Risks

(Disclaimer: This page is under development)

Munitions in the sea can affect people, marine ecosystems and human activities in different ways. Their presence does not create the same level of risk everywhere. The consequences depend on the type and condition of the munition, its location, the surrounding environment and the likelihood that it will be encountered or disturbed.

Across the scientific and technical literature, these risks are commonly grouped into three principal and interconnected mechanisms: explosion hazards, toxic exposure and environmental contamination. A single munition may present more than one of these risks at the same time.

Explosion hazards

Unexploded ordnance may still contain functioning explosive components or fuzes. Depending on its design and condition, a munition may be triggered by contact, movement, impact or vibration. Certain sea mines may also respond to acoustic, magnetic or pressure influences.

An underwater explosion generates intense shock waves, rapidly expanding gas bubbles and impulsive sound. These effects can kill or seriously injure people, damage vessels and offshore infrastructure and harm marine mammals, fish and other organisms. Investigations following underwater clearance explosions have, for example, documented severe blast-related injuries in harbour porpoises.

Ageing does not necessarily make a munition safe. Some components may stop functioning as originally intended, while the main explosive charge remains hazardous. Corrosion may also make an item more fragile or difficult to handle. The continuing explosive hazard posed by decades-old ordnance was demonstrated by the 2020 explosion beneath the fishing vessel Galwad-Y-Mor.

Toxic exposure

Munitions can pose risks even when they do not explode. Direct contact with chemical warfare agents, explosive compounds or incendiary materials may cause poisoning, chemical burns, respiratory damage or other serious injuries.

Chemical warfare agents can escape from damaged shells, containers or wrecks. They may be brought to the surface in fishing gear, contaminate catches and equipment or, in some cases, wash ashore. Encounters involving chemical and conventional munitions have been recorded across European fishing grounds and coastal waters.

White phosphorus is a particularly visible example. Fragments from incendiary munitions may resemble amber, wax or ordinary stones. Once dry and exposed to air, they can ignite and cause severe burns. Such finds have repeatedly been reported on parts of the Baltic coast.

Environmental contamination

As munition casings corrode, break apart or are physically damaged, explosive compounds, chemical warfare agent degradation products, metals and other hazardous substances may be released into surrounding water and sediments.

The scale and movement of contamination differ considerably between sites. They depend on the materials present, the condition of the munitions, whether they are exposed or buried and local conditions such as salinity, oxygen availability, temperature, currents and sediment characteristics.

Contamination is generally highest close to exposed explosive material, damaged munitions, munition-bearing wrecks and heavily affected dumping sites. Dissolved substances and contaminated particles may nevertheless spread beyond the immediate source area.

One munition can create several forms of risk simultaneously.
It may represent an explosion hazard, expose people or organisms directly to toxic substances and release contaminants into the surrounding environment.

People and coastal communities

Fishers, vessel crews, divers, port workers and offshore personnel face some of the most direct risks because their work may bring them into contact with exposed or buried munitions.

Bottom-contact fishing gear can disturb or recover munitions, sometimes bringing them close to or onto a vessel before they are recognised. This can expose crews to both explosion hazards and toxic substances. In 2005, three fishermen were killed in the southern North Sea after a Second World War bomb caught in their nets exploded aboard their vessel.

In 2020, the fishing vessel Galwad-Y-Mor disturbed a 250-kilogram unexploded Second World War bomb while recovering crab pots in the North Sea. The resulting explosion injured five crew members and caused major damage to the vessel.

Beach users, swimmers, recreational divers and anglers may also encounter munitions, chemical-agent residues or incendiary materials in shallow waters or along the coast.

The consequences for coastal communities can extend beyond direct injury. Discoveries may affect access to fishing grounds, beaches, ports or other marine areas and can create uncertainty for livelihoods that depend on fisheries, tourism and coastal activities.

Marine ecosystems

Explosive compounds such as TNT and their transformation products have been detected in water, sediments and marine organisms near individual munitions, wrecks and dumping sites.

Some munition-related substances can be taken up by mussels, worms, crustaceans and fish, particularly by organisms living, feeding or filtering water close to the seabed. Research in German coastal waters has detected TNT transformation products in dab living near munition dumping sites.

Organisms may metabolise and eliminate some compounds, but continuous or repeated exposure can still result in detectable residues and biological responses. Research around munition-bearing shipwrecks in the Belgian North Sea has identified explosive contamination and biological responses in mussels and fish.

Laboratory and field studies have reported metabolic disturbance, oxidative stress, cellular damage and changes in detoxification processes. Liver abnormalities have also been observed in fish at some contaminated sites. However, findings differ between locations, and marine organisms are simultaneously exposed to other pollutants, diseases and environmental stressors. One study of dab in German coastal waters detected explosive contamination but did not establish clear health impairment attributable to it.

Contaminated organisms may provide a pathway through which munition-related substances enter the marine food web. Current evidence does not show that explosive compounds consistently increase in concentration at higher trophic levels.

An assessment of commercially available seafood from the North and Baltic Seas found that the munition compounds examined presented a limited risk to consumers under the conditions studied. However, the available evidence does not cover every region, species or hazardous substance. Direct contamination of a catch by chemical warfare agents, white phosphorus or exposed explosive material represents a different and more immediate form of toxic exposure.

Underwater explosions can also affect marine ecosystems. Shock waves and intense impulsive sound may injure or kill marine mammals, fish and other organisms. The physical disruption of munitions may additionally disperse explosive residues and contaminated material.

