Acute dermal toxicity of two quarternary organophosphonium salts in the rabbit

Tetrabutyl phosphonium chloride and tetrabutyl phosphonium bromide were evaluated for their potential to cause primary dermal irritation and acute dermal toxicity in rabbits. Both chemicals were found to not only be severely irritating to skin, but the pure hygroscopic chemicals caused death in more than half the number of rabbits used in the primary dermal irritation tests. Further investigations revealed the single-application dermal LD50 of tetrabutyl phosphonium chloride (Bu4PCl) (using an ethylene carbonate (EC) vehicle) was 600 mg/kg for male rabbits and 500 mg/kg for female rabbits. The single-application dermal LD50 of tetrabutyl phosphonium bromide (Bu4PBr) (using the EC vehicle) was 700 mg/kg for male rabbits and 850 mg/kg for female rabbits. The dermal LD50 of pure undiluted Bu4PCl was 225 mg/kg for male rabbits. These data indicate that Bu4PCl and Bu4PBr represent a substantial acute dermal toxicity hazard.