Nerve agents in chemical attacks
Nerve agents are a class of highly toxic chemical weapons that disrupt the nervous system, leading to incapacitation or death. These agents, which include substances like tabun, sarin, and VX, work by inhibiting the enzyme cholinesterase, causing an accumulation of the neurotransmitter acetylcholine. This buildup results in continuous nerve signaling, leading to symptoms such as chest tightness, dimming vision, and potentially rapid respiratory failure. The use of nerve agents has been notably rare but has occurred in historical conflicts, such as during the Iran-Iraq War and the Tokyo subway attack by the Aum Shinrikyo cult in 1995.
Nerve agents are categorized into various groups, including G-agents and V-agents, each with different properties and levels of toxicity. Modern developments, such as Novichok agents, have raised concerns due to their increased potency and ability to evade detection. Responding to nerve agent exposure requires specialized training and protective gear, and treatment typically involves antidotes like atropine and pralidoxime chloride. International treaties, like the Chemical Weapons Convention, aim to limit the production and usage of such agents, with efforts ongoing to safely dispose of existing stockpiles. The potential for terrorist groups to use these agents remains a serious concern, highlighting the importance of preparedness and public safety measures.
Nerve agents in chemical attacks
DEFINITION: Chemical weapons, usually liquid or gas, that incapacitate or kill by poisoning the nervous system.
SIGNIFICANCE: Given the deadly nature of nerve agents and the possibility that such substances could be used in terrorist attacks, law-enforcement personnel must be familiar with the various types of nerve agents, decontamination procedures, and treatments for exposure.
The earliest use of poison gases as weapons took place during World War I; the agents used were vesicants, or blister-causing agents, such as chlorine gas, phosgene gas, and mustard gas. These injured by inflicting chemical burns on the lungs (and, in the case of mustard gas, on the skin and eyes as well). The gases had to be deployed in massive quantities (six hundred tons was a common amount), inflicted a low death rate, and soon dispersed, and gas masks provided sufficient protection to potential targets. Nerve agents, in contrast, are extremely toxic and can contaminate an area for days or weeks; protection of targets requires full-body coverings in addition to masks.
Nerve agents function like modern organophosphate insecticides: They attack the nervous system. They inhibit the process by which cholinesterase neutralizes the neurotransmitter acetylcholine, thus clearing the nerve to transmit another signal. Acetylcholine then builds up in the nerves, causing the nervous system to malfunction; the nerves essentially transmit a continuous signal, causing the muscular system to lock up. The first symptoms—a feeling of tightness in the chest, dimming vision, and headache—may appear within seconds of exposure. Unconsciousness, coma, and death from respiratory paralysis follow within minutes or at most within a few hours. Survivors may suffer lasting impairment to their nervous systems.
G-Agents
Nerve gases are commonly divided into the three categories defined by the North Atlantic Treaty Organization (NATO): G-agents, V-agents, and Novichok agents. The first of these, the G-agents, were reportedly so named because they were German inventions. GA, or tabun, was discovered in 1936 by the German scientist Gerhard Schrader, who was researching insecticides. This agent is extremely toxic compared with the World War I vesicants, and unlike them, it is not simply a gas. At room temperature, it takes the form of a liquid that evaporates slowly (albeit more rapidly than its successor G-agents). It is colorless and has only a faint odor, described as fruity.
Although its primary lethal mechanism is inhalation, liquid tabun will penetrate the skin; exposure to a single droplet can kill. When tabun is delivered by an artillery round or missile warhead, a large area is splattered with droplets, lethal in themselves, the vapors from which contaminate the air for an extended period of time. Because the droplets can kill through skin contact, a gas mask is insufficient protection; the body must be fully covered. Ordinary clothing, however, can make tabun even more dangerous, as it can trap droplets and hold them in contact with the skin.
Tabun’s fumes are five times as dense as air, so they do not easily disperse into the atmosphere. Dangerous concentrations can, thus, remain for long periods in low-lying areas, including trenches and dugouts. Decontamination of areas contaminated with G-agents generally takes the form of rinsing the affected areas down with chlorine bleach. With tabun, however, this results in the release of toxic cyanogen chloride gas.
The second G-agent, known as GB or sarin, was invented by a German team in 1938. It is about twice as deadly as tabun (lethal skin dose for a human is less than a milligram) and so toxic that even its vapor can kill through skin exposure. Sarin evaporates more slowly than tabun, and, thus, its droplets can contaminate an area for a longer period.
Sarin has an unusual feature: It can be delivered as a binary agent, in the form of two or three harmless chemicals that, when mixed, convert into sarin. This makes sarin relatively safe to store, and it can be used in artillery shells, missile warheads, and bombs that are not dangerous until they are on the way to their targets.
Another G-agent, GD, or soman, was discovered by German scientist Richard Kuhn in 1944. GD, more deadly than sarin, can also be used as a binary agent. It is slower to evaporate than its predecessors and, thus, is a more persistent area contaminant. In its pure form, it is colorless and has only a faint odor. In impure forms, it can have a brown coloration and an odor resembling that of camphor.
