Occurrence of boscalid and other selected fungicides in surface water and groundwater in three targeted use areas in the United States

Monitoring and Risk Assessment of Pesticide Residues in Fishery Products Using GC-MS/MS in South Korea

The aim of this study was to assess the risk of pesticide contamination in aquaculture and its impact on fishery products. We conducted an assessment of 300 samples collected from nine regions in South Korea, including various types of seafood, such as freshwater fish, marine fish, crustaceans, and shellfish. Pesticide residues in seafood were analyzed using GC-MS/MS after sample preparation using a modified QuEChERS method, revealing the presence of eight pesticides (4,4'-DDE, 4,4'-DDT, boscalid, isoprothiolane, oxadiazon, pendimethalin, thifluzamide, and trifluralin) across seven fish species (carp, far eastern catfish, crucian carp, eel, Chinese muddy loach, mirror carp, and sea bass). Following the grouping of DDE with DDT, a risk assessment of fishery products was conducted. After the estimated daily intake (EDI) of fish was calculated and compared with the acceptable daily intake (ADI), the health risk index (HI, %ADI) of the detected pesticides was evaluated and found to be 1.07% or lower. The results suggest that the consumption of domestically farmed fish products in South Korea poses minimal health risks associated with pesticide residues.

Cardiac and neurobehavioral impairments in three phylogenetically distant aquatic model organisms exposed to environmentally relevant concentrations of boscalid

Boscalid (2-Chloro-N-(4'-chlorobiphenyl-2-yl) nicotinamide), a pyridine carboxamide fungicide, is an inhibitor of the complex II of the respiration chain in fungal mitochondria. As boscalid is only moderately toxic for aquatic organisms (LC50 > 1-10 mg/L), current environmental levels of this compound in aquatic ecosystems, in the range of ng/L-μg/L, are considered safe for aquatic organisms. In this study, we have exposed zebrafish (Danio rerio), Japanese medaka (Oryzias latipes) and Daphnia magna to a range of concentrations of boscalid (1-1000 μg/L) for 24 h, and the effects on heart rate (HR), basal locomotor activity (BLA), visual motor response (VMR), startle response (SR), and habituation (HB) to a series of vibrational or light stimuli have been evaluated. Moreover, changes in the profile of the main neurotransmitters have been determined. Boscalid altered HR in a concentration-dependent manner, leading to a positive or negative chronotropic effect in fish and D. magna, respectively. While boscalid decreased BLA and increased VMR in Daphnia, these behaviors were not altered in fish. For SR and HB, the response was more species- and concentration-specific, with Daphnia exhibiting the highest sensitivity. At the neurotransmission level, boscalid exposure decreased the levels of L-aspartic acid in fish larvae and increased the levels of dopaminergic metabolites in D. magna. Our study demonstrates that exposure to environmental levels of boscalid alters cardiac activity, impairs ecologically relevant behaviors, and leads to changes in different neurotransmitter systems in phylogenetically distinct vertebrate and invertebrate models. Thus, the results presented emphasize the need to review the current regulation of this fungicide.

A screening-level human health risk assessment of dietary intake of pesticide residues in produce as compared to consumer guide recommendations

Consumers are confronted with conflicting information regarding the safety of specific foods. For example, the Environmental Working Group (EWG) publishes an annual consumer guide in which they rank the pesticide contamination of 46 popular fruits and vegetables, which includes designating the 12 with the greatest pesticide contamination as the "Dirty Dozen," to help consumers reduce exposures to toxic pesticides. However, consumer guides like EWG's only incorporate some hazard assessment principles and do not reflect a dietary risk assessment. Therefore, the purpose of this study is to apply risk assessment techniques to EWG's Dirty Dozen list using a uniform screening-level approach to estimate pesticide exposures for U.S. consumers and to characterize the associated chronic human health risks. The most commonly detected pesticide and its representative residue concentrations were identified for each produce type on the 2022 Dirty Dozen list using the USDA Pesticide Data Program database. Estimates of mean dietary consumption in the U.S. were used to calculate dietary exposure to each pesticide-produce combination for adults and children. Pesticide-specific U.S. EPA dietary health-based guidance values (HBGVs) were then used as benchmarks to evaluate the chronic human health risk of consuming each produce type. Overall, the estimated daily exposure for each pesticide-produce combination was below the corresponding HBGV for all exposure scenarios. The current analysis demonstrates that excessive produce-specific pesticide exposure is unexpected as the amount of produce that would need to be consumed on a chronic basis, even among children, far exceeds typical dietary intake. Future research is necessary to assess acute dietary exposure scenarios and to consider cumulative risk.

Strobilurin fungicide increases the susceptibility of amphibian larvae to trematode infections

The global rise in fungal pathogens has driven the increased usage of fungicides, yet our understanding of their ecotoxicity remains largely limited to acute toxicity. While such data is critical for projecting the risk of fungicide exposure to individual species, the contamination of natural systems with fungicides also has the potential to alter species interactions within communities including host-parasite relationships. We examined the effects of the fungicide pyraclostrobin on the susceptibility of larval American bullfrogs (Rana catesbeiana) to trematode (echinostome) infections using a controlled laboratory experiment. Following a 2-wk exposure to 0, 1.0, 5.2, or 8.4 µg/L of pyraclostrobin, tadpoles were then exposed to parasites either in the 1) presence (continued/simultaneous exposure) or 2) absence (fungicide-free water) of pyraclostrobin. We found that when exposed to pyraclostrobin during parasite exposure, meta cercariae counts increased 4 to 8 times compared to control tadpoles. Additionally, parasite loads were approximately 2 times higher in tadpoles with continued fungicide exposures compared to tadpoles that were moved to fresh water following fungicide exposure. This research demonstrates that fungicides at environmentally relevant concentrations can indirectly alter host-parasite interactions, which could elevate disease risk. It also underscores the need for studies that expand beyond traditional toxicity experiments to assess the potential community and ecosystem-level implications of environmental contaminants.

Impacts of pyraclostrobin on intestinal health and the intestinal microbiota in common carp (Cyprinus carpio L.)

Pyraclostrobin (PYR) is a strobilurin fungicide that is commonly used in agriculture, and its use in agriculture may lead to an increase in its residue in the aquatic environment and may have a deleterious influence on the intestinal health of aquatic creatures. Here, common carp were chronically exposed to PYR (0, 0.5, or 5.0 μg/L) for 30 d to determine its effect on the physical and immunological barrier and intestinal microbiota in the intestine. PYR exposure caused significant histological changes; altered the mRNA expression levels of occludin, claudin-2, and zonula occludens-1 (ZO-1); induced oxidative stress in the common carp intestine; and increased the serum D-lactate and diamine oxidase (DAO) levels. Moreover, PYR significantly increased the protein expression levels of tumour necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and IL-6 while decreasing the level of transforming growth factor beta (TGF-β). Further studies revealed that PYR significantly reduced lysozyme (LZM) and acid phosphatase (ACP) activities as well as complement 3 (C3) and immunoglobulin M (IgM) levels. Furthermore, PYR decreased gut microbial diversity while increasing the abundance of pathogenic bacteria such as Aeromonas and Shewanella, causing an intestinal microbial disturbances in common carp. These results imply that PYR has a negative impact on fish intestinal health and may pose serious health risks to fish by disrupting the intestinal microbiota, physical barrier, and immunological barrier in common carp.

Evidence of strobilurin fungicides and their metabolites in Dongjiang River ecosystem, southern China: Bioaccumulation and ecological risks

Despite the widespread application of strobilurin fungicides (SFs) in agriculture, little is known about their distribution and bioaccumulation in aquatic ecosystems. In this study, the concentrations of 12 SFs and two of their metabolites were determined in abiotic (water and sediment; n = 83) and biotic (plant, algae, zooplankton, and fish; n = 123) samples collected from a subtropical freshwater ecosystem, namely, Dongjiang River wetland, in southern China. Among the 12 SFs measured, azoxystrobin (AZ) was the major fungicide found in surface water (median: 2.20 ng/L) and sediment (0.064 ng/g dry wt.). Azoxystrobin acid (AZ-acid), a metabolite of AZ, was the major analyte in the plant samples and had a median concentration at 0.36 ng/g dry wt. In algae and zooplankton, (Z)-metominostrobin was the predominant fungicide and had median concentrations of 3.52 and 5.55 ng/g dry wt., respectively. In fish muscle, dimoxystrobin (DIMO) was the major SF and had a median concentration of 0.47 ng/g dry wt. The bioconcentration factor (BCF) values of AZ-acid, trifloxystrobin (TFS), and pyraclostrobin (PYR) in algae and zooplankton and AZ-acid, PYR, TFS, TFS-acid, picoxystrobin, and DIMO in fish muscle exceeded 1000 L/kg (algae, zooplankton, and fish concentrations were expressed on a dry weight basis), suggesting that these fungicides can accumulate in biota. A positive association between log BCFs of SFs in fish and logKow of SFs and a negative correlation between log BCFs and the log solubility index were observed. Additionally, the risk quotient (RQ) was calculated to evaluate the potential ecotoxicological risk of SFs to different aquatic organisms (algae, zooplankton, and fish). The PYR and DIMO concentrations at 19 sampling sites had RQ values >0.1, indicating moderate ecotoxicological risks to aquatic organisms. This study is the first to document the widespread occurrence of SFs and their metabolites in aquatic ecosystems and to elucidate the bioaccumulation potential of SFs in aquatic organisms.

