Occurrence and risk of neonicotinoid insecticides in surface water in a rapidly developing region: Application of polar organic chemical integrative samplers

Residual distribution and risk assessment of neonicotinoids in urban green space soils of the pearl river delta, South China: A socioeconomic analysis

Urban green spaces are the soil component in cities that interacts most closely with humans. This study investigated the residues of seven neonicotinoids (NEOs) in soils from urban green spaces within the Pearl River Delta (PRD) region and analyzed the correlation between the residue characteristics and the region's economic development. Notably, we introduced the Nemerow Index method, a comprehensive approach, to quantify the overall pollution level of NEOs in the soil of urban park green spaces and utilized this to assess the cumulative exposure probability risks for different populations in this scenario. We found that: (1) The soil of urban park green spaces exhibited varying degrees of NEOs contamination (Σ7NEOs: N.D.-137.31; 6.25 μg/kg), with imidacloprid and clothianidin constituting the highest proportions (89.46 % and 83.60 %); (2) The residual levels of NEOs in Children's Park were significantly higher than those in community parks within Guangzhou, with an average value of 13.30 μg/kg compared to 3.30 μg/kg; (3) The residual characteristics of NEOs exhibited a positive correlation with regional economic development; specifically, the per capita GDP well correlated with IMIRPF, a summation of seven NEOs in imidacloprid equivalents via relative potency factors (R2 =0.86). Regions with higher economic development typically exhibited elevated IMIRPF levels; (4) The fitted cumulative probability distributions for average daily exposure doses revealed that children's exposure was an order of magnitude higher than adults'. Despite this, the exposure risks for both groups remained within acceptable limits.

Spatiotemporal distribution, risk levels, and transport variations in neonicotinoids and fipronil and its metabolites cross a river-to-sea continuum

Neonicotinoids (NEOs) and fipronil are widely used in pest control, but their spatiotemporal distribution and risk levels in the "river-estuary-bay" system remain unclear. Between 2018 and 2021, 148 water samples from rivers to inshore and offshore seawater in Laizhou Bay, China were collected to investigate the presence of eight NEOs and fipronil and its metabolites (FIPs). Significant seasonal variations in NEOs were observed under the influence of different cultivation practices and climatic conditions, with higher levels in the summer than in the spring. The average concentrations of total neonicotinoids (ΣNEOs) and ∑FIPs decreased from rivers (63.64 ng/L, 2.41 ng/L) to inshore (22.62 ng/L, 0.14 ng/L) and offshore (4.48 ng/L, 0.10 ng/L) seawater of Laizhou Bay. The average concentrations of ΣNEOs decreased by 85.3 % from 2018 to 2021. The predominant insecticides in the study area were acetamiprid, thiamethoxam, imidacloprid, and fipronil sulfone, with a gradual shift toward low-toxicity and environmentally friendly species over time. Influenced by agricultural intensity, ∑NEOs were mostly distributed in the Yellow River, Xiaoqing River, and their estuaries, where they pose chronic ecological risks. However, FIP exhibited high risk in certain rivers and sewage treatment plants owing to the use of animal repellents or landscape gardening insecticides. This study provides evidence of the transfer of NEOs and FIPs from rivers to the ocean and also clarifies their transition dynamics and changes in risk levels from rivers to oceans. Additionally, the study offers data support for identifying critical pesticide control areas.

Prediction of Potential Risk for Flupyradifurone and Its Transformation Products to Hydrobionts

Flupyradifurone (FPF) is considered the latest generation of neonicotinoid insecticides. Here, we investigated the toxicity and ecological risk of FPF and its aerobic transformation products (TPs) to aquatic species using the method of prediction. We found that FPF exhibited moderate or high toxicity to some aquatic species. The 5% hazardous concentration of FPF was 3.84 μg/L for aquatic organisms. We obtained 91 aerobic TPs for FPF, and almost half of FPF TPs exhibited toxicity to fish or Daphnia. Eleven of the TPs of FPF exhibited a high or moderate risk to aquatic ecosystems. All FPF TPs with high and moderate risks contained a 6-chloropyridine ring structure, indicating that the derivant of a pyridine ring exhibits potential risks to aquatic ecosystems. Our results provide insight into the potential risk of FPF to aquatic ecosystems and could be used to help set criteria to control pollution caused by FPF.

Theoretical insights, degradation, and sub-lethal toxicity of thiamethoxam to the planarian Girardia tigrina

Advanced oxidative processes, such as Photo-Fenton, transform organic contaminants due to the attack by radicals. In this context, the lethal and sub-lethal effects of the Cruiser® 350FS (CRZ) with the active ingredient thiamethoxam (TMX) were investigated using the planarian Girardia tigrina. Degradation of thiamethoxam by the Fenton process was also assessed by using theoretical studies and the efficiency of Solar-Fenton versus Fenton. The 48 h LC50 value of CRZ for planarians was 478.6 mg L-1. The regeneration of planarians was significantly affected for concentrations ≥ 17 mg·L-1 of TMX (24 h). The Solar-Fenton showed a high degradation percentage reaching ~70%. The theoretical model showed the atoms of the TMX molecule that will suffer attacks from the formed radicals. Current results open new perspectives concerning the treatment of TMX in the aquatic environment because the 70% degradation seems to be sufficient to reach concentrations that do not induce sub-lethal effects in planarians. Further studies should determine if the by-products generated might be toxic for planaria or other organisms.

Spatiotemporal variation, fluxes and risk evaluation of neonicotinoid insecticides within the midsection of Yangtze River, China: An exploration as ecological protection threshold

Neonicotinoid insecticides (NNIs) have attracted global concern due to its extensive use in agricultural activities and their potential risks to the animal and human health, however, there is limited knowledge on the regional traits and ecological risks of NNIs in the aquatic environments. We herein investigated the occurrence of NNIs within the midsection of Yangtze River in China, offering the inaugural comprehensive report on NNIs within this region. In this study, eleven NNIs were analyzed in 108 river water and sediment samples from three seasons (normal, dry and wet season). We detected a minimum of seven NNIs in the water and four NNIs in the sediment, with total concentrations ranging from 12.33 to 100.5 ng/L in water and 0.08-5.68 ng/g in sediment. The levels of NNIs in both river water and sediment were primarily influenced by the extent of agricultural activities. The estimated annual load of NNIs within the midsection of Yangtze River totaled 40.27 tons, April was a critical contamination period. Relative potency factor (RPF) analysis of the human exposure risk revealed that infants faced the greatest exposure risk, with an estimated daily intake of 11.27 ng kg-1∙bw∙d-1. We established the acute and chronic thresholds for aquatic organisms by employing the Species Sensitive Distribution (SSD) method (acute: 384.1 ng/L; chronic: 168.9 ng/L). Based on the findings from this study, 33% of the river water samples exceeded the chronic ecological risks thresholds, indicating the urgent need for intervention programs to guarantee the safety of the river for aquatic life in the Yangtze River Basin.

Contaminants of emerging concern in water and sediment of the Venice Lagoon, Italy

This study investigates for the first time the contamination of water and sediment of the Venice Lagoon by twenty Contaminants of Emerging Concern (CECs): three hormones, six pharmaceutical compounds (diclofenac and five antibiotics, three of which are macrolides), nine pesticides (methiocarb, oxadiazon, metaflumizone, triallate, and five neonicotinoids), one antioxidant (BHT), and one UV filter (EHMC). Water and sediment samples were collected in seven sites in four seasons, with the aim of investigating the occurrence, distribution, and possible emission sources of the selected CECs in the studied transitional environment. The most frequently detected contaminants in water were neonicotinoid insecticides (with a frequency of quantification of single contaminants ranging from 73% to 92%), and EHMC (detected in the 77% of samples), followed by BHT (42%), diclofenac (39%), and clarithromycin (35%). In sediment the highest quantification frequencies were those of BHT (54%), estrogens (ranging from 35% to 65%), and azithromycin (46%). Although this baseline study does not highlight seasonal or spatial trends, results suggested that two of the major emission sources of CECs in the Venice Lagoon could be tributary rivers from its drainage basin and treated wastewater, due to the limited removal rates of some CECs in WWTPs. These preliminary results call for further investigations to better map priority emission sources and improve the understanding of CECs environmental behavior, with the final aim of drawing up a site-specific Watch List of CECs for the Venice Lagoon and support the design of more comprehensive monitoring plans in the future.

Combined neurotoxicity of aged microplastics and thiamethoxam in the early developmental stages of zebrafish (Daniorerio)

Microplastics (MPs) pollution, together with its consequential effect on aquatic biota, represent a burgeoning environmental concern that has garnered significant scholarly attention. Thiamethoxam (TMX), a prevalently utilized neonicotinoid insecticide, is renowned for its neurotoxic impact and selective action against targeted pests. The aquatic environment serves as a receptacle for numerous pollutants, such as MPs and neonicotinoid insecticides. However, there is currently a lack of comprehensive understanding regarding the toxic effects of co-exposure to aged MPs and neonicotinoid insecticides in aquatic organisms. Therefore, we endeavor to elucidate the deleterious impacts of aged polystyrene (PS) and TMX on zebrafish (Danio rerio) larvae when present at environmentally relevant concentrations, and to reveal the underlying molecular mechanisms driving these effects. Our study showed that exposure to aged PS, TMX, or their combination notably inhibited the heart rate and locomotion of zebrafish larvae, with a pronounced effect observed under combined exposure. Aged PS and TMX were found to diminish the activity of antioxidative enzymes (SOD, CAT, and GST), elevate MDA levels, and disrupt neurotransmitter homeostasis (5-HT, GABA and ACh). Notably, the mixtures exhibited synergistic effects. Moreover, gene expression related to oxidative stress (e.g., gstr1, gpx1a, sod1, cat1, p38a, ho-1, and nrf2b) and neurotransmission (e.g., ache, ChAT, gat1, gabra1, 5ht1b, and 5ht1aa) was significantly altered upon co-exposure to aged PS and TMX in larval zebrafish. In summary, our findings support the harmful effects of aged MPs and the neonicotinoid insecticides they carry on aquatic organisms. Results from this study enhance our understanding of the biological risks of MPs and insecticides, as well as help fill existing knowledge gaps on neonicotinoid insecticides and MPs coexistence toxicity in aquatic environment.

