Toxicities of Neonicotinoid-Containing Pesticide Mixtures on Nontarget Organisms

Impacts of neonicotinoid compounds on the structure and function of Apis mellifera OBP14: Insights from SPR, ITC, multispectroscopy, and molecular modeling

Honeybees are vital for biodiversity and agricultural productivity, yet their populations are declining globally, partly due to exposure to neonicotinoid pesticides. Odorant-binding protein 14 (OBP14) plays an important role in honeybee chemosensation, but its involvement in neonicotinoid toxicity remains underexplored due to limitations in traditional fluorescence spectroscopy techniques. This gap hampers our understanding of neonicotinoid risks to honeybee health. Here, we explored the molecular interactions between OBP14 from Apis mellifera and three widely used neonicotinoids (imidacloprid, thiamethoxam, and clothianidin) using molecular modeling, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), and multispectroscopy. SPR and ITC characterized the binding affinity, specificity, and thermodynamic parameters of AmelOBP14 interacting with three neonicotinoid compounds, revealing that the binding process is spontaneous and primarily driven by hydrophobic and electrostatic interactions. Molecular modeling highlighted that phenylalanine residue Phe54, near the binding site, plays a critical role in these interactions. UV-vis absorption spectroscopy and synchronous fluorescence spectroscopy (SFS) support slight changes in the microenvironment around the aromatic amino acids of OBP14. Fourier Transform Infrared Spectroscopy (FTIR) and circular dichroism spectroscopy (CD) indicate a decrease in the α-helix content of OBP14, suggesting a change in its secondary structure, while three-dimensional (3D) fluorescence spectroscopy confirms the non-fluorescent nature of the OBP14 polypeptide backbone. The study results revealed its potential as a biomarker for pesticide risk assessment, providing important insights into the molecular mechanisms by which neonicotinoids may impair bee chemosensory function, and offering guidance for the design of safer pesticides to minimize harm to these important pollinators.

Neonicotinoid insecticide sulfoxaflor in the environment: a critical review of environmental fate, degradation mechanism, and toxic effects

In recent decades, neonicotinoids (NEOs) have become widely adopted in agriculture for the control of crop pests and plant pathogens, leading to improved crop yields and enhanced agricultural productivity. However, the prolonged and widespread use of NEOs has raised significant concerns regarding their environmental persistence, food safety, and public health risks. These pesticides have been shown to contaminate various environmental compartments, including soil, surface water, and groundwater, posing potential hazards to ecosystems and human health. Microbes play a crucial role in mitigating the environmental impact of toxic pesticides, with microbial degradation emerging as a promising, cost-effective strategy for degrading pesticide residues. Several sulfoxaflor (SUL)-degrading microbes have been isolated and characterized, yet the identification of microbes, genes, and enzymes responsible for the degradation of NEOs remains an area requiring further investigation. Despite some progress, few reviews have comprehensively addressed the underlying mechanisms of NEOs degradation. This paper provides a detailed review of research on the environmental distribution, exposure risks, and ecotoxicological effects of NEOs, with a particular focus on the environmental fate of SUL. It aims to offer a novel perspective on the fate of NEOs in the environment, their potential toxicological effects, and the role of microbes in mitigating their impact.

Elevated temperature magnifies the toxicity of imidacloprid in the collembolan, Folsomia candida

Global warming subjects soil organisms to elevated temperature stress, while simultaneously altering the detoxification processes for pollutants within these organisms. The combined stressors of increased temperature and pollutants may impose synergistic stress on soil fauna, necessitating detailed investigation. Here, we exposed Collembola (Folsomia candida) to imidacloprid (a neonicotinoid pesticide) in combination with a range of constant temperatures in a full-factorial experimental design to assess the integrated impacts on survival, growth, and bioaccumulation. The results revealed that high temperatures and imidacloprid synergistically inhibited the survival of F. candida. Under 6.4 mg/kg imidacloprid exposure, survival rates decreased by 41.38 % at 30.2 °C and 68.75 % at 30.5 °C, compared to the same temperature treatments without imidacloprid exposure. Bayesian model analysis confirmed a significant synergistic interaction between imidacloprid and temperature on survival. Interestingly, at elevated temperatures, the internal concentration of imidacloprid in F. candida significantly decreased, while the soil concentration of the insecticide remained stable. This suggests that the observed synergistic effect is not due to increased pollutant accumulation within F. candida at higher temperatures, but rather the exhaustion of energy resources needed for detoxification and thermal stress management. This dual-stressor-induced energy competition underpins the synergistic interactions observed. Our findings highlight the significant synergistic effects of high temperatures and imidacloprid on Collembola, underscoring an increased ecological risk under such conditions.

