Figure 5-1. Locations of Sulfur Mustard Stockpile and Non-stockpile Sites in the United Statesa

Sulfur mustard is a synthetic organic compound. It was first manufactured in 1822 by the action of ethene on sulfur monochloride or dichloride. Since then, the methods of manufacture have been refined, although they have not been changed substantially. Three main processes have been used. The Germans produced sulfur mustard using the Meyer process, which involved treating ethylene with hypochlorous acid followed by sodium sulfide, yielding β,β'-dihydroxy-methyl sulfide. This in turn was heated with hydrochloric acid, which produced sulfur mustard. In the United States, sulfur mustard was formerly made using the Levenstein process in which ethylene was reacted with sulphur monochloride at 30– 35 °C. Sulfur mustard produced by this process contains 62–64% distilled sulfur mustard (or HD) (Munro et al. 1999). This process produces a complex mixture that includes constituents that are more toxic than sulfur mustard itself (Rosenblatt et al. 1975). The most recent process used in the United States involved the formation of bis-(2-hydroxyethyl)-thioether from ethylene oxide and hydrogen sulfide; this was then reacted with hydrochloric acid to form sulfur mustard (Franke 1967; IARC 1975; Rosenblatt et al. 1975). Sulfur mustard produced by this process contains 89% HD (Munro et al. 1999).