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Terrorist Chemical Releases: Assessment of Medical Risk and Implications for Emergency Preparedness

Posted on: Sunday, 31 July 2005, 03:00 CDT

ABSTRACT

In the last few years, public health has played an increasingly important role in disaster management, particularly in biological terrorist event planning. However, little time or financial expenditure has been spent on preparation for terrorist-related chemical events. In addition, chemical hazardous material and industrial accidents are common occurrences in the United States and have significant public health and emergency preparedness consequences. This manuscript reviews previous terrorist-related and industrial chemical events, an assessment of the risk that these events have on the public health, and ways that hospitals and local, state, and regional public health agencies may plan for such an event.

Key Words: emergency preparedness, chemical agents, terrorism, risk assessment, emergency medicine.

INTRODUCTION

Over the last several years, and following the incidents of September 11, 2001, much energy has been expended preparing for a terrorist event. The majority of the concern and monetary expenditures have been in preparing for the release of biological agents. However, there are multiple recent real-world examples of terrorist and military releases of "chemical agents." Although there are similarities in planning, chemical events differ from biological and radiological events in several ways. Chemical events produce victims who develop symptoms simultaneously, leading to an initial mass casualty event. This is typically followed by large numbers of patients reporting over a broader time frame that is more typical of biological events. Chemicals have the potential to immediately affect and incapacitate health care workers, leading to the combination of a mass casualty event with a limited health care workforce. And, of course, chemicals may require the delivery of antidotal therapy within minutes of exposure, making reliance on regional caches impossible. This article will attempt to review both intentional and accidental chemical releases, discuss the risks involved, and discuss preparations that are necessary.

"Chemical agents" are those chemicals that may be released by terrorists or militaries with the aim of producing mass casualties. They include agents that have been developed by military organizations (e.g., nerve agents, vesicants), as well as chemicals that are routinely used in industrial processes (e.g., cyanide, phosgene, hydrofluoric acid, chlorine, ammonia). Many of these chemical agents are among the most potent chemicals known.

Terrorist releases may occur in several different ways. The purposeful release of an industrial chemical from a fixed facility or transportation vehicle is the least complex and probably the most likely event. Many of these industrial chemicals are ubiquitous in American cities and typically act as irritant gases (e.g., ammonia, chlorine, phosgene), although industrial chemicals may also have systemic effects (e.g., cyanide, hydrogen sulfide). Alternatively, terrorists may choose to manufacture more sophisticated chemical agents, such as nerve agents (e.g., VX, sarin, soman, tabun) or mustard. Although the technical aspects of manufacturing these agents has been fine-tuned by the world's militaries over the last century, their manufacture would require the clandestine production of a large volume of chemical, which may be difficult. Table 1 reviews the clinical features of the most likely chemical agents and their characteristics.

Although some of these agents have lethal doses in the milligram range (Sidell and Borak 1992; Sidell and Groff 1974), when these agents have been deployed in real-world scenarios, large numbers of casualties, but few actual fatalities, have been produced (Trumpener 1975; Hyams et al. 2002; Okumura et al. 1996; Morita and Yanagisawa 1995; Wing et al. 1991). Historically, both terrorist-related and accidental chemical-releases have resulted in widespread fear, anxiety, and overwhelming numbers of mildly affected casualties. This large number of asymptomatic to mildly symptomatic patients represents the largest risk to the health care system from chemical agents and should be a main focus of emergency preparedness and public health planning.

WHAT ARE THE CHARACTERISTICS OF PREVIOUS CHEMICAL RELEASES?

Large-scale chemical releases have historically produced hundreds to thousands of mildly symptomatic patients, but few fatalities (Okumura et al. 1996; Wing et al. 1991; Okumura et al. 1998; Okudera et al. 1997). Several examples have been described in the medical literature and will be discussed here.