Assessing neonicotinoid pollution in aquatic ecosystems: A systematic review and bibliometric-content analysis

The widespread use and distribution of neonicotinoids (NNIs) have led to their significant accumulation in aquatic ecosystems, posing serious ecological risks to non-target species and the human food chain. This review employed bibliometric analysis to examine global research from 2013 to 2023, highlighting key trends, advancements, and research priorities. Moreover, we summarized the global distribution of NNIs in various aquatic environments through content analysis and assessed their ecotoxicological effects under controlled laboratory conditions. Our findings indicate a growing global concern about NNIs in aquatic systems, with research efforts primarily concentrated in regions most affected by their use. The presence of NNIs across different water bodies highlights widespread contamination, with China facing particularly severe pollution. However, research on the safety of NNIs in aquatic environments remains insufficient. Future studies should focus on monitoring chronic NNIs exposure and its long-term ecological impacts through field research. Moreover, developing microbial formulations, integrating phytoremediation, and combining multiple technologies for synergy are crucial for developing sustainable strategies to mitigate NNIs pollution, protect human health, and preserve aquatic ecosystems.

Neonicotinoid pesticides in African agriculture: What do we know and what should be the focus for future research?

This review provides a comprehensive overview of the direct and indirect effects of neonicotinoid pesticides (NEO-P) within African agricultural ecosystems and identifies research gaps, particularly in the monitoring and regulation of pesticide use. We observed a decline in the numbers of NEO-P studies conducted in Africa since 2019 with 40.7% of the countries reporting at least one study to date. Imidacloprid (33.5%), acetamiprid (23.3%), and thiamethoxam (25.0%) are the most reported NEO-P across the continent with concentrations range from 9.0 × 10-5 to 7.2 × 107 mg kg-1, 1.7 × 10-5 to 2.1 × 103 mg kg-1, and 1.0 × 10-5 to 4.7 × 104 mg kg-1, respectively. NEO-P have been reported in honey, water, vegetables, fruits, and staple foods in most countries and in 92-100% of human urine samples collected in Ghana and Cameroon. This widespread presence indicates a potential food safety and public health concern, warranting further study. Studies on NEO-P interactions with bees have emanated mainly from North Africa (35.3% published studies) while Central/Middle, and Southern Africa accounted for 11.8% each of these studies, all of which were conducted in Cameroon and South Africa, respectively. It is important to have contextual evidence to understand neonicotinoids-pollinator interactions across specific African regions and countries; however, literature regarding the extent of NEO-P toxicities/effects on pollinators is required in 44 African countries. The environmental persistence of NEO-P and their broad-spectrum impact necessitate a re-evaluation of current regulatory practices and adoption of more sustainable pest management strategies across the continent. Furthermore, future studies should focus on investigating the long-term exposure to NEO-P, advanced computational methods in ecological risk assessments and eco-friendly alternatives to NEO-P.

Efficacy of salicylic acid (SA) in modulating the dynamics of pesticide-thiamethoxam-induced stress responses in Brassica juncea L. insights from biochemical and molecular dissection

The present study uncovers the impacts of pesticide-thiamethoxam (TMX- 750 mg L-1) and salicylic acid (SA- 0.01, 0.1 and 1 mM) in Brassica juncea L. TMX poisoning exacerbates the nuclear and membrane damage, whereas an increment in the oxidative stress markers like hydrogen peroxide (H2O2), superoxide anions (O2-) and malondialdehyde (MDA) contents has been observed. The significance of phytohormone SA in mitigating TMX toxicity by enhancing the growth, and antioxidant capacities of B. juncea seedlings is not well documented. Salicylic acid priming to these TMX-exposed seedlings maximizes the germination potential by 34%, and root, shoot length by 86.9% and 41.5%, whereas, minimizing the levels of oxidative stress indicators such as H2O2 by 34.8%, O2- by 26.9% and amounts of MDA by 45.6% and EL (electrolyte leakage) contents by 22.7% under 1 mM of SA. Also, an increment in the activity of enzymatic antioxidants like superoxide dismutase (SOD), ascorbate peroxidase (APOX), glutathione peroxidase (GPOX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), peroxidase (POD), and catalase (CAT) by 122.1%, 186%, 39%, 82.61%, 40.02%, 75.6% and 59.5% was observed when TMX exposed seeds were supplemented with the highest SA (1 mM) concentration. Whereas, an upregulation in the gene expressions of enzymatic antioxidants was assessed as well as a swift decrease in the RBOH1 (respiratory burst oxidase1) gene expression was observed under the subsequent SA supplementation. Thus, the results effectively address the ameliorative potentials of exogenously applied SA in order to maximize the growth and development, by mediating osmotic adjustments, and antioxidant potentials in B. juncea L.

Wildlife ecotoxicology of plant protection products: knowns and unknowns about the impacts of currently used pesticides on terrestrial vertebrate biodiversity

Agricultural practices are a major cause of the current loss of biodiversity. Among postwar agricultural intensification practices, the use of plant protection products (PPPs) might be one of the prominent drivers of the loss of wildlife diversity in agroecosystems. A collective scientific assessment was performed upon the request of the French Ministries responsible for the Environment, for Agriculture and for Research to review the impacts of PPPs on biodiversity and ecosystem services based on the scientific literature. While the effects of legacy banned PPPs on ecosystems and the underlying mechanisms are well documented, the impacts of current use pesticides (CUPs) on biodiversity have rarely been reviewed. Here, we provide an overview of the available knowledge related to the impacts of PPPs, including biopesticides, on terrestrial vertebrates (i.e. herptiles, birds including raptors, bats and small and large mammals). We focused essentially on CUPs and on endpoints at the subindividual, individual, population and community levels, which ultimately linked with effects on biodiversity. We address both direct toxic effects and indirect effects related to ecological processes and review the existing knowledge about wildlife exposure to PPPs. The effects of PPPs on ecological functions and ecosystem services are discussed, as are the aggravating or mitigating factors. Finally, a synthesis of knowns and unknowns is provided, and we identify priorities to fill gaps in knowledge and perspectives for research and wildlife conservation.

