GA (Tabun) is chemically known as ethyl N,N-dimethylphosphoroamidocyanidate. It is the first of the nerve agents. It was developed by the Germans prior to World War II. GA is a fast acting lethal nerve agent. It is approximately 30 times as toxic as phosgene, and about 20 times as persistent as GB. It is primarily a respiratory hazard, but it is also highly toxic upon exposure to the eyes, skin and digestive tract. The toxicity is much greater through the eyes than through the skin.