disposal program is also included. The chapter concludes with an outline of some of the conclusions drawn by the committee from analysis of the historical records and calculations of exposure levels.
Sulfur mustard (C4H8Cl2S) is one of a class of chemical warfare agents known as vesicants because of their ability to form vesicles, or blisters, on exposed skin (see Figure 3-1). During WWI, exposed troops described the odor of this agent as a stench like mustard or garlic, hence its common name. Table 3-1 summarizes some characteristics of mustard agents and Lewisite. First noted for its toxic properties by dye chemists in the late 1880s, sulfur mustard has been referred to by a number of synonyms: S-mustard, to distinguish it from nitrogen mustard; ''Lost" or "S-Lost," from the names of two chemists who suggested it be used as a war gas (Lommel and Steinkopf); "yellow cross," for the identifying mark on WWI shells containing sulfur mustard; or Yperite, after the site of its first use in 1917. Although commonly and inaccurately referred to as mustard gas, the agent is a liquid at room temperature.
Sulfur mustard produces skin blisters and damage to the eyes and respiratory tract, and it can be lethal at sufficiently high doses. It is a cellular poison and mutagen and a recognized human carcinogen. Battlefield use of sulfur mustard decreases the opponent's ability to fight by producing chemical burns on tissues that come into contact with either vapors or liquid droplets and aerosols. Exposed skin surfaces, eyes, and the linings of both the respiratory and the gastrointestinal tracts are all at risk, and the risks increase dramatically under hot, humid conditions.
From a military standpoint, one of sulfur mustard's most useful properties is its persistence. Droplets of this agent released in an explosion can deposit on numerous surfaces, evaporating slowly and posing a risk from inhalation as well as contact with the skin. Indeed, this very set of conditions was observed in WWI after mustard shelling (Haber, 1986). One reason for this persistence is the characteristic freezing temperature of sulfur mustard (13°C to 15°C). Droplets or bulk quantities would thus be expected to remain where initially deposited during cool or winter weather, under forest canopies, or under overgrown vegetation. Under certain conditions, bulk quantities of mustard agent spilled or splashed onto the soil would not degrade for months.
The exact date of the first sulfur mustard synthesis is somewhat unclear, but the first report may have been by Despretz in 1822. An 1860 report by Neimann describes a delayed-effect vesicant oil as a reaction product of ethylene on a mixture of sulfur chlorides. At that time, this