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Acute and Environmental Toxicity Studies with Hexazinone
Haskell Laboratory for Toxicology and Industrial Medicine, E. I. du Pont de Nemours and Company, Inc. Wilmington, Delaware 19898
Acute and Environmental Studies with Hexazinone. KENNEDY, G. L, JR. (1984). Fundam. Appl. Toxicol. 4, 603–611. The acute toxicity of hexazinone, a herbicide intended for general noncropland areas and selected crop uses (alfalfa and sugarcane), has been evaluated to establish proper handling guidelines and to measure its potential impact on the environment The material is slightly to moderately toxic when given as a single oral dose; its LD50 in male rats is 1690 mg/kg, in male guinea pigs 860 mg/kg, and in male dogs greater than 3400 mg/kg although in the dog emesis prevented accurate quantitation. When the material is administered intraperitoneally, the LD50 in rats is 530 mg/kg. Repeated doses (five oral doses per week for 2 weeks) of 300 mg/kg to rats produced slight weight loss in one of two replicate experiments. In both studies, no gross or histologjc alterations were apparent Hexazinone is a moderate to severe eye irritant in the rabbit and produced only mild erythema in rabbit skin at 5278 mg/kg, a dose which did not produce lethality or other clinical signs. Subchronic dermal exposures (10 consecutive doses) to rabbits produced increases in serum alkaline phosphatase and glutamic-pyruvic transaminase at the highest levels tested (680 and 770 mg/kg in two separate experiments) with no effects seen at 150 mg/kg. There were no alterations in livers from treated rabbits examined by light microscopy. No dermal sensitization was produced when concentrations of up to 50% were tested in guinea pigs. One-hour inhalation exposure of up to 7.48 mg/liter did not produce mortality in rats. In freshwater biota, the material had slight to low toxicity with 96-hr LC50 values being between 370 and 420 mg/liter in bluegill sunfish, between 320 and 420 mg/liter in rainbow trout, and 274 mg/liter in fathead minnows. The 48-hr LC50 in Daphnia magna was 152 ppm. In marine biota, similar low toxicity was indicated by a 48-hr EC50 of 320 to 540 ppm in eastern oysters, a 96-hr LC50 of 56 to 100 ppm in grass shrimp, and a 96-hr LC50 greater than 1000 ppm in fiddler crabs. Bobwhite quail were not killed by feeding of up to 10,000 ppm. When given to quail as a single oral dose by intubation, the LD50 value was 2258 mg/kg. Ducks survived feeding of 10,000 ppm indicating that the material has a low order of toxicity in water fowl and upland game birds. Hexazinone had a low order of acute toxicity when tested in mammals, freshwater and marine biota, and birds. The material is an eye irritant and should be handled carefully. Dermal irritancy, sensitization potential, and systemic toxicity are low.