More than 200 fishermen have been injured by the chemical warfare agents (CWA) dumped in the Baltic Sea near the island of Bornholm after the 2nd World War. However, researchers have not been able to demonstrate any damage to fish or other organisms in the sea. Low concentrations of decomposition products from the CWA can still be measured in the sea bed, but the researchers believe that most of the CWA are now more or less decomposed. These are the conclusions presented in a newly published international paper whose main author comes from the National Environmental Research Institute (NERI) at Aarhus University.

2010.06.11

Mustard gas bomb KC 250 in its original wooden crate which made several bombs wash ashore on Bornholm where the elaborately fabricated crates were used as flower boxes (Bornholm Museum). 

Jens C. Pedersen

More than 200 fishermen have been injured by the chemical warfare agents (CWA) dumped in the Baltic Sea near the island of Bornholm after the 2nd World War. However, researchers have not been able to demonstrate any damage to fish or other organisms in the sea. Low concentrations of decomposition products from the CWA can still be measured in the sea bed, but the researchers believe that most of the CWA are now more or less decomposed. These are the conclusions presented in a newly published international paper whose main author comes from the National Environmental Research Institute (NERI) at Aarhus University.

”Remember that lack of proof of effects is not the same as proof that there are no effects,” says senior researcher Hans Sanderson in a warning not to overinterpret the results of a 4-year EU project, MERCW” (”Modeling of Ecological Risks related to sea-dumped Chemical Weapons”).

Nonetheless he admits that it is reasonably important that no serious effects on fish or other higher sea organisms from the CWA in the Baltic Sea sea bed were evidenced by the MERCW project – despite the efforts of more than 20 researchers using the most novel model methods, sea bed scanning and chemical and microbiological investigations.

The researchers have just presented their results as a “feature” in the acknowledged international journal ”Environmental Science & Technology”.

Only one intact container in 30 years

Hans Sanderson describes the huge challenge of investigating the effects of the old CWA: “Most were dumped more than 60 years ago at 100 m depth. It is a little like looking for a needle in a haystack. At the same time we talk of substances that have been illegal to produce since 1925. This implies that only limited information is available in the scientific literature on their toxicity, solubility and biological characteristics.”

Despite the difficult odds the project has demonstrated low concentrations of decomposition products of mustard gas and other CWA as well as an additive in chemical combat substances in the sea bed near Bornholm. However, Hans Sanderson emphasises that only decomposition products were found – not active CWA. And they were only found in the sea bed, not in the water column. He believes that most CWA are now decomposed.

Danish fishermen have only found one intact container with CWA during the past 30 years. In contrast, many fragments with lumps of viscous material encapsulated in wax have appeared. For these, one may suppose that the CWA are partly decomposed.”

He concludes that the only containers that might still be intact are buried in sediment material where they might be ploughed up by trawl gear – thus, it remains a good idea to maintain the fishing ban in the area despite its richness in fish.

“More than 200 Danish fishermen have been injured by CWA. Luckily no-one has died, but several have suffered lifelong health problems.”

The project has not been able to produce a good estimate of the number of containers with CWA buried in the sea bed. The geophysical investigations are subject to uncertainties related to the determination of the origin of magnetic objects and the nature of scanned objects – is it, for instance, stones or other hard material?

Facts on CWA

After the use of mustard gases during the 1^st World War a global ban was adopted in 1925 against their production. During the 2nd World War, however, both sides maintained a stock and a certain production and development. After the end of the war the Russians dumped approx. 32,000 tons chemical weapons with approx. 11,000 tons active substance in the Bornholm Basin, east of Bornholm. The dumping occurred in international waters and was not illegal at that time.

The most important CWA was yperite (mustard gas) whose “safe oral dose” for humans (the oral dosage to be ingested without adverse effects) is as low as 0.000007 mg per kg body weight. Also organic arsenic compounds, which are carcinogenic, were dumped.

Later, indications are that DDR dumped 200-300 tons chemical weapons during the period 1952-1965.

CWA have also been dumped in the Mediterranean Sea and in many other places such as USA, Australia, Japan, England etc.

Mustard Gas Bomb Type KC 250 – the most common bomb dumped in the Bornholm Basin (Bornholm Marine District). The detonator was removed from all bombs before the dumping.

Contact: Senior researcher Hans Sanderson, tel. +45 4630 1822, hasa@dmu.dk

Environmental hazards of sea-dumped chemical weapons. Sanderson, H. et al. Environmental Science & Technology. Vol. xxx, no. xxx, 2010