The Nerve Agent
SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 32
SecuritySecurity The VX Nerve Agent Understanding the risks of a deadly threat By Geary Randall Sugg
TERRORISM AFFECTS EVERYONE, everywhere, cameras were mounted inside and outside the mall every day. It is fast becoming part of the SH&E pro- area. The FBI reviewed the footage after the incident Tfessional’s job to recognize the vulnerability risk fac- to develop a more thorough sequence of events. tors associated with it. Many HazMat training Following is a summary of those events. programs and seminars now cover weapons of mass A man of medium height and build, with short destruction (WMD). Although there are four basic black hair and a mustache, walked up to a tall trash types of WMD—chemical, ordnance, biological and receptacle and dropped a large brown paper sack radiological (COBRA) [DOJ(a)]—this article primari- into it. A busboy noticed that part of the sack was ly focuses on one deadly chemical threat commonly hanging out of the dispenser. He removed the sack known as the VX nerve agent. Although all nerve and set it on top of the trash receptacle so he could agents are deadly, the VX nerve agent is the “bad- properly install a fresh plastic liner. Moments later, a dest of the bad.” In the wrong hands and with the sharp popping sound was heard followed by a hiss- right devices, it could possibly be disseminated to ing noise (like that of an aerosol can). An elderly murder millions. man eating at a table less than 10 feet away from the The case study presented is hypothetical and sim- trash can immediately started choking and fell out of ilar to many training scenarios studied by first his chair to the floor. responders across the country. Because terrorists’ As the cashier dialed 9-1-1, the restaurant manag- potential targets include com- er knelt down beside the man to attempt a first-aid Geary Randall “Randy” Sugg is mercial and industrial facili- maneuver learned in a recent CPR class. Suddenly, a career professional firefighter, ties, SH&E students should the restaurant manager grabbed his chest, vomited holding the rank of captain with also benefit from studying it, and fell forward to the floor. Both men lay on the the Paducah (KY) Fire Dept. He is a as it is designed to stimulate floor, twitching and jerking as they began foaming at member of the International Assn. of Fire group discussion, and increase the mouth. Other people began gathering around Fighters Local 168 with more than awareness and understanding the two men, hoping they could somehow help, but 18 years’ experience in professional fire of what terrorism is and the they also began coughing and staggering. In addi- service. Off-duty, Sugg works as an risks associated with such an tion, many became confused and one individual intern in the Human Resources Dept. incident. The discussion fol- suddenly lost his vision. Paramedics soon arrived, for the City of Paducah, where he is lowing the case study pro- expecting to find one possible cardiac patient. What involved in workers’ compensation, vides answers to the challenge they found instead was an array of lifeless bodies. OSHA recordkeeping, risk management questions posed about it. They began triage and patient assessments, but and personnel. Sugg holds a within seconds they, too, began to experience similar B.S. in Business and is pursuing an The Case Study symptoms and lost consciousness. M.S. in Occupational Safety and Health One warm summer Sat- When a local fire engine company arrived, pan- at Murray State University. urday afternoon around 2:00 icked customers were pouring out of the mall, trip- He is a student member of ASSE pm, a security camera cap- ping, falling and running over each other. Many and AIHA, and belongs to the tured an act of terrorism occur- were coughing and some appeared to be choking Rho Sigma Kappa honor society for ing inside the food court of a and gasping for breath. When the fire company offi- occupational safety and health. crowded shopping mall. Other cer stepped off the truck, a mall security guard 32 PROFESSIONAL SAFETY MARCH 2004 www.asse.org SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 33
informed him that he had observed the situation on FigureFigure 1 1 monitors located in the securi- ty office and had immediately Chemical Structure called for full evacuation of the facility. He said he counted at of VX Nerve Agent least eight people down and showing no signs of move- ment. The fire officer tried to contact the EMTs, but received no response. After quickly assessing the situation, he concluded that a fast-acting airborne hazard was inside, requiring Level A protection. Although difficult to resist the temptation to rush in, he knew regular structural firefighting suits with SCBAs would not offer the protection needed for such an atmosphere. Plus, it was not yet Biological & Chemical Weapons: known what deadly agent had been released. The A Brief Overview fire officer then contacted central dispatch and Biological and chemical weapons have been used requested that a second alarm be given for police throughout history in warfare and terrorist activi- who could provide traffic control and that more ties. As far back as 600 BC, the Assyrians contami- EMS workers be summoned. He also requested that nated the water supply of their enemies with Rye the county