Weapons of Mass Destruction: Chemical Agents and Toxins

Esequiel Barrera, SM (TOX) Biol/Chem Safety Officer University of Texas Southwestern Medical Center at Dallas

Points of Discussion

• Agent characteristics • History of use • Modes of action • Clinical Manifestations • Medical treatment • Personal Protective Equipment • Decontamination Acute Toxicity • Chlorine gas • Cyanide gas • Mustard gas • Incapacitants • Nerve gas • Botulinum toxin • Ricin • T2 Mycotoxin

Chlorine Gas

• Chlorine is a powerful oxidizing agent • Household chemicals such as sodium hypochlorite/pool chlorine tablets and muriatic acid (HCl) when mixed produce chlorine gas • Chlorine and anhydrous ammonia are the most common hazardous materials in interstate commerce

Chlorine: Physical Characteristics

• Chlorine gas is a respiratory irritant which affects the mucous membranes • Chlorine is a toxic, corrosive, greenish yellow gas • Gas is two and a half times heavier than air. It becomes a liquid at -34° C (-29° F)

Chlorine: Health risks

• Contact may cause burns to skin and eyes however the major concern is inhalation toxicity • It can be fatal after a few breaths at 1000 ppm.

• Chlorine odor threshold ~0.3 to 0.5 ppm • Medical treatment: move individual(s) to fresh air, administer oxygen if necessary • Post-exposed Individuals generally recover to normal state

Chlorine: Symptoms

• Cough (52-80%) • Shortness of breath (20-51%) • Chest pain (33%) • Burning sensation in the throat and substernal area (14%) • Nausea or vomiting (8%) • Ocular and nasal irritation (4 6%)

Incapacitant

• Under the Department of Defense definition, an incapacitant is an agent that produces temporary physiological or mental effects, or both, which will render individuals incapable of concerted effort in the performance of their assigned duties

Incapacitants

• The chemical warfare agent 3 quinuclidinyl benzilate (QNB, BZ) is an anticholinergic agent that affects both the peripheral and central nervous systems (CNS). It is one of the most potent anticholinergic psychomimetics known, with only small doses necessary to produce incapacitation. It is classified as a hallucinogenic chemical warfare agent.

Incapacitants

• QNB usually is disseminated as an aerosol, and the primary route of absorption is through the respiratory system. Absorption also can occur through the skin or gastrointestinal tract. It is odorless. QNB's pharmacologic activity is similar to other anticholinergic drugs (eg, atropine) but with a much longer duration of action.

First generation chemical agents

• WWI agents such as cyanide and mustard gases introduced the horror of chemical warfare • http://www.superevi

l.tv/rommel/rommel.

htm

Hydrogen Cyanide Gas

• Easy to obtain potassium cyanide or other salts and react with acid to release cyanide gas cloud • First synthesized in 1782 • Colorless gas, bitter almond 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 • Blood agent

Cyanide: Toxicology

• Median lethal dose of potassium cyanide in man is 200 mg (taken orally) and death occurring in 1 to 2 minutes • Hydrogen cyanide can cause rapid death due to metabolic asphyxiation.

• LC(50) in humans is 270 ppm in 6 to 8 minutes. • Medical treatment: nitrate thiosulfate combination antidote

Cyanide: Biochemical

• Lipid Peroxidation • Elevated cell calcium • Acidosis • Ribosylation of mitochondrial protein • Elevated blood ammonia and amino acids

Cyanide: chronic exposure

• Headaches, weakness, changes in taste and smell, irritation of the throat, vomiting, effort dyspnea, lacrimation, abdominal colic, precordial pain, and nervous instability.

Mustard Gases

• 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, can be quickly absorbed through the skin

Mustard Gases: Mode of action

• 2-4 hours experience chest tightness, sneezing, lacrimation, rhinorrhea, epistaxis, hacking cough • Vesicant (blistering) properties, 2-3 days later.

• Immediate exposure determination upon detection of garlic/onion like odor • No effective medical treatment due to nonspecific alkylating nature of agent • http://www.opcw.org/re sp/html/mustard.html

Mustard gas

• More individuals have died of mustard gas than any other chemical agent or toxin • Most of these deaths happened during WWI • Emergency care effective less than 3% of WWI casualities results in death. • http://www.opcw.org/resp/htm l/mustard.html

Mustards: Decontamination

• Efforts must be made to treat the symptoms. By far the most important measure is to rapidly and thoroughly decontaminate the patient and thereby prevent further exposure. This decontamination will also decrease the risk of exposure to staff. • Clothes are removed, the skin is decontaminated with a suitable decontaminant and washed with soap and water. If hair is suspected to be contaminated then it must be shaved off. Eyes are rinsed with water or a physiological salt solution for at least five minutes.