GF, or cyclosarin, was invented in 1949. It is more persistent than its predecessors, evaporating at a speed about one-twentieth that of water and one-seventieth that of sarin. It is colorless and has a faint odor, variously described as similar to peaches or shellac.
By the end of World War II, Germany had produced about twelve thousand tons of nerve agents. Although the Germans held a technological advantage over their enemies, they were reluctant to initiate chemical warfare for a simple reason: Most of their artillery, and much of their transport, was still horse-drawn, and efforts to design gas masks for horses had proven unsuccessful. The Allies’ use of even World War I gases would have immobilized the Germans’ artillery and stopped much of their resupply efforts.
V-Agents
The G-agents were succeeded in the years following World War II by the British-created V-agents, known as VE, VG, VM, and VX. Like the G-agents, these originated with researchers seeking to create insecticides (VG was briefly marketed for that purpose until it was withdrawn owing to its extreme toxicity).
Of these, VX was the only variant chosen for development as a war gas. VX was developed in Great Britain in the 1950s, and its secret was traded to the United States in exchange for information on construction of thermonuclear warheads. The Soviet Union reportedly developed its own version, known in the West as VR and in the Soviet Union as Substance 33, and produced more than fifteen thousand tons of it.
VX possesses all the characteristics that make nerve agents so deadly. It is viscous (its consistency has been likened to that of motor oil), so that it adheres to objects and persons. It can be delivered in binary form. It evaporates very slowly, at about 1/1500th the rate of water. It is deadlier than its predecessors: A lethal skin dose is estimated at ten micrograms. When VX does evaporate, its fumes are nine times the density of air, so that it is not easily dispersed by wind.
Novichok Agents
For many years, VX represented the zenith of the development of nerve agents. That changed with Russia’s development of Novichok (Russian for “newcomer”) agents. Novichok agents take the form of a fine powder or dust that can evade modern chemical warfare protection equipment. These agents may be several times more potent than VX. Further, existing detection systems may not detect Novichok agents, and antidotes may not function against them. The existence of these agents was revealed in 1992 by Russian chemists Lev Fedorov and Vil Mirzayanov, who were imprisoned after they went public.
Responses to Nerve Agent Attacks
Nerve agents are potent area-denial weapons. That is, an area that is attacked with the use of such weapons will be dangerous for unprotected humans for an extended period unless it is completely washed down with decontaminates (typically chlorine bleach, although steam and ammonia may be used in restricted areas). As the smallest missed droplet can kill, decontamination must be exceptionally thorough. Below ground areas must be flushed of any vapors.
Treatment of casualties is likewise complicated. First responders must themselves wear protective outfits. Unprotected personnel must not have contact with any exposed person until that person has been undressed, any known droplets of agent on the body have been neutralized, and the hair has been washed.
The earliest antidote used in response to exposure to nerve agents was atropine, which is itself a toxin. Atropine counters the effects of nerve agents by binding to nerve receptor sites and blocking excess acetylcholine. Biperiden, originally developed for use against Parkinson’s disease, is also useful. Pralidoxime chloride (2-PAM chloride, known in the military simply as 2-PAM) offers a more direct and safe approach, in that it reactivates the acetylcholinesterase deactivated by the nerve agent. Treatment with 2-PAM must be begun more quickly than treatment with atropine, as 2-PAM takes effect more slowly. Military personnel are commonly issued kits containing self-injectors of atropine and 2-PAM if nerve agents are considered to be a risk. Diazepam can also be employed to counteract convulsions caused by nerve agents.
Employment of Nerve Agents
The deployment of nerve agents has been mercifully rare. During the Iran-Iraq War (1980–88), Iraq used tabun, sarin, and cyclosarin against Iranian infantry and later used these agents to kill thousands of Kurds. In Japan, the Aum Shinrikyo religious cult used homemade sarin in a 1995 attack on the Tokyo subway system. Owing to the crude nature of the material used and a rather inept delivery system (leaky cans left in subway cars), casualties in that incident were held to twelve deaths and about five thousand hospitalizations.
The risk of future use may be curtailed by treaties. Early agreements such as the Geneva Protocol of 1925 forbade the use of poisonous gases, but not their manufacture and storage. Later, the Chemical Weapons Convention of 1993, which entered into force in 1997, requires signatory nations to destroy existing stockpiles of nerve agents. In the United States, government efforts to destroy such stockpiles by breaking the substances down chemically and discharging the byproducts into water have encountered objections from groups concerned with possible negative environmental impacts. However, in 2023, the United States destroyed its last M55 rocket filled with sarin at a storage facility in Kentucky. The country once had 30,600 tons of chemical warfare agents. Among signatory nations, the United States was the last country to comply with the Chemical Weapons Convention treaty.
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