HazMat team be activated. Ergot. When the plague broke out among the ranks of the Tartar army during its siege of Kaffa in 1346, Challenge Question 1 they used catapults to hurl the corpses over the city’s What signs and symptoms did the victims in the walls in order to start an epidemic. Even Napoleon food court area exhibit? Autopsies revealed that the attempted to infect the people of Mantua with elderly man and restaurant manager died within a swamp fever during his Italian campaign in 1797. few minutes. What type of hazard (e.g., inhalation, The Japanese army reportedly used various biologi- skin contact) did they likely encounter to cause cal agents during World War II to contaminate food death so quickly? and water supplies of Chinese cities (Stockholm International Peace Research Institute). Challenge Question 2 Eventually, chemical weapons were intentionally Why did the company officer in this scenario developed and used. Mustard gas and nerve agents elect not to have his firefighters rush in for a search- are the two major classes of chemical weapons that and-rescue immediately on arrival? pose a significant threat to the world’s population. Challenge Question 3 Mustard was first synthesized in the early 1800s and Assuming drugs were available, how would you used by the Germans against the British at Ypres, treat a patient who was exposed to VX nerve agent? Belgium, on July 12, 1917, during World War I. The use of mustard and chlorine resulted in approxi- What Is VX? mately 400,000 casualties during that war. Even VX nerve agent is one of the most dangerous though the Geneva Convention of 1925 prohibited manufactured chemicals. It was first developed in the use of chemical weapons, production continued Port Down, Wiltshire, England in 1952, where its and many countries began to stockpile them. devastating effects were tested. The U.S. received it Since World War I, it is believed that mustard gas by trading information on thermonuclear weapons has been used by Great Britain in the Middle East; to Great Britain. (The agent was featured in the film the French in Morocco; Italy against Ethiopia in 1936; The Rock, as a somewhat green liquid used by a ter- Japan against China in 1937; Poland against rorist to threaten San Francisco.) Germany in 1939; the Russians in central Asia; Egypt Classes of nerve agents have not changed in more against Yemen from 1963 to 1967; Iraq against Iran than 50 years. What has changed, however, is the during the Iran-Iraq War; and Iraq against the Kurds understanding of their potency. New considerations [Reutter(b)]. Terrorists have also used these agents include the fact that more women (who may be on civilian populations in Japan. On March 20, 1995, affected differently than men) are now serving in the members of the Shinrikyo religious sect released military and the growing likelihood that civilians sarin at several points in the Tokyo subway system, will be targeted. Concern regarding the nonlethal killing 11 and injuring more than 5,500 people (Ohbu but delayed effects that may be produced by nerve and Yamashina 587). agents is growing as well (Reutter). Nerve agents consisting of basically two classes, www.asse.org MARCH 2004 PROFESSIONAL SAFETY 33 SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 34
TableTable 1 1 Chemical Agent Comparison: Symptoms & Hazards
Symbol/ Common Name Agent Type Symptoms Hazard GB (sarin) Nerve agents Dim or blurred vision; pinpointing of the Skin dose effective in minutes to GD (soman) pupils; running nose; salivation; nausea and hours. Respiratory dose effective with- GA (tabun) vomiting; sweating; tightness of chest; diffi- in seconds to minutes. Skin exposure VX culty breathing; convulsions; loss of con- has a better survival rate but VX is sciousness; tachycardia; incontinence; death. fatal if inhaled or absorbed through the skin. These agents are extremely toxic and lethal. HD Blister agent, Blisters and reddening of skin; eye pain, Although it absorbs rapidly into the commonly reddening and damage; sneezing and skin, eye effects may appear in a few called “mus- coughing; airway irritation and damage; hours; respiratory effects and blisters tard” diarrhea, fever and apathy. in two to 24 hours. It can be lethal in large doses. L (lewisite) Blister agent Immediate stinging pain or irritation of Immediate pain. Most symptoms in skin; instant eye pain with severe perma- about 12 hours. It can be lethal in nent damage or blindness; running nose; large doses. coughing, sneezing and lung edema; other symptoms similar to the HD agent. CX (phosgene Blister agent Immediate burning; corrosive to skin; eyes, Immediate pain with other symptoms oxime) nose and airway irritation and damage; shortly thereafter. It can be lethal in victim can drown in own mucous. large doses. CK (cyanogen Blood agents Flushed (reddish skin); cherry red lips It can cause death in six to eight chloride) (blue in African-American or other dark- minutes. AC (hydrogen skinned races); confusion; drowsiness; cyanide) headache; gasping for air; frothing or vom- iting, then weakness, unconsciousness, col- lapse and death. CG (phosgene) Choking Corrosive to skin and eyes; irritates throat In very high doses, it can cause death CL (chlorine) agents and lungs; dizziness; tightness of chest; after several days. delayed pulmonary edema. Source: DOJ. COBRA WMD Responder Guide.