Rapid screening of acetylcholinesterase active contaminants in water: A solid phase microextraction-based ligand fishing approach

Effect-directed analysis (EDA) has been increasingly used for screening toxic contaminants in the environment, but conventional EDA procedures are often time-consuming and labor-extensive. This challenges the use of EDA for toxicant identification in the scenarios when quick answers are demanded. Herein, a solid phase microextraction ligand fishing (SPME-LF) strategy has been proposed as a rapid EDA approach for identifying acetylcholinesterase (AChE) active compounds in water. The feasibility of ligand fishing techniques for screening AChE active chemicals from environmental mixtures was first verified by a membrane separation method. Then, SPME fibers were prepared through self-assembly of boronic acid groups with AChE via co-bonding and applied for SPME-LF. As AChE coated SPME fibers selectively enriched AChE-active compounds from water, comparing sorbing compounds by the SPME fibers with and without AChE coating can quickly distinguish AChE toxicants in mixtures. Compared with conventional EDA, SPME-LF does not require repeating sample separations and bioassays, endowing SPME-LF with the merits of low-cost, labor-saving, and user-friendly. It is believed that cost-efficient and easy-to-use SPME-LF strategy can potentially be a rapid EDA method for screening receptor-specific toxicants in aquatic environment, especially applicable in time-sensitive screening.

Assessing neonicotinoid accumulation and ecological risks in the aquatic environment of Yangtze River Basin, China

Neonicotinoids (NNIs) constitute commonly used pesticides across various regions, however, the lack of research and data on its long-term effects and threshold levels within specific ecosystems have left an important knowledge gap. This study aimed to comprehensively examine NNI concentrations and their potential impacts on human health and aquatic organisms in the region of the Yangtze River Basin (YRB). The study employed datasets on seven commonly applied NNIs across 244 surface water samples collected from 12 distinct geographic sites within the YRB. The relative potency factor was used to evaluate human exposure risks, while the species sensitivity distribution could estimate acute and chronic hazardous concentrations for 5% of species (HC5) for NNIs impacting aquatic organisms. Analysis revealed varying NNI concentrations across the sampled sites, with thiacloprid recording the lowest concentration at 0.1 ng L-1, and dinotefuran recording a high concentration of 408 ng L-1. The observation indicated NNI concentration declined at sampling sites downstream of the YRB. Infants were identified as the most vulnerable to NNI exposure, with an estimated daily intake of 40.8 ng kg-1 bw d-1. The acute HC5 was determined at 946 ng L-1 and a chronic HC5 at 338 ng L-1, to NNI hazards. These findings highlight the urgent need for a more comprehensive understanding of the ecological implications and hazards posed by NNIs within the YRB. Variations in NNI concentrations across sites, potential risks to human health, and increased vulnerability of aquatic organisms from this study underscore the necessity for further research and concerted efforts to mitigate these ecological threats in the region.

Tracing the attenuation of fipronil and its transformation products from a rice paddy field to receiving rivers using polar organic chemical integrative samplers

Irrational use of fipronil for rice pest control often occurred, resulting in high concentrations of fipronil and its transformation products (TPs) (collectively termed fiproles) in aquatic sediment, calling for a better understanding of the migration and transformation of fipronil in surface water as well as efficient methods for source identification. Herein, the fate and transport of fiproles from a paddy field to receiving rivers were assessed in Poyang Lake basin, Jiangxi, China using polar organic chemical integrative samplers with mixed-mode adsorbents (POCIS-MMA). Average concentrations of fiproles in water were 6.16 ± 6.32 ng/L, with median, minimum, and maximum values being 2.99 ± 0.67, 0.40 ± 0.08, and 18.6 ± 3.1 ng/L, respectively. In all samples, over half of fiproles (55.9 %-90.8 %) presented in the form of TPs and fipronil desulfinyl was the dominant TP. Two approaches were applied for source identification, including the change of molar concentration ratios of fipronil to its TPs and the relative attenuation values of fiproles normalized to a reference compound (acetamiprid) that was stable in aquatic environment. While the paddy field upstream was the main source of waterborne fiproles, additional input sources in the downstream region were identified. The present study indicated that the combination of attenuation of molar concentration ratios of micro-pollutants to their respective TPs and relative attenuation values of micro-pollutants' concentrations normalized to a reference compound measured by POCIS is an effective means to study the migration and transformation of micro-pollutants in field.

Transport of neonicotinoid insecticides in a wetland ecosystem: Has the cultivation of different crops become the major sources?

Extensive application of neonicotinoid insecticides (NNIs) in agricultural production has resulted in widespread contamination of multiple environmental media. To investigate the occurrence and fate of NNIs in the largest marsh distribution area in Northeast China, an integrated ecosystem covering farmlands, rivers, and marshes, referred to as the farmland-river-marsh continuum in this study, was chosen for soil, water, and sediment sampling. Five NNIs were detected, with imidacloprid (IMI), thiamethoxam (THM), and clothianidin (CLO) being the most frequently detected ones in different samples. Concentrations of target NNIs in soil, surface water, and sediment samples were 2.23-136 ng/g dry weight (dw), 3.20-51.7 ng/L, and 1.53-8.40 ng/g dw, respectively. In soils, NNIs were detected more often and at higher concentrations in upland fields, while the concentration of NNIs in the soybean-growing soils (71.5 ng/g dw) was significantly higher than in the rice-growing soils (18.5 ng/g dw) (p < 0.05). Total concentration of NNIs in surface water was lower in the Qixing River channel than inside the marsh, while that in sediments showed an opposite trend. Total migration mass of IMI from approximately 157,000 ha of farmland soil by surface runoff was estimated to be 2636-3402 kg from the application time to the sampling period. The storage of NNIs in sediments was estimated to range from 45.9 to 252 ng/cm². The estimated environmental risks, calculated as the risk quotients (RQs), revealed low risks to aquatic organisms (RQs <0.1) from the residual concentrations of NNIs in water.

Experiments and simulation of adsorption characteristics of typical neonicotinoids in urban stream sediments

Sediment adsorption is one of the main environmental fates of neonicotinoids (NEOs) in aquatic environments. Little information is available on for the adsorption characteristics of NEOs on urban stream sediments. In this study, urban tidal stream sediments were collected to determine the adsorption properties of four selected NEOs. The influence of environmental factors on NEO adsorption was determined by the RSM-CCD method. The NEO adsorption rates on sediments were established by multiple regression equations. As a result, the adsorption of four NEOs onto sediments fitted a linear isotherm model. The adsorption amounts of thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI) were 1.68 to 2.24, 1.71 to 2.89, 1.88 to 3.07, and 2.23 to 3.16 mg/kg, respectively. The adsorption processes of four NEOs on urban sediments were favorable. Moreover, adsorption behaviors of NEOs were typical physical adsorption and readily adsorbed onto urban sediments. The adsorption processes of NEOs were exothermic reactions, and their adsorption rates decreased with increasing pH. Flow rates and organic matter contents could promote the adsorption ratios of typical NEOs. Multiple linear regression was used to assess the relationships between the adsorption rates of NEOs and environmental factors. The p-values of the fitting equations of adsorption rates were all less than 0.05. Within the ranges of concentration of the investigated factors, the multiple regression equations were able to reasonably model and predict the sorption of typical NEOs onto urban stream sediments. Therefore, the adsorption rate equations effectively predicted the NEO adsorption performance of urban streams and were helpful for controlling risk assessment of NEOs.

Integrate transcriptomic and metabolomic analysis reveals the underlying mechanisms of behavioral disorders in zebrafish (Danio rerio) induced by imidacloprid

Imidacloprid, a widely used neonicotinoid insecticide, poses a significant threat to aquatic ecosystems. Behavior is a functional indicator of the net sensory, motor, and integrative processes of the nervous system and is presumed to be more sensitive in detecting toxicity. In the present study, we investigated the behavioral effects of imidacloprid at the level of environmental concentrations (1, 10 and 100 μg/L) for a constant exposure to zebrafish adults, and performed the integrated transcriptomic and metabolomic analysis to analyze the molecular mechanism underlying behavioral effects of imidacloprid. Our results show that imidacloprid exposure significantly induce behavioral disruptions characterized by anxiety, depression, and reduced physiological function including exploratory, decision, social interaction and locomotor activity. Integrated transcriptomic and metabolomic analysis indicate that the disruption of circadian rhythm, metabolic imbalance of arginine and proline, and neurotransmitter disorder are the underlying molecular mechanisms of behavioral impairment induced by imidacloprid. The "gene-metabolite-disease" network consisted by 11 metabolites and 15 genes is associated human disease Alzheimer's disease (AD) and schizophrenia. Our results confirm the behavioral impairment induced by imidacloprid at environmental concentrations for constant exposure. The identified genes and metabolites can be used not only to illustrate the underlying mechanisms, but also can be developed as biomarkers in determining the ecological risk of imidacloprid to aquatic organisms even Homo sapiens.

