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CHAPTER 2 TRANSPORTATION RESPONSE TO CBR EVENTS This section summarizes the key characteristics of CBR threats (Sections 2.1, 2.2, and 2.3) and then compares these agents (Section 2.4). Sections 3.1, 3.2, and 3.3 focus on threat characteristics that will affect the selection of transportation response options and the development and implementation of a transportation response plan. Each of the threat-specific sections includes â¢ A fundamental description of the threat, â¢ Information needs for emergency response decision- makers, and â¢ Discussion of transportation system vulnerabilities to the threat agent and consequence minimization. Section 2.4 compares the general categories of CBR agents with respect to factors that decide their potential effects on the transportation system. Readers are encouraged to review multiple information sources for better understanding of CBR threats. Because any given source may be very helpful and accurate in many aspects and still have some misleading pre- sentation of factual details, it is important to recognize the general level of information presented and that overall summaries often must generalize for the sake of simplicity and omit qualifying details (e.g., with respect to persistence in specific types of environments, lethality or contagiousness of particular strains, etc.). For another general source for an introduction to CBR threats is The National Academies Fact Sheets on Terrorist Attacks, available on line at http://www.nae.edu/nae/pubundcom.nsf/weblinks/CGOZ- 642P3W?OpenDocument 2.1 CHEMICAL THREATS Familiarity with the basic types of chemicals that may pose threats can aid in developing appropriate emergency response plans. The effects of toxic chemical releases range from irritations to fatality. The chemical agents addressed in this report are those that react chemically with the cells of the human body to cause adverse effects. Types of chemi- cals not included in this report are those that pose their great- est threat by displacing substantial amounts of ambient oxygen during a large release, thereby causing asphyxiation (e.g., methane, nitrogen, carbon dioxide), and flammable 6 agents (i.e., incendiaries), which are most likely to cause harm by burning and creating large amounts of heat (e.g., napalm and ethylene oxide). This section discusses chemical fundamentals (2.1.1), emergency response information needs (2.1.2), and interre- lationships among chemical threats and the transportation system (2.1.3). 2.1.1 Fundamentals Some background information can help in understanding chemical threats. The fundamentals addressed in the subsec- tions below are â¢ Basics, â¢ Events, â¢ Categories, â¢ Doses, â¢ Detection, and â¢ Decontamination More information on chemicals is readily available from many sources, including the Internet. Some of these sources are listed in Appendix A. Basics Thousands of different chemicals pose different threats to humans. Some basic concepts and associated terms used in evaluating a specific chemical toxin are as follows: â¢ Toxicity. This is a measure of the quantity of a sub- stance required to get a harmful effect. Depending on the type of harmful effects cause by the chemical, a highly toxic chemical may or may not be likely to cause death. â¢ Lethality. This refers to how much of a substance is needed to cause death. Not all chemical weapons are de- signed to maximize lethality (e.g., riot-control agents, which are designed to incapacitate, but not kill, the target). â¢ Exposure route. Exposure routes are the pathways by which a chemical may enter the body. The most common
exposure route for both chemical weapons and an indus- trial chemical release is inhalation, followed by skin absorption. The final exposure route, ingestion, may occur with contamination of food and water supplies and to a much lesser extent with inhalation of particles. â¢ Speed of action. This refers to the delay between expo- sure to a toxin and the beginning of symptoms, which varies from split-seconds to hours. â¢ Persistence. This refers to the length of time the chem- ical remains toxic after release. Loss of toxicity may be caused by dilution, as when a gas is dissipated by the wind, or chemical breakdown from various chemical reactions that may occur with water, oxygen, and light. The military defines a chemical as non-persistent if it is likely to evaporate or break down from a ground surface in less than 24 hours at temperatures of 60 to 80 Â°F. Most if not all, commercial chemicals carried in bulk (e.g., chlorine, ammonia, and hydrogen fluoride) are non-persistent. â¢ Dose. A dose is the amount of a chemical taken into the body and depends on the chemical concentration, the duration of exposure, and the route of exposure. The quantity of a chemical needed for a dose to yield harm- ful effects depends on the chemical toxicity and the ex- posure route. Events From an emergency response perspective, understanding where, what type, and how much chemical contamination has been released are the key issues for decision-making in the event of a chemical threat. The cause of the chemical release is, in many cases, likely to be a secondary issue for response management unless it suggests an increased possi- bility of a second release. However, recognition of the types of chemical events that may occur can assist in both assess- ing regional vulnerabilities and in developing scenarios for emergency training and exercises. Two basic types of chem- ical releases are described below. â¢ Chemical Infrastructure Event. Chemicals may be re- leased from any of the thousands of facilities in the United States that produce, handle, use, and store chem- icals, or chemicals in transport between these facilities. Two types of release events that have received substan- tial attention and response planning are â Chemical plant incidentâinvolves the accidental or deliberate release of dangerous levels of chemicals from one or more of the 66,000 chemical facilities in the United States. The FBI has long warned that at- tacks on an industrial facility may come from a local or disgruntled employee, just as the 1984 Bhopal in- cident appears to have been a result of human error or sabotage by a demoted employee. In an extreme 7 event, such as occurred in Bhopal, India, a radius of tens of miles and the health of many thousands of people may be threatened. â Chemical transportation incidentârefers to an acci- dental or deliberate release of chemicals that are in transport. Large quantities of chemicals are trans- ported in special containers, which, if breached, can result in a significant chemical release. This may occur inadvertently, such as in the case of the recent (February 2004) runaway train in Iran, which de- railed and released sulfur, petrol, and fertilizer before an explosion that killed more than 300 on- lookers. In a deliberate release, a vehicle or vessel may be attacked or hijacked and driven to a densely populated area before the chemical release to maxi- mize injury and destruction. â¢ Chemical Weapons Event. Refers to the use of chemi- cal weapons agents that may have been produced by a government or by terrorist organizations. Precursors for the chemical weapons may be obtained legally or ille- gally. Large quantities of chemical weapons are more difficult to obtain than industrial chemicals, thus re- leases of chemical weapons in crowded enclosed spaces (e.g., subway or airport), where a small amount may be effective is a more likely terrorist scenario than an open- air release. In general, a serious chemical event may result in hundreds to a few thousand casualties and in thousands of permanent injuries. As large as the magnitude of these consequences seems, it is not as great as could occur from a serious radio- logical or biological event, which are addressed in other sections of this report. Categories Many methods exist for grouping or categorizing the many thousands of chemicals available. OSHA and DOT use a similar classification of chemicals based on the type of physical hazard posed (e.g., explosives, flammable liquids, and corrosives).1 The OSHA/DOT classification system typically is used to describe chemicals involved in chemical infrastructure incidents, either at a chemical facility or dur- ing transport. However, when chemicals are intentionally used to threaten people, they are referred to as chemical weapons and spoken of in terms of their military classifica- tion. The military classification system is based on the human symptoms the agent causes (e.g., choking, blister, and nerve). Many of these weapons classes were first used in World War I. The most common classes of chemical 1 The Department of Transportation Emergency Response Guidebook, 2004, de- scribes this classification system and can be viewed or downloaded from links provided at http://hazmat.dot.gov/pubs/erg/gydebook.htm
weapons that have proliferated since WWI are described below: â¢ Choking agents. Inhalation is the typical exposure route for choking agents, also called ârespiratoryâ or pul- monaryâ agents. They are lung irritants that cause fluid build-up in the lungs, which can result in suffocation as much as 24 hours after exposure. Although choking agents are no longer common as military weapons, many choking agents are common industrial chemicals, and their release from an industrial facility or during bulk transport can have devastating effects. Histori- cally, chlorine and phosgene have been the most used chemical weapon choking agents and are currently mass-produced by the chemical industry. Some chok- ing agents are gases at standard temperature and pres- sures (e.g., chlorine and phosgene); others are liquids that are most dangerous as aerosols (e.g., diphosgene). Choking agents generally dissipate relatively easily under many open-air circumstances so typically are not persistent. â¢ Blister agents. These agents cause serious skin and eye irritation. Blister agents, also referred to as âvesicants,â are the most widely used and stockpiled chemical weapon. Although blister agents can cause death, they are not considered very lethal. They are used primarily to cause substantial distress, put demands on the med- ical system, and incite general public fear. Blister agents include sulfur mustard, nitrogen mustards (e.g., HN-3), and Lewisite. They are low-cost and relatively easy to mass produce. Although eye irritation often occurs within minutes, the development of noticeable skin irri- tation varies from seconds for Lewisite, to hours for mustard agents. Many blister agents will persist on surfaces for days in the summer and, depending on the temperature, may persist for weeks in the winter. In soils, persistence may be longer. Blister agents can seep through fabric, rubber, and leather, so first-responders and decontamination crews require special protective clothing. â¢ Nerve agents. These organophosphate chemicals are liquids at standard temperatures and pressure. Exposure routes are inhalation and skin contact, depending on the dispersion method (i.e., size of aerosol droplets), and their rate of evaporation after settling. Nerve agents paralyze the respiratory muscles and can cause death within a few minutes when inhaled, whereas a drop on unprotected skin may take several hours to produce se- vere symptoms and possible death. Some of the more common chemical weapon nerve agents are sarin, tabun, soman, and VX. They vary in persistence from a few hours for sarin to days or weeks on surfaces (i.e., potential skin exposure) for agents such as VX. Nerve agents require more sophistication to produce 8 than blister agents, but have been produced and used by terrorists (i.e., sarin was used in 1995 by the Aum Shin- rikyo cult in Tokyo). Some nerve agents have been used along with blister agents for a broader scope of effects. â¢ Blood agents. These toxins typically are taken into the body by inhalation and act by blocking oxygen use or uptake from the blood, thereby causing suffocation. Hence, blood agents are also called âchemical as- phyxiants.â Some of the more common blood agents are hydrogen cyanide (the active ingredient in Zyklon B), hydrogen sulfide, and cyanogen chloride. These agents are highly volatile and difficult to store and have a low persistency on release. However, they are also very lethal and act very quickly. Agents such as hydrogen cyanide are easily produced from common industrial chemicals and therefore may attract terrorist interest. â¢ Riot-control agents. These include pepper sprays and tear gases (e.g., CS and CN, both of which are actu- ally solids at standard temperature and pressure). They irritate the eyes, nose, and mouth, initially mim- icking other chemical weapons agents. CS is favored for large-scale riot control because of its low toxicity and short-term effects (5 to 15 minutes). Although they are not generally lethal unless ingested in high doses, riot control agents can cause extreme discom- fort and panic, which can lead to lethal events. Fur- thermore, in enclosed areas, fine particles from some riot control agents may facilitate explosions similar to grain elevator explosions. Other, less common chemical weapons classes include vomit agents and incapacitants (i.e., psychoactive chemicals). Non-toxic chemical agents, such as obnoxious odorants, can be used to harass or mask other toxic compounds. In recent years there have been more than one hundred cases of ânox- ious chemical vandalismâ on abortion clinics throughout the United States. The chemical agent in these events was butyric acid, which produces a rancid butter odor, can irritate skin and eyes, and requires much effort to remove the odor. With the classification of these cases as vandalism, terrorism experts generally believe that nerve and blister agents are the most likely chemical weapons to be used by government-defined terrorists. In addition to chemical weapons agents, numerous indus- trial chemicals at both fixed sites and during transport may be attractive to terrorists. Based on available sources, FBI in- vestigations, product availability, and the complexity of manufacture and development, the FBI has developed a list of industrial chemicals potentially attractive to terrorists (Table 2-1). Appendix A contains a list of other organiza- tions that have similar lists of chemicals of concern and a summary table of specific characteristics of several potential chemical agents
Doses and Concentrations of Concern The specific dose of a chemical that is received is not easily measured, unless the chemical is given in a carefully measured way. This is because the amount of a chemical taken into the body can vary among individuals. For example, the dose re- ceived of a blister agent may vary with the type of clothing an individual is wearing. Therefore, exposure to chemicals in the environment is often discussed in terms of exposure concen- trations rather than doses. Chemical concentrations of concern vary depending on the situation being addressed. For example, in an office workplace, the amount of ozone that causes 50 percent of the employees to have burning eyes for several hours every workday is a serious issue. However, in a chemical weapons event, this same effect is not generally consid- ered serious (although the event may be considered seri- ous as an indication of possible future, more harmful events). The many different concentrations of concern for chemicals reflect the differences in levels of effect that are a concern. Concentrations of concern are based on a specific effect (e.g., discomfort, serious injury, or death), within a specific time (e.g., immediate, 10 minutes, 96 hours), in a specific percentage of the population (e.g., 1 percent, 10 percent, 9 or 0 percent). Concentrations of concern are established by government agencies (e.g., OSHA, DOE, or EPA) and in- dustry associations on the basis of multiple studies. In a chemical release event, concentrations that cause long- lasting health effects from short-term exposures are a primary reference for response management. Table 2-2 displays concentrations as parts per million (ppm) of several chemicals. The concentrations shown are Acute Exposure Guideline Limits (AEGLs) established by EPA. AEGL-2 concentrations are airborne concentrations above which the general population could experience irreversible or long- lasting serious health effects, or an impaired ability to es- cape. AEGL-3 concentrations are airborne concentrations above which the general population could experience life- threatening health effects or death. The smaller the AEGL, the smaller the amount of the material that needs to be re- leased to cause dangerous health effects to people within a given area. Appendix A describes other chemical concen- trations of concern. Chemical Detection Identification of chemicals involved in chemical infra- structure incidents can often be determined from OSHA- and Ammonia Arsenic Arsine Boron Trichloride Boron Trifluoride Butyric Acid Carbon Disulfide Chlorine Chloroacetone Cyanides Diborane Dimethyl Sulfate Dimethyl Sulfoxide (DMSO) Ethylene Oxide Fluorine Formaldehyde Hydrogen Bromide Hydrogen Chloride Hydrogen Fluoride Hydrogen Sulfide Mercury Methyl Phosphonyl Dichloride N,Nâ-Dicyclohexyl carbo-dimide (DCCDI) N,Nâ-Diisopropylcarbo-diimide (DICDI) N,Nâ-Dimethylamino Phos- Phoryl Dichloride Nitric Acid Phosphine Phosphorus Trichloride Sodium Azide Sodium Fluoroacetate Sulfur Dioxide Sulfuric Acid Thallium Thiodiglycol Thionyl Chloride Tributylamine Tungsten Hexafluoride 2-(Diisopropylamino) ethane thiol 2-(Diisopropylamino) ethanol Reproduced from the FBI Community Outreach Program for Manufacturers and Suppliers of Chemical and Biological Agents, Materials, and Equipment (http://www.aiche.org/ccps/pdf/fbi_wmd.pdf). This list is by no means complete. Other lists of potentially attractive chemicals are provided in Appendix A. TABLE 2-1 FBI Community Outreach Program List of Potentially Attractive Chemicals for Terrorist and Criminal Activity TABLE 2-2 Examples of Acute Exposure Guidelines for Inhalation Chemical AEGL-2 (ppm) AEGL-3 (ppm) 10 min 1 hr 8 hr 10 min 1 hr 8 hr Ammonia 270 110 110 2,700 1,100 390 Chlorine 2.8 2.0 0.71 50 20 7.1 Hydrogen Cyanide 17 7.1 2.5 27 15 6.6 Sarin 0.015 0.006 0.002 0.064 0.022 0.009 Sulfur Mustard 0.09 0.02 0.002 0.59 0.32 0.04 (Source: EPAâs National Advisory Council/AEGLs website at http://www.epa.gov/oppt/aegl/chemlist.htm)
