The toxicity of diquat

Clark, D. G. and Hurst, E. W. (1970).Brit. J. industr. Med.,27, 51-55. The toxicity of diquat. The acute toxicity of diquat has been assessed in several species. The oral LD₅₀ ranged from about 30 mg/kg in cattle to 231 mg/kg in the rat. Large doses of diquat gave rise to symptoms indicative of an action on the central nervous system, but smaller doses did not suggest an obvious mode of action to account for the deaths, which were sometimes delayed for up to 14 days. The 24-hour percutaneous LD₅₀ in the rabbit was greater than 400 mg/kg. This dose did not irritate the skin. A drop of a 20% aqueous solution of diquat in the conjunctival sac of the rabbit eye caused only slight irritation. The chronic administration of diquat dichloride in the diet for several months led to bilateral cataract in the rat and the dog. A concentration of 0·05% in the rat diet caused bilateral opacities in all rats within 12 months, but 0·001% diquat did not cause any opacities in two years. Bilateral opacities of the lenses of all dogs occurred within 12 months of administration of 15 mg/kg/day, but 1·7 mg/kg/day was without effect after four years.