Maritime activities and infrastructure

Activities that interact directly with the seabed are particularly likely to encounter munitions. These include:

• offshore wind-farm construction
• subsea cable and pipeline installation
• dredging and port development
• fishing with bottom-contact gear
• anchoring and seabed preparation
• some forms of aquaculture and coastal construction

The risks to these sectors include injury, damage to equipment, interruption of operations, project delays, route changes and additional costs.

Munitions can affect projects even where no detonation occurs. Incomplete historical information, unidentified seabed objects and unexpected discoveries can restrict access to parts of a site or require project plans and construction schedules to be changed.

Technical surveys may identify objects or anomalies that require further investigation, but not every detected object is a munition and not every munition can be detected easily.

The fishing sector is particularly exposed because munitions can become caught in trawls, dredges, nets or crab-pot lines. Chemical warfare agents may also contaminate catches, equipment and vessels. Reported encounters are not confined to officially designated dumping sites.

Tourism is generally less exposed, but individual objects, chemical residues and incendiary materials may be discovered on beaches or in shallow coastal waters. Even isolated incidents can affect access to coastal areas and public confidence.

More broadly, the presence of munitions creates uncertainty, cost and liability for activities that depend on safe access to the seabed and coastal environment.

Security and illicit use

Accessible underwater munitions can sometimes become a source of explosive material for illicit or criminal purposes.

Historical accounts from Malta describe explosive material recovered from marine ordnance being used for purposes including fireworks production.

In Sicily, explosives recovered from unexploded Second World War ordnance were supplied to organised crime and linked to Mafia bombings, including the 1992 killing of anti-Mafia judge Giovanni Falcone.

A 2004 report from Taranto, Italy, described poachers exploiting underwater wartime remnants to recover explosives for bombs used in illegal blast fishing.

Such cases appear to be uncommon, but they demonstrate that explosive material may remain recoverable and usable decades after entering the sea.

Detailed information on the location, quantity and condition of munitions may also have security implications where it could facilitate unauthorised recovery or deliberate interference.

Type and condition of the munition

An unexploded bomb, sea mine, chemical shell, torpedo and ammunition cargo within a shipwreck do not present the same hazards.

The risks depend on factors including:

• the type and quantity of explosive or chemical material;
• the design and condition of the fuze;
• the integrity of the casing;
• whether the contents are contained or exposed;
• the sensitivity of the item to movement or disturbance.

Individual munitions may age differently even where they have remained underwater for similar periods. The diversity and changing condition of underwater ordnance are therefore central to understanding the risks involved.

Location and environmental conditions

Water depth, salinity, oxygen availability, temperature, currents and sediment conditions influence corrosion, burial and the movement of released substances. Some munitions lie exposed on the seabed, while others are partially or completely buried. An exposed item close to a fishing ground, beach, port or construction site may present a different risk from a deeply buried object in an area with little human activity. The presence of sensitive habitats and species can also influence the ecological consequences of contamination or underwater explosions.

Likelihood of disturbance

A munition that remains undisturbed may present a different risk from one located in an area used for fishing, dredging, anchoring or offshore construction.

Activities that interact with the seabed can:

• strike or move a munition
• expose previously buried objects
• recover items in fishing gear
• damage corroded casings
• release explosive or chemical contents

An object that has remained undisturbed for decades may therefore become relevant when a new activity reaches its location.

Concentrated and dispersed munitions

In some areas, large quantities of munitions are concentrated in dumping grounds, wrecks, former minefields, ports or military ranges. Such sites may contain substantial quantities of explosive or chemical material within a relatively small area.

Elsewhere, individual items are widely dispersed as a result of combat, aerial bombing, transport losses, en-route dumping and military exercises.

A single munition can create a serious local hazard even where the wider area is not considered heavily affected. Recorded encounters show that munitions are found well beyond recognised dumping grounds.

Incomplete and uncertain information

Historical records are often incomplete, inaccessible or based on approximate positions. Official dumping areas may represent only part of the affected zone, while many wartime losses, accidental releases and individual disposal events were never documented.

Munitions are therefore frequently found outside recognised dumping grounds or areas marked as hazardous. Their location and condition may remain uncertain until individual objects are investigated.

The seabed is also dynamic. Storms, currents, erosion, sediment movement, trawling and dredging can expose, bury or move objects. Technical surveys provide valuable information, but not every detected object is a munition and not every munition can be detected easily. Deep burial, heavy corrosion, non-ferrous materials and surrounding wreckage can all complicate identification.

The risks posed by munitions in the sea are not static. Casings corrode, sediments move, objects become exposed or buried and human activities expand into areas that may previously have remained undisturbed.

These processes do not affect every munition in the same way. Ageing may prevent some components from functioning as originally intended, while the main explosive charge remains hazardous. At the same time, deterioration can increase the release of toxic substances.

Different risks can also interact. A munition may simultaneously represent an explosion hazard, a source of toxic exposure and a source of environmental contamination. Disturbing or detonating an item may alter these risks by generating shock waves, underwater noise or the dispersal of contaminated material.

The resulting risks are therefore highly site-specific. They depend not only on the munition itself, but also on its surroundings and on the people, ecosystems and activities that may be exposed to it. This interconnected character is central to understanding explosive-remnants-of-war risks as a wider system.

Acknowledgement: This article is under development.