In June, a clam boat happened upon some old military munitions off the coast of Long Island, New York. Mustard gas, released when the fishermen inadvertently hauled in the shells, blistered one crew member and reminded government officials, scientists and the public of the weapons arsenal that is buried deep below the surface of the world's oceans.
This arsenal includes ammunition, explosives and chemical weapons such as sulfur mustard (mustard gas), arsenic, cyanide, lewisite (a gas that blisters the skin and irritates the lungs) and sarin (now classified as a weapon of mass destruction by the United Nations).
The problem isn't going away anytime soon, experts say, because the dangers are hard to measure and because safe ways to remove and dispose of the weapons are lacking.
"Other than for research purposes, sea-disposed munitions are not really on anyone’s list," said J.C. King, an assistant for munitions and chemical matters in the Office of the Deputy Assistant Secretary of the Army for Environment, Safety & Occupational Health. "We are trying to understand the impact of munitions on the ocean and the ocean on munitions."
There are dump sites in waters around the world, according to a 2009 Annual Report to Congress from the Department of Defense Environmental Programs. In waters bordering the United States, including Hawaii and Alaska, tens of thousands of ammunition and explosives, as well as millions of pounds of chemical munitions lurk on the sea floor.
There are at least 5,400 tons of sulfur mustard in waters off the Atlantic coast and 9,100 tons off the Pacific coast.
The Department of Defense estimates that a total of 17,000 tons of sulfur mustard exist in United States waters, when the 2,300 tons buried off the coast of Hawaii and the 57 tons in Alaskan waters are included.
Quick-fix for surplus weapons
Although the number of dumped weapons may seem ludicrous in the environmentally conscious 21st century, it was considered the safest option for munitions disposal until 1970, according to a 2009 Department of Defense report.
The vastness of the ocean and its inaccessibility at certain depths seemed like the ideal trashcan for the volume of dangerous weapons left after two world wars. It was believed that seawater would dilute toxic chemicals, and that weapons deep underwater would be permanently unavailable to the hands of foreign powers.
With the passing of legislation like the Marine Protection, Research and Sanctuaries Act of 1972, sea-dumping of munitions ended (at least by the United States). But a long history of dumping — with spotty historical records — was left in its wake.
Looking deep to find answers
In 2007, the Department of Defense began to compile information about toxicity levels, amounts and locations of underwater munitions. But there are still many unknowns. Scientists don’t really understand how cold water temperatures and decades buried at sea affect chemical weapons.
According to a 2007 report written by David Bearden, an analyst for the Federation of American Scientists, seawater may transform sulfur mustard into a crusty gel that can last for years, and cold water may prolong its lifespan further. The result, albeit a rare event, is that a clam fisherman in New York waters may snag old munitions shells and get burned by mustard gas.
Scientists are beginning to study underwater munitions to determine whether they pose significant health and environmental risks. For example, a team of European and Russian researchers reported last month on a project to take samples in the Baltic Sea, where about 11,000 tons of toxic chemicals are under water.
After initial testing of seawater, sediment and marine life, they wrote in the journal Environmental Science & Technology "there are significant uncertainties."
At the University of Hawaii at Manoa, scientists are testing degradation of chemicals as part of the Hawaii Undersea Munitions and Material Assessment study. Although they are currently focusing on determining toxicity levels, the goals of their research include developing standard protocols for dealing with all aspects of munitions dumps, from locating them to cleaning them up.
Pinpointing the exact locations of munitions poses its own set of problems. According to the Department of Defense, most munitions are disposed at least 10 miles (16 kilometers) from coastlines and 300 feet (91 meters) deep; however, as analyst Bearden noted in his report, there are incomplete records of dump sites and "the possibility that ocean currents may have moved weapons [makes] the implementation of any response option difficult at best, if not impracticable in some cases."
Another challenge with no clear solution is how best to get rid of the munitions that are found to pose a threat.
"Underwater destruction is problematic," King told Life's Little Mysteries, "but to move recovered munitions to port for movement to another location for destruction, increases the risk to workers and public."
In other words, the seabed may remain peppered with tons of rockets, bombs and toxic containers for generations to come.
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This article was provided by Life's Little Mysteries, a sister site to LiveScience.