Vesicants incapacitation caused

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. 

The skin and eyes are especially sensitive to the toxic effects of sulfur mustard. When applied to human skin, about 80% of the dose evaporates and 20% is absorbed (Vogt et al., 1984). About 12% of the amount absorbed remains at the site and the remainder is distributed systemically (Renshaw, 1946). Doses up to 50 pg/ cm cause erythema, edema, and sometimes small vesicles. Doses of 50-150 pg/cm cause bullous-type vesicles, and larger doses cause necrosis and ulceration with peripheral vesication. Droplets of liquid sulfur mustard containing as little as 0.0025 mg may cause erythema (Ward et al., 1966). Eczematous sensitization reactions were reported in several early studies and may occur at concentrations below those causing direct primary irritation (Rosenblatt et al., 1975). In humans, the LCtso (estimated concentration x exposure period lethal to 50% of exposed individuals) for skin exposures is 10,000 mg-min/m (DA, 1974) (for masked personnel however, the amount of body surface area exposed was not reported). The ICt 50 (estimated concentration x exposure period incapacitating to 50% of exposed individuals) for skin exposures is 2000 mg-min/m at 70-80°F in a humid enviromnent and 1000 mg-min/m at 90°F in a dry enviromnent (DA, 1974, 1992). The ICtso for contact with the eyes is 200 mg-min/m (DA, 1974, 1992). The LDl for skin exposure is 64 mg/kg and the LD50 is estimated to be about 100 mg/kg (DA, 1974,1992). 

From a military perspective, it is not necessarily the lethality of a percutaneous threat agent that is of primary concern but its ability to cause incapacitation. On this basis, HD can be considered to be equipotent to VX (the most toxic of nerve agents). In addition, the pathological consequences of HD exposure would likely impose a substantial burden on medical resources. Thus, while HD is not generally considered to be a lethal agent, its vesicant potency combined with its relative persistence and delayed effects contribute to its reputation as king of the war gasses . 

Immediately after exposure, there is eye irritation and coughing, sneezing, salivation and lachrymation rapidly follow. Contamination of the skin causes erythema at concentrations of 0.05-0.01 mg cm-2 (Inns et al., 1990) with vesication after a few hours. Pain in the skin and eyes is immediate, a major point of difference from sulphur mustard. The effects in the eye and skin reach their greatest at 4-8 h post-exposure. The patient is seriously incapacitated, breathing with difficulty and unable to see. In severe cases, pulmonary edema follows and the patient may die of respiratory failure. In cases where skin contamination is extensive, there may be liver necrosis and the absorption of arsenic may be sufficient to cause death. 

Vesicants, such as sulfur mustard (HD) and the arsenical Lewisite (L), cause irritation and vesication of the skin and mucous membranes, notably of the lungs. Mustard exposure to the skin is insidious, causing no immediate discernible effects to the skin for several hours blistering occurs 12 to 24 hours after exposure.25 Although mustard causes few deaths, its vesicating properties are incapacitating, and casualties require 1 to 4 months of hospitalization. Lewisite blisters heal within several weeks. 

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