Importance of considering pesticide stereoisomerism––proposal of a scheme to apply Directive 91/414/EEC framework to pesticide active substances manufactured as isomeric mixtures

An important gap has been detected in the application of the European framework for the evaluation of pesticide active substances constituted by enantiomeric and other kind of stereoisomeric mixtures. Up to date, little attention has been paid to the different biological properties of these compounds. Considering efficacy, toxicity, environmental fate and behaviour and ecotoxicity of separated isomers is necessary to fulfil Directive 91/414/EEC objectives of health and environment protection. Here, a critical review of this question for pesticide active substances is presented. An evaluative scheme for considering this question in the framework of Directive 91/414/EEC is also proposed.