Neonicotinoids Impact All Aspects of Bird Life: A Meta-Analysis

Worldwide, bird populations are declining dramatically. This is especially the case in intensely used agricultural areas where the application of neonicotinoid insecticides is thought to-unintendedly-cause a cascade of negative impacts throughout food webs. Additionally, there could be direct (sub-) lethal impacts of neonicotinoids on birds, but to date there is no comprehensive quantitative assessment to confirm or rule out this possibility. Therefore, we use a meta-analytical approach synthesising 1612 effect sizes from 49 studies and show that neonicotinoids consistently harm bird health, behaviour, reproduction, and survival. Thus, in addition to reduced food availability, the negative direct effects of exposure to neonicotinoids likely contribute to bird population declines globally. Our outcomes are pivotal to consider in future risk assessments and pesticide policy: despite localised bans, the metabolites and residues of neonicotinoids remain present in the environment and in birds and will thus have long-lasting direct effects on both the individual and the population levels.

Lysosomal disruption, mitochondrial impairment, histopathological and oxidative stress in rat's nervous system after exposure to a neonicotinoid (imidacloprid)

Imidacloprid (IMI), a neonicotinoid pesticide, has been widely used due to its high efficiency against insect pests. However, its prolonged exposure may pose significant risks to non-target organisms, including mammals. Recent studies have raised concerns about its potential neurotoxicity, yet the underlying mechanisms remain poorly understood. This study aimed to assess the neurotoxic effects of chronic Imidacloprid exposure in Wistar rats, focusing on oxidative stress, mitochondrial dysfunction, and lysosomal disruption. Wistar rats were orally administered two doses of Imidacloprid (5 mg/kg and 50 mg/kg body weight) for three months. Neurotoxic effects were assessed by measuring key biochemical markers such as the enzymatic activities of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and glutathione S-transferase (GST). Non-enzymatic markers, including glutathione (GSH) levels and malondialdehyde (MDA) index, were also evaluated. Mitochondrial function was assessed by analyzing oxygen consumption, swelling, and membrane permeability and histopathological changes. Lysosomal stability was examined using the Neutral Red Retention Time (NRRT) assay. Neutral red is a dye that accumulates in the acidic environment of lysosomes. Healthy lysosomes retain the dye, while compromised lysosomes lose it, indicating destabilization. By measuring the amount of neutral red retained in lysosomes, the NRRT assay assesses lysosomal integrity. Lysosomal pH variations were also monitored to evaluate functional changes. Microscopic analysis provided insight into structural changes in lysosomes and other cell components. Lysosomal destabilization was further confirmed by morphological alterations observed through light microscopy, revealing a progressive, time-dependent degeneration of lysosomal structures, including lysosomal expansion, neutral red dye leakage, and cell rounding. These changes reflected a temporal evolution of lysosomal damage, progressing from minor structural disruptions to more severe alterations as exposure continued, observable at the microscopic level. During the study, clinical observations of intoxicated rats included symptoms such as lethargy, reduced activity levels, and impaired motor coordination. High-dose Imidacloprid exposure led to noticeable behavioral changes, including decreased exploratory behavior and altered grooming patterns. Additionally, signs of neurotoxic effects, such as tremors or ataxia, were observed in the rats exposed to the higher dose, reflecting the systemic impact of chronic pesticide exposure. The results revealed a significant decrease in the enzymatic activities of CAT, GPx, and SOD, accompanied by an increase in GST activity. A notable reduction in glutathione levels and a rise in MDA index were observed, indicating enhanced oxidative stress in the brain. Mitochondrial impairment was evidenced by disturbances in oxygen consumption, increased swelling, and altered membrane permeability. Lysosomal destabilization was confirmed by reduced retention of neutral red dye, structural changes in lysosomes, and a significant rise in lysosomal pH in the IMI-exposed groups. In addition, the histopathological features indicate that imidacloprid at the given dose and exposure duration may have caused notable neurotoxic effects in Wistar rat brain tissue. Chronic exposure to Imidacloprid induces oxidative stress, mitochondrial dysfunction, lysosomal disruption and histopathological alterations in the central nervous system of Wistar rats. These findings provide valuable insights into the neurotoxic mechanisms of neonicotinoid pesticides, highlighting the need for further research to understand the long-term effects of Imidacloprid exposure on mammalian health.

