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

Titanium Dioxide Nanoparticles Increase Sensitivity in the Next Generation of the Water Flea <em>Daphnia magna</em>

<div><p>The nanoparticle industry is expected to become a trillion dollar business in the near future. Therefore, the unintentional introduction of nanoparticles into the environment is increasingly likely. However, currently applied risk-assessment practices require further adaptation to accommodate the intrinsic nature of engineered nanoparticles. Combining a chronic flow-through exposure system with subsequent acute toxicity tests for the standard test organism <em>Daphnia magna</em>, we found that juvenile offspring of adults that were previously exposed to titanium dioxide nanoparticles exhibit a significantly increased sensitivity to titanium dioxide nanoparticles compared with the offspring of unexposed adults, as displayed by lower 96 h-EC₅₀ values. This observation is particularly remarkable because adults exhibited no differences among treatments in terms of typically assessed endpoints, such as sensitivity, number of offspring, or energy reserves. Hence, the present study suggests that ecotoxicological research requires further development to include the assessment of the environmental risks of nanoparticles for the next and hence not directly exposed generation, which is currently not included in standard test protocols.</p> </div

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

The experimental set-up.

<p>The flow-through testing apparatus, showing four experimental units (volume, 500 mL) with five <i>D. magna</i> each. Approximately 40 mL of the test medium was introduced every other hour slightly below the surface of the water. The old test medium was passively discharged using hydrostatic pressure at the bottom of each vessel. A fine mesh screen (0.1 mm) prevented the loss of recently hatched juvenile daphnids.</p

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

The sensitivity of juveniles released by nTiO₂-exposed adults.

<p>The cumulative mean (±95% CIs) difference in sensitivity – in terms of 96 h-EC50 values – of the offspring (fifth brood) released by adults exposed to 0.02 or 2.00 mg nTiO2/L and offspring released by control (uncontaminated) daphnids is displayed using the standardised effect size Cohen’s <i>d</i>. (<i>A</i>) The cumulative effect sizes for all bioassays conducted (n = 7) with the fifth brood during the first and second set of experiments. (<i>B</i>) The cumulative effect sizes for acute toxicity experiments conducted with offspring released in the control medium by adults previously exposed to the above-mentioned nTiO2 concentrations during the second set of experiments (n = 3). The statistical significance of a cumulative effect is highlighted by an asterisk (*). Negative effect sizes indicate increased toxicity.</p

Heavy Metal Uptake and Toxicity in the Presence of Titanium Dioxide Nanoparticles: A Factorial Approach Using <i>Daphnia magna</i>.

Unintentionally released titanium dioxide nanoparticles (nTiO₂) may co-occur in aquatic environments together with other stressors, such as, metal ions. The effects of P25-nTiO₂ on the toxicity and uptake of the elements silver (Ag), arsenic (As) and copper (Cu) were assessed by applying a factorial test design. The test design consisted of two developmental stages of <i>Daphnia magna</i>, two levels of nTiO₂ (0 versus 2 mg/L) as well as seven nominal test concentrations of the respective element. The presence of nTiO₂ increased Ag toxicity for juveniles as indicated by a 40% lower 72-h EC₅₀, while the toxicities of As and Cu were reduced by up to 80%. This reduction was even more pronounced for Cu in the presence of dissolved organic carbon (i.e., seaweed extract) and nTiO₂. This outcome coincides with the body burden of the elements, which was elevated 2-fold for Ag and decreased 14-fold for Cu in the presence of nTiO₂. Although the underlying mechanisms could not be uncovered, the data suggest that the carrier function of nTiO₂ plays a central role. However, to understand the processes and mechanisms occurring in the field due to the presence of nTiO₂ further systematic investigations considering environmental variables and nanoparticle characteristics are required

The sensitivity of juveniles released during the third set of experiments.

<p>96 h- EC₅₀ values with respective 95% CIs of the fifth brood released by adults exposed to 0.00 and 2.00 mg/L P25-nTiO₂ during the third set of experiments, which considered exclusively potential implication of nTiO₂ exposure within the brood pouch. No statistically significant difference among treatments was observed.</p

The sensitivity of juveniles released by adults exposed to different nTiO₂ products.

<p>Sensitivity, displayed as percent relative to the 96 h-EC₅₀ of the respective control, of the fifth brood released by adult <i>D. magna</i> exposed to different nTiO₂ treatments using the products P25 or A-100. The data displayed for P25 represent the weighted mean values of the seven experiments (first and second set of experiments), each with four replicates per treatment, whereas the 96 h-EC₅₀ for the offspring released from the control parents was 3.13 mg/L nTiO₂. For the product A-100, the results of one experiment with four replicates of pre-treatment are displayed (fourth set of experiments). In this situation, the 96 h-EC₅₀ for the offspring released from the control parents was 1.98 mg/L nTiO₂. The error bars and dashed lines indicate the standard error. The dashed lines are related to the control. Asterisks (*) denote significant differences between a treatment and the respective control.</p

Scanning electron microscope image.

<p>An image of the size-homogenised, stable nTiO₂ suspension of the product P25 taken by an scanning electron microscope using 100,000-fold magnification (Hitachi SU8030).</p