Agent GA Tabun

Agent GA (tabun) is an organophosphate ChE inhibitor similar to other nerve agents in mode of action and toxic effects, and it is toxic by all possible exposure routes ingestion, inhalation, and ocular and percutaneous absorption (DA 1974). By the inhalation exposure route, GA is only half as toxic as GB however, at low concentrations it has a greater effect on the eyes (DA 1974). The acute toxicity of GA and other nerve agents has been reviewed in several earlier reports (Carnes and Watson 1989 Dacre 1984 Munro et al. 1994 Sidell 1992  

1 Intravenous Estimated no-effect level for RBC-ChE inhibition McNamara et al. (1973) 

Somani et al. 1992 Watson et al. 1989b). This review focuses primarily on the available subchronic or chronic toxicity data that may be useful for deriving an oral RfDg. 

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Final Recommendations for Protecting Human Health From Potential Adverse Effects of Exposure to Agents GA (Tabun), GB (Sarin), and VX." Federal Register 68, No. 196 (October 9, 2003) 58348-58351. 

There are seven sites in the United States where U.S. Unitary Chemical Stockpile exists. Below they are listed by chemical weapon as follows GB, sarin H, mustard HD, mustard HT, mustard VX, persistent nerve agent GA, tabun L, lewisite TGA, thickened tabun TGB, thickened sarin. 

Kawakami TG, Goldman M, Rosenblatt L, Wilson BW. Toxicity Studies in Agent GA Mutagenicity of Agent GA (Tabun) in the Mouse Lymphoma Assay. Davis, Calif University of California Davis Laboratory for Energy 1989. 

Nerve agents GA (tabun), GB (sarin), GD (soman), and VX are manufactured compounds. The G-type agents are clear, colorless, tasteless liquids miscible in water and most organic solvents. GB is odorless and is the most volatile nerve agent. GA has a slightly fruity odor, and GD has a slight camphor-1 ike odor. VX is a clear, amber-colored odorless, oily liquid. It is miscible with water and dissolves in all solvents. VX is the least volatile neive agent. 

The Ml8 detection kit, like the M256A1 kit, is a military item. In fact it might be termed a chemical weapons Draeger tube kit—a colorimetric device for measuring the concentration of selected airborne chemicals. The Ml 8 comes with disposable tubes for cyanide, phosgene. Lewisite, sulfur mustard, and nerve agents GA (tabun), GB (sarin), GD (soman), and VX. Tests for each take only 2 to 3 minutes but must be conducted serially. 

Organic arsenical L (lewisite) Nerve agents GA (tabun)... 

Agent GA (tabun ethyl dimethylamidocyanophosphate CAS no. 77-81-6) is a colorless to brown liquid with a molecular weight of 162.1 (DA 1974 MacNaughton and Brewer 1994). Its chemical structure is... 

Agent GA (Tabun). RfDe = 4 x 10 mg kg d" . A NOAEL was identified in a 90-d study in rats. A total uncertainty factor of 3000 was applied to account for protection of sensitive subpopulations (10), animal-to-human extrapolation (10), extrapolation from a subchronic to chronic exposure (3), and incomplete data base (3). An uncertainty factor of 3 was used to extrapolate from a subchronic to chronic exposure because of the unlikelihood that the LOAEL would have been substantially lower if the exposure had been chronic. A LOAEL-to-NOAEL uncertainty factor was not needed because a NOAEL was used in the derivation. The data base for GA lacks a multigeneration reproductive toxicity study, but because the available evidence indicates that organophosphate cholinesterase inhibitors such as GA are not likely to be reproductive toxins, the missing study was not considered critical. Therefore, a UFd of 3, not the default value of 10, was applied. A Modifying Factor of 3 was applied because the key study involved a nonoral exposure route (intraperitoneal injections). 

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