Spatiotemporal distribution patterns and ecological risk of multi-pesticide residues in the surface water of a typical agriculture area in China

This study systematically investigated the occurrence, spatiotemporal distribution, and ecological risk of 106 pesticides in the surface water of the Jiaodong Peninsula in China. The results show that 52 pesticides, including 21 insecticides, 10 fungicides, and 21 herbicides, were detectable in the surface water. The concentrations of target pesticides in water samples ranged from 0.42 (tebuconazole in the wet season) to 645.31 ng/L (thiamethoxam in the normal season). The two most polluting and widespread pesticides were quintozene (maximum concentration of 481.46 ng/L and detection rate of 94 %) and atrazine (maximum concentration of 465.73 ng/L and detection rate of 100 %). The total pesticide concentrations in surface water in different seasons revealed the order of dry season > wet season > normal season. Based on aquatic pesticide concentrations, their frequency of occurrence, and effect concentrations, insecticides posed higher risks to aquatic organisms and human health than either fungicides or herbicides. Total pesticide concentrations were significantly positively correlated with suspended particulate matter, dissolved organic carbon, soil pH, normalized difference vegetation index, adjacent cropland area; and were negatively associated with adjacent grassland area. The cropland area largely influences pesticide distribution in the surface water of the Jiaodong Peninsula.

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

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

Occurrence, spatial distribution, and potential risks of organic micropollutants in urban surface waters from qinghai, northwest China

Lack of knowledge on the destiny of organic micropollutants (OMPs) in the Tibetan Plateau region of China prevents the public from being aware of the need for protecting these unique aquatic ecosystems that are precious water resources and source areas of the Yellow River. To address this knowledge gap, this study systematically investigated the multi-residue analysis, distribution, and potential risks of six types of OMPs, namely, neonicotinoid pesticides (NEOs), fungicides, organophosphate esters (OPEs), organophosphorus pesticides (OPPs), psychoactive substances (PSs), and antidepressants (ADs), in surface waters of major cities in Qinghai. A total of 31 compounds, consisting of 8 NEOs, 1 fungicide, 12 OPEs, 2 OPPs, 5 PSs, and 3 ADs, were detected in >50% of the sites, showing their ubiquitous nature in the study area. Results showed that the total OMP concentration in surface water was 28.3-908 ng/L, and OPEs were the dominant composition (48.6%-97.4%). The risk quotient values of the detected diazinon and dursban regularly exceeded 1 for aquatic organisms at all sampling sites, indicating moderate-high chronic ecological risk. The joint probability curves showed that dursban and NEOs have higher risk levels than other OMPs. Although the results of the non-carcinogenic total hazard quotient of the OMPs in the surface water was less than 1 in all age groups and the carcinogenic risk was lower than the negligible risk level, the potential risks to children and infants were considerably greater and should not be underestimated. In addition to pollutant concentration and exposure duration, ingestion rate and body weight (BW) are also important factors affecting health risk, with BW having a negative effect. To the best of the authors' knowledge, this report is the first to describe OMP pollution in Qinghai, and the results provide new insight into the ecological security of the water resources of the Tibetan Plateau.

Enhanced biodegradation of thiamethoxam with a novel polyvinyl alcohol (PVA)/sodium alginate (SA)/biochar immobilized Chryseobacterium sp H5

Long-term and extensive usage of thiamethoxam, the second-generation neonicotinoid insecticide, has caused a serious threat to non-target organisms and ecological security. Efficient immobilized microorganism techniques are a sustainable solution for bioremediation of thiamethoxam contamination. A Gram-negative aerobic bacterium Chryseobacterium sp H5 with high thiamethoxam-degrading efficiencies was isolated from activated sludge. Then we developed a novel polyvinyl alcohol (PVA)/sodium alginate (SA)/biochar bead with this functional microbe immobilization to enhance the biodegradation and removal of thiamethoxam. Results indicated that the total removal and biodegradation rate of thiamethoxam with PVA/SA/biochar (0.7 %) beads with Chryseobacterium sp H5 immobilization at 30 °C and pH of 7.0 within 7 d reached about 90.47 % and 68.03 %, respectively, much higher than that using PVA/SA immobilized microbes (75.06 %, 56.05 %) and free microbes (61.72 %). Moreover, the PVA/SA/biochar (0.7 %) immobilized microbes showed increased tolerance to extreme conditions. Biodegradation metabolites of thiamethoxam were identified and two intermediates were first reported. Based on the identified biodegradation intermediates, cleavage of C-N between the 2-chlorothiazole ring and oxadiazine, dichlorination, nitrate reduction and condensation reaction would be the major biodegradation routes of thiamethoxam. Results of this work suggested the novel PVA/SA/biochar beads with Chryseobacterium sp H5 immobilization would be helpful for the effective bioremediation of thiamethoxam contamination.

Effect of thiamethoxam on the behavioral profile alteration and toxicity of adult zebrafish at environmentally relevant concentrations

Thiamethoxam (THM) is a commercial neonicotinoid insecticide with broad-spectrum insecticidal activity. It has been widely detected in the aquatic environment, but its behavioral toxicity on aquatic organisms received limited attention. In this study, adult zebrafish were exposed to THM at three levels (0.1, 10, and 1000 μg/L) for 45 days to investigate its effect on their ecological behavior, histopathology, bioaccumulation, and stress response. The bioconcentration factor in zebrafish brain was significantly higher (p < 0.05) at low concentration of THM (0.1 μg/L) than in other treatment groups. In terms of individual behavior, the locomotor activity, aggregation, and social activity of fish were enhanced after THM exposure, but the memory of the food zone was disturbed and abnormal swimming behavior was observed. THM exposure caused brain tissue necrosis, erythrocyte infiltration, cloudy swelling, and other pathological changes in brain tissue and affected the concentrations of acetylcholinesterase and cortisol related to neurotoxicity. The condition factor and organ coefficients (brain, heart, and intestine) of zebrafish were markedly impacted by THM treatment at 0.1 and 1000 μg/L, respectively. This finding showed that THM was more harmful to fish behavior than lethality, reproduction, and growth, and a behavioral study can be a useful tool for ecological risk assessment.

Tuning of (E)-(4-fluorophenyl)-1,1-diamino-2,3-diazabuta-1,3-diene nanostructures for the selective detection of imidacloprid

The present work demonstrates a facile route for synthesizing the organic nanoparticles (ONPs) and the blue fluorescent Quantum Dots (QDs) based on an organic molecule named (E)-(4-fluorophenyl)-1,1-diamino-2,3-diazabuta-1,3-diene. The synthesis process possesses advantages viz green synthesis, non-toxic degraded products, and amount of organic compound. Initially, the ONPs were prepared using the nanoprecipitation method and were screened for their recognition potential against various pesticides, however, no selectivity has been observed. This motivated us to tune the ONPs into QDs. The QDs were prepared using the hydrothermal method and a color change was observed in the QDs solution under daylight and under a UV lamp. The emission wavelength was observed at 400 nm (λexcitation = 278 nm). The synthesized QDs exhibited selective sensing potential towards imidacloprid via a quenching mechanism. A normalised decrement in the luminescence intensity of QDs was observed on raising the concentration of imidacloprid and a good linear response was noticed over a concentration varies from 1 μM to 100 μM with a regression coefficient of 0.99. The detection limit was estimated to be 4.53 nM and quantification limit was calculated to be and 13.72 nM.

Neonicotinoid insecticides promote breast cancer progression via G protein-coupled estrogen receptor: In vivo, in vitro and in silico studies

Neonicotinoid insecticides (NIs) have been widely detected in environmental media and human body with concentrations reaching hundreds of nanomolar to micromolar levels. However, the information about their human health toxicology and mechanism is deficient. Previous studies have implied that NIs might exert estrogenic disruption and promote breast cancer progression, but the molecular mechanism is unclear, especially the molecular initiating event. G protein-coupled estrogen receptor (GPER), as a candidate therapeutic target, plays vital roles in the development of breast cancer. This work aimed to reveal the potential mechanism through GPER pathway. Firstly, we screened the activities of seven most common NIs on GPER signal pathway by calcium mobilization assay. Clothianidin, acetamiprid (ACE), and dinotefuran activated GPER most potently and ACE displayed the highest agonistic activity with the lowest observed effective concentration (LOEC) of 1 μM. The molecular docking and dynamics simulation showed favored interaction trend between the NIs and GPER. The three NIs with GPER activity induced 4T1 breast cancer cells migration and ACE showed the highest potency with LOEC of 100 nM. ACE also induced 4T1 cells proliferation at high concentration of 50 μM and up-regulated GPER expression in a dose-dependent manner. We speculated that both the induction effects of ACE on 4T1 cells proliferation and migration might be owing to the activation and up-regulation of GPER. By using 4T1-Luc cells injected orthotopic tumor model, we found that ACE also promoted in-situ breast cancer growth and lung metastasis in normal mouse dependent on GPER. However, ACE only promoted in-situ breast cancer growth through GPER but not lung metastasis in ovariectomized mice, implying that the ACE-induced lung metastasis should be related to endogenous estrogen from ovary. Overall, we demonstrated that NIs promoted breast cancer progression via GPER pathway at human related exposure levels and their female health risks need urgent concerns.

