From 1946 to 1993, the UK, France, Switzerland and others dumped 200,000 radioactive waste barrels in the Atlantic. Decades later, scientists are investigating the potential radioactive threat.

Between 1946 to 1993, European countries, including the United Kingdom, France, Belgium, the Netherlands, Sweden, Switzerland, and Germany, deliberately transported low- and intermediate-level radioactive waste to designated dump sites in the deep ocean. The radioactive waste was dumped in the North Atlantic, eventually totaling 200,000 barrels and deposited it there in sealed drums. The disposal concept assumed that deep-sea disposal was a fine idea for ditching low-level radioactive waste because it would sit in the barrels long enough to lose its potency. However, by 1975 the potential harms raised enough concern that the London Convention was brought into force to protect the marine environment.

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The scientists found badly corroded barrels, material spilling onto the seabed and signs of radioactive contamination around the dumping grounds. Researchers are trying to find out how much radioactive waste has leaked, how far it has travelled and whether deepsea marine life is absorbing it.

What did the scientists find three miles under the Atlantic?

For about a month, from May to June 2026, around 30 scientists aboard the French research vessel Pourquoi Pas? investigated one of the Atlantic’s former radioactive-waste dumping sites. The expedition was part of NODSSUM (Nuclear Ocean Dump Site Survey Monitoring), a French-led project launched in 2025 to understand what has happened to nuclear waste dumped in the ocean decades ago.

The manned submersible Nautile carried out 20 dives to depths of more than 15,400 feet, taking scientists directly to the area where the barrels had been located during an earlier expedition. Researchers inside the submersible Nautile collected samples from 50 or so barrels in five areas and also gathered specimens of surrounding sediment, water, and microbial communities.

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The results were alarming as several containers appeared to be in an advanced state of decay, with many heavily rusted and damaged after decades underwater. In some cases, material from inside the barrels appeared to have spilled onto the surrounding seabed mud.

Tests also detected radioactive substances associated with the dumped waste at levels higher than would normally be expected in the area. While some of the radioactive traces could have come from other sources, the expedition provided clear evidence that decades on the ocean floor have left some of the barrels severely corroded, with some showing signs of leakage.

The barrels are now in an advanced state of deterioration. So much so that several of them have already leaked their contents into the surrounding water. “The barrels alter the environment by providing a hard substrate that becomes colonized, potentially facilitating the transfer of radionuclides to living organisms,” two researchers involved in the project, Javier Escartin and Patrick Chardon, wrote in The Conversation. “This is one of the first radioecological studies in the deep sea, requiring the implementation and development of new procedures and methodologies ranging from the definition of the sampling strategy to onboard radiation protection.”

The researchers will now take back the samples to the lab along with samples of water, sediments, and living organisms to further study how the radiation is interacting with the environment and its inhabitants.

Animals growing on the barrels

When Nautile reached the dumping site, researchers found anemones, sponges, crabs and other marine life living on and around the barrels. Scientists collected organisms, water, mud and microbes from the area and nearby natural habitats for comparison. So far, there is no evidence that seafood eaten by humans is contaminated. For now, researchers are focused on understanding the impact on the ecosystem surrounding the waste.

Photos show some animals are now growing on the barrels. A reminder that wildlife has no concept of trash when finding a new home. Scientists from France, Norway, Germany and Spain will spend the coming months examining them to identify the radionuclides present, determine their concentrations and understand how radioactive material has moved through the surrounding environment. Once completed, the research could become one of the most detailed studies of its kind, according to the authors.

The environmental damage caused by past generations cannot be reversed, but researchers say understanding how these deliberate episodes of pollution affected the ocean and its surroundings could offer valuable lessons. Such findings may help future generations recognise the long-term consequences of nuclear waste dumping and avoid repeating similar mistakes.

Is there a radioactive threat?

Researchers have examined only a tiny fraction of the entire dumping ground. So, is there a radioactive threat? Some barrels have clearly degraded, with material escaping and radioactive substances detected around the dumping grounds at higher-than-expected levels. Scientists are now investigating how much has leaked, how far it has spread and whether marine life is absorbing it.

Radioactive traces from past nuclear testing and accidents make the analysis more difficult. So far, there is no evidence of an immediate threat to humans, but researchers are awaiting results from samples collected during the 2025 and 2026 expeditions to understand the long-term impact.