Characterization of Neonicotinoid Metabolites by Cytochrome P450-Mediated Metabolism in Poultry

Neonicotinoids, a neuro-effective class of insecticides, are heavily applied in agricultural activities worldwide. Poultry can be exposed to neonicotinoids by several routes, but the knowledge of neonicotinoid's metabolism in poultry and its associated interspecies differences is highly limited. Hence, this study aims to investigate the species differences in metabolite formations, as well as cytochrome P450 (CYP)-dependent metabolism of four major neonicotinoid compounds, acetamiprid, imidacloprid, clothianidin, and thiamethoxam, in poultry. In vitro biotransformation assays using hepatic microsomes of chicken, ducks, geese, quails, and rats were conducted. Metabolites of neonicotinoids were then screened by LC/Q-TOF and quantified by LC/MS/MS. The results revealed an existence of interspecies differences in the formations of N-[(6-chloro-3-pyridyl) methyl] -N-methyl acetamidine (IM-1-5) of acetamiprid and dm-clothianidin of clothianidin between chicken and other species. In addition, the greatest CYP activities in the metabolism of most neonicotinoid substrates, such as acetamiprid to dm-acetamiprid, imidacloprid to hydroxylated-imidacloprid and imidacloprid-olefin, clothianidin to dm-clothianidin, and thiamethoxam to clothianidin, were found in chicken. These results suggested that the CYPs in chicken may have a greater capacity for metabolism of neonicotinoids compared to other poultry. This study further revealed that the maximum intrinsic clearance of dn-imidacloprid and dn-clothianidin in ducks may be superintended by CYP-mediated nitro-reductions of imidacloprid and clothianidin. Further studies employing CYP recombinant enzymes may be required to elucidate the specific CYP isoforms that may be involved in neonicotinoid metabolism in avian species.

Structural gonadal lesions observed in Japanese quail (Coturnix coturnix japonica) following exposure during puberty to the neonicotinoid pesticide, imidacloprid

Exposure to the neonicotinoid insecticide, imidacloprid (IMI), causes reproductive toxicity in mammals and reptiles. However, reports on the effects of IMI on the gonads in birds are grossly lacking. Therefore, this study investigated the effects of pubertal exposure to IMI on the histology, ultrastructure, as well as the cytoskeletal proteins, desmin, smooth muscle actin and vimentin, of the gonads of Japanese quail (Coturnix coturnix japonica). Quails were randomly divided into four groups at 5 weeks of age. The control group was given only distilled water, whereas, the other three experimental groups, IMI was administered by oral gavage at 1.55, 3.1, and 6.2 mg/kg, twice per week for 4 weeks. Exposure to IMI doses of 3.1 and 6.2 mg/kg caused dose-dependent histopathological changes in the ovary and testis. In the ovary, accumulation of lymphocytes, degenerative changes, and necrosis with granulocyte infiltrations were observed, while in the testis, distorted seminiferous tubules, germ cell sloughing, vacuolisations, apoptotic bodies, autophagosomes, and mitochondrial damage were detected. These changes were accompanied by a decreased number of primary follicles (P ≤ 0.05) in the ovary and a decrease (P ≤ 0.05) in the epithelial height, luminal, and tubular diameters of seminiferous tubules at the two higher dosages. In addition, IMI had a negative effect on the immunostaining intensity of desmin, smooth muscle actin, and vimentin in the ovarian and testicular tissue. In conclusion, exposure to IMI during puberty can lead to a range of histopathological alterations in the gonads of Japanese quails, which may ultimately result in infertility.

Following Regulation, Imidacloprid Persists and Flupyradifurone Increases in Nontarget Wildlife

After regulation of pesticides, determination of their persistence in the environment is an important indicator of effectiveness of these measures. We quantified concentrations of two types of systemic insecticides, neonicotinoids (imidacloprid, acetamiprid, clothianidin, thiacloprid, and thiamethoxam) and butenolides (flupyradifurone), in off-crop nontarget media of hummingbird cloacal fluid, honey bee (Apis mellifera) nectar and honey, and wildflowers before and after regulation of imidacloprid on highbush blueberries in Canada in April 2021. We found that mean total pesticide load increased in hummingbird cloacal fluid, nectar, and flower samples following imidacloprid regulation. On average, we did not find evidence of a decrease in imidacloprid concentrations after regulation. However, there were some decreases, some increases, and other cases with no changes in imidacloprid levels depending on the specific media, time point of sampling, and site type. At the same time, we found an overall increase in flupyradifurone, acetamiprid, thiamethoxam, and thiacloprid but no change in clothianidin concentrations. In particular, flupyradifurone concentrations observed in biota sampled near agricultural areas increased twofold in honey bee nectar, sevenfold in hummingbird cloacal fluid, and eightfold in flowers after the 2021 imidacloprid regulation. The highest residue detected was flupyradifurone at 665 ng/mL (parts per billion [ppb]) in honey bee nectar. Mean total pesticide loads were highest in honey samples (84 ± 10 ppb), followed by nectar (56 ± 7 ppb), then hummingbird cloacal fluid (1.8 ± 0.5 ppb), and least, flowers (0.51 ± 0.06 ppb). Our results highlight that limited regulation of imidacloprid does not immediately reduce residue concentrations, while other systemic insecticides, possibly replacement compounds, concurrently increase in wildlife. Environ Toxicol Chem 2024;43:1497-1508. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Anthropogenic-induced ecological risks on marine ecosystems indicated by characterizing emerging pollutants in Pearl River Estuary, China

