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5 Decontamination Decontamination is the process of removing or neutralizing chemical or biological agents so that they no longer pose a hazard. For military purposes, decontamination is undertaken to restore the combat effective- ness of equipment and personnel as rapidly as possible. Most current decontamination systems are labor and resource intensive, require exces- sive amounts of water, are corrosive and/or toxic, and are not considered environmentally safe. Current R&D is focused on developing decontami- nation systems that would overcome these limitations and effectively decontaminate a broad spectrum of CB agents from all surfaces and materials. R&D on decontamination has evolved over the years. Ideally, these efforts would result in the identification and deployment of a "universal" decontaminating system. However, this has not happened. During and after the 1950s, most decontamination involved aqueous-based systems or the nonaqueous Decontamination Solution Number 2 (DS2), both of which have weaknesses. Aqueous-based systems require large amounts of water (often not available on a battlefield) and are very inefficient at removing agent that has been adsorbed onto or absorbed into a painted surface. In addition, the contaminated water must be gotten rid of. DS2 is too corrosive for many applications. Ongoing attempts to develop dry systems (referred to euphemistically as "magic pixie dusts") that would be easy to transport and use, would not require large amounts of fluids, and could replace DS2 or aqueous systems, have not yet been successful. Based on the experiences of U.S. forces in the Gulf War and as a consequence of the breakup of the Soviet Union, the focus of the military 108

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DECONTAMINATION 109 has changed from defense against massive, large-area battlefield strikes against mobile forces to the defense of assets supporting force and power projection. Current U.S. military strategies are based on our ability to deploy forces rapidly to various theaters of operation (joint Chiefs of Staff, 1996; Secretary of Defense, 1999~. Fixed sites that are critical to the deployment of troops have now become attractive and vulnerable targets for CB attack, increasing the importance of protecting them or, if protection is impossible, improving our ability to restore contaminated sites and equipment to operational status. The focus of R&D has, therefore, been shifted from the decontami- nation of mobile forces to the decontamination of fixed sites. The key differences between decontamination of fixed sites and mobile forces are summarized in Table 5-1. The Joint Science and Technology Panel for CB Defense identified five functional areas where effective decontamination may be necessary in the event of a CB attack: (1) skin and personal equipment, (2) exterior equipment (field and fixed), (3) sensitive equipment, (4) interior equip- ment, and (5) large areas (land systems, seaport systems, ships at sea). Although these areas have some common needs, they also have significantly different vulnerabilities. Because the shortcomings of all cur- rent decontamination methods can be slightly mitigated but not elimi- nated through effective training, advances in technology will be neces- sary to increase the effectiveness of decontamination methods. The skin decontamination technologies currently used make person- nel more vulnerable to injury by increasing percutaneous absorption. It had been assumed that washing with either water or soap and water removes all contaminants. Experimental data, however, especially stud- ies on humans with agricultural chemicals, have demonstrated that this is TABLE 5-1 Differences between the Decontamination of Fixed Sites and Mobile Forces Fixed Sites Mobile Forces · Power and water resources are readily available. . Transportation is not a key factor. · Personnel operating in contaminated environments may be subject to prolonged exposure. · Many items and many different materials must be decontaminated. Resources are limited and must frequently be transported in. Assets must be transported. During decontamination, personnel are subject to limited exposures from contaminated equipment in a relatively "clean" environment. The number of items to be decontaminated is generally small.

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0 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES not true. First, washing with soap and water does not remove all of the chemicals. Second, at certain times, bathing actually increases systemic penetration into the body (Wester and Maibach, 1999a). Because the de- contamination of skin poses radically different challenges from the de- contamination of personal equipment, the subject is addressed as a sepa- rate issue in the next section. DECONTAMINATION OF SKIN Risks and Challenges The time between exposure of the skin and decontamination is criti- cal. Ideally, decontamination should be done within the first two minutes, before the agent penetrates the skin, because topical decontaminants are not effective for chemical agents that have penetrated the skin (Hurst, 1997~. However, decontamination after 15 minutes of exposure can still be of value although it may not be as effective. Washing with soap and water has always been assumed to remove chemical and biological materials from the skin. However, recent evi- dence suggests that penetration and systemic absorption/toxicity may actually be increased by washing (Wester and Maibach, l999b, l999c). Washing is also ineffective for decontaminating painted surfaces. Appen- dix D describes in vitro and in viva techniques for determining if skin has been decontaminated. Mustard and other organophosphates do not cause any sensation as they pass through the skin. The person may not even know which areas of skin are contaminated. Thus, an individual may become aware of expo- sure only after considerable damage has been done. Because the speed of decontamination is critical, an indicator of exposure would be very use- ful. In fact, the rapidity of contamination removal is more important than the type of decontaminant. The following problems are common to current and potential decontaminants: irritation of the skin, toxicity, ineffectiveness, and high cost. R&D to develop a skin decontaminant with the following traits is continuing (Chang, 1984; Hurst, 1997~: · capability of neutralizing chemical and biological agents · safety (i.e., nontoxic and noncorrosive) · easy application by hand · ready availability · rapid action · no production of toxic end products