In June 1994 a religious-based organization, named the Aum Shinryko, released vaporized sarin nerve agent within the city of Matsumoto, Japan. The group used a converted refrigeration truck that was equipped with metal tanks, a heater, and a fan to produce a sarin vapor that was released from the truck while it was parked outside a residential apartment building. Despite releasing the vapor in a populated residential area, only 600 of the city's 200,000 residents were affected. Fifty-eight of the residents were hospitalized and seven people died (Morita and Yanagisawa 1995).

Table 1. Characteristics of common chemical agents.

The following year, in March 1995, the same organization again released sarin, this time into five Tokyo subway cars during Monday morning rush hour (7:55 a.m.). The targeted subway station was situated directly beneath the Japanese National Government's ministry offices (Okumura et al. 1996). Following the event, more than 5000 people sought medical care (Okumura et al 1996). St. Luke's International Hospital, situated within 3 km of the event, cared for more than 500 patients within the first 2 hours after the release and 640 in the first day (Okumura et al. 1996). Sarin is an organic phosphorous compound ("nerve agent") that requires low concentrations to produce fatalities (liquid LD50 = 1.7 g),1 particularly in its vapor form (LCT50 = 100 mg min/m^sup 3^).2 Sarin evaporates readily and was an ideal agent to use for this type of attack. However, despite the release of this agent in an enclosed, crowded space, only 12 citizens died (Okumura et al. 1998).

In October, 1987, 53,000lbs of hydrofluoric acid were accidentally released from a petrochemical plant in Texas (Wing et al. 1991). The release produced a vapor cloud that covered a community of 41,000 residents, sending 939 citizens to area hospitals. Of the exposed, 94 were admitted to hospital, and there were no deaths reported (Wing et al. 1991).

One example of a large-scale military chemical release has been well described. In April 1915, the German military released more than 150 tons of chlorine near Ypres, France. The chlorine was stored in thousands of canisters placed within the German trenches and opened when the wind blew toward the Canadian and French troops. Although politically motivated reports have described thousands of deaths, actual French and German accounts from the time refer to 625 casualties and 3 deaths (Trumpener 1975).

In 1984, the world's worst industrial disaster occurred in Bhopal, India. Late at night on December 2, over a 1-2 hour period, approximately 27 metric tons of methyl isocyanate (MIC), and possibly phosgene, hydrogen cyanide, nitrogen oxides, and carbon monoxide, were released in proximity to a highly populated area (Ramana Dhara and Dhara 2002). Environmental factors, including low wind speed and a thermal inversion, prevented dissipation of the chemicals and resulted in exposure of 200,000 of the 900,000 residents of Bhopal (Ramana Dhara and Dhara 2002; Singh and Ghosh 1987). The release produced more than 80,000 victims with approximately 3,000 deaths (Varma and Guest 1993). There has been considerable controversy over whether the release was an industrial accident or the intentional act of individuals/terrorists. In either case, Bhopal is a striking example of the effectiveness of chemical agents. However, it should be noted that the mass fatalities in Bhopal were due to the tremendous volume of chemicals used, the location of the release (populated area), and favorable environmental conditions.

WHY ARE CHEMICAL RELEASES MORE LIKELY TO PRODUCE MASS CASUALTIES AND NOT MASS FATALITIES?

In several of the earlier examples, despite the use of large volumes of chemicals (Texas and Ypres) or their use in enclosed spaces (Tokyo), releases of chemicals have produced few fatalities. The one instance of significant fatalities (Bhopal) required very large volumes of chemicals, released in a populated area with favorable environmental conditions.

