In 1917, German submarine UC-30 sank during World War I - it’s still leaking toxic chemicals more than a century later

Over a hundred years after the loss of a German submarine in the North Sea, science has discovered that its impact on the marine ecosystem is felt even now. The German submarine UC-30 was lost in April 1917 due to an explosion of a British mine near Rømø, Denmark, leaving 27 people dead. The wreck had lain hidden in the depths of the North Sea for close to a century until recently when scientists identified TNT contamination from the wreck in the water, sediment, and marine organisms. The discovery is just another example of the less-known side effect of the two world wars, namely the presence of thousands of sunken ships and weapons which are rusting away under the water.

A SUBMARINE LOST IN WORLD WAR I

UC-30 had left for Germany in April 1917 due to technical issues related to the mission to Ireland. The submarine had 18 mines and six torpedoes in addition to 45 crew members when it hit a British mine causing its sinking. It had been lying there almost for a hundred years until its discovery by Danish diver Gert Normann Andersen in 2016. The wreck had then been involved in the NorthSeaWrecks project. The water and sediments had been sampled in the area of the wreck together with the starfishes and mussels living in its vicinity with the help of the Danish Navy divers under the supervision of professor Katrine Juul Andresen from Aarhus University, Department of Geoscience. Their investigation proved that explosive substances coming from the wreck get into the marine environment.

SCIENTISTS FOUND TNT IN MARINE LIFE

The finding is significant since the pollution is not limited to the wreck only. According to Andresen, the scientists found that there is TNT contamination in the environment around, but as they argue, it seems to be rather localized. The study cited in ScienceDaily adds the broader evidence that the shipwrecks from the time of the World War may be the source of environmental pollution. The scientific paper, published in Marine Pollution Bulletin, has been prepared by Romina Marietta Schuster, Franziska Isabell Binder, Lillian Tabea Hannah Bünning, Jennifer Susanne Strehse, Katrine Juul Andresen, Maarten De Rijcke, Sven Van Haelst, Uwe Wichert, Philipp Grassel, Edmund Maser and Matthias Brenner.

Titled 'Environmental Risks of World War Shipwrecks: Field-Based Evidence of Biomarkers Using Caged Mussels in the North Sea', the study published in 2026 relied on field-based evidence of mussels to examine the environmental risks posed by world war shipwrecks. This is important considering that mussels co-exist with their environment. The identification of chemical compounds in marine organisms provides scientists with a new tool for understanding how pollution from old shipwrecks spreads in local ecosystems.

THOUSANDS OF WRECKS REMAIN UNDERWATER

UC-30 is just one out of many examples of a much bigger issue. In her report for the Danish Environmental Protection Agency released in 2024, Andresen listed 10,127 wrecks found in Danish waters. Around 15 percent were dated from the periods prior to and during both world wars, such as 1910-1920 and 1940-1945. This demonstrates the reasons why the long-term environmental impact of past conflicts is becoming a matter of serious concern for scientists today. It was estimated that 190,000 naval mines had been planted in the North Sea alone during the First World War. However, the cleanup is not an easy task since the removal of explosives is quite costly and dangerous and their detonation may lead to contaminating the area further.

Less destructive methods are thus being studied. Not every shipwreck must necessarily be disturbed. Scientists claim that shipwrecks that are partly or completely covered by sediment pose less threat of pollution since the layer can restrict the escape of pollutants. The problem is to determine which shipwrecks pose the biggest environmental threat.

The tale of UC-30 highlights the idea that the environmental effects of war may last much longer than the actual events themselves. UC-30 was lost back in 1917, yet almost a century later, it is possible for scientists to trace the presence of TNT related to the sunken ship within its vicinity. In other words, scientists are not saying that all submerged ships are potential environmental disasters. What the problem with these ships might be is that their further corrosion might lead to an increased exposure of the explosives and contamination at certain sites. There are more than 10,000 ships documented in the Danish waters alone. While the solution for researchers is obviously not taking everything out of the seabed, it consists of identifying hazardous sites and reducing their impact on the environment.