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DECONTAMINATION · stability in long-term storage · short-term stability (i.e., after issue to the unit/individual) · affordability · no enhancement of percutaneous agent absorption · nonirritating · hypoallergenic · easy disposal · safe to the eyes 111 Technologies In the 1970s, the U.S. Army developed the M258 skin decontamina- tion kit, which was modeled on a Soviet kit recovered from Egyptian tanks during the Yom Kippur War. This kit consisted of two packets, one containing a towelette prewetted with phenol, ethanol, sodium hydrox- ide, ammonia, and water; and one containing a towelette impregnated with chloramine-B and a sealed glass ampoule filled with zinc chloride solution. The ampoule was broken and the towelette wetted with the solution immediately prior to use. Zinc chloride was used to maintain the pH of water between 5 and 6 in the presence of the chloramine-B, which would otherwise raise the pH to 9.5 (Leslie et al., 1991~. The M291 kit, a solid sorbant system for wiping bulk liquid agent from the skin, was adopted in 1989 and is currently in use (Yang et al., 1992; Yang, 1995~. This kit is composed of nonwoven fiber pads filled with a resin mixture (trade name XE-555) developed by Rohm & Haas Company (Kerch, 1998~. The resin is composed of an absorptive resin based on styrene/divinylbenzene, a high surface area carbonized macroreticular styrene/divinylbenzene resin, cation-exchange sites (sul- fonic acid groups), and anion-exchange sites (tetraalkylammonium hy- droxide groups) (Yang et al., 1992; Yang, 1995~. The absorptive resin can absorb liquid agents, and the reactive resins promote hydrolysis reac- tions; however, in a recent study using nuclear magnetic resonance (NMR), neither VX nor a mustard simulant was hydrolyzed on the XE- 555 resin surface during the first 10 days (Leslie et al., 1991~. GD was slowly hydrolyzed with a half-life of about 30 hours. The effectiveness of the M291 kit depends primarily on the physical removal of the agent by wiping. The resin blend in the M291 kit was found to be less corrosive to the skin than the liquid in the M258 system. Another decontamination kit, the M295, contains the same resin as the M291 and may be used to decontaminate personal equipment but not the skin. At present, the most universal chemical agent decontamination methods continue to be washing with water or water and soap, oxidation,

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2 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES and acid/alkaline hydrolysis (fresh 0.5 percent hypochlorite solution at an alkaline pH) (All et al., 1997; U.S. Army Medical Research Institute of Infectious Disease, 1998~. Because several biological agents pose a percutaneous threat to a con- taminated individual, respiratory protection alone may not provide ad- equate protection, although in most instances respiratory protection will be sufficient for short-term protection, provided decontamination of the skin is initiated relatively quickly (Johnson, 1990; LeDuc, 1989; Mikolich and Boyce, 1990~. The 0.5 percent hypochlorite solution, which has been used since World War I, is currently recommended for decontamination of all bio- logical agents (All et al., 1997~. However, it cannot be used in abdominal wounds, open chest wounds, on nervous tissue, or in the eye. Reactive Skin Decontaminant Lotion (RSDL), which was developed in Canada and is believed to contain phenoxides, oximates, a solvent (such as tetraglyme), and a thickener, is said to be effective for a number of chemical agents and some biological agents (Barnard et al., 1991~. The U.S. Army Medical Research Institute of Chemical Defense (USAMRICD) is developing a barrier cream based on perfluorocarbon formulations (Braue, 1998~. The cream will be applied in a 0.15-mm thick layer and is expected to provide protection for six hours (four hours mini- mum) against liquid agents, including HD, lewisite, GD, and VX. The cream would lessen the need for immediate skin decontamination after exposure. The requirements for the cream include: no interference with other antidotes or pretreatments, no increase in vulnerability to detection, a minimum shelf life of three years, and catalytic reactivity. The extreme thickness of the cream layer is a serious limitation, however, because it interferes with the normal functioning of the skin. Stoichiometric reagents in the cream would not be expected to decon- taminate a significant quantity of agent. Therefore, attempts are being made to include reactive constituents in the formulation. Some reactive species under development are polyoxometalates, cross-linked enzyme crystals: organophosphorous hydrolase (OPH) and organophosphorous acid anhydrolase (OPAA), nanoscale metal oxides (magnesium oxide [MgO], calcium oxide [CaO], titanium oxide [TiO2], manganese oxide [MnO2~), polymer-coated metal alloys (titanium-iron-manganese, manganese-nickel, calcium-nickel), potassium persulfate (K2S 208 ), zero valence metals (iron/palladium, zinc/palladium), 2,3-butanedione monoxime (present in the Canadian RSDL), thermophylic bacterial enzymes, and benzoyl peroxide (Braue, 1998~.

