The Washington PostDemocracy Dies in Darkness

Deadly gases may be starting to leak from Europe’s World War weapons cemeteries

The Post's Rick Noack traveled to Estonia to learn more about the vast amount of unexploded ordnance left over from two world wars. (Video: Rick Noack, Sarah Parnass, William Neff/The Washington Post)

BERLIN — After World War I and World War II, officials decided to dump hundreds of thousands of metric tons of munitions into the oceans around Europe, which at the time appeared to be the most easily accessible disposal ground. Some of those weapons — including mines containing mustard gas — were simply dropped into the Baltic and North seas in the heart of Europe 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, the Belgian newspaper Het Laatste Nieuws reported that officials have grown concerned that one of those 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 paper said. The revelation followed months of official 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.

If confirmed, the leaks would hardly come as a surprise to other officials around Europe. They see themselves in a race against time to prevent the leaking of deadly gases and other hazardous substances, but they have struggled to have their concerns heard.

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 mines 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 munitions, the metal has rusted and become porous.

In the 1920s and 1940s, that may have seemed like a distant threat amid the still-vivid horrors of some of the deadliest conflicts in world history. But in more recent years, such leaks have posed a growing environmental threat. Activists have blamed the leaks in part for decreasing biodiversity in the Baltic Sea.

The problem extends far beyond the “weapons cemeteries” that are now making headlines.

In the neighboring Baltic Sea, more than 80,000 mines are believed to be beneath the surface. 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 of them 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 — for instance, last August in the Polish resort city of Kolobrzeg, where 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,” Cmdr. Peeter Ivask, the head of Estonia’s navy, told a visiting reporter late last year.

“Our mission here will last decades,” Ivask said.

And, likely, it will never be complete.

More on WorldViews:

Alleged Russian spy whale is refusing to leave and seeking Norwegians’ devotion, authorities say

Subversive Japanese otter mascot ready to take on John Oliver

The White House wants Maduro gone. But it may be helping him stay in power.