NTI: Nuclear Threat Initiative Soman
Technical Description: Soman
The third military nerve agent developed by Germany in the 1930s, but never produced in any meaningful quantity, soman nerve agent was later classified by the US military and NATO with the designation GD, after the “German” series of nerve agents GA and GB. (There is no nerve agent with the GC classification, as this was already taken by the US military medical code for gonorrhea.) Soman is a colorless liquid and has been described having an odor of fruit or camphor. Although chemically it is not far removed from sarin, soman is relatively persistent with a lower volatility rating. Thus, soman was often referred to as an intermediate volatile agent. The toxicity of soman inhaled (vapor) is estimated (median lethal dose, or LD50) to be 50mg-min/m3, or 350mg through the skin. How soman got its name is still uncertain, but may derive from the Latin for “bludgeon” or the Greek for “sleep.”

A production scheme for soman would likely involve the reaction of difluor (difluoro methylphosphonate) and pinacolyl alcohol. Theoretically, a binary chemical weapon could be devised using these two components, although it is unknown what the reaction rate or yield would be in practice.

The toxic principle of soman is its ability to inhibit acetylcholinesterase (AChE), the body’s enzyme required for proper nerve transmission at the molecular level. Increased levels of acetylcholine produce exaggerated levels of bodily secretions and muscular twitching, as well as pronounced effects on the cardiovascular and central nervous systems. While death from respiratory paralysis can occur as a consequence, victims are also prone to asphyxiate due to mucous and salivary excretions from the upper respiratory tree. Without timely medical intervention and follow-up treatment, those who do survive exposure to large doses of nerve agents can suffer permanent neurological damage. Because of soman’s propensity to quickly “age” AChE, the soman-inhibited enzyme is particularly difficult to treat with oxime drugs, such as pralidoxime chloride (2-PAM-Cl).