The difficulty in producing fatalities with chemical agents may be due to several factors. First, it is difficult to produce an airborne cloud of chemicals in open air that have adequate local concentration to kill a substantial number of people. Occasionally, lethal concentrations have been produced in small or enclosed areas, such as within a theater in Moscow in 2003 (Wax et al. 2003), or with very large volume releases, as in Bhopal (Rhamana Dhara and Dhara 2002). However, the development of a lethal threshold airborne concentration in a large area, such as a stadium or open-air venue, may be difficult to produce and would likely require tremendous volumes \of chemical with an advanced dispersal device and favorable environmental conditions. The reasons for this can be shown using a simplified model. Say, for example, a terrorist targeted an open- air baseball stadium. The example stadium (based on an actual stadium) is 1,172,127 square feet with a 215 foot retractable dome. If a terrorist chose sarin as the chemical agent, how much chemical would be necessary to produce mass fatalities? Sarin has an LCT50 of 100 mg min/m3. If wind direction, wind speed, and the problems of dispersing the agent (which are numerous) are ignored, and assuming a homogenous vapor breathed for one minute, then to kill 50% of the attendees would require 860 kg of sarin,3 which is about 781 liters (206 gallons) of pure sarin liquid.

The earlier example scenario ignored several significant factors that decrease a released chemical agent's effectiveness: wind direction and speed, precipitation, chemical purity, and the method of dispersal (see Table 2). Accounting for these factors would likely require a manyfold increase in the necessary volume of chemical.

The method of dispersal of chemical agents also affects the concentration of chemical at the target, and therefore, the consequential fatality rate. During the 1950s and 1960s, many of the world's militaries attempted to solve the problems of volume and environment by producing weapons that would bring the chemicals close to the enemy and then release. Although simple mortars were initially used, more "successful" projectiles were later produced that required technologically advanced mechanisms for release. For example, the "Honest John" rocket (1960) was a medium range rocket that contained about 50 small spherical bomblets. The bomblets contained an explosive central burster with sarin-filled outer compartments. The bomblets' shape initiated a spin that armed the impact fuse (Sidell et al. 1997). Advanced technology weapons such as these are not likely to be obtained or used by terror organizations, although state-sponsored organizations may have such access.

Table 2. Representative factors that may influence the casualty rate of chemical releases.

Another method of dispersal that has been theorized is the direct introduction of a chemical into the air-intake of a large stadium. This type of dispersal may be more difficult to perform than an open- air release, because it requires control of the building and the air- intake system. However, this type of dispersal may require a small, yet still significant volume of chemical. For example, using the simplified model above, producing 50% fatalities in a large hockey or basketball arena would require at least 164 kg (149 Liters) of sarin.4 Again, transportation of this volume of liquid would be difficult without attracting attention, however, a smaller volume could certainly produce casualties without producing large numbers of fatalities.

The volume of chemicals necessary and the complexity of dispersal devices required to produce massive fatalities may be significantly prohibitive for a terrorist organization and be difficult to conceal from authorities. However, releases of smaller amounts of chemical, or from less sophisticated dispersal systems, may produce large numbers of victims exposed to smaller concentrations, or simply produce terror without exposure. Using the earlier sarin analogy (with all of its limitations), it would require only 6.2 gallons of sarin to produce miosis, and therefore blurry vision, in half of the crowd at the example baseball stadium [CT50 (miosis) = 3 mg min/ m^sup 3^]5 and only 1.8 gallons to produce the same effect in a hockey arena. A similar effect may be produced by releasing large volumes of chemical agents into the open air from industrial sites or transportation vehicles (e.g., rail cars) that are not directly within high-density population areas.

WHY DO ASYMPTOMATIC OR MILDLY SYMPTOMATIC PATIENTS PRESENT TO HEALTH CARE FACILITIES?

Historically, after chemical releases, large numbers of people seek medical care at health care facilities (HCFs), such as emergency departments and primary care offices. In the 1994 sarin release in Matsumoto, Japan and the 1995 sarin release in Tokyo, Japan, 80-90% of all patients reporting to the emergency departments had mild or no complaints (Okumura et al. 1996; Morita and Yanagisawa 1995). Similarly, in the 1987 release of anhydrous hydrofluoric acid in Texas, 90% of the 932 patients seen in emergency departments were discharged to home and 15% had no complaints at all (Wing et al. 1991).

