Alexandra Kroll

Protecting aquatic ecosystems from pesticide pollution is a critical regulatory task. Benthic diatoms, being part of aquatic biofilms, are commonly used to indicate nutrient pollution. However, their potential as bioindicators for pesticides and other co-occurring environmental stressors remains poorly assessed. To address this, we conducted a flow-through chamber experiment designed to reflect realistic field exposure scenarios. We exposed biofilms to 44 treatments combining environmentally relevant pesticide mixtures including herbicides, fungicides, insecticides (44 levels of measured Toxic Units (TU_mix) ranging from 2 × 10^-5 to 4), in combination with three environmental stressors (light intensity, temperature, nutrient levels) over a 25-day period. Upon termination, we examined the diatom community composition using Next-Generation Sequencing along with community-level biofilm descriptors (β-diversity, effective photosynthetic activity, chlorophyll-a content, ash-free dry weight, bacterial abundance). While we did not find any significant responses to pesticides at the community level, we identified species-specific patterns of sensitivity or tolerance to pesticides and other experimental factors, thereby identifying them as potential bioindicators. These candidate species represent a first step toward a diatom-based index for pesticide stress assessment in Swiss streams. These findings highlight the need for realistic, multifactorial experiments to assess the impact of stressors in aquatic ecosystems.

The European Union (EU) regulates chemicals to protect the environment, but different regulations apply depending on the intended use of the substances in question. Advances in chemical monitoring have revealed inconsistencies in environmental risk assessments, prompting the European Commission to advocate for a “one substance, one assessment” (OS-OA) approach. As part of the EU Partnership for the Assessment of the Risk from Chemicals (PARC), this study examines the implementation and outcome of environmental risk assessments carried out within different regulatory frameworks, focusing on the aquatic environment. Using case studies on imidacloprid and deltamethrin, we highlight methodological differences and their implications for OS-OA. Our analysis reveals little consistency in the data used by assessments in different regulatory processes. This is partially due to the historical development of risk assessments. In addition, we show that new scientific data are not consistently incorporated into risk assessments, leading to delays and prolonged environmental risks. Finally, we demonstrate that low analytical sensitivities contribute to low detection rates in monitoring programs and hinder comparisons between prospective and retrospective risk assessments. Differences in data accessibility and validity assessments and lack of collaboration and varying involvement of Member States contribute to these inconsistencies and underscore the need for standardized methods. As a result of different data requirements, models, and protection goals, isolated risk assessments of the same substance lead to divergent outcomes. In cases where data gaps exist and safe uses cannot be demonstrated, we strongly recommend read-across of hazard assessments between regulations to support more efficient regulatory conclusions. In summary, our findings highlight the need for coherent regulation and risk assessment to improve environmental protection in the EU.

Background: For use in cosmetic products, 32 substances have been authorised in the EU as UV-filters as of August 2022 (Annex VI of the EU Cosmetics Regulation (EC) No 1223/2009). Although these substances can enter the aquatic environment directly through bathing, authorisation for use in cosmetic products does not require a specific environmental risk assessment, whereas risks to human health are specifically assessed. Furthermore, no environmental quality standards have been proposed at EU level. For the current review, data on freshwater ecotoxicity, physicochemical properties, environmental fate and measured exposure were retrieved from ECHA registration information and public databases and assessed for reliability and relevance. Environmental quality standards (EQS) were proposed based on the EU technical guidance for EQS for the Water Framework Directive (WFD). Results: From a WFD perspective, there were significant or complete gaps for acute and chronic effects data, sediment organisms and rarely tested organisms at the time of data retrieval, as well as gaps for measured environmental concentrations in the assessed databases. The reliability of the reported data could not always be verified due to missing information. As expected from the heterogeneity of molecular structures, ecotoxicity data and environmental fate parameters vary considerably between the different substances. Our assessments indicate that the use of some of the substances in direct contact with surface water may pose a repeated risk to aquatic organisms. Conclusions: We recommend a revision of the process for the inclusion of UV-filters in the EU Cosmetics Product Regulation, taking into account the potential environmental risks. A full assessment of all UV-filters using standard test organisms as well as rarely tested species for acute and chronic effects and bioaccumulation would require, among other things, a large number of fish tests. Therefore, new assessment methods (NAMs) are recommended, including the use of fish cell lines for acute toxicity testing and alternatives for the assessment of chronic toxicity.