An integrated One Health framework for holistic evaluation of risks from antifungal agents in a large-scale multi-city study

A new framework for retrospective mass spectral data mining for antifungal agents (AFs) and Wastewater-Based Epidemiology (WBE) was developed as part of One Health framework to tackle risks from AFs. A large scale, multi-city study was undertaken in South-West England. Key drivers of AFs in the catchment were identified with communal wastewater discharges being the main driver for human AFs (fluconazole, ketoconazole) and agricultural runoff being the main driver for pesticide AFs (prochloraz, prothioconazole and tebuconazole). Average WBE-estimated human used fluconazole and ketoconazole PNDIs (population normalised daily intake) exceeded 300 mg day-1 1000 inh-1 and 2000 mg day-1 1000 inh-1. This is much higher than PNDPs (population normalised daily prescriptions <40 mg day-1 1000 inh-1 and <80 mg day-1 1000 inh-1 for fluconazole and ketoconazole respectively). This was expected due to both prescription and over-the-counter usage, and both oral and topical applications. Pesticide AF, prothioconazole had PNDIs <40,000 mg day-1 1000 inh -1, which gave intake: 0.43, 0.26, 0.07 mg kg-1 in City A, B, and C, likely due to accounting for external/non-human sources. This is higher than the acceptable daily intake (ADI) of 0.01 mg kg-1bw day-1, which warrants further study. Intake per kg of body weight estimated using tebuconazole was 0.86, 1.39, 0.12, 0.13, and 2.7 mg kg-1 in City A-E respectively and is likely due to external/non-human sources. Intake calculated using its metabolite was 0.02 and 0.01 mg kg-1 in City B and C respectively, which aligned with ADI (0.03 mg kg-1bw day-1). The environmental risk assessment of AFs indicated low/medium risk from fluconazole, prochloraz, and tebuconazole, medium risk from epoxiconazole, prothioconazole's metabolite, and tebuconazole, and high risk for prothioconazole in river water. High risk was estimated from fluconazole, epoxiconazole, prothioconazole and its metabolite, tebuconazole, ketoconazole in wastewater samples, which is important during raw sewage discharge events via sewer overflows.

Evaluation of the toxic effects of fluindapyr, a novel SDHI fungicide, to the earthworms Eisenia fetida

The emergence of resistance to existing succinate dehydrogenase inhibitor fungicides (SDHIs) calls for the urgent innovation of novel formulations, but also results in an increase information gap on the ecological risks of novel SDHIs especially to non-target organisms. Herein, the environmental behavior and toxicological effects of a novel SDHI, fluindapyr (FIP), were evaluated using earthworm as model non-target organism. Results showed that FIP had a relatively shorter half-live (about 28 days) in artificial soil compared with traditional SDHIs. Besides, FIP exhibited a rapid uptake and bioaccumulation trend in earthworms. For the toxicological effects, FIP suppressed earthworm growth (≥ 5 mg/kg) and reproduction (≥ 1 mg/kg) whereas no lethal effects were observed up to the highest tested concentration of 25 mg/mg. FIP of high exposure concentrations also induced serious epidermis and intestines damage as well as oxidative stress to earthworms after 28-day exposure. In addition, expression of oxidative damage related genes (CAT, CRT, GST, HSP70, SOD) was further verified after FIP exposure. The earthworm Tier 1 RQ also indicated a potential risk for earthworm reproduction. Data presented here may be useful for the risk assessments of FIP in soil ecosystems and help to set appropriate precautions to ensure protection against novel SDHIs.

Fungicides modify pest insect fitness depending on their genotype and population

Fungicides are the most sold pesticide group, with an 8% increase in sales in Europe within the last decade. While adverse short-term fungicide effects on non-target insect species have been reported, the long-term effects and their impact on fitness are unclear. As the effects may depend on both the fungicide and the genetic background of the species, we investigated the effects of the commonly used fungicide, fluazinam, on the Colorado potato beetle's life history traits, and whether the effects were dependent on a previously characterized insecticide resistance mutation (S291G in acetylcholinesterase-2 gene) in different populations. Our findings show that fungicide exposure can have both negative and positive, long-lasting effects on beetles, depending on the parental insecticide resistance status and population. In the Belchow population, individuals carrying resistance mutation had higher survival, but they produced offspring with lower egg-hatching rates. While, in the Vermont population, fungicide exposure increased the body mass and offspring quality in the beetles carrying resistance mutation but did not affect the beetles' survival. Our results suggest that commonly used fungicides can have both negative and positive effects on pest insects' life-history, however, their impact may differ depending on the population and parental genetic background.

An insight into the sorption kinetics of boscalid onto soils: Effect of general soil properties

Boscalid is a carboxamide fungicide widely used for crop protection, however owing to its high persistence, it is detected in high concentrations in various environments. Since the fate of such xenobiotics is strongly influenced by its interaction with soil components a better understanding of its adsorption onto soils of varying properties could allow the adjustment of its application in a given agro-ecological region to limit the consequent environmental burden. The present investigation was carried out to examine the kinetics of boscalid adsorption onto ten Indian soils of varying physico-chemical properties. Kinetic data of boscalid for all soils under investigation fitted well to both pseudo-first-order and pseudo-second-order kinetic models. However, based on the standard error of estimate (S.E._est.) values pseudo-first-order model was better for all soil samples, except one soil which had the lowest readily oxidizable organic carbon. Adsorption of boscalid by soils appeared to be controlled by the diffusion-chemisorption process while for soils especially rich in readily oxidizable organic carbon or clay + silt content the intra-particle diffusion process seemed to be more important. Stepwise regression of kinetic parameters on soil properties revealed that the inclusion of a set of some soil properties could help better prediction of adsorbed amounts of boscalid and kinetic constants. These findings may help assess the fate and possible transport of boscalid fungicide in different soils.

Ocean current redistributed the currently using Organoamine Pesticides in Arctic summer water

In a comprehensive study on the presence and distribution of Currently Using Organoamine Pesticides (CUOAPs) in the Arctic Ocean, this study collected and analyzed 36 surface seawater samples during the summer of 2021. The study detected 36 CUOAPs, 17 of these compounds at levels exceeding the Method Detection Limits (MDLs). Concentrations of CUOAPs ranged from 0.11 to 2.94 ng/L, exhibiting an average of 1.83 ± 0.83 ng/L. Spatial distribution analysis revealed lower CUOAP concentrations in the central Arctic Ocean, with Cycloate constituting the most abundant component (23.66 %). The investigation identified terrestrial inputs and long-range atmospheric transport as potential sources of CUOAPs in the Arctic Ocean region. The origins of individual CUOAPs appeared to be associated with application procedures and their propensity for co-occurrence at low latitudes. The study also examined the role of ocean currents in the transport and redistribution of CUOAPs in surface seawater across different regions. While ocean currents played a significant role, the influence of sea ice cover on CUOAP distribution was minimal. An ecological risk assessment analysis underscored the need for regional attention to the presence of CUOAPs in the Arctic Ocean.

Acute exposure of Isopyrazam damages the developed cardiovascular system of zebrafish (Danio rerio)

Isopyrazam (IPZ) is one of the broad-spectrum succinate dehydrogenase inhibitor fungicides (SDHIs). Although the potential bio-toxicity of SDHIs has been reported hourly, the specific effects focused on the cardiovascular system have remained unclear and piecemeal. Thus, we chose IPZ as a representative to observe the cardiovascular toxicity of SDHIs in zebrafish. Two types of transgenic zebrafish, Tg (cmlc2:GFP) and Tg (flk1:GFP) were used in this study. Healthy embryos at 6 hpf were exposed to IPZ solutions. The statistical data including survival rate, hatching rate, malformed rate, and morphological and functional parameters of the cardiovascular system at 48 hpf and 72 hpf demonstrated that IPZ could cause abnormalities and cardiovascular defects such as spinal curvature, dysmotility, pericardial edema, pericardial hemorrhage, and slowed heart rate, etc. At the same time, the activity of enzymes related to oxidative stress was altered with IPZ. Our results revealed that IPZ-induced cardiovascular toxicity and oxidative stress might be one of the underlying toxic mechanisms.

Refining acute human exposure assessment to pesticides in surface water: An integrated data-driven modeling approach

The substantial spatial and temporal variability of pesticides has led to large uncertainties when determining their peak aqueous concentrations. There is however a lack of large-scale studies dealing with accurate determination of annual maximum daily concentration (AMDC) across the landscape and over time based on the publicly available monitoring data. We developed a novel data-driven approach that firstly used time series modeling to generate AMDCs for qualified water monitoring sites in the conterminous U.S. With feature variables such as pesticide use and land cover compiled into the dataset, machine learning models using eXtreme Gradient Boosting (XGBoost) and Random Forest Regressor (RF) were then developed to estimate AMDCs in surface waters across the U.S. Both models exhibited significant predictability, while a hybrid model consisting of the average predictions by XGBoost and RF model had the highest prediction accuracy (mean absolute error (MAE): 1.23; R²: 0.61). The analysis of permutation variable importance indicated that pesticide use and drainage area were the two most important drivers. Partial dependence analysis revealed that pesticide use, precipitation, cultivated crop land cover and solubility exhibited concentration-promoting effects, whereas drainage area and molecular weight had concentration-demoting effects. Soil adsorption coefficient (Koc) showed nonmonotonic effects. The hybrid model was used to predict and map AMDCs of four example pesticides, including 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine, glyphosate and imidacloprid during 2016-2019 at national scale. The predictive capability was validated using independent monitoring datasets. The fully evaluated approach significantly reduced the uncertainties in modeling annual peak concentrations and served as a valuable solution for conducting geographically oriented, highly refined exposure assessments for pesticides.