Anthropogenic Contaminants of Emerging Concern (CECs) in marine environments have raised significant concerns. Yet, analyses detailing their origins, fate, and environmental effects are limited. This study employs an integrated non-target screening methodology to elucidate CECs existence across 46 sampling sites in the Pearl River Estuary (PRE) of the South China Sea. Assisted by advanced liquid chromatography-high resolution mass spectrometry, we discovered 208 chemicals in six usage categories, with pesticides (33 %) and pharmaceuticals (29 %) predominating. Several CECs drew attention for their consistent detections, profound abundance, and significant ecotoxicities. The wide detection of them at offshore sites further implies that anthropogenic activities may contribute to large-scale contamination. Meanwhile, distinct distribution patterns of CECs across PRE are evident in semi-quantitative results, indicating regional anthropogenic influences. Identified transformation products may establish a novel and non-negligible negative contribution to ecology through elevated environmental toxicities, exemplified by HMMM and atrazine. Based on the ecological risks, we compiled a prioritized list of 21 CECs warranting intensified scrutiny. Our findings indicate the introduction of various CECs into the South China Sea via PRE, emphasizing the urgent necessity for ongoing surveillance of discharged CECs at estuary areas and assessment of their marine ecological consequences.

Isolation of the AccCDK8 gene of Apis cerana cerana and its functional analysis under pesticide and heavy metal stress

Environmental pollution has gained negative attention in recent years. The pesticides and heavy metals are top list of environmental toxicants directly endangering the survival and development of Apis cerana cerana. Cyclin-dependent kinases (CDKs) are heteromeric serine/threonine kinases that participate in cell cycle regulation and have a vital role in pesticide and heavy metal stress in Apis cerana cerana. In this experiment, we filtered out CDK8 gene from Apis cerana cerana (AccCDK8) and investigated its functions of pesticide and heavy metals resistance. Sequence analysis indicated that AccCDK8 is highly homologous to multiple CDK8s and contains a highly conserved CDK active site sequence. Phylogenetic analysis showed that AmCDK8 and AccCDK8 were closely related evolutionarily in Apis mellifera. Transcriptome analysis revealed that AccCDK8 expression was differentially affected after exposure to pesticide and heavy metal stresses. This indicates that AccCDK8 has a significant role in the resistance of Apis cerana cerana to pesticide and heavy metal stresses. It has implications for studying the function of CDK in other insects in response to stress.

Toxicologic effect and transcriptome analysis for sub-chronic exposure to carbendazim, prochloraz, and their combination on the liver of mice

Carbendazim (CBZ) and prochloraz (PCZ) are broad-spectrum fungicides used in agricultural peat control. Both fungicides leave large amounts of residues in fruits and are toxic to non-target organisms. However, the combined toxicity of the fungicides to non-target organisms is still unknown. Therefore, we characterized the toxic effects of dietary supplementation with CBZ, PCZ, and their combination for 90 days in 6-week-old male Institute of Cancer Research (ICR) mice. CBZ-H (100 mg/kg day), PCZ-H (10 mg/kg day), and their combination treatments increased the relative liver weights and caused liver injury. The serum total cholesterol (TC), triglyceride (TG), glucose (Glu), pyruvate (PYR), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were reduced, and synergistic toxicity was observed. Hepatic transcriptome revealed that 326 differentially expressed genes (DEGs) of liver were observed in the CBZ treatment group, 149 DEGs in the PCZ treatment group, and 272 DEGs in the combination treatment group. According to KEGG enrichment analysis, the fungicides and their combination affected lipid metabolism, amino acid metabolism, and ferroptosis. In addition, the relative mRNA levels of key genes involved in lipid metabolism were also examined. Compared with individual exposure, combined exposure to CBZ and PCZ caused a more obvious decrease in the expression of some genes related to glycolipid metabolism. Furthermore, the relative mRNA levels of some key genes in the combination treatment group were lower than those in the CBZ and PCZ treated groups. In summary, CBZ, PCZ, and their combination generally caused hepatotoxicity and glycolipid metabolism disorders, which could provide new insights for investigating the combined toxicity of multiple fungicides to animals.

