Sulfur mustard environmental conditions

Under environmental conditions, CWAs (vesicant agents, sulfur mustard (H, HD and HT) and lewisite (L) nerve agents, GA, GB, GD and VX) can undergo multiple-degradation processes such as hydrolysis, oxidation, dehydration and photolysis. These baseline degradation reactions can vary in rate and completeness, depending upon reaction temperature and pH, as well as the presence of free radicals and catalysts. Knowledge of these baseline reaction parameters has formed the basis for many modern decontamination procedures. 

Sulfur mustard can be considered environmentally persistent because it is chemically stable and of low volatility. When protected from weathering conditions, it may persist in soil for years. VX is moderately persistent because of low volatility and slow rate of hydrolysis. The G-agents can be considered non-persistent on the basis of volatility and hydrolysis rates. Depending on environmental conditions, their half-lives may be measured in hours to days. Lewisite is rapidly hydrolyzed but the insoluble oxide formed is stable in the environment. In addition, arsenical degradation products of lewisite persist in the environment. Because of its extreme volatility and relatively rapid hydrolysis, cyanogen chloride is not persistent in the environment. 

The agents that can be considered environmentally persistent, in varying degrees, are VX, sulfur mustard, and lewisite. Agent VX exhibits very low volatility and a slow rate of hydrolysis its half-life in soil may be measured in weeks to months, depending on environmental conditions. Sulfur mustard may persist... 

In a sulfur mustard vapor environment, unprotected military personnel will be exposed simultaneously via the respiratory and percutaneous routes. Such a combined exposure has not yet been studied, but it would be interesting to see which route would be predominant. Obviously, the environmental conditions will have a profound influence on the relative importance of the two exposure routes. 

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