Predicting and assessing the toxicity and ecological risk of seven widely used neonicotinoid insecticides and their aerobic transformation products to aquatic organisms

Neonicotinoid insecticides (NIs) are widely used worldwide, accounting for 25 % of the global insecticide market, and are easily transported into surrounding aquatic ecological environments after application. At present, >80 % of surface water is contaminated by NIs globally. Some transformation products (TPs) of NIs can exhibit greater toxicity to aquatic organism than their parent products. However, few studies have evaluated the toxicity and ecological risk of the TPs of NIs. In this study, we aimed to assess the toxicity and ecological risk of seven widely used NIs and their aerobic TPs to aquatic organisms using a prediction method. We found that partial aerobic TPs of NIs have greater toxicity to aquatic organisms than their parent products, and some of them could severely damage aquatic ecosystems. Meanwhile, acetamiprid, thiacloprid, and several other TPs of NIs with a chlorinated ring structure showed strong bioconcentration abilities, which could potentially harm aquatic organisms through the food chain. Moreover, the widespread use of NIs has certain aquatic ecological risks, which should be controlled and limited. This study comprehensively evaluated the ecological risk of seven widely used NIs and their aerobic TPs to aquatic organisms for the first time. Our results could provide an important reference for assessment of the aquatic environmental risk posed by NIs and pollution control.

Long-Term Exposure to Neonicotinoid Insecticide Acetamiprid at Environmentally Relevant Concentrations Impairs Endocrine Functions in Zebrafish: Bioaccumulation, Feminization, and Transgenerational Effects

Neonicotinoid insecticides have attracted worldwide attention due to their ubiquitous occurrence and detrimental effects on aquatic organisms, yet their impacts on fish reproduction during long-term exposure remain unknown. Here, zebrafish (F0) were exposed to a neonicotinoid, acetamiprid, at 0.19-1637 μg/L for 154 d. Accumulation and biotransformation of acetamiprid were observed in adult fish, and the parent compound and its metabolite (acetamiprid-N-desmethyl) were transferred to their offspring. Acetamiprid caused slight survival reduction and significant feminization in F0 fish even at the lowest concentration. Hormone levels in F0 fish were remarkedly altered, that is, gonad 17β-estradiol (E2) significantly increased, while androstenedione decreased. The corresponding transcription of steroidogenic genes (ar, cyp19b, fshβ, gnrh2, gnrh3, and lhβ) were significantly upregulated in the brain and gonad of the females but downregulated in the males. The vtg1 gene expression in the liver of male fish was also upregulated. In addition to F0 fish, parental exposure to acetamiprid decreased hatchability and enhanced malformation of F1 embryos. Chronic exposure to acetamiprid at environmentally relevant concentrations altered hormone production and the related gene expression of the hypothalamic-pituitary-gonad (HPG) axis in a sex-dependent way, caused feminization and reproductive dysfunction in zebrafish, and impaired production and development of their offspring.

Carbon nanotube-passive samplers as novel tools for sampling and determining micropollutants in the aquatic environment

Passive sampling is an interesting and cost-effective strategy for the quantification of micropollutants in the aquatic environment. When combined especially with a sensitive analytical method such as liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS), the use of passive sampling devices (PSDs) enables long-term and reliable determination of a wide range of chemicals. In this study, carbon nanotubes (CNTs) were used as an innovative sorbent in POCIS-like samplers (Polar Organic Chemical Integrative Sampler). The developed CNTs-PSDs were calibrated by the flow-through method and the obtained sampling rates (R_s) of analytes were compared with the previously obtained R_s values using the semi-static method. Subsequently, passive samplers were placed in the Baltic Sea, the Nogat River, and the Sztumskie Pole Lake in order to sample and concentrate 28 chemical compounds belonging to the group of contaminants of emerging concern (CECs). For the first time, the effectiveness of the use of CNTs-PSDs in the field was proven by the quantification of carbamazepine, diclofenac, p-nitrophenol, bisphenol A, 3,5-dichlorophenol, 17-β-estradiol, 17-α-ethinylestradiol and metoprolol in the tested surface waters. The obtained time-weighted average (TWA) concentrations of analytes ranged from 0.22 ± 0.12 ng/L (for metoprolol in the Nogat River) to 32.1 ± 2.4 ng/L (for bisphenol A in the Sztumskie Pole Lake). More importantly, CNTs-PSDs determined a greater amount of micropollutants than grab sampling and solid-phase extraction (SPE), which proves the advantage of passive sampling over grab sampling, especially when monitoring contaminants in the aquatic environment at low concentration levels.

A review of spatiotemporal patterns of neonicotinoid insecticides in water, sediment, and soil across China

Neonicotinoid insecticides (NNIs) have been widely used to control insect pests, while their environmental residues and associated hazardous impacts on human and ecosystem health have attracted increasing attention worldwide. In this study, we examined the current levels and associated spatial and temporal patterns of NNIs in multiple environmental media across China. Concentrations of NNIs in surface water, sediment, and soil were in the range of 9.94-755 ng·L^-1, 0.07-8.30 ng·g^-1 DW, and 0.009-356 ng·g^-1 DW, respectively. The high levels of NNIs in surface water, such as in Yangtze River (755 ng·L^-1), North River (539 ng·L^-1), Nandu River (519 ng·L^-1), and Minjiang River (514 ng·L^-1), were dominated by imidacloprid, thiamethoxam, and acetamiprid due to their extensive use. The levels of NNIs in sediments were relatively low, and the highest concentration (8.30 ng·g^-1 DW) was observed in Dongguan ditch. Sediment-water exchange calculated from fugacity fraction indicated that NNIs in sediment can be released back into the water due to their high solubility and low K_OW. Soils from agricultural zones contained the largest residual NNIs, with imidacloprid concentrations in cultivated soil reaching 119 ng·g^-1 DW. The calculated leaching potential showed that clothianidin has the highest migration potential to deep soil or groundwater. The monitored data of NNIs presented a decreasing trend from 2016 to 2018, which might be caused by the implementation of relevant control policies for NNI applications. The high levels of NNIs mainly occurred in southern China due to frequent agricultural activities and warm and humid meteorological conditions. The results from this study improve our understanding of the pollution levels and environmental behavior of NNIs in different environmental media across China and provide new knowledge that is needed for making future control policies for NNIs production and application.

Greenhouse production contributes to pesticide occurrences in Swedish streams

Greenhouse and other covered cultivation systems have increased globally over the past several decades, leading to considerably improved product quality and productivity per land area unit. However, there is a paucity in information regarding the environmental impacts of covered production systems, especially regarding pesticides entering the surrounding environment. Aiming to address this knowledge gap, we collected grab samples downstream of greenhouses from seven Swedish streams every 14 days during a 12 month period. In three of the streams, samples were also taken upstream of the greenhouses and in four of the streams time-integrated samples were collected by TIMFIE samplers in the period between grab sampling occasions. The samples were analyzed for 28 substances (27 that were permitted for use in greenhouse production systems in Sweden and one degradation product to a permitted substance). Pesticide use journals were collected from the greenhouse producers for the 12 month period. The results were examined for indications of greenhouse contributions to detection frequencies, maximum and average concentrations, and potential ecotoxicicity in several ways: (1) comparing locations downstream of greenhouses with registered use of a substance with those without registered use, (2) comparing results from this study with those from the Swedish environmental monitoring program of pesticides in surface water from catchments with no greenhouses from the same period and region, (3) comparing concentration trends with registered pesticide application times in the greenhouses, and (4) comparing up- and downstream concentrations. The results strongly suggest that greenhouse applications do contribute to pesticide occurrences, maximum and median concentrations for most of the pesticides included in this study, and to potential toxicity to aquatic organisms for several of them, most notably imidacloprid, acetamiprid, carbendazim, and pirimicarb.

Point or non-point source: Toxicity evaluation using m-POCIS and zebrafish embryos in municipal sewage treatment plants and urban waterways

Municipal sewage treatment plants (STPs) have been regarded as an important source of organic contaminants in aquatic environment. To assess the impact of STPs on occurrence and toxicity of STP-associated contaminants in receiving waterways, a novel passive sampler modified from polar organic chemical integrative sampler (m-POCIS) was deployed at the inlet and outlet of a STP and several upstream and downstream sites along a river receiving STP effluent in Guangzhou, China. Eighty-seven contaminants were analyzed in m-POCIS extracts, along with toxicity evaluation using zebrafish embryos. Polycyclic musks were the predominant contaminants in both STP and urban waterways, and antibiotics and current-use pesticides (e.g., neonicotinoids, fiproles) were also ubiquitous. The m-POCIS extracts from downstream sites caused significant deformity in embryos, yet the toxicity could not be explained by the measured contaminants, implying the presence of nontarget stressors. Sewage treatment process substantially reduced embryo deformity, chemical oxygen demand, and contamination levels of some contaminants; however, concentrations of neonicotinoids and fiproles increased after STP treatment, possibly due to the release of chemicals from perturbed sludge. Source identification showed that most of the contaminants found in urban waterways were originated from nonpoint runoff, while cosmetics factories and hospitals were likely point sources for musks and antibiotics, respectively. Although the observed embryo toxicity could not be well explained by target contaminants, the present study showed a promising future of using passive samplers to evaluate chemical occurrence and aquatic toxicity concurrently. Zebrafish embryo toxicity significantly decreased after sewage treatment, but higher toxicity was observed for downstream samples, demonstrating that urban runoff may produce detrimental effects to aquatic life, particularly in rainy season. These results highlight the relevance of monitoring nonpoint source pollution along with boosting municipal sewage treatment infrastructure.

