The fate of chemical weapons in seawater

Peter G. Brewer, Ph.D.
Monterey Bay Aquarium Research Institute

Wednesday, February 18, 1998
3:30 p.m.—Pacific Forum

Over 3,000 nautical miles of seafloor immediately to the west and north of Monterey Bay are designated on nautical charts as chemical weapons disposal areas. The quantity and type of material disposed of there is not well known, for incomplete records have been kept. Here I review the history of ocean disposal of chemical weapons, the mechanism of oceanic chemical attack on released material, and the nature and fate of the breakdown products. We may be glad that seawater is remarkably effective in de-naturing these loathsome molecules.

In the years before World War II, and continuing through the Cold War, ocean dumping of chemical weapons was a fairly common international practice. Many nations, including the United States and the USSR, used this method of disposal. This material today presents an environmental challenge as corrosion of the containers takes place and as exploration and use of the deep ocean expands. Chemical weapons threats, ranging from the Tokyo subway incident to the Gulf War and its aftermath, continue to plague society.

In the years immediately following the war, an estimated 50,000-150,000 metric tons of chemical weapons were dumped in the Baltic Sea at a shallow depth. Details of dumping in Japanese waters were not widely known until 1972 when a national inquiry was held. Ocean disposal continued until about 1970. Estimates of dumping at Russian Arctic sites have only recently become available, and about 140,000 tons of various chemical agents have probably been disposed of in the White, Barents, and Kara seas. The United States, Japan, and the USSR signed the London Convention prohibiting such disposal in 1972.

In the decades since then, some corrosion of the containers has occurred, and several hundred incidents involving Danish and Japanese fishermen have now taken place. United States domestic protocol under the CHASE program involved careful entombing of the weapons material in steel and concrete before ocean disposal.

The primary chemical weapons agents produced in industrial quantities are Mustard, Lewisite, Tabun, and Sarin, all of which have apparently been dumped in large quantities. Each compound is subject to breakdown and detoxification in seawater by hydrolytic attack once it is released from the primary container. The mechanism of attack, the primary breakdown products, and the approximate rate of hydrolysis are all known to some reasonable extent. While the toxicity of some chemical weapons agents is so high that widespread oceanic effects cannot be a priori excluded, the persistence of the primary materials in seawater is relatively short, and the environmental effects are very largely confined within the designated areas.

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