Chemical-warfare (CW) agents are chemical mass-casualty weapons (MCWs) developed by governments for wartime use and include:
Toxic agents, intended to cause serious injury or death
Incapacitating agents, intended to cause temporary, non–life-threatening effects
Incendiary agents, intended to produce light and flame
Although incapacitating agents are sometimes mistakenly referred to as nonlethal, in high doses, these agents can cause serious injury or death.
Toxic industrial chemicals are chemicals produced for industrial uses that are capable of causing mass casualties. Some chemicals (eg, chlorine, phosgene, cyanide compounds) have both industrial and CW uses and are called dual-use agents.
A useful online and downloadable resource for incidents involving chemical agents is Chemical Hazard Emergency Medical Management (CHEMM).
(See also Overview of Incidents Involving Mass-Casualty Weapons.)
Classification of Chemical-Warfare Agents
Toxic chemical warfare agents are divided into 4 major classes:
Systemic asphyxiants (blood agents)
Vesicants (blistering agents)
Nerve agents inhibit the enzyme acetylcholinesterase, causing excess cholinergic stimulation and cholinergic crisis (eg, diarrhea, urination, miosis, bronchorrhea, bronchoconstriction, emesis, lacrimation, salivation).
Because many pulmonary agents primarily affect the upper respiratory tract rather than lung parenchyma, some experts prefer to call this class “agents with acute local effects on the respiratory tract.” Because most toxic industrial chemicals capable of generating mass casualties affect the respiratory tract, they are discussed with pulmonary CW agents.
Systemic asphyxiants, specifically cyanide compounds and hydrogen sulfide, interfere with mitochondrial energy transport, blocking cellular respiration. They are distributed in the blood and thus affect most tissues. Military references identify such agents as "blood agents."
Vesicants damage the dermoepidermal junction, causing pain and typically blistering. Many vesicants can also affect the lungs if inhaled.
Incapacitating agents can be categorized as:
Riot-control agents, commonly and incorrectly called "tear gas," are dispersed as solid aerosols or as solutions (Note: The U.S. military does not consider riot-control agents to be chemical warfare agents.)
Opioids, especially potent fentanyl derivatives
Opioids, such as the potent fentanyl derivatives reputedly used by Russia against Chechnyan terrorists in 2002, can be considered incapacitating in that their use is not typically intended to cause serious injury or death. However, when they are used as mass-casualty weapons they can easily cause death via respiratory depression. (See Opioid Toxicity and Withdrawal.) In mass-casualty situations, the route of exposure will most likely be inhalation of an aerosolized agent; larger than usual doses of naloxone may be needed for treatment when exposure is to fentanyl derivatives.
In addition to their chemical designations, most CW agents also have a 1- to 3-letter North Atlantic Treaty Organization (NATO) code (eg, nerve agents GA [agents tabun], GB [sarin], GD [soman], and GF [cyclosarin]) (1, 2).
Incendiary agents, designed to create light and flame, may also cause thermal burns in large numbers of casualties. Hydrogen fluoride (HF) may likewise cause chemical burns. Some of these burns require specific management apart from the typical management of thermal burns.
References
1. Chauhan S, Chauhan S, D'Cruz R, et al. Chemical warfare agents. Environ Toxicol Pharmacol. 2008;26(2):113-122. doi:10.1016/j.etap.2008.03.003
2. Bland SA. Chemical, Biological, Radiological and Nuclear (CBRN) Casualty Management Principles. Conflict and Catastrophe Medicine. 2013;747-770. Published 2013 Jul 18. doi:10.1007/978-1-4471-2927-1_46
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