This lecture Conceptual framework nato codes General concepts Chemical Agent: Definition (fm 8-285)

Chemical-warfare Agents: An Overview

Objectives

• Course

• Overview and relevance
• Agent characteristics and effects
• Patient presentation and management

• This lecture

• Conceptual framework
• NATO codes
• General concepts

Chemical Agent: Definition (FM 8-285)

• “A chemical substance…intended for use in military operations to kill, seriously injure, or incapacitate humans (or animals) through its toxicological effects.”

• Compare and contrast

• Chemical agents (chemical-warfare agents)
• Biological agents (biological-warfare agents)
• Toxins
• “Toxicants”

Chemical Agent: Definition (FM 8-285)

• “A chemical substance…intended for use in military operations to kill, seriously injure, or incapacitate humans (or animals) through its toxicological effects.”

• Excluded by FM 8-285

• Riot-control agents (CS, CN, DM)
• Chemical herbicides (e.g.. Agent Orange)
• Smoke and flame materials

Excluded Agents I: Riot-control Agents

• Irritant agents (lacrimators)

• CS (“tear gas”)
• CN (Mace©)
• CA
• CR

• Vomiting agents

• DM (Adamsite)
• DA
• DC

Riot-control Agents

• Local irritants with high safety ratio

• Short onset (seconds to minutes)

• Short duration (15-30 minutes)

• In low concentrations, cause intense pain and lacrimation (tearing) with (Adamsite only) or without vomiting

Excluded Agents II: Herbicides (Defoliants)

• Agent Blue (cacodylic acid)

• Agent Orange (1:1 mixture of 2.4.5-T and 2.4-D)

• Contaminant: TCDD (Dioxin)

• Agent White (4:1 mixture of 2.4-D and picoram)

• Paraquat

Excluded Agents III: Smokes

• Petroleum oil smokes (fog oil=SGF)

• Diesel fuel

• HC

• RP (RED phosphorus) in butyl rubber

• WP (WHITE phosphorus)

• FS

• FM

Classification of “Official” Chemical Agents

• TOXIC AGENTS (producing injury or death)

• LUNG-DAMAGING AGENTS (choking agents)
• Chlorine (CL), phosgene (CG) [smokes] [vesicants]
• “BLOOD” AGENTS (cyanogens): AC and CK
• BLISTER AGENTS (vesicants)
• Mustard (H), Lewisite (L), phosgene oxime (CX), [riot-control agents] [T-2 mycotoxin]
• NERVE AGENTS (anticholinesterases)
• GA,GB,GD,GF,VX

• INCAPACITATING AGENTS (producing temporary effects)

• BZ, Agent 15, [riot-control agents]

“Official” Chemical Agents I: Toxic Agents

• Lung-damaging agents (choking agents)

• Chlorine (CL), phosgene (CG) [smokes] [vesicants]

• “Blood” agents (cyanogens): AC and CK

• Blister agents (vesicants)

• Mustard (H), Lewisite (L), phosgene oxime (CX), [riot-control agents] [T-2 mycotoxin]

• Nerve agents (anticholinesterases)

• GA,GB,GD,GF,VX

Lung-damaging Agents

• Chlorine (CL)

• Chloropicrin (PS)

• Phosgene (CG)

• Diphosgene (DP)

• [Mustard (HD, H) Lewisite (L)]

• [Smokes] [isocyanates] [PFIB] [oxides of nitrogen]

Chemical-agent Damage to Respiratory System

• Central effects (in larynx, trachea, and bronchi) predominate

• Mustard (H, HD)
• Lewisite (L)
• [Chlorine (CL)]

• Peripheral effects (in small airways and alveoli) predominate

• Phosgene (CG)
• Perfluoroisobutylene (PFIB)
• Nitrogen oxides (NOx)
• HC smoke, isocyanates, many others

“Blood” Agents (Cyanogens)

• Hydrogen cyanide (AC)

• Cyanogen chloride (CK)

Blister Agents (Vesicants)

• Sulfur mustard (H, HD)

• Nitrogen mustard (HN1, HN2, HN3)

• Lewisite = chlorovinyldichloroarsine (L)

• Mustard / Lewisite mixtures (HL, HT, TL)

• Phosgene oxime (CX)

• [Riot-control agents]

• [T-2 mycotoxin]

Nerve Agents (Anticholinesterases)

• Tabun (GA)

• Sarin (GB)

• Soman (GD)

• GF

• VX

“Official” Chemical Agents II: Incapacitating Agents

• Purpose: Temporary incapacitation

• CNS stimulants

• Amphetamines, cocaine, caffeine, nicotine, strychnine, metrazole

• CNS depressants

• Barbiturates, opioids, antipsychotics, benzodiazepines

• Psychedelics

• LSD-25, psilocybin, ibogaine, harmine, MDMA (“ecstasy”), PCP

• Deliriants

• Anticholinergic glycolates (BZ, Agent 15)