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

Inhibitors of acetylcholinesterase

• Soman, Sarin and VX these chemicals strongly bind to acetylcholinesteras e and effectively cause the over stimulation of nicotinic and muscarinic receptor by the lack of acetylcholine breakdown

SOMAN

• Soman half-life is 82 hours at pH 7.0, 20 C • Liquid and gaseous forms are odorless and colorless • Can be absorbed through the skin but generally considered non persistent

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, non-persistent • 1995 Tokyo Sarin attack by Aum Shinrikyo religious cult

VX gas

• Most potent chemical nerve agent with 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.

Chemical Nerve Agents: 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 Nerve Agents

• Atropine (muscarinic cholinergic antagonist) 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. In addition, Pralidoxime administration (2PAM-Cl) 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.

Details about chemical agents

• Cyanide, Mustard gas, Soman, Sarin and VX gases are difficult to handle due to the low vapor pressure and susceptibility to environmental conditions • 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.

• 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

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 • Unlike toxins, Sarin, Soman, VX, should not be treated with soap and water for skin exposure instead use 0.5% hypochlorite solution if available. Skin absorption too quick.

Toxins as Weapons of Mass Destruction

• Botulinum Toxin – Most potent toxin known to man – Toxin is produced by a bacteria • Ricin Toxin – Recent events involving ricin – Toxin is produced by a plant • T-2 Mycotoxins – Difficult to detect (not recognized by M8 paper or M256 kit used for Mustard gases – Toxin is produced by a fungus

Botulinum toxin

•

• Clostridium botulinum • Anaerobic, gram positive, rod shaped bacteria • Food poisoning cases • LD50 is 0.001 ug/kg, most potent toxin known to man • FDA approved Botox http://microvet.arizona.edu/Courses/MIC420/l ecture_notes/clostridia/clostridia_neurotox/gr am_c_botulinum.html

Botulinum Toxin: Clinical Symptoms

• Ptosis, generalized weakness, dizziness, dry mouth and throat, blurred vision and diplopia, dysarthria, dysphonia, and dysphagia followed by symmetrical descending flaccid paralysis and development of respiratory failure. Symptoms begin as early as 24-36 hours but may take several days after inhalation of toxin.

Botulinum Toxin: Medical Treatment

•

Treatment:

Intubation and ventilatory assistance for respiratory failure. Tracheostomy may be required. Administration of heptavalent botulinum antitoxin (IND product) may prevent or decrease progression to respiratory failure and hasten recovery.

Botulinum Toxin: Decontamination and Isolation • Standard Precautions for healthcare workers. Toxin is not dermally active and secondary aerosols are not a hazard from patients. Hypochlorite (0.5% for 10-15 minutes) and/or soap and water.

Differences between chemical nerve agents and Botulinum toxin Chemical Agent Minutes Convulsions, Muscle twitching Ocular: Small pupils Atropine/2-PAM-Cl responsive Botulinum toxin Hours (12-48) Progressive paralysis Ocular: Large pupils Atropine/2-PAM-Cl: no effect

Ricinus communis

plant

Bean Pods

• Seed color varies from white to brown with wave patterns

http://waynesword.palomar.e

du/plmar99.htm#flow

Castor Beans

• Worldwide one million tons of castor beans are processed annually in the production of castor oil (waste mash is ~5% ricin by weight) • Castor oil used as a mechanical lubricate, contains no ricin

http://museum.gov.ns.ca/poison/cas tor1.htm

RICIN OVERVIEW

• Ricin is a heterodimeric protein toxin, 64Kd. • The ricin A chain is able to cross the membrane of intracellular compartments to reach the cytosol where it catalytically inactivates protein synthesis. It is linked via a disulfide bond to the B chain, a galactose-specific lectin, which allows ricin binding at the cell surface and endocytosis.

• Cancer and autoimmune treatment applications

Ricin History and Significance

• Assassination of Bulgarian exile Georgi Markov in London (1978) • Minnesota Patriots Council (1994 and 1995) and Thomas Leahy, Wisconsin (1997) • Deborah Green, Kansas (1995) • al Qaeda cell, London (2003)

Ricin Toxicology

• Potent protein and DNA synthesis inhibitor • LD50 for mice is 3.0 ug/kg • Comparative lethality: LD50 for Botulinum toxin (bacterium) is 0.001 and for VX gas (chemical agent) is 15.0

• LD50 for humans is uncertain and varies with route of entry (ricin vs ricinine)

Ricin Agent Characteristics

• Ricin is environmentally stable with 3 day survival in dry conditions • No person to person transmission • Lethality is high with death occurring 10-12 days for ricin ingestion and 3-4 days for inhalational exposure

