Pesticide Mixtures in Surface Waters of Two Protected Areas in Southwestern Germany.

Pesticides enter non-target surface waters as a result of agricultural activities and may reach water bodies in protected areas. We measured in southwestern Germany pesticide concentrations after heavy rainfalls in streams of a drinking water protection area near Hausen (Freiburg) and in the catchment of the Queich (Landau), which originates from the biosphere reserve Palatinate Forest. On average, 32 (n = 21) and 21 (n = 10) pesticides were detected per sample and event in the area of Hausen (n = 56) and in the Queich catchment (n = 17), respectively. The majority of pesticides detected in > 50% of all samples were fungicides, with fluopyram being detected throughout all samples. Aquatic invertebrates exhibited highest risks with 16.1% of samples exceeding mixture toxicity thresholds, whereas risks were lower for aquatic plants (12.9%) and fish (6.5%). Mixture toxicity threshold exceedances indicate adverse ecological effects to occur at half of sites (50%). This study illustrates the presence of pesticide mixtures and highlights ecological risks for aquatic organisms in surface waters of protected areas in Germany.

Neonicotinoid insecticides in global agricultural surface waters - Exposure, risks and regulatory challenges.

Neonicotinoids are the most widely used insecticides worldwide. However, the widespread usage of neonicotinoids has sparked concerns over their effects on non-target ecosystems including surface waters. We present here a comprehensive meta-analysis of 173 peer-reviewed studies (1998-2022) reporting measured insecticide concentrations (MICs; n = 3983) for neonicotinoids in global surface waters resulting from agricultural nonpoint source pollution. We used compound-specific regulatory threshold levels for water (RTLSW) and sediment (RTLSED) defined for pesticide authorization in Canada, the EU and the US, and multispecies endpoints (MSESW) to assess acute and chronic risks of global neonicotinoid water-phase (MICSW; n = 3790) and sediment (MICSED; n = 193) concentrations. Results show a complete lack of exposure information for surface waters in >90 % of agricultural areas globally. However, available data indicates for MICSW overall acute risks to be low (6.7 % RTLSW_acute exceedances), but chronic risks to be of concern (20.7 % RTLSW_chronic exceedances); exceedance frequencies were particularly high for chronic MSESW (63.3 %). We found RTLSW exceedances to be highest for imidacloprid and in less regulated countries. Linear model analysis revealed risks for global agricultural surface waters to decrease significantly over time, potentially biased by the lack of sensitive analytical methods in early years of neonicotinoid monitoring. The Canadian, EU and US RTLSW differ considerably (up to factors of 223 for RTLSW_acute and 13,889 for RTLSW_chronic) for individual neonicotinoids, indicating large uncertainties and regulatory challenges in defining robust and protective RTLs. We conclude that protective threshold levels, in concert with increasing monitoring efforts targeting agricultural surface waters worldwide, are essential to further assess the ecological consequences from anticipated increases of agricultural neonicotinoid uses.

Pesticide occurrence in protected surface waters in nature conservation areas of Germany.

A complete ban on pesticide use in sensitive areas, such as nature conservation areas (NCA), is currently being debated in the EU as part of the Sustainable Use Regulation. NCA are strictly protected landscapes in Germany with minimal agricultural activity (<4.5 %) that serve as vital ecological refuges. However, it is largely unknown whether surface waters in German NCA are contaminated by pesticides. The current study uses extensive monitoring data (n = 3,822,553 measurements, 1998-2020, 208 pesticides) from the federal state of Saxony (18,416 km2), Germany, to characterize pesticide occurrence, contamination levels and risks (defined as exceedance of regulatory threshold levels) for surface waters in NCA (n = 68,277 measurements, mean size = 2.5 km2) in comparison to unprotected areas (n = 3,754,276). Pesticide detection frequencies show strong correlation between NCA and unprotected areas (UPA, R2= 0.70-0.92), but concentrations to be ∼40 % lower in protected areas. Ecological risk distributions for three major species groups are similar between NCA and UPA (fish = 79.8 % overlap in density distribution, invertebrates = 78.6 %, plants = 81.9 %). Threshold exceedances differ greatly among groups (fish = 0.9 %, aquatic invertebrates = 14.7 %, plants = 20.4 %). Based on principal component analysis, ecological risks for aquatic plants and aquatic invertebrates are strongly correlated with upstream agricultural land use (80.5-82.4 %) and are negatively correlated with upstream (semi)-natural land cover (90.1-97.3 %). Fluvial transport appears to be the most important pathway for contaminants into NCA surface waters, likely due to small conservation area size. Overall, surface waters in NCA are exposed to numerous organic contaminants causing ecological risks, highlighting the need to improve protection of these valuable water resources.

Trends of Total Applied Pesticide Toxicity in German Agriculture.