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DECONTAMINATION DECONTAMINATION OF EQUIPMENT, FACILITIES, AND LARGE AREAS Risks and Challenges 113 The decontamination of equipment is complicated because different types of equipment must be decontaminated by different means. For ex- ample, personal equipment (e.g., rifles, tools, and other gear) must be decontaminated by a different process than sensitive equipment (e.g., communications equipment, navigational equipment, computers, and avionics), which, almost by definition, cannot be exposed to aqueous decontaminants or strong oxidizing or caustic solutions. Interior equipment (e.g., the interior of vehicles, aircraft, and shelters) have unique requirements because personnel are likely to operate in these confined areas with reduced protection. Exterior equipment and large areas, in- cluding pre-existing facilities, land and sea systems (e.g., roadbeds, air- fields, buildings, seaports, and cargo loading docks), operationally fixed sites (e.g., command and control facilities and maintenance facilities), and transportable support structures (e.g., supply depots, medical facilities, and communications and intelligence collection facilities) have extensive surface areas that must be decontaminated. In addition, decontamination equipment for use in buildings must fit in a conventional elevator. Technologies Self-Decontaminating Materials and Protective Equipment Self-decontaminating coatings, which could facilitate the rapid reuse of contaminated equipment, could be formulated with components ca- pable of catalyzing the conventional hydrolysis and oxidation reactions of agents (Albizo et al., 1988; Medema et al., 1987~. Examples include nanoclusters of semiconductors, zero-valent metals, functionalized poly- mers, and polyoxymetalates in polymers (Tadros, 1999~. Other areas be- ing researched include using solar radiation to activate decontaminating compounds and discarding contaminants by using strippable coatings. Although several options are in development, none of these techniques is ready to be used in the field. Some applications are summarized in Table 5-2. Natural Decontamination (Water, Steam) Probably the first (and most versatile) decontamination method is washing or spraying with water, water plus soap or detergent, or steam.

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4 STRATEGES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES TABLE 5-2 Decontamination Coatings Applicable Production Coating Agents State Description Chemical agent-resistant coating (CARC) all Sacrificial not specified coatings Self decontaminat ing coatings available in development not specified in development CARCs are polyurethane- based coatings designed to be chemically resistant to both chemical agents and decontaminants. When a chemical agent is deposited on the surface of a CARC coating, the surface repels the agent causing it to form droplets. The agent is then removed or decontaminated. Sacrificial coatings quickly absorb deposited chemical agents to reduce vapor hazards. Once the agent is absorbed into the sacrificial coating, the contaminated coating can either release itself from an uncon- taminated substrate or it can be stripped off using relatively mild decon- taminants, such as soapy water. Self-decontaminating coatings absorb deposited chemical agents to reduce vapor hazards. Once the agent is absorbed into the coating, active decontaminating agents can degrade or neutralize the agent. Sources: Friel and Graham, 1989; Nene et al., 1988; Stevens and Henderson, 1987. A serious drawback to this method is that, although most contaminants are removed and diluted, not all of them are neutralized or destroyed. To neutralize or destroy CB agents, bleach or other chemical reagents must be added; but the large volume of fluid used can cause logistics chal- lenges, and contaminated runoff may cause environmental problems and require subsequent treatment.

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DECONTAMINATION Weathering (Natural Attenuation) 115 "Weathering" is a mode of decontamination in which natural sources of heat and ultraviolet radiation (sunlight), water (precipitation), and wind (evaporation and dilution) degrade contaminants on equipment, structures, and terrain. The effectiveness of weathering as a decontamina- tion process depends on the persistence of the agent, as well as on me- teorological and surface conditions. Some conditions that are favorable for decontamination by weathering (high wind or high temperature) can also spread contamination by resuspending contaminated particles or liq- uids in air or by volatilizing agents at high temperatures with no wind (producing a vapor hazard). Ordinarily, thickened agents are not effec- tively removed by weathering. Standard Decontaminants (Bleach, Decontaminating Solutions) In the 1950s, supertropical bleach (a mixture of 93 percent calcium hypochlorite and 7 percent sodium hydroxide) was standardized for use as a decontaminant because it is more stable in long-term storage and easier to spread than bleaching powder. Bleach reacts with mustard gas by oxidation of the sulfide to sulfoxide and sulfone and by dehydrochlo- rination to form nontoxic compounds, such as O2S(CHCH2~2 (Price and Bullitt, 1943~. The G-agents are converted by hydrolysis to the correspond- ing phosphoric acids because the hypochlorite anion behaves as a cata- lyst (Epstein et al., 1956~. In acidic solution, VX is oxidized rapidly by bleach at the sulfur bond and dissolves by profanation at the nitrogen bond. At high pH values, however, the solubility of VX is significantly reduced, and the deprotonated nitrogen is oxidized leading to the con- sumption of greater than stoichiometric amounts of bleach (Yang et al., 1992; Yang, 1995~. At high concentrations of about 5 percent, bleach has been shown to kill bacterial spores (Bloomfield and Arther, 1992; Sagripanti and Bonifacino, 1996; Williams and Russell, 1991~. DS2, introduced in 1960, is a nonaqueous liquid composed of 70 per- cent diethylenetriamine, 28 percent ethylene glycol monomethyl ether, and 2 percent sodium hydroxide (Beaudry et al., 1990; Richardson, 1972~. The reactive component is the conjugate base CH3OCH2CH2O-. Although DS2 is a highly effective decontaminant for chemical agents, ethylene glycol monomethyl ether showed teratogenicity in mice, so replacement with propylene glycol monomethyl ether (DS2P) has been proposed (Talamo et al., 1994~. DS2 attacks paints, plastics, and leather materials so contact time is limited to 30 minutes followed by rinsing with large amounts of water. Personnel handling DS2 are required to wear respira- tors with eye shields and chemically protective gloves. The reactions of

