Lewisite acute lethality

The vesicant properties of lewisite result from direct contact with the skin. Signs of dermal toxicity (pain, inflammation) may be experienced within a minute after exposure. Acute lethality is usually the result of pulmonary injury. Ocular exposure may result in corneal necrosis. Due to its lipophilicity, percutaneous absorption of lewisite is rapid and, at a sufficient exposure, may be associated with systemic toxicity characterized by pulmonary edema, diarrhea, agitation, weakness, hypothermia, and hypotension (lOM, 1993). The threshold for severe systemic toxicity in humans following dermal exposure to lewisite has been estimated at lOmg/kg (9.1-13.4 mg/kg) (Sollman, 1957). 

Acute oral toxicity values for lewisite have been summarized by Watson and Griffin (1992). The only available oral LD50 is that for the rat (50 mg/kg). Lethality values for other routes of exposure indicate some species variability but the values differ by less than an order of magnimde for any particular exposure route. 

Acute toxicity figures for man are not known but a lowest lethal concentration over 30 min of 6 ppm was quoted by Maynard (1989). The LD50 has been measured in a number of species (Table 3), while LCfsoS in a variety of species vary from 500 to 1500 mg min m 3 (Goldman and Dacre, 1989). The efficacy of lewisite, like that of mustard, depends partly upon its vesicant properties but lewisite is also a lethal systemic chemical weapon. About 30 drops (2.6 g), applied to the skin and not washed off or otherwise decontaminated would be expected to produce a fatal outcome in an average man. 

Lewisite is a lethal vesicant and systemic poison. The acute toxicology of lewisite has been reviewed by Goldman and Dacre (1989), Watson and Griffin (1992), and Trammell (1992) and, therefore, is only briefly discussed here. 

Acute Toxicity. Liquid lewisite applied by eye-dropper to the forearms of men caused blanching and discoloration of the skin followed by extensive erythema within 15-30 min and vesication within 12 hr (Wardell 1941 as cited in Goldman and Dacre 1989). The pain associated with these dermal exposures reportedly occurred within 2 min, and considerable discomfort persisted for about 1 wk. Other tests with human subjects and clinical reports also indicate a similar temporal sequence of events. Exposure to lewisite vapor (0.06-0.33 mg/ L) caused discoloration and blistering, with the maximum effect occurring by 36 8 hr after exposure (Wardell 1941). At a concentration of 0.01 mg/L, lewisite vapor caused inflammation of the eyes and swelling of the eyelids after 15 min of exposure, and inhalation of 0.5 mg/L for 5 min is considered to be potentially lethal. 

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