Significance of impurities in the safety evaluation of crop protection
products (IUPAC Technical Report)
A. Ambrus*, D.
J. Hamilton, H. A. Kuiper, and K. D. Racke
Abstract: There may be substantial differences in the chemical
composition of technical-grade products of the same active ingredient
manufactured under different conditions, from different raw materials,
or by different routes of synthesis. Resulting differences in impurity
content may significantly affect the toxicological properties of pesticide
products. Relevant impurities are those that may exhibit pronounced
toxic effects compared to the active ingredient, affect phytotoxicity
or physical properties of formulations, result in undesirable residues
in food,or cause environmental contamination. The first safety assessment
of an active ingredient by a regulatory body considers toxicological
data developed on a representative batch of technical products, with
the assumption that the material produced commercially by the original
or generic manufacturers has an equal or higher content of active ingredient
and contains the same or fewer impurities at equal or lower concentrations
as the fully characterized technical product used in the toxicological
tests. Three steps are essential for ensuring the safety of commercial
technical- grade pesticide products, whether produced by the original
manufacturer or by generic manufacturers. First, the identity and chemical
structure of the impurities must be elucidated.This should include positive
identification of major (=1 %) and all toxicologically or environmentally
relevant impurities, and characterization of minor impurities (>0.1
%). Second, in addition to recognition of a minimum active ingredient
content, official specifications should also list relevant impurities
and their maximum permissible concentrations.Implementation of these
specifications should be aided by a decision-making scheme for establishing
similarity of subsequently evaluated technical products. Third, appropriate
analytical methods for the detection and quantification of impurity
levels should be developed and employed in a quality-monitoring program
associated with the manufacturing and formulation process.
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*Corresponding Author
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