Patients with mild complaints or concerns may continue to present to HCFs for several days, even after releases of immediately acting chemicals (Wing et al. 1991; Okumura et al. 1998). For example, after the 1996 Tokyo sarin attack, one hospital received 640 patients on the day of the release. Over the next 6 days, they received an additional 770 patients related to the attack (Okumura et al. 1998). Following the hydrofluoric acid (HF) release in Texas, HF-related complaints continued to be greater than one-fourth of the emergency department volume for more than four days (Wingeiai 1991).

So, why do victims of chemical events present to HCFs when they have few or no symptoms? And why do they present several days after exposure to chemicals that are rapidly acting? To answer these, we must review the various physical and psychological factors that motivate victims to seek care.

Mild Exposure

Patients exposed to low concentrations of chemicals may develop mild, yet irritating or disconcerting symptoms. Many of the chemical agents used by militaries were designed for this purpose. Chlorine, for example, was used extensively in WWI, with its main effect the production of mucosal irritation and incapacitation of enemy troops. Victims of the sarin release in Tokyo also largely developed eye and mucosal symptoms, in that case lacrimation and miosis (Okumura et al. 1996). Although symptoms such as blurry vision may be non- systemic, non-life threatening, and described as "mild" in the health care setting, they are very concerning, worrisome, and irritating to patients. It is important to note that the vast majority of patients report to HCFs for entirely rational reasons; because they either have symptoms or they don't know what symptoms require treatment.

Many patients with mild complaints may report to HCFs hours or days after the release. There are numerous possible explanations for this behavior. Some patients may believe that their mild symptoms will resolve quickly and only present later, when symptoms persist. Others may determine that mild symptoms are tolerable until they can determine and secure the safety of their families. Finally, several chemicals may produce subtle symptoms after low concentration exposure (e.g., nerve agents) (Brown and Brix 1998). These subtle symptoms may not be initially recognized and may be difficult to differentiate from health effects from other diseases, exposures and anxiety reactions (Brown and Brix 1998; Nakajima et al. 1998).

While patients may seek care chronologically distant to the event, for similar reasons they may also present at geographically distant sites, including primary care and obstetrical offices, acute care clinics and distant emergency departments.

Confusion, Anxiety, and Chemical-Phobia

The concept of the domestic use of weapons of mass destruction, either conventional or unconventional, is frightening and anxiety provoking for the general public. Several characteristics of chemical terrorist acts may produce a unique and enhanced sense of vulnerability in the public (Hyams et al. 2002): (1) Terrorist events are involuntary and unpredictable, (2) They may occur in locations that were previously deemed "safe" (e.g., workplace, home), (3) Chemical threats are unfamiliar scenarios, and (4) Chemical events pose a danger to patients' families. Chemical weapons have the additional stigma of being exotic weaponry developed, stored, and deployed by the military with little public knowledge. All of these factors contribute to the significant public anxiety concerning chemical events (Hyams et al. 2002).

The general public does not have a complex understanding of chemical principles and the risks of exposures to chemical agents. Agents are typically concretely divided into "toxic" and "non- toxic" chemicals, of which industrial and military agents are "toxic." Much of the public's knowledge of chemical agents may have been derived from WWI and political propaganda, sensationalistic media reports, and entertainment. One needs only to look at the adjectives used by the media to describe chemicals to understand why the general public is frightened: toxic, killer, lethal, deadly, caustic, and so on. The public has associated these adjectives, as well as images of massive death and suffering, with the release of any chemical. Given this ingrained fear of these "deadly" chemicals, it is difficult to communicate that a low concentration exposure to a "deadly" agent may not produce symptoms or long-term effects. The concept of a dose-response curve for "lethal" agents is not an easy concept when, by definition, the agent is "lethal."

People who feel they may have been exposed to a chemical may seek medical assistance after noticing previously existing symptoms and connecting them to the event. Nonspecific complaints are common in the general population. Approximately 20-30% of people who consider themselves healthy and well, report fatigue or musculoskeletal symptoms when directly asked (Barsky and Borus 1999). In fact, 81% of healthy college-aged students report somatic symptoms over any 3- day period (Barsky and Borus 1999; Reidenberg and Lowenthal 1968). These non-specific symptoms include headache, nausea, dyspnea, paresthesias, problems with memory, palpitations, dry mouth, and lightheadedness, which may be easily attributed to a chemical agent (Barskyand Bonis 1999).