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6 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES DS2 with mustard lead to elimination of hydrogen chloride. Nerve agents react with DS2 to form diesters, which further decompose to the corre- sponding phosphoric acids. DS2 is not very effective in killing spores. Only 1-log kill was observed for Bacillus subtilis after one hour of treat- ment (Tucker, 1998~. German C8, a microemulsion system developed in Germany, consists of 76 percent water, 15 percent tetrachloroethylene, 8 percent calcium hypochlorite, and 1 percent anionic surfactant mix (Ford and Newton, 1989~. German C8 enhances the solubility of agents but contains chlori- nated hydrocarbons that are environmentally persistent. It may also pro- duce toxic by-products, such as vinyl chloride (a carcinogen). Standard decontaminants are effective not only for chemical agents but also for most biological agents. Pathogens that form spores may be considered a special case because bacterial spores are highly resistant structures formed by certain gram-positive bacteria usually in response to stresses in their environment. The most important spore-formers are mem- bers of the Bacillus and Clostridium genera. Spores are considerably more complex than vegetative cells. The outer surface of a spore is the spore coat, typically a dense layer of insoluble proteins containing a large num- ber of disulfide bonds. The cortex consists of peptidoglycan, a polymer primarily made up of highly cross-linked N-acetylglucosamine and N-acetylmuramic acid. The spore core contains normal (vegetative) cell structures, such as ribosomes and a nucleoid. Many bacterial pathogens, some of which are biological warfare agents (e.g., Bacillus anthracis), protect themselves from hostile environ- ments by forming spores. Considerable research has been carried out to investigate methods of killing or inactivating bacterial spores. Although spores are highly resistant to many common physical and chemical agents, a few antibacterial agents are also sporicidal. Because many powerful bactericides may only be inhibitory to spore germination or outgrowth (i.e., sporistatic) rather than sporicidal, they may postpone rather than eliminate a biological warfare threat (Tadros, 1999~. Examples of spori- cidal reagents (in high concentrations) are glutaraldehyde, formaldehyde, iodine and chlorine oxyacids, peroxy acids, and ethylene oxide. In gen- eral, these reagents are toxic and, therefore, of limited use for decontami- nating personnel. Nonstandard Decontaminants (Caustic Soda, Solvents) The SBCCOM Edgewood Chemical Biological Center has developed a microemulsion system called the multipurpose chemical biological decontaminant. It consists of tetrachloroethylene, water, a high concen- tration of cationic surfactant, a cosurfactant (tetrabutyl ammonium

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DECONTAMINATION 117 hydroxide), Fichlor reagent (sodium dichloroisocyanurate), a hydrolysis catalyst (sodium 2-nitro-4-iodoxybenzoate [IBX]), and sodium borate (Walther and Thompson, 1988~. The multipurpose decontaminant is more stable than the German C8 emulsion. Fichlor reagent acts by producing hypochlorous acid upon interaction with water. Another product designed to eliminate the use of chlorinated solvent, called decontamination agent multipurpose (DAM), contains N-cyclohexyl-2-pyrolidone, calcium hypochlorite, and a surfactant mix- ture. Although multipurpose decontaminants look promising, none has been accepted as a completely effective substitute for DS2 (see the exten- sive bibliography in Day, 1996~. Trichlorotrifluoroethane FC-113 is electrically nonconductive, com- patible with electronic components, and is currently used as a cleaning solvent. These properties suggested that it might be used to decontami- nate military equipment. An exploratory Army study of FC-113 resulted in the development of a nonaqueous decontamination system that can be used for sensitive electronic equipment (e.g., night-vision goggles and communication equipment) (Richmond et al., 1990~. Reactions and Mechanisms Reactions involved in detoxification of chemical agents may be di- vided into substitution and oxidation reactions. Substitution Reactions The rate of hydrolysis] of mustard and the nature of the products formed depends on the solubility of mustard in water and on the pH of the water. Mustard forms a cyclic sulfonium cation that reacts with nucleophilic reagents (Mikolajczyk, 1989; Yang et al., 1992; Yang, 1995~. The dominant product is thiodiglycol, which may react with sulfonium ions to produce the secondary intermediates HD-TDG and CH-TDG (Figure 5-1~. The hydrolysis of sarin (GB) and soman (GD) occurs rapidly under alkaline conditions and produces the corresponding O-alkyl methyl- phosphonic acid. In contrast, the hydrolysis of VX with OH- ions is more complex. In addition to displacement of the thioalkyl group, the O-ethyl group is displaced producing a toxic product known as EA-2192 (Yang et al., 1992, 1997; Yang, 1995~. 1Hydrolysis is a chemical reaction in which a substance reacts with water, hydroxyl ions, or other nucleophiles and becomes a different substance.

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8 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES /CH2CH2S(CH2 CH2OH)2 So -CH2CH2CI HD-TDG ,CH2CH2S(CH2 CH2oH)2 So CH2CH2OH CH-TDG FIGURE 5-1 Secondary products formed by hydrolysis of sulfur mustard. Nucleophilic substitution at phosphorous centers involves addition to form a trigonal bipyramidal intermediate. Nucleophiles enter and de- part the intermediate from an apical position. Electronegative groups, such as RO groups, preferentially occupy apical positions; groups that are bulky or -electron donors, such as RS groups, occupy equatorial posi- tions. If the lifetime of the TBP allows pseudorotation to occur, the final product will depend on the balance between apicophilicity and the ten- dency for the leaving group to disengage. The result is that P-S bond cleavage is favored over P-O bond cleavage by a factor of about five. Peroxyhydrolysis, however, using OOH- ions in alkaline medium was shown to involve quantitative P-S cleavage at rates 30~0 times the rate with OH-. This selectivity was related to the relative base alkaline of the anionic nucleophile and the leaving anions (Yang et al., 1997~. Catalytic species (e.g., iodosobenzoate) have been used to accelerate substitution reactions. An example of the catalytic reactions of iodoso- benzoate is shown in Figure 5-2 (Moss et al., 1983; Moss and Zhang, 1993~. The compound was also functionalized to introduce surface activity and surfactant character to the active groups (Moss et al., 1986~. Metal ion- amine complexes, with a surface active moiety, were also developed and shown to exhibit catalytic effects in substitution reactions (Courtney et al., o O2 N `~4 ll o o o 11 / P' IP'o_: ~ l\ -Hi O2 N j~OH off To o ~0 // O-P~ ~ /+OH O O 11 / o' IP'o_\ FIGURE 5-2 Catalytic acceleration of soman by iodobenzoate.