Development of an analytical method based on solid-phase extraction and LC-MS/MS for the monitoring of current-use pesticides and their metabolites in human urine

Pyrethroids, organophosphorus pesticides and fipronil have been listed as priority chemicals in human biomonitoring studies because of their wide use and potential health effects in humans. The determination of 13 pesticides, including pyrethroids (deltamethrin, cypermethrin, permethrin, cyfluthrin, bifenthrin), organophosphorus (chlorpyrifos, chlorpyrifos-methyl, and malathion), fipronil, neonicotinoids (imidacloprid, acetamiprid and thiacloprid) and triazole (prothioconazole), together with 13 corresponding metabolites in human urine samples was achieved by solid-phase extraction and analysis by liquid chromatography coupled to tandem mass spectrometry. All targeted compounds, except malathion dicarboxylic acid, were measured with a mean within-accuracy (n = 5) of 71%-114% (RSD: 1%-14%) and between-run (n = 15) accuracy of 80%-118% (RSD: 2%-14%). Limits of quantitation of the targeted analytes ranged from 0.1 to 16 pg/mL. The detection result of urine samples from 25 volunteers indicated that the detection frequencies of 3,5,6-trichloro-2-pyridinol (median: 448 pg/mL), 6-chloropyridine-3-carboxylic acid (median: 193 pg/mL), 2-methyl-3-phenylbenzoic acid (median: 181 pg/mL), 3-phenoxybenzoic acid (median: 99 pg/mL), 2-isopropyl-6-methyl-4-pyrimidinol (median: 77 pg/mL), cyfluthrin (median: 59 pg/mL), cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (cis-DCCA, median: 53 pg/mL), trans-DCCA (median: 25 pg/mL), prothioconazole (median: 21 pg/mL), imidacloprid (median: 7 pg/mL), and prothioconazole-desthio (median: 1 pg/mL) were > 50%. The obtained results show that the validated method is suitable for the human biomonitoring of these current-use pesticides and their metabolites.

Multimedia distributions and the fate of microcystins from freshwater discharge in the Geum River Estuary, South Korea: Applicability of POCIS for monitoring of microalgal biotoxins

Here, we investigated the characteristics of the environmental multimedia distribution of microcystins (MCs) introduced from freshwater discharge through the estuary dam of the Geum River. In addition, the applicability of a passive sampling device (polar organic chemical integrative sampler, POCIS) for monitoring MCs was evaluated. Surface water, suspended solids (SS), sediments, and oysters were collected from the inner and outer estuary dam. Seven MC variants were analyzed using HPLC-MS/MS. POCIS was deployed at three sites over one week, and MCs were monitored for four weeks from August to September 2019. Before POCIS was deployed in the field, compounds-specific sampling rates of MCs were determined as functions of water temperature (10, 20, and 30 °C), flow rate (0, 0.38, and 0.76 m s^-1), and salinity (0, 15, and 30 psu) in the laboratory. The sampling rates of MCs in POCIS increased significantly with increasing water temperature and flow rate, whereas salinity did not significantly affect the sampling rates between freshwater and saltwater. The MCs in the Geum River Estuary mainly existed as particulate forms (mean: 78%), with relatively low proportions of dissolved forms (mean: 22%), indicating that MCs were mainly contained in cyanobacterial cells. There was no significant correlation among the concentrations of MCs in water, SS, sediments, and oysters. Time-weighted average concentrations of MCs from POCIS were not significantly correlated with the concentrations of MCs in water and oysters. The metabolites of MCs, including MC-LR-GSH, MC-LR-Cys, MC-RR-GSH, and MC-RR-Cys, were detected in oysters (no metabolites were detected in POCIS). Overall, POCIS can be useful for monitoring dissolved MCs in the aquatic ecosystem, particularly in calculating time-weighted average concentrations, but it seems to have limitations in evaluating the contamination status of total MCs, mainly in particulate form.

Selected transformation products of neonicotinoid insecticides (other than imidacloprid) in drinking water

Several transformation products (or metabolites) of neonicotinoid insecticides (NNIs) have been detected in drinking water, such as desnitro-imidacloprid and imidacloprid-urea. However, data on the occurrences of the metabolites of NNIs (mNNIs) in drinking water are mainly limited to the imidacloprid metabolites. To identify whether the potential metabolites of other widely used NNIs (such as acetamiprid, clothianidin, and thiamethoxam) occur in drinking water and to characterize their distribution profiles, twelve selected (mainly urea and desnitro/decyano) metabolites of NNIs were measured in drinking water samples (n = 884, including n = 789 for tap water, and n = 95 for shallow groundwater) that were collected from 32 provinces in mainland China and Hong Kong. Nearly 90% of the drinking water samples contained the detected mNNI residues. Among the selected mNNIs, thiamethoxam-urea (THM-urea: 76%) and decyano-acetamiprid (decyano-ACE: 73%) were frequently detected (median: 0.94 and 0.25 ng/L, respectively), which were followed by clothianidin-urea (CLO-urea: 45%), desnitro-thiamethoxam (DN-THM: 38%), and other mNNIs (detected in less than 30% of the water samples). Surface-water-sourced tap water had an approximately 8-10 times higher median cumulative concentration (ng/L) of the selected mNNIs (ΣmNNIs: 3.88) than the deep groundwater-sourced tap water (0.53) and groundwater that was directly used as drinking water (0.38). Higher ratios of THM-urea accounted for ΣTHM in north and northwest China than in south China could be partly explained by the decreasing soil pH values from north to south in China. The higher ratios of decyano-ACE accounted for ΣACE in south China than in north and northwest China could be attributable to the lower soil pH levels, higher temperatures, and greater light intensities in south China. The THM-urea, decyano-ACE, and ΣmNNIs levels in cities were found to be significantly higher than those in nonurban areas. The THM-urea levels in seven drinking water samples from Guangxi and Henan Provinces exceeded the guideline limit (100 ng/L) of the European Union. This is the first study to identify THM-urea, decyano-ACE, CLO-urea, and DN-THM in drinking water. To better assess the mass loadings of NNIs in drinking water, mNNIs should be considered in further studies.

Occurrence, variations, and risk assessment of neonicotinoid insecticides in Harbin section of the Songhua River, northeast China

Neonicotinoid insecticides (NNIs) have been intensively used and exploited, resulting in their presence and accumulation in multiple environmental media. We herein investigated the current levels of eight major NNIs in the Harbin section of the Songhua River in northeast China, providing the first systematic report on NNIs in this region. At least four NNIs in water and three in sediment were detected, with total concentrations ranging from 30.8 to 135 ng L^-1 and from 0.61 to 14.7 ng g^-1 dw, respectively. Larger spatial variations in surface water NNIs concentrations were observed in tributary than mainstream (p < 0.05) due to the intensive human activities (e.g., horticulture, urban landscaping, and household pet flea control) and the discharge of wastewater from many treatment plants. There was a significant positive correlation (p < 0.05) between the concentrations of residual imidacloprid (IMI), clothianidin (CLO), and Σ₄NNIs in the sediment and total organic carbon (TOC). Due to its high solubility and low octanol-water partition coefficient (K _ow), the sediment-water exchange behavior shows that NNIs in sediments can re-enter into the water body. Human exposure risk was assessed using the relative potency factor (RPF), which showed that infants have the highest exposure risk (estimated daily intake (ΣIMI_eq EDI): 31.9 ng kg^-1 bw·d^-1). The concentration thresholds of NNIs for aquatic organisms in the Harbin section of the Songhua River were determined using the species sensitivity distribution (SSD) approach, resulting in a value of 355 ng L^-1 for acute hazardous concentration for 5% of species (HC₅) and 165 ng L^-1 for chronic HC₅. Aquatic organisms at low trophic levels were more vulnerable to potential harm from NNIs.

Occurrence, spatiotemporal distribution, and risk assessment of current-use pesticides in surface water: A case study near Taihu Lake, China

This study involved the monitoring and risk assessment of current-use pesticides in surface water from the northwestern section of the Taihu Lake Basin (China) in 2019. In particular, 114 current-use pesticides were measured in samples collected during four campaigns spread across the wet, dry, and normal seasons. Pesticide concentrations were measured by means of a novel analytical method involving online solid-phase extraction coupled to LC-MS/MS. In total, 1 plant growth regulator, 34 herbicides, 23 insecticides, and 25 fungicides were detected. Detection frequencies greater than 90% were recorded for 26 pesticides; furthermore, acetamiprid, azoxystrobin, bentazone, carbendazim, isoprothiolane, metolachlor, paclobutrazol, and triadimenol were present in every sample. The measured pesticide concentrations varied widely, from below the detection limit to 10,600 ng/L (tricyclazole). The highest median concentrations for the fungicide, herbicide, and insecticide families were observed for carbendazim (135 ng/L), metolachlor (40 ng/L), and imidacloprid (31 ng/L), respectively. Twenty-two pesticides were quantitatively reported in Chinese surface water for the first time. The number and concentration of detected pesticides were significantly higher in June and September (wet season) compared to March and December (dry season). Agricultural areas of the study area were more contaminated than the residential and industrial sections. Imidacloprid was the only pesticide that exhibited high risk to sensitive ecological species (RQ_median > 1) in all four seasons. Isoproturon, isoprothiolane, and pretilachlor were identified as high risk in March (RQ_median = 4.5), September (1.3), and June (1.1), respectively; moreover, another eight pesticides posed a high ecological risk at specific sites. Seven pesticides recorded moderate risks (i.e., RQ_median = 0.1-1.0). Of the 18 pesticides with cases of high risk, a novel risk index, which accounted for frequency of PNEC exceedance, ranged from 6.7 (imidacloprid) to 7.1 × 10^-5 (propiconazole). The integrated consideration of ecological risk and frequency of risk inform priorities for regional pesticide management and control.