Expressing temporal changes in the use of pesticides, based not only on amounts (masses) but also on their toxicity for different species groups, was proposed as a sensible approach for evaluating potential environmental risks. Here, we calculated the total applied toxicity (TAT) between 1995 and 2019 for Germany, mapped it, and compared it to the US TAT and other risk indicators. Results show that the German TAT for terrestrial vertebrates decreased over time by about 20%. The TAT increased by a factor of three for fishes, largely due to insecticides, by a factor of two for soil organisms, largely due to fungicides and insecticides, and, to a lower extent, for terrestrial plants, solely due to herbicides. Other species groups showed no trends in TAT, which for pollinators likely results from neonicotinoid use restrictions. Many TAT trends from Germany and the US differ, partly due to different insecticide and fungicide uses. TAT, SYNOPS risk indicators, and the EU Harmonized Risk Indicators, currently being used to assess the German National Action Plan's goal to reduce risks by 30% by 2023, lead to clearly different risk perceptions. Validated approaches are needed for evaluation of risk quantifications at the national scale.

Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops.

Pesticide impacts are usually discussed in the context of applied amounts while disregarding the large but environmentally relevant variations in substance-specific toxicity. Here, we systemically interpret changes in the use of 381 pesticides over 25 years by considering 1591 substance-specific acute toxicity threshold values for eight nontarget species groups. We find that the toxicity of applied insecticides to aquatic invertebrates and pollinators has increased considerably-in sharp contrast to the applied amount-and that this increase has been driven by highly toxic pyrethroids and neonicotinoids, respectively. We also report increasing applied toxicity to aquatic invertebrates and pollinators in genetically modified (GM) corn and to terrestrial plants in herbicide-tolerant soybeans since approximately 2010. Our results challenge the claims of a decrease in the environmental impacts of pesticide use.

Water quality and ecological risks in European surface waters - Monitoring improves while water quality decreases.

Aquatic ecosystems are at risk of being impaired by various organic chemicals, however comprehensive large-scale evaluations of waterbodies' status and trends are rare. Here, surface water monitoring data, gathered as part of the EU Water Framework Directive and comprising the occurrence of 352 organic contaminants (>8.3 mil. measurements; 2001-2015; 8213 sites) in 31 European countries, was used to evaluate past and current environmental risks for three aquatic species groups: fish, invertebrates, plants. Monitoring quality indices were defined per country and found to improve over time. Relationships became apparent between countries' monitoring quality index and their success in detecting contaminants. Across the EU, contaminants were more frequently found in recent years. Overall, 35.7% (n = 17,484) of sites exceeded at least one acute regulatory threshold level (RTL) each year, and average risks significantly increased over time for fish (τ = 0.498, p = 0.01) and aquatic invertebrates (τ = 0.429, p = 0.03). This indicates an increased chemical pressure to Europe's waterbodies and overall large-scale threshold exceedances. Pesticides were identified as the main risk drivers (>85% of RTL exceedances) with aquatic invertebrates being most acutely at risk in Europe. Agricultural land-use was clearly identified as the primary spatial driver of the observed aquatic risks throughout European surface waters. Issues in monitoring data heterogeneity were highlighted and also followed by subsequent improvement recommendations, strengthening future environmental quality assessments. Overall, aquatic ecosystem integrity remains acutely at risk across Europe, signaling the demand for continued improvements.

Aquatic pesticide exposure in the U.S. as a result of non-agricultural uses.

Non-agricultural uses of pesticides are common in the U.S. and may thus lead to exposure of non-target ecosystems such as urban waterways. However, surface water exposure resulting from agricultural pesticide uses has received substantially more attention during the last decades. Here we conducted a literature review and meta-analysis of peer-reviewed studies to identify measured environmental concentrations (MEC) of pesticides in perennial surface water bodies due to non-agricultural uses in the U.S. Acute and chronic Aquatic Life Benchmarks (ALBacute, ALBchronic) for water-phase concentrations and regulatory threshold levels (RTLSED) for sediment concentrations were used for risk evaluations. Based on 10,755 MECs retrieved from 70 scientific studies, results show that a multitude of pesticide compounds (approx. 150) have been detected at 609 urban surface water sites. Particularly herbicides and insecticides were among the most frequently detected compounds in the water phase, whereas insecticides dominated detections in sediments. While overall acute (5.64% ALBacute exceedances; n = 9034 MEC) and chronic (9.31% ALBchronic exceedances; n = 9036 MEC) risks were comparably low in the water phase, 35% of sediment concentrations (n = 1621 MEC) exceeded RTLSED. Insecticides and particularly pyrethroids were identified as the main drivers of benchmark exceedances in both the water phase and sediments. In addition to pesticide type, a linear model analysis identified further drivers important for risks such as sampling methods. Overall insecticide risks in non-agricultural surface waters were significantly (by a factor of 1.9) lower than those already known from agricultural surface waters in the U.S. However, substantially higher risks in sediments were identified for urban compared with agricultural waterbodies. The present study provides the first comprehensive assessment of pesticides in urban surface waters in the U.S. with overall results indicating common occurrence and non-negligible risks particularly due to urban insecticide uses.

Insecticide Risk in US Surface Waters: Drivers and Spatiotemporal Modeling.

Although pesticide contamination in agricultural surface waters is a common phenomenon, large-scale studies dealing with the responsible drivers are rare. We used data from 259 publications reporting 5830 individual water or sediment concentrations of 32 insecticides and their metabolites in 644 US surface waters to determine the factors driving insecticide risks, that is, exceedance of regulatory threshold levels (RTLs). Multiple linear regressions (R2 adj. = 49.6-76.5) revealed that toxicity-normalized agricultural insecticide use (i.e. use divided by toxicity) was the most important driver. Burst rainfall erosivity and irrigation practices also had risk-promoting effects, whereas time, catchment size, and sampling interval had risk-demoting effects. A regression model (R2 adj. = 62.2, n = 1833) for small, medium, and large running waters was validated and used for risk mapping at the national scale, highlighting multiple regions, where the comparison of predicted insecticide concentrations with their RTLs indicate adverse conditions for aquatic organisms. Particularly in smaller streams, risks were most pronounced with an average RTL exceedance frequency of 27.7% in all grid cells (n = 9968). Finally, mixture toxicity was mainly (about 76.7%) explained by the most toxic compound in the mixture, causing ∼95.7% of RTL exceedances. Identifying the factors, which drive exposure for all relevant insecticide classes, and subsequently mapping these risks for surface waters of various sizes across the U.S., will support future risk management.

Meta-Analysis of Insecticides in United States Surface Waters: Status and Future Implications.

Agricultural insecticides occur in U.S. surface waters, yet our knowledge of their current and potential future large-scale risks for biodiversity is restricted. Here, we conducted a meta-analysis of measured insecticide concentrations (MICs; n = 5817; 1962-2017) in U.S. surface waters and sediments reported in 259 peer-reviewed scientific studies for 32 important insecticide compounds and their degradation products ( n = 6). To assess overall and substance-specific ecological risks and future implications, MICs were compared with official U.S. Environmental Protection Agency regulatory threshold levels (RTLs) and insecticide use trends. Approximately half of the MICs, i.e., 49.4% (at 69.7% of the 644 sites covered), exceeded their RTLs, indicating substantial risks to the integrity of U.S. aquatic ecosystems and potential shortcomings of regulatory risk assessment procedures. Overall, pyrethroids had the highest exceedance rate (80.7%; n = 1808), followed by organophosphates and carbamates (42.2%, n = 2618), and organochlorines (33.3%, n = 468). Pronounced increasing use trends were found for neonicotinoids, which exceeded their chronic RTLs, i.e., those of high relevance due to neonicotinoids̀ persistence in surface waters, for 56.8% of MICs (22.2% for acute RTLs). A regression analysis of insecticide use trends, although to be interpreted with care, indicated a future increase in applied amounts of several high risk insecticides such as pyrethroids and neonicotinoids, suggesting elevated prospective risks for U.S. surface waters, biodiversity, and endangered species.

Long-term effects of fungicides on leaf-associated microorganisms and shredder populations-an artificial stream study.

Leaf litter is a major source of carbon and energy for stream food webs, while both leaf-decomposing microorganisms and macroinvertebrate leaf shredders can be affected by fungicides. Despite the potential for season-long fungicide exposure for these organisms, however, such chronic exposures have not yet been considered. Using an artificial stream facility, effects of a chronic (lasting up to 8 wk) exposure to a mixture of 5 fungicides (sum concentration 20 µg/L) on leaf-associated microorganisms and the key leaf shredder Gammarus fossarum were therefore assessed. While bacterial density and microorganism-mediated leaf decomposition remained unaltered, fungicide exposure reduced fungal biomass (≤71%) on leaves from day 28 onward. Gammarids responded to the combined stress from consumption of fungicide-affected leaves and waterborne exposure with a reduced abundance (≤18%), which triggered reductions in final population biomass (18%) and in the number of precopula pairs (≤22%) but could not fully explain the decreased leaf consumption (19%), lipid content (≤43%; going along with an altered composition of fatty acids), and juvenile production (35%). In contrast, fine particulate organic matter production and stream respiration were unaffected. Our results imply that long-term exposure of leaf-associated fungi and shredders toward fungicides may result in detrimental implications in stream food webs and impairments of detrital material fluxes. These findings render it important to understand decomposer communities' long-term adaptational capabilities to ensure that functional integrity is safeguarded. Environ Toxicol Chem 2017;36:2178-2189. © 2017 SETAC.