4.1 This practice specifies an in-vivo measurement of CWA decontamination on the skin.

4.2 CWA skin decontaminants will have different modes of action including absorption, adsorption, removal, chemical neutralization or some combination of the above. There is, therefore, no single representative in-vitro method for validation of decontamination efficacy of products for skin decontamination. For example, measuring the presence of a radiolabelled chemical warfare agent after chemical neutralization, may give a false positive results. It has been shown that if the agent has been chemically neutralized, the radiolabel may still be present in a non-toxic molecule. In addition, some chemical neutralization methods may break down the original agent, but the breakdown product is highly toxic. In the case of VX, hydrolysis produces a highly toxic product, EA2192 (S-(2-diisopropylaminoethyl) methylphosphonothioic acid (8).

4.3 This standard practice is of significance in that efficacy is thoroughly evaluated to the extent possible to represent use on human skin. In-vivo studies have demonstrated that simple chemical monitoring for disappearance of the chemical agent may not be sufficient to measure decontamination and neutralization effectiveness. A standard practice is needed for determining actual decontamination and neutralization by measuring the decrease in mortality or lesion size caused by the agent.