Ricin Identification

• Gold Standard technique is enzyme linked immunosorbent assays (ELISA) -antigen detection -IgG immunoassay -IgM immunoassay

Ricin Prophylaxis

• There is currently no commercial vaccine or prophylactic antitoxin available for human use albeit animal immunization studies have been promising • Protective mask and engineering controls are currently the best protection

Inhalational ricin exposure: Signs and Symptoms

• 4 to 8 hours: Acute onset of fever, chest tightness, cough, dyspnea, nausea and arthralgias • 18-24 hours: Airway necrosis and pulmonary capillary leak leading to pulmonary edema • 36-72 hours: severe respiratory distress and death from hypoxemia

Ricin Medical Sampling

• Early Post-exposure (0-24 h): nasal swabs, induced respiratory secretions for PCR (contaminating castor bean DNA) and Serum for toxin assays • Clinical (36-48 h): serum for toxin assay and tissues for immunohistological stain in pathology samples • Postmortem (>6 days): Serum for IgM and IgG

Ricin Treatment

• Ingestional entry: Gastric lavage and cathartics are indicated. Charcoal application is of little value for large molecules such as ricin • Inhalation entry: Pulmonary edema treatment and supportive management

Ricin Decontamination

• Ricin inactivation can be accomplished with bleach (1% sodium hypochlorite, 20 min) or autoclave treatment (80C for 10 min) • Intact skin surface decontamination use soap and water (dilution).

T-2 Mycotoxins

• Trichothecene (T-2) mycotoxins produced by the fungi of genus Fusarium (common grain mold) • Extremely stable in the environment • Toxin is dermally active causing blisters (minutes to hours after exposure)

T2 History and Significance

• Shortly after WWII, flour contaminated with Fusarium unknowingly baked into bread and ingested by civilians. Exposed individuals developed a protracted lethal illness called alimentary toxic aleukia (ATA).

• “Yellow rain” incidents in Laos (1975 81), Kampuchea (1979-81) and Afghanistan (1979-81).

T2 Toxin Characteristics

• Trichothecene are relatively insoluble in water • Compounds are extremely stable to heat and ultraviolet light inactivation • Bioactivity retained even after standard autoclaving (inactivation requires 1500 F for 30 minutes) • Hypochlorite solution alone does not inactive the toxins • Toxin rapidly inhibit protein and nucleic acid synthesis

T2: Clinical Features

• Routes of exposure: penetration through the skin, inhalation and ingestion.

• Contaminated clothing can serve as a reservoir for further toxin exposure • Early symptoms (minutes after skin exposure): burning skin, redness, tenderness, blistering and progression to skin necrosis with leathery blackening and sloughing of large areas of the skin • Pulmonary/tracheobronchial toxicity produces dyspnea, wheezing and cough.

• Gastrointestinal toxicity causes pain and blood tinged saliva and sputum • Death may occur in minutes, hours or days • Most common symptoms: vomiting, diarrhea, skin involvement with burning pain, redness, rash or blisters, bleeding and dyspnea.

T2: DIAGNOSIS

• Physical clues yellow, red, green or other pigmented oily liquid • Contact with the skin (unlike ricin) forms characteristic symptoms • Generally considered odorless • Serum and urine should be collected to be sent to a reference lab for antigen detection (gas liquid chromatography-mass spectrometry technique)

T2: MEDICAL TREATMENT

• Toxin inactivation requires 0.1M NaOH added to 1% hypochlorite solution for a duration of one hour.

• No specific antidote or therapeutic regimen is currently available.

• Exposed individuals: remove clothing, wash skin with soap and water.

• Standard burn care is indicated for cutaneous involvement • Toxin ingestion use superactivated charcoal • Aerosol attack: respiratory support may be required, rinse out eyes with saline or water.

• Only physical protection of the skin, mucous membranes and airway are the only proven effective methods of protection during an attack.

Text References

• Klaassen, Curtis D. (1996) Casarett and Doull’s Toxicology, The Basic Science of Poisons, fifth edition. The McGraw-Hill Companies, Inc.

• Somani, Satu M. (1992) Chemical Warfare Agents, Academic Press, Inc.

• Satellite Broadcast September 26-28, 2000 Biological Warfare and Terrorism, Medical Issues and Response (Student Material Booklet). Sponsored by the United States Army Medical Research Institute of Infectious Diseases and the Food and Drug Agency

Acknowledgements

Gulf War Syndrome Research UT Southwestern: Department of Epidemiology • Christopher Sinton, PhD. • Robert Haley, MD.

Ricin Research Endeavors UT Southwestern: Cancer Immunobiology Center • Joan Smallshaw, PhD.

• Ellen Vitetta, PhD.