Merck Manual

Please confirm that you are a health care professional

honeypot link

Overview of Chemical-Warfare Agents

By

James M. Madsen

, MD, MPH, U.S. Army Medical Research Institute of Chemical Defense (USAMRICD)

Last full review/revision Feb 2021
Click here for Patient Education

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 only temporary, non–life-threatening effects)

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 Hazards Emergency Medical Management (CHEMM).

Classification

Toxic chemical warfare agents are divided into 4 major classes:

Nerve agents inhibit the enzyme acetylcholinesterase, causing excess cholinergic stimulation and cholinergic crisis (eg, diarrhea, urination, miosis, bronchorrhea, bronchoconstriction, emesis, lacrimation, salivation).

Because pulmonary agents include substances that also affect primarily 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 are thus termed blood agents in military references) and thus affect most tissues.

Vesicants damage the dermoepidermal junction, causing pain and typically blistering. Many can affect the lungs if inhaled.

Incapacitating agents can be divided into

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 far too easily cause death via respiratory depression. (See Opioid Toxicity and Withdrawal Opioid Toxicity and Withdrawal Opioids are euphoriants that, in high doses, cause sedation and respiratory depression. Respiratory depression can be managed with specific antidotes (eg, naloxone) or with endotracheal intubation... read more .) In mass-casualty situations, the route of exposure will most likely be inhalation of aerosolized agent; larger than usual doses of naloxone may be needed for fentanyl derivatives.

In addition to their chemical designations, most CW agents also have a 1- to 3-letter North Atlantic Treaty Organization (NATO) code.

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 Treatment Burns are injuries of skin or other tissue caused by thermal, radiation, chemical, or electrical contact. Burns are classified by depth (superficial and deep partial-thickness, and full-thickness)... read more Treatment .

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the US Government.

More Information

The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read
Test your knowledge
Snakebites
More than 60,000 bites and stings are reported to poison centers in the US each year, about 45,000 of which are snakebites (of which 7,000 to 8,000 are venomous and cause about 5 deaths). Which of the following types of snakes accounts for the majority of these bites and almost all deaths? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP