Environmental risk assessment of neonicotinoids in surface water

A dynamic energy budget (DEB) model to assess the sublethal effects of imidacloprid toward Gammarus pulex at different temperatures

Environmental ambient temperature significantly impacts the metabolic activities of aquatic ectotherm organisms and influences the fate of various chemicals. Although numerous studies have shown that the acute lethal toxicity of most chemicals increases with increasing temperature, the impact of temperature on chronic effects - encompassing both lethal and sublethal endpoints - has received limited attention. Furthermore, the mechanisms linking temperature and toxicity, potentially unveiled by toxicokinetic-toxicodynamic models (TKTD), remains inadequately explored. This study investigated the effects of environmentally relevant concentrations of the insecticide imidacloprid (IMI) on the growth and survival of the freshwater amphipod Gammarus pulex at two different temperatures. Our experimental design was tailored to fit a TKTD model, specifically the Dynamic Energy Budget (DEB) model. We conducted experiments spanning three and six months, utilizing small G. pulex juveniles. We observed effects endpoints at least five times, employing both destructive and non-destructive methods, crucial for accurate model fittings. Our findings reveal that IMI at environmental concentrations (up to 0.3 μg/L) affects the growth and survival of G. pulex, albeit with limited effects, showing a 10% inhibition compared to the control group. These limited effects, observed in both lethal and sublethal aspects, suggest a different mode of action at low, environmentally-relevant concentrations in long-term exposure (3 months), in contrast to previous studies which applied higher concentrations and found that sublethal effects occurred at significantly lower levels than lethal effects in an acute test setting (4 days). Moreover, after parameterizing the DEB model for various temperatures, we identified a lower threshold for both lethal and sublethal effects at higher temperatures, indicating increased intrinsic sensitivity. Overall, this study contributes to future risk assessments considering temperature as a crucial factor and exemplifies the integration of the DEB model into experimental design for comprehensive toxicity evaluations.

Comprehensive risk assessment and interactions of fluoride and boron ions in the water-sediments interface: The Red Sea, Egypt

This study presents a baseline evaluation of the distribution, human and ecotoxicological risk, and the potential interactions of fluoride and boron in the water-sediment interface in 25 locations from incredible Red Sea tourist destinations. Results showed comparable levels of B and F in the water and sediments with previous literature. Significant positive correlation was found between B and F (r = 0.57; P<0.01). Based on the sediment/liquid partition coefficient (Kd), F is more likely to be released from the sediment into seawater (logKd< 3) than B (3< logKd< 4). pH and alkalinity may affect water-sediment interactions of B and F, respectively, while SO42- and Cl- ions had no significant effect on adsorption ability of F and B. The majority of minerals had average saturation Index (SI) > 1 referring to the over saturation of seawater with these minerals and their inability to dissolve. The formation of CF, FAP, and CFAP may be related to the high correlation between Fw (r = 0.928, P< 0.01; r = 0.527, P< 0.01; r = 0.608, P< 0.01) and Bw (r = 0.38, P< 0.05; r = 0.38, P< 0.05; r = 0.397, P< 0.05). Total hazard quotient (THQ) for children and adults were <1, revealing no health risks from exposure to B and F through ingestion and skin contact while swimming. The risk characterization ratio; RCRmix(MEC/PNEC) showed high short-term risks to aquatic organisms. Further investigations might emphasis on emerging mitigation strategies to address these concerns.