UDP-Galactopyranose Mutase Mediates Cell Wall Integrity, Polarity Growth, and Virulence in Fusarium graminearum

CHY1 is a zinc finger protein unique to microorganisms that was found to regulate polarized tip growth in Fusarium graminearum, an important pathogen of wheat and barley. To further characterize its functions, in this study we identified CHY1-interacting proteins by affinity purification and selected UDP-galactofuranose (Galf) mutase (UGMA) for detailed characterization, because UGMA and UDP-Galf are unique to fungi and bacteria and absent in plants and animals. The interaction between CHY1 and UGMA was confirmed by yeast two-hybrid assays. Deletion of UGMA in F. graminearum resulted in significant defects in vegetative growth, reproduction, cell wall integrity, and pathogenicity. Infection with the ΔugmA mutant was restricted to the inoculated floret, and no vomitoxin was detected in kernels inoculated with the ΔugmA strain. Compared to the wild type, the ΔugmA mutant produced wide, highly branched hyphae with thick walls, as visualized by transmission electron microscopy. UGMA tagged with green fluorescent protein (GFP) mainly localized to the cytoplasm, consistent with the synthesis of Galf in the cytoplasm. The Δchy1 mutant was more sensitive, while the ΔugmA mutant was more tolerant, to cell wall-degrading enzymes. The growth of the ΔugmA mutant nearly ceased upon caspofungin treatment. More interestingly, nocodazole treatment of the ΔugmA strain attenuated its highly branched morphology, while caspofungin inhibited the degree of the twisted Δchy1 mycelia, indicating that CHY1 and UGMA probably have opposite effects on cell wall architecture. In conclusion, UGMA is an important pathogenic factor that is specific to fungi and bacteria and required for cell wall architecture, radial growth, and caspofungin tolerance, and it appears to be a promising target for antifungal agent development. IMPORTANCE The long-term use of chemical pesticides has had increasingly negative impacts on the ecological environment and human health. Low-toxicity, high-efficiency and environmentally friendly alternative pesticides are of great significance for maintaining the sustainable development of agriculture and human and environmental health. Using fungus- or microbe-specific genes as candidate targets provides a good foundation for the development of low-toxicity, environmentally friendly pesticides. In this study, we characterized a fungus- and bacterium-specific UDP-galactopyranose mutase gene, ugmA, that contributes to the synthesis of the cell wall component Galf and is required for vegetative growth, cell wall integrity, deoxynivalenol (DON) production, and pathogenicity in F. graminearum. The ugmA deletion mutant exhibited increased sensitivity to caspofungin. These results demonstrate the functional importance of UGMA in F. graminearum, and its absence from mammals and higher plants constitutes a considerable advantage as a low-toxicity target for the development of new anti-Fusarium agents.

"Fishcide" effect of the fungicide difenoconazole in freshwater fish (Labeo rohita): A multi-endpoint approach

Difenoconazole is widely used to protect crops, fruits, and vegetables. However, this fungicide can enter aquatic environments and cause harmful effects to non-target organisms and induce little-known biological disorders. Thus, aiming to expand our knowledge about the ecotoxicity of difenoconazole on freshwater ichthyofauna, we aimed to determine the median lethal concentration (LC₅₀) of difenoconazole and evaluate its possible impacts from different toxicity biomarkers, using freshwater fish Labeo rohita as a model system. Using the probit analysis method, the 96 h LC₅₀ value of difenoconazole in the fish was calculated as 4.5 mg L^-1. Posteriorly, fish were exposed to two sublethal concentrations (0.45 mg L^-1 1/10th and 0.9 mg L^-1 1/5th LC₅₀ value) for 21 days. A significant reduction of superoxide dismutase (SOD) and catalase (CAT) activity was noted in the gill, liver, and kidneys of fish compared to the control groups. The level of glutathione-S-transferase (GST) and lipid peroxidation (LPO) activity was higher in all vital tissues of difenoconazole-treated fish. Histological alterations in the gill include epithelial lifting, lamellar fusion, hypertrophy, and epithelial necrosis. At the same time, the liver showed pyknotic nucleus, vacuolation, cellular edema and tubular necrosis, shrinkage of glomeruli, vacuolation, and pyknotic nuclei in the kidney. DNA damage was increased significantly with tail formation based on the concentration and time-dependent manner. Therefore, our study confirms that the exposure of L. rohita to difenoconazole induces negative biological consequences and sheds light on the danger of this fungicide for freshwater fish species. We believe that studies like ours can support actions and strategies for the remediation/mitigation of aquatic pollution by difenoconazole and for the conservation of freshwater ichthyofauna.

Evaluation of three novel soil bacterial strains for efficient biodegradation of persistent boscalid fungicide: Kinetics and identification of microbial biodegradation intermediates

Boscalid, a new fungicide of anilide group, is intended to prevent and treat grey mould (Botrytis cinerea), primarily in vines and other fruit plants. In many regions, its long half-life in soil and water poses a serious environmental threat. Boscalid is reported to be toxic to a variety of aquatic organisms. One of the best ways to lessen the amount of boscalid that gets into surface and ground waters is to reduce its concentration in soil. Soil microbes are crucial for the degradation of organic pollutants including pesticides. The present study reports the assessment of three novel soil bacterial strains isolated from pesticide-contaminated soil of Crop research centre, Pantnagar, Uttarakhand, India, which possess boscalid degradation ability. Two of these bacterial isolates could degrade boscalid up to 85-95% within 36 h of incubation period under shaking conditions in the minimal medium. The growth pattern of degrading bacterial isolates was monitored by recording the optical density (OD) of bacterial suspension using an ultra violet (UV)-visible spectrophotometer, whereas the concentration of primary boscalid was recorded by High-Performance Liquid Chromatography (HPLC-UV). A linear relationship was observed between the bacterial growth and the decrease in the residual concentration of boscalid. The concentration of boscalid during incubation with different bacterial strains could be best predicted by a second-order polynomial relationship with time and OD of the suspension as independent variables. Three degradation intermediates of boscalid namely, N-(1,1'-biphenyl-2-yl)pyridine-3-carboxamide (C₁₈H₁₄N₂O, N-{[1,1'-biphenyl]-2-yl}-2-chloropyridine-3-carboxamide (C₁₈H₁₃N₂OCl), and N-{[4'-chloro-1,1'-biphenyl]-2-yl}-2-chloropyridine ({C₁₇H₁₁NCl₂}OH) were identified by the liquid chromatography-mass spectrometry (LC-MS) analysis of biodegraded samples. The biodegradation of boscalid through bacterial isolates seemed to be an economical and eco-friendly method for degrading a highly persistent boscalid fungicide.

Chronic toxic effects of isoflucypram on reproduction and intestinal energy metabolism in zebrafish (Danio rerio)

The intestine is a vital organ involved in chemical and nutrient uptake and biotransformation. Intestinal dysfunction can impair energy and material supply for reproduction. Isoflucypram, a new succinate dehydrogenase inhibitor fungicide, is highly toxic to aquatic systems. However, the chronic toxic effects of isoflucypram on intestinal differentiation in aquatic organisms remain unknown. In this study, zebrafish (F0, 4-month-old) were exposed to 0, 0.008, or 0.08 μM isoflucypram for 120 days. After 90 days of exposure, F0 generations of adult zebrafish were paired, and the corresponding F1 generation embryos were obtained and observed. After 120 days of exposure, the gut of F0 generation zebrafish was collected, and intestinal histopathology and mitochondrial morphology were analyzed. Exposure to 0.08 μM isoflucypram resulted in significant death, hatching delay, and malformation (blood clot clustering, pericardial edema, and microphthalmia) of F1 embryos and larvae. Exposure to isoflucypram caused irregular and swollen villi in the zebrafish gut, accompanied by alterations in the intestinal mitochondrial ultrastructure. In addition, the differentially expressed genes involved in mitochondrial energy metabolism were significantly enriched. Overall, our data suggest that chronic exposure to isoflucypram is associated with reproductive and intestinal dysfunction in adult zebrafish.

Effect of H3PO4-modified biochar on the fate of atrazine and remediation of bacterial community in atrazine-contaminated soil

The application of chemically modified biochar is a promising strategy for the remediation of contaminated (e.g., pesticides) soil. In this study, H₃PO₄ was used to modify peanut shell to improve the remediation performance of biochar. Surface area (980.19 m²/g), pore volume (0.12 cm³/g), and the functional groups (OH, CO, and phosphorus-containing groups) on the biochar were increased by H₃PO₄ treatment. The sorption experimental data were well fitted by Freundlich model, while the sorption affinity (K_f) of H₃PO₄ modified biochar (PBC) for atrazine was 128 times greater than that of the untreated biochar (BC) in the aquatic systems. The K_f values of PBC-amended soil to atrazine were increased by 13.57 times than that of single soil. The strong sorption of PBC on atrazine delayed the degradation of atrazine in soil, and the residual percentage of atrazine in soil and soil-PBC mixture were 4.90% and 71.44% at the end of 60-day incubation, with the degradation half-life increased from 13.3 to 121.6 d. The analysis of high-throughput sequencing results showed that atrazine reduced the diversity of soil microbial community, but the abundance of microorganisms with degradation function increased and became dominant species. The addition of PBC in soil accelerated the microbial remediation of atrazine stress, which may promote the soil nitrogen cycle. Therefore, amendment of atrazine contaminated soil with PBC can reduce the environmental risk of atrazine and benefit the soil microbial ecology.

