Soman decontamination

Immediate decontamination is required for the smallest drop. VX can be very rapid, and death can occur within fifteen minutes after absorption of a fatal dosage. Heavily splashed liquid persists for long periods under average weather conditions, and VX can persist for months in cold weather. For instance, VX is calculated to be approximately 1,500 times slower in evaporation than sarin (GB). As for LD-50 dose on the skin, sarin (GB) requires a dose of 1700 mg while VX requires only ten mg (tabun requires 1000 mg, soman requires 50 mg, and GF requires 30 mg). 

Parchment et al. (67) used a diamond ATR probe to monitor decontamination of mustard gas, sarin, soman, and VX. They conclude that because of relatively low sensitivity of the method, it can only be used for analysis of CWA in realistic concentrations in real time and in situ. 

Hobson, D., Blank, J., Menton, R. (1985). Comparison of effectiveness of 39 experimental decontamination systems and evaluation of the effect of three pretreatment materials against percutaneous application of soman, thickened soman, VX, and sulfur mustard to the rabbit. Aberdeen Proving Ground, MD. MREF Task 85-12. 

Though an ideal decontaminant may be difficult to attain, many alternatives exist that are readily available and meet many basic requirements, van Hooidonk et al. (1983) evaluated a variety of household products as decontaminants for VX, soman, and sulfur mustard. His paper provides an excellent comparison of these readily available decontaminants to include flour, soapy water, talcum powder, and tissue paper. We have selected several other candidate decontaminants that are under investigation, in advanced development, or currently fielded. These include the currently fielded U.S. Department of Defense skin decontaminants (M291 Skin Decontamination Kit [SDK], 0.5% hypochlorite, and 1% soapy water). Reactive Skin Decontaminant Lotion (RSDL), Diphoterine, Sandia Laboratory s Decontamination Foam, and the Decontamination Sponge. 

To date, the M291 SDK has not been used to decontaminate humans exposed to chemical agent. Extensive animal data suggest that the kit will provide significant protection to exposed soldiers. The resin itself was first tested for efficacy in rabbits with shaved backs that were exposed to soman, thickened soman, and VX. Two minutes after exposure, the animals were treated with the resin. The protective ratios were observed to be 2.0, 10.4, and 22.8, respectively (Joiner et al., 1988). 

In another study, clipped rabbits were exposed to sulfur mustard, lewisite (L), thickened soman, and VX and were decontaminated between 30 s and 5 min postexposure. Eor the vesicants (sulfur mustard and L), lesion areas were compared. Decontaminating for 1 min resulted in the lesion areas being reduced 21-fold for sulfur mustard and 22-fold for L, relative to no decontamination. For the nerve agents (soman and VX), the inhibition of blood acetylcholinesterase (AChE) was used as a marker. Using a 2 min decontamination time, the dose of nerve agent required to produce 50% inhibition of AChE was increased 1.8-fold for thickened soman and 18-fold for VX (Hobson et al., 1993). 

Recent studies in the clipped haired guinea pig model using 1% soapy water and a 2 min decontamination delay demonstrated protective ratios for soman, cyclosarin, VX, and VR of 2.2, 6.0, 16, and 27, respectively (Braue, 2006 Hanssen et al., 2006). 

Several decontaminants are readily available for CWA exposure. The trae measure of effectiveness requires that all products be tested identically, to include soapy water as van Hooidonk et al. (1983) did so well for common household products. The most comprehensive data available are the studies conducted at the USAMRICD (Braue, 2006 Hanssen et al., 2006) which directly compared the efficacy of M291 SDK, RSDL, 0.5% bleach, and 1% soapy water challenged with soman, cyclosarin, VX, and VR in the clipped haired guinea pig model. The most important guiding principle of decontamination is rapid removal of the threat agents from the skin. This principle supersedes seeking out sophisticated decontaminants immediately after CWA exposure. The immediate use of soapy water would offer far better results than the best possible decontaminant that was delayed more than 30 min in its use. Future evaluation of potential decontaminants should consider all of the discussed factors to determine the best product. 

Formulation is also used to manipulate the fate of the agent. Soman, VX, Lewisite, and sulfur mustard can be mixed with high-molecular-weight thickeners to increase droplet size and thereby decrease primary vaporization. Such additives are generally used to promote efficient agent deposition on the target site. Thickeners can also increase agent persistence and may hamper decontamination efforts. 

Three types of chemical mechanisms have been used for decontamination water/soap wash oxidation and acid/base hydrolysis.9 Mustard (HD) and the persistent nerve agent VX contain sulfur molecules that are readily subject to oxidation reactions. VX and the other nerve agents (tabun [GA], sarin [GB], soman [GD], and GF) contain phosphorus groups that can be hydrolyzed. Therefore, most chemical decontaminants are designed to oxidize mustard and VX and to hydrolyze nerve agents (VX and the G series).1 Water and Water/Soap Wash... 

Hobson D, Blank J, Menton R. Comparison of Effectiveness of 30 Experimental Decontamination Systems and Evaluation of the Effect of Three Pretreatment Materials Against Percutaneous Application of Soman, Thickened Soman, VX, and Sulfur Mustard to the Rabbit. Edgewood Area, Aberdeen Proving Ground, Md 1985. MREF Task 85-12 Final Report. 

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