Biochemical and gene expression alterations due to individual exposure of atrazine, dichlorvos, and imidacloprid and their combination in zebrafish

In environmental toxicology, combined toxicity has emerged as an important concern. Atrazine (ATZ), dichlorvos (DIC), and imidacloprid (IMD) are the major pesticides, extensively used to control insect, flies, mosquitoes, and weed. Here, we investigate whether the exposure to three different types of pesticides individually and in combination for 24 h alters antioxidant enzyme responses in zebrafish (Danio rerio). Oxidative stress parameters (biochemical and mRNA expression), acetylcholinesterase (AChE) activity, and Metallothionein-II (MT-II) mRNA expression levels were measured. Present work includes toxicological assessment of individual and combined (CMD) exposure of ATZ (185.4 µM), DIC (181 µM), IMD (97.8 µ), and CMD (ATZ 92.7 µM + DIC 90.5 µM + IMD 48.9 µM), in the liver, kidney, and brain of adult zebrafish. Lipid peroxidation (LPO), glutathione (GSH) content, AChE, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity along with mRNA expression of SOD, CAT, GPx, and MT-II were evaluated. Briefly, LPO, GSH content, the activity of AChE, and all antioxidant enzymes enhanced significantly in individual exposure, which was further altered in the CMD group. The mRNA expression of SOD, CAT, GPx, and MT-II in the liver and kidney showed significant down-regulation in all exposed groups. In the brain, significant upregulation in mRNA expression of SOD, CAT, GPx, and MT-II was observed in DIC and IMD groups, while ATZ and CMD showed significant downregulation except for GPx. Findings postulate that the CMD group exhibits synergistic toxic manifestation. The present study provides the baseline data on the combined toxic effects of pesticides and suggests regulating the use of pesticides.

Laboratory Determination of Particulate-Matter-Bound Agrochemical Toxicity among Honeybees, Mason Bees, and Painted Lady Butterflies

Pollinator population declines are global phenomena with severe consequences for native flora and agriculture. Many factors have contributed to pollinator declines including habitat loss, climate change, disease and parasitism, reductions in abundance and diversity of foraging resources, and agrochemical exposure. Particulate matter (PM) serves as a carrier of toxic agrochemicals, and pollinator mortality can occur following exposure to agrochemical-contaminated PM. Therefore, laboratory-controlled experiments were conducted to evaluate impacts of individual PM-bound agrochemicals. Honeybees (Apis mellifera), blue orchard mason bees (Osmia lignaria), and painted lady butterfly (Vanessa cardui) larvae were exposed to bifenthrin, permethrin, clothianidin, imidacloprid, abamectin, and ivermectin via suspended, airborne PM. Agrochemical concentrations in PM to which pollinators were exposed were based on concentrations observed in fugitive beef cattle feedyard PM including a "mean" treatment and a "max" treatment reflective of reported mean and maximum PM-bound agrochemical concentrations, respectively. In general, pollinators in the mean and max treatments experienced significantly higher mortality compared with controls. Honeybees were most sensitive to pyrethroids, mason bees were most sensitive to neonicotinoids, and painted lady butterfly larvae were most sensitive to macrocyclic lactones. Overall, pollinator mortality was quite low relative to established toxic effect levels derived from traditional pollinator contact toxicity tests. Furthermore, pollinator mortality resulting from exposure to individual agrochemicals via PM was less than that reported to occur at beef cattle feedyards, highlighting the importance of mixture toxicity to native and managed pollinator survival and conservation. Environ Toxicol Chem 2023;42:2642-2650. © 2023 SETAC.

Multiple pesticide residues and risk assessment of Dendrobium officinale Kimura et Migo: a three-year investigation

Dendrobium officinale Kimura et Migo (D. officinale) is a traditional Chinese medicine homologous to food, and its safety has attracted considerable attention. Pesticide residues are critical indicators for evaluating the safety of D. officinale. This study investigated the levels of 130 pesticides in 137 stem samples and 82 leaf samples from five main production areas of D. officinale in Zhejiang Province, along with the associated risk of dietary exposure for the population between 2019 and 2021. Forty-five pesticides were detected in 171 samples, of which pyraclostrobin had the highest detection frequency. Multiple residues were detected in 52.56% of the stem samples and 54.88% of the leaf samples, and one stem sample contained up to 18 pesticides. Here, the level of difenoconazole in three samples (two stem samples and one leaf sample) was higher than the maximum residue limit (MRL) in China. Considering the possible health risks related to pesticide residues, a risk assessment of human exposure to pesticides via the intake of D. officinale stems and leaves was evaluated, indicating negligible short-term, long-term, and cumulative risks to human health. However, considering the high detection rate of unregistered pesticides, the supplementation of pesticide registration information on D. officinale should be expedited, and MRLs should be established to ensure food and drug safety.

Effects of mixed application of avermectin, imidacloprid and carbendazim on soil degradation and toxicity toward earthworms

The application of pesticides in mixtures often exerts multiple pressures on agricultural soils in the short term. Therefore, it is necessary to assess the effects of mixed application on the environmental behavior and ecotoxicity of pesticides in soil. In this study, we assessed the effects of three common pesticides through mixed application on soil degradation and toxicity toward the earthworm Eisenia fetida. Compared with the degradation half-lives (DT50) the single pesticide, the DT50 values of avermectin, imidacloprid and carbendazim in the binary mixtures were similar. However, their DT50 values in the ternary mixtures were approximately 1.5 times longer than those in the individual applications, enhancing their stable in soil after two or three applications. The ternary mixtures of the pesticides showed significantly synergistic toxicity toward E. fetida, while their binary mixtures exhibited a changing interaction throughout the entire effect level range. The ternary mixtures activated higher SOD and CAT activities in E. fetida than the individual treatments, confirming their synergistic effects. By conducting avoidance tests with E. fetida, ternary toxic interactions were effectively assessed within a relatively short testing period. In summary, the three pesticides in ternary mixtures exhibited longer degradation half-lives and synergistic toxicity toward earthworms compared to individual or binary mixtures.