Fluxapyroxad disrupt erythropoiesis in zebrafish (Danio rerio) embryos

Fluxapyroxad, a succinate dehydrogenase inhibitor (SDHI) fungicide, is commercialized worldwide to control a variety of fungal diseases. Growing evidence shows that fluxapyroxad is teratogenic to aquatic organisms. In this study, the influence of fluxapyroxad toward hematopoietic development was evaluated using zebrafish embryos which were exposed to fluxapyroxad (0.03 µM, 0.3 µM and 3 µM) from 3 h post fertilization (hpf) to 3 days post fertilization (dpf). Compared to the control groups, the hemoglobin was ectopic and decreased in response to fluxapyroxad treatment. The transcription levels of genes (hbbe1, hbbe2, and gata1a) involved in erythropoiesis were reduced after exposure to fluxapyroxad. In contrast, the distributions and expression of marker genes for myeloid lineage cells were unaffected by fluxapyroxad exposure. Our data suggested that fluxapyroxad might specifically affect erythropoiesis and hold great promise for the assessment of the toxicity of fluxapyroxad to aquatic organisms.

Hepatopancreas toxicity and immunotoxicity of a fungicide, pyraclostrobin, on common carp

Pyraclostrobin (PYR), a strobilurin fungicide, has been widely used to control fungal diseases, posing potential risk to aquatic organisms. However, the toxic effects of PYR to fish remained largely unknown. In this study, common carp (Cyprinus carpio L.) was exposed to environmentally relevant levels of PYR (0, 0.5 and 5.0 μg/L) for 30 days to assess its chronic toxicity and potential toxicity mechanism. The results showed that long-term exposure to PYR induced hepatopancreas damage as evident by increased in serum transaminase activities (AST and ALT). Moreover, PYR exposure remarkably enhanced the expressions of hsp70 and hsp90, decreased the levels of antioxidant enzymes and biomarkers and promoted the reactive oxygen species (H₂O₂ and O₂^-) and MDA contents in carp hepatopancreas. PYR exposure also upregulated apoptosis-related genes (bax, apaf-1, caspase-3 and caspase-9) and reduced anti-apoptosis gene bcl-2 in fish hepatopancreas. Moreover, PYR exposure altered the expressions of inflammatory cytokines (IL-1β, IL-6, TNF-α and TGF-β) in the serum and hepatopancreas and the level of NF-κB p65 in the hepatopancreas. Further research indicated that PYR exposure markedly changed the levels of immune parameters (LYZ, C3, IgM, ACP and AKP) in the serum and/or hepatopancreas, indicating that chronic PYR exposure also has immunotoxicity on fish. Additionally, we found that PYR exposure upregulated p38 and jnk MAPK transcription levels, suggesting that MAPK may be play important role in PYR-induced apoptosis and inflammatory response in the hepatopancreas of common carp. In summary, PYR exposure induced oxidative stress, triggered apoptosis, inflammatory and immune response in common carp, which can help to elucidate the possible toxicity mechanism of PYR in fish.

Repeated exposure of fluazinam fungicides affects gene expression profiles yet carries no costs on a nontarget pest

Fungicides are used to control pathogenic fungi of crop species, but they have also been shown to alter behavioral, life history and fitness related traits of nontarget insects. Here, we tested the fungicide effects on feeding behavior, survival and physiology of the nontarget pest insect, the Colorado potato beetle (CPB) (Leptinotarsa decemlineata). Feeding behavior was studied by a choice test of adult beetles, which were allowed to choose between a control and a fungicide (fluazinam) treated potato leaf. Larval survival was recorded after 24 and 72 h exposure to control and fungicide-treated leaves with 2 different concentrations. The adults did not show fungicide avoidance behavior. Similarly, survival of the larvae was not affected by the exposure to fungicides. Finally, to understand the effects of fungicides at the physiological level (gene expression), we tested whether the larval exposure to fungicide alter the expression of 5 metabolic pathway and stress associated genes. Highest concentration and 72-h exposure caused upregulation of 1 cytochrome P450 (CYP9Z14v2) and 1 insecticide resistance gene (Ldace1), whereas metabolic detoxification gene (Ugt1) was downregulated. At 24-h exposure, highest concentration caused downregulation of another common detoxification gene (Gs), while both exposure times to lowest concentration caused upregulation of the Hsp70 stress tolerance gene. Despite these overall effects, there was a considerable amount of variation among different families in the gene expression levels. Even though the behavioral effects of the fungicide treatments were minor, the expression level differences of the studied genes indicate changes on the metabolic detoxifications and stress-related pathways.

Fungicides and bees: a review of exposure and risk

Fungicides account for more than 35% of the global pesticide market and their use is predicted to increase in the future. While fungicides are commonly applied during bloom when bees are likely foraging on crops, whether real-world exposure to these chemicals - alone or in combination with other stressors - constitutes a threat to the health of bees is still the subject of great uncertainty. The first step in estimating the risks of exposure to fungicides for bees is to understand how and to what extent bees are exposed to these active ingredients. Here we review the current knowledge that exists about exposure to fungicides that bees experience in the field, and link quantitative data on exposure to acute and chronic risk of lethal endpoints for honey bees (Apis mellifera). From the 702 publications we screened, 76 studies contained quantitative data on residue detections in honey bee matrices, and a further 47 provided qualitative information about exposure for a range of bee taxa through various routes. We compiled data for 90 fungicides and metabolites that have been detected in honey, beebread, pollen, beeswax, and the bodies of honey bees. The risks posed to honey bees by fungicide residues was estimated through the EPA Risk Quotient (RQ) approach. Based on residue concentrations detected in honey and pollen/beebread, none of the reported fungicides exceeded the levels of concern (LOC) set by regulatory agencies for acute risk, while 3 and 12 fungicides exceeded the European Food Safety Authority (EFSA) chronic LOC for honey bees and wild bees, respectively. When considering exposure to all bees, fungicides of most concern include many broad-spectrum systemic fungicides, as well as the widely used broad-spectrum contact fungicide chlorothalonil. In addition to providing a detailed overview of the frequency and extent of fungicide residue detections in the bee environment, we identified important research gaps and suggest future directions to move towards a more comprehensive understanding and mitigation of the risks of exposure to fungicides for bees, including synergistic risks of co-exposure to fungicides and other pesticides or pathogens.

Using metabolomic profiling to inform use of surrogate species in ecological risk assessment practices

The U.S. EPA frequently uses avian or fish toxicity data to set protective standards for amphibians in ecological risk assessments. However, this approach does not always adequately represent aquatic-dwelling and terrestrial-phase amphibian exposure data. For instance, it is accepted that early life stage tests for fish are typically sensitive enough to protect larval amphibians, however, metamorphosis from tadpole to a terrestrial-phase adult relies on endocrine cues that are less prevalent in fish but essential for amphibian life stage transitions. These differences suggest that more robust approaches are needed to adequately elucidate the impacts of pesticide exposure in amphibians across critical life stages. Therefore, in the current study, methodology is presented that can be applied to link the perturbations in the metabolomic response of larval zebrafish (Danio rerio), a surrogate species frequently used in ecotoxicological studies, to those of African clawed frog (Xenopus laevis) tadpoles following exposure to three high-use pesticides, bifenthrin, chlorothalonil, or trifluralin. Generally, D. rerio exhibited greater metabolic perturbations in both number and magnitude across the pesticide exposures as opposed to X. laevis. This suggests that screening ecological risk assessment surrogate toxicity data would sufficiently protect amphibians at the single life stage studied but care needs to be taken to understand the suite of metabolic requirements of each developing species. Ultimately, methodology presented, and data gathered herein will help inform the applicability of metabolomic profiling in establishing the risk pesticide exposure poses to amphibians and potentially other non-target species.

On the behaviour of Atrazine removal from water using fabrics as anodes and cathodes

This study examines the degradation of atrazine (ATZ) with Pt-modified textile electrodes using an electrochemical method that is comparatively studied in two electrochemical cell configurations: cells with separated anodic and cathodic compartments (divided configuration); and without any separation (undivided configuration). The influence of the presence of chloride ions was studied. The best results were obtained when an undivided cell was used. The morphology and composition of the dispersed Pt coatings were analyzed using field emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray Analysis. The FESEM analyses confirmed that the textile surface was effectively modified by the electrocatalytic material. High performance liquid chromatography, gas chromatography mass spectrometry, and spectroscopic methods were used to follow the evolution of major oxidation products. Total organic carbon, chemical oxygen demand, and total nitrogen were used to evaluate the degradation efficiency of treated aqueous solutions. The experimental results obtained indicate that the efficiency of the electrochemical treatment was high with a low energy consumption when using electrodes based on textile materials, such as anodes or as cathodes (in particular, in electrolysis without compartment separation). All these can be produced at very competitive prices.