Physical Forms of Chemical Agents

• Solid

• Liquid

• Gas

• Vapor

• Aerosol

Persistence

• Dependent on several factors

• Agent volatility (determined by chemical structure)
• Temperature
• Wind
• Agent-surface interactions

• “Nonpersistent” agents (usually gone within 24 hours)

• GA, GB, GD, CL, CG, AC, CK

• “Persistent” agents

• VX, L, HL, “thickened” nerve and blister agents (e.g., TGD, THD)

Exposure and Absorption

• Exposure (contact with agent) does not necessarily lead to absorption (penetration of epithelial barrier)

• Two types of effects from exposure and absorption:

• Local
• (effects are at the site of contact)
• Systemic
• (absorption and subsequent systemic distribution produce effects at sites distant from contact site)

Routes of Exposure and Absorption

• Absorption through skin (percutaneous absorption)

• Absorption through lungs (inhalational absorption)

• Absorption through eyes (ocular absorption)

• Absorption through the gut (enteral absorption)

• Absorption by injection (parenteral absorption)

• Intravenous absorption
• Intramuscular absorption

Toxicity (Potency) of Liquid Agents

• ED50: Effective Dose for 50% of exposed individuals

• ID50: Incapacitating Dose for 50% of exposed individuals

• LD50: Lethal Dose for 50% of exposed individuals

• ID50 for liquid HD: 770 mg / 70-kg man

• LD50 for liquid HD: 3000-7000 mg / 70-kg man

Toxicity of Vapors or Gases

• The Ct concept: Concentration x time

• 1 mg / m3 x 8 min = 8 mg-min / m3

• 8 mg / m3 x 1 min = 8 mg-min / m3

• 4 mg / m3 x 2 min = 8 mg-min / m3

• 2 mg / m3 x 4 min = 8 mg-min / m3

Toxicity of Vapors or Gases

• ECt50: Effective Ct for 50% of exposed individuals

• ICt50: Incapacitating Ct for 50% of exposed individuals

• LCt50: Lethal Ct for 50% of exposed individuals

• Ct50 assesses external dose, not internal dose

• ICt50 and LCt50 therefore affected by
• Route of exposure
• Respiratory rate and depth, skin moisture, etc.

Toxicity of HD Vapor

• HD vapor in eyes:

• ICt50: 200 mg-min / m3

• Inhaled HD vapor:

• ICt50: 200 mg-min / m3

• HD vapor on skin:

• ICt50: 1000-2000 mg-min / m3

Toxicity of HD Vapor

• HD vapor in eyes:

• Permanent injury: > 800 mg-min/ m3

• Inhaled HD vapor:

• LCt50: 1000-1500 mg-min / m3

• HD vapor on skin:

• LCt50: 10,000 mg-min / m3

Comparative Toxicity of CW Agents

Medical Response to CW Threats

A Framework for Learning about Chemical Agents

• History / background

• Physicochemical properties

• Toxicokinetics (ADBE) [how the body handles the agent]

• Toxicodynamics (mechanism of action) [how the agent “handles” the body]

• Clinical presentation / diagnosis: ASBESTOS

• Management

• Protection, general supportive treatment, and antidotal treatment
• Decontamination and evacuation

“ASBESTOS”: A Systematic Approach to the Patient

• Agent(s): Type and toxicity (remember LD50)

• State(s): Solid? Liquid? Gas? Vapor? Aerosol?

• Body site(s): Where exposed / Route(s) of entry? [absorption]

• Effects: Local? Systemic? [distribution]

• Severity: Mild? Moderate? Severe? [effects and exposure]

• Time course: Onset? Getting better/worse? Prognosis?

• Other diagnoses? Instead of? [DDx] In addition to?

• Synergism: Combined effects of multiple exposures or insults?

Summary: “Official” Chemical Agents

• TOXIC AGENTS (producing injury or death)

• LUNG-DAMAGING AGENTS (choking agents)
• Chlorine (CL), phosgene (CG) [smokes] [vesicants]
• “BLOOD” AGENTS (cyanogens): AC and CK
• BLISTER AGENTS (vesicants)
• Mustard (H), Lewisite (L), phosgene oxime (CX), [riot-control agents] [T-2 mycotoxin]
• NERVE AGENTS (anticholinesterases)
• GA,GB,GD,GF,VX

• INCAPACITATING AGENTS (producing temporary effects)

• BZ, Agent 15, [riot-control agents]