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

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  • Bruce Tefft
    Terrorist Chemical Releases: Assessment of Medical Risk and Implications for Emergency Preparedness ABSTRACT In the last few years, public health has played an
    Message 1 of 1 , Aug 1, 2005
      Terrorist Chemical Releases: Assessment of Medical Risk and Implications for
      Emergency Preparedness

      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.

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      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@...

      Copyright CRC Press Jun 2005

      Story from REDNOVA NEWS:
      http://www.rednova.com/news/display/?id=192365

      Published: 2005/07/31 03:00:57 CDT

      C Rednova 2004


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