Dumped chemical weapons missing at sea

23 March 2008
Magazine issue 2648

THE last thing you might expect to encounter exploring the ocean floor is a chemical weapon. But it seems hundreds of thousands of tonnes of them have been dumped into the sea, and no one knows exactly where the weapons are. Now, scientists are calling for weapons sites to be mapped for safety's sake.

Between 1946 and 1972, the US and other countries pitched 300,000 tonnes of chemical weapons over the sides of ships or scuttled them along with useless vessels, according to public reports by the Medea Committee, a group of scientists given access to intelligence data so they can advise the US government on environmental issues.

But the military have lost track of most of the weapons because of haphazard record keeping combined with imprecise navigation. Even the exact chemicals were not always noted, though there are records of shells, rockets and barrels containing sulphur mustard and nerve agents such as sarin.

The Chemical Weapons Convention does not cover the destruction of the sea-dumped weapons, which are considered abandoned. "There's no piece of legislation or treaty that deals with this stuff," says Peter Brewer, an ocean chemist at the Monterey Bay Aquarium Research Institute in Moss Landing, California. "It's in limbo."

If the chemicals leak from their containers, they will break down slowly in the cold seawater. But it is unclear what will happen if the chemicals bind to sediment or sink into anoxic zones, says Brewer (Environmental Science and Technology, vol 42, p 1394).

A team led by Roy Wilkens at the University of Hawaii in Manoa is planning to look for munitions dumped off the island of Oahu. Records only note that the weapons were dumped about "five miles south of Pearl Harbour". Finding them will involve a search of 60 square kilometres, says Wilkens.