A comparative study of surfactant distribution and fate (western and eastern) Egyptian Mediterranean coasts focusing on its environmental toxicity

One of the most difficult-to-manage new contaminants constantly released into the environment is linear alkylbenzene sulphonate (LAS), an anionic surfactant. Significant volumes of LAS are received by the Mediterranean coast of Egypt. The current study is a comprehensive assessment of the environmental fate of the LAS 1505 km off the Mediterranean coast of Egypt in the fall of 2023 in order to track its geographic spread and eventual demise in the water column. Critical analysis of LAS revealed that it is vertically distributed in various ways according to sources, uses, production amounts, and salinity levels. The vertical variation of LAS can be explained by its amphiphilic structure. A significant increase in surfactant concentration (>300 μg/L) was recorded in 66% and 43% of the total samples, ranging from 301.128 to 455.36 and from 304.556 to 486.135 for the western and eastern sides along the Egyptian Mediterranean coast, respectively. Evaluation of the average acute and chronic risk quotient (RQ) along the investigated locations revealed that fish were the most susceptible to LAS in both long and short exposure periods. The presented results also indicated significant LAS toxicity to three trophic levels (RQ values > 1). LAS toxicity to marine organisms was greater in the western than in eastern coastal regions according to acute and chronic mixture risk characterization ratios (RCRmix). The three trophic levels in the study area had the following order of acute relative contribution (RC) to LAS toxicity: fish > invertebrates > algae. The ANOVA test results showed that in both the western and eastern regions, LAS varied significantly (p < 0.05) with salinity (1.04E-60 and 5.44E-42) and depth (6.02E-65 and 1.59E-47), respectively. In addition, a significant difference was observed using the ANOVA test between the eastern and western regions of the Egyptian Mediterranean coast.

Impact of land development along the western Mediterranean coast of Egypt regarding surfactant sources, interfering elements and ecotoxicity

The effect of recent land development of the western side of the Egyptian Mediterranean coast on the fates, behaviors, interactions, and ecotoxicology of surfactant (LAS), F, Br, B, Ca, Mg, and P was studied. Samples of seawater and sediments were collected from 15 stations at different depths representing, 5 perpendicular sectors. Elevated levels of LAS were identified in seawater columns in the El-Hamam (467.3 ± 220.8 μg/L) and El-Dabaa (480.0 ± 314.1 μg/L) stations. LAS homologue in sediment was in the range of 0.013-0.024, 0.042-0.184, 0.086-0.402, and 0.025-0.058 μg/g for C10, C11, C12, and C13, respectively. Studied parameters showed mixture risk characterization ratios RCRmix > 1 for algae, invertebrates, and fish in seawater and sediments, except for P, which showed low risk (RCRmix ≤ 1) in sediment. Acute relative contribution (RC) of LAS reflected that fish were the most sensitive species (RCFish = 48.5), followed by algae (RCAlgae = 44.4) and invertebrates (RCInvert = 7.1).

Risk analysis for groundwater intakes based on the example of neonicotinoids

Neonicotinoids are a class of broad-spectrum insecticides that are dominant in the world market. They are widely distributed in the environment. Understanding the sources, distribution, and fate of these contaminants is critical to mitigating their effects and maintaining the health of aquatic ecosystems. Contamination of surface and groundwater by neonicotinoids has become a widespread problem worldwide, requiring comprehensive action to accurately determine the mechanisms behind the migration of these pesticides, their properties, and their adverse effects on the environment. A new approach to risk analysis for groundwater intake contamination with emerging contaminants was proposed. It was conducted on the example of four neonicotinoids (acetamiprid, clothianidin, thiamethoxam, and imidacloprid) in relation to groundwater accessed by a hypothetical groundwater intake, based on data obtained in laboratory tests using a dynamic method (column experiments). The results of the risk analysis conducted have shown that in this case study the use of acetamiprid and thiamethoxam for agricultural purposes poses an acceptable risk, and does not pose a risk to the quality of groundwater extracted from the intake for food purposes. Consequently, it does not pose a risk to the health and life of humans and other organisms depending on that water. The opposite situation is observed for clothianidin and imidacloprid, which pose a higher risk of groundwater contamination. For higher maximum concentration of neonicotinoids used in the risk analysis, the concentration of clothianidin and imidacloprid in the groundwater intake significantly (from several to several hundred thousand times) exceeds the maximum permissible levels for drinking water (<0.1 μg/L). This risk exists even if the insecticides containing these pesticides are used according to the information sheet provided by the manufacturer (lower maximum concentration), which results in exceeding the maximum permissible levels for drinking water from several to several hundred times.

