Decision-making in CWA response


CarolinaFireJournal - Chris Wrenn
Chris Wrenn
10/18/2009 -

(This is part one in a three-part series on gas detection.)
 
In responses to releases of Chemical Warfare Agent (CWA) there may not be one technology or one “answer” that is correct. The responder must take into account all of the clues present to conclude the presence or absence of CWAs and take appropriate action. Understanding what the clues are and how to layer them to make a decision is critical to successful CWA response.

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Why is gas detection important?
Responders cannot rely on their senses for decisionmaking. Without effectively knowing how to use detection techniques responders are unable to properly identify threats and make Personal Protective Equipment (PPE) decisions that are appropriate to the actual hazard. Detection technologies supplement our senses when making decisions in potentially hazardous environments. Relying on our senses alone can be dangerous in chemical response, detectors become our eyes and ears when our senses fail us. Proper use of detection technologies coupled with the clues present at the scene allow us to make better decisions.

Risked based response
Risked Based Response (RBR) is a common concept in the first responder community. The idea is to respond at the lowest level necessary to prevent undue risk to the responder while protecting the public. Over responding can be dangerous to the community because panic is as effective a killer as bullets, bombs or chemical attacks. One example of how panic can kill occurred in 2003 when more than 1,500 people were in the Epitome Night Club in Chicago when someone released pepper spray into the air. Twenty-one people were crushed to death in the resulting stampede to evacuate the club from the unknown chemical release. The community will echo how the first responders act. If the first responders are calm, civilians will act accordingly. If the first responders overreact and immediately jump into full encapsulation protection it could panic the public and cause unnecessary worry.

Over protection can be dangerous to the responder
Heat stress is the number one injury in HazMat response and immediately jumping into full Level A encapsulation is a good way of overheating oneself. Level A encapsulation also makes one much more susceptible to slip, trip and fall injuries. Finally, over protection makes it harder to get things done. Properly used, detection allows responders to respond at lower levels of PPE to provide the highest levels of safety to themselves and to the community that they protect.

CWA response Is a 3-step process
Location: one needs to quickly figure out where the problem is coming from using clues, common sense and survey tools. Victims running from a central location, clouds of chemical, and pools of liquid all provide location clues. Survey technologies like Photoionization and Flame Ionization Detectors (PIDs & FIDs) also can help. Location should take seconds to minutes and can cost nothing to $3000 to $5000 for a survey monitor like a PID.

Classification: one needs to quickly get a general idea of the kind of threat using clues, common sense or classification technologies like colorimetric techniques, Ion Mobility Spectroscopy (IMS), Surface Acoustical Wave (SAW) or Flame Spectrophotometry. In the case of CWAs, at this stage it isn’t necessary to differentiate between Soman (GA) or Sarin (GB) because the initial response protocol is the same. Classification should take seconds to minutes and can cost from $5 to $20,000.

Identification: using clues, common sense or an instrument, we can gain the specific identity of a chemical or a mixture of chemicals. This can back-up the initial classification and will be helpful in further prosecution of the perpetrators. Common technologies include Raman, Fourier Transform InfraRed (FTIR) and Gas Chromatography/Mass Spectroscopy (GC/MS). Response time can range from 60 seconds to more than 15 minutes.

What are CWAs?
CWAs or Chemical Warfare Agents are chemicals designed to either kill or debilitate an opposing military. They are often derived from civilian Toxic Industrial Chemicals (TICs) such as insecticides, chlorine and hydrogen cyanide.

Why worry about CWAs?
In 1994 the Japanese Cult Aum Shinrikyo released a Sarin spray from a refrigerated box truck in a quiet neighborhood of Matsumoto Japan with the intent to kill three judges who were due to rule against the cult. Seven people were killed and 200 hospitalized. Later in 1995 the Aum cult again used Sarin to terrorize the Tokyo subways by simultaneously spilling Sarin liquid in a number of subway cars. Twelve people were killed, about 1000 were hospitalized and thousands were made ill. In Iraq, insurgents have used chemical munitions to make roadside IEDs (Improvised Explosive Devices). With terrorist groups having demonstrated their ability to make and use CWAs, responders must look at ways to effectively detect and respond to these compounds. A brief history of CWAs Chemical warfare is not a 20th century development. The Chinese used arsenical smokes in 1000 BC. The Spartans used noxious smoke and flame against the Athenian allied cities in the Peloponnesian War in 429 and 424BC. Leonardo DaVinci proposed a powder of sulfur and verdigris (oxidized copper) as a weapon in the 17th century. John Doughty, a New York City school teacher, proposed chlorine filled 10” shells during the US Civil War but was turned down because the weapon was too inhumane. In 1915 the Germans used Chlorine against the English trenches in Ypres, Belgium. One of the lessons from using Chlorine is that it is not stable and persistent. Wind easily carried the chlorine gas over to the English trenches. However, the weather is fickle, and when the wind changed it carried the chlorine gas back over to the Germans. What was needed was a stable and persistent chemical that would stay where it was needed. Mustard “gas,” also called Yperite or Ypercite was used for the first time near Ypres in the autumn of 1917. Mustard is a liquid at normal temperatures and it is very persistent. That is, it is not a gas and it stays where it is put. Mustard is so pervasive that it still remains in the soil and water around Ypres. Modern farmers have sat down on freshly cut tree stumps and suffered severe burns to their rear ends because the trees draw up the mustard in the soil and water and concentrate it in their sap.

