Can you reduce validation effort when jointly calibrating guts models for multiple species?
In regulatory risk assessment of Plant Protection Products, an option for endpoint refinement using effect modelling has been included in guidance documents since 2013 (Tier IIC; EFSA Aquatic Guidance 2013). A detailed description on the type of models that are fit for the regulatory process, their application, and underlying data requirements were outlined and discussed in detail in the EFSA Opinion on TKTD modelling (2018). For lethal effects there is a clear recommendation for the parameterization of the (reduced) GUTS model. Although PPP Notifiers are often very interested in the modelling approaches, in our experience, many are hesitant to ultimately choose an effect modelling approach to address their regulatory questions. This is mainly due to the uncertainty surrounding regulatory acceptance and the high costs associated with calibration and validation experiments, particularly if a large number of species are involved. Often, existing data sets from previous submissions do not include the necessary information to be re-used for model parameterization. The lack of information in some studies may be circumvented by calibrating GUTS jointly using multiple species data sets if parameters correlate. Here, we propose conducting a reduced number of non-standard higher tier experiments, for a set of key species to validate the multi-species GUTS parametrization. We highlight where the uncertainties of this approach within a risk assessment lie, as well as the potential advantages and knowledge gains.
The poster is available for free download.