Dinotefuran exposure alters biochemical, metabolomic, gut microbiome, and growth responses in decapoda pacific white shrimp Penaeus vannamei

Dinotefuran, a neonicotinoid insecticide, may impact nontarget organisms such as Decapoda P. vannamei shrimp with nervous systems similar to insects. Exposing shrimp to low dinotefuran concentrations (6, 60, and 600 μg/L) for 21 days affected growth, hepatosomatic index, and survival. Biomarkers erythromycin-N-demethylase, alanine aminotransferase, and catalase increased in all exposed groups, while glutathione S-transferase is the opposite; aminopyrin-N-demethylase, malondialdehyde, and aspartate aminotransferase increased at 60 and 600 μg/L. Concentration-dependent effects on gut microbiota altered the abundance of bacterial groups, increased potentially pathogenic and oxidative stress-resistant phenotypes, and decreased biofilm formation. Gram-positive/negative microbiota changed significantly. Metabolite differences between the exposed and control groups were identified using mass spectrometry and KEGG pathway enrichment. N-acetylcystathionine showed potential as a reliable dinotefuran metabolic marker. Weighted correlation network analysis (WGCNA) results indicated high connectivity of cruecdysone in the metabolite network and significant enrichment at 600 μg/L dinotefuran. The WGCNA results revealed a highly significant negative correlation between two key metabolites, caldine and indican, and the gut microbiota within co-expression modules. Overall, the risk of dinotefuran exposure to non-target organisms in aquatic environments still requires further attention.

Assessing pesticide residues occurrence and risks in water systems: A Pan-European and Argentina perspective

Freshwater ecosystems face a particularly high risk of biodiversity loss compared to marine and terrestrial systems. The use of pesticides in agricultural fields is recognized as a relevant stressor for freshwater environments, exerting a negative impact worldwide on the overall status and health of the freshwater communities. In the present work, part of the Horizon 2020 funded SPRINT project, the occurrence of 193 pesticide residues was investigated in 64 small water bodies of distinct typology (creeks, streams, channels, ditches, rivers, lakes, ponds and reservoirs), located in regions with high agricultural activity in 10 European countries and in Argentina. Mixtures of pesticide residues were detected in all water bodies (20, median; 8-40 min-max). Total pesticide levels found ranged between 6.89 and 5860 ng/L, highlighting herbicides as the dominant type of pesticides. Glyphosate was the compound with the highest median concentration followed by 2,4-D and MCPA, and in a lower degree by dimethomorph, fluopicolide, prothioconazole and metolachlor(-S). Argentina was the site with the highest total pesticide concentration in water bodies followed by The Netherlands, Portugal and France. One or more pesticides exceeded the threshold values established in the European Water Framework Directive for surface water in 9 out of 11 case study sites (CSS), and the total pesticide concentration surpassed the reference value of 500 ng/L in 8 CSS. Although only 5 % (bifenthrin, dieldrin, fipronil sulfone, permethrin, and terbutryn) of the individual pesticides denoted high risk (RQ > 1), the ratios estimated for pesticide mixtures suggested potential environmental risk in the aquatic compartment studied.

Risk mitigation strategy and mechanism analysis of neonicotinoid pesticides on earthworms

Neonicotinoid insecticides (NNIs) are a new class of widely used insecticides with certain risks to non-target organisms, like earthworms. The gray correlation method was used to calculate the comprehensive risk effect value of acute toxicity (LC50) and bioaccumulation (logKow) of NNIs on earthworms. A comprehensive effects three-dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed, using NNIs molecular structures and the comprehensive effect value as the independent and dependent variables, respectively. One of the representatives guadipyr (GUA) was selected as the template molecule for the molecular design and modification. A total of 63 NNIs alternatives were designed with a reduced comprehensive value higher than 10%, and as high as 42%. After screening, 15 NNIs alternatives were screened with decreased acute toxicity to earthworms, bioaccumulation effects and improved functional property. The calculated primary acute risk quotient of earthworms shows that the designed NNIs alternatives have lower earthworm risks (reduction of 70.48-99.99%). Results also found that the electronic, geometric and topological parameters of NNIs are the key descriptors that affect NNIs alternatives' toxicity. The number of hydrophobic interaction amino acid residues in NNIs molecules also contributes to the acute toxicity and the bioaccumulation of NNIs alternatives on earthworms. This study aims to design and screen functionally improved and environmentally friendly NNIs alternatives that have low risk to earthworms and provide theoretical methods and new ideas for the risk control and development of pesticides represented by NNIs.

