TOXICOLOGICAL IMPLICATIONS OF THE METABOLISM OF BENOMYL IN ANIMALS

Benomyl, methyl 1-(butylcarbamoyl)-benzimidazol-2-yl carbamate, is a f ungicide registered for application on many agricultural and ornamenta l crops. It is also used as a pasture dressing for the control of fung i responsible for facial eczema in sheep and cattle. Its fungicidal pr operty is attributed to its ability to interfere with mitosis, specifi cally by binding to tubulin, and preventing tubulin polymerization. Me tabolic studies have shown that benomyl is hydrolyzed and hydroxylated to different metabolites in mice, rabbits and sheep, and the hydroxyl ated. metabolites are excreted from all species as glucuronide and sul fate conjugates. Benomyl and one of its major degradation products met hyl benzimidazol-2-yl-carbamate (MBC) have low mammalian toxicity prob ably due to their rapid degradation and elimination, and low affinity for mammalian tubulin. Benomyl is a neurotoxic as well as hepatotoxic agent. In addition, it is a teratogenic, mutagenic and carcinogenic co mpound.