The progress in chemical analytics and understanding of pesticide dynamics in surface waters allows establishing robust data on compounds with frequent exceedances of quality standards. The current chemical, temporal, and spatial coverage of the pesticide monitoring campaigns differs strongly between European countries. A questionnaire revealed differences in monitoring strategies in seven selected European countries; Nordic countries prioritize temporal coverage, while others focus on spatial coverage. Chemical coverage has increased, especially for non-polar classes like synthetic pyrethroids. Sweden combines monitoring data with agricultural practices for derived quantities, while the Netherlands emphasizes spatial coverage to trace contamination sources. None of the EU member states currently has established a process for linking chemical surface water monitoring data with regulatory risk assessment, while Switzerland has recently established a legally defined feedback loop. Due to their design and objectives, most strategies do not capture concentration peaks, especially 2-week composite samples, but also grab samples. Nevertheless, for substances that appear problematic in many data sets, the need for action is evident even without harmonization of monitoring programs. Harmonization would be beneficial, however, for cross-national assessment including risk reduction measures.

Microplastics (MPs) in natural waters are heterogeneously mixed with other natural particles including algal cells and suspended sediments. An easy-to-use and rapid method for directly measuring and distinguishing MPs from other naturally present colloids in the environment would expedite analytical workflows. Here, we established a database of MP scattering and fluorescence properties, either alone or in mixtures with natural particles, by stain-free flow cytometry. The resulting high-dimensional data were analyzed using machine learning approaches, either unsupervised (e.g., viSNE) or supervised (e.g., random forest algorithms). We assessed our approach in identifying and quantifying model MPs of diverse sizes, morphologies, and polymer compositions in various suspensions including phototrophic microorganisms, suspended biofilms, mineral particles, and sediment. We could precisely quantify MPs in microbial phototrophs and natural sediments with high organic carbon by both machine learning models (identification accuracies over 93%), although it was not possible to distinguish between different MP sizes or polymer compositions. By testing the resulting method in environmental samples through spiking MPs into freshwater samples, we further highlight the applicability of the method to be used as a rapid screening tool for MPs. Collectively, this workflow can be easily applied to a diverse set of samples to assess the presence of MPs in a time-efficient manner.

Plastics, especially microplastics (<5 mm in length), are anthropogenic polymer particles that have been detected in almost all environments. Microplastics are extremely persistent pollutan...

Stream biofilms have been shown to be among the most sensitive indicators of environmental stress in aquatic ecosystems and several endpoints have been developed to measure biofilm adverse effects caused by environmental stressors. Here, we compare the effects of long-term exposure of stream biofilms to diuron, a commonly used herbicide, on several traditional ecotoxicological endpoints (biomass growth, photosynthetic efficiency, chlorophyll-a content, and taxonomic composition), with the effects measured by recently developed methods [community structure assessed by flow cytometry (FC-CS) and measurement of extracellular polymeric substances (EPS)]. Biofilms grown from local stream water in recirculating microcosms were exposed to a constant concentration of 20 μg/L diuron over a period of 3 weeks. During the experiment, we observed temporal variation in photosynthetic efficiency, biomass, cell size, presence of decaying cells and in the EPS protein fraction. While biomass growth, photosynthetic efficiency, and chlorophyll-a content were treatment independent, the effects of diuron were detectable with both FC and EPS measurements. This demonstrates that, at least for our experimental setup, a combination of different ecotoxicological endpoints can be important for evaluating biofilm environmental stress and suggests that the more recent ecotoxicological endpoints (FC-CS, EPS protein content and humic substances) can be a useful addition for stream biofilm ecotoxicological assessment.