costly area for investment. And from an environmental perspective, the toxins represent a risk to marine species through constant exposure. The data available today is not sufficient to predict the consequences or how the situation will evolve. If steady and slow corrosion and leakage continues, the problem will be long-lasting, but localised. Eventually, the degradation process will remove most of the threat. However, if leakage increases, the degradation process will not balance the amount of leakage and then severe problems can occur. More studies are needed, especially on the evolution over time, including the extent of leakage and the rate of corrosion. All to determine which scenario is the most likely.

“Chemical warfare agents shall not be present in fish or shellfish. Regardless of the amount of poison, levels of chemical toxins are always alarming.”

Fredrik Lindgren, Investigator at the Marine Environment Management Unit of the Swedish Maritime and Water Agency

During the summer of 2019, the Agency carried out new investigations, both in the Baltic Sea and off the west coast, and continued to find residues of chemical warfare agents in the sediments in both areas. The extent of pollution and the possible spread of these toxins to marine organisms is of great interest. And in the end, it leads to the need to find out what possibilities there are to put in place management measures.

– On the west coast, we found traces of chemical warfare agents in shrimp, crayfish, flatfish and eels,” says Fredrik. And in the Gotland Deep we found the same thing for cod and flatfish. The levels are very low, but there is always something worrying about the levels of chemical toxins in seafood.

The risk of spreading the contents of the chemical warfare agents increases over time as the containers rust and natural flow conditions carry the toxins to new locations. In the Gotland Deep, all sediment samples contained chemical toxins, indicating that large parts of the area are affected. The same substances found in the sediments can also be found in the tissues of the marine organisms caught from the same positions.

Despite many years and many different studies, the impact of chemical warfare agents on marine organisms is still relatively unknown. In addition to the direct damage to the animal, indirect effects can also occur when substances are stored in tissues or for animals higher up the food chain.

– This problem will not fall through the cracks, explains Fredrik. It is on the agenda of several authorities. We must continue to monitor developments.

But exactly what measures may be put in place is not clear. And apart from the knowledge gaps, it is also complicated because it involves so many different countries. This often makes the issue of liability difficult to manage.

– However, there may be a need to change the way fishing is carried out in these areas. Maybe we need to regulate where bottom trawling can take place,” Fredrik concludes.

Cecilia Åsberg and her research colleagues find no physical traces of the chemical warfare agents among the roughened shoreline on southern Gotland. Nor do they get answers that establish with certainty the causes of the damage to the seals’ faces. Instead, they seek to understand the cultural, historical, emotional and environmental structures that bind weapons together, preserve them and hold them in place in an uncertain future. They write an article to share their thoughts. They are convinced that we need to find new ways to talk about problems of this kind. New ways that can help us open our eyes and engage better with the transgressions that have been committed and are now part of the sea. Then we can develop the capacity to act in the right way. Because we can’t keep using the sea as a solution to problems, we have to stop letting the water wash away our sins.

Footnote 1:
Glossary of chemical warfare agents dumped in the Baltic Sea:
Mustard gas – Mustard gas is a compound that contains sulphur and chlorine, among other things. Pure mustard gas is a colourless and odourless liquid. The snake is dark brown in colour and has a faint mustardy or garlicky smell that attacks the skin and mucous membranes. The eyes are very sensitive and the gas causes inflammation, which can lead to blindness, skin redness, blisters and burn-like sores, damage to the airways and lungs, which can be fatal at higher doses.
Nitrogen mustard gas – Differs from ordinary mustard gas in that the sulphur is replaced by nitrogen.
Chloracetophenone – In the pure state the substance is colourless crystalline. The technical product is coloured grey or yellow-brown and has an aromatic odour. The substance is highly irritating to the eyes but also irritates the respiratory tract and moist skin. The effect is instantaneous, but passes when exposure ceases.
Clark I (diphenylchloroarsine) – Organic arsenic compound. In its pure form, it consists of colourless crystals, while the technical product is grey or dark brown in colour and has no pronounced odour. Clark I has a very strong irritant effect on the upper respiratory tract, causing runny nose and tears, difficulty breathing, sneezing, chest pain, headache, nausea and vomiting.
Clark II (diphenylcyanarsin) – Very similar to Clark I. Clark II, however, has an onion or bitter smell. The damaging effects are the same as for Clark I.
Adamsite (phenarsazine chloride) – Organic arsenic compound named after an American chemist. In its pure form, adamsite consists of light yellow needle-shaped crystals. The technical product is coloured green by by-products. The substance has no particular odour and the adverse effects are the same as for Clark I.
Phosgene – Made up of carbon, hydrogen and chlorine. The only gaseous chemical warfare agent in the German arsenal. The technical product is yellow or reddish-yellow and has a sweet smell reminiscent of spoiled fruit or freshly cut hay. Phosgene acts as an inhalation poison. The first signs of poisoning occur only after 3 to 12 hours. That’s why you can eat a lot without noticing. Symptoms include coughing, lack of oxygen, pneumonia and choking. Tabun – Organic phosphorus compound. The only nerve gas produced on a large scale. In its pure state, the compound is a clear liquid while the technical product is brown in colour. Taboos are absorbed by inhalation of gas or aerosol and by skin penetration of droplets. Symptoms at low doses are pupil constriction, shortness of breath and pressure across the chest. Lethal doses cause drowsiness, sweating, vomiting, convulsions, involuntary defecation and urination, convulsions and finally suffocation.

Footnote 2:
Article Fathoming chemical weapons in the Gotland Deep, by Astrida Neimanis (The University of Sydney, Australia), Aleksija Neimanis (National Veterinary Institute), Cecilia Åsberg (Linköping University)

Footnote 3:
Professor Cecilia Åsberg is co-founder of The Posthumanities Hub. A feminist platform for diverse projects, international networks, arts and communication, visiting scholars, natural and cultural scientists meeting in creativity and curiosity across university, national and discipleship boundaries. Projects at The Posthumanities Hub create encounters for art, science, theory and society based on interdisciplinary humanities.

Text: Björn Hagberg
Photo: Magnus Martinsson/N/TT, Jorma Valkonen/TT, Sydsvenskan/IBL, Sjöfartsverket, Sipa/TT

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