Widespread anxiety and fear of terrorist acts exists in the general population, particularly from unusual, foreign, and "lethal" chemical agents. During a large chemical release, it is likely that a large group of people with a perceived exposure may report to health care workers with symptoms related to anxiety or unconnected nonspecific symptoms. Concerned citizens may view HCFs as safe locations, as well as logical locations for sources of information concerning exotic and unusual chemicals.

Mass Psychogenic Illness

During a chemical disaster, the public's concern of the health effects of exposure may contribute to individual and group symptomatology. This shared anxiety may produce "victims" who require evaluation by HCFs despite not being exposed to a significant amount of chemical. This phenomenon is called mass psychogenic illness (MPI), and is also known as mass sociogenic illness or epidemic hysteria. MPI is defined as a constellation of symptoms that are suggestive of an organic illness, but without an identified cause. The symptoms occur in groups with shared beliefs about the cause of the symptoms (Jones et al. 2000). MPI typically occurs in large groups who are in stressful situations and is commonly brought on by environmental triggers, such as odors (Jones el al. 2000). Suspected chemical releases are a common trigger and several MPI events have occurred after the suspected detection of a "chemical smell" (Wessely e,t al. 2001; Bartholomew and Wessely 2002).

Symptoms in MPI victims are typically nonspecific, such as lightheadedness, headache, nausea, chest tightness, dyspnea, and drowsiness (Jones et al. 2000; Bartholomew 2002; Spitters et al. 1994). MPI symptoms may be easily mistaken for those produced by low concentration chemical exposures. Unfortunately, the misdiagnosis of MPI symptoms as the effects of chemicals may reinforce the patient's symptoms (Barsky and Borus 1999). Reinforcement of MPI symptoms by authorities and health care providers may increase concern in the community and potentially produce additional MPI victims (Barsky and Borus 1999).

The risk and intensity of MPI is higher if the suspected causative factor is foreign to victims (Barsky and Borus 1999), as is the case with most chemical agents and industrial chemicals. Symptoms typically "spread" rapidly and in a pattern that is consistent with "line of sight" spread or via communication lines (e.g., over the telephone), rather than the typical geographical or close personal contact spread of disease or contamination (Spitters et al. 1994). Additionally, there may be asymptomatic people interspersed and juxtaposed with symptomatic people who shared the same "exposure" (Jones et al. 2000).

Several MPI episodes have occurred as a result of concerns of chemical terrorism. During the 1991 Persian Gulf War, it was postulated that Iraq would use chemical weapons against Israel. After several missiles that did not contain chemicals were fired, almost one-half of the residents of an Israeli community reported breathing problems (Carmeli et al 1991). In 1983, 949 people in the West Bank of Jordan reported a variety of nonspecific symptoms over a two-week period. Initial victims detected a sulfur smell in a school (likely a broken toilet). Additional victims occurred due to large-scale media coverage and an underlying fear that Israel had deployed a "poison gas" (Modan et al. 1983). A similar episode occurred in Georgia (Russia) in 1989 when false rumors that the Russian government had used chloropicrin on a crowd led to more than 400 patients complaining of mucosal irritation (Bartholomew and Wessely 2002).

Considering the current anxiety about terrorist events, MPIs can be expected with high frequency in the event of a chemical disaster. Unavoidable vigorous responses from authority, including PPE-clad hazardous materials teams, governmental agencies, and health care personnel, may exacerbate and reinforce MPI symptoms and expand the victim pool (Kovalchick et al. 2002).

