Presentation on theme: "Chemical Nerve Agents Esequiel Barrera, SM (TOX) Biol/Chem Safety Officer at UTSWMC, Dallas."— Presentation transcript:
Chemical Nerve Agents Esequiel Barrera, SM (TOX) Biol/Chem Safety Officer at UTSWMC, Dallas
Toxic Responses of the Nervous System Normal Neural function: neuron, nissl substance, myelinating cell, axon, synapse Neuronopathy Axonpathy Myelinopathy Transmission Toxicity
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
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
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
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
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.
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
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
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
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.
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
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
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.
Lethal Concentrations for humans (LCt 50 ) 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.