Tracing neonicotinoid insecticides and their transformation products from paddy field to receiving waters using polar organic chemical integrative samplers

Neonicotinoid insecticides are ubiquitous in surface water worldwide, yet the transportation and transformation of these compounds in aquatic environment remain unclear. In the present study, polar organic chemical integrative sampler with mixed-mode adsorbents (POCIS-MMA) was developed for simultaneously tracing environmental fate of seven neonicotinoids and 10 transformation products (TPs) from a paddy field to receiving waters in Poyang Lake basin, Jiangxi, China. All neonicotinoids (5.20 ± 0.75‒866 ± 143 ng/L) and seven TPs (116 ± 4‒334 ± 78 ng/L) were detected, demonstrating widespread occurrence of these insecticides in aquatic environment. Dinotefuran (up to 802 ± 139 ng/L) and its TP, 1-methyl-3- (tetrahydro-3-furylmethyl) guanidium dihydrogen (DN) (103 ± 4‒320 ± 76 ng/L) were the dominant neonicotinoids and TPs with mean concentrations of 200 ± 296 and 208 ± 58 ng/L, respectively. Spatial attenuation of neonicotinoids stretched downstream along the rivers, while TP concentrations firstly increased (D1‒S6) and then kept constant (S7‒S16) from upstream to downstream. Though paddy field was the main source of neonicotinoids, additional input sources downstream were identified by analyzing the composition of neonicotinoids and their TPs. Our study highlighted the applicability of POCIS-MMA passive sampling to investigate the transportation and transformation of neonicotinoids in agricultural waterways.

The neonicotinoid alternative sulfoxaflor causes chronic toxicity and impairs mitochondrial energy production in Chironomus kiinensis

Unintentional environmental consequences caused by neonicotinoids reinforce the development of safer alternatives. Sulfoxaflor is considered such an alternative. However, ecological risk of sulfoxaflor remains largely unknown. Here, we investigated the acute and chronic toxicity of sulfoxaflor to a benthic invertebrate, Chironomus kiinensis. Sulfoxaflor showed lower lethality than imidacloprid to midges, with LC50 values of 84.1 (81.5-87.3), 66.3 (34.8-259), and 47.5 (29.5-306) μg/L for 96-h, 10-d, and 23-d exposures, respectively. Conversely, sulfoxaflor significantly inhibited C. kiinensis growth and emergence in chronic exposures when concentrations were above 20 μg/L. Effects on energy production were assessed through in vitro tests using mitochondria isolated from C. kiinensis. Sulfoxaflor disrupted mitochondrial state-3 respiration, meanwhile, adenosine triphosphatase (ATPase) activity and adenosine triphosphate (ATP) production were both inhibited in a dose-dependent manner. The observed mitochondrial dysfunction may be related to the decreased organismal growth and emergence, which could further influence biodiversity. Interestingly, sulfoxaflor uptake in C. kiinensis was detected even after emergence, implying its potential to be transported along food webs and among environmental compartments. This study provides thorough investigations on the toxicity of an emerging neonicotinoid alternative to Chironomidae. Data derived from the current study are useful to inform future ecological risk assessment and benefit problem-solving to the overall agriculture-environment nexus.

Joint toxicity of imidacloprid and azoxystrobin to Chironomus dilutus at organism, cell, and gene levels

Pesticides occur in the environment as mixtures, yet the joint toxicity of pesticide mixtures remains largely under-explored and is usually overlooked in ecological risk assessment. In the current study, joint toxicity of a neonicotinoid insecticide (imidacloprid, IMI) and a strobilurin fungicide (azoxystrobin, AZO) was investigated with Chironomus dilutus over a wide range of concentrations and at different effect levels (organism, cell, and gene levels). The two pesticides, both individually and in combination, were found to induce oxidative stress and cause lethality in C. dilutus. Median lethal concentrations for IMI and AZO were 3.98 ± 1.17 and 52.9 ± 1.1 μg/L, respectively. Mixtures of the two pesticides presented synergetic effects at environmentally relevant concentrations whilst antagonistic effects at high concentrations, showing concentration-dependent joint toxicity. Investigation on the expressions of 12 genes (cyt b, coi, cox1, cyp4, cyp12m1, cyp9au1, cyp6fv1, cyp315, gst, Zn/Cu-sod, Mn-sod, and cat) revealed that the two pesticides impaired mitochondrial respiration, detoxification, and antioxidant system of C. dilutus, and the joint effects of the two pesticides were likely due to an interplay between their respective influences on these physiological processes. Collectively, the synergistic effects of the two pesticides at environmentally relevant concentrations highlight the importance to incorporate combined toxicity studies into ecological risk assessment of pesticides.

High Tolerance and Delayed Responses of Daphnia magna to Neonicotinoid Insecticide Imidacloprid: Toxicokinetic and Toxicodynamic Modeling

Species sensitivity to neonicotinoids has been shown to be highly variable among aquatic invertebrates. Toxicokinetic and toxicodynamic (TKTD) models were constructed to mechanistically elucidate the susceptibility of Daphnia magna to imidacloprid. D. magna was highly tolerant to single short-term exposure to imidacloprid (96-h LC50 of 8.47 μg/mL), but delayed and carry-over toxicity occurred under repeated pulse exposures. Kinetic distribution of imidacloprid between exoskeleton and soft tissues of D. magna was evaluated using a newly developed method. Approximately 84% imidacloprid was distributed to soft tissues but was rapidly depurated from the tissue (t_1/2 of 1.2 h), resulting in low bioaccumulation and high tolerance. TKTD modeling also successfully simulated the survival of D. magna after pulsed exposures. The calculated recovery time was 45 d, indicating significant delayed and carry-over toxicity of the insecticide. While complete elimination of imidacloprid only took about 5 h (TK), slow damage recovery (45 d) caused slow organism recovery (TD). Consequently, although D. magna was tolerant to imidacloprid due to fast depuration from soft tissue, long damage recovery time significantly enhanced the toxicity under repeated pulse exposures. Our study highlights the necessity of integrating delayed and carry-over toxicity quantification in assessing the risk of neonicotinoids to aquatic invertebrates.

Fiproles as a proxy for ecological risk assessment of mixture of fipronil and its degradates in effluent-dominated surface waters

Environmental risk assessment of complex chemical mixtures has increasingly been prioritized as a management goal, especially in the regulatory sector. Although fipronil and its three degradates (-sulfone, -sulfide and -desulfinyl) have been frequently quantified in waterways, little information is available about the likelihood and magnitude of ecological risk posed by these chemical mixtures - collectively known as fiproles - in surface water. In the present study, a probabilistic risk assessment of mixtures of fipronil and its three degradates was conducted for three effluent-dominated southern California rivers: Los Angeles River (LAR), San Gabriel River (SGR) and Santa Clara River (SCR), California, USA. The assessments, which used fiproles as an integrated proxy, were based on three levels of toxicity endpoints: median lethal concentration (LC50), half-maximal effective concentration (EC50), and lowest observed effect concentration (LOEC), to gain comprehensive assessment information. Probabilistic approaches based on species sensitivity distribution (SSD) and exposure concentration distribution (ECD) were developed with the log-logistic model by pooling the toxicity and occurrence data, respectively. The 5th percentile hazardous concentrations (HC5s) were calculated to be at low parts per billion levels, enabling these values to be used to estimate the chemical-specific benchmarks for components that lack ecotoxicity data. The single substance potentially affected fraction (ssPAF) of fiproles revealed risk levels for the three rivers in descending order: LAR ≥ SGR > SCR. The overall risk probability estimated from the joint probability curve (JPC) by Monte Carlo simulation was 1.13 ± 0.20% (LC50), 9.31 ± 1.46% (EC50), and 6.58 ± 1.43% (LOEC) for the three rivers collectively. These results derived from the fiproles indicates that fipronil and its degradates pose risks to the aquatic organisms in the surface water of the three rivers. The present study provides a methodology for the use of a proxy in the risk assessment of chemical mixtures.

Pesticide occurrence and persistence entering recreational lakes in watersheds of varying land uses

Currently little is known of newer pesticide classes and their occurrence and persistence in recreational lakes. Therefore, the objectives of this study were to (1) assess average pesticide concentrations and loadings entering recreational lakes in three mixed land use watersheds throughout the growing season, (2) evaluate pesticide persistence longitudinally within the lakes, and (3) perform an ecotoxicity assessment. Six sampling campaigns were conducted at three lakes from April through October 2018 to measure the occurrence and persistence during pre, middle, and post growing season. Polar organic chemical integrative samplers (POCIS) were placed in streams near lake inlets and monthly samples were collected for analysis of twelve pesticides. Additional monthly grab water samples were taken at each POCIS location and at the midpoint and outlet of each lake. All pesticide samples were analyzed using liquid chromatography/tandem mass spectrometry (LC/MS/MS) and individual pesticide loading rates were determined. Occurrence and persistence of specific pesticides were significantly different between lakes in varying watershed land uses. Specifically, the recreational lake receiving predominately urban runoff had the highest load of pesticides, likely in the form of biocides, entering the waterbody. Concentrations of imidacloprid exceeded acute and chronic invertebrate levels for 11% and 61% of the sampling periods, respectively, with the recreational lake receiving predominately urban runoff having the most occurrences. Findings from this study are critical for preventing and mitigating potential effects of pesticides, specifically applied as biocides in urban landscapes, from entering and persisting in recreational lakes.