G and V, were conceived in the 1930s. They belong 13, 1968, at the Dugway Proving Grounds in Utah. A to a group of chemicals called “organophosphates” malfunction in a spray tank used to test aerial spray- that were originally developed in 1854 to control ing, coupled with unfortunate winds, resulted in the insects and save crops. German scientist Gerhard contamination of grazing land outside the test site’s Schrader synthesized the GA nerve agent, also boundaries. Although no human injuries were called “tabun,” in 1936. The GB agent “sarin” was reported, more than 6,000 sheep in the area died. synthesized about a year later, and “soman” or In July 1969, a VX leak from weapons at a storage “GD” was made in 1944. Although it appears that facility on Okinawa led to the hospitalization of 23 Germany did not use these agents during World U.S. military personnel and one civilian. There is no War II, it is believed that the country had tons of proof that the VX agent has been used in any large- both. After the war, the U.S. and Russia also became scale military operation as of yet (CBWInfo). large producers and stockpilers of tabun and sarin. As noted, England developed the worst nerve agent Physical/Chemical Properties yet, named VX, in the 1950s. It is the primary Nerve agents are similar to insecticides in that V-type agent that is the least volatile but most potent they contain either a fluorine, sulfur or cyanide sub- of all nerve agents. The “V” stands for venom be- stituent group. VX contains a sulfur substituent cause of its extreme potency (Reutter, et al). group. It is 1,000 to 10,000 times more potent than the most potent organophosphate insecticides com- Accidental Release of VX mercially available and it is theoretically possible to An accidental release of VX occurred on March disseminate it in high enough vapor concentrations 34 PROFESSIONAL SAFETY MARCH 2004 www.asse.org SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 35
so that one breath can kill (Opresko 440). The agent’s these are not the targets of toxicity and are of chemical formula is: unknown function. There is lacking correlation Classes CH CH O-P (O)(CH )-SCH CH N (C H ) between toxic signs and symptoms, dose and degree 3 2 3 2 2 3 7 2 of blood cholinesterase inhibition. Repeated small of nerve It is also known as O-ethyl S-[2-(diisopropylamino) exposures can suppress nearly all blood cholinesterase ethyl]-methylphosphonothioate. Figure 1 (pg. 33) de- activity while producing only negligible clinical agents have picts its structure. effects. However, its inhibition is often an excellent Although VX is sometimes referred to as a gas, it indicator of nerve agent exposure. As far as chronic not changed is normally a colorless to straw-colored liquid. It has toxicity of VX, litte data can be found in the literature. a molecular weight of 267.4; a vapor density of 9.2 in many (air = 1 STP); and a liquid density of 1.0083 g/ml at Reproductive & Developmental Effects 25ºC. The agent has a water solubility of 30 g/L per years. What 100g at 25ºC and a vapor pressure of 0.0007 mm Hg Studies have been conducted on pregnant rats that at 25ºC. It has a boiling point of 298ºC at 760 mm Hg; were dosed with 0.25, 1.0 or 4.0 micrograms VX/kg has changed, specific gravity of 1.0113; melting point of -50ºC; vis- by subcutaneous (sc) injection on day six to 15 of ges- cosity (centistokes) of 9.958 at 25ºC; and a volatility tation. The animals were killed on the twentieth day however, of 8.9 mg/m3 at 25ºC. of gestation and the examined fetuses showed no evi- dence of malformations. Fetal body weight, litter size is the Effects on the Nervous System and sex ratio were within normal limits. It is important to first discuss how acetylcholine VX effects on the development and reproduction understanding (a common neurotransmitter) works in order to of sheep were also evaluated following the acciden- understand how the VX nerve agent affects the nerv- tal release in Utah. The 79 surviving animals that of their ous system. Acetylcholine (ACh) is found in the cen- were pregnant at the time of exposure were evaluat- tral and peripheral nervous system. When it is ed for changes in red blood count and AChE activi- potency. released from an axon terminal, ACh moves across ty, and for signs of toxicity over a six-month the synaptic cleft to bind to a receptor on the other post-exposure period. The researchers concluded side of the synapse (on the post-synaptic mem- that VX had little or no effect on fetal growth and brane). In