Pyraclostrobin Removal in Pilot-Scale Horizontal Subsurface Flow Constructed Wetlands and in Porous Media Filters

Pyraclostrobin is a fungicide extensively used for the control of various fungal diseases and is frequently detected in environmental samples. Natural systems, such as constructed wetlands (CWs) and gravity filters, are effective and environmentally friendly treatment systems, which can reduce or eliminate pesticides from the environment. The aim of this study was to investigate the capacity of two pilot-scale CWs (porous media: cobbles and fine gravel, planted with Phragmites australis) and six gravity filters (filling material: bauxite, carbonate gravel and zeolite) to remove pyraclostrobin from polluted water originating from spraying equipment rinsing sites. For this, experiments were conducted to test the performance of the above natural systems in removing this fungicide. The results showed that the mean percent pyraclostrobin removal efficiencies for cobbles and fine gravel CW units were 56.7% and 75.2%, respectively, and the mean percent removals for HRTs of 6 and 8 days were 68.7% and 62.8%, respectively. The mean removal efficiencies for the bauxite, carbonate gravel and zeolite filter units were 32.5%, 36.7% and 61.2%, respectively, and the mean percent removals for HRTs 2, 4 and 8 days were 39.9%, 43.4% and 44.1%, respectively. Regarding the feeding strategy, the mean removal values of pyraclostrobin in gravity filter units were 43.44% and 40.80% for continuous and batch feeding, respectively. Thus, these systems can be used in rural areas for the treatment of spraying equipment rinsing water.

Detection of Azoxystrobin Fungicide and Metabolite Azoxystrobin-Acid in Pregnant Women and Children, Estimation of Daily Intake, and Evaluation of Placental and Lactational Transfer in Mice

BACKGROUND

Azoxystrobin (AZ) is a broad-spectrum strobilurin fungicide that is used in agriculture and was recently added to mold- and mildew-resistant wallboards. AZ was found to have toxic effects in animals at embryonic stages and was listed as a frontline target for biomonitoring in children.

OBJECTIVES

This study investigated exposure to AZ in pregnant women and young children, whether AZ could be transferred from an exposed mother to offspring, and whether AZ or one of its primary metabolites, AZ-acid, was neurotoxic in vitro.

METHODS

We quantified AZ-acid, a sensitive indicator of AZ exposure, in urine samples collected from 8 pregnant women (12 urine samples) and 67 children (40-84 months old; 96 urine samples) with high-resolution mass spectrometry. Gestational and lactational transfer was assessed in C57Bl/6 mice. Neurotoxicity of AZ and AZ-acid was investigated in vitro with mouse cortical neuron cultures.

RESULTS

AZ-acid was present above the limit of quantification (0.01 ng/mL) in 100% of the urine samples from pregnant women and in 70% of the urine samples from children, with median concentration of 0.10 and 0.07 ng/mL, and maximal concentration of 2.70 and 6.32 ng/mL, respectively. Studies in mice revealed that AZ transferred from the mother to offspring during gestation by crossing the placenta and entered the developing brain. AZ was also transferred to offspring via lactation. High levels of cytotoxicity were observed in embryonic mouse cortical neurons at concentrations that modeled environmentally relevant exposures.

DISCUSSION

Our study suggested that pregnant women and children were exposed to AZ, and at least 10% of the children (2 out of 20 that were evaluated at two ages) showed evidence of chronic exposure. Future studies are warranted to evaluate whether chronic AZ exposure affects human health and development. https://doi.org/10.1289/EHP9808.

Effects of embryonic exposure to fluxapyroxad on zebrafish (Danio rerio) ocular development

Fluxapyroxad (FLU) is a succinate dehydrogenase inhibitor that protects crops from fungal diseases, however, it has been identified as toxicants to aquatic organisms. The objective of this study is to investigate the potential toxicity and underlying mechanisms of FLU on aquatic organisms. Herein, by using zebrafish embryos as a model organism, we demonstrated that FLU can cause microphthalmia in zebrafish embryos. The cell density in ganglion cell layer (GCL) is increased after exposure. Compared with the control, differentiation of the cells in ganglion cell layer, inner nuclear layer (INL), and outer nuclear layer (ONL) were severely disrupted in response to FLU treatment. The data show clear evidence that FLU exhibits development toxicity to zebrafish embryos by inducing retinal cell apoptosis, which causes microphthalmia. Our study provides comprehensive understanding to the underlying mechanism of FLU toxicity.

Interaction of Insecticides and Fungicides in Bees

Honeybees and wild bees are among the most important pollinators of both wild and cultivated landscapes. In recent years, however, a significant decline in these pollinators has been recorded. This decrease can have many causes including the heavy use of biocidal plant protection products in agriculture. The most frequent residues in bee products originate from fungicides, while neonicotinoids and, to a lesser extent, pyrethroids are among the most popular insecticides detected in bee products. There is abundant evidence of toxic side effects on honeybees and wild bees produced by neonicotinoids, but only few studies have investigated side effects of fungicides, because they are generally regarded as not being harmful for bees. In the field, a variety of substances are taken up by bees including mixtures of insecticides and fungicides, and their combinations can be lethal for these pollinators, depending on the specific group of insecticide or fungicide. This review discusses the different combinations of major insecticide and fungicide classes and their effects on honeybees and wild bees. Fungicides inhibiting the sterol biosynthesis pathway can strongly increase the toxicity of neonicotinoids and pyrethroids. Other fungicides, in contrast, do not appear to enhance toxicity when combined with neonicotinoid or pyrethroid insecticides. But the knowledge on possible interactions of fungicides not inhibiting the sterol biosynthesis pathway and insecticides is poor, particularly in wild bees, emphasizing the need for further studies on possible effects of insecticide-fungicide interactions in bees.

Multiple pesticides occurrence, fate, and environmental risk assessment in a small horticultural stream of Argentina

Peri-urban horticulture is crucial to local populations, but a global paucity of information exists regarding the contamination of the associated waterways because of this activity. The aim of this study was to assess pesticide pollution of surface water, suspended particulate matter and bottom sediments from the Carnaval Creek Basin (La Plata, Buenos Aires, Argentina) - a representative system of waterways surrounded by horticultural production - by over 40 selected herbicides, insecticides, and fungicides by gas-chromatography-time-of-flight mass spectrometry and ultraperformance liquid chromatography tandem mass spectrometry. Six sampling campaigns were conducted biannually from 2015 to 2017. Glyphosate and (aminomethyl)phosphonic acid (AMPA), surprisingly, were the most frequently detected pesticides, in concentrations comparable to those reported in areas with genetically modified extensive crops (maximum in water, 20.04 and 4.86 μg·L^-1; in sediment, 1146.5 and 4032.7 μg·kg_dw^-1, respectively). The insecticides chlorpyrifos, cypermethrin and λ-cyhalothrin were detected in more than 30% of the samples. The concentrations tended to greatly exceed those previously reported - by up to more than 800 times for chlorpyrifos in water (maximum 2.645 μg·L^-1) and more than 400 times for lambda-cyhalothrin in sediments (maximum 2607.7 μg·kg_dw^-1). The total pesticide concentration in surface water was found to be influenced by precipitation regimes but was independent of the season of the year, with precipitations of more than 140 mm diluting the pesticide concentrations to levels below detection limits. An environmental risk assessment performed with the pesticide concentrations of pesticides in surface water revealed that the surrounding horticultural activity posed a high risk for aquatic biota, with 30% of the samples exceeding the threshold value by more than a thousand times. We conclude that pesticides from horticultural use are a major threat to small streams and their biodiversity. This work provides valuable information that is scarce regarding the impact on watercourses exclusively as a consequence of horticulture.

SDHI Fungicide Toxicity and Associated Adverse Outcome Pathways: What Can Zebrafish Tell Us?

Succinate dehydrogenase inhibitor (SDHI) fungicides are increasingly used in agriculture to combat molds and fungi, two major threats to both food supply and public health. However, the essential requirement for the succinate dehydrogenase (SDH) complex—the molecular target of SDHIs—in energy metabolism for almost all extant eukaryotes and the lack of species specificity of these fungicides raise concerns about their toxicity toward off-target organisms and, more generally, toward the environment. Herein we review the current knowledge on the toxicity toward zebrafish (Brachydanio rerio) of nine commonly used SDHI fungicides: bixafen, boscalid, fluxapyroxad, flutolanil, isoflucypram, isopyrazam, penthiopyrad, sedaxane, and thifluzamide. The results indicate that these SDHIs cause multiple adverse effects in embryos, larvae/juveniles, and/or adults, sometimes at developmentally relevant concentrations. Adverse effects include developmental toxicity, cardiovascular abnormalities, liver and kidney damage, oxidative stress, energy deficits, changes in metabolism, microcephaly, axon growth defects, apoptosis, and transcriptome changes, suggesting that glycometabolism deficit, oxidative stress, and apoptosis are critical in the toxicity of most of these SDHIs. However, other adverse outcome pathways, possibly involving unsuspected molecular targets, are also suggested. Lastly, we note that because of their recent arrival on the market, the number of studies addressing the toxicity of these compounds is still scant, emphasizing the need to further investigate the toxicity of all SDHIs currently used and to identify their adverse effects and associated modes of action, both alone and in combination with other pesticides.