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DECONTAMINATION P-O cleavage product \ 0.1 M NaOH - ~ I . 1 1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1 55 50 45 40 35 30 25 20 15 10 ppm Decontamination in 0.1 M NaOH P-S and P-O cleavage 127 Starting material ~ / me' P-S cleavage product pH - 2.2 29min 21 min \ 1 14 min \ ~ - | 4min 1 1. ,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,,1,,,, 1,,,,1,,,, 1,,,,1,,,,1,,,,1 55 50 45 40 35 30 25 20 15 10 5 0 ppm Foam decontamination P-S cleavage FIGURE 5-6 UP NMR study of the decontamination of O-ethyl-S-ethyl phenyl phosphonothioate. silica particles, which can efficiently catalyze the hydrolysis of P bonds in G agents. The gel is thixotropic in nature, and the viscosity can be varied allowing the material to "stick." The gel has been tested on a variety of different materials using surrogates, and testing with actual agents is under way (Raber et al., 1998~. The material residue has been shown to be environmentally acceptable. The gel is sprayed on, allowed to dry, and then vacuumed up. The gel can attach to vertical and inverse surfaces. In a test with concrete and asphalt contaminated with VX and GD, an analysis after treatment showed that more than 97 percent of the cholinesterase-inhibiting capa- bility had been destroyed. When HD was tested, residual activity was reduced to nondetectable levels. Some tests have been less successful, however. For example, GD was effectively removed from carpet but was less effectively removed from painted surfaces. The gel has also been tested against BG spores and found to reduce the number of spores by "6 logs" (i.e., no spores were detected after treatment). Tri-n-butyl Phosphate (BCTP) Emulsion. Researchers at the University of Michigan and Novavax, Inc., have developed an antimicrobial emulsion with low toxicity consisting of soybean oil, Triton X-100, water, and a solvent (tri-n-butyl phosphate, known as BCTP). This material was shown to kill anthrax spores both in a culture dish and in mice exposed to an- thrax through a skin incision. The authors claim that BCTP causes the spores to revert to an active bacterial state. In four to five hours, the spore

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28 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES In a C' a 103 / / . / 10-5 H CO3-/H2O2 in water H CO3-/H2O2 in foam FIGURE 5-7 Foam decontamination of Bacillus subtilis spores after one hour of treatment. Demonstration of synergistic effects of the mild oxidant and the foam. Outer membrane changes, allowing the solvent to strip away the exterior membrane. The detergent then degrades the spore interior. A "l-log" kill (i.e., reduction in activity by a factor of 10) was reported during this time period (Renter, 1998~. Gaseous Decontamination Gases. Gas-phase reagents would be attractive for decontamination if the decontaminating gas is environmentally acceptable. The advantage of gas decontamination is that gases can penetrate (diffuse) and could be used to complement other decontamination techniques. Ozone, chlorine dioxide, ethylene oxide, and paraformaldehyde have all been investigated as decontaminants. All of these are known to be effective against bio- logical agents. Reports by SBCCOM have shown that ozone is not effec- tive as a decontaminant for GD (Bartram et al., 1998~. Ozonic decontami- nation of VX leads to cleavage of the P-O bond and the formation of toxic products (Bartram et al., 1998~. However, the effectiveness of ozone for

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DECONTAMINATION 129 killing spores in a high-humidity environment has been well established (Currier, 1999~. Vapor of hydrogen peroxide (VHP) is now used commercially for sterilization, and the sporicidal effects of VHP have been reported. A significant advantage of VHP is that it breaks down through a simple catalytic process into water vapor and oxygen, eliminating the emission of any dangerous by-products. Sandia National Laboratories is consider- ing the development of a mixture of hydrogen peroxide (H2O2), carbon dioxide (CO2), and water vapors to produce the active species hydro- peroxycarbonate in situ. Reactive Plasma. Los Alamos National Laboratories has developed an at- mospheric-pressure plasma source to generate chemically reactive efflu- ent for neutralizing chemical and biological agents (Selwyn and Currier, 1999~. This approach is "dry," requires no subsequent cleanup or waste disposal, and can potentially decontaminate surfaces and equipment. The system could be modified to produce reactive metastables and/or radicals that may kill bacteria and viruses used as biological agents and might also be used to neutralize chemical agents. The method is based on the development of a small electrical dis- charge in the space between two opposing insulated flat-plate electrodes connected to a high-voltage source at alternating radio frequencies. A large number of short-lived but high instantaneous current micro- discharges are uniformly distributed over the discharge space. Energetic electrons are produced that lead to the creation of free radicals in the gas flowing between the electrodes. Because of the short duration of the microdischarges and low ion mobilities, the electrical energy is primarily coupled into electron channels so that the electrons, ions, and gas mol- ecules do not equilibrate. Thus, the electrons are "hot," and the other species are "cold." This results in a very efficient transfer of electrical energy to electronic excitation of molecules and chemical processes at essentially ambient temperatures and pressures. One could actually ex- pose skin or other heat-sensitive surfaces to such plasmas without being burned. Innovatek, Inc., is commercializing a hand-held, low-power, corona discharge plasma flare that operates at atmospheric pressure and low temperatures for surface sterilization (Irving, 1998~. In laboratory testing, the device demonstrated high-efficiency destruction of Bacillus subtilis and DMMP. Reactive plasma units might also be used to monitor chemical agents. By analyzing the absorption bands in the plasma discharge, the presence of chemical agents can be detected. Thus, this technique has the potential of providing simultaneous decontamination and detection.

