Response to Overt Chemical, Biological, or Radiological Terrorist Attacks

According to a study conducted in the mid-1990’s by the Public Safety Group, there are over 950 chemicals, microorganisms, biological toxins, and radioactive substances with potential benefit for terrorists seeking to create casualties or generate public anxiety. Some of these agents have been produced for military applications and are commonly known by the public such as bacillus anthracis (the bacteria which causes Anthrax), sarin, and mustard. Other possible agents include toxic industrial chemicals (TIC’s) such as ammonia, chlorine, formaldehyde, and tungsten hexaflouride. And then there are hundreds of agents which were largely dismissed by militaries, but potentially useful to terrorists such as MPTP, fentanyl analogs, rabies virus, and others.

In addition to the spectrum of possible chemical, biological, and radiological (CBR) agents, there are a wide range of methods that can be employed by terrorists to intoxicate or infect people. Agents may be used to contaminate food or beverages, relying on ingestion as a route of entry into the victim’s body. Some agents can be disseminated as aerosols or vapor, relying on inhalation or exposure to the eyes and skin as a means of entering or affecting the body. Other agents may be used to contaminate projectiles or disseminated by infected or contaminated insects (i.e., vector weapons).

Considering the range of possible agents, dissemination methods, and possible venues for attack, the number of possible scenarios is endless. However, for the purpose of security planning and response preparation, attacks can be generally categorized as overt or covert.

Overt Chemical, Biological, & Radiological Attacks

In an overt attack scenario, observable indicators are present at the time of attack to suggest that an attack has occurred or may be pending. Such indicators could include:

  • Credible warnings or threat statements
  • Presence of unusual aerosols, visible vapors, droplets or powder
  • Small explosion(s) followed by an aerosol or plume of fine powder
  • Discovery of a possible dissemination device
  • People exhibiting symptoms of exposure to chemical agents with fast rates of action (e.g., hydrogen cyanide, nerve agents, etc.)

Although there are numerous possible scenarios for overt attacks, most overt attack scenarios involve dissemination of agents in the form of an aerosol or vapor. For the purpose of defining safe procedures for response to aerosol and vapor attacks, procedures are largely dictated by when/where the agent is disseminated—indoors or outdoors.

Indoor Aerosol or Vapor Attacks

If a suspected aerosol or vapor release occurs indoors, best procedure is to immediately alert anyone else nearby and evacuate the building. If you have an extra piece of clothing available, cover your nose and mouth while exiting the area to aid in filtering airborne contaminants. According to tests conducted in the 1970’s, even a cloth towel folded four times and held tightly over one’s nose and mouth can provide filtration with a potential protective factor of 8.

Once you have exited outdoors, look for arriving emergency responders. Once the hazardous materials team arrives on-site, they will establish a location for personal decontamination and victim assessment and treatment. Follow the directions of emergency responders and ensure that you are fully decontaminated and assessed—even if you are not exhibiting any symptoms of agent exposure.

If emergency responders are delayed, move at least 300 feet upwind of the building and avoid contact with people who were outside the building at the time of the attack. Even though you may feel fine, most chemical and biological agents have a delayed onset of symptoms and contaminants deposited on skin and clothing that can be transferred to others. While waiting, monitor yourself and others for symptoms of intoxication. Particularly watch for any symptoms of nerve agent intoxication.

Nerve Agent Symptoms

Nerve Agent on Skin

  • Localized sweating
  • Muscular twitching at location of drop
  • Nausea
  • Vomiting

If dose is sufficient…

  • Loss of consciousness
  • Convulsions
  • Flaccid paralysis
  • Respiratory failure
  • Cardiac arrest

Inhalation of Vapor or Aerosol

  • Dim vision / pinpointed pupils
  • Difficulty breathing
  • Runny nose

Eventually (if dose is sufficient)…

  • Loss of consciousness
  • Convulsions
  • Flaccid paralysis
  • Respiratory failure
  • Cardiac arrest

Nerve agents are highly toxic chemicals with very fast rates of action. If these types of symptoms are observed, immediately begin expedient decontamination and seek expedited medical treatment.

See the section below for guidelines on expedient decontamination.

Outdoor Aerosol or Vapor Attacks

If a suspected aerosol or vapor release occurs outdoors, alert anyone else in the area and move immediately to an indoor location. Ensure that the windows and doors are closed and that the heating/ventilation/air conditioning (HVAC) system is shut off. Although there are some unique circumstances where operating an HVAC system is helpful, such as a high-rise building with rooftop air intakes, it is generally best to minimize risk of contaminated air intake.

Locate a room toward the interior of the building and away from the building façade, entrance doors, stairwells, and elevator shafts. It is also preferred if the room has minimal openings such as doors and windows (and ideally, without drop ceilings). Shelter-in-place until after the plume has passed.

Next, if possible, use duct tape and plastic sheeting to seal all openings to the room including doorways, windows, electrical and telephone outlets, air vents, etc. If duct tape and plastic are not available, be creative and use what you have available. In an office, plastic garbage bags and transparent tape can be used in an emergency. At home, wet towels can be stuffed under doors and used to plug openings. As a general rule, the better the room is sealed, the lower the air exchange rate and thus less likely dangerous levels of aerosol or vapor will penetrate the room.

In a worst case scenario (when sheltering materials are not available), simply being in an enclosed room without the HVAC system operating will still provide a reasonable degree of protection. In the 1994 sarin attack against an apartment building in Matsumoto, Japan, the only people who experienced sarin intoxication were people who slept with their windows open. Simply remaining in an enclosed structure with closed windows and doors can greatly reduce the risk of exposure to an outdoor aerosol or vapor plume. This point is also reinforced by numerous case studies of hazardous material accidents in the United States.

Once the shelter room is sealed, monitor news reports for indications when an all-clear order is issued by authorities. If evacuation becomes necessary before the area outside is all clear, tape down all sleeves and pant legs and use any available clothing to cover as much exposed skin as possible. Use a towel or thick piece of cloth for expedient respiratory protection.

In most cases, the best response is to remain in the shelter room until authorities declare the area clear or instruct you to exit. While waiting for instructions, watch for any indications that the aerosol or vapor is penetrating the room. If there are indications that the agent is entering the room or if people begin to exhibit symptoms of intoxication, early evacuation may be necessary. If you need to evacuate, use expedient respiratory protection and move everyone quickly through the hazardous area and directly to the upwind location of the fire department’s decontamination site. The decontamination site can usually be recognized as an area where tents, barrels, hoses, and wash basins are located. There will also most likely be emergency vehicles parked nearby and people working in protective clothing.

Expedient Decontamination

In most urban locations, emergency responders will be on-scene and set up for decontaminating exposed people within a reasonable period of time. In most cases, waiting fifteen to thirty minutes for decontamination will not result in severe consequences. However, if emergency responders are delayed for a longer period of time or if people begin exhibiting symptoms of nerve agent exposure as described earlier in this article, it may be necessary to initiate decontamination before emergency responders arrive.

If expedient decontamination is necessary, use a systematic process to ensure that people are decontaminated properly and minimize the spread of contamination on the ground. Starting near the contaminated area, evacuees should strip to at least their undergarments. Discarded clothing should be collected at one location downwind of the decontamination site. Next, exposed people should wash thoroughly with water (ideally, hot, soapy water). In most cases, hot water will not be available. Expedient sources of wash water include water hoses, fire hydrants, fire sprinklers, swimming pools, and outdoor fountains. Swimming pools are particularly ideal, as they contain chlorinated water similar to the hypochlorite solution used by emergency responders for decontamination. If a swimming pool or fountain is used, people should wade and wash inside the pool, exit, and rinse using a separate hose outside of the pool.

When establishing a wash site, pay close attention to drainage. Be sure that contaminated wash water is not running into the “clean” side of the decontamination site. Use caution and ensure that washed evacuees do not become re-contaminated due to run-off from the wash area.

Everyone who passes through the wash site should be collected and monitored until emergency responders arrive. If necessary, decontaminated people can be temporarily clothed using large garbage bags to provide a degree of privacy. Once emergency responders have set up their decontamination site, everyone who was passed through the expedient wash process should be decontaminated again and properly assessed for exposure.

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