ABSTRACT
Herbacides are also pesticides; they are usually chemically and toxico-logically quite different from insecticides and are not included in this review. Livestock do not usually have direct contact with these agents, so exposure is rare. The insecticide classes which replaced the chlorinated hydrocarbons for use on and around livestock in Canada were the pyrethrins, organo-phosphates and carbamates. For chemicals to become residues in animal products they must be taken in by the animal more rapidly than they are removed. Also, the animal product must be made available for human consumption before the chemical has had time to leave the animal’s system or before the chemical has been destroyed in the product during processing. A survey of the literature on the frequency of pesticide residues in human food of animal origin suggests that the incidence is quite low in some countries and quite high in others.