Low Concentration Exposure to Chemicals

Symptoms of MPI or anxiety may be quite difficult to differentiate from an exposure to a chemical agent. Several chemicals, including organic phosphorous compounds (e.g., nerve agents, organophosphate pesticides), carbon monoxide, hydrogen sulfide, and ricin may produce nonspecific symptoms without outward physical findings (Brown and Brix 1998). Exposure and toxicity may be determined by identification of the agent at the sight of exposure, by laboratory examination of the patient (e.g., cholinesterase activity/organic phosphorous compounds, carboxyhemoglobin concentration/carbon monoxide, metabolic acidosis/ hydrogen sulfide), and may be predicted using environmental data, plume simulation, and on-site testing.

WHAT TO EXPECT

Large chemical releases have historically produced hundreds of victims who arrive to hospital emergency departments within the first several hours (Okumura et al. 1998). There is typically a brief "ramp up" period between the time of the release and the arrival of the first patients (<1 hour) (Okumura et al. 1998; Okudera et al. 1997). Most patients arrive by foot or private conveyance, and fewer than 20% arrive via police, fire, or EMS vehicle (Okumura et al. 1998). Although the vast majority of patients arriving in the early stages are mildly symptomatic, the most severely affected patients are also likely to arrive at this time (Kovalchick et al. 2002).

After this initial influx of patients, a large increase in volume to hospital emergency departments and primary care offices should be expected over the next week or more (Wing et al. 1991; Okumura et al. 1998). The majority of these victims have complaints that are mild, stress-related, or simply have concerns and request information. Primary care health care workers may see an increase in visits from patients who are concerned about exposure to chemicals that may have entered the food and water supply. Patients may request information about chemical exposures and their risk of long- term medical problems, including cancer. Additional questions should be expected from pregnant patients with concerns about teratogenicity and fetal effects of chemical exposures.

WHAT CAN BE DONE TO PREPARE?

HCFs, including hospitals and primary care offices, should be prepared for an initial influx of patients shortly after an event as well as a sustained increase in volume over several days to weeks. Regional public health plans should consider health care sites that are distant to hospitals and offices to decompress these health care facilities. These regional health care sites should consider the use of a mobile decontamination system, and include a system to triage patients to a higher level of care (e.g., ambulances to transport patients to area hospitals), if necessary. Disaster plans must keep in mind that most patients who seek health care are mildly symptomatic or asymptomatic and that differentiating between symptoms of mild exposure and psychosomatic or unrelated symptoms may be difficult. In certain cases, laboratory evaluation may be available to confirm exposures (e.g., nerve agents) and patients may require additional testing or repeat visits after discharge from HCFs. Additionally, a regional health care plan may include the use of the regional poison center to follow patients at home by telephone and to give educated advice on treatments and the need to be seen in health care facilities. Most importantly, patients initially, and over the short term, require accurate information about the exposure and their expectations for recovery or chronic symptoms (Kales and Christiani 2004; Brennan et al. 1999). Regional disaster plans should include a method of obtaining rapid, accurate chemical and decontamination information, possibly from the regional poison control center, local resources, or federal agencies (e.g., ATSDR, CDC) to distribute to health care workers (first responders, emergency departments, primary care offices, etc.) (Brennan et al. 1999; Greenberg and Hendrickson 2003). The possibility of pre- written data sheets that are rapidly available to health care workers either via fax or electronic media may be considered as most health care workers are not knowledgeable on rare chemical exposures.

Training and education should be considered to address the psycho- social aspects of disaster management. Few HCWs have training on the diagnosis and management of acute and sub-acute psychological reactions. Planning should address the issues of acute exacerbations of chronic psychiatric diseases due to acute stress or limited access to psychiatric medications and counseling, as well as acute disorders in patients without previous psychiatric disorders. Planning may include the identification of caches or storage facilities of common medications that are prescribed for psychiatric problems, including schizophrenia, depression, and anxiety disorders. Planning may include a method of dispersal of these medications to the public or through primary health care workers if pharmacies and hospitals are overwhelmed. Regional groups of psychiatrists, social workers, and psychologists should be included in disaster planning.

