The U. S. Army Reactive Topical Skin Protectant (rTSP): Challenges and Successes
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The U. S. Army Reactive Topical Skin Protectant (rTSP): Challenges and Successes +♦ Stephen T. Hobson∗, Erich K. Lehnert, and Ernest H. Braue Jr. Drug Assessment Division, U. S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA ABSTRACT In 1994, the U. S. Army initiated a research effort towards an effective material that acts both as a protective barrier and as an active destructive matrix against chemical warfare agents (CWA). We report results on our preparation and evaluation of Reactive Topical Skin Protectants (rTSP’s). These creams are composite materials consisting of a base material (TSP) and a reactive moiety. Using an established base of perfluorinated-polyether and perfluoropolyethylene solids we incorporated over 60 reactive components. Classes tested include organic polymers, organic/inorganic hybrid materials, polyoxometallates (POM's), enzymes, inorganic oxides, metal alloys and small molecules. We characterized these materials by light microscopy and FTIR. We determined the efficacy of these materials against both sulfur mustard (HD) and a representative nerve agent, soman (GD), using a penetration cell model coupled to a continuous air monitor and also by in vivo testing. Composite materials with optimum reactive compounds exhibit a 94% reduction of GD vapor break-through after 20 hours (from 9458 ng to 581 ng) and a 3.6 fold increase (from 162 min to 588 min) in the time 1000 ng of GD liquid penetrates through the material. Similar composite materials show a 99% reduction in HD vapor break-through after 20 hours (from 4040 ng to 16 ng), a 2.3 fold increase (from 524 min to >1200 min) in the time 1000 ng of HD vapor penetrates through the material, and an elimination of erythema versus control in an HD vapor challenge. These results indicate that an rTSP that protects against sulfur mustard and nerve agents is within reach. INTRODUCTION Chemical warfare agents (CWA’s) represent a real and growing threat both to U.S. Armed Forces as well as to civilians. Within the last three decades, chemical weapons have been used by the Soviets in Cambodia (yellow rain, tricothecene mycotoxins) [1], by Iraq against Iran (HD and tabun) [2], and by Iraq against its own dissident Kurdish population at Halabja (HD, HCN(g)) [3]. In the United States’ experience in World War I, almost one-third of hospitalized casualties were a result of CWA’s [4]. Furthermore, the 1995 use of sarin in a terrorist attack in Tokyo, Japan, which resulted in over 1000 casualties and 12 deaths [5], demonstrates that the civilian population has also become a target. The United States Army classifies CWA’s into seven categories [6]. However, in this paper we will focus only on protection against two classes: nerve agents (soman, GD) and blister agents (sulfur mustard, HD). Currently, protection against these agents in the United States Army consists of a chemically resistant outer layer of clothing (BDO) and protective mask (M40) [7]. This scheme of protection does allow continued operation in a
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