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130 include: STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES Technology in this area is developing rapidly. Current innovations · plasma/peroxide systems for the decontamination of biological warfare agents · plasma "blankets" that run at 30W and can be wrapped around small objects, such as a rifle · plasma air purifiers that could augment or replace conventional filters There may be problems with scale (i.e., producing enough plasma to cover a large area), but for decontamination or sterilization of delicate surfaces on objects the size of soldiers, electronics, or optics, these tech- niques are exciting. Because of their speed, low power requirements, and lack of residual products, this technology may be the method of choice for the decontamination of sensitive surfaces. Supercritical Fluids. SBCCOM has initiated a program to extract chemical agents from contaminated sensitive equipment using supercritical carbon dioxide (joint Science and Technology Panel for CB Defense, 1999~. Supercritical fluids exhibit very high mass-transfer rates because of their liquid-like density, gas-like viscosity, and negligible surface tension. Car- bon dioxide was selected because it is nontoxic, nonflammable, inexpen- sive, has a low supercritical temperature (31°C), and has high compress- ibility. In addition, no water, heat, or radiation (which could affect sensitive equipment) would be required. A combination of extraction and simultaneous decontamination with reagents soluble in carbon dioxide has also been considered. Problems that must be solved before this technology could be used include the placement of equipment into reactor vessels and the need to transport and handle tanks of liquid carbon dioxide. Radiation, Pressure, and other Techniques Ultraviolet Activated Oxidation Systems. The photolysis of hydrogen perox- ide, ozone, and other oxidants by ultraviolet radiation generates highly reactive intermediates, such as hydroxyl radicals, that can then degrade agents (Bolton and Stevens, 1995~. These processes are called advanced oxidation processes. Ferrioxalate anions were found to absorb both in the ultraviolet and near-visible region at 500 rim yielding hydroxyl radicals. This method has the potential of using solar light as the energy source. Ionizing Radiation. Ionizing radiation can include x-rays, gamma rays, high-intensity ultraviolet rays, and electron beams. Experimental

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DECONTAMINATION 131 measurements, presented as DO values (i.e., the dose level required to reduce the sample population by a factor of 10), have been made of the effects of radiation on spores and bacteria. Typical DO values for a num- ber of spores and bacteria are 100-300 Krad (Ito et al., 1993~. A minimum of Ado is required, and a level of Ado is considered a sterilization level. Thus, the dose required for typical spore agents ranges from 1 to 3 Mrad. Limited data are available on the effects of radiation on chemical agents and biological toxins. The DO values for other organic molecules range from 0.3 to 5.0 Mrad (Gray and Hilarides, 1995; Turman et al., 1998~. An interesting application of radiation for decontamination would involve the use of electron beams (McKnight et al., 1999~. The main com- ponents of the system would include some type of electron "gun," an accelerator, a power conditioning and control system, and shielding. In the field, shielding could be provided by soil so that bulky shielding material would not have to be transported. Large objects and runoff wa- ter are potential decontamination targets for electron beams. Ionizing radiation is routinely recommended for the sterilization of prepackaged medical devices, and a 2,500-rad dose is generally effective for sterilization. Microorganisms are inactivated by the radiation that attacks water molecules within the organism creating intermediate hy- drolysis products that result in complete inactivation. Because the radia- tion dose can be calculated with great reliability, the process is highly predictable. The high penetration range of ionizing radiation (i.e., ability to pen- etrate beyond walls, cracks, ducting, etc.) makes it suitable for the decon- tamination of large areas, such as fixed sites. The major hazards associ- ated with this technology are high voltage and radiation, both of which can be potentially mitigated. No residual waste or radioactivity is left behind after treatment provided that the energy of the exciting beam does not exceed about 10 million electron volts (MeV) (Battelle Memorial Insti- tute and Charles Williams, Inc., 1999~. Several applications for decontamination by ionizing radiation have been considered (Irving et al., 1997~. High-energy radiation could provide a method for destroying agent while it is still inside a bomb-type canister, which would be an effective way of dealing with terrorist threats of most biological agents and some chemical agents. Radiation might also be used to decontaminate large areas, such as airstrips, highways, and seaports. The kill rate increases logarithmically with time, so the percentages of decontamination would increase as the time of irradiation increased. Operationalizing radiation methods will require the detection of chemical warfare missiles and the availability of compact beam accelera- tors. Several accelerator technologies could be used (Turman et al., 1998~; and several low-power options are already commercially available. The