Risk communication is a key aspect of any disaster plan and because of the difficult concepts involved and the public's concerns about chemicals in general, is particularly important during chemical exposures. Disaster plans should include rapid access to accurate information about acute and chronic effects of chemicals that are rapidly and clearly communicated at a level that typical citizens may understand. Disaster procedures should allow for communication between regional spokespeople, including the regional poison center, the regional public health agency, hospitals, and the media, so that a coordinated, single message concerning risks and procedures may be communicated to the publi\c (Richards et al. 1999). Rapid and planned communication with the media should be considered to express this coordinated message and to communicate instructions to victims.

Resources for emergency preparedness typically concentrate on the few severely ill patients and the first responders and health care workers who care for them. Additional resources must be used for preparation for the many patients who arrive to HCFs with mild symptoms and are served with minimal medical care, but with accurate and rapid information that is coordinated through HCFs (hospitals, offices), regional poison centers, regional public health agencies, the media, and the regional/national spokespeople (e.g., CDC).

1 LD50 = lethal dose 50%: This is the dose of liquid that would kill 50% of people to whom it was applied.

2 LCT50 = lethal concentration-time 50%: This is the concentration of airborne chemical that would kill 50% of people who breathed it for one minute.

3 Volume of stadium = 1,172,127 ft^sup 2^ 215ft (height of roof) = 130236 m^sup 2^ 66 m = 8,595,576 m^sup 3^.

Kg sarin required = LCT50 Vol = 100 mg min/m^sup 3^ 8,595,576 m^sup 3^ = 860 Kg min.

Liters sarin required = 860 kg l mL/1.1 g (at 20C) (Sidell et al. 1997, p. 141) = 781L.

4 Arena volume = 383,528 ft^sup 2^ 150 ft height = 57,529,200 ft^sup 3^ = 35,649 m^sup 2^ 46 m = 1,639,854 m^sup 3^.

Kg sarin required = LCT50 Vol = 100 mg min/m^sup 3^ 1,639,854 m^sup 3^ = 164 Kg min.

Liters sarin required = 164 kg 1 mL/1.1 g (at 20C) (Sidell et al. 1997, p. 141) = 149 L.

5 Ct50(miosis): This is the concentration at which 50% of exposed patients would develop miosis after exposure for one minute (Sidell et al. 1997).

Volume required in baseball stadium = Ct50 volume of stadium 1 mL/1.1 g sarin = 3 mg min/m^sup 3^ 8,595,576 m^sup 3^ 0.91 mL/g = 23.4 L = 6.2 gallons.

Volume required in hockey arena = Ct50 volume of arena 1 mL/ 1.1 g sarin = 3 mg min/m^sup 3^ 1,639,854 m^sup 3^ 0.91 mL/g = 4.48 L = 1.2 gallons.

REFERENCES

Barsky AJ and BorusJF. 1999. Functional somatic syndromes. Ann Intern Med 130:910-21

Bartholomew RE and Wessely S. 2002. Protean nature of mass sociogenic illness: From possessed nuns to chemical and biological terrorism fears. Brit J Psych 180:300-6

Brennan RJ, WaeckerleJF, Sharp TW, et al 1999. Chemical warfare agents: Emergency medical and emergency public health issues. Ann Emerg Med 34(2):191-204

Brown MA and Brix KA. 1998. Review of health consequences from high-, intermediate-, and low-level exposure to organophosphorus nerve agents. J Appl Toxicol 18(6):393-408

Carmeli A, Liberman N, and Mevorach L. 1991. Anxiety-related somatic reactions during missile attacks. IsrJ Med Sciences 27(11- 12):677-80

Greenberg MI and Hendrickson RG. 2003. Report of the CIMERC/ Drexel University Emergency Department Terrorism Preparedness Consensus Panel. Acad Emerg Med 10(7) :783-8

Hyams KC, Murphy FM, and Wessely S. 2002. Responding to chemical, biological, or nuclear terrorism: The indirect and long-term health effects may present the greatest challenge. J Health Politics Policy Law 27(2):273-91

Jones TF, Craig AS, Hoy D, et al. 2000. Mass psychogenic illness attributed to toxic exposure at a high school. N Engl J Med 342:96- 100