DOT-required labeling and tracking. In a chemical facility incident, first responders may be able to identify the chemi- cal based on community preplanning lists of hazardous chemicals at specific locations. In addition, emergency personnel should be alert to other obvious locations in their communities that use hazardous materials, such as laborato- ries, factories, farm and paint supply outlets, and construc- tion sites. In a chemical transportation incident, cargo chemical identity can be determined from â¢ Container Shape. DOT regulations dictate certain shapes for transport of hazardous materials. â¢ Markings. Transportation vehicles must use DOT mark- ings, including identification (ID) numbers, located on both ends and sides of all cargo tanks, portable tanks, rail tank cars, and other small packages that carry haz- ardous materials. â¢ Placards and Labels. These convey hazard class infor- mation by use of colors and symbols, and either hazard class wording or four-digit identification numbers. Plac- ards are used when hazardous materials are in bulk such as in cargo tanks; labels designate hazardous materials on small packages. â¢ Shipping Papers. These provide the same information as on placards and labels. Such papers also provide to the shipper name, quantity of material, and general emergency response instruction. Shipping papers must accompany all hazardous material shipments. â¢ Senses. Odor, vapor clouds, dead animals or dead fish, fire, and irritation to skin or eyes can signal the presence of hazardous materials. After a chemical has been identified, information on how to respond can be found in various references, such as Material Safety Data Sheets (MSDS), the DOT Emergency Response Guidebook, and the CHEMical TRansportation Emergency Center (CHEMTREC) web page (http://www.chemtrec.org/ Chemtrec/), in addition to the shipping papers. Thus, there are several sources of on-scene information for chemical events involving a chemical facility or chemi- cal transportation. In contrast, none of this information would be available during a chemical weapons event. Regional HazMat teams should be equipped with Technical Operations Modules, or science and control units that con- tain chemical detection equipment such as chemical detec- tor system kits; programmable chemical agent detectors; and M256A1 Chemical Agent Detector Kits. HazMat teams may also have multigas meters, organic vapor analyzers, and gas chromatograph/mass spectrometers. If the HazMat team cannot identify the chemical in question, the incident com- mander probably will be able to call on the services of local laboratories (e.g., in universities) for assistance. These var- ious detectors can also be used during chemical facility and chemical transportation incidents. 10 Chemical Decontamination The need for decontamination of chemical agents depends on their concentration and persistence. There is no generally accepted guide on large-scale chemical decontamination methods. Thus, when persistence is long enough to consider active decontamination, controversy is likely. The trade-off between passive decontamination (i.e., isolating the con- taminated area and allowing the contaminant to degrade or become diluted naturally) and active decontamination (i.e., taking action to degrade or dilute the contaminant to safe levels) will be affected by the location and size of the contaminated area, the affected population and economy, and the persistence of the chemical agent and the hazards as- sociated with decontaminating agents (e.g., chlorine). Blood agents such as hydrogen cyanide, arsine, and cy- anogen chloride are chemical asphyxiants that evaporate rapidly in the environment, generally precluding the need for decontamination actions. In enclosed conditions where de- contamination may be needed, both respiratory support and protective clothing are needed, because these agents may also be absorbed through the skin and eyes. In contrast, blister agents are very persistent at cold tem- peratures. However, at warmer temperatures, evaporation rates increase causing higher vapor concentrations that pre- sent inhalation as well as skin absorption hazards. Many of these agents are inactivated gradually by sunlight, increasing the rate of their degradation in outdoor versus indoor envi- ronments. There are exceptions however, Lewisite is both stable below about 120 oF and is not inactivated by sunlight. The primary mode for active decontamination of blister agents has been copious amounts of water with a 0.5% hypochlorite solution (1 part bleach, 9 parts water). Protective respiratory support and clothing must be worn by trained per- sonnel. Phosgene oxime is unique among the blister agents in that it may be chemically inactivated using an alkali. Nerve agents such as sarin, soban, and tabun evaporate and loose their toxicity within minutes to days, depending on tem- peratures. The need for active decontamination is increased for nerve agents that are slower to evaporate (i.e., soman, GF, and VX). For active decontamination of nerve agents, water has been used. Nerve agents are organophosphates, which is the same chemical family as many common pesticides (e.g., chlor- pyrifos, diazinon, disulfoton, malathion, sevin, etc), thus water run-off containing these agents may pose hazards for both en- vironmental and human health. Both nerve and blister agents may be thickened into an oily liquid that can remain on surfaces as a persistent hazard. When the agents are thickened, a soap and bleach solution is used. In both cases, protective clothing and respiratory protection are needed during the clean-up. The use of large quantities of chlorine (i.e., bleach), in particular, may be subject to EPA and similar state require- ments. These requirements may include containment of run- off, measurement of water quality, and possible sustained
holding of run-off water with more treatment until accept- able levels of both the initial contaminant and any added de- contaminants (i.e., chlorine and soap) are reached. 2.1.2 Emergency Response Information Needs Regardless of the cause of a chemical release, from an emergency response perspective, the primary considerations for response management are the chemical type and toxicity, quantity and persistence, exposure route; and dispersion and population density in the area at risk. These factors and their interrelationship are discussed below. Table 2-3 delineates some of the information needed in a chemical event to decide the appropriateness of transportation goals for isolation, shel- ter-in-place, evacuation, and checkpoint establishment. Chemical Type and Toxicity Chemical type and toxicity are key factors in assessing the threat posed to human health, thus is important for determin- ing appropriate protective wear for first-responders and clean-up personnel, and population risks. The health risks to responders and the general population are also affected by the contaminant concentration (derived for the initial quan- tity and area of dispersion) and the exposure route. In popu- lated areas, the general type of a released chemical can often be assessed within minutes of release because of the rapid onset of symptoms. Most industrial transport chemicals are choking agents or asphyxiants. In non-industrial events, mul- tiple agents may be released, and a more common agent, such as tear gas, initially may mask the presence of another agent, such as the blister agent mustard gas, for which symptoms other than those similar to tear gas may be delayed for several hours. 11 Quantity and Persistence The quantity of a chemical released and the chemical type and toxicity determine the potential human health effects. The quantity and persistence of the released chemical deter- mine the duration of the human health risk. An upper range estimate of the quantity of a chemical release from an indus- trial storage or transport container can be determined easily on the basis of container size and can assist in developing a conservative estimate of the area that may receive concen- trations of concern. The larger volumes of chemicals in trans- port are in railcars, with amounts up to 90 tons per car, and on inland and coastal barges in amounts up to 2,500 tons per barge. These containers may be particularly attractive from a terrorist perspective because of the possibility of very quickly releasing large quantities of a toxic chemical. Toxic gases (transported as both gases and as liquids under pres- sure) are generally not very persistent, so typically present only a short-term threat. Estimating the release quantity and associated area with concentrations of concern may be more problematic from a chemical weapons release, particularly if there is a delay be- tween exposure and observable symptoms. Particularly among blister and nerve agents, the persistence of chemical toxicity after release varies greatly (i.e., from minutes to weeks). The identification of a chemical weapons release agent needs to be confirmed with laboratory tests to estimate confidently its persistence and the protective wear needed during clean up. Exposure Route Possible exposure routes are determined by whether the chemical is a gas, liquid, or solid. If it is one of the latter two forms, aerosol or particle size and evaporation rate must also be considered. Inhalation is the primary exposure route of concern for choking agents and for some nerve agents (e.g., sarin). In a severe release, inhalation may also be an im- portant exposure path for some blister agents. The time re- quired for an agent suspended in air to be diluted, and for par- ticles and aerosols to settle to the ground and evaporate, determines how long inhalation is a concern. The size of the particles is critical in that if the particles are too large, they quickly fall to the ground and no longer pose a threat through the inhalation exposure route. Table 2-4 provides estimates Chemical Event Information Needed to Determine Appropriate Emergency Response Estimated population exposed to levels of concern as determined from: Affected area information (see below) Population data Estimated affected area as determined from: Quantity and toxicity of material Release parameters (density, temperature, momentum, etc.) Location of release Wind direction and speed Topography, urban or rural environment Levels of concern (i.e., toxicity) Possible exposure pathways as determined from: Chemical identity Physical form (gas, liquid, solid) TABLE 2-3 Determination of Chemical Event Emergency Response TABLE 2-4 Particle Size and Sedimentation Rate in Stagnant Air Particle Diameter Time to Fall 100 Ft. 100 microns 2 minutes 10 microns 3 hours 3 microns 30 hours 1 micron 240 hours 0.5 microns 820 hours
of how long it takes various particle sizes to settle to the ground when there are no wind currents. The smaller the particle, the further it may travel within the respiratory tract. In general, particles greater than 10 m (mi- crometers, also called microns) in diameter are trapped by nasal hairs and released with exhaled air or sneezing. Parti- cles less than 10 m in diameter are referred to as âinhalableâ because they may pass into the upper portions of the lungs, which contain many branched passageways. These passages (bronchi and terminal bronchioles) are lined with mucus and cilia. The mucus traps particles, and the cilia gradually push the mucus and its contents up and out of the lungs within about a day. Chemical agents trapped in the mucus are then swallowed, entering the digestive tract. The smallest parti- cles or aerosols (e.g., less than 2.5 m diameter) are referred to as âfineâ or ârespirableâ particles. Fine particles may pass into the deepest portions of the lungs (i.e., respiratory bron- chioles, alveolar ducts, and alveolar sacs) where they may dissolve or be removed by macrophages over many days. The unaided human eye can discriminate individual par- ticles down to the size of 30 microns. These particles will be trapped by nose hairs and mucous and blown out or swallowed before reaching the lungs. To put particle sizes in perspective, particle size of commonly used substances are presented in Table 2-5. Absorption through skin is the primary exposure route for some chemical weapons agents (i.e., essentially all blister agents and some nerve agents). Many of the agents for which the skin is a primary exposure route are oily liquids. Aerosol droplets too large to be readily respired are a common means for dispersal of these agents. Droplets of some of these agents (e.g., VX) can take weeks to evaporate or break down to less toxic forms. Many common fabrics provide protection from skin absorption of some agents (e.g., the blister agent phos- gene oxime), but provide little protection from other agents (e.g., sulfur mustard). Ingestion of chemical toxins may occur with tainted drink- ing water or food. An effective chemical toxin release in the drinking water supply of a city-sized population gener- ally is not viewed as a credible threat by terrorism experts be- cause of the quantity of an agent needed and the degradation of chemicals that results from standard water disinfection processes. However, a chemical attack on post-purification drinking water storage in a small municipality or a specific building is viewed as more credible, but difficult to get without site-specific knowledge and access. By extension, intentional chemical contamination of passenger drinking 12 water within the transportation system is possible, but prob- ably would not be a very large event in terms of injuries or casualties. Food contamination with toxic chemicals is also possible. Although only isolated cases of intentional food poisoning have occurred, several single accidental food poisoning events within the last decade have sickened thousands of peo- ple, suggesting the potential effects that could be achieved with intentional food poisoning. Dispersion, and Population Density The density of the population in the area at risk affects the means for communicating instructions and the choices of transportation-related responses. The number of individuals at risk during a chemical event depends on the population density and the area over which health-threatening levels of contamination are dispersed. Health-threatening levels are determined by the type and toxicity of the chemical and the exposure route. Dispersion is determined from the physical form of the chemical (i.e., gas, liquid, solid, or particles), topology and meteorology (i.e., rain and wind currents), and the quantity released. One of the more common worst-case scenarios of a chem- ical incident involves the release of a chemical that is a gas under ambient conditions, but is transported as a liquid under pressure in 90-ton railroad tank cars. A release from one of these cars carrying chlorine or ammonia has been projected to create a danger zone in the range of 14 milesâin a highly urbanized area, such a release could affect millions of peo- ple. When pressurized liquids are released, part of the liquid immediately flashes to a gas, forming a vapor cloud. The re- mainder may be fragmented into fine liquid droplets (i.e., an aerosol), which will soon evaporate. Depending on the re- lease conditions, some of the liquid may form an evaporat- ing liquid pool on the ground. The highly turbulent nature of these releases facilitates mixing with air. Within a minute, the cloud typically consists of air with a few percent of the released chemical. The vapor cloud is heavier than air, caus- ing it to slump to the ground, becoming a broad cloud that backs up against the wind. Within a few minutes, a release of common bulk transport quantities of a liquefied gas (i.e., 20 to 90 tons) can cause a vapor cloud with a backup of several hundred meters and a width of a kilometer or more. Depending on atmospheric conditions, the size of the release, and the toxicity of the released gas, the area of concern may Substance Individual Particle Size (Microns) Inhalable / Respirable Beach sand 74 to 187 No Table salt crystal 100 No Powdered confectionerâs sugar 10 Inhalable Talc powder 1.5 to 37 Inhalable and Respirable Tobacco Smoke 0.5 Inhalable and Respirable TABLE 2-5 Individual Particle Size of Commonly Used Substances