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32 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES Titan Beta Linac produces a beam of 10 MeV at a maximum power of 15 kW; the beam can be extracted through a thin metal foil for propaga- tion through the atmosphere for a short range. The beam is scanned in one dimension over a distance of about 100 cm at the exit window. A similar system has been fielded on a truck bed for mine detection applica- tions (Figure 5-8~. Other systems are the Canadian AECL (radio-frequency accelerator with 9.5 MeV 50kW beam output) and the Belgium Rhodatron accelerator (10 MeV, 150 kW). High-current, high-power beams can be produced with linear inductive voltage-adder accelerators, such as the RHEPP II accelerator at Sandia National Laboratories that produces a 2.5 MeV, 20 kA, 3 K! pulsed beam. This technology has the potential to produce beam power with an average of 300 kW at a repetitive rate of 100Hz. With some miniaturization of the superconducting elements, con- ventional radio-frequency accelerators could fit on a truck bed. Feasibility studies are being conducted at Sandia National Laborato- ries to validate the concept that electromagnetically induced alteration of tertiary molecular structure is sufficient to deactivate biological agents. The wavelength will be selected based on absorption characteristics of the agents in the microwave region. The system would be fast and energy efficient and could be used on the surfaces of sensitive equipment (Tadros, 1999~. CURRENT DOCTRINE AND TRAINING Army Field Manual (FM) 3-5/Fleet Marine Force Manual 11-10 (U.S. Army and U.S. Marine Corps, 1993) provides detailed guidelines for FIGURE 5-8 (a) High-energy accelerator fitted on a truck. (b) Large-area decon- tamination with ionizing radiation.

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DECONTAMINATION 133 decontamination operations. One of the basic messages of this doctrine is that decontamination is costly in terms of manpower, time, space, and materiel; the same resources required to fight the battle. Therefore, commanders must use them wisely to sustain combat op- erations. To limit the spread of contamination, commanders are advised to decontaminate equipment and personnel as soon and as far forward as possible, decontaminating only as much equipment and as many person- nel as necessary. Commanders are also advised to decontaminate chemi- cal agents first because decontamination methods for chemical agents are also believed to be effective for neutralizing or removing biological con- tamination, but not vice versa. Decontamination is only briefly mentioned in Joint Doctrine for Nuclear, Biological and Chemical Defense (joint Chiefs of Staff, 1995~. This document does not include detailed operational guidelines but does iter- ate the concepts spelled out in FM 3-5/FMFM 11-10 (U.S. Army and U.S. Marine Corps, 1993~. It also suggests that, depending on the CB agent, decontamination may not be necessary because of natural weathering effects. Natural decontamination by weathering, ultraviolet, and thermal processes has been effectively used as a basis for Air Force procedures for spot decontamination in selected areas. Army doctrine related to training in decontamination states that all individuals will be trained in basic decontamination skills using indi- vidual and unit decontamination equipment and that leaders will ensure that their units are proficient in decontamination procedures (U.S. Army and U.S. Marine Corps, 1993~. Joint doctrine does not specifically mention training in decontamination (joint Chiefs of Staff, 1995) except that each service will incorporate NBC defense training into its overall training plan for units and individuals. The degree to which training is effective and/or being provided is not known because DoD does not have a mecha- nism for assessing the status of training (DoD, 1999~. The shift in military strategy in the 1980s to dependence on force projection capabilities has resulted in profound changes in attitude to- ward decontamination. Several areas of potential vulnerability were iden- tified in a computer simulation (called CB 2010) of a covert CB attack on forces during the process of deployment from the continental United States (CONUS) to the Middle East (Booz-Allen and Hamilton, 1997~. The simulation showed that CONUS ports of embarkation were vul- nerable and that CB attacks could delay deployment and degrade the effectiveness of fighting forces. In this scenario, the mission was seriously compromised, and some military objectives were not achieved. The pur- pose of the CB attack was not necessarily to kill, but to disrupt and delay deployment.

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34 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES In a more recent deployment exercise at Pope Air Force Base and Fort Bragg, the computer scenario was incorporated into a war game (Raines, 1999~. In a covert CB attack, simulated thickened mustard was dropped from two crop-duster aircraft. The attack targeted key deployment areas and mission-critical assets. The following lessons were learned: · The attack successfully delayed and disrupted deployment. The delay, which was longer than one day, was significantly longer than was predicted by CB 2010. · No DoD guidelines address CB threats against military operations in CONUS. · No monitoring capability or chemical protective equipment was available for the deploying troops because their gear had been packed for transport. · Post-attack detection and decontamination facilities and equipment were also packed, which delayed decontamination. . . No decontamination standards were available for certifying that contaminated equipment could be returned to operational status. Nondeploying (or nonmobility) personnel did not have equipment and had not been trained in CB defense. · The medical facilities were overwhelmed by the casualties and were not prepared to treat contaminated personnel. This exercise clearly identified discontinuities between doctrine and training. At the very least, facilities and equipment that are critical to a force deployment mission should be identified and appropriate plans developed to protect and/or decontaminate critical assets. Guidelines for responding to a CB attack in CONUS are clearly necessary. The relationship between doctrine (or guidance) and risk with respect to decontamination is complicated, especially because the risk has not been quantified. USACHPPM has drafted Short-Term Chemical Exposure Guidelinesfor Deployed Personnel, which provides exposure guidelines that could be used "as criteria to identify potential risks that should be consid- ered in deployment mission decision-making and overall risk manage- ment" (U.S. Army CHPPM, 1999, p. 1-2~. These guidelines, which were intended for use during deployments and exercises outside CONUS, were not intended to be used as mandatory exposure standards. The key question in the development of doctrine on decontamination is long-term exposure to low-level concentrations in a contaminated envi- ronment. The doctrine would have to establish the sufficient level of de- contamination (i.e., "how clean is clean enough?". Setting of exposure guidelines is a critical step in the assessment of risk and provides a basis for managing the risk (which relates to doctrine).