the peripheral nervous system, ACh is development (Opresko 452-455). located at the “neuromuscular junction,” where it acts to control muscular contraction. Basically, nerve Carcinogenicity & Genotoxicity agents are inhibitors of acetylcholinesterase (AChE), Little information is available on the potential an enzyme responsible for stopping the action of carcinogenicity of VX in humans. No standard, long- acetylcholine at some neuronal synapses and term carcinogenicity studies have been performed myoneural junctions. By a mechanism of phospho- on lab animals exposed to the agent. rylation, VX acts as a substrate for AChE, thereby Similarly, information regarding the genotoxicity preventing deactivation of ACh. Simply put, with a of VX in humans is not available. Although tests on depletion of AChE and a buildup of ACh, acetyl- microorganisms and mammalian cell cultures have choline continues to act (Opresko 442). been conducted, VX was not found to be mutagenic or was only weakly mutagenic (Opresko 452-455). Toxicity However, children would have some special vulner- Organophosphate nerve agents can act by dermal, abilities to nerve agents. The release of chemical tox- oral or inhalation routes of exposure. VX nerve agent ins would disproportionately affect children attacks all synapses that use acetylcholine as a neuro- through several mechanisms. With aerosolized VX, transmitter. This means both the central and peripher- the higher number of respirations per minute in chil- al nervous systems are affected. The anticholinesterase dren would result in exposure to a relatively greater effects can be characterized as being muscarinic, nico- dosage. Also, the more permeable skin of newborns tinic or central nervous system (CNS) related. and children combined with a larger surface-to-mass Muscarinic effects occur in the parasympathetic sys- ratio results in greater exposure to transdermally tem (bronchi, heart, pupils; and salivary, lacrimal and absorbed toxicants (AAP). sweat glands) and result in signs of pulmonary edema, bradycardia, miosis, tearing and sweating. Treatment Nicotinic effects occur in the somatic (skeletal/motor) First responders, heathcare providers and other and sympathetic systems, and result in muscle fascic- rescue workers wearing protective gear should decon- ulation, muscle weakness, tachycardia and diarrhea. taminate the patient’s skin with hypochlorite (house- CNS effects include headache, depression, convul- hold bleach diluted 1:10) or soap and water, and rinse sions and coma, as well as respiratory arrest (it causes the eyes with plain water. Treatment with drugs can copious secretions, paralyzes the respiratory muscles be lifesaving as well. Two drugs, atropine and prali- and inhibits the respiratory center of the brain), confu- doxime chloride, have been used as antidotes for sion and slurred speech. Breathing a lethal dose nerve agent poisoning. Atropine blocks the action of (10 mg-min/m3) can kill in seconds to minutes, while excess ACh primarily at muscaric sites, decreasing a lethal dose on the skin can kill in minutes to hours secretions, bronchoconstriction and intestinal motility. (Munro, et al 952). The initial dose is 2mg for mild dyspnea to 6mg or Nerve agents also inhibit blood cholinesterases, but more for severe dyspnea or multisystem signs. An www.asse.org MARCH 2004 PROFESSIONAL SAFETY 35 SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 36
automatic injection Personal Protective Equipment device called the It is foolish for first responders to rush into a haz- AtroPen auto-injec- ardous situation without first evaluating the inci- tor delivers this dent area and determining the severity of danger. intramuscularly; After the initial assessment of a HazMat incident, pressing the device special considerations must be given to the selection against the thigh of proper PPE and how it may affect the wearer’s activates a spring ability to execute the rescue. that injects the dose Chemical protective clothing is designed to shield into the muscle. The or isolate first responders from the chemical, physi- drug can be given as cal and biological hazards that may be encountered often as every five during HazMat operations. Guidelines, descriptions minutes until secre- and recommendations for PPE are based on EPA’s tions are minimal; widely used levels of protection: Levels A, B, C and some patients re- D (details at www.epa.gov/superfund/programs/ quire 15 to 20mg er/hazsubs/equip.htm). during the first three Chemical warfare agents