Detection methods, migration patterns, and health effects of pesticide residues in tea

Due to its rich health benefits and unique cultural charm, tea drinking is increasingly popular with the public in modern society. The safety of tea is the top priority that affects the development of tea industry and the health of consumers. During the process of tea growth, pesticides are used to prevent the invasion of pests and diseases with maintaining high quality and stable yield. Because hot water brewing is the traditional way of tea consumption, water is the main carrier for pesticide residues in tea into human body accompanied by potential risks. In this review, pesticides used in tea gardens are divided into two categories according to their solubility, among which water-soluble pesticides pose a greater risk. We summarized the methods of the sample pretreatment and detection of pesticide residues and expounded the migration patterns and influencing factors of tea throughout the process of growth, processing, storage, and consumption. Moreover, the toxicity and safety of pesticide residues and diseases caused by human intake were analyzed. The risk assessment and traceability of pesticide residues in tea were carried out, and potential eco-friendly improvement strategies were proposed. The review is expected to provide a valuable reference for reducing risks of pesticide residues in tea and ensuring the safety of tea consumption.

A novel laboratory method for simulating pollinator exposure to agrochemical-laden particulate matter

Environmental transport and deposition of particulate matter (PM) associated with toxic chemicals has begun to receive attention as a source of risk to pollinators. For example, dust arising from manipulations of insecticide-treated seed has potential to exert toxic effects among non-target insects. Similarly, synthetic steroid growth promoters, antibiotics and multiple insecticides and parasiticides detected in fugitive beef cattle feedyard PM may also negatively impact pollinators since many of these chemicals have been detected on wildflowers and pollinators collected near beef cattle feedyards. Therefore, there is a need to assess risk to pollinators posed by deposition of agrochemical-laden PM, both in the field and the laboratory. Unfortunately, established laboratory methods for simulating PM exposure or toxicity associated with contaminated PM are few and highly situation-specific. Herein we describe development and use of a PM circulation system that can be employed to evaluate toxicity of agrochemical-contaminated PM in the laboratory under controlled conditions. Two model organisms (honeybees (Apis mellifera) and mason bees (Osmia lignaria)) were exposed to agrochemical-free PM in the circulator system, and post-exposure mortality was compared with controls. No significant differences in mortality between exposed and control bees were observed. Next, honeybees and mason bees were exposed to PM spiked with an insecticide known to exert toxic effects to pollinators (thiamethoxam). Bees experienced significantly higher mortality when exposed to thiamethoxam-laden PM at environmentally relevant concentrations as compared to bees exposed to agrochemical-free PM. These results confirm the validity of these methods for use in controlled laboratory PM toxicity tests and offer a source of positive and negative control groups for laboratory and field experiments examining exposure of pollinators to potentially toxic agrochemical-laden PM. This method facilitates generation of more realistic toxicity data than standard contact toxicity tests when pollinator exposure scenarios involve particulate-based agrochemicals or other toxic chemicals.

Environmental occurrence, toxicity concerns, and biodegradation of neonicotinoid insecticides

Neonicotinoids (NEOs) are fourth generation pesticides, which emerged after organophosphates, pyrethroids, and carbamates and they are widely used in vegetables, fruits, cotton, rice, and other industrial crops to control insect pests. NEOs are considered ideal substitutes for highly toxic pesticides. Multiple studies have reported NEOs have harmful impacts on non-target biological targets, such as bees, aquatic animals, birds, and mammals. Thus, the remediation of neonicotinoid-sullied environments has gradually become a concern. Microbial degradation is a key natural method for eliminating neonicotinoid insecticides, as biodegradation is an effective, practical, and environmentally friendly strategy for the removal of pesticide residues. To date, several neonicotinoid-degrading strains have been isolated from the environment, including Stenotrophomonas maltophilia, Bacillus thuringiensis, Ensifer meliloti, Pseudomonas stutzeri, Variovorax boronicumulans, and Fusarium sp., and their degradation properties have been investigated. Furthermore, the metabolism and degradation pathways of neonicotinoids have been broadly detailed. Imidacloprid can form 6-chloronicotinic acid via the oxidative cleavage of guanidine residues, and it is then finally converted to non-toxic carbon dioxide. Acetamiprid can also be demethylated to remove cyanoimine (=N-CN) to form a less toxic intermediate metabolite. A few studies have discussed the neonicotinoid toxicity and microbial degradation in contaminated environments. This review is focused on providing an in-depth understanding of neonicotinoid toxicity, microbial degradation, catabolic pathways, and information related to the remediation process of NEOs. Future research directions are also proposed to provide a scientific basis for the risk assessment and removal of these pesticides.

