Toxicity studies with 5-bromo-3- sec-butyl-6-methyluracil

Abstract

The herbicide, 5-bromo-3- sec-butyl-6-methyluracil (bromacil) exhibited a low order of acute toxicity as evaluated by oral, dermal, and inhalation studies in mammals and by fish and wildlife studies. Bromacil fed to pregnant New Zealand white rabbits on days 8–16 of gestation at dietary levels of 0, 50, and 250 ppm was not teratogenic. In a three-generation six-litter reproduction study with rats, a dietary level of 250 ppm had no adverse effects upon reproduction and lactation performance; no pathologic changes were observed in weanling pups of the F 3b generation. Rats of both sexes were fed nutritionally complete diets containing 0, 50, 250, and 1250 ppm bromacil for 2 yr. Except for a lower rate of weight gain, a slightly decreased food intake and a slightly lower food efficiency among the female rats that received 1250 ppm bromacil, there was no nutritional, clinical, hematologic, urinary, or biochemical evidence of toxicity, nor any evidence of carcinogenicity; there was, however, a suggestion of slight hyperplasia in the thyroids of animals given the highest dietary level. Beagle dogs of both sexes, 1–2 yr of age, fed nutritionally complete diets containing 0, 50, 250, and 1250 ppm bromacil for 2 yr, showed no nutritional, clinical, hematological, urinary, biochemical, or pathologic evidence of toxicity.