Sunken WWI and WWII Ships and Subs Are Leaking TNT Pollution Into the Ocean — Gizmodo

RESOLVING THE LEDGER

Sunken WWI and WWII Ships and Subs Are Leaking TNT Pollution Into the Ocean — Gizmodo | AIPROPX

The German Type UC II minelaying submarine UC-30 was armed to do serious damage as it approached Denmark’s Wadden Sea Islands in 1917. The U-boat carried 18 mines, six torpedoes, and a crew of 27 Kaiserliche Marine seamen—all of whom sank to a watery grave when the German sub hit a British mine near the island of Rømø off Denmark’s southeastern coast.

UC-30 remained undiscovered for almost a century. But now, thanks to Aarhus University geoscientist Katrine Juul Andresen and multi-institution team, the Kaiser’s attack sub has joined a catalogue of roughly 1,500 sunken World War I and World War II vessels, as well as thousands more wrecks, mapped off the nation’s coast.

Andresen has been in a race against time to measure toxic leaks from these sunken artifacts to help remediation efforts to stop these wrecks from poisoning local marine food chains—including the many people who rely on North Sea commercial fishing for their sustenance.

For the new study, published this month in the journal Marine Pollution Bulletin, Andresen and colleagues used blue mussels ( Mytilus edulis ) as aquatic canaries in the undersea coal mine and found that leaking munitions are now damaging the enzymatic pathways these species employ to naturally detoxify.

“Pollution is definitely occurring,” Andresen explained in a statement. “We found traces of TNT in the wildlife, the seabed, and the water column.”

“It is likely a relatively localized source of pollution, but it will worsen as the wreck continues to deteriorate and expose more of the explosive material inside the mines,” according to Andresen, who collaborated with marine ecologists at Germany’s Alfred Wegener Institute and elsewhere on the new research.

The most common categories of chemical explosives now resting in these decaying munitions under the North Sea are 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazine (RDX), and 1,3-dinitrobenzene (DNB). None of them are safe, according to study coauthor Edmund Maser, a toxicologist at the University Medical Center Schleswig-Holstein in Kiel.

“The problem with these ammunition compounds is that they are not only toxic but also carcinogenic,” as Maser told the American Geophysical Union’s Eos last year, after publishing a related study .

Carcinogens bring a higher level of risk compared to lesser toxins that living things can more readily metabolize in small doses. “One single molecule could cause cancer,” Maser said.

Andresen, Maser, and their colleagues found trace amounts of TNT in the seawater surrounding UC-30 at around 72.6 nanograms per liter (72.6 parts per trillion). But that minute amount belies its impact: The researchers’ test mussels displayed not only trouble detoxifying, but disrupted metabolisms, and reduced energy for reproduction (specifically glycogen in the bivalves’ digestive tissue).

The study also conducted similar tests near two other wrecks, the WWI-era German light cruiser the SMS Mainz and the WWII-era transport KW 58 Hendricus, but Andresen noted that more work needs to be done both on the scope of these leaks and many still underexamined wrecks.

“The question is how significant the effect is and how far from the wreck the pollution impacts the marine environment,” according to Andresen, who previously authored a 2024 study funded by the Danish government on the wider scope of this toxic shipwreck problem.

“In the report, I found that there are 10,127 wrecks in Danish waters. Around 15 percent of them date back to the years around and during the two world wars,” she noted. “I am not aware of whether the agency has taken the work further since the report was published.”

Germany, Andresen pointed out, has devoted considerable resources to retrieving similar sunken munitions in the Baltic Sea, but solutions are costly. Andresen has considered ideas as complex as robots and as comically simple as blowing the aging ordinance up. But, in some cases, she said the best approach may simply be doing nothing at all.

“Some wrecks are fully or partially buried in the seabed. When covered by sand, the risk of polluting the surrounding sea is significantly lower,” Andresen pointed out. “It is a matter of identifying where the environmental threat is greatest—and then deciding whether the munitions on the wrecks should be removed.”