In the European Union environmental risk assessment for plant protection products in aquatic ecosystems follows a tiered approach that is specified by EFSA in the aquatic guidance document (AGD). With its entry into force in 2015 a revised version of the AGD defined several regulatory changes, e.g. for higher tier risk assessment.
In higher tier risk assessment the regulatory acceptable concentration (RAC) may be based on data from aquatic (semi-)field studies (micro-/mesocosms). For this purpose the AGD requires that it should be verified whether the effects observed in the study occurred during a realistic exposure to the substance of concern. The measured dissipation of the test substance applied in the study has to be compared with modelled exposure profiles (i.e. the course of a predicted environmental concentration as a function of time) to decide if the dissipation was realistic to worst case.
Figure 1: Measured dissipation of the test substance (black, here normalised to the peak of the exposure profile) in a field study compared to a modelled exposure profile (red)
The RAC may subsequently be derived by applying either the ecological threshold option (ETO), accepting negligible population effects only, or the ecological recovery option (ERO), accepting initial population-level effects if recovery is demonstrated within 8 weeks after the first application. To upgrade a provisional to an official ERO-RAC using the ecological recovery option the AGD requires that periods of an exposure profile exceeding the ETO-RAC but not the ERO-RAC are evaluated.
Figure 2: Modelled exposure profile (red) with exposure periods (shaded blue) exceeding ETO-RAC (black) but not ERO-RAC (blue)
Both, evaluating test substance dissipation in the (semi-)field study and upgrading the ERO-RAC require a comparison of study results to modelled exposure profiles. For these analyses several approaches are possible, however, there is no standardised scientific or regulatory accepted guidance available yet. In this project the AGD requirements are exemplarily applied to a representative dataset of substances and different approaches for the analysis of exposure profiles are evaluated in order to develop a practicable method that is suitable for regulatory practice in EU risk assessment.
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Publications:
- Ernst, J., Petschick, L., Nickel, J.P., Bereswill, R., Meller, M. & R. Debus (2015) Exposure profiles in aquatic mesocosm risk assessment. Poster, 20th annual meeting of SETAC GLB (Society of Environmental Toxicology and Chemistry - German Language Branch), Zürich, 7 – 10 September 2015.
- Ernst, J. (2015) Assessment of pesticide effects based on time-variable exposure in aquatic ecosystems. Master Thesis, University of Applied Sciences RheinMain.
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