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From the Baltic to the Pacific, decaying underwater chemical arms expose a blind spot in disarmament—and a looming environmental hazard.
Image Source: Getty
In August 2024, over 15,000 metric tonnes of toxic agents were found in the Baltic Sea, dumped from World War Stockpiles. In May 2023, the Chemical Weapons Convention (CWC) conducted its fifth review conference. These conferences focus on updating conversations on chemical weapon (CW) resurgence, new technologies, and verification systems. An important and recurring conversation that was also highlighted in this edition of the CWC review conferences was discussing Abandoned Chemical Weapons (ACWs) and Sea-Dumped Chemical Weapons (SCWs). This discussion was reintroduced at the 29th Conference of State Parties (CSP) held in November 2024.
In the years following the First and Second World Wars, chemical weapons disposal was traditionally conducted by ocean dumping. At least four major military powers—the United States (US), the former Soviet Union, the United Kingdom (UK), and Germany—among others, have engaged in dumping obsolete, damaged, or captured chemical munitions in the ocean. They disposed of artillery shells, aerial bombs, and containers of mustard gas, Lewisite, and other toxic agents, often loaded onto scuttled ships—ships intentionally sunk to avoid capture—or dumped directly into the ocean. The CW material on heavy machinery, such as sunken ships, stayed in a small area undamaged. Conversely, water currents and other factors result in a wider distribution of smaller munitions, an aspect often neglected/ignored by the disposal crews, especially considering the safety and environmental effects of sea-dumping CW back then.
Although the US military records account for at least 74 dumping operations (32 off US shorelines and 42 off foreign shorelines) between 1918 and 1970, other countries have been less obtuse with their archive on SCWs. Russian sources claimed to ‘bury’ an estimated 160,000 tonnes of chemical weapons at sea in 1995. The worldwide total of reported ACW is estimated at a minimum of 1.6 million tonnes. However, the actual figure is likely much higher owing to incomplete or inadequate record-keeping.
The impact of SCW was seen by Hawaii Undersea Military Munitions Assessment (HUMMA) in Hawaiian shorelines—in the Mediterranean Sea—where 232 Italian fishermen sustained injuries alongside five fatalities due to exposure to mustard gas between 1946 and 1997, and increasing levels of toxicity in the Baltic Sea.
Furthermore, sea-dumped chemical weapons pose a triple threat. First, the highest risk lies with explosive materials in sunken ammunition, which may cause unexpected detonations. Second, there is a possibility of SCW getting disturbed by fishing activities, construction, dredging operations, or even natural disasters. This can trigger the munitions and lead to potential injuries or fatalities to the common masses/people. The impact of SCW was seen by Hawaii Undersea Military Munitions Assessment (HUMMA) in Hawaiian shorelines—in the Mediterranean Sea—where 232 Italian fishermen sustained injuries alongside five fatalities due to exposure to mustard gas between 1946 and 1997, and increasing levels of toxicity in the Baltic Sea. Moreover, the decaying containers release toxic substances into the seabed and water column, harming marine biodiversity and resulting in seafood contamination through bioaccumulation, indirectly impacting human health.
Legacy chemical weapons dumped at sea must be addressed in light of climate change and ocean degradation.. Currently, no international law or treaty mandates the removal of chemical weapons or their breakdown products from the oceans directly, despite being cognizant of the implications of such ACWs and SCWs on the United Nations Sustainable Development Goals (SDGs)—specifically, SDG 13 (Climate Action) and SDG 14 (Life Below Water).
Advances in technology have also expanded deep-sea exploration and industrial activity, heightening the risk of accidental encounters with chemical dump sites while enhancing the ability to detect, map, and safely dismantle ACWs and SCWs.
International chemical disarmament has made considerable progress. The 87-nation ratified the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, known as the 1975 London Convention, which legally prohibits the ocean dumping of hazardous wastes. Following this, the current largest treaty on CW non-proliferation—the CWC—was enforced to eliminate declared stockpiles. However, the CWC does not mandate retrospective action on abandoned or sea-dumped weapons prior to 1985—a significant loophole in their approach to destroying stockpiles and mitigating long-term environmental damage caused by sea-dumped chemicals. Additionally, no official notifications of sea-dumping operations have been submitted to the Organisation for the Prohibition of Chemical Weapons (OPCW) ever since the CWC came into effect. This lack of oversight and accountability constitute a key lacuna in global regulation.
The CWC does not mandate retrospective action on abandoned or sea-dumped weapons prior to 1985—a significant loophole in their approach to destroying stockpiles and mitigating long-term environmental damage caused by sea-dumped chemicals.
In response to these mounting concerns, several national, regional, and international measures have been adopted:
In a Joint NGO statement titled “Promoting International Cooperation on Abandoned Sea Dumped Chemical Weapons in the Context of a Climate Crisis,” the Chair, International Dialogues on Underwater Munitions, Terrance P Long, has quoted “A global solution to underwater munitions threats requires global cooperation.” A holistic strategy and global cooperation, therefore, must include the following elements:
The removal of declared chemical stockpiles under the CWC demonstrates the effectiveness of international cooperation. However, the CWC, OPCW, and nations must now address the unresolved issue of chemical weapons that have been abandoned and dumped into the ocean to safeguard future generations and marine health entirely.
Shravishtha Ajaykumar is an Associate Fellow at the Centre for Security, Strategy, and Technology at the Observer Research Foundation.
The views expressed above belong to the author(s). ORF research and analyses now available on Telegram! Click here to access our curated content — blogs, longforms and interviews.
Shravishtha Ajaykumar is Associate Fellow at the Centre for Security, Strategy and Technology. Her fields of research include geospatial technology, data privacy, cybersecurity, and strategic ...
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