Occurrence, distribution, and health risk assessment of pyrethroid and neonicotinoid insecticides in aquatic products of China

Synthetic pyrethroid insecticides (SPIs) and neonicotinoid insecticides (NEOs), now dominant in the insecticide market, are increasingly found in aquatic environments. This study focused on six SPIs and five NEOs in aquatic products from four Chinese provinces (Shandong, Hubei, Shanxi and Zhejiang) and the risk assessment of the safety for the residents was conducted. It revealed significantly higher residues of Σ6SPIs (6.27-117.19 μg/kg) compared to Σ5NEOs (0.30-14.05 μg/kg), with SPIs more prevalent in fish and NEOs in shellfish. Carnivorous fish showed higher pesticide levels. Residues of these two types of pesticides were higher in carnivorous fish than in fish with other feeding habits. In the four regions investigated, the hazard quotient and hazard index of SPIs and NEOs were all <1, indicating no immediate health risk to human from single and compound contamination of the two types of pesticides in aquatic products. The present study provides valuable information for aquaculture management, pollution control and safeguarding human health.

Photolysis of dinotefuran in aqueous solution: Kinetics, influencing factors and photodegradation mechanism

The environmental behaviour of neonicotinoid insecticides (NNIs) is of momentous concern due to their frequent detection in aquatic environment and their biotoxicity for non-target organisms. Phototransformation is one of the most significant transformation processes, which is directly related to NNIs exposure and environmental risks. In this study, the photodegradation of dinotefuran (DIN, 1-Methyl-2-nitro-3-(tetrahydro-3-furanylmethyl)-guanidine), one of the most promising NNIs, was conducted under irritated light in the presence of Cl-, DOM along with the effect of pH and initial concentration. The findings demonstrated that in ultra-pure (UP) water, the photolysis rate constants (k) of DIN rose with increasing initial concentration. Whereas, in tap water, at varied pH levels, and in the presence of Cl-, the outcomes were reversed. At the same time, lower concentration of DOM promoted DIN photolysis processes due to the production of reactive oxygen species, while higher concentrations of DOM inhibited the photolysis by the predominance of light shielding effects. The singlet oxygen (1O2) was produced in the photolysis processes of DIN with Cl- and DOM, which was confirmed by electron spin resonance (EPR) analysis. Four main photolysis products and three intermediates were identified by UPLC-Q-Exactive Orbitrap MS analysis. The possible photodegradation pathways of DIN were proposed including the oxidation by 1O2, reduction and hydrolysis after the removal of nitro group from parent compounds. This study expanding our understanding of transformation behavior and fate of NNIs in the aquatic environment, which is essential for estimating their environmental risks.

Neonicotinoids Persisting in the Sea Pose a Potential Chronic Risk to Marine Organisms: A Case from Xiangshan Bay, China (2015-2019)

Neonicotinoid insecticides (neonics) are extensively employed in agriculture and pervade various environmental matrices. However, few studies have documented the occurrence and potential chronic ecological risks of these chemicals in the marine environment. We collected 720 seawater samples from Xiangshan Bay during 2015-2019 and the integrated concentrations of seven neonics were determined using the relative potency factor method. Trend analyses using the Mann-Kendall test in time series, along with the estimation of the flux of neonics into the sea, were conducted. At last, the ecological risk of neonics was evaluated by water quality criteria derivation based on species sensitivity distribution. Our findings revealed that 47.6% of samples contained at least one neonic, with the integrated concentration of neonics ranging from 63.30 to 1684.14 ng/L. Imidacloprid and dinotefuran exhibited the highest frequency of detection in the analysis. The significance level of the Mann-Kendall test ranged from 2.16 × 10-10 to 1.21 × 10-5 (S > 0), indicating all neonics behaved with sharply increasing trends. Approximately 8.47 × 10-2 tons of neonics were discharged into Xiangshan Bay. Notably, the integrated concentrations of neonics represented a potential chronic ecological risk to marine organisms. This study provided novel insights into the spatial distribution, source, and migration of neonic species and their impacts on marine ecosystems.

Application of passive sampling device for exploring the occurrence, distribution, and risk of pharmaceuticals and pesticides in surface water

Pharmaceuticals and pesticides are compounds of high concern in surface waters around the world. However, few studies have used passive sampling methods to screen and detect these compounds in natural waters. In this study, a self-developed passive sampler was employed to measure pharmaceuticals and pesticides in the rivers of Nanjing, China. A total of 41 pharmaceuticals and 11 pesticides were detected, among which antibiotic and insecticide were the predominant classes, respectively. Valproic acid, caffeine and triclosan from the pharmaceuticals, and isoprocarb and imidacloprid from the pesticides were found frequently with high concentrations. At most sampling sites, the concentration ratios of caffeine versus carbamazepine exceeded 10, and even above 50, indicating relatively poor efficiency of wastewater treatment, or possibly the direct discharge of raw sewage, or other unknown source of pollution. It was found that the concentrations and ecological risks in the northern area of Yangtze River were higher than those in the southern area of Yangtze River, implying that economic development and population density were not the main contributors to the discovered pollution. The total concentration of pharmaceuticals and pesticides in Qinhuai River increased gradually with the direction of water flow, demonstrating the success of water diversion project in flushing and scouring pollutants.

Pharmaceutically active compounds (PhACs) in surface water: Occurrence, trends and risk assessment in the Tagus River Basin (Spain)

In this study, the presence of 23 pharmaceutically active compounds (PhACs) including antibiotics, analgesics, anti-inflammatories, psychiatric and cardiovascular drugs, antifungals and metabolites was investigated in surface waters. A total of 89 samples were collected during 3 years (2020, 2021 and 2022) from a European representative river basin (Tagus, Spain). To elucidate PhAC potential sources, sampling points located in areas with low, median and high anthropogenic influence were selected. The analytical method based on solid phase extraction (SPE) followed by UHPLC-MS/MS analysis was validated meeting SANTE/2020/12830 and SANTE/12682/2019 performance criteria. PhACs were quantified above limits of quantification (LOQs) in 96 % of water samples, being the antihypertensives valsartan (648 ng/L, 87 % quantification frequency) and irbesartan (390 ng/L, 75 %) and the antidepressant o-desmethylvenlafaxine (495 ng/L, 76 %) the predominant pollutants. The rest of the target PhACs showed median concentrations between 4 and 172 ng/L with quantification frequencies ranging from 35 to 75 %. ∑PhAC concentrations did not show temporal or seasonal trends. However, valsartan and naproxen presented lower levels in drier (spring and summer) compared to the wetter. Source identification revealed a clear anthropogenic origin since concentrations obtained in highly populated areas were statistically higher (p < 0.01) than those quantified in sparsely populated ones. This finding was also confirmed by calculating PhACs mass flow rates, which ranged between 1.4 and 235 kg/y. Finally, data generated were used to estimate the potential risk to the aquatic ecosystem for three trophic levels (phototrophic, invertebrate and vertebrate organisms). Risk quotient ratios (RQs) were calculated for all PhACs at the median (P50) and worst-case (max) scenarios. Up to 7 PhACs (acetaminophen, carbamazepine, gemfibrozil, ibuprofen, irbesartan, ketoprofen and venlafaxine) showed high risk for the highest trophic level (fish) in >45 % of investigated locations.

Contamination of neonