Nerve agents exposure route

Since the onset of effects caused by nerve agent exposure may occur as long as 18 hours after skin contact, prolonged observation is prudent. The longer the interval until the onset of signs and symptoms, the less severe they will be, but medical assistance will still be necessary. Since vapor (or inhaled aerosol) causes effects within seconds or minutes, it is extremely unlikely that a suspected asymptomatic casualty would be produced by this route. 

The recommended dose of pralidoxime for nerve agent exposure is variable, depending on the route of exposure and the severity of the poisoning. 

DF and its precursor, DC are organophosphonic acids. They will react with alcohols to form crude lethal nerve agents, such as crude GB. High overexposure may cause inhibition of cholinesterase activity. Although much less toxic than GB, DF and DC are toxic and corrosive materials. Because DF and DC are relatively volatile compounds, the primary route of exposure is expected to be the respiratory system. However, ingestion also results from inhalation exposures in animals and could occur in humans. DF and DC vapors have a pungent odor and may cause severe and painful irritation of the eyes, nose, throat, and lungs. Data provided is for DF only, DC has similar properties. 

Nerve agents are hazardous through any route of exposure including inhalation, exposure of the skin and eye, ingestion, and broken, abraded, or lacerated skin (e.g., penetration of skin by debris). 

Toxins present a variety of both incapacitating and lethal effect. Most toxins of military significance can be broadly classified in one of two ways. Neurotoxins disrupt the nervous system and interfere with nerve impulse transmission similar to nerve agents (Chapter 1). However, all neurotoxins do not operate through the same mechanism of action or do they produce the same symptoms. Cytotoxins are poisons that destroy cells or impair cellular activities. Symptoms may resemble those of vesicants (Chapter 3) or they may resemble food poisoning or other diseases. Toxins may also produce effects that are a combination of these general categories. The consequences of intoxication from any individual toxin can vary widely with route of exposure and dose. In addition, some toxins act as biomediators and cause the body to release excessive, and therefore harmful, amounts of chemicals that are normally produced by the body. 

Muscle fasciculations and eventual paralysis may occur. Symptoms usually occur within seconds of exposure to a nerve agent hut may take several hours when exposure is only transdermal (see Figure 25.1). Effects and time of onset of a nerve agent are dependent on the concentration of the agent and the amount of time exposed, as well as the route of exposure. 

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