soon extend as much as tens of miles downwind before grad- ually falling below the concentrations of concern. Heavy vapor clouds also tend to run into depressions, ditches, drains, and basements of buildings (if released in an urban area). They can persist there for several hours if the wind speed is low or if enclosed spaces are not well ventilated. This can be dangerous for unwary members of the public and emergency rescue personnel. Computer models such as RMP*Comp (Risk Manage- ment Plan offsite consequence analysis software) (EPA, 2004) are used to predict the area over which a toxic cloud may spread. These models generally are conservative, so the distance over which a cloud would cause harmful effects in the field would often be less than predicted by the models. Atmospheric conditions such as inversions may have a sub- stantial effect on the dispersion of toxic gases. An inversion is considered the optimum condition for an open-air chemi- cal weapons release. Inversion occurs when the ground is cooler than the air, and temperatures increase further from the ground. Under these conditions, there is little air turbu- lence and wind speeds are low, thereby reducing the rate of dispersion of a chemical release. The 1984 release of methyl isocyanate (a choking agent) at a pesticide factory in Bhopal, India, occurred during an inversion, which had slow but steady winds. The toxic cloud moved to a densely populated area where it killed more than 2,500 people and caused tens of thousands of permanent respiratory injuries. Similar to gases, aerosols and fine particles from chemi- cal weapons may be dispersed by natural wind and wind generated from traffic. In contrast to gases, particles dis- persed by wind eventually will be deposited onto surfaces. The atmospheric dispersion of small particles and aerosols is affected by many factors, such as energy in the dispersion (i.e., fire, heat, or explosion), height of release, presence of obstructions (e.g., buildings, hills, and mountains), and weather conditions (e.g., wind speed and direction, temper- ature, humidity, rain, and cloud cover). The most important factors are wind speed, wind direction, energy and height of release, and the presence of obstructing structures or natural features. Re-suspension of particles with traffic-generated wind is possible but most of the chemical agents are gases or aerosols for which re-suspension is not generally an issue. Spilled liquid chemicals will form a slowly evaporating pool on the ground. The rate of evaporation is affected by factors such as the boiling point of the liquid, ambient tem- perature, the area over which the liquid spreads, and the wind speed. The Aum Shinrikyo cult used an evaporating liquid to release a few liters of the nerve agent, sarin, in commuter trains on three Tokyo subway lines in 1995. The sarin was concealed in lunch bags and soft-drink containers, and placed on subway train floors. The containers were then punctured with umbrellas, spilling sarin on the floor as the perpetrators left the trains (Ohbu et al., 1997). The incident resulted in 12 deaths and about 1,000 injuries. Pouring liquid nerve and blister agents on the ground or floor is a relatively inefficient 13 way of dispersing them. If terrorists were able to obtain or manufacture chemical munitions, they could cause a more devastating effect. The use of crop duster planes to disperse chemical weapons agents is considered to be possible, but very un- likely. Without substantial reconfiguration, crop-dusters can only release liquid droplets that are much larger than can be taken into the lungs, thus only agents that cause injury by contact could be effective. Blister agents and the nerve agent, VX, have been identified as potentially able to be ef- fectively dispersed with a crop duster. Difficulties would in- clude preventing leakage (for VX in particular, even minimal exposure would kill the pilot before leaving the ground) and infiltrating both a crop duster company and one of the traditionally separate, specialized companies that load chemicals into crop dusters. 2.1.3 Threats and the Transportation System The transportation system has particular vulnerabilities with respect to chemical threats and, as discussed below, is likely to be involved in actions to minimize the consequences of a chemical event. Transportation System Vulnerabilities A chemical release event that occurs near or in any transportation mode can contaminate the roadway or track on which vehicles travel, transportation vehicles, passen- gers, and cargo passing through the contaminated area. Factors that make a transportation mode more vulnerable to sustained toxic concentrations during a chemical event include the presence of enclosed spaces, the likelihood of persistent contamination, and the ease (or difficulty) of de- contamination. These factors and other vulnerability fac- tors are summarized in Table 2-6 for each transportation mode. Enclosed spaces such as tunnels and, to a lesser extent, road and track surrounded by tall buildings, may more read- ily retain toxic vapors, aerosols, and particles than open spaces. Gaseous and aerosol chemicals may enter vehicles and vessels with air, and in all transportation vehicles, may be more readily retained in passenger and cargo compart- ments than in the open air. Factors that reduce the ability for quick dilution of toxic gases or aerosols (e.g., enclosed spaces) allow people and cargo to receive larger doses, thereby increasing health effects. Among the largest public populations at risk in enclosed spaces are in transit under- ground stations or terminals, airport terminals, large civil aircraft, and passenger cruise ships. Enclosed spaces with HVAC systems have increased exposure risks caused by continued circulation of toxic chemicals in the form of gases, aerosols, or fine particles. Food and water cargo present
concerns as both a primary target for contamination and as transportation system cargo that has passed through a conta- minated area. Toxic particles and, to a lesser extent, aerosols, can be re-suspended or evaporated more quickly by air currents gen- erated by passing traffic. In the contaminated area, highway vehicles and rail or subway cars in particular can expand the contaminated area. Contaminant spread by traffic could also be an issue in ports, docks, canals, and rivers. The open sea, however, is not susceptible to significant chemical contami- nation from passing ships because its enormous volume would dilute any toxins to an insignificant concentration. Intersecting modes of transportation can result in cross- contaminating one transportation mode from another. Primary mode intersections include rail crossings, stations, airports, ports and docks, and mass transit lines and/or stations. This physical proximity can result in contamination spreading from one transportation mode to another. Consequence Minimization of a Chemical Event The first response in the event of a chemical release that contaminates transportation pathways would be to close the affected paths until a non-persistent chemical is diluted or chemically broken down or until a persistent chemical is otherwise removed. Depending on the released agentâs persistence, potentially contaminated people, vehicles, and associated cargo may be routed to isolation and decontami- nation areas or directly to medical assistance. Transportation would need to be provided for first responders to assist 14 trapped or injured people. For rapid response in the event a chemical weapons agent is detected in association with an explosion, emergency response plans may specify an imme- diate, conservative radius surrounding the explosion site for evacuation. These boundaries may be adjusted after a more complete chemical survey. A difficult and probably contro- versial aspect of determining transportation response goals will be in establishing the physical boundaries of isolation areas. Transportation officials are unlikely to have primary responsibility for these decisions and probably will be fol- lowing instructions from the emergency operations center. In the event of a persistent chemical release, successfully routing all potentially exposed traffic to decontamination areas depends on the time it takes to recognize that a chemi- cal weapons agent has been released. Symptoms from most chemical agents appear within minutes, but in the case of de- layed detection of a release, effort may be needed to identify, decontaminate, and provide medical assistance to contami- nated travelers, vehicles, and cargo after they have left the area of initial contamination. In some outdoor release cases (e.g., blister agent or VX), it may be safer for people to remain inside buildings (i.e., shel- ter-in-place) than to evacuate. In other cases, such a distant re- lease of a large amount of a choking agent that may travel to a populated area, population evacuations may be necessary. In these cases, transportation paths may be re-routed to expe- dite one-way travel. If the people, vehicles, and cargo from evacuated areas have the possibility of being contaminated with a persistent chemical, isolation and decontamination stops would be established along evacuation routes. Essen- tially all modes of transportation may assist in population Chemical Vulnerability Highway Rail Transit Aviation Maritime Enclosed space â¢ Tunnels â¢ Passenger compartments â¢ Tunnels, â¢ Stations â¢ Passenger compartments â¢ Tunnels â¢ Stations/terminals â¢ Passenger compartments â¢ Aircraft â¢ Terminals â¢ Cruise ships â¢ Terminals Persistent contaminationa High for passenger vehicles High High for aircraft and airports High for cruise ships, and terminals Ease of decontaminationa Moderate Moderate Moderate Moderate Moderate HVAC spread contamination None Within passenger car or station Within passenger compartments, terminals Within airports and aircraft Within cruise ship and terminals Drinking water contamination None Passenger drinking water Passenger drinking water Passenger drinking water Passenger drinking water Agricultural cargo contamination Yes Yes No Slight Yes Able to contaminate other modes Transfer points Transfer points Transfer points Airport terminal Dock a: Persistent contamination and decontamination are only issues when a persistent chemical is released (i.e., some chemical weapons agents). High for stations, passenger trains TABLE 2-6 Vulnerabilities to Extended Chemical Exposure for Each Transportation Mode (Note: High more vulnerable (higher risk), Medium medium vulnerability, Low less vulnerable (lower risk))
evacuations, as well as in the transport of first responders and provision of emergency response supplies. Any transportation modes with large buildings may be considered for use as tem- porary shelters. 2.2 BIOLOGICAL THREATS Familiarity with the fundamentals of biological agents can be useful in developing appropriate emergency response plans. Depending on the particular biological agent, effects range from sickness to death, and treatment of infections range from administration of vaccines and antibiotics that may prevent or destroy the infection to simple supportive care to keep infected people as comfortable as possible while their bodies fight the infection. This section addresses bio- logical organisms that may pose either a human health threat or an agroterrorism threat and toxins produced by biological organisms. Subsections are fundamentals (2.2.1), emergency response information needs (2.2.2), and biological threats and the transportation system (2.2.3). 2.2.1 Fundamentals This section provides background information for better understanding of biological threats. The fundamentals ad- dressed below are â¢ Basics, â¢ Events, â¢ Dose and infectivity, â¢ Categories, â¢ Detection, and â¢ Decontamination. More information on biological threats is available from many commonly available sources, including the Internet. Basics There are three general types of biological threat agents: bacteria, viruses, and toxins produced by biologi- cal organisms. â¢ Bacteria are single-celled organisms that have a cell wall, cell membrane, and DNA found throughout the cell, rather than in a compartment (i.e., they do not have a nucleus, as in plant and animal cells). Bacteria repro- duce by division and are commonly cultured in broth or on a nutrient gel. When bacteria establish themselves and replicate in the human body they can cause disease. Some bacteria can form spores. Bacterial spores have extremely tough outer coatings that allow them to sur- vive in hostile environments in an inactive state, similar 15 to hibernation. When spores settle in favorable condi- tions, they become vegetative bacteria, which can grow and reproduce. Most bacterial diseases can be effectively treated with antibiotics (i.e., drugs that kill bacteria) if treat- ment is begun before the onset of symptoms, generally 1 to 4 days after exposure. For anthrax, more treatments may include vaccination and antitoxins, the latter of which counteract the toxin that this bacteria produces while growing in the body. â¢ Viruses are much smaller than bacteria. Viruses must be inside a host cell to replicate, thus they cannot replicate before infecting an organism. Two frequently used pro- duction methods for viral replication are cell culture and inoculation of fertilized chicken eggs. Medical treatment of viruses is more difficult than for bacteria. Diseases from some viral agents (i.e., smallpox and certain influenza strains) can be prevented with vac- cines. Vaccines are products that produce immunity to specific diseases, preventing the disease from occurring. When vaccines are available, they must be administered before the onset of disease symptoms to be effective. An- tiviral agents can destroy or weaken some viruses and also may be helpful for some viral diseases (e.g., small- pox and possibly some hemorrhagic fevers). However, in many cases, the treatment for viral diseases is limited to supportive care. â¢ Biological toxins are non-living chemicals produced by living organisms, in contrast with the human- manufactured toxins discussed in the chemical threats section. Examples are ricin, from the castor bean plant, botulina from the bacteria Clostridium botu- linum, and mycotoxins from fungi (i.e., molds). Many biological toxins are relatively stable. Diseases from some biological toxins can be treated with antitoxins (i.e., botulism), but these are not available for others (i.e., mycotoxins and ricin). In these cases, treatment is limited to supportive care. Biological organisms are given a two-part name, where the first name represents the genus and the second name is unique to the species. There can be different versions or strains of the same species. Often, the ability of an organism to infect peo- ple easily requires only a different strain. Different strains of the same type of organism also may have different resistance to antibiotics. A wide variety of biological threat lists circulate throughout the government and medical communities. These lists contain the same disease-causing organisms and toxins of typical concern, with variation in the inclusion of agents thought to be less likely to be used in an attack. Table 2-7 lists some commonly considered bioterrorism agents, the diseases they cause, and their Center for Disease Control (CDC) categories, which are described below in âCategories.â
The potential for exposure is defined as the probability of an individual to be exposed to the agent. Susceptibility refers to the likelihood of an agent to cause disease in a population exposed to the agent. Persistence of a biological agent relates to how long it re- mains a danger and how difficult it is to render harmless. As with chemical agents, the persistence of an agent in the en- vironment depends on factors such as temperature, humidity, and sunlight. The persistence of a biological agent may be quite different in the air, versus on surfaces or in soil or water. In this report chemical agents that substantially de- grade in open air within 24 hours of release were defined as non-persistent. However for biological agents, the definition of non-persistent is extended to 48 hours because, for the bi- ological agents addressed, persistence in open environments is either 48 hours or less, or a week or more, making a greater distinction between persistence categories delineated by 48 hours. For non-persistent biological agents in particular, sur- vival is often substantially longer in soils than in open air. Vegetative bacteria and viruses typically are not very persis- tent in an open environment, thus they only present a long- term risk when they are contagious. In contrast, spores are typically very persistent, lasting months to years in an open environment. Contagiousness refers to the ability of the biological agent to be spread from one person to another after it has increased in numbers in the initially infected person. Highly contagious agents can be spread with face-to-face contact, as coughed or exhaled droplets from infected individuals in a contagious stage of the disease are inhaled by others. Some highly contagious agents may also be transferred to others from touching the skin, clothes, or bedding of an infected individual or corpse. During the most contagious stages of these diseases, infected individ- uals tend to be obviously sick and often bed-ridden. Less contagious agents may be spread with bodily fluids. 16 Events Responses to biological events are driven primarily by the type, quantity, and dispersion of the biological agent. Recog- nition of the types of possible biological events can help in assessing vulnerabilities and risk. Three general types of biological events are as follows: â¢ Natural spread of a disease caused by a biological agent not deliberately concentrated as a weapon or for re- search purposes. SARS, West Nile Virus, Hong Kong Flu, and Avian Bird Flu are recent examples of biolog- ical threats that have not been deliberately concentrated. Influenza viruses, which cause the flu, are the biologi- cal group generally thought to pose the greatest risk of natural spread caused by their ability to continually mu- tate into new strains, thereby making established vac- cines ineffective. One of the most extreme influenza outbreaks recorded was in 1918.2 Estimates of deaths worldwide from the 1918 flu outbreak range from 20 million to 100 million. There is an increased potential for the promotion of natural spread of disease during events with other threat agents (i.e., conventional, chemical, or radiological) when responses include crowding of injured or displaced people, which may en- able the evolution of new, more contagious strains.3 Agent Type Organism Name CDC Category Disease Caused Host Organism Bacillus anthracis A Anthrax Human/Livestock Coxiella burnetii B Q-fever Human/Insects Bacterial spore Brucellae spp. B Brucellosis Human/Animals Yersinia pestis A Plague, bubonic and pneumatic Human/Insects Burkholderia mallei B Glanders Human/Livestock Vegetative bacteria Francisella tularensis A Tularemia Human/Insect/Animals Variola major Filoviruses A Smallpox Human and Arenaviruses (Ebola, Marburg, Lassa) A Hemorrhagic Fevers Human/Insects/Animals Virus Foot and Mouth Virus NA Foot and Mouth Disease Livestock Clostridium botulinum A Botulism NA* Castor bean B Ricin NA* Toxin produced by organisms Various Funji A Mycotoxin toxicity NA* NA = not applicable. Biological toxins are produced by organisms, but are chemicals rather than living organisms, hence they do not have a host. All listed toxins are toxic to humans TABLE 2-7 Potential Biological Terrorism Agents 2 In the U.S., deaths from the 1918 influenza outbreak were at least 500,000, repre- senting 5 percent of the population at that time. 3 The crowded conditions of wounded soldiers in WWI are thought to have facilitated the development of the influenza virus that caused the exceptionally deadly 1918 out- break. It has been suggested that in the previous year, a strain that was not initially very contagious, was more easily spread under extreme crowding of wounded soldiers, in particular, providing more opportunity for strain evolution. Similarly, Southeast Asian markets with dense crowding of a wide variety of animals (i.e., poultry and livestock,) and people are thought have facilitated viral strain developments that have lead to the more recent threats from Avian Flu and SARS.