Kales SN and Christiani DC. 2004. Acute chemical emergencies. N EnglJ Med 350:800-8

Kovalchick DF, Burgess JL, Kyes KB, et al. 2002. Psychological effects of hazardous materials exposures. Psychosomatic Med 64:841- 6

Modan B, Swartz TA, Tirosh M, et al. 1983. The Arjenyattah epidemic. A mass phenomenon: spread and triggering factors. Lancet 2 (8365-66): 1472-4

Morita H and Yanagisawa N. 1995. Sarin Poisoning in Matsumoto, Japan. Lancet 346(8970): 290-3

Nakajima T, Ohta S, Morita H, et al. 1998. Epidemiological study of sarin poisoning in Matsumoto City, Japan. J Epidemiol 8(1):33-41

Okudera H, Morita H, Iwashita T, et al. 1997. Unexpected nerve gas exposure in the city of Matsumoto: Report of rescue activity in the first sarin gas terrorism. Am J Emerg Med 15:527-8

Okumura T, Takasu N, Ishimatsu S, et al. 1996. Report on 640 victims of the Tokyo subway sarin attack. Ann Emerg Med 28:129-35

Okumura T, Suzuki K, Fukuda A, et al. 1998. The Tokyo subway sarin attack: Disaster management, part 2: Hospital response. Acad Emerg Med 5:618-24

Ramana Dhara V and Dhara R. 2002. The Union Carbide disaster in Bhopal: A review of health effects. Arch Environ Health 57(5):391- 404

Reidenberg MM and Lowenthal DT. 1968. Adverse nondrug reactions. N EnglJ Med 279:678-9

Richards CF, BursteinJL, WaeckerleJF, et al. 1999. Emergency physicians and biological terrorism. Ann Emerg Med 34(2):183-90

Sidell FR and GroffWA. 1974. The reactivatibility of cholinesterase inhibited by VX and Sarin in man. Toxicol Appl Pharmacol 27:241-25

Sidell FR and Borak J. 1992. Chemical warfare agents: II. Nerve agents. Ann Emerg Med 21(7):865-71

Singh MP and Ghosh S. 1987. Bhopal gas tragedy model simulation of the dispersion scenario. J Hazard Mater 17:1-22

Smart JK. 1997. History of chemical and biological warfare: An American perspective. In: Sidell FR, Takafuji ET, and Fran/ DR (eds), Textbook of Military Medicine: Medical Aspects of Chemical and Biological Warfare, pp 58-9. TMM Publications (Office of the Surgeon General), Washington, DC, USA

Spitters C, DarcyJ, Hardin T, el al. 1996. Outbreak of unexplained illness in a middle school-Washington, April 1994. MMWR 45(1):6-9

Trumpener U. 1975. The road to Ypres: The beginnings of gas warfare in World War 1. J Modern History 47(3):460-80

Varma DR and Guest I. 1993. The Bhopal accident and methyl isocyanate toxicity. J Toxicol Envir Health 40:513-29

Wax PM, Becker CE, and Curry SC. 2003. Unexpected "gas" casualties in Moscow: A medical toxicology perspective. Ann Emerg Med 41 (5):700-5

Wessely S, Hyams KC, and Bartholomew R. 2001. Psychological implications of chemical and biological weapons. BMJ 323:878-9

Wing JS, Sanderson LM, Brender JD, et al. 1991. Acute health effects in a community after a release of hydrofluoric acid. Arch Envir Health 46(3):155-60

Robert G. Hendrickson

Department of Emergency Medicine, Medical Toxicologist, Oregon Poison Center, Oregon Health and Science University, Portland, Oregon, USA

Address correspondence to Robert G. Hendrickson, M.D., Assistant Professor, Department of Emergency Medicine, Medical Toxicologist, Oregon Poison Center, Oregon Health and Science University, Portland, OR 97239, USA. E-mail: Hendriro@ohsu.edu

Copyright CRC Press Jun 2005

Source: Human and Ecological Risk Assessment

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