Environmental Risk Assessment for Veterinary Medicinal Products Part 3. Validation of environmental exposure models

This report investigates the validity of exposure and distribution models for soil, groundwater and surface water for the environmental risk assessment (ERA) of veterinary medicinal products (VMPs) at registration. The functional validations with (oxy)tetracycline and sulphonamides indicate that it is impossible to analyse the contribution of every single model parameter to the variability in the model predictions using random field samples. It can be concluded that the available field data do not allow for validation of the parameter selection in the models investigated.A lysimeter study with sulphachloropyridazine was used for a functional validition of the groundwater model PEARL. A simulation error of 0.02 was established, which means that computed values underestimated the measured values by a factor 50. In this study two major factors for uncertainty in the simulation are discerned. First, the untimely ending of the lysimeter hampered the full expression of downward transport. Second, the uncertainty in the sorption process and parameter is of major importance for a reliable simulation. Despite the shortcomings of the case study the potential of pesticide leaching models in general and of PEARL in particular is demonstrated