Regulatory FOCUS Surface Water Models Fail to Predict Insecticide Concentrations in the Field

Abstract

The FOrum for the Co-ordination of pesticide fate models and their USe (FOCUS) exposure models are used to predict the frequency and magnitude of pesticide surface water concentrations within the European regulatory risk assessment. The predictions are based on realistic worst-case assumptions that result in predicted environmental concentrations (PEC). Here, we compared for the first time a larger data set of 122 measured field concentrations (MFC) of agricultural insecticides extracted from 22 field studies to respective PECs by using FOCUS steps 1-4. While FOCUS step 1 and 2 PECs generally overpredicted the MFCs, 23% of step 3 and 31% of step 4 standard PECs were exceeded by surface water MFCs, which questions the protectiveness of the FOCUS exposure assessment. Using realistic input parameters, step 3 simulations underpredicted MFCs in surface water and sediment by 43% and 78%, respectively, which indicate that a higher degree of realism even reduces the protectiveness of model results. The ratios between PEC and MFC in surface water were significantly lower for pyrethroids than for organophosphorus or organochlorine insecticides, which suggests that the FOCUS predictions are less protective for hydrophobic insecticides. In conclusion, the FOCUS modeling approach is not protective for insecticide concentrations in the field.

Agricultural insecticides threaten surface waters at the global scale

“…However, a recent study (18) showed that the FOCUS model, used for the regulatory exposure assessment in the European Union, underpredicts field concentrations of newer, increasingly used insecticides such as hydrophobic pyrethroids. Specifically, the ratio of the predicted insecticide surface water concentrations to the MIC SW was significantly lower for pyrethroids than for organochlorines and organophosphorus insecticides.…”

“…Targeted postregistration monitoring schemes and regulatory actions are needed, considering that 18 and 24 of the 28 insecticide compounds included in our metaanalysis are currently approved in EU countries and in the United States, respectively. The high numbers of threshold exceedances worldwide are caused by failures of either regulatory exposure assessment (18) or farmers' adherence to prescribed risk management obligations (35).…”

“…The few large-scale studies of insecticide exposure in surface waters have either examined sites in spatially restricted areas (10,17,18); lacked a quantitative data analysis (4); or followed other, rather specific objectives (18,19) (SI Appendix, SI Discussion). However, the results obtained in these studies suggest that exceedances of threshold values occur, particularly for insecticides.…”

Road to regulation of endocrine disruptors and combination effects

“…Exposure models used in RA for predicting concentrations of PPPs in surface waters, for instance, are demonstrated being unreliable for realistic situations (Bach and Hollis, 2012, Knäbel et al, 2012. The application of assessment factors is not sufficient for considering realistic combination effects (Martin et al, 2013).…”

Environmental risk assessment of pesticides in Ethiopia : a case of surface water systems

“…If relevant input parameters may not be correctly estimated or cannot be verified comparing model output (and certainly output from a suite of coupled models), to field measurements raises concerns about its usefulness and validity, especially if contributions from non-modelled point sources cannot be excluded for the field measurements. In addition, if populations of simulations and field measurements are compared, it is crucial to demonstrate that the compared populations of simulations and field measurements represent similar environmental conditions and that for each comparison the application regimes are identical (Knäbel et al, 2012 and two ensuing rebuttals: Bach and Hollis, 2013;Reichenberger, 2013).…”