Fears deadly gases may be leaking from World War weapons dumped at sea
After World War I and World War II, officials decided to dump hundreds of thousands of tonnes of munitions into the oceans around Europe, which at the time appeared the most easily accessible disposal ground.
Some of the weapons - including mines containing mustard gas - were simply dropped into the Baltic and North Seas rather than being taken to faraway dump sites near the Arctic Circle.
But the hidden legacy of those world wars may come to haunt the continent for decades to come.
This week, Belgian newspaper 'Het Laatste Nieuws' reported that officials have grown concerned one of the dump sites, close to the Belgian coastal municipality of Knokke-Heist, has started to leak. At the site, two out of 23 probed locations showed signs of contamination.
The revelation followed months of inquiries into what authorities fear could be a mounting public safety threat.
Used as a potentially deadly chemical agent during World War I, mustard gas can burn victims' skin, respiratory tract and eyes.
While mustard gas leaks from Europe's underwater weapons cemeteries were long considered a worst-case scenario, officials also are expressing alarm over leaks of explosives such as TNT from dumped land or sea mines.
While those substances have been contained inside metal cases for eight decades in the case of World War II, and about a century in the case of World War I, the metal has rusted and become porous.
Activists have blamed the leaks in part for decreasing biodiversity in the Baltic Sea.
More than 80,000 mines are believed to be lurking beneath the surface of the Baltic. Unlike the North Sea's mass dump sites, the locations of single mines are more difficult to track down. There are only vague maps of where the mines might be hidden, and most appear to be spread out across hundreds of miles.
Reminders of their potentially deadly impact have mounted. In 2005, three Dutch fishermen were killed after they accidentally caught an American-made World War II bomb in their fishing net.
Similar discoveries regularly trigger mass evacuations - last August in the Polish resort city of Kolobrzeg, for example, when three bombs were discovered in the nearby bay.
European navies help out with remote-controlled vehicles and clearance divers within their own territorial waters, but in some areas the density of explosives is believed to be so high that fishing is still prohibited there a century later.
Pipeline construction companies often hire private mine-clearance contractors to do the job if there is no way around it and when the explosives are found far out at sea, where European navies do not claim responsibility.
"It's unbelievable how many mines there still are," said Commander Peeter Ivask, the head of Estonia's navy. "Our mission here will last decades."
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