Lack of knowledge prevents new strains from being used as a weapon in bioterrorism. â¢ Release during transport of biological material is the ac- cidental or intentional release of harmful biological ma- terial being shipped within the transportation system. Such material is considered DOT Class 6 material, âToxic and Infectious Materials.â These materials have strict shipping requirements to minimize leakage and re- lease. Such a release could occur following accidental or deliberate demolition of a carrier through the use of an explosive device. â¢ Deliberate release of a biological weapon is a release of a biological agent with the intent to harm a target. A small amount of a biological weapon may be sufficient to have significant effects in enclosed places such as buildings, tunnels, or subways, or within passenger compartments of airplane, trains, cruise liners, buses, and so forth. Larger amounts are needed for an effective outdoor release. Areas with high visibility, large crowds, and high economic effect are thought to be the most likely targets for bioterrorism. The most dangerous form of biological weapons agent is an aerosol, which is not the natural state of these organisms. Much sophistication is required to generate âweaponizedâ forms of these agents as found in the anthrax mailings in 2001. Materials legally transported within the transportation system are not weaponized agents and thus are less likely to remain suspended in air. However, these materials can still contaminate surfaces, causing access restrictions until ap- propriately decontamination. Dose and Infectivity The infectivity of a biological agent is the actual number of inhaled organisms necessary to generate an infection. These numbers are generally presented as the infectious dose (i.e., number of organisms) required for 50 percent of those individuals exposed to become infected (abbreviated ID50). In contrast, contagiousness refers to how easily an infectious agent can be spread from person to person. Infectivity, or ID50, can be more clearly measured than contagiousness. Therefore, many experts refer to infectivity rather than con- tagiousness. Agents that cause highly contagious diseases often have low infectivity; however, not all agents with low infectivity are highly contagious. The infectivity and conta- giousness of different biological agents are commonly used to define categories of these agents. Categories The Centers for Disease Control (CDC) assembled a panel of experts in 1999 to rank potential biological terror 17 agents based on their public health effect, dissemination po- tential, public perception of the risk, and the need for spe- cial preparation to respond adequately to a deliberate attack. The ranking did not include clean-up costs or plant and animal pathogens that do not infect people. The resulting ranks were used to establish three risk categories: A, B and C. Category A agents can cause high mortality rates, can be relatively easily spread either by contagiousness or delivery as a weaponized aerosol, and may have major public health effects. Category B agents are moderately easy to dissemi- nate and result in a moderate rate of disease and low mor- tality rates. This category includes the major threats to food and water supplies. Category C agents are those that do not currently pose a significant bioterrorism threat but could emerge as future threats. The CDC categories are often referred to in various ref- erences. However, for this report, the primary characteris- tics of a biological agent that affect the emergency response are the agentâs persistence in the environment, which helps determine the need for decontamination, and the agentâs contagiousness, which determines the possible need for quarantines. Quarantines are only considered for highly con- tagious agents. Based on contagiousness and persistence, the following categories of biological agents are referred to in this report and summarized in Table 2-8: 1. High persistence, low contagiousnessâThese biolog- ical agents take weeks to years to degrade naturally in the environment, but they are not typically transmitted from person to person. The causative agent of anthrax, the spores of Bacillus anthracis (BA), is the only CDC Category A organism that falls within this group. De- pending on the strain, BA may cause death in 85 per- cent of infected individuals if untreated. For BA, the dose required for infectivity has been estimated to be between 8,000 to 10,000 spores. Lower numbers may be required for cutaneous (open wound, skin infec- tions) or gastrointestinal forms of the disease. After washing to remove spores from skin and removal of contaminated clothing, it is difficult to transfer an in- fective dose of BA. The causative agent of Q-fever, Coxiella burnetii, is also a bacterial spore, and a CDC Category B agent that typically does not cause death. For Coxiella burnetii, the dose required for infectivity may be as low as one spore. Bacterial spores of both agents may last months to years in the environment. The causative agents of brucellosis, several bacterial species of the genus Brucella, are CDC Category B agents that typically do not cause death. Brucella is not able to form spores, but is relatively stable in the environment and can survive up to 6 weeks in dust. Brucella is relatively easy to decontaminate, while bac- terial spores can be very difficult to decontaminate be- cause of their protective spore coat. Of the toxins in this group, mycotoxins (produced by molds, e.g., T2 or
yellow rain) are very difficult to decontaminate, while ricin (extracted from castor beans) is relatively easy to decontaminate. 2. Low persistence, low contagiousnessâBacteria and toxin in this group cannot survive in the open environ- ment for more than a couple of days. Many of the bacteria in this group last only a few hours in open air, while botulinum toxin may take a couple of days to sub- stantially degrade depending on specific conditions (i.e., it may be stable for weeks in non-moving water or food). Both bacteria and toxins in this group are relatively easy to decontaminate. The bacteria in this group are rela- tively infectious, generally needing only 10 to 100 or- ganisms to cause an infection, and include both CDC Category A agents (i.e., causative agents of the bubonic plague and tularemia) and Category B agents (i.e., causative agents of glanders4). Botulinum toxin is pro- duced by the bacterium Clostridium botulinum under special conditions such as in poorly prepared canned goods and fish products. One of the most poisonous sub- stances known to man, it is a CDC Category A agent. As with other diseases caused by toxins, botulism is not con- tagious. The contagiousness of bacterial diseases in this group is relatively low. The bubonic plague is caused by Yersinia pestis. Although this disease is generally not 18 very contagious, the same causative bacteria can also cause the pneumonic plague, which is very contagious and listed in the group below.5 If untreated, diseases in this group may cause death in 33 percent (i.e., tularemia) to 100 percent (i.e., glanders) of the affected population. As few as a dozen organisms may be sufficient to cause an infection in a person, but these infections can be ef- fectively treated with antibiotics. 3. Low persistence, high contagiousnessâThe combina- tion of high contagiousness and high lethality makes the agents in this category formally listed as or equivalent to CDC Category A.6 The causative agent of smallpox, Or- thopox virus Variola major, is usually transferred from person to person in airborne droplets from the infected personâs coughing or breathing. It may also be trans- ferred through skin sores, secretions, and contaminated clothing and bedding. Some of the hemorrhagic fever viruses (e.g., Ebola, Lassa, and Marburg), Yersinia pestis in pneumonic plague cases, and influenza viruses may also be readily transferred from person to person. Weaponized versions of smallpox, hemorrhagic fever viruses, or Yersinia pestis would likely be formulated for PERSISTENCE (and CDC categories in parentheses) CONTAGIOUSNESS LOW = Less than 2 days in an open environment HIGH = Weeks to years in an open environment Bacterial Diseases: Tularemia (A) Plague, bubonic (A) Glanders (B) Bacterial Diseases: Anthrax (A) Q-fever (B) Brucellosis (B) LOW = Unlikely person to person transmission Toxin Diseases: Botulism (A) Toxin Diseases: Mycotoxins (A) Ricin (B) Bacterial Diseases: Plague, pneumonic (A) HIGH = *** Likely person to person transmission Viral Diseases: ** Smallpox (A) Hemorrhagic fevers (A) Influenza (no CDC category) Foot-and-mouth* (no CDC category) None known * Foot-and-mouth is highly contagious among livestock, it does not cause disease in people. ** Persistence may be longer on surfaces, clothing, and bedding. *** Note: highly contagious agents can remain persistent within the population regardless of persistence in open environments TABLE 2-8 Biological Threat Groups 5 Yersinia pestis can be transmitted through flea bites to infect human lymph nodes, causing the bubonic plague, which is not easily transmitted to another person because the bacteria reside in the lymph nodes rather than in the lungs. In contrast, if the same organism infects the lungs, it causes the pneumonic plague, which can be readily trans- ferred through person-to-person contact with exhaled droplets making it highly conta- gious. A bioweapon would likely disperse Yersinia pestis as an aerosol, allowing in- halation and causing pneumonic plague. 6 The CDC Categories A, B, and C were developed for bioterror agents that infect people. The influenza viruses pose a natural spread risk rather than a bioterror risk, and as such, have not been formally assigned to a CDC bioterror category. However, based on statistics from the 1918 influenza outbreak, lethality may approach that of smallpox (i.e., 30 percent) when a vaccine is not available, suggesting equivalence to CDC Category A for some influenza strains. 4 The summary references on glanders used in this report provide conflicting infor- mation on stability in an open environment. Glanders-causing agent Burkholderia mallei is reported to be sensitive to UV light by Acquista (The Survival Guide: What to do in a Biological, Chemical, or Nuclear Emergency. 2003, Random House Trade Paperbacks, NY, p. 28), likely causing its rapid degradation outside. However, it is listed as âvery stableâ in The National Academies Fact Sheet on Biological Attack, available at: http://www.nae.edu/NAE/pubundcom.nsf/weblinks/CGOZ-6C2MCR/ $file/Biological%20Attack.pdf.
