Chemical Nerve Agents

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Chemical Nerve Agents

• Esequiel Barrera, SM (TOX)
• Biol/Chem Safety Officer at UTSWMC, Dallas

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Toxic Responses of the Nervous System

• Normal Neural function neuron, nissl substance,
  myelinating cell, axon, synapse
• Neuronopathy
• Axonpathy
• Myelinopathy
• Transmission Toxicity

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Details about chemical agents

• Chlorine, Cyanide, Mustard gas, Soman, Sarin and
  VX gases are difficult to handle due to the low
  vapor pressure and susceptibility to
  environmental conditions
• Deployment would not involve an conventional
  explosive device but rather a pressure cylinder
  mechanism or glass container release in the HVAC
  intake for silent aerosol exposure

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First generation chemical agents

• WWI agents such as chlorine, cyanide, mustard
  gases have distinct odors and exposure to the gas
  cloud would need to be significant given the
  relatively high concentrations necessary to
  elicit symptoms
• WWI agents such as chlorine, cyanide, mustard
  gases have distinct odors and exposure to the gas
  cloud will be have to significant given relative
  high concentration necessary to elicit symptoms

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CHLORINE

• Today chlorine and anhydrous ammonia are the most
  common hazardous materials in interstate
  commerce.
• Chlorine is a greenish-yellow, noncombustible gas
  at room temperature and atmospheric pressure. The
  intermediate water solubility of chlorine
  accounts for its effect on the upper airway and
  the lower respiratory tract. The odor threshold
  for chlorine is approximately 0.3-0.5 parts per
  million (ppm).
• Contact may cause burns to skin and eyes however
  the major concern is inhalation toxicity
• Medical treatment move individual(s) to fresh
  air, administer oxygen if necessary

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CYANIDE

• Easy to obtain potassium cyanide and acid or base
  oxidizing reactants to release cyanide gas cloud
• Median lethal dose of potassium cyanide in man is
  200 mg and death occurring in 1 to 2 minutes
• Immediate exposure determination upon detection
  of almond-like odor
• A characteristic sign of cyanide poisoning is the
  bright red color of the blood in the comatose
  patient (some exceptions have been observed) due
  to the blood remaining fully oxygenated
• Medical treatment nitrate-thiosulfate antidote

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Mustard Gases

• 2,2-dichlorodiethylsulfide first synthesized in
  1859
• There are two types of mustards the sulfur
  mustard and the nitrogen mustard and both share
  common chemistry in the formation of cyclic onium
  cation and free chloride anion
• Both liquid and vapor forms are readily soluble
  in oils, fats and organic solvents
• Vesicant and blistering properties
• Immediate exposure determination upon detection
  of garlic/onion-like odor
• Medical treatment Nucleophilic scavengers such
  as Sodium thiosulfate others in this class
  thiocarbamates, thiophosphates, thiophosphonates,
  sulfhydryl-containing compounds.

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Anticholinesterase chemical classes

• Organophosphorus Esters
• Carbamate Esters
• Organophosphorus ester insecticides were first
  synthesized in 1937 by a group of German chemists
  led by Gerhard Schrader

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SOMAN

• Soman half-life is 82 hours at pH 7.0, 20 C
• Liquid and gaseous forms are odorless and
  colorless
• Similar to sarin and VX these chemicals strongly
  bind to acetylcholinesterase and effectively
  cause the over stimulation of nicotinic and
  muscarinic receptor by the lack of acetylcholine
  breakdown

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SARIN

• O-isopropyl methylphosphonofluoridate (commonly
  known as Sarin)
• Evidence of sarin usage by Iraq in 1988 against
  Kurdish villages in northern Iraq.
• Odorless and colorless chemical can be absorbed
  through the skin

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VX gas

• Of all chemical warfare agents, VX has the lowest
  vapor pressure and highest dermal absorption rate
• Chemical is odorless and colorless gas
• VX droplets would remain on shrubbery or other
  surface for about a week. In the absence of
  sunlight, toxicant has a half-life of 996 hours,
  pH 7, 25 C.

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Clinical symptoms

• Eye Miosis, dim vision or blurred vision
• Nose Rhinorrhea
• Mouth Excessive salivation
• Pulmonary tract Bronchoconstriction and
  secretions, cough, complaints of tight chest,
  shortness of breath
• Gastrointestinal increase secretions, vomiting,
  diarrhea, abdominal cramps, pain
• Skin Excess sweating
• Muscular twitching of muscle groups, flaccid
  paralysis, twiching
• Cardiovascular decrease or increase in heart
  rate
• Central nervous system loss of consciousness,
  convulsions, depression of respiratory center to
  produce apnea, coma

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Treatment of Organophosphorus ester poisoning

• Atropine is the standard treatment applied
  individuals showing symptoms of sweating,
  dilation of the pupil and salivation.
  Intravenous application of atropine is
  administered every 20-30 minutes until symptoms
  disappear. Pralidoxime administration has also
  been indicated.
• Prophylactic deployed during the Persian Gulf War
  consisted of pyridostygmine-bromine compounds

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Decontamination and isolation

• Generally all chemical agents noted are
  susceptible to hypochlorite treatment. For
  environmental decontamination consider 10
  hyperchlorite application. For skin, 0.5
  hyperchlorite application has been suggested.
• Note that for chlorine and G-agents are generally
  too volatile to remain on the skin long enough to
  allow absorption of much of the deposited dose
  and are too polar to penetrate the skin well.
  However, if agent is placed on clothing and
  covered it would penetrate the skin.
• On the other hand,VX gas is well absorbed through
  the skin therefore hypochlorite decontamination
  must occur instantaneously for unprotected
  individuals to receive any benefit from the
  disinfectant process.

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Lethal Concentrations for humans (LCt50)

• Hydrogen cyanide 2500 to 5000 mg x min per cubic
  meter
• Sarin 100 mg x min per cubic meter
• Soman 50 mg x min per cubic meter
• VX 10 mg x min per cubic meter
• All chemical agents are rapidly absorbed and
  quick acting such that hospital emergency
  responders handling the victims (excluding
  clothing) would be minimal and requiring basic
  PPE. On-scene emergency responders would require
  level A protective equipment
• Unlike toxins, these toxicants (Sarin, Soman, VX)
  should not be treated with soap and water for
  skin exposure instead use 0.5 hypochlorite
  solution if available.
• Open spaces with wind influence will quickly
  dilute toxic gases (except for VX) and most
  agents are susceptible to ultraviolet light
  inactivation over time. The problem are closed
  spaces such as buildings, gyms, convention halls.
  These areas require physical decontamination or
  increased ventilation actions. Note VX always
  requires inactivation for the environmental
  surroundings.