Pure Appl. Chem.,
Vol. 70, No. 7, pp.1423-1447, 1998
CHEMISTRY AND THE
COMMISSION ON AGROCHEMICALS AND THE ENVIRONMENT
IUPAC Reports on Pesticides( 40 )
Bound Xenobiotic Residues in Food Commodities
of Plant and Animal Origin.
M. W. Skidmore, G. D. Paulson, H.
A. Kuiper, B. Ohlin and S.
Synopsis : In order to assess the dietary risk resulting from the
use of pesticides or veterinary drugs the nature of the chemical residues
on food commodities needs to be determined. Elucidation of the nature of the
chemical residue is carried out using radiolabelled studies where the radiolabelled
xenobiotic is applied or dosed in a manner which reflects use conditions.
Food commodities are exhaustively extracted to remove the individual components
of the residue. Once extracted the identity and toxicological significance
of the components can be assessed and, where appropriate, analytical methods
developed to quantitatively determine the amount of the components in food
Depending on the characteristics of the components of the residue, the extraction
regime may not remove all the chemical residue from the sample matrix. These
residues are frequently characterised as being "bound", however
the amount and nature of this residue will be highly dependant on the extraction
regime used. To provide guidance and standardisation a definition of the term
"bound residues" is recommended. This definition builds on a previous
IUPAC definition but takes account of the current availability of enzyme systems
which effectively solubilise the entire matrix rather than extracting the
residue. It is also recommended that where the extraction falls short of the
full definition then the residues should be termed as "unextractable"
and the conditions of the extraction should also be defined .
Where residues are bound the assessment of the dietary risk cannot be directly
assessed thus raising issues relating to the significance of the bound residue.
The overall toxicological significance of a bound residue will depend primarily
on its bioavailability and the level of exposure. In order to determine the
bioavailability, study design is crucial in order to perform a critical safety
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