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
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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