Germany's Corroding Sea Munitions Pose Growing Toxic Threat to Marine Life

Beneath the cold waters off Germany's northern coast, an invisible contamination is spreading. Somewhere in the murk lie roughly 1.6 million metric tons of bombs, mines, and ammunition—relics of two world wars and the frantic disposal campaigns that followed Nazi Germany's surrender in 1945. For decades, these weapons were treated as a hazard only if they might explode. Now, as their metal casings slowly corrode, they are becoming something else entirely: a source of toxic chemicals seeping into the marine food web.

When the Allies won the war, they faced a practical problem: what to do with an arsenal of weapons Germany no longer needed. The answer was to dump vast quantities into the North Sea and Baltic Sea. The munitions were left there, largely forgotten, until scientists began noticing something troubling in the fish. Edmund Maser, a toxicologist at Kiel University, explained the shift in understanding: compounds from the corroding weapons were entering the marine ecosystem, and those compounds were toxic and carcinogenic to both human and animal life.

The primary culprit is trinitrotoluene—TNT—the military explosive that filled countless shells and bombs. Jörn Scharsack of Germany's Thünen Institute of Fisheries Ecology has been searching for evidence of it in dab fish caught near munitions hotspots. He finds it regularly, though in tiny quantities measured in nanograms. The fish themselves appear healthy when pulled from the water. They do not suffer from the usual diseases—viral, bacterial, parasitic. But there is one abnormality that keeps appearing: tumors in the liver. In some areas near munitions dumping grounds, liver abnormalities show up in more than half of the fish examined, compared to a baseline of just one to two percent in uncontaminated waters.

The contamination does not stop with fish. Maser's team, working with the Alfred Wegener Institute in Bremerhaven, has found TNT-related compounds in mussels as well, where they trigger biochemical signs of oxidative stress—a process in which highly reactive forms of oxygen damage proteins, lipids, and DNA. This damage can be a pathway toward cancer. More alarming still, researchers have detected these compounds in tissue samples from two stranded whales, meaning the toxins have traveled up the food chain to apex predators. The chemicals are accumulating in animals that consume contaminated prey day after day, year after year.

The question naturally follows: if whales are being poisoned, what about people who eat seafood? For now, both Scharsack and Maser say the risk to humans remains low. Whales face constant exposure through their diet and their surrounding water; humans eat fish only occasionally. "One would need to eat lots of fish to really reach a level where it's getting dangerous," Scharsack said. But he also acknowledged the trajectory: as the munitions continue to corrode, more toxic substances will leach into the water. The problem is already worse in the Baltic Sea, where weaker currents allow pollutants to linger rather than disperse. Maser's examination of archived mussels dating back to 1985 showed TNT-related contamination increasing steadily from around 2000 through 2022. The levels remain low, but they are climbing. Over the coming decades—perhaps two, three, or four—concentrations could reach levels that harm people who consume seafood regularly.

The challenge now is that the window to act is closing. A study published in July identified 484 known or potential munitions piles in just two areas of the Baltic Sea, but of the estimated 1.6 million tons in German waters, around 1.5 million tons have yet to be mapped. Germany has only recently begun pilot projects for systematic clearance aimed at preventing environmental harm rather than just removing immediate explosive hazards. Torsten Frey of GEOMAR noted that recovering munitions from known locations is no longer the main obstacle—specialist companies can clear large quantities relatively quickly. The bottleneck is disposal and destruction. Germany is developing an offshore treatment platform to increase capacity, but Frey was clear: "This will be a marathon, not a sprint."

Even if all the large munitions are removed, small fragments will remain—pieces no larger than a sugar cube. Maser is investigating whether marine bacteria and fungi could eventually break down these residues into harmless compounds like carbon dioxide and water, but that work remains in the laboratory stage and cannot replace physical removal. The urgency is real. If action is delayed another 40 years, the metal casings will have corroded completely, and the toxic compounds will be dispersed throughout the water column with no way to recover them. "We need more of these platforms," Maser said. "We need to start as early as possible."