Bioavailability of Common Conjugates and Bound Residues

Michael W. Skidmore, Jill P. Benner, Cathy Chung Chun Lam, James D. Booth, Terry Clark, AlexJ. Cledhill, Karen J. Roberts 

Before any pesticide can be authorized for use, its human and environmental safety have to be considered through risk assessment i.e., a comparison of hazard and exposure. A key element in the risk assessment process is the determination of the residue definition, i.e., the components of the residue resulting from the use of the pesticide that are considered to be relevant. Residues remaining on items for food and feed are identified in metabolism studies, in which the pesticide is radiolabeled to enable its fate and behavior to be followed. The metabolic pathways can be extremely complex but can be grouped into four distinct categories or phases [1], 

Phase I metabolism mostly involves oxidation, reduction, and hydrolytic reactions introducing functional groups into the xenobiotic compound. These residues are generally extractable and can be readily characterized/identified and their relevance assessed, based on their concentration, toxicity or by structure-activity relationships. 

Phase IV residues result from the incorporation of the radiolabel from the pesticide into naturally occurring compounds, e.g., proteins and sugars. These residues are of no toxicological concern. 

The focus of the current project is on the bioavailability of specific Phase II and Phase III metabolites, derived from plants. The objective of the project is  

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