are easily and inexpen- hours after ex- sively produced and pose a significant threat to mil- posure. Miosis may itary forces, first responders and the public. VX persist but its resolu- presents both a respiratory and a skin hazard. Source: Millard, C.B., et al. tion should not be Although it does not readily produce vapors at room used as a therapeutic temperature, and is mainly a skin contact hazard, it This image depicts endpoint. There is no direct effect on the can be disseminated into the air through devices the structure nerve agent or AChE. such as an aerosol can, a bomb or a crop-dusting of acetylcholinesterase Pralidoxime chloride attaches to and plane. In liquid form, droplets of nerve agent may be with part of the VX nerve releases the inhibiting agent from absorbed by the skin; in a vapor state, they may agent molecule (black) in AChE. The initial dose is 1g, given intra- enter the body through the lungs, eyes or GI tract. the acetylcholine-binding venously over 20 to 30 minutes, which Upon initial entry into an area suspected of nerve site. The VX nerve agent can be repeated at hourly intervals for agent contamination, Level A protection must be reacts with the enzyme one or two additional doses. An auto- worn to ensure full protection of both the respirato- and a portion of the matic injector dispenses a 600mg dose ry tract and the skin. After a more-accurate assess- agent remains covalently intramuscularly when the device is ment of agent concentration in the atmosphere is attached to the enzyme, pressed against the thigh. made, protection may be downgraded to Level B if thus inhibiting its function. Newer oximes may be more effective it is determined that a vapor hazard no longer exists. than pralidoxime against some nerve Level A includes a totally encapsulated chemical- agents, but they are not currently commercially resistant suit, with a self-contained breathing appa- available due to ongoing testing. These oximes are ratus (SCBA) or supplied air respirator (SAR) with termed the H-series oximes and dioximes (HI-6, escape tank. Because this level provides maximum HL07). They have more ability to reactivate phos- respiratory and skin protection, it is used when there phorylated AChE, and have proven to be more com- is a high potential for liquid splash, a toxic respira- bative against the effects of all nerve agents in tion and skin vapor hazard, or where the chemical animal studies because they take direct antimus- agent is unidentified. The responder Level A suit carinic and antinicotinic actions to counter these produced by Kappler has been tested and found effects. Other promising treatments include the use effective against chemical agents, as has the of exogenous cholinesterase and human monoclon- Trelleborg Trellchem suit. Both support the mission al antibodies. They prevent nerve agents from bind- profile used by the U.S. Army Technical Escort Unit ing to AChE (Med CEU). (TEU), which provides a secure escort for WMD and Nerve agents can still cause prolonged convul- is tasked with providing support to civilian agencies sive activity leading to severe neuropathology, even in the event of a WMD incident. if atropine and pralidoxime are used. Because ani- Some models of chemical-resistant gloves (e.g., mal experiments suggest that anticonvulsants such North’s SilverShield and Safety4’s 4H) have been as diazepam can prevent brain damage after expo- tested and found to be effective against some types sure to nerve agents, a 5 or 10mg dose of diazepam of chemical agents. Various types of chemical-resist- (valium) has been added to the usual regimen in ant boots are also available to allow full encapsula- cases of severe nerve agent poisoning (“Treatment of tion. In summary, Level A protection should be worn Nerve”). These drugs were issued to U.S. troops when the highest level of respiratory, eye, skin and during the Persian Gulf War in the form of an anti- mucous membrane protection is needed. In all cases, dote kit called the Mark I. (More information on the gear must be absolutely vapor tight. treatment, uses and dosages of lifesaving drugs can Level B protection includes a nonencapsulating be found at www.er365.com/germ%20warfare chemical splash-resistant suit with hood and SCBA. -nerve%20gas-anthrax-biological%20warfare%20 The air tank is outside the suit so it provides maxi- treatment.htm.) mum respiratory protection with less skin protection. 36 PROFESSIONAL SAFETY MARCH 2004 www.asse.org SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 37
