A Hazard Quotient approach for assessing the risk to non-target arthropodsfrom 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/Co E Arthropod Natural Enemies Risk Assessment Scheme for guidance on how to c onduct risk assessments for terrestrial non-target arthropods. This scheme is currently in the process of being revised by EPPO/CoE. A major change wi ll be the recommendation for the generation and use of 'Dose Response' toxi city 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 Quot ient (HQ; = Ratio Application Rate/LC50 on Glass)), comparable to the succe ssful approach adopted in the EPPO/CoE 'Honeybee Risk Assessment Scheme'. H owever, 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 recom mended sensitive indicator species (T: pyri and Aphidius) for a wide range of products and validating opposite robust semi-field/held data. This valid ation 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 t o trigger higher-tier risk assessment and/or higher-tier testing for non-ta rget 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 assump tions used in this HQ validation analysis, no further uncertainty factors n eed to be applied for in-crop risk assessment. Whilst a small amount of unc ertainty exists regarding the comparative sensitivity of T. pyri and Aphidi us spp. for off-crop non-target arthropod guilds of arthropods, this is bal anced by the fact that the off-crop exposure assessment used in the HQ deri vation, is at least an order of magnitude higher than that realistically li kely in the field. This HQ approach and trigger value is an appropriate and conservative tool for tier 1 risk assessment, which should reduce the numb er of false positive results leading to unnecessary higher-tier testing.