Residual concentrations and ecological risks of neonicotinoid insecticides in the soils of tomato and cucumber greenhouses in Shouguang, Shandong Province, East China

Neonicotinoid insecticides (NNIs) are the most widely used insecticides in China and worldwide. Continuous use of NNIs can lead to their accumulation in soil, causing potential ecological risks due to their relatively long half-life. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to investigate the residual levels of nine neonicotinoids in greenhouse soils in Shouguang, East China, at different soil depths and with different crops (tomato and cucumber) after varying periods of cultivation. Seven neonicotinoids were detected in the soils of the tomato greenhouses and six were detected in the soils of the cucumber greenhouses, with total concentrations ranging from 0.731 to 11.383 μg kg^-1 and 0.363 to 19.224 μg kg^-1, respectively. In all samples, the neonicotinoid residues in the soils cultivated for 8-9 years were lower than in those cultivated for 2 years and 14-17 years. In the tomato greenhouse soils, the residual levels of NNIs were highest in the topsoil, with progressively lower concentrations found with depth. Under cucumber cultivation, the NNI residue levels were also highest in the topsoil but there was little difference between the middle and lower soil layers. Total organic carbon (TOC) decreased with soil depth while pH showed the opposite trend, showing a significant negative correlation in both types of soils (tomato soils ρ = -0.900, p = .001; cucumber soils ρ = -0.883, p = .002). Furthermore, TOC was significantly positively correlated, and pH was negatively correlated, with total NNI concentrations in both types of soils (TOC: tomato soils ρ = 0.800, p = .010; cucumber soils ρ = 0.881, p = .004; pH: tomato soils ρ = -0.850, p = .004; cucumber soils ρ = -0.643, p = .086). The results of an ecological risk analysis showed that acetamiprid represents a particularly high toxicity risk in these soils. Based on our analysis, NNI residues in the soils of tomato greenhouses and their associated ecological risks deserve more attention than those of cucumber greenhouse soils.

A new configuration of polar organic chemical integrative sampler with nylon membranes to monitor emerging organophosphate ester contaminants in urban surface water

Organophosphate ester contaminants, including organophosphate pesticides (OPPs) and organophosphate flame retardants (OPFRs) are ubiquitous in surface water and pose a significant risk to aquatic organisms, thus it is important to develop effective methods for long-term monitoring of these emerging compounds. Polar organic chemical integrative sampler (POCIS) has become a promising monitoring tool for waterborne contaminants, yet recent studies found that the commonly used polyethersulfone (PES) membrane strongly sorbed some moderately hydrophobic compounds, resulting in long lag-phase for chemical accumulation in POCIS. In the present study, 0.45-μm nylon membranes was selected as POCIS diffusion-limiting membrane to design a new POCIS-Nylon configuration for analyzing moderately hydrophobic OPPs and OPFRs in water. The POCIS-Nylon had negligible lag-phase due to low sorption of OPPs and OPFRs to nylon membrane. Meanwhile, linear accumulation time and sensitivity for target contaminants using POCIS-Nylon retained similar to the traditional POCIS. Water velocity and chemical concentration had little impact on sampling rate (R_s), validating that the POCIS-Nylon was suitable for various water conditions. Finally, the occurrence of OPPs and OPFRs in urban waterways of Guangzhou, China was evaluated using the POCIS-Nylon with R_s values that were calibrated in the laboratory. The average concentration of OPPs was 4.97 ± 1.35 ng/L (range: 2.64 ± 1.28-6.54 ± 0.18 ng/L) and the average concentration of OPFRs was 400 ± 88 ng/L (range: 316 ± 24-615 ± 36 ng/L) across nine sampling sites. The present study provides a way to resolve the inherent challenge of accumulating hydrophobic substances by POCIS.

Acetamiprid Affects Destruxins Production but Its Accumulation in Metarhizium sp. Spores Increases Infection Ability of Fungi

Metarhizium sp. are entomopathogenic fungi that inhabit the soil environment. Together, they act as natural pest control factors. In the natural environment, they come into contact with various anthropogenic pollutants, and sometimes, they are used together and interchangeably with chemical insecticides (e.g., neonicotinoids) for pest control. In most cases, the compatibility of entomopathogens with insecticides has been determined; however, the influence of these compounds on the metabolism of entomopathogenic fungi has not yet been studied. Secondary metabolites are very important factors that influence the fitness of the producers, playing important roles in the ability of these pathogens to successfully parasitize insects. In this study, for the first time, we focus on whether the insecticide present in the fungal growth environment affects secondary metabolism in fungi. The research revealed that acetamiprid at concentrations from 5 to 50 mg L-1 did not inhibit the growth of all tested Metarhizium sp.; however, it reduced the level of 19 produced destruxins in direct proportion to the dosage used. Furthermore, it was shown that acetamiprid accumulates not only in plant or animal tissues, but also in fungal cells. Despite the negative impact of acetamiprid on secondary metabolism, it was proofed to accumulate in Metarhizium spores, which appeared to have a stronger infectious potential against mealworm Tenebrio molitor, in comparison to the insecticide or the biological agent alone.

Development and Calibration of the Polar Organic Chemical Integrative Sampler (POCIS) for Neonicotinoid Pesticides

Neonicotinoid pesticides are highly hydrophilic systemic insecticides that have been extensively used worldwide. To evaluate their environmental risks, the concentrations of these pesticides in the aquatic environment must be monitored. Although the polar organic chemical integrative sampler (POCIS) has proved to be a suitable passive sampler for many highly hydrophilic compounds, Oasis HLB (Waters) POCIS has shown limitations for the monitoring of neonicotinoid pesticides, such as short linear uptake ranges. In the present study we optimized POCIS for neonicotinoid pesticides by selecting suitable adsorbents and filters. The ENVI-Carb (Supelco) nonporous carbon-based adsorbent demonstrated a good balance between strong sorption and high recovery. Static renewal experiments showed that the our POCIS device using ENVI-Carb with a polyethersulfone membrane filter had a 3 d (dinotefuran) to 28 d (clothianidin, imidacloprid, acetamiprid, and thiacloprid) linear range, which is longer than that of HLB POCIS (≤1 [dinotefuran] to 14 d). The POCIS using ENVI-Carb with a polytetrafluoroethylene membrane had higher sampling rates (0.270 L/d [clothianidin] to 0.686 [imidacloprid] L/d) than those of the HLB POCIS for short-term deployment. The time-weighted average concentrations in actual river water measured by the new POCIS were in good agreement with those obtained by repeated grab sampling, within 30%. Moreover, POCIS detected 2 neonicotinoid pesticides that were not detected by grab sampling. Thus, the proposed POCIS is a promising tool for the monitoring of neonicotinoid pesticides. Environ Toxicol Chem 2020;39:1325-1333. © 2020 SETAC.

Occurrences of 29 pesticides in the Huangpu River, China: Highest ecological risk identified in Shanghai metropolitan area

To investigate the occurrence and risk of pesticides in the Huangpu River basin, spatial and temporal concentration variations of 29 commonly used pesticides and their risk quotient (RQ) values for three different trophic organisms (fish, daphnia, green algae) from 16 sampling sites were conducted in 2018-2019. These 29 pesticides include 4 carbamates, 2 benzimidazoles, 6 neonicotinoids, 2 organophosphates, 9 triazoles, and 6 others. Of the 29 pesticides analyzed, 18 were present in every sample taken from the Huangpu River. The concentration of target pesticides in water samples ranged from < LOQ (for buprofezin in summer, autumn, and winter) to 607.30 ng L^-1 (for carbendazim in spring). From the source (i.e., Taihu Lake) to the estuary of the Huangpu River, with the exception of isocarbophos and isoprothiolane (gradual decrease), the spatial variation of target pesticide concentrations firstly exhibited an increasing trend and then a decreasing trend. Peak spatial variation was seen in metropolitan area, which is closely related to the type of land use and the discharge of tributaries. In addition, the total summed concentration of the 29 pesticides during winter (1037.60 ng L^-1) was higher than summer (788.82 ng L^-1) in rural and metropolitan areas. For the ecological risk assessments of fish, daphnia, and green algae, the triazoles, carbamates, neonicotinoids were risk-dominant pesticides, respectively. Notably, carbendazim had a 100% detection frequency and the highest concentration of the 29 pesticides analyzed, indicating its high consumption in the Huangpu River basin.

Contamination of neonicotinoid insecticides in soil-water-sediment systems of the urban and rural areas in a rapidly developing region: Guangzhou, South China

Residues and distribution of neonicotinoid insecticides (NEOs) in soil-water-sediment systems of the urban and rural areas of Guangzhou, South China were investigated. A total of 104 soil samples from 7 different functional zones and 29 water/sediment samples from creeks were collected. The results showed that at least one neonicotinoid insecticide was detected in all samples. The summed levels of five target neonicotinoids (∑₅neonics) were in the range of 0.003-229 ng/g dw for soil samples, 7.94-636 ng/L for water samples, and 0.017-31.3 ng/g dw for sediment samples, with a geometric mean of 0.59 ng/g dw, 153 ng/L and 1.11 ng/g dw, respectively. Soils from agricultural areas contained the highest residual NEOs, followed by commercial, traffic, residential, industrial, educational zones and parks. Among the seven different functional zones studied, imidacloprid was the most dominant NEO in the agricultural areas and commercial zones, whereas acetamiprid was dominant in the other five functional zones with different land-use types. Thiamethoxam and acetamiprid were the main NEOs in water and sediment samples collected from 29 creeks. The pollution of NEOs in soils, water and sediments from rural areas was higher than that in the counterparts from urban areas. Residual concentration of NEOs detected in soils, water and sediments showed significant correlations with each other. The distribution of NEOs in soil-water-sediment systems indicated that NEOs tended to concentrate in water, followed by sediments and soils, especially in urban areas. An evaluation of the exposure to the current level of the ∑₅NEOs in Guangzhou suggests a significant risk for aquatic and soil organisms, particularly under chronic exposures. The results of the present study offer valuable data to better understand the contamination and ecological risks of neonicotinoid insecticides in the rapidly developing urbanized region of South China.