High Performance of Ionic-Liquid-Based Materials to Remove Insecticides

Neonicotinoids are systemic insecticides commonly used for pest control in agriculture and veterinary applications. Due to their widespread use, neonicotinoid insecticides (neonics) are found in different environmental compartments, including water, soils, and biota, in which their high toxicity towards non-target organisms is a matter of great concern. Given their widespread use and high toxicity, the development of strategies to remove neonics, while avoiding further environmental contamination is of high priority. In this work, ionic-liquid-based materials, comprising silica modified with tetraalkylammonium cations and the chloride anion, were explored as alternative adsorbent materials to remove four neonics insecticides, namely imidacloprid, acetamiprid, thiacloprid, and thiamethoxam, from aqueous media. These materials or supported ionic liquids (SILs) were first synthesized and chemically characterized and further applied in adsorption studies. It was found that the equilibrium concentration of the adsorbate in the solid phase decreases with the decrease in the SIL cation alkyl chain length, reinforcing the relevance of hydrophobic interactions between ionic liquids (ILs) and insecticides. The best-identified SIL for the adsorption of the studied insecticides corresponds to silica modified with propyltrioctylammonium chloride ([Si][N3888]Cl). The saturation of SILs was reached in 5 min or less, showing their fast adsorption rate towards all insecticides, in contrast with activated carbon (benchmark) that requires 40 to 60 min. The best fitting of the experimental kinetic data was achieved with the Pseudo Second-Order model, meaning that the adsorption process is controlled at the solid-liquid interface. On the other hand, the best fitting of the experimental isotherm data is given by the Freundlich isotherm model, revealing that multiple layers of insecticides onto the SIL surface may occur. The continuous removal efficiency of the best SIL ([Si][N3888]Cl) by solid-phase extraction was finally appraised, with the maximum adsorption capacity decreasing in the following sequence: imidacloprid > thiacloprid > thiamethoxam > acetamiprid. Based on real reported values, under ideal conditions, 1 g of [Si][N3888]Cl is able to treat at least 106 m3 of wastewater and water from wetland contaminated with the studied neonics. In summary, the enhanced adsorption capacity of SILs for a broad diversity of neonics was demonstrated, reinforcing the usefulness of these materials for their removal from aqueous matrices and thus contributing to preventing their introduction into the ecosystems and reducing their detrimental effects in the environment and human health.

Agricultural surface water, imidacloprid, and chlorantraniliprole result in altered gene expression and receptor activation in Pimephales promelas

The toxicity of single pesticides is likely underestimated when considering complex pesticide mixtures found in agricultural runoff and this is especially true for newer pesticides with little toxicity data on non-target species. The goal of our study was to compare the toxicity of two newer pesticides, imidacloprid (IMI) and chlorantraniliprole (CHL), when an invertebrate and fish were exposed to single compounds, binary mixtures or surface water collected near agricultural fields. A secondary goal was to determine whether changes in select subcellular molecular pathways correspond to the insecticides' mechanisms of activity in aquatic organisms. We conducted acute (96 h) exposures using a dilution series of field water and environmentally relevant concentrations of single and binary mixtures of IMI and CHL. We then evaluated survival, gene expression and the activity of IMI toward the n-acetylcholine receptor (nAChR) and CHL activity toward the ryanodine receptor (RyR). Both IMI and CHL were detected at all sampling locations for May 2019 and September 2019 sampling dates and exposure to field water led to high invertebrate but not fish mortality. Fish exposed to field collected water had significant changes in the relative expression of genes involved with detoxification and neuromuscular function. Exposure of fish to single compounds or binary mixtures of IMI and CHL led to increased relative gene expression of RyR in fish. Furthermore, we found that IMI targets the nAChR in aquatic invertebrates and that CHL can cause overactivation of the RyR in invertebrates and fish. Overall, our finding suggests that IMI and CHL may impact neuromuscular health in fish. Expanding monitoring efforts to include sublethal and molecular assays would allow the detection of subcellular level effects due to complex mixtures present in surface water near agricultural areas.

Microbial Technologies Employed for Biodegradation of Neonicotinoids in the Agroecosystem

Neonicotinoids are synthetic pesticides widely used for the control of various pests in agriculture throughout the world. They mainly attack the nicotinic acetylcholine receptors, generate nervous stimulation, receptor clot, paralysis and finally cause death. They are low volatile, highly soluble and have a long half-life in soil and water. Due to their extensive use, the environmental residues have immensely increased in the last two decades and caused many hazardous effects on non-target organisms, including humans. Hence, for the protection of the environment and diversity of living organism's the degradation of neonicotinoids has received widespread attention. Compared to the other methods, biological methods are considered cost-effective, eco-friendly and most efficient. In particular, the use of microbial species makes the degradation of xenobiotics more accessible fast and active due to their smaller size. Since this degradation also converts xenobiotics into less toxic substances, the various metabolic pathways for the microbial degradation of neonicotinoids have been systematically discussed. Additionally, different enzymes, genes, plasmids and proteins are also investigated here. At last, this review highlights the implementation of innovative tools, databases, multi-omics strategies and immobilization techniques of microbial cells to detect and degrade neonicotinoids in the environment.