inhalation. All agents in this group are relatively easy to decontaminate in the open environment. For livestock, the foot-and-mouth disease is caused by a highly conta- gious virus. Although this disease is not known to be transferred to people, it could cause substantial eco- nomic disruption. At this time, no commonly recognized biological threat agents are both very persistent in an open environment and very contagious. Also, for the purpose of this study we have included Foot and Mouth Virus (FMV) as an agroterrorism threat that is highly contagious but not persistent. Recent events in Taiwan and the United Kingdom have demon- strated the severe negative economic effect of an FMV out- break among livestock. This virus is highly contagious among livestock and sufficiently stable in the environment to travel many miles through the air to infect other hosts. Detection and Identification The terms âdetectionâ and âidentificationâ are frequently interchanged in the context of biological warfare compounds, even though they have very different meanings. Detection of biological agents refers to the ability to discriminate between biological and non-biological material without further char- acterization. Not all biological materials are hazardous and these technologies do not discriminate between âgoodâ and âbadâ biological organisms. Identification is the ability to dis- criminate between biological materials and accurately name them. The difference between detection and identification is the degree of resolution. Biological detection technologies detect the presence of airborne biological particles in a sampled volume of air. Changes in the number and types of particles in the air may indicate the presence of a biological hazard. Generally these detection technologies can discriminate bacteria and spores from pollen and fungi also present in the atmosphere. These detectors either use measurement of induced fluorescence, generally from protein components characteristic of a biolog- ical organism, or the identification of adenosine triphosphate (ATP) that is indicative of a living biological organism. The fluorescent detection technology is more sensitive than ATP detection, but it cannot discriminate between live and dead or- ganisms. Detectors that discriminate live and dead particles are relatively expensive and do not discriminate between âgoodâ and âbadâ organisms, so are subject to false or nui- sance alarms. These systems serve as âtriggersâ to activate an identification system. Detection systems can provide a first level of response in a transportation surveillance system. Biological identification technologies are used to name the type of biological material detected. The most common approaches to biological identification are antibody-based assays and nucleic acid (i.e., DNA) amplification and identi- fication assays. Each of these technologies has benefits and 19 limitations, but used together can result in sensitive detection with a high degree of confidence. Some antibody identification methods, such as hand held assays, are relatively simple, single-use devices that require little in the way of maintenance other than proper storage conditions. The sensitivity of antibody-based identification technologies depends on the availability of sensitive and specific antibody reagents. The most well-known type of antibody-based identification in the biodefense market is hand held immuno-chromatographic assays (HHAs), also referred to as antibody âtickets.â In general, HHAs are designed for one agent identification per assay. Although the systems are relatively robust, they are not as sensitive as DNA amplification-based identification systems. These sys- tems are commercially available and provide a responder with rapid, onsite analysis of some biological agents. DNA identification methods use an organismâs genetic code for positive identification. These methods require substantial operator training and maintenance requirements. DNA-based anthrax identification systems are in the early stages of opera- tion at select U.S. postal facilities. DNA identification for a wider variety of materials requires more procedural develop- ment. Specific biological toxins are identified with mass spectrometry, which requires substantial operator training and maintenance. Use of these technologies for laboratory or con- firmatory analysis of samples from the transportation system would likely either be contracted from a commercial firm or be conducted by another government agency. None of the identification technologies can determine if a biological agent is alive or dead, and a dead bacterium or virus cannot cause infection. A live agent is confirmed by its ability to grow in a culture media; such growth may take several days. The ability to discriminate between live and dead agents is critical for verifying decontamination technologies. Decontamination Decontamination is the inactivating or killing of bacteria, viruses, or toxins. Spores represent the most significant inac- tivation challenge. Vegetative bacteria and viruses are rela- tively susceptible to many means of remediation. Toxins have varying degrees of resistance, but can be inactivated by many of the materials used for decontamination. Surface deconta- mination of most biological agents can be achieved using dis- infecting solvents, foams, gels, or emulsions. A 0.5 percent hypochlorite solution (i.e., 1 part household bleach, 9 parts water) is a common recommendation. Line-drying clothes in the sun allows ultraviolet rays to kill most organisms. The use of disinfectant foams can increase the time a surface is ex- posed to effective concentrations of a disinfectant, which in- creases the likelihood of destroying the biological agentâa particular concern for more persistent agents (e.g., anthrax spores and mycotoxins). Mycotoxins are the most difficult of
the biological agents to destroy; however, as toxins rather than viable organisms, they may be washed away and diluted to safe levels with soap and water. Gaseous decontamination, or fumigation, applies to en- closed spaces. The primary choices for destroying bacteria and viruses are chlorine dioxide, methyl bromide, para formaldehyde, ozone, vapor hydrogen peroxide, and ethylene oxide. Any gas or vapor that can kill bacteria is also harmful to humans. Chlorine dioxide was used in 2001 to remediate anthrax in the Hart Senate Office Building and the Brentwood U.S. Postal Distribution Center. The remaining disinfectant gas was later broken down by the addition of sodium bisul- fate. Vapor hydrogen peroxide was successfully used by the Department of State to decontaminate a mail sorting facility in Sterling, Virginia, in 2002. Particularly in the cases of an- thrax spores, administering vaccines may sometimes be more practical than complete decontamination. After decontamination, removal or cleanup of the disin- fectant is required. Wide area decontamination would require close coordination with the U.S. EPA. The use of large quantities of liquid chlorine (i.e., bleach), in particular, will be subject to EPA and similar state requirements. These re- quirements may include containing runoff, measuring water quality, and possibly sustained holding of runoff water with other treatment until acceptable levels of both the initial con- taminant and any added decontaminants are reached. The EPA has released an alert relative to environmental liabilities caused by mass decontamination runoff. 2.2.2 Emergency Response Needs Regardless of the cause of a biological release, from an emergency response perspective, the primary considerations for response management are biological agent type and for- mulation, quantity and persistence, exposure route, disper- sion, and population density in the area at risk. These factors and their interrelationship are further discussed below. Table 2-9 delineates some of the information needed in a biologi- cal event to decide the appropriateness of transportation goals for evacuation, isolation and checkpoint establishment, and provision of supplies to the contaminated area. Agent Type and Formulation The type of agent, its associated infectivity and conta- giousness, and its formulation are key factors in assessing the threat posed to human health. The health risk to an ex- posed population is also affected by the quantity of the agent released and the likely exposure route (i.e., whether the par- ticle size will permit inhalation into the lungs). Similarly, in- formation on the biological agent type and formulation also determines what is needed to protect emergency response and cleanup personnel adequately. Formulation relates to 20 the physical state of the organism, and in particular, the like- lihood of the organism being suspended in air. Weaponized biological agents have been treated such that their physical properties favor aerosol dispersion. This quality makes their re-suspension into the air a greater threat than is posed by the naturally occurring forms of the organisms. Quantity and Persistence The quantity of a biological agent released and its disper- sal and likely exposure routes determine the area over which people may be infected. The persistence determines the du- ration of the risk of infection. The quantity of a viral or bac- terial agent is increased orders of magnitude in an infected individual, while the quantity of a biological toxin is not in- creased after release. Biological agents that do not survive long in open environments may still be very persistent over- all if they are contagious and can be easily transmitted from person to person. An upper range estimate of the quantity of the release of a biological agent in transport cannot be easily determined based on the container size. Often infectious material consti- tutes only a small proportion of contaminated medical wastes. Pure bacterial or viral cultures are shipped in small quantities because the receiving institution generally can culture more of the organism as needed, thereby reducing transportation concerns. In the event of a biological weapons attack, estimating the release quantity and associated area with concentrations of concern is difficult and made more difficult when there is a delay between exposure and recog- nition of an attack (i.e., observable symptoms). Exposure Routes Inhalation is the exposure route of greatest concern, and this is likely to be a primary form of exposure for agents dispersed Biological Event Information Needed to Determine Appropriate Emergency Response Estimated population exposed to levels of concern as determined from: Affected area information (see below) Population data Estimated affected area as determined from: Quantity and infectivity Location of release and contagiousness Wind direction and strength Topography Surface sampling Possible exposure pathways as determined from: Agent type Physical form and formulation TABLE 2-9 Determination of Biological Event Emergency Response
as aerosols with droplets in the 1- to 5-m-diameter range. This size range can be achieved by using either a solid or a liq- uid preparation. Because all the biological threat agents exist as solids, the liquid preparation is actually a slurry of particles in solution. Optimal dispersion occurs when the slurry is atomized such that only a few organisms are present in each liquid droplet. Because of the high surface-area-to-volume ratio of these small particles, the liquid evaporates leaving the aerosolized particles suspended in air. Dry agent can also be released after it is treated to result in a majority of particles within the appropriate size. Bacterial spores are ideally suited for this dry method because their nominal size is within this range and they are inherently stable. Vegetative bacteria, viruses, and toxins are better suited for liquid formulations, but can be prepared as dry agent as well. Particle size is critical for two factors. First, if the particles are too large, they quickly fall to the ground and are no longer an aerosol threat. Table 2-4 in the chemical subsection high- lights sedimentation rates for various-sized particles in stag- nant air. The second factor is that the size of a particle affects its ability to cause infection. In general, particles greater than 10 m in diameter are trapped by nasal hairs and released with exhaled air or sneezing. Particles less than 10 m in di- ameter are referred to as âinhalableâ because they may pass into the upper portions of the lungs, which contain many branched passageways. These passages (i.e., bronchi and terminal bronchioles) are lined with mucus and cilia. The mucus traps particles, and the cilia gradually push particles up and out of the lungs within about a day. These particles are then swallowed. Stomach acids can destroy many types of bi- ological agents, thus preventing infection. The smallest parti- cles (e.g., less than 2.5 m in diameter) are referred to as âfineâ or ârespirableâ particles. Fine particles may pass into the deepest portions of the lungs (i.e., respiratory bronchioles, alveolar ducts, and alveolar sacs) and may be removed by macrophages over many days, allowing time for bacteria growth and the development of an infection. Bacteria are typically 1 to 5 m in diameter, while viruses are generally 0.5 m or less. To put these sizes in perspective, the particle size of some common substances is shown in Table 2-5 of the chemical subsection. Biological agents either not released as an aerosol or released as large enough particles to settle on the ground pose greatly re- duced inhalation risks. Biological agents generally cannot cause infection by skin absorption unless there are open wounds. A notable exception to the inability of biological agents to pass through uninjured skin is mycotoxins, biological toxins pro- duced by molds. Mycotoxins act quickly, similarly to chemical blister agents. They can be distinguished from blister agents by a lack of odor and by a yellow, red, green, or other color associ- ated with oily droplets. As discussed in the chemical subsection, effective contam- ination of the drinking water supply of a city-sized population is not generally viewed as a credible threat by terrorism ex- ports. However, an attack on post-purification drinking water 21 storage in a small municipality or a specific building is viewed as more credible, but difficult to reach without site-specific knowledge and access. Alternatively, disruption of the water disinfection process may lead to unhealthy levels of biological disease agents. Intentional contamination of passenger drink- ing water within the transportation system is possible, but would probably not be a very large event in terms of injuries or casualties. Food contamination is also possible. Although only isolated cases of intentional food poisoning have occurred, several single accidental food poisoning events with chemical agents within the last decade have sickened thousands of people, sug- gesting the effects that could be achieved with intentional food poisoning. Dispersion and Population Density The density of the population in the area at risk affects the means for communicating instructions and the choices of transportation-related responses. The number of individuals at risk during a biological event depends on the population density and the area over which health-threatening levels of contamination are dispersed. Health-threatening levels are determined by the type of the agent and the exposure route. Dispersion of the initial release is determined from the phys- ical form of the released agent (i.e., aerosol or particles), topology and meteorology (i.e., rain and wind currents), and the quantity released. For contagious agents, dispersion will also follow the path of infected individuals. Aerosols and fine particles from a biological release may be dispersed by natural wind and wind generated from traffic. The particles dispersed by wind will eventually be de- posited onto surfaces. The atmospheric dispersion of small particles and aerosols is affected by many factors, such as en- ergy in the dispersion (i.e., fire, heat, explosion), height of re- lease, presence of obstructions (e.g., buildings, hills, and mountains), and weather conditions (wind speed and direc- tion, temperature, humidity, rain, and cloud cover). The most important factors are wind speed, wind direction, energy and height of release, and the presence of obstructing structures or natural features. Weaponized biological agents travel with the wind for many miles before being deposited on the ground. The actual number of infected individuals may be greater in areas of lower contamination because these areas are much larger than high contamination areas. Sampling, within enclosed structures and in strategically determined outdoor locations, is the most effective way to identify the extent of contami- nation. Both surface and air collections are made in areas of high contamination, but in areas of lower contamination, typically only air collections are made because significant amounts are often not found on distant surfaces. Secondary releases of an agent can be caused by two dis- tinct mechanisms. The first is by the introduction of wind or
an explosion in an area of relatively high contamination re- sulting in the re-suspension of the particles. The second, and more devastating, is the spread of contagious agent by in- fected individuals, as may be the case with smallpox, pneu- monic plague, and some hemorrhagic fever viruses. These diseases may be spread with exhaled air from infected indi- viduals; however, during the disease stages where this is pos- sible, infected persons are usually largely bedridden at home, in hospitals, or other medical centers. Livestock foot and mouth disease may also have secondary releases caused by contagiousness. Contagious diseases in particular may have a significant effect on transportation, which may be restricted or stopped to isolate either clean or infected regions. 2.2.3 Interrelationships between Biological Threats and Transportation Mode A biological release event that occurs near or in any trans- portation mode can contaminate the roadway or track on which vehicles travel, transportation vehicles, passengers, and cargo passing through the contaminated area. Factors that make a transportation mode more vulnerable to a bio- logical release include the presence of enclosed spaces, num- ber of passengers, re-suspension of biological particulates, and ease (or difficulty) of decontamination. These factors and other vulnerability factors are summarized in Table 2-10 for each transportation mode. 22 The highway (trucking) and rail transportation modes are frequent haulers of toxic and infectious medical materials, while the aviation and maritime modes are less frequent car- riers of DOT Class 6 infectious materials, and mass transit is never a carrier of these materials. The release of a biological agent during legal transport would disrupt travel along the specific route; however, the likelihood of widespread release of dangerous material is low. If an airplane crash resulted in release of an infectious agent, it is unlikely that the hazard from this release would provide significantly more threat to the personnel. Standard fire suppression techniques would minimize the chance of aerosolization. Because of the small amounts of dangerous biological agents that are transported and secondary packaging, the chance for release of signifi- cant levels of respirable particles is very low. Deliberate releases of gram to kilogram amounts of a bio- logical agent in enclosed spaces (e.g. buildings, passenger com- partments of rail, aircraft, and cruise ships) could contaminate many people and surfaces, both of which can serve as sec- ondary sources of contamination. All classes of biological agents would cause serious interruption of service if released in a passenger compartment of a commercial or public vehicle. In transportation system passenger compartments, the contamina- tion would be carried to subsequent destinations and could re- sult in widespread closure of the system. If the passengers did not detect the initial event it would be many days before au- thorities traced the source to a particular rail, air, marine, or mass transit route. The suspicion of release occurring within a Biological Vulnerabilities Highway Rail Transit Aviation Maritime Enclosed space â¢ Tunnels â¢ Passenger compartments â¢ Tunnels, â¢ Stations â¢ Passenger compartments â¢ Tunnels â¢ Stations/ terminals â¢ Passenger compartments â¢ Aircraft â¢ Terminals â¢ Cruise ships â¢ Terminals Potential for persistent contamination Low High for stations, passenger compartments High for stations and passenger compartments High for airports and passenger compartments High for cruise ships, terminals Ease of decon- tamination Moderate Moderate Easier Easier Moderate Resuspension of deposited contamination High High High Medium Low HVAC spread contamination None Within passenger car or station Within passenger compartments, terminals Within airports, aircraft Cruise ship, passenger terminals Drinking water contamination None Passenger drinking water Passenger drinking water Passenger drinking water Passenger drinking water Ability to contaminate other modes Yes Yes Yes Yes, at Airport Terminal Yes, at Dock only Agricultural cargo contamination Yes Yes No No Yes Transport pathway contamination Yes (road) Yes (track) Yes (transit route) Only Airport Docks, harbor, canals, rivers TABLE 2-10 Vulnerabilities to Biological Threats for Each Transportation Mode (Note: High more vulnerable (higher risk), Medium medium vulnerability, Low less vulnerable (lower risk))
passenger transport system (i.e., aviation, mass transit, and fer- ries) could have a devastating effect on customers riding the system. Substantial delays would occur attempting to locate the source. The most devastating medical effect would result from the release of contagious agents. By the time the infections were discovered, there would be many more foci of infection. The protected environment of enclosed spaces would help pre- serve biological agents, and decontamination efforts may be applied in these areas regardless of the agentâs persistence in order to assure safety and public confidence. More persistent agents would require more extensive and time-consuming de- contamination measures. The confined nature of ships and the sequestration of the personnel can, in some cases, minimize a biological agentâs effect as occurred with the Norwalk virus incidents. Then, the incubation period was short enough for individuals to become ill while still confined to the ship. This is in con- trast to a biological release in the transit, rail, and aviation modes, where the transit time is almost always less than the time required for observable symptoms, and passengers de- barking at subsequent stops can serve as secondary sources of contamination. Cargo transport of agricultural products and livestock are another potential target for bioterrorism. Release of a highly contagious virus such as the foot and mouth virus could spread the contamination widely with devastating economic effects. If a transportation mode is contaminated from either an enclosed release or an outdoor release, intersecting modes of transportation can cross- contaminate each other. A large outdoor release may result in closing transporta- tion paths in the vicinity and downwind of the release site until the limits of dispersion are established. In such an event, vehicle and building windows and HVAC systems should be closed so as to prevent exchanging air with the outside. The duration of risks associated with aerosols may be extended in areas with traffic-induced winds that can re-suspend particles into the atmosphere. All biological agents would have similar effect during the early phase after a release, however, the duration of the haz- ard varies with the agentâs persistence. Decontamination of viruses and vegetative bacteria may occur rapidly (i.e., hours to days) in the environment in the absence of secondary sta- bilization additives. Stabilizing agents can extend the life of these agents several-fold. The stability of different biologi- cal toxins varies from days to years in the environment. In contrast, bacterial spores (i.e., BA) are stable for years in the outside environment. In their natural form, these agents are quite stable and long-lived in the environment. The formula- tion as a weaponized agent requires total decontamination because of the ability of these preparations to re-suspend into the air and pose a health hazard. In all cases of biological agent release, timely detection and identification of the threat is important for developing the most appropriate and effective response. Unlike chemi- cal agents that react within seconds to hours, the delay 23 between exposures to biological agents to onset of symptoms is often several days. This is also confounded by the fact that many of these diseases initially present with flu-like symp- toms, which can add days to the correct diagnosis. Further- more, the later detection and identification occur, the greater the sampling and analysis needed to find out the extent of the contamination. Labile agents such as viruses and vegetative bacteria may escape detection because of their instability in the environment. 2.2.4 Consequence Minimization A primary factor in minimizing the consequences of a bi- ological release is the delay between the actual event and the discovery that a biological release has occurred. For all biological agents, the sooner a release has been determined, the fewer the number of casualties. Although this differen- tial varies widely between categories, it still is a factor. Once an event has been identified, it must be characterized so that protective and restoration actions can be initiated. Characterization includes identifying the agent and the es- tablishment of the contaminated area. Organisms with low persistence may no longer be detectable in the environment by the time a release has been determined, while stable spores in weaponized formulations will pose a continued health hazard as they are re-suspended by air currents. The size and variable environments in the transportation system present both strengths and vulnerabilities in terms of de- fense against biological attacks. If a biological agent is released in an enclosed space (i.e., building or passenger compartment), the HVAC systems may be closed or redirected to prevent continued re-circulation of particles. This action would be the same for chemical and ra- diological threats, thus an agent need not be identified to initi- ate this response. If a release occurs outside, building HVAC systems may be set to have slightly positive pressure inside, thus reducing the ability for outside contaminants to enter the building. Once again, this action would be the same for chem- ical and radiological threats, so an agent need not be identified to initiate this response. The incorporation of HEPA filtration within enclosed transportation facilities will greatly enhance the rapid removal of the threat from the environment. For rapid response in the event a threat agent is suspected in association with an explosion, emergency response plans may specify an immediate, conservative radius surrounding the ex- plosion site for isolation until the agent is identified and the most appropriate response can be determined. These bound- aries may be adjusted after a more complete biological survey with surface sampling and identification of the released agent. A difficult and probably controversial aspect of determining transportation response goals will be in establishing the physi- cal boundaries of isolation areas. Transportation officials are unlikely to have primary responsibility for these decisions and probably will be following instructions from incident
command and the emergency operations center (e.g., the state emergency management office or agency). A confounding variable is that there are no rapid identification methods for bi- ological agents, as there are for radiological and chemical agents. The ability to successfully route all potentially exposed traffic to decontamination areas clearly depends on the time it takes to recognize that the agent has been released. In the case of delayed detection of a release, effort may be needed to identify, decontaminate, and provide medical assistance to contaminated travelers, vehicles, and cargo after they have left the area of initial contamination. In some outdoor release cases, it may be safer for people to remain inside buildings (i.e., shelter-in-place) than to evacu- ate. If evacuation of an area is determined to be needed, evac- uees would be directed to decontamination areas. In these cases, transportation paths may be re-routed to expedite one- way travel. Essentially all modes of transportation may assist in population evacuations, as well as in transporting first re- sponders and providing emergency response supplies. Fur- thermore, any transportation modes with large buildings may be considered for use as temporary shelters. If the released agent or a disease outbreak is contagious, isolation of those infected is essential for containment. In this case, potentially infected people would be directed to area hospitals. Special routes may be designated for transport of potentially infected people. If hospitals cannot handle all those infected, quarters for quarantines may be necessary. In a worst-case scenario, people may be asked to stay isolated from others in their homes. In this extreme scenario, trans- portation would essentially be reserved for first responders and providing supplies. 2.3 RADIOLOGICAL THREATS Familiarity with the basic types of radiation that may pose threats can help in developing appropriate emergency response plans. The effects of radiation releases range from increased long-term cancer risks to acute radiation sickness and death. This section presents radiation fundamentals (2.3.1), emer- gency response information needs for decision-makers (2.3.2), and radiological threats and the transportation system (2.3.3). 2.3.1 Radiation Fundamentals A general understanding of radiation, including the terms used when referring to radiological threats, can improve com- munication when dealing with a radiological event. More in- formation on radiation is available from many commonly available sources, including the Internet. The radiation fun- damentals addressed are â¢ Basics, â¢ Events, 24 â¢ Categories, â¢ Doses, â¢ Detection, and â¢ Decontamination. Basics Radioactivity is a property of unstable atoms. As unstable atoms decay, they release or radiate energy in the form of particles or waves known as radiation. Radiation emanates in all directions from a radioactive material and can bounce off or reflect from surfaces or the air to get around a corner. The energy of the radiation determines whether or not it will pen- etrate a particular surface. Everyone is exposed to low levels of naturally occurring radiation. We are also exposed to radi- ation during certain medical procedures such as x-rays. Ultimately, radioactive atoms decay to a stable atom that is no longer radioactive. The time for half of a specific ra- dioactive material to decay to this stable and non-radioactive form is called its half-life. Half-lives can vary from fractions of a second to billions of years. After a period of ten half- lives, over 99.9 percent of a radioactive material has decayed to a non-radioactive stable substance. Therefore, radioactive materials with half-lives of up to hours decay too quickly to pose significant long-term hazards to humans. Radioactive atoms have the identical physical and chemical properties as their non-radioactive or stable counterparts. Thus, radio- active iron looks, feels, and behaves the same as normal sta- ble iron. Events Responses to radiological events are driven primarily by the quantity, quality, and dispersion of the radiological re- lease. However, recognition of the types of possible radio- logical events can help in assessing vulnerabilities and risk. Four general types of radiological events are described below: â¢ Radiological Infrastructure Event. Radioactive material may be released from any of the thousands of facilities in the United States that produce, handle, and store ra- dioactive materials (e.g., nuclear reactors, medical cen- ters, factories, food irradiators, research laboratories, construction sites, military depots, uranium mines, nu- clear fuel fabricating facilities, and nuclear waste stor- age sites), or from radioactive materials in transport between these facilities. Two particular types of release events that have received substantial attention and re- sponse planning in nuclear threat studies are â Nuclear Reactor Incident. This involves the release of dangerous levels of radiation from a nuclear reactor. In an extreme event, such as occurred in Chernobyl,
hundreds of square miles and the health of millions of people may be threatened. In such an event, state agencies would work in tandem with the federal agency that regulates the reactor or the federal agency that owns and operates the reactor to coordinate emer- gency response. The Nuclear Regulatory Commission regulates civilian nuclear reactors. The DOE and DOD regulate the reactors they own and operate for research and nuclear weapons production. The licens- ing of nuclear reactors requires establishment of evac- uation plans coordinated with the appropriate state and local response agencies. â Radioactive Material Transportation Incident. This refers to an accidental or deliberate release of radioac- tive material in transport. Large quantities of radioac- tive material are transported in special packages (i.e., casks or containers) which, if breached, can result in significant radioactive release. DOE-licensed haulers for radioactive materials follow pre-approved routes and must have an acceptable emergency response plan for radioactive leaks that includes training and commu- nication with the appropriate state and local response agencies along the shipping route. The effect of such an event could be a radiological dispersal that resembles an inefficient dirty bomb, contaminating the nearby area, including the transportation infrastructure and population. â¢ Passive Radiological Dispersion. Radiation can be spread passively, without the need of active dispersal mechanisms. For example radioactive material can be placed as pellets or liquid spilled in elevators, trains, or other spaces. Depending on the type of radioactive material and the time of exposure, the health effects experienced by exposed people can be severe, but the number of people and area affected would likely be rel- atively small. â¢ Radiological Dispersal Device (RDD). This refers to the use of a forceful (or active) method of spreading radia- tion into the environment. A dirty bomb (frequently mentioned in the media) is a prime example of an RDD. A dirty bomb uses a conventional explosive, such as dy- namite, to scatter a radioactive material, such as spent nuclear reactor fuel rods, or radioactive material from industrial or hospital equipment (e.g., Cesium-137 or Cobalt-60). The potential spread of radiation from an RDD is far less than from a nuclear bomb (referred to as a nuclear yield incident, below), which produces radia- tion from a nuclear reaction. Analyses of many RDD scenarios suggest that this type of event would probably have minimal prompt fatalities and little serious life- threatening radiation doses to the public. However, all analyzed scenarios have resulted in widespread, low- level contamination causing panic, terror, and signifi- cant economic impacts. More details and examples of RDD events are presented in Appendix A-4. 25 â¢ Nuclear Yield Incident. This refers to the detonation of a nuclear weapon (i.e., atomic, hydrogen, or neutron bomb). These detonations both produce and spread radiation and radioactive fallout (i.e., particles that descend through the air) as the result of either splitting atoms (fission) or fus- ing the nuclei of two atoms (fusion).7 The magnitude of such an event would result in substantial federal (civil and military) agency response that would likely exert sizable control on all emergency responses. Although state and local transportation officials would be involved in such a response, specific classified procedures have been devel- oped to guide responders. Thus, this extreme event is not specifically considered in this document. Categories Radiation refers to any form of energy that travels through space, such as light, heat, sound, and ionizing radiation. Ion- izing radiation is any type of radiation that can cause the par- ticles it strikes to become chemically charged (i.e., ionized). The radiation of concern in WMD is ionizing radiation, and throughout this report, all references to radiation are more specifically referring to ionizing radiation. Ionizing radiation is produced by atoms that are unstable because they have extra energy or mass. Unstable atoms, also referred to as radioactive materials, give off, or emit their extra energy or mass to become more stable. The energy or mass that is emitted from radioactive materials can be cate- gorized as alpha particles, beta particles, gamma rays and x- rays, and neutrons. These different types of radiation have different properties and therefore pose different hazards. Alpha particles are relatively heavy, cannot travel far, and cannot penetrate the skin, but these particles can cause dam- age if inhaled or ingested. Beta particles are lighter, can travel farther, and can penetrate the skin. Skin can receive a thermal burn (or beta burn) if it is exposed to a large enough quantity of beta particles. Gamma rays and x-rays are electromagnetic energy that can penetrate farther than beta particlesâfor ex- ample, up to 3 inches of lead. Gamma rays have a shorter wavelength than x-rays and thus have higher, more damaging energy. Gamma rays are only generated in nuclear processes, while x-rays can be generated by either nuclear processes or electronic devices. Neutrons are the highest energy form of radiation and penetrate the farthest. Neutrons are only re- leased during a nuclear detonation or as part of a nuclear re- actor leak. Many radioactive materials emit more than one type of radiation simultaneously. For example, the materials considered most likely to be used in a dirty bomb, Cesium- 137 and Cobalt-60, both emit beta particles and gamma rays. Radiation that penetrates body tissues is referred to as external direct exposure. For each type of radiation, the 7 In addition to nuclear (ionizing) radiation, these reactions also release thermal radi- ation, and they are unique in their release of an immediate electromagnetic pulse, or surge of electrical power.