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DECONTAMINATION 135 The severity and extent of the effects of exposure to CB agents de- pends on the following factors: · individual sensitivity · duration of the exposure · agent concentration · aggravating or mitigating conditions (i.e., medical pretreatments, health status, other chemicals, etc.) USACHPPM has proposed 1-day and 14-day military air guideline (MAG) levels (exposures for 24 hours/day for 1 or 14 days). These levels may appear to be conservative when compared to the Occupational Safety and Health Administration (OSHA) standards or other industrial hygiene guidelines. However, USACHPPM assumes exposures of 24 hours/day while industrial guidelines are based on 8 hour/day exposures. Field commanders are responsible for deciding what risks are neces- sary for accomplishing their missions. Making informed decisions and managing the overall risks in the deployment environment require infor- mation on agent concentrations. The MAGs for chemical warfare agents listed in Table 5-5 are for concentrations that produce minimal and severe effects after 1-day and 14-day exposures. Relating doctrine to risk in the area of decontamination will first re- quire establishing guidelines for what constitutes acceptable risk and then TABLE 5-5 Military Air Guidelines for Chemical Warfare Agents 1-hour MAGs (ppm) Minimal Severe Time-Weighted Average of Agent Effects Effects 1-day to 14-day MAGs (ppm) Tabun 0.008 0.10 0.000010 Sarin 0.008 0.10 0.000010 0.003 0.05 0.000003 VX 0.0015 0.02 0.000030 Sulfur mustard 0.05 no data 0.003a Phosgene 0.10 1.00 0.01 aNot to exceed at any time. Source: U.S. Army CHPPM, 1999.

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36 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES developing the doctrine and training protocols for limiting exposure. At the present time, some of the elements necessary for developing doctrine are inadequate. For example, detection capabilities are not designed for the decontamination environment. The current fast-response methods are not sensitive enough, and the sensitive, definitive assays are very time consuming and not easily adaptable for field use. If the MAGs were ac- cepted as guidelines for managing risks, estimates of exceedances could be made (i.e., an "effects-based" decontamination goal). If an effects-based goal cannot be established, the lower limit of detectability by the most sensitive method available could be adopted as the decontamination goal by default (i.e., an "analysis-based" decontamination goal). Because doctrine is not strongly related to risk, several serious prob- lems remain all but unsolvable. First, no standards can be established for returning previously contaminated equipment to service. Second, decon- tamination doctrine is not consistent across services. And third, problems are more complicated when joint forces or coalition forces are involved. FINDINGS AND RECOMMENDATIONS As belief in the CB threat has increased, decontamination has re- ceived more attention, but few changes in funding have resulted. No extensive, planned, organized research programs are being conducted, and many issues remain unresolved. Finding. lust as only a few benchmarks for the removal of MOPP gear have been established (because detection technology is inadequate), few benchmarks of decontamination levels have been established. Therefore, it is difficult to know when it is safe to return equipment to operational status and impossible to "certify" that previously contaminated equip- ment can be transported to a new location, especially a location in the United States. Recommendation. The Department of Defense should initiate a joint ser- vice, interagency, international cooperative effort to establish decontami- nation standards. Standards should be based on the best science available and may require the development of new models for setting benchmarks, especially for highly toxic or pathogenic agents. If residual decontamination levels are based on ultraconservative tox- icity and morbidity estimates, returning contaminated equipment be- comes impractical. Benchmarks for decontamination should be based on highly accurate, reliable, up-to-date toxicity data.

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DECONTAMINATION 137 Finding. Although significant progress is being made with limited re- sources in exploring decontamination technologies that may be effective, no organized, integrated research program has been developed to meet the new challenges and objectives that have been posed (i.e., environmen- tally acceptable decontamination). Various agencies are actively pursuing many projects, but they are not well coordinated and do not have clear priorities for fixed-site programs, casualty management, and sensitive equipment programs. Recommendation. The Department of Defense (DoD) should coordinate and prioritize the chemicalibiological research and development (R&D) defense program, focusing on the protection of deployed forces and the development of environmentally acceptable decontamination methods. DoD should also establish the relative R&D priority of decontamination in the chemicalibiological defense program. Finding. Recent developments in catalytic/oxidative decontamination (enzymes, gels, foams and nanoparticles) appear promising for decon- taminating a wide range of CB agents. Recommendation. Research on enzyme systems for battlefield decon- tamination (especially for small forces) should be given high priority be- cause they could be used to decontaminate both personnel and equip- ment and would not require large volumes of water or complicated equipment. Recommendation. The Department of Defense should continue to de- velop other catalytic/oxidative systems for larger scale decontamination. If possible, these systems should be less corrosive and more environmen- tally acceptable than current methods. Finding. Low-power plasma technology has been shown to be effective for decontaminating sensitive equipment and has the potential of incor- porating contaminant-sensing capabilities. Recommendation. The Department of Defense should continue to de- velop plasma technology and other radiation methods for decontaminat . . ring equipment.