Simazine is the common name for 2-chloro-4,6-bis(ethylamino)-1,3,5 triazine. The acute oral LD50 estimates are 5,000 mg/kg or higher in rats, mice, rabbits, and birds, but a dose of 500 mg/kg has been reported to be lethal in sheep. Pharmacotoxic signs in sheep included incoordination, tremors, weakness, cyanosis, and clonic convulsions. A dose of 4,200 mg/kg caused anorexia, weight loss, and some lethality in rats. In a three-generation reproduction study with Charles River rats fed simazine 80W in the diet at 50 or 100 ppm, a parental toxicity NOAEL of less than 50 ppm and a LOAEL of 50 ppm were identified based on reduced weight gains in males during the premating periods. In a teratology study with rats, simazine administered at high doses (1,250 and 2,500 mg/kg/day) during gestation days 6 through 15 delayed fetal development and was embryotoxic but not teratogenic. Most tests of mutagenic potential for simazine have been negative.