protective shielding, expected range of unshielded radia- tion, and damaging exposure pathways for human health are presented in Table 2-11. A specific radioactive material, also called a radioisotope, is identified by its element abbreviation and atomic weight. The atomic weight is written either before or after the element abbreviation. For example, radioactive cobalt is identified as 60Co, Co-60, Cobalt-60, or Co60. Radioisotopes can exist as a single pure element or as a compound with other non-radioactive elements. For example, radioactive sodium combined with non-radioactive chlorine can produce radioactive table salt. Depending on the specific element or compound, radioisotopes can exist as a solid, liquid, or gas at normal temperatures. Each radioisotope has a unique half-life and energy of emis- sion of one or more types of radiation. Energy of emission is measured in electron volts (ev). A higher energy emission re- sults in greater penetration capability through shielding and the human body. In contrast, the quantity of a radioactive mater- ial is a measure of how many atoms decay in each second. This is called the activity and is expressed in units of Curies (Ci) or Bequerels (Bq) with 37 billion Bq = 1 Ci. Doses Radiation dose to humans is measured in units that quan- tify the damage that can be done because of the radiation type, energy, and quantity a person has been exposed to. These units are called rem or Sieverts ( 100 rem). Each of these units may be prefaced with milli- (m) or micro (), meaning one-thousandth and one-millionth, respectively. The average individual receives background levels of radia- tion at a rate of about 0.3 rem per year. Background radiation is naturally occurring radiation (alpha, beta, and gamma) from radioactive materials in the soil, air, and water. There is no natural neutron radiation. Lifestyle choices such as living at higher altitudes, frequent air travel, or residing in an area with high natural radioactivity in the soil and rocks can in- crease the natural radiation received by an individual. The average annual radiation dose in the United States is around 26 0.5 rem. This is slightly higher than background levels caused by exposure to man-made sources, including medical x-rays, CAT-scans, nuclear medicine, and so forth.8 Sub- stantial human health effects of radiation occur if the dose re- ceived exceeds 100 rem in a period of hours to weeks. A short-term dose to the whole body that exceeds 300 rem could be fatal to some people, depending on medical care. Greater detail on human health effects, established public dose limits, personal protection, and treatment after exposure is presented in Appendix C. Detection No type of radiation can be seen, felt, heard, smelled, or tasted. Radiation can only be detected with appropriate in- struments. Since September 11, 2001, the design and avail- ability of radiation measurement instruments, called dosime- ters, survey meters, detection meters, radiation meters, and Geiger counters, has grown. One instrument can measure alpha, beta, and gamma radiation, but the direct measure- ment of neutron radiation requires either another instrument or another probe to connect to an instrument. Almost all in- struments are portable and battery operated and can be as small as a personal pager or as large as a loaf of bread. For the purpose of first-responder detection of significant radia- tion, a detector or meter that measures alpha, beta, and gamma radiation dose rates from about 0.1 or 1 mrem/hour to 100 or 1000 rem/hour is adequate and can be purchased for about $400 to $1,500. Field personnel who may be first at the scene of an event may be able to provide critical threat in- formation if they have the appropriate detection equipment. Decontamination Almost all radiological events require some degree of decontamination. Removal or decontamination of surface Property or Hazard Alpha () Radiation Beta () Radiation Gamma () and X-ray Radiation Neutron Radiation Shielding Protection Normal human skin layer Less than 1/4 inch of metal, glass, or concrete 2 to 12 inches of lead, or 3 to 18 inches of iron/steel, or 1 to 6 feet of concrete 2 to 6 feet of water, or 4 to 8 feet of concrete Expected Range of Unshielded Radiation 1 to 4 inches in air 1 to 18 feet in air Hundreds to thousands of feet in air Hundreds to thousands of feet in air External Exposure Pathway to Humans Open wound absorption Open wound absorption, and external direct Open wound adsorption, and external direct Open wound adsorption, and external direct Internal Exposure Pathway to Humans Inhalation and ingestion Inhalation and ingestion Inhalation and ingestion Inhalation and ingestion TABLE 2-11 Radiation Shielding, Range, and Exposure Pathways 8 National Research Council, 2005. Health Risks From Exposure to Low Levels of Ion- izing Radiation: BEIR VII â Phase 2 Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation. National Academies Press, Washington, D.C.
contamination is typically achieved with vacuum cleaners or high-pressure water washing with suitable cleaners or deter- gents. Personnel working in decontamination areas would require proper protective gear, and waste from these areas would be disposed of as radioactive waste. Typically, the ease of decontamination is inversely related to surface ad- sorptivity. Thus, smooth surfaces, such as new cars and the outside of aircraft, are more easily decontaminated than rough surfaces, such as asphalt, concrete, terminals, stations, vehicle interiors, and so forth. In the more limited range of a pressure wave from a con- ventional explosion, radioactive particles may actually pen- etrate surfaces, rather than just lie on or adhere to the surface. In these cases, the top surface layers of road, tunnel, or walls nearby the blast area may need to be removed and disposed of as radioactive waste. There is no generally accepted guide on the most appropriate methods for dealing with long-term radioactive contamination of large surfaces that are difficult to decontaminate (i.e., asphalt and concrete). Handling of these cases is likely to be controversial and may vary de- pending on the location, expected surrounding population, and size of the contaminated area. In marine scenarios, pumped seawater could be effective in removing contamination from ships, docks, and other modes of transportation present in the harbor. If a radiologi- cal release is small enough and does not adhere to surfaces, it may be acceptably cleaned within a week; however, de- contamination of surface radioactivity generally can be ex- pected to take anywhere from weeks to years, depending on its magnitude and tenacity. 2.3.2 Emergency Response Information Needs Regardless of the cause of a radioactive release, from an emergency response perspective, the primary considerations for response management are: radiation type and energy, quantity and persistence, exposure route, and dispersion and population density in the area at risk. Table 2-12 delineates the information needed to decide transportation goals for isolation, shelter-in-place, evacuation, and checkpoint es- tablishment in a radiological event. These factors and their interrelationship are further discussed below. Type and Energy The type and energy of a radioactive material, and its quan- tity, determine the extent of shielding or distance needed to protect people from radiation. The type and energy of the ra- diation also determine what exposure routes are most likely to cause human health effects. For example, low-energy alpha radiation cannot penetrate the skin, but can be damaging if it is ingested or inhaled. In contrast, beta and gamma radiation can pass through the skin (i.e., external direct exposure), and be inhaled or ingested. 27 Quantity and Persistence The quantity of radioactive material released, in conjunc- tion with radiation type and specific radioisotopes, deter- mines the persistence as a health threat. Gaseous and liquid forms may be diluted to background levels. Releases of types of radioactivity with a short half-life may be isolated and contained until it has decayed to safe levels. Radioactivity with a very short half-life is not among the common threat scenarios. Of the more commonly discussed RDD compo- nents, Co-60 may have the shortest half-life (5.27 years). Thus, isolation of areas with Co-60 contamination for a decade would reduce radiation levels to about a quarter of the initial levels. In any case, the feasibility and cost of deconta- mination would be a significant consideration along with the value of the contaminated area. Exposure Route The expected exposure route needs to be assessed for ap- propriate risk management. As stated above, radiation type and energy determine the likely exposure routes, in con- junction with the physical form of the radioactive material as a gas, liquid, or solid. Inhalation is the primary exposure route of concern for a gas that contains radioactive materi- als (i.e., unstable atoms that release radiation). Depending on the type and energy of a radioactive gas, exposure through the skin may also be possible. A radioactive liquid would pose the greatest threat when introduced into a potable water system or other drinks, thereby allowing in- gestion. As with gaseous radiation, depending on the type and energy of radioactivity in a liquid, radiation may pass from the liquid through the skin. Radiological Event Information Needed to Determine Appropriate Emergency Response Estimated population exposed to levels of concern as determined from: Affected area information (see below) Population data Estimated affected area as determined from: Exposure pathway information (see below) Amount of material Location of release Wind direction and strength Topography Possible exposure pathways as determined from: Radiation type Physical form (gas, liquid, solid) Specific radioisotope TABLE 2-12 Determination of Radiological Event Emergency Response
Solid radioisotopes, in the form of sizeable shapes such as pellets, rods, discs, blocks, and plates, present a human health hazard if they are approached without proper shield- ing. Exposure may be by skin absorption for beta particles and gamma rays, the latter of which may also be inhaled. Al- though a large solid mass of radiation is the easiest form to contain, if the solid mass is broken into fine particles, it be- comes much more dangerous. Fine particles of radioactive materials are considered the most likely form in the event of an RDD because the explosion would physically spread particles regardless of whether the ra- dioactive material was initially fine particles or a large chunk pulverized by the explosion. Particles small enough to be in- haled present the greatest concern because they can affect human health though all exposure routes: inhalation, ingestion, and external direct exposure (i.e., radiation absorbed through the skin). The smaller the particle, the farther it may travel within the respiratory tract. In general, particles greater than 10 m in di- ameter are trapped by nasal hairs and released with exhaled air or sneezing. Particles less than 10 m in diameter are referred to as âinhalableâ because they may pass into the upper portions of the lungs, which contain many branched passageways. These passages (bronchi and terminal bronchioles) are lined with mucus and cilia. The mucus traps particles, and the cilia gradually push them up and out of the lungs in about a day. These particles are then swallowed and enter the digestive sys- tem. The smallest particles (e.g., less than 2.5 m in diameter) are referred to as âfineâ or ârespirableâ particles. Fine particles may pass into the deepest portions of the lungs (i.e., respira- tory bronchioles, alveolar ducts, and alveolar sacs), where they are removed by macrophages over many days and months, al- lowing longer-term lung exposure to the radioactive particle. The smallest particle size that can be distinguished by the unaided human eye is about 30 m in diameter. Table 2-5, in the preceding chemical agent subsection, shows the particle sizes of some commonly used substances to help put particle size in perspective. Dispersion and Population Density The density of the population in the area at risk affects the means for communicating instructions and the choices of transportation-related responses. The number of individuals at risk during a radiological event depends on the population density and the area over which health-threatening levels of radiation are dispersed. Health-threatening levels are deter- mined by the type and energy of the radiation. Dispersion is determined from the form (i.e., gas, liquid, solid, or particles), topology and meteorology (i.e., rain and wind currents), and the quantity of radioactive material. A radioactive liquid could spill on the ground, puddle, and be absorbed into soil or other solids as well as run into sew- ers or nearby natural bodies of water. Public exposure to a 28 liquid release could be relatively easily limited, and cleanup would be easier than for fine particles. Overall, topography, obstructions, and plumbing would largely decide the disper- sion of a released radioactive liquid. Water disinfection processes cannot reduce radiation levels. Dilution to safe levels is a possible solution for liquid radioactivity in some scenarios. Open-air gaseous radioisotope releases are generally quickly dispersed and diluted with the surrounding air, thereby presenting a relatively short-term, local radiological hazard. A release of a radioactive gas that is heavier than air may linger longer than expected when there is little wind. Structures such as buildings may also slow the mixing and dilution of released gases with air. Generally, a radioactive gas release in an enclosed space with little or no ventilation poses a much greater threat than a release outside. Predicted dispersion of a gaseous release in conjunction with an esti- mated radioisotope quantity can together indicate the extent of the area at risk, but many gaseous releases may be essen- tially completely dispersed by the time this information is considered. Similar to gases, fine radioactive particles may be dis- persed by natural wind and wind generated from traffic. In contrast to gases, particles dispersed by wind will eventually be deposited on surfaces where they may either stick or be re-suspended in the air. There has been extensive study of the atmospheric dispersion of radioactive gases and small radioactive particles (also called particulates). Although many factors affect dispersion of gases and fine particles, the most important factors are wind speed, wind direction, energy and height of release (i.e., fire, explosion), and the presence of obstructing structures or natural features (e.g., buildings, hills, and mountains). Table 2-4 in the preceding chemical subsection provides estimates on how long it takes various particle sizes to settle to the ground in the absence of air currents. 2.3.3 Radiological Threats and the Transportation System The transportation systems has particular vulnerabilities with respect to radiological threats, and as discussed below, is likely to be substantially involved in actions to minimize the consequences of a radiological event. Transportation System Vulnerabilities A radiation release event that occurs near or in any trans- portation mode can contaminate the roadway or track on which vehicles travel, transportation vehicles, passengers, and cargo passing through the contaminated area. Factors that make a transportation mode more vulnerable to sustained radiation during a radiological event include the presence of enclosed spaces, surface contamination and re-suspension of
radioactive particulates, and ease (or difficulty) of decontam- ination. These factors and other vulnerability factors are sum- marized in Table 2-13 for each transportation mode. Enclosed spaces such as tunnels and, to a lesser extent, road and track surrounded by tall buildings may more read- ily retain concentrated radioactive material than open spaces. Gaseous and particulate radiation may enter vehicles and vessels with air and, in all transportation vehicles, may be more readily retained in passenger and cargo compartments than in the open air. Factors that reduce the ability for quick dilution of radioactive gases or particles (i.e., enclosed spaces) allow people and cargo to receive larger doses, thereby increasing health effects. Among the largest public populations at risk in an enclosed space are those in transit underground stations or terminals, airport terminals, and large passenger compartments (e.g., trains, cruise ships, and aircraft). HVAC systems in enclosed spaces may increase exposure risks caused by continued cir- culation of radioactive gases or fine particles. Contamination of food and water cargo present unique concerns both as a specific target for contamination and as cargo present in the transportation modes passing through a contaminated area. Surfaces with a greater adsorptivity for particles will have greater levels of surface contamination from radioactive par- ticles. Thus, the surfaces are more vulnerable to greater and extended radiation exposure. In general, surface adsorptivity is less at high speeds and for aerodynamic, smooth surfaces including aluminum, steel, and glass (e.g., aircraft and high 29 speed passenger trains). Rough or corroded metal has high adsorptivity, as does bare concrete, asphalt, and fabric. Thus, surface contamination will generally be high for older vehi- cles, stations, terminals, roads, and clothing. The ease of decontamination is typically inversely related to surface adsorptivity. Thus, smooth surfaces, such as new cars and the outside of aircraft, are more easily decontaminated than rough surfaces, such as asphalt, concrete, terminals, sta- tions, and vehicle interiors. Time required for decontamination may range from hours to years, depending on the magnitude and tenacity of the radiation. Deposited solid radioactive particles can be re-suspended by air currents generated by passing traffic. This is a particu- lar concern for highway, rail, and mass transit because traffic on these modes would essentially expand the contaminated area. Spread of the contaminated area by traffic could also be an issue in ports, docks, canals, and rivers. The open sea, how- ever, is not susceptible to significant radioactive particle con- tamination from passing ships because its enormous volume would dilute any radioactive material to an insignificant concentration. Similarly, re-suspension of radioactive parti- cles by aircraft in flight is a reduced concern because the re-suspended particles would be greatly diluted in the upper air before settling to the ground. Intersecting modes of transportation can represent a substantial vulnerability because they can allow cross- contamination from one transportation mode to another (e.g., rail crossings, rail and bus stations, airports, ports Radiological Vulnerability Highway Rail Transit Aviation Maritime Enclosed space Tunnels Passenger compartments Tunnels Stations Passenger compartments Tunnels Stations/ terminals Passenger compartments Aircraft Terminals Terminals Passenger compartments Vehicle surface contamination High Low for high speed High for all others High Low for aircraft High for airports High Ease of decontamination Moderate Easier for high speed Moderate for others Easier Difficult for aircraft Easier for airports Moderate Resuspension of deposited solid particle contamination High High for low speed Low for high speed High Very Low for aircraft High for airports Very Low at sea High in port HVAC spread contamination None Within passenger car Passenger compartments High in airport or aircraft High in cruise ship Drinking water contamination None Passenger drinking water Passenger drinking water Passenger drinking water Passenger drinking water Ability to contaminate other modes Yes Yes Yes Yes, at airport Terminal Yes, at dock Agricultural cargo contamination Yes Yes No Slight Yes Transport path contamination Road Track Road, track, waterway Airport Harbors, canals, rivers TABLE 2-13 Vulnerabilities to Extended Radiation Exposure for Each Transportation Mode. (Note: High more vulnerable (higher risk), Low less vulnerable (lower risk))
and docks), increasing contaminant spread and area re- quiring decontamination. Transportation Consequence Minimization The first response in the event of a radiation release that contaminates transportation pathways would be to close the affected paths until they can be decontaminated and route contaminated people, vehicles, and associated cargo to iso- lation and decontamination areas. For rapid response in the event radiation is detected in association with an explosion, emergency response plans may specify an immediate, con- servative radius surrounding the explosion site for evacua- tion. These boundaries may be adjusted after conducting a more complete radiological survey. A difficult and proba- bly controversial aspect of determining transportation re- sponse goals will be in establishing the physical boundaries of isolation areas. Transportation officials are unlikely to have primary responsibility for these decisions and proba- bly will be following instruction from the emergency com- mand center (e.g., their state emergency management office or agency). Roads, in particular, are highly susceptible to radioactive contamination from vehicles that have traveled through an area contaminated with radioactive particles, thus the greater the potential travel time before traffic re-routing, the greater the area of contaminated roadway. Successfully routing all potentially exposed traffic to decontamination areas depends on the time it takes to recognize that radiation has been re- leased. In the case of delayed detection of a radiation release of particles that may adhere to passing vehicles and vessels, effort may be needed to identify and decontaminate poten- tially contaminated travelers, vehicles, and cargo after they have left the area of initial contamination. If radiation contamination issues are realized several hours to days after a radiological release, identifying cars and ves- sels that have passed through a contaminated area would be relatively easy within the rail and aviation system, for which essentially all trips are scheduled by a relatively few organi- zations. Port logs could identify large vessels that may have passed through a contaminated area. In contrast, the highway system has essentially no means for identifying vehicles that may have passed through a contaminated area, with the ex- ception of trucking industry logs. Mass media requests for highway travelers who may have been passed through cont- aminated areas to identify themselves may be the only way to identify highway system travelers. Responses to a radiological event may also involve pop- ulation evacuations, in which case transportation paths may be re-routed to expedite one-way travel. If the people, vehicles, and cargo from evacuated areas may be contami- nated, isolation and decontamination stops would be estab- lished along evacuation routes. Essentially all modes of transportation may assist in population evacuations, as well 30 as in transporting first responders and providing emergency response supplies. Any transportation modes with large buildings may be considered for use as temporary shelters. In some cases, it may be safer to have members of the pub- lic stay in a protected structure, called shelter-in-place, to avoid exposure to a passing cloud or plume of radioactive material. 2.4 COMPARISON OF CBR THREATS How much CBR agents affect the transportation system depends on factors such as the specific agent, the amount re- leased, the means of dispersal, and the surrounding infra- structure and population density. In terms of the potential area affected by a single event: â¢ Chemical releases could quickly affect tens of square miles. While decontamination of the most persistent of these agents may take many weeks, other agents may naturally degrade or disperse within hours. â¢ Biological releases could also affect tens of miles, and if a contagious agent is used, could soon lead to global effects. While decontamination of the most persistent of these agents may take many weeks, other agents may naturally degrade or disperse within hours. â¢ Radiological releases such as from a nuclear bomb or major nuclear power plant accident could affect hun- dreds of miles. However, more likely scenarios involve dirty bombs, which could affect up to about a square mile. Decontamination of persistent radioactivity would probably take months to years. The amount of a CBR agent needed to inflict a similar level of effect per area varies by many orders of magnitude. Table 2-14 compares the estimated minimum amount of a threat agent needed to cause heavy casualties within a square-mile under ideal conditions (i.e., efficient dispersal and optimal meteorological conditions). In addition to the amount of an agent needed to cause harm, other important factors in the use of a given CBR agent from the terrorist perspective are ease of acquisition Agent Category Description of Material Grams Fuel-air explosives 320 millionConventional Fragmentation cluster bombs 32 million Hydrocyanic acid 32 million Mustard gas 3.2 million Chemical GB nerve gas (sarin) 800,000 Radiological âCrudeâ nuclear weapon (in terms of fissionable material only) 5,000 Type A botulinum toxin 80Biological Anthrax spores 8 (Source: Kupperman and Trent, 1979) TABLE 2-14 Estimated Amount of CBR Agents for Heavy Casualties Within a Square-Mile under Ideal Conditions
31 Health Effects Agent Identification Potential Effect on Transportation Event Type Overt Event Covert Event How Recognized Field Sensors Time for Detection/ Identification Decontamination Requirements Overt Event Covert Event Radiological High Persistence Immediate for high doses, delayed for low doses. Treatment can reduce health effects. Same as overt event but more people affected and more serious effects. Must have sensor Readily available Seconds (on-site) Decontamination likely required. Long-term service suspension until safe levels achieved. Chemical Low Persistence Readily available Little to no decontamination except for very large releases. Short-term suspension of service until safe levels achieved. High Persistence Immediate to hours, temporary distress to mortality. Treatment can reduce health effects. Same as overt event but more people affected and more serious effects. Symptoms seen immediately to hours later Seconds (on-site) Decontamination likely required. Medium-term suspension until safe levels achieved. Biological High Persistence, Low Contagiousness Decontamination likely required. Medium-term suspension of service until safe levels achieved. Low Persistence, Low Contagiousness Symptoms typically delayed for days. Some agents: Effective treatment if initiated prior to symptoms. Other agents: Treatment limited to supportive care. Same as overt but reduced treatment effectiveness with delayed application. Symptoms seen days to weeks later if no analysis Available for some agents Some agents: Minutes (on-site) Other agents: Days for lab identification Decontamination may not be needed, depends on amount released. Short-term suspension of operations depending on the amount and stability of agent. Low Persistence, High Contagiousness Same as above with outbreaks around the country and world. Broad, medium- term service suspension until infected people are isolated and safe levels achieved. Very broad, medium-term suspension of service until infected individuals are isolated and safe levels achieved. Short-term broad suspension until know limited of spread, long- term suspension in contaminated areas. Short-term suspension of service until safe levels achieved. Short-term broad suspension until know limit of spread, medium suspension in contaminated areas. Short-term broad suspension until know limit of spread, medium suspension in contaminated areas. Short-term suspension if the released agent has not already lost infectivity. Possible very broad, medium term suspension of services until infected individuals are isolated and safe levels achieved. TABLE 2-15 Comparison of CBR Threats (Short-term a few hours to a few days; Medium-term several days to several weeks; Long-term several months to years)
32 Ability to Retain Contamination Difficulty of Decontamination Ability to Spread ContaminationVulnerability Chem 1 Bio 2 Rad 3 Chem 1 Bio 2 Rad 3 Chem Bio Rad Transportation Path Road Medium Medium High Medium Medium High Low Low Low Track Medium Medium High Medium Medium High Low Low Low Tarmac Medium Medium High Medium Medium High Low Low Low Air Low Low Low Low Low Low High 4 High 4 High 4 Waterway Low Low Low Low Low Low High 4 High 4 High 4 Indoor or Underground Stations/ Terminals Smooth surfaces High High High Medium Medium High Low Low Low Porous surfaces 5 High High High Medium High High Low Low Low HVAC system Medium Medium Medium Low Low Low High High High Outdoor Stations/ Terminals Smooth surfaces Medium Medium High Low Low Medium Low Low Low Porous surfaces 5 Medium Medium High Medium Medium High Low Low Low Vehicles/ Vessels Smooth surfaces Medium Medium Medium Low Low Medium Low Low Low Porous surfaces 5 High High High High High High High 6 Medium Medium HVAC system Medium Medium Medium Low Low Low High High High Contents Crew/ Passengers Medium Medium Medium Medium Medium Medium High 6 Medium 7 Medium Cargo/ food/ water High High High Medium Medium High High High High 1 Persistent chemicals include some chemical weapons agents (e.g., mustard agents, VX). Most transported industrial chemicals and many chemical agents are not persistent; thus ability to retain contamination and the difficulty of decontamination is low for many chemicals due to their non-persistence. 2 Persistent biological agents include Anthrax spores, mycotoxins (T2 or yellow rain), and the causative agent of Q- fever, none of which are very contagious. Most other biological agents are not persistent in an open environment, and the ability to retain contamination and the difficulty of decontamination would be relatively low. 3 Most radiological agents are persistent. For those that are not persistent the ability to retain contamination and the difficulty of decontamination would be relatively low. 4 Ability to spread contamination is high, but the contaminant may be relatively quickly diluted below levels of concern. 5 Porous surfaces include corroded metal, cement, rubber, carpet, fabric, etc. 6 Most persistent chemical agents of concern (i.e., mustard and VX) are oily liquids that may adhere to skin, clothing, and other porous surfaces better than solid particle forms of radiological and biological agents. 7 High if the biological agent is contagious (i.e., influenza, pneumonic plague, smallpox, some hemorrhagic fevers). TABLE 2-16 Relative Vulnerabilities of the Transportation System to Releases of Persistent Chemical, Biological, and Radiological Agents (Persistence more than 24 hours to substantially degrade in an open environment) or manufacture and probability of successful delivery to the target. Although radiological and biological agents can af- fect a broader geographic area than chemical agents, ob- taining the most potent forms of chemical agents is gener- ally easier than for biological and radiological agents. For all agents, effective dispersal is a substantial dif- ficulty. These difficulties are exemplified in the multiple attacks by the Aum Shinrikyo cult in Tokyo first using bio- logical agents without success and then chemical agents with modest success (i.e., diluted chemical and crude, rela- tively poor dispersion). The nature of risk is that while the most likely types of events over an extended time may be predicted, the next sin- gle event type cannot be predicted. The 2001 anthrax mail- ings in the United States exemplified this problem in that the agent used was a highly weaponized bacterial strain that is very difficult to obtain or produce. Therefore, this specialized form was not among the more likely agents to be used in a terrorist act, but it was used nevertheless. Thus, all credible event types must be given serious consideration and response planning, regardless of their relative likeliness to occur. The general characteristics of CBR releases are summa- rized in Table 2-15 in terms of health effects, agent identifi- cation, decontamination requirements, and potential effect on transportation. CBR subcategories are delineated based on the agentsâ persistence and contagiousness. Persistence refers to the extent of time a released agent remains a threat in an open environment; and contagiousness denotes the po- tential to multiply within an infected person and then spread from person to person (i.e., a characteristic unique to biolog- ical agents). Both of these factors have a profound influence on the duration of health risks, the scope of human health ef- fects, and the related duration and magnitude of effects on the transportation system. For most CBR agents, the magnitude of health effects and related effects on transportation vary greatly for overt and
covert releases (Table 2-15). An overt event is quickly rec- ognized because of accompanying signs such as an explo- sion, visible plume, odor, or warning letter. Overt events generally solicit better targeted and measured responses from all sectors, including transportation. In contrast, a covert event is not quickly recognized, which causes delays in agent identification, delivery of emergency response, and implementation of mitigating measures. The rapid onset of symptoms from most chemical agents in conjunction with rapid detection technology reduces the differences in effects between overt and covert chemical re- leases. In contrast, firm identification of biological agents often takes days after an event is suspected, and in a covert event, the development of suspicions of an event may also take days to weeks. During such delays, persistent biological agents and infected individuals continue to spread aided by the transportation system. Rapid detection of radiological agents allows for rela- tively rapid determination (i.e., within hours) of contami- nated areas (Table 2-15). However, in a covert radiological event with low enough doses of radiation for delayed symp- toms, the hazard may not be detected for years, or until a serendipitous measurement of radiation is made. In general, the speed with which CBR contamination can be identified affects the duration of broader, shorter-term effects of a CBR release on transportation, and the difficulty of de- contamination of the CBR agent largely determines how long areas of the transportation system may be isolated and restricted. 33 Table 2-16 summarizes the transportation systemâs rela- tive vulnerabilities with respect to the systemâs ability to re- tain contamination of persistent CBR agents at levels that may affect human health, the difficulty of decontamination, and the ability to spread these contaminants. In enclosed areas (e.g., passenger compartments and build- ings), the ventilation system may help disperse CBR agents, so shutting down these systems is a commonly recommended first- response. In open, outdoor areas, concerns about wind spread of contamination may be off set by factors such as the ability of wind to enhance evaporation of liquid agents and broadly dilute vapors and small particles to safe levels and degradation of many chemical and biological agents by sunlight. These same factors may facilitate decontamination of chemical and biolog- ical agents in open environments; however, runoff control of de- contamination chemicals may be more challenging. In general, porous surfaces have greater ability to retain contamination than smooth surfaces. Porous surfaces such as fabric, rubber, and corroded metal have microscopic pits and valleys that may retard natural degradation and hinder de- contamination efforts. After decontamination, the only CBR agents that may be spread further are the subset of biological agents that are con- tagious. For many diseases, the most contagious stages occur during the period that infected individuals are obviously sick and often confined to bed. The transportation system may fa- cilitate the dispersal of infected individuals before conta- gious stages and the possibility of contagious passengers in- fecting other passengers.