Nerve Agents


 2-1. General

a.    Nerve agents are a group of highly toxic organic esters of phosphoric acid derivatives. These agents have physiological effects (inhibition of cholinesterase) resembling those of physostigmine and pyridostigmine. However, they are more potent, longer-acting, and tend to be irreversible after a time which varies with the agent.

b.    Nerve agents are among the deadliest of chemical agents and may produce rapid symptoms. They include the G- and V-agents. Examples of G-agents are Tabun (GA), Sarin (GB), Soman (GD), and GF. A V-agent is VX. In some countries, "V" agents are known as "A" agents. (Detailed descriptions of nerve agents are found in FM 3-9.)

c.    Nerve agents can be dispersed by artillery shell, mortar shell, rocket, land mine, missile, aircraft spray, and aircraft bomb or bomblet. d.    Several related but somewhat less toxic compounds have proven to be useful in medicine and agriculture, as indicated below. The symptoms and treatment of poisoning by these compounds are similar to those of poisoning by nerve agents.

(1)    Anticholinesterase agents have been used in the treatment of abdominal distention, urinary retention, and glaucoma.

(2)    Many of the insecticides currently in use are organophosphates and are chemically related to nerve agents. Although beneficial for arthropod control, their widespread use has caused many accidental poisonings - some fatal. Organophosphate insecticides may have a slower and longer lasting effect as compared to CW organophosphates.

2-2. Physical and Chemical Properties

Nerve agents are colorless to light brown liquids. Some are volatile, while others are relatively non-volatile at room temperature. Most nerve agents are essentially odorless; however, some have a faint fruity odor. In toxic amounts, aqueous solutions of nerve agents are tasteless. The G-agents tend to be nonpersistent, whereas the V-agents are persistent. However, thickened nonpersistent agents may present a hazard for an extended period of time. These agents are moderately soluble in water with slow hydrolysis; are highly soluble in lipids; and are rapidly inactivated by strong alkalies and chlorinating compounds (strong alkalies and chlorinating compounds are used for decontaminating equipment; in diluted formulas, chlorinating compounds are used for patient de-contamination).

2-3. Absorption of and Protection Against Nerve Agents

a.    Nerve agents may be absorbed through any body surface. When dispersed as a spray or aerosol, droplets can be absorbed through the skin, eyes, and respiratory tract. When dispersed as a vapor at expected field concentrations, the vapor is primarily absorbed through the respiratory tract. If enough agent is absorbed, local effects are followed by generalized systemic effects. The rapidity with which effects occur is directly related to the amount of agent absorbed in a given period of time. Liquid nerve agents may be absorbed through the skin, eyes, mouth, and membranes of the nose. Nerve agents may also be absorbed through the gastrointestinal tract when ingested with food or water. Local effects after skin exposure are localized sweating and/or muscular twitching. Local effects after vapor or liquid exposure to the eye include miosis and often conjunctival hyperemia. Local effects of liquid on the mucous membrane include twitching or contracting of the underlying muscle and glandular secretions. Ab-sorption of a nerve agent by any route may result in generalized systemic effects. The respiratory tract (inhalation) is the most rapid and effective route of absorption.

b.    The protective mask and hood protect the face and neck, eyes, mouth, and respiratory tract against nerve agent spray, vapor, and aerosol. Nerve agent vapor (in expected field concentrations) is absorbed through the skin very slowly, if at all, so proper masking may protect against the effects of low vapor concentrations. To prevent inhaling an incapacitating or lethal dose, hold your breath and put on your mask within 9 seconds at the first warning of a nerve agent presence.

c.    Liquid nerve agents penetrate ordinary clothing rapidly. However, significant absorption through the skin requires a period of minutes. The effects may be reduced by quickly removing contaminated clothing and neutralizing liquid nerve agent on the skin (washed off, blotted, or wiped away). Prompt decontamination of the skin is imperative. Decontamination of nerve agents on the skin within 1 minute after contamination is perhaps ten times more effective than it would be if delayed 5 minutes. A nerve agent on the skin can be removed effectively by using the M291 Skin Decontaminating Kit or the M258A1 Skin Decontamination Kit (app D). The M291 Skin Decontaminating Kit is replacing the M258A1. Upon receipt of the M291, discontinue using the M258A1 on the skin. Liquid nerve agent in the eye is absorbed faster than on the skin and is extremely dangerous; immediately irrigate the eye with copious amounts of water.

d.    The chemical protective overgarment, patient protective wrap (PPW), impermeable protective gloves, and overboots protect the skin against nerve agents in liquid, aerosol, and vapor forms.


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