In March 1991, during the cease-fire period, troops from the U.S. The health effects of low levels of sarin exposure are of most interest to Gulf War veterans because of their possible exposure from demolition of Iraqi munitions at Khamisiyah, Iraq (see discussion below). Finally, low-level exposure may have occurred even though there are no immediately detectable cholinergic signs and symptoms (Brown and Brix, 1998). An intermediate-level exposure is presumed to have occurred when the acute cholinergic effect is limited to miosis (contraction of the pupil), rhinorrhea (an extreme type of runny nose), and depressed cholinesterase levels in the blood. A high level of sarin exposure of humans (after single or multiple exposures) is presumed to have occurred when the acute cholinergic syndrome is manifest. Because the actual doses to humans under battlefield or terrorist circumstances cannot be measured or are difficult to reconstruct, they can be inferred on the basis of their acute clinical effects. The acute health effects of sarin are exquisitely dependent on dose. The binding of sarin to AChE is irreversible, whereas the binding of PB is reversible.
Both PB and sarin exert their effects by binding to and inactivating the enzyme acetylcholinesterase (AChE). The drug pyridostigmine bromide (PB) is pharmacologically similar to sarin and other organophosphates, but it is a member of a different chemical class, the carbamates (see Chapter 6). A few highly toxic members of this large class are chemical warfare agents, but most are insecticides ( Table 5.1) (Lotti, 2000). There are about 200 distinct organophosphate insecticides marketed today in thousands of formulations (Klaassen et al., 1996). Sarin is a member of a class of chemicals known as organophosphorus esters (or organophosphates).
Because of its extreme potency, sarin is lethal to 50 percent of exposed individuals at doses of 100 to 500 mg across the skin, or 50–100 mg/min/m 3 by inhalation (in an individual weighing about 70 kg) (Somani, 1992). In vapor or liquid form, sarin can be inhaled or absorbed, respectively, across the skin, eyes, or mucous membranes (Stewart and Sullivan, 1992). Sarin's first military use did not occur until the Iran–Iraq conflict in the 1980s (Brown and Brix, 1998).Įxposure to sarin can be fatal within minutes to hours. Although its battlefield potential was soon recognized, Germany refrained during World War II from using its stockpiles. It was synthesized in 1937 in Germany in a quest for improved insecticides (Somani, 1992). Sarin is a highly toxic nerve agent produced for chemical warfare.
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