The invention of modern “nerve agents” On December 23, 1936 Dr. Gerhard Schrader of I.G. Farben invented Tabun (GA) as an insecticide. Because of a 1935 Nazi decree it was reported to the Ministry of War as an invention of possible military significance. In 1938 Sarin was invented and was named for its discoverers Schrader, Ambros, Rigriger and Vad Der Linde.

CWA classes and characteristics CWAs are grouped into three major categories: Nerve Nerve agents are liquids at normal temperatures that are stable and persistent. Nerve agents are acute (quick acting) and act by inhibiting the chemical actions of the central nervous system. Nerve agents are organophosphates that are similar to insecticides but 100 to 500 times more powerful. They shut down the nervous system by blocking acetylcholinerase transmission at the nerve synapses (acetylcholinerase inhibitors). At IDLH (Immediately Dangerous to Life and Health) levels they produce muscle twitches, foaming at the mouth, tremors, and lungs constrict and fill with fluids. At TWA (Time Weighted Average or eight hour dosage levels) they can produce pinpoint pupils, watery eyes, stomach cramps or can feel like a bad hangover. One thing to remember is that victims are the ultimate and best nerve agent detector.

Blister  Blister agents are liquids at normal temperatures that are stable and persistent. Blister agents can take minutes to hours to develop blisters. They often don’t kill their victims like nerve agents. But blister agents certainly make it difficult for soldiers to perform their tasks. When inhaled, blister agents can fill their victims’ lungs with fluid and they can develop pneumonia. Because blister agent symptoms take time to develop and it doesn’t immediately cause death, many people don’t consider blister agents an effective WMD agent. While they can deny usage of an area and they definitely cause pain and suffering, they don’t provide the dramatic effects that other WMDs can provide.

Blood or choke Blood or choke agents are gases at normal temperatures that are neither stable nor persistent. They include chlorine, phosgene, hydrogen cyanide and cyanogen chloride. They act by choking, or preventing the blood stream from taking up oxygen by preferentially binding to hemoglobin. Typically they are derived from TICs or still have legitimate industrial uses.

A brief review of chemical properties When discussing CWAs it is important to understand their chemical properties. Vapor Pressure tells us how readily a liquid (or solid) wants to evaporate into a vapor. Low vapor pressure chemicals don’t want to make vapors while high vapor pressure chemicals want to become gases. Any chemical with a vapor pressure over one ATM, 760 mm Hg, 14.7 PSIA or 1,701 mb is a gas. Vapor pressures of over 40 mm/Hg are more likely to move around and are considered to be an inhalation or vapor hazard. As a reference point, water has a vapor pressure of 20 mm/Hg. A chemical’s boiling point is another way to understand how readily a liquid wants to move to a vapor state. A liquid’s boiling point is the temperature at which it transitions to a gas. Low boiling point chemicals want to become vapors and have relatively higher vapor pressures making them easier to measure in air. An example is gasoline. High boiling point chemicals don’t want to become vapors, have relatively low vapor pressures and are harder to measure in air. An example is diesel. From chart C, we can see that CWAs all have vapor pressures well below 40mm/ Hg and therefore do not present much of a vapor threat. In comparison, while diesel will burn, it doesn’t represent much of a flammability threat unless it is sprayed in a mist. Due to their low vapor pressure and high boiling points, CWAs don’t represent much of a vapor threat unless they have been aerosolized in some way, otherwise they are heavier than air and tend to stay low to the ground. All of the CWAs have vapor pressures less than 40mm/Hg (the arbitrary “vapor threat” pressure), less than 20mm/Hg for water (which we all know isn’t that volatile), less than diesel and even less than number six fuel oil (essentially crank case oil) so CWAs are not going to easily move around on their own (unlike gaseous TICs like ammonia or chlorine which move easily).

Water solubility CWAs are complex organic compounds and are not very water soluble. This can provide a clue. For example, water will bead up on M8 paper and M9 tape while organic chemicals and CWAs soak right into these colorimetric technologies. If a sample beads up on M8 paper it probably is not a CWA.

There is no such thing as “nerve gas” CWAs are stable and persistent liquids, as opposed to gases, because the army that deploys them wants them to stay on their enemy and not float back. Without some means of becoming aerosolized, CWAs will take some time to produce vapors that would affect people at room temperature of ~20oC/65oF. Compared to gases like chlorine, hydrogen fluoride, and ammonia which all can move readily in air, CWAs are very toxic but they are not that tough to contain and deal with. Finally, unlike most other atmospheric threats (like lack of oxygen) there are antidotes for CWA exposure. (Next issue will discuss biological detection.)

Christopher Wrenn is the Sr. Director of Sales and Marketing for Environics USA a provider of sophisticated gas and vapor detection solutions for the military, 1st responder, safety and homeland security markets. He has been a featured speaker at more than 20 international conferences including the American Chemical Society’s annual conference, NATO’s advanced research workshop and Jane’s Defense Weekly WMD conference. He has written numerous articles, papers and book chapters on gas detection in HazMat and industrial safety applications.
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