Far from the hunt for weapons of mass destruction in Iraq, corrosion, deeper fishing by trawlers and seabed cables are disturbing stockpiles in what once seemed inaccessible dumps from the Baltic to the Atlantic.
"It was terrifying. The pain was unbearable and my hands blistered all over," said Danish fisherman Walther Holm Thorsen, who was 15 when he threw a cracked grey canister back into the Baltic Sea after it was snared in the net of his trawler.
One of the first postwar victims of the Nazis in the 1969 accident, he said the pain came in the middle of the night, hours after he and another crew member had rinsed the oily substance off the fish. They had no idea it was mustard gas.
Thorsen spent three months in hospital, and his hands are badly scarred despite skin grafts. "Working as a fisherman now is hard -- my hands often feel like they're freezing," he said.
He said that trawler crew are now more aware of the dangers from chemical arms and have decontamination gear aboard. "But increasing rust will be a problem in future," he added.
Lack of knowledge
In some parts of Europe, no one even knows where tens of thousands of tonnes of munitions are.
Ole-Kristian Bjerkemo of the Norwegian coastguard said he hoped a new seismic survey would be carried out this year to locate ships loaded with Nazi stocks of mustard gas and the nerve agent tabun which were scuttled off Norway in 1945.
Norway knows the exact locations of just 15 of a probable 36 ships in waters about 600 metres deep off the southern town of Arendal, one of the main postwar chemical dumps with 168,000 tonnes of Nazi ammunition.
"This problem is not going to go away. As corrosion sets in, the likelihood of releases
principal scientist, Greenpeace research laboratories
"We want to know where they are," Bjerkemo said. A robot camera sent down in 2002 found a trawler net caught on one wreck. Sulphur, mustard and traces of arsenic compounds were found in the seabed but no chemicals in the sea water.
European governments reckon the stocks are safest where they are, slowly seeping poisons that may break down in contact with sea water or become diluted over decades.
Burying the problem?
The environmental group Greenpeace says they should be recovered. Apart from the threat to people working at sea, a sudden release of nerve gas could kill fish stocks. Other poisons might sink into the sediment and damage the food chain.
"Recovery of dumped munition is a costly and high-risk operation which could result in the release of large amounts of toxic compounds," the OSPAR commission of 15 nations protecting the north-east Atlantic said in a study.
"This problem is not going to go away," countered Paul Johnston, principal scientist at Greenpeace research laboratories. "As corrosion sets in, the likelihood of releases
Most dumps around Europe are from Nazi Germany but other countries from Britain to the United States have disposed of munitions at sea since World War One.
Led by Ireland, OSPAR governments are working on a common set of guidelines for fishermen on the frontlines, likely to be ready in June.