similar to sarin and other organophosphates, but it is a member of a different chemical class, the carbamates. Both PB and sarin exert their effects by binding to and inactivating the enzyme acetylcholinesterase (AChE).2 The binding of sarin to AChE is irreversible, whereas the binding of PB to AChE is reversible.

In March 1991, during the cease-fire period, troops from the U.S. 37th and 307th Engineering Battalions destroyed enemy munitions throughout the occupied areas of southern Iraq (PAC, 1996). One of the sites destroyed was a large storage complex at Khamisiyah, Iraq, consisting of more than 100 bunkers, which contained stacks of 122-mm rockets loaded with sarin and cyclosarin3 (Committee on Veterans’ Affairs, 1998). U.S. troops performing demolitions were unaware of the presence of nerve agents. In October 1991, inspectors from the United Nations Special Commission on Iraq (UNSCOM) first confirmed the presence of a mixture of sarin and cyclosarin (Committee on Veterans’ Affairs, 1998). At the time of the demolition, there were no medical reports by the U.S. Army Medical Corps of military personnel with signs and symptoms of acute exposure to sarin (PAC, 1996). Further, a 1997 survey mailed by the Department of Defense (DoD) to 20,000 troops within a 50-mile radius of Khamisiyah found that more than 99 percent of respondents (n = 7,400) reported no acute cholinergic effects (CIA–DoD, 1997). Nevertheless, low-level exposure could have occurred without producing acute cholinergic effects.

Conclusions on the Health Effects of Sarin

The committee reached the following conclusions after reviewing the literature on sarin. The committee was unable to formulate any conclusions about cyclosarin because of the paucity of toxicological and human studies.

The committee concludes that there is sufficient evidence of a causal relationship between exposure to sarin and a dose-dependent acute cholinergic syndrome that is evident seconds to hours subsequent to sarin exposure and resolves in days to months.

In humans, exposure to high doses of sarin produces a well-characterized acute cholinergic syndrome. This syndrome, as evidenced by acute cholinergic signs and symptoms, is evident seconds to hours after exposure and usually resolve in days to months. The syndrome is produced by sarin’s irreversible inhi-

2  

AChE is an enzyme necessary to remove acetylcholine (ACh). ACh transmits nerve signals at the cholinergic neuromuscular junction or synapses in the central nervous system. Anticholinesterase agents inhibit (inactivate) AChE, resulting in an accumulation of acetylcholine. The accumulation repetitively activates the ACh receptors, resulting in exaggerated responses of the organ (e.g., excess salivation).

3  

Cyclosarin is an organophosphate nerve agent. The committee examined the literature on this agent but found a very limited amount of information available on the health effects of this compound.



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