3 research outputs found
Aquatic Exposure Predictions of Insecticide Field Concentrations Using a Multimedia Mass-Balance Model
Highly
complex process-driven mechanistic fate and transport models
and multimedia mass balance models can be used for the exposure prediction
of pesticides in different environmental compartments. Generally,
both types of models differ in spatial and temporal resolution. Process-driven
mechanistic fate models are very complex, and calculations are time-intensive.
This type of model is currently used within the European regulatory
pesticide registration (FOCUS). Multimedia mass-balance models require
fewer input parameters to calculate concentration ranges and the partitioning
between different environmental media. In this study, we used the
fugacity-based small-region model (SRM) to calculate predicted environmental
concentrations (PEC) for 466 cases of insecticide field concentrations
measured in European surface waters. We were able to show that the
PECs of the multimedia model are more protective in comparison to
FOCUS. In addition, our results show that the multimedia model results
have a higher predictive power to simulate varying field concentrations
at a higher level of field relevance. The adaptation of the model
scenario to actual field conditions suggests that the performance
of the SRM increases when worst-case conditions are replaced by real
field data. Therefore, this study shows that a less complex modeling
approach than that used in the regulatory risk assessment exhibits
a higher level of protectiveness and predictiveness and that there
is a need to develop and evaluate new ecologically relevant scenarios
in the context of pesticide exposure modeling
Fungicide Field Concentrations Exceed FOCUS Surface Water Predictions: Urgent Need of Model Improvement
FOCUS
models are used in European regulatory risk assessment to
predict the frequency and magnitude of individual pesticide surface
water concentrations. A recent study showed that these models are
not protective in the prediction of insecticide concentrations in
surface waters and sediments. Since fungicides differ with regard
to their physicochemical properties, application patterns, and entry
routes, we compared a larger data set of 417 measured field concentrations
(MFC) of agricultural fungicides in surface waters and sediments from
56 studies to the respective predicted environmental concentrations
(PEC) calculated with FOCUS step 1–4. Although the fraction
of the underestimation of fungicide MFC values was generally lower
than that obtained for insecticides, 12% of step 3 and 23% of step
4 PECs were exceeded by surface water MFCs. Taking only the 90th percentile
concentration of every substance and only E.U. studies into account
(E.U. studies: <i>n</i> = 327; 90th percentile + E.U. studies: <i>n</i> = 136), a maximum of 25% of the step 3 and 43% of the
step 4 PECs were exceeded by surface water MFCs, which is an even
worse outcome than that obtained for insecticides. Our results demonstrate
that FOCUS predictions are neither protective nor appropriate for
predicting fungicide concentrations in the field in the context of
European pesticide risk assessment
Regulatory FOCUS Surface Water Models Fail to Predict Insecticide Concentrations in the Field
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