This level is mainly used when an agent presents no tion but VX will be absorbed through cloth and skin. skin vapor hazard and a low splash potential exists. Time following exposure is very critical so exposed Level B can also be worn in low-oxygen environ- clothing must be removed and the skin decontaminat- ments. This nonencapsulated system requires either ed (Wester, Tanojo, et al ). an SCBA or SAR and a Tyvek-F or equivalent chem/biosuit with inner gloves. Outer butyl rubber Decontamination gloves and chemical-resistant boots must be worn. The two levels of decontamination are emergency The advantage of using Level B is that the air and technical. Together, these cover the rapid decon- cylinders can be removed or changed without open- tamination of victims and the more deliberate ing the suit. A disadvantage is that the SCBA is decontamination of the first responders at the scene. exposed to the atmosphere. In summary, Level B Emergency decontamination involves neutralizing should be should be worn when the highest level of the agent on the skin and physically removing the respiratory protection is needed, but a lesser level of agent hazard; it must be performed quickly. skin and eye protection is required. It is the mini- Technical decontamination is performed to remove mum level recommended on initial site entries until contamination from PPE of rescue workers, equip- hazards have been further identified and defined by ment and facilities in a deliberate manner. monitoring, sampling and other reliable methods of Technician-level responders primarily focus on analysis and personnel equipment corresponding emergency decontamination of casualties and tech- with those findings [DOJ(b)]. nical decontamination of responders. Gas masks have received wide media coverage, The best decontaminant for the VX nerve agent is but they have limitations as well. How well they 10 percent sodium hydroxide in alcohol. However, it actually work depends on factors such as their can be neutralized by the commercial types HTH design, manufacture and storage. The nerve agent (calcium hypochlorite) and sodium hypochlorite used, wind speed and the individual’s distance from (bleach) or the military types DS-2 and super tropi- the source of exposure should also be considered. cal bleach. Removal of the agent can be accom- Masks that fit only over the nose and mouth will not plished with ethylene glycol, soap and water, likely be effective against nerve agents because the adsorbents and sealants [DOJ(c)]. vapor can be absorbed through the conjunctiva. U.S. During a basic hydrolysis of VX, it is important to military standard full-facepiece masks have the consider that up to 10 percent of the agent is con- adsorbent capacity to protect against many times the verted to EA2192 (an Edgewood arsenal number LCt50 (concentration and time of exposure that and common synonym for diisopropylaminoethyl would be lethal for 50 percent of the population) of methylphosphonothioic acid). A Class B poison nerve agents, but some other masks may be less effi- would result, based on the concentration expected to cient. Any gas mask can lose protective capacity if it be formed during hydrolysis and its toxicity (accord- is crushed or stored in high humidity. The tightness ing to animal studies). of the seal around the face is usually more of a limit- The large-scale decontamination procedure, ing factor than the filter’s adsorbent capacity. Beards which uses both HTH and NaOH, destroys VX by and eyeglasses, among other variables, may inter- oxidation and hydrolysis. Normally the large-scale fere as well (“Treatment of Nerve”). product contains 0.2-0.4 wt. % EA2192 at 24 hours; at To help validate the use of PPE for protection pH 12, it has a half-life of about 14 days. Therefore, against VX, Wester, et al performed a study to predict the 90-day holding period at pH 12 results in about a VX toxicity to a uniformed soldier using parathion in 64-fold reduction of EA2192 (six half- lives). This vitro human skin exposure and absorption (Wester, holding period is sufficient to reduce the toxicity of Quan, et al). The study determined the amount of per- the product under that of a Class B poison. Other cutaneous absorption of parathion when applied to less-toxic products include diisopropyaminoethyl bare human skin and uniformed skin with and with- mercaptan, ethyl methylphosphonic acid, methyl- out sweat. “Parathion percentage dose absorbed phosphonic acid, diethyl methylphosphonate and through naked skin (1.78 +/- 