Individual performances and biochemical pathways as altered by field-realistic exposures of current-use fungicides and their mixtures in a non-target species, Gammarus fossarum

Persistent fungicides, which are widely applied to agricultural soils to protect crops, are frequently detected in freshwaters because of hydraulic transfer, possibly resulting in unintentional adverse effects on wildlife. However, the ecotoxicity of fungicides in aquatic species remains scarcely assessed at environmentally relevant concentrations, and there is scant information available on their combined effects. This study aims at investigating multi-level changes elicited by two currently used fungicides, boscalid and tebuconazole, in the amphipod Gammarus fossarum. In microcosms, gammarids were exposed for 72 h to fungicides tested individually or in binary mixture at 0.01, 0.1 and 1.0 μg/L to monitor individual performances (locomotion, respiration and amplexus formation) and biochemical parameters (involved in energy metabolism, growth, moulting and cell stress). This range of exposure concentrations was field-realistic and largely lower than local environmental quality standards for the protection of aquatic wildlife. Overall, results showed that single and combined exposures altered the mobility and respiratory activity of individuals. At the cellular level, boscalid inhibited energy-based biomarkers whereas tebuconazole led to cytotoxicity associated with reduced antioxidant defences. In binary mixtures, the biochemical responses were mainly driven by the presence of boscalid. Multi-variable analyses, integrating individual alterations and cellular impairments alike, confirmed the relevance of the multi-level approach in forecasting the toxicity of fungicides and their mixtures towards other aquatic species. This study demonstrates dose-related sublethal effects of fungicides on multiple functional traits in an ecosystem engineer under realistic exposure scenarios, highlighting the harmful signs of these toxicants. Such sublethal alterations could thus constitute reliable tools for the early diagnosis of the organisms' health and the ecological status of agriculturally impacted hydrosystems.

Fucoidan ameliorates acute and sub-chronic in vivo toxicity of the fungicide cholorothalonil in Oreochromis niloticus (Nile tilapia)

Fucoidans are sulfated glycans from marine algae that have both anti-cancer and anti-microbial properties. Chlorothalonil is a fungicide and insecticide commonly used in agriculture. Chlorothalonil is relatively toxic to fish and can potentially affect the aquaculture practices. In this study, we determined whether fucoidan administration would offer any protection from acute and subchronic toxicity of chlorothalonil on Nile tilapia. First, we tested the effect of chlorothalonil (20 to 140 μg/L, water-applied) on Nile tilapia in an acute exposure (six days). Survival analysis was performed, together with assessment of histopathology, oxidative stress (i.e., antioxidant status, hydrogen peroxide levels, malondialdehyde and nitric oxide levels) and immunohistochemistry to measure indicators of hepatic damage (i.e., caspase 3, p53, mini-chromosome maintenance proteins (MCM), and glutathione peroxidase). Chlorothalonil induced mild to severe histopathological alterations that were dose-dependent in various tissues of Nile tilapia. Chlorothalonil also induced oxidative stress as indicated by elevated biochemical markers. The highest recorded mortalities were associated with p53 expression. Additional feeding experiments were conducted with fucoidan (8 g/kg diet), following acute (40 μg/L for seven days) and sub-chronic (20 μg/L for six weeks) chlorothalonil application in Nile tilapia. Many of these same biochemical biomarkers of stress, oxidative damage response, and tissue pathology (evidence for hepatic neoplasm) were ameliorated by fucoidan, suggesting a protective effect of the compound. Agrochemicals are ubiquitous on a global scale, and the use of fucoidan as a feed additive may be beneficial for protecting aquatic animal health and aquaculture species from the impacts of chemical run-off.

Environmental and anthropogenic drivers of contaminants in agricultural watersheds with implications for land management

If not managed properly, modern agricultural practices can alter surface and groundwater quality and drinking water resources resulting in potential negative effects on aquatic and terrestrial ecosystems. Exposure to agriculturally derived contaminant mixtures has the potential to alter habitat quality and negatively affect fish and other aquatic organisms. Implementation of conservation practices focused on improving water quality continues to increase particularly in agricultural landscapes throughout the United States. The goal of this study was to determine the consequences of land management actions on the primary drivers of contaminant mixtures in five agricultural watersheds in the Chesapeake Bay, the largest watershed of the Atlantic Seaboard in North America where fish health issues have been documented for two decades. Surface water was collected and analyzed for 301 organic contaminants to determine the benefits of implemented best management practices (BMPs) designed to reduce nutrients and sediment to streams in also reducing contaminants in surface waters. Of the contaminants measured, herbicides (atrazine, metolachlor), phytoestrogens (formononetin, genistein, equol), cholesterol and total estrogenicity (indicator of estrogenic response) were detected frequently enough to statistically compare to seasonal flow effects, landscape variables and BMP intensity. Contaminant concentrations were often positively correlated with seasonal stream flow, although the magnitude of this effect varied by contaminant across seasons and sites. Land-use and other less utilized landscape variables including biosolids, manure and pesticide application and percent phytoestrogen producing crops were inversely related with site-average contaminant concentrations. Increased BMP intensity was negatively related to contaminant concentrations indicating potential co-benefits of BMPs for contaminant reduction in the studied watersheds. The information gained from this study will help prioritize ecologically relevant contaminant mixtures for monitoring and contributes to understanding the benefits of BMPs on improving surface water quality to better manage living resources in agricultural landscapes inside and outside the Chesapeake Bay watershed.

A comprehensive review of strobilurin fungicide toxicity in aquatic species: Emphasis on mode of action from the zebrafish model

Strobilurins are popular fungicides used in agriculture on a global scale. Due to their widespread use as agrochemicals, they can enter aquatic environments at concentrations that can elicit adverse effects in organisms. This review synthesizes the current state of knowledge regarding the toxic effects of strobilurin fungicides on aquatic species, including algal species, Daphnia magna, and fish species, to determine risk to aquatic organisms and ecosystems. Data show that the toxicities of strobilurins vary widely across aquatic species. Strobilurins bind cytochrome bc1 in mitochondrial complex III in fungi, and as such, research in aquatic species has focused on mitochondria-related endpoints following exposures to strobilurins. In fish, studies into the activities of mitochondrial complexes and the expression of genes involved in the electron transfer chain have been conducted, converging on the theme that mitochondrial complexes and their enzymes are impaired by strobilurins. In general, the order of toxicity of strobilurins for fish species are pyraoxystrobin > pyraclostrobin ≈ trifloxystrobin > picoxystrobin > kresoxim-methyl > fluoxastrobin > azoxystrobin. In addition to mitochondrial toxicity, studies also report genotoxicity, immunotoxicity, cardiotoxicity, neurotoxicity, and endocrine disruption, and each of these events can potentially impact whole organism-level processes such as development, reproduction, and behavior. Screening data from the US Environmental Protection Agency ToxCast database supports the hypothesis that these fungicides may act as endocrine disruptors, and high throughput data suggest estrogen receptor alpha and thyroid hormone receptor beta can be activated by some strobilurins. It is recommended that studies investigate the potential for endocrine disruption by strobilurins more thoroughly in aquatic species. Based on molecular, physiological, and developmental outcomes, a proposed adverse outcome pathway is presented with complex III inhibition in the electron transfer chain as a molecular initiating event. This review comprehensively addresses sub-lethal toxicity mechanisms of strobilurin fungicides, important as the detection of strobilurins in aquatic environments suggests exposure risks in wildlife.

Environmentally relevant concentrations of boscalid exposure affects the neurobehavioral response of zebrafish by disrupting visual and nervous systems

Boscalid is a persistent fungicide that is frequently detected in surface waters and may be neurotoxic to aquatic organisms. Herein, we evaluated the effects of environmentally relevant boscalid concentrations to zebrafish to explore its potentially neurotoxic mechanisms of effect. Behavioral responses (swimming, phototaxis, and predation), histopathology, transcriptomics, biochemical parameter analysis and gene expression of larval and adult zebrafish following boscalid treatment were assessed. We found that boscalid significantly inhibited the locomotor ability and phototactic response of larvae after an 8-d exposure, and altered the locomotor activity, predation trajectories and ability in adults after a 21-d exposure. It was noted that predation rates of zebrafish were significantly decreased by 30% and 100% after exposure to 0.1 and 1.0 mg/L boscalid, respectively. Adverse alterations in the cell differentiation of eyes and brain injury were also observed in both larvae and adults following boscalid exposure. The expression of genes related to neurodevelopment, neurotransmission, eye development, and visual function, in conjunction with RNA-Seq results, indicated that boscalid may impair visual phototransduction and nervous system processes in larval zebrafish. Conclusively, boscalid exposure may affect the neurobehavioral response of zebrafish by impairing proper visual and nervous system function.

Molecular mechanisms of developmental toxicities of azoxystrobin and pyraclostrobin toward zebrafish (Danio rerio) embryos: Visualization of abnormal development using two transgenic lines

Azoxystrobin (AZ) and pyraclostrobin (PY) are strobilurin fungicides that inhibit fungal mitochondrial respiration. In this study, a representative model, zebrafish (Danio rerio), was used as a test species for acute and developmental toxicity. Survival and malformation rates were observed only PY-treated embryos, with an LC₅₀ value of 77.75 ppb accompanied by a dramatic decrease in hatching rate, while AZ did not show great mortality. Morphological changes were observed in PY-treated embryos with the occurrence of pericadial edema at 25 ppb. A delay in growth was observed after treatment with pyraclostrobin at 50 ppb. Use of genetically engineered Tg(cmlc:EGFP) allowed fluorescence observation during heart development. PY interfered with normal heart development via upregulation of the nppa gene responsible for the expression of natriuretic peptides. Heart function was dramatically reduced as indicated by reduced heart rates. Increased expression of the nppa gene was also seen in AZ-treated embryos. The expression level of cyp24a1 was also up-regulated, while ugt1a1 and sult1st6 were down-regulated after treatment of zebrafish embryos with AZ or PY. Overall, strobilurin fungicides might inhibit normal heart formation and function within the range of concentrations tested.

Occurrence of pesticides in waters from the largest sugar cane plantation region in the world

In this study, a multi-residue method was used to analyze 13 pesticides and 1 degradation product in surface and groundwater in the region with the largest sugar cane production in the world. The potential effects of individual pesticides and their mixtures, for aquatic life and human consumption, were evaluated. For the surface water, 2-hydroxy atrazine, diuron, carbendazim, tebuthiuron, and hexazinone were the most frequently detected (100, 94, 93, 92, and 91%, respectively). Imidacloprid (2579 ng L^-1), carbendazim (1114 ng L^-1), ametryn (1101 ng L^-1), and tebuthiuron (1080 ng L^-1) were found at the highest concentrations. For groundwater, tebuthiuron was the only quantified pesticide (107 ng L^-1). Ametryn, atrazine, diuron, hexazinone, carbofuran, imidacloprid, malathion, carbendazim, and their mixtures presented risk for the aquatic life. No risk was observed for the pesticides analyzed in this work, alone or in their mixtures for human consumption.

Screening of potential oestrogen receptor α agonists in pesticides via in silico, in vitro and in vivo methods

In modern agricultural management, the use of pesticides is indispensable. Due to their massive use worldwide, pesticides represent a latent risk to both humans and the environment. In the present study, 1056 frequently used pesticides were screened for oestrogen receptor (ER) agonistic activity by using in silico methods. We found that 72 and 47 pesticides potentially have ER agonistic activity by the machine learning methods random forest (RF) and deep neural network (DNN), respectively. Among endocrine-disrupting chemicals (EDCs), 14 have been reported as EDCs or ER agonists by previous studies. We selected 3 reported and 7 previously unreported pesticides from 76 potential ER agonists to further assess ERα agonistic activity. All 10 selected pesticides exhibited ERα agonistic activity in human cells or zebrafish. In the dual-luciferase reporter gene assays, six pesticides exhibited ERα agonistic activity. Additionally, nine pesticides could induce mRNA expression of the pS2 and NRF1 genes in MCF-7 cells, and seven pesticides could induce mRNA expression of the vtg1 and vtg2 genes in zebrafish. Importantly, the remaining 48 out of 76 potential ER agonists, none of which have previously been reported to have endocrine-disrupting effects or oestrogenic activity, should be of great concern. Our screening results can inform environmental protection goals and play an important role in environmental protection and early warnings to human health.

Pesticides and their degradates in groundwater reflect past use and current management strategies, Long Island, New York, USA

Long Island, New York, has a mix of urban/suburban to agricultural/horticultural land use and nearly 3 million residents that rely on a sole-source aquifer for drinking water. The analysis of shallow groundwater (<40 m below land surface) collected from 54 monitoring wells across Long Island detected 53 pesticides or pesticide degradates. Maximum concentrations for individual pesticides or pesticide degradates ranged from 3 to 368,000 ng/L. The highest concentrations and most frequent pesticide detections occurred in samples collected from the pesticide management (PM) network, set in an agricultural/horticultural area in eastern Long Island with coordinated pesticide management by state and local agencies. The other two networks (Suffolk and Nassau/Queens) were set in suburban and urban areas, respectively, and had less frequent detections and lower pesticide concentrations than the PM network. Pesticide detections and concentration patterns (herbicide, insecticide, or fungicide) differed among the three networks revealing broad differences in land use. The predominance of fungicides metalaxyl, 1H-1,2,4-triazole (propiconazole/myclobutanil degradate), and 4-hydroxychlorothalonil (HCTL, chlorothalonil degradate) in samples from the PM network reflects their intensive use in agricultural settings. Total fungicide concentrations in the PM network ranged from <10 to >300,000 ng/L. The widespread detection of imidacloprid and triazine herbicides, simazine and atrazine, reveal a mixture of current and past use pesticides across the Long Island region. Low concentrations (<200 ng/L) of the triazines in the Suffolk and Nassau/Queens networks may reflect a change in land use and application. Acetanilide herbicides and aldicarb have been discontinued for 20 and 40 years, respectively, yet the concentrations of their degradates were among the highest observed in this study. Acetanilide (total concentrations up to 10,000 ng/L) and aldicarb degradates (up to 270 ng/L) are present in the PM network at much lower concentrations than previous Long Island studies and reflect changes in agricultural practices and pesticide management.

Exposure to Boscalid Induces Reproductive Toxicity of Zebrafish by Gender-Specific Alterations in Steroidogenesis

Boscalid is a succinate dehydrogenase inhibitor fungicide and is frequently detected in surface water. Due to the frequent detection of boscalid, we evaluated its impact on the reproduction of adult zebrafish following a 21 d exposure to 0, 0.01, 0.1, and 1.0 mg/L. Following exposure to boscalid, the fertility of female zebrafish and fertilization rate of spawning eggs were reduced in a concentration-dependent manner up to a respective 87% and 20% in the highest concentration. A significant 16% reduction in the percentage of late vitellogenic oocytes was noted in ovaries, and a significant 74% reduction in the percentage of spermatids in testis was also observed after treatment with 1.0 mg/L. 17β-Estradiol (E2) concentrations decreased significantly in females (34% decrease) but significantly increased in males (15% increase) following 1.0 mg/L boscalid treatment. The expression of genes (such as era, er2b, cyp19a, and cyp19b) related to the hypothalamus-pituitary-gonad-liver (HPGL) axis was significantly altered and positively correlated with E2 concentrations in female and male zebrafish (p < 0.05). Molecular docking results revealed that the binding modes between boscalid and target proteins (ER and CYP19) of zebrafish were similar to that of the reference compounds and the target proteins. The binding energies indicate that boscalid may have a weak estrogen-like binding effect or CYP19 inhibition, potentially altering the HPGL axis, thereby reducing E2 concentrations and fecundity in females. In contrast, boscalid caused significant induction of E2 steroidogenesis and subsequent feminization of gonads in males, indicating gender-specific adverse outcome pathways.

Evaluation of boscalid toxicity on Daphnia magna by using antioxidant enzyme activities, the expression of genes related to antioxidant and detoxification systems, and life-history parameters

Boscalid is a succinate dehydrogenase inhibitor fungicide commonly used to control a range of plant pathogens. Although it is one of the most common fungicides in the aquatic environment, the potential adverse effects of boscalid on freshwater invertebrates still remain unclear. This study aimed to evaluate the toxicity of boscalid on Daphnia magna (D. magna) and provide new information to assess the eco-toxicity of the boscalid on aquatic invertebrates. The effects of boscalid on malondialdehyde (MDA) level, activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the mRNA level of genes associated with antioxidant system (sod, cat, and gst) and detoxification (cytochrome P450 4 (cyp4) and nuclear respiratory factor 1 (nrf1)) were determined after 48 h treatment. The effect of boscalid on reproduction and development of D. magna was evaluated by a 21-d-chronic toxicity test. Boscalid dose-dependently altered activities of SOD, CAT, and GST and led to lipid peroxidation during acute exposure in D. magna. Exposure to 5 and 10 mg/L boscalid also significantly decreased gene expression of sod, gst, cyp4 and nrf1 but increased cat gene expression. Furthermore, chronic toxicity results showed that exposure to boscalid decreased molting frequency, number of neonates per Daphnia, and the number of broods per female as compared to the control groups. The above results indicated that boscalid had significant negative impacts on D. magna, and information present here helps to evaluate the eco-toxicity caused by boscalid on aquatic invertebrates.

Sampling rates for passive samplers exposed to a field-relevant peak of 42 organic pesticides

Pesticide concentrations in agricultural streams are often characterised by a low level of baseline exposure and episodic peak concentrations associated with heavy rainfall events. Traditional sampling methods such as grab sampling, which are still largely used in governmental monitoring, typically miss peak concentrations. Passive sampling represents a cost-efficient alternative but requires the additional determination of sampling rates to calculate time-weighted average (TWA) water concentrations from the accumulated pesticide mass in the sampler. To date, sampling rates have largely been determined in experiments with constant exposure, which does not necessarily reflect field situations. Using Empore styrene-divinylbenzene (SDB) passive sampler disks mounted in metal holders, we determined sampling rates for 42 organic pesticides, of which 27 sampling rates were lacking before. The SDB disks were in an artificial channel system exposed to a field-relevant pesticide peak. We used an open-source algorithm to estimate coefficients of equations for the accumulated pesticide mass in disks and to determine exposure time-dependent sampling rates. These sampling rates ranged from 0.02 to 0.98 L d^-1 and corresponded to those from previous studies determined with constant exposure. The prediction of sampling rates using compound properties was unreliable. Hence, experiments are required to determine reliable sampling rates. We discuss the use of passive sampling to estimate peak concentrations. Overall, our study provides sampling rates and computer code to determine these under peak exposure designs and suggests that passive sampling is suitable to estimate peak pesticide concentrations in field studies.

