Toxicological significance of pesticide conjugates

Abstract

Products formed by the reaction of pesticides and their metabolites with endogenous chemicals (glucose, glucuronic acid, sulfate, glutathione, amino acid, etc.) are referred to as pesticide conjugates. Evidence to date suggests that this is a detoxification process since the resulting products are polar and usually rapidly eliminated from the body. However, very little is known about their acute toxicity, and almost nothing concerning the effects of chronic dietary exposure of animals to these materials. Though conjugates may be formed in vivo by animals administered the parent pesticide, this hardly can be considered an adequate means of assessing their toxic properties. Pesticide metabolites formed by primary metabolic reactions are often evaluated individually in both acute and subchronic toxicity tests, but similar experiments are not conducted with conjugates. To assume that pesticide conjugates are toxicologically insignificant is unsound scientifically, although the rationale for such an assumption is not completely without merit. Many polar compounds are inactive but many, including some conjugates, are biologically active and indeed may be very toxic. While elaborate toxicological investigations of all pesticide conjugates do not appear warranted, there is a clear need to strengthen the data base relative to their potential toxicological significance. Extensive investigations of selected model compounds, representing different pesticide groups and conjugate types, are in order if the issue is to be placed in proper perspective relative to the total safety evaluation of pesticidal chemicals.