0.41) was greater than ethanol. The small-scale decontamination procedure dry uniform skin (0.29 +/- 0.17; p = 0.000) and sweat- uses enough HTH to oxidize all VX so no EA2192 is ed uniform skin (0.65 +/- 0.16; p = 0.000). Sweated and formed (Munro, et al 967, 952-953). dry uniform skin were also different (p = 0.007).” These results were then applied to VX skin perme- Environmental Fate ability for bare skin (head, neck, arms and hands) and The volatility of the VX nerve agent is relatively the remaining uniformed skin over the various low, having a vapor pressure of 0.0007 mm Hg. A regions of the human body. Risk assessment shows vapor concentration of 10.5 mg/m3 has been reported VX 50 percent lethality within the first hour for a sol- for a temperature of 250ºC. Photodegradation is not a dier wearing a sweated uniform. An eight-hour post- significant environmental fate for VX because it does exposure to bare skin plus trunk area predicted not absorb ultraviolet radiation above 290nm. By lethality for both dry and sweated uniform, and, at 96 reacting with photochemically produced hydroxyl hours post exposure, all body regions individually radicals in the troposphere, VX is estimated to have a exposed would produce lethality. Military uniform half-life of approximately six hours. The water solu- and public clothing provide some immediate protec- bility of VX is 3g per 100g solvent at 250ºC and 7.5g www.asse.org MARCH 2004 PROFESSIONAL SAFETY 37 SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 38
Key Terms Acetylcholine: A neurotransmitter (C3H17NO3) released at Oxime: Any of various compounds obtained chiefly by the autonomic synapses and neuromuscular junctions, active in the action of hydroxylamine on aldehydes and ketones and character- transmission of nerve impulses and formed enzymatically in the ized by the bivalent group C=NOH. tissues from choline. Parasympathetic system: The part of the autonomic nervous Acetylcholinesterase: An enzyme that hydrolyzes choline system that contains chiefly cholinergic fibers, that tends to induce esters and that is found especially in blood plasma. secretion, to increase the tone and contractility of smooth muscle, Atropine: A racemic mixture of hyoscyamine usually obtained and to slow the heart rate, and that consists of 1) a cranial part from belladonna and related plants of the family Solanaceae and made up of preganlionic fibers leaving and passing the midbrain used especially in the form of its sulfate for its anticholinergic by the oculomotor nerves and the hindbrain by the facial, glos- effects (as relief of smooth muscle spasms of dilation of the pupil sopharyngeal, vagus, and accessory nerves and passing to the cil- of the eye). iary, sphenopalatine, submandibular, and otic ganglia of the head Axon terminal: A usually long and single nerve-cell process or to ganglionated plexuses of the thorax and abdomen and post- that conducts impulses away from the cell body. ganglionic fibers passing from these ganglia to end organs of the Boiling point: The temperature at which the vapor pressure of head and upper trunk; and 2) a sacral part made up of pregan- a liquid equals the pressure of the atmosphere in contact with its glionic fibers emerging and passing in the sacral nerves and pass- surface. ing to ganglionated plexuses of the lower trunk and postganglionic Bradycardia: Relatively slow heart action whether physiologi- fibers passing from these plexuses chiefly to the viscera of the cal or pathological. lower abdomen and the external genital organs. Bronchi: Either of the two primary divisions of the trachea that Parathion: An extremely toxic thiophosphate insecticide lead respectively into the right and the left lung. (C10H14NO5PS). Central nervous system: The part of the nervous system which Peripheral nervous system: The part of the nervous system in vertebrates consists of the brain and spinal cord, to which senso- that is outside the central nervous system and comprises the cra- ry impulses are transmitted and from which motor impulses pass nial nerves excepting the optic nerve, the spinal nerves and the out, and which supervises and coordinates the activity of the entire autonomic nervous system. nervous system. Phosphorylation: The process of phosphorylating a chemical Conjunctiva: The mucous membrane that lines the inner sur- compound either by reaction with inorganic phosphate or by face of the eyelids and is continued over the forepart of the eyeball. transfer of phosphate from another organic phosphate. Convulsion: An abnormal violent and involuntary contraction Photodegradation: Degradation by means of radiant energy or series of contractions of the muscles. (as light). Density: Mass per unit volume. Pralidoxime: A substance (C7H9CIN2O) that restores the reac- Half-life: The time required for half of something to undergo a tivity of cholinesterase and is used to counteract phosphorylation process as a) the time required for half of the atoms of a radioac- (as by an organophosphate pesticide)—also called 2-PAM. tive substance to become disintegrated; b) the time required for Pulmonary edema: Abnormal accumulation of fluid in the lungs. half the amount of a substance (as a drug or radioactive tracer) in Somatic: Of, relating to, supplying or involving skeletal muscles. or introduced into a living system or ecosystem to be eliminated or Specific gravity: The ratio of the density of a substance to the disintegrated by natural processes. density of some substance (as pure water) taken as a standard Intravenous: Situated within, performed within, occurring when both densities are obtained by weighing in air. within or administered by entering a vein. Substituent: An atom or group that replaces another atom or In vitro: Outside the living body and in an artificial environment. group in a molecule. Lacrimal: Of, relating to, associated with, located near or consti- Substrate: A substance acted upon (as by an enzyme). tuting the glands that produce tears. Sympathetic system: The part of the autonomic nervous system Melting point: The temperature at which a solid melts. that is concerned especially with preparing the body to react to situ- Miosis: Excessive smallness or contraction of the pupil of the eye. ations of stress or emergency, that contains chiefly adrenergic fibers Molecular weight: The mass of a molecule that may be calcu- and tends to depress secretion, decrease the tone and contractility lated as the sum of the atomic weights of its constituent atoms. of smooth muscle, increase heart rate, and that consists essentially Muscarinic effects: Relating to, resembling, producing or medi- of preganglionic fibers arising in the thoracic and upper lumbar ating the effects (as a slowed heart rate, increased secretion by parts of the spinal cord and passing through delicate white rami exocrine glands and increased activity of smooth muscle) that are communicantes to ganglia located in a pair of sympathetic chains produced on organs and tissues by acetylcholine liberated by post- situated one on each side of the spinal column or to more peripher- ganglionic nerve fibers of the parasympathetic nervous system and al ganglia or ganglionated plexuses and postganglionic fibers pass- that are mimicked by muscarine. ing typically through gray rami communicantes to spinal nerves Neuromuscular junction: The junction of an efferent nerve with which they are distributed to various end organs. fiber and the muscle fiber plasma membrane. Synapse: The place at which a nervous impulse passes from Neurotransmitter: A substance (as norepinephrine or acetyl- one neuron to another. choline) that transmit nerve impulses across a synapse. Tachycardia: Relatively rapid heart action whether physiologi- Nicotinic effects: Relating to, resembling, producing or mediat- cal (as after exercise) or pathological. ing the effects that are produced by acetylcholine liberated by nerve Vapor pressure: The pressure of a vapor in equilibrium with its fibers at autonomic ganglia and at the neuromuscular junctions or liquid. voluntary muscle and that are mimicked by nicotine which increas- Viscosity: The internal resistance or friction offered to an object es activity in small doses and inhibits it in larger doses. moving through a fluid. Organophosphates: Phosphorus-containing organic pesticides Volatile: Readily vaporizable at a relatively low temperature. that act by inhibiting cholinesterase.
Source: MEDLINEplus.
38 PROFESSIONAL SAFETY MARCH 2004 www.asse.org SuggFeatureMarch2004.qxd 2/12/04 9:31 AM Page 39
per 100g solvent at 150ºC. A Henry’s law constant esti- References mated to be 3.5 x 10-9 atm m3/mol indicates a low American Academy of Pediatrics (AAP). “Chemical-Biologi- First potential for evaporation from water. Its evaporation cal Terrorism and Its Impact on Children: A Subject Review.” Pediatrics. 105(2000): 662. responders, rate is about 1/1500 that of water. VX’s reported half- Benitez, F.L., et al. “CBRNE: Nerve Agents, V-Series: VE, VG, lives in water at 250ºC and pH 7 ranges from 400 to VM, VX.”