Toxicogenomics provides insights to toxicity pathways of neonicotinoids to aquatic insect, Chironomus dilutus

Neonicotinoid insecticides have posed a great threat to non-target organisms, yet the mechanisms underlying their toxicity are not well characterized. Major modes of action (MoAs) of imidacloprid were analyzed in an aquatic insect Chironomus dilutus. Lethal and sublethal outcomes were assessed in the midges after 96-h exposure to imidacloprid. Global transcriptomic profiles were determined using de novo RNA-sequencing to more holistically identify toxicity pathways. Transcriptional 10% biological potency values derived from ranked KEGG pathways and GO terms were 0.02 (0.01-0.08) (mean (95% confidence interval) and 0.05 (0.04-0.06) μg L^-1, respectively, which were more sensitive than those from phenotypic traits (10% lethal concentration: 0.44 (0.23-0.79) μg L^-1; 10% burrowing behavior concentration: 0.30 (0.22-0.43) μg L^-1). Major MoAs of imidacloprid in aquatic species were identified as follows: the activation of nicotinic acetylcholine receptors (nAChRs) induced by imidacloprid impaired organisms' nerve system through calcium ion homeostasis imbalance and mitochondrial dysfunction, which posed oxidative stress and DNA damage and eventually caused death of organisms. The current investigation highlighted that imidacloprid affected C. dilutus at environmentally relevant concentrations, and elucidated toxicity pathways derived from gene alteration to individual outcomes, calling for more attention to toxicity of neonicotinoids to aquatic organisms.

Distribution and ecological risk of neonicotinoid insecticides in sediment in South China: Impact of regional characteristics and chemical properties

Neonicotinoid insecticides have been frequently detected in surface water due to extensive use worldwide, however, little information is available for the regional characteristics and ecological risk of neonicotinoids in sediment. In the current study, six neonicotinoids were analyzed in 58 sediment samples from agricultural (vegetable and rice planting) and urban areas in South China. Neonicotinoids were ubiquitous in the sediments, with maximum, mean and median concentrations of 23.8, 4.21 and 2.73 ng·g^-1 dry weight, respectively. Neonicotinoids were detected more often and at higher concentrations in vegetable planting and urban areas while clothianidin and imidacloprid dominated neonicotinoid composition in the rice-planting area. Multiple correspondence analysis showed the distribution of sediment-bound neonicotinoids were significantly affected by crop type, distance to the source, and physicochemical properties of neonicotinoids. While more hydrophilic neonicotinoids tended to migrate to the streams, those with log K_ow > 0 are usually retained in the ditches near the treated fields. Neonicotinoids with shorter half-lives (acetamiprid and thiacloprid) were detected more frequently in vegetable planting areas, yet more persistent imidacloprid and clothianidin were more likely to be detected in rice planting areas. It was in accordance with application patterns of neonicotinoids in different crops. Environmental exposure distributions indicated that sediment-bound neonicotinoids, except for thiacloprid, posed considerable risk to aquatic invertebrates, which are important for ecological functioning of aquatic ecosystems, calling for better measures to control and manage of neonicotinoid risks.

Simultaneous analysis of current-use pesticides and their transformation products in water using mixture-sorbent solid phase extraction and high-performance liquid chromatography-tandem mass spectrometry

Pesticides have posed significant threats to aquatic ecosystems, yet little is known about their transformation products. The challenge is to simultaneously analyze various pesticides and transformation products in water as they have distinct physicochemical properties. A mix-mode solid phase extraction method was established to simultaneously analyze current-use pesticides and their transformation products using a mixture of hydrophile-lipophile balance, weak anion, and cation exchange resins (2:1:1, w/w/w) in combination with high-performance liquid chromatography and tandem mass spectrometry for chemical quantification. Neutral, acidic, and alkaline methanol were used as the elution solvent. Box-Behnken design was applied to optimize extraction conditions. Optimal conditions were as follows: sorbent mass, 200 mg; volume of elution solvent, 5 mL × 3; pH 4. The method was validated for compounds at concentrations from 20 to 1000 ng/L in different types of water samples, with recovery being from 43.5 ± 3.1 to 141 ± 35%. Low method detection limits (0.02-5.6 ng/L) implied that the developed method was sensitive. Finally, the method was applied to monitor current-use pesticides and their transformation products in natural waters. Frequent detection of transformation products of pesticides indicated that their contribution to aquatic risk should not be ignored.

Neonicotinoid insecticides in the drinking water system - Fate, transportation, and their contributions to the overall dietary risks

Neonicotinoids (Neonics) have become the most widely used insecticides around the world in recent years. Due to the hydrophilic character, neonics are emerging contaminants in drinking water. In this study, we aimed to characterize and quantify the fate and transport of neonics in the drinking water treatment system and their contributions to the overall dietary risks. Seven neonics in 97 surface and drinking water samples in the city of Hangzhou, China were analyzed. The relative potency factor method was adopted in order to calculate the total neonics concentrations. We then used the Monte Carlo simulation to calculate the chronic daily intake (CDI) of total neonics from water consumption. All 16 surface water samples collected from two rivers contained at least two neonics, and more than 93% of those contained 3 or more neonics. Imidacloprid was detected in all 16 surface water samples, followed by clothianidin and acetamiprid with average concentrations of 11.9, 7.6, 17.6 ng L-1, respectively. The drinking water treatment plants removed approximately 50% of neonics from surface water. However, 68 out of 71 tap water samples that we collected from the household faucets contained at least one neonic, with the highest average concentrations of 5.8 ng L-1 for acetamiprid. The maximum of CDIs of total neonics from water consumption for adult and children were 10.2 and 12.4 ng kg-1 d-1, respectively, which are significantly lower than the acceptable daily intake (ADI). The results presented here shown drinking water consumption only represented an insignificant portion of dietary risks of total neonics, mainly due to the modern drinking water treatment technologies that are capable of removing significant amount of neonics from drinking water. However, the ubiquity of neonics in the drinking water sources to kitchen faucets, should be a concern for public health.

Dietary exposure to neonicotinoid insecticides and health risks in the Chinese general population through two consecutive total diet studies

Neonicotinoid insecticides are ubiquitous in food and the environment due to their wide use. Growing evidence suggests the adverse effects of neonicotinoids in many species, including mammals. Some studies have reported the urinary concentrations of neonicotinoids in human biological monitoring, but the potential risks of neonicotinoids on human health based on long-term chronic exposure studies in any general population have been rarely tackled. In this study, the dietary exposure to neonicotinoids of the Chinese adult population was studied on the basis of composite dietary samples collected from the 5th (2009-2012) and 6th (2015-2018) Chinese total diet studies (TDS). Residue levels of ten neonicotinoids were determined in 528 composite dietary samples from 24 provinces in China. Most of the samples (53.3% and 70.5% in the 5th and 6th TDS, respectively) that we analyzed contained the multi-residue of neonicotinoids. Imidacloprid and acetamiprid were the most frequently detected neonicotinoids, and thiamethoxam and clothianidin were increasingly used and found in the 6th TDS. The estimated daily intake (EDI) for total neonicotinoids was calculated to evaluate health risk of the Chinese adult population based on a relative potency factor assessment method. The mean EDIs of total neonicotinoids in the 5th and 6th TDS respectively reached 598.95 and 710.38 ng/kg bw per day. Although the mean EDIs of total neonics in 6th TDS was relatively higher than that in 5th TDS, no statistical difference was observed (p > 0.05). Vegetables were the main source of dietary exposure, but exposure via cereals and beverages and water must also be addressed in China. Although the average exposure for total neonicotinoids was much lower than the current chronic reference dose (57 μg/kg bw per day), the dietary exposure risks of a general population for total neonicotinoids should not be overlooked due to the ubiquity of neonicotinoids in food and the environment.

Physiological endpoints in daphnid acute toxicity tests

Daphnids are freshwater crustaceans used in toxicity tests. Although lethality and immobilisation are the most commonly used endpoints in those tests, more sensitive parameters are required for determination of sublethal acute effects of toxicants. The use of various physiological endpoints in daphnids is considered as a low-cost and simple alternative that meets the 3R's rule (Replacement, Reduction, Refinement) criteria. However, currently there is no review-based evaluation of their applicability in toxicity testing. This paper presents the results on the most commonly determined physiological parameters of Daphnia in ecotoxicological studies and human drug testing, such as feeding activity, thoracic limb movement, heart rate, cardiac area, respiratory activity, compound eye, mandible movements and post-abdominal claw contractions. Furthermore, their applicability as promising endpoints in the assessment of water quality or drug testing is discussed.

Neonicotinoids and carbendazim in indoor dust from three cities in China: Spatial and temporal variations

Neonicotinoid insecticides (NNIs) are a relatively new class of insecticides, and carbendazim (CBDZ) is a representative antifungal biocide. The occurrence of them in indoor dust was not documented in China. In this study, 336 indoor dust samples were collected from 3 cities, including Taiyuan (October 2016), Wuhan (October 2016 and 2018), and Shenzhen (February 2019), located in North, Central, and South China, for determination of the residues of six NNIs, two of their metabolites, and CBDZ. Acetamiprid (ACE), imidacloprid (IMI), and CBDZ were found to be the major target analytes in dust samples from all selected cities with detection frequencies of 98.8%, 99.7%, and 95.2%, respectively. At least one target NNI was detected for all of the dust samples, with the median concentration of 25.8 ng/g for the imidacloprid-equivalent total neonicotinoids (IMI_eq: generated by the relative potency factor method), and the median for CBDZ was 35.8 ng/g. Higher levels of several NNIs and CBDZ were found in urban areas of Taiyuan and Wuhan than those in rural areas. A significant increase of the NNI residues was observed in dust of Wuhan from 2016 to 2018 (while not significant for CBDZ). Finally, the estimated daily intake (EDI) of IMI_eq and CBDZ for infants and toddlers were higher than that found in other age groups through dust ingestion, which indicated that infants and toddlers may be susceptible to current residue of NNIs and CBDZ in indoor dust, and dust ingestion of NNIs might be <1% of that reported for dietary intakes in China. This is the first study to report the residue levels of NNIs and CBDZ in dust samples from indoor environment in China.