A Hazard Quotient approach for assessing the risk to non-target arthropods from plant protection products under 91/414/EEC : hazard quotient trigger value proposal and validation

The EU Plant Protection Product Directive 91/414/EEC recommends the EPPO/CoE Arthropod Natural Enemies Risk Assessment Scheme for guidance on how to conduct risk assessments for terrestrial non-target arthropods. This scheme is currently in the process of being revised by EPPO/CoE. A major change will be the recommendation for the generation and use of `Dose Response' toxicity data instead of limit test data. In addition, the revised EPPO/CoE Non-target Arthropods Risk Assessment Scheme will replace the current arbitrary 30 % threshold trigger value applied to limit test data, with a Hazard Quotient (HQ; = Ratio Application Rate/LC50 on Glass)), comparable to the successful approach adopted in the EPPO/CoE `Honeybee Risk Assessment Scheme'. However, in order for this new approach to be implemented under 91/414/EEC, an appropriate regulatory HQ trigger value needs to be derived. Such an HQ trigger value has been established by calculating HQ values for the 2 recommended sensitive indicator species (T. pyri and Aphidius) for a wide range of products and validating opposite robust semi-field/field data. This validation indicated that an HQ trigger value of greater than or equal to 12 for T. pyri and greater than or equal to 8 for Aphidius spp., should be used to trigger higher-tier risk assessment and/or higher-tier testing for non-target arthropods. As these trigger values were validated with realistic semi-field/field data they apply for both lethal and sub-lethal effects as well as single and multiple application scenarios. Due to the worst case assumptions used in this HQ validation analysis, no further uncertainty factors need to be applied for in-crop risk assessment. Whilst a small amount of uncertainty exists regarding the comparative sensitivity of T. pyri and Aphidius spp. for off-crop non-target arthropod guilds of arthropods, this is balanced by the fact that the off-crop exposure assessment used in the HQ derivation, is at least an order of magnitude higher than that realistically likely in the field. This HQ approach and trigger value is an appropriate and conservative tool for tier 1 risk assessment, which should reduce the number of false positive results leading to unnecessary higher-tier testing.