QSAR models for the acute toxicity of 1,2,4-triazole fungicides to zebrafish (Danio rerio) embryos

In recent decades, the 1,2,4-triazole fungicides are widely used for crop diseases control, and their toxicity to wild lives and pollution to ecosystem have attracted more and more attention. However, how to quickly and efficiently evaluate the toxicity of these compounds to environmental organisms is still a challenge. In silico method, such like Quantitative Structure-Activity Relationship (QSAR), provides a good alternative to evaluate the environmental toxicity of a large number of chemicals. At the present study, the acute toxicity of 23 1,2,4-triazole fungicides to zebrafish (Danio rerio) embryos was firstly tested, and the LC₅₀ (median lethal concentration) values were used as the bio-activity endpoint to conduct QSAR modelling for these triazoles. After the comparative study of several QSAR models, the 2D-QSAR model was finally constructed using the stepwise multiple linear regression algorithm combining with two physicochemical parameters (logD and μ), an electronic parameter (Q_N1) and a topological parameter (X^vPC₄). The optimal model could be mathematically described as following: pLC₅₀ = -7.24-0.30X^vPC₄ + 0.76logD - 26.15Q_N1 - 0.08μ. The internal validation by leave-one-out (LOO) cross-validation showed that the R²_adj (adjusted noncross-validation squared correlation coefficient), Q² (cross-validation correlation coefficient) and RMSD (root-mean-square error) was 0.88, 0.84 and 0.17, respectively. The external validation indicated the model had a robust predictability with the q² (predictive squared correlation coefficient) of 0.90 when eliminated tricyclazole. The present study provided a potential tool for predicting the acute toxicity of new 1,2,4-triazole fungicides which contained an independent triazole ring group in their molecules to zebrafish embryos, and also provided a reference for the development of more environmentally-friendly 1,2,4-triazole pesticides in the future.

Exposure to pyrimethanil induces developmental toxicity and cardiotoxicity in zebrafish

Pyrimethanil is a broad-spectrum fungicide commonly used in the prevention and treatment of Botrytis cinerea. However, little information is available in the literature to show the toxicity of Pyrimethanil to cardiac development. In this study, we used an experimental animal model to explore the developmental and cardiac toxicity of Pyrimethanil in aquatic vertebrates; we exposed zebrafish embryos to Pyrimethanil at concentrations of 2, 4, and 6 mg/L from 5.5 to 72 h post fertilisation. We found that Pyrimethanil caused a decrease in the hatching rate, heart rate, and survival rate of zebrafish embryos. Pyrimethanil exposure also resulted in pericardial and yolk sac edema, spinal deformity, and heart loop failure. Moreover, Pyrimethanil increased reactive oxygen stress levels and heightened the activity of superoxide dismutase and catalase. Alterations were induced in the transcription of apoptosis-related genes (p53, Bax, Bcl2, Casp 9, and Casp6l1) and heart development-related genes (Tbx2b, Gata4, Myh6, Vmhc, Nppa, Bmp2b, Bpm 4, and Bpm 10). Our data showed that the activation of Wnt signalling by BML-284 could partially rescue the malformed phenotype caused by Pyrimethanil. Our results provide new evidence for Pyrimethanil's toxicity and the danger of its residues in the environment and agricultural products.

Pesticides in aquatic environments and their removal by adsorption methods

Although pesticides are widely used in agriculture, industry and households, they pose a risk to human health and ecosystems. Based on target organisms, the main types of pesticides are herbicides, insecticides and fungicides, of which herbicides accounted for 46% of the total pesticide usage worldwide. The movement of pesticides into water bodies occurs through run-off, spray drift, leaching, and sub-surface drainage, all of which have negative impacts on aquatic environments and humans. We sought to define the critical factors affecting the fluxes of contaminants into receiving waters. We also aimed to specify the feasibility of using sorbents to remove pesticides from waterways. In Karun River in Iran (1.21 × 10⁵ ng/L), pesticide concentrations are above regulatory limits. The concentration of pesticides in fish can reach 26.1 × 10³ μg/kg, specifically methoxychlor herbicide in Perca fluviatilis in Lithuania. During the last years, research has focused on elimination of organic pollutants, such as pesticides, from aqueous solution. Pesticide adsorption onto low-cost materials can effectively remediate contaminated waters. In particular, nanoparticle adsorbents and carbon-based adsorbents exhibit high performance (nearly 100%) in removing pesticides from water bodies.

Photolysis and photo-induced toxicity of pyraclostrobin to Vibrio fischeri: Pathway and toxic mechanism

Pyraclostrobin is a fungicide used widely across the world. However, its photolysis pathway and toxic mechanism is unclear. In this study, photolysis and photo-induced toxicity of pyraclostrobin to Vibrio fischeri were determined. The results showed that direct photolysis dominated the degradation of pyraclostrobin. Gas Chromatography-Mass spectrometry and quantum chemical calculation revealed that the pyraclostrobin was firstly photo-degraded into Methyl N-phenyl-carbamate and 1-(4-chlorophenyl)-3-hydroxy-1H-pyrzole, synthetic intermediates of pyraclostrobin, then into aniline, benzoquinone and acids. Toxicity assay showed that bioluminescent inhibition rate to V. fischeri fluctuated with radiation/illumination time and the toxicity curve can be classified into three phases (Phase I: 0-10 min, incline; Phase II: 10-60 min, decline; Phase III: 60-120 min, incline). The up-and-down curve indicates the change of parent compound during the photolysis. Simulation of molecular docking showed that the CDOCKER interaction energy of pyraclostrobin (-44.71) lower than other intermediate products (>-30.00), indicating that the parent compound is more toxic than its intermediates. An increased toxicity observed in the toxicity curve was attributed to the generation of benzoquinone with log1/EC₅₀ of 6.73, which can greatly change structure of target luciferase in Vibrio fischeri. In addition, the addition of radical scavengers can inhibit the bioluminescence of the tested solutions, indicating the involvement of radicals in the transformation of intermediates. This paper reveals that one of photochemical transformation products of pyraclostrobin can cause more toxic than its parent compound to bacteria. Environmental risk assessment should consider not only the parent compound, but also its metabolites.

Herbicide Exposure and Toxicity to Aquatic Primary Producers

The aim of the present review was to give an overview of the current state of science concerning herbicide exposure and toxicity to aquatic primary producers. To this end we assessed the open literature, revealing the widespread presence of (mixtures of) herbicides, inevitably leading to the exposure of non-target primary producers. Yet, herbicide concentrations show strong temporal and spatial variations. Concerning herbicide toxicity, it was concluded that the most sensitive as well as the least sensitive species differed per herbicide and that the observed effect concentrations for some herbicides were rather independent from the exposure time. More extensive ecotoxicity testing is required, especially considering macrophytes and marine herbicide toxicity. Hence, it was concluded that the largest knowledge gap concerns the effects of sediment-associated herbicides on primary producers in the marine/estuarine environment. Generally, there is no actual risk of waterborne herbicides to aquatic primary producers. Still, median concentrations of atrazine and especially of diuron measured in China, the USA and Europe represented moderate risks for primary producers. Maximum concentrations due to misuse and accidents may even cause the exceedance of almost 60% of the effect concentrations plotted in SSDs. Using bioassays to determine the effect of contaminated water and sediment and to identify the herbicides of concern is a promising addition to chemical analysis, especially for the photosynthesis-inhibiting herbicides using photosynthesis as endpoint in the bioassays. This review concluded that to come to a reliable herbicide hazard and risk assessment, an extensive catch-up must be made concerning macrophytes, the marine environment and especially sediment as overlooked and understudied environmental compartments.

Pesticides in Surface Waters in Argentina Monitored Using Polar Organic Chemical Integrative Samplers

Polar Organic Chemical Integrative Samplers (POCIS) were deployed in two watersheds in Córdoba province and one watershed in Buenos Aires province in Argentina. The fungicides, tebuconazole, carbendazim and azoxystrobin, and the herbicides, atrazine, dicamba and 2,4-D were detected in POCIS deployed in each of the three watersheds. Estimated time weighted average concentrations of atrazine were greater than 2 µg/L at the outflow of Brava Lake in Buenos Aires province, and this concentration exceeds the Canadian water quality guideline for protection of aquatic life. The concentrations of all other pesticides were less than 400 ng/L. The distribution of pesticides detected in surface waters indicated that the sources were runoff from agricultural and urban lands and discharges from wastewater treatment plants.

Characterization of boscalid-induced oxidative stress and neurodevelopmental toxicity in zebrafish embryos

Boscalid is a widely used fungicide in agriculture and has been frequently detected in both environments and agricultural products. However, evidence on the neurotoxic effect of boscalid is scarce. In this study, zebrafish served as an animal model to investigate the toxic effects and mechanisms of boscalid on aquatic vertebrates or higher animals. And we unravelled that boscalid induced developmental defects associated with oxidative stress. Developmental defects, including head deformity, hypopigmentation, decreased number of newborn neurons, structural defects around the ventricle, enlarged intercellular space in the brain, and nuclear concentration, were observed in zebrafish embryos after boscalid exposure at 48 hpf. Interestingly, we found that boscalid might directly induce oxidative stress and alter the activity of ATPase, which in turn disrupted the expression of genes involved in neurodevelopment and transmitter-transmitting signalings and melanocyte differentiation and melanin synthesis signalings. Ultimately, the differentiation of nerve cells and melanocytes were both impacted and the synthesis of melanin was inhibited, leading to morphological abnormalities. Additionally, exposure to boscalid led to less and imbalance motion and altered tendency of locomotor in larval fish. Collectively, our results provide new evidences for a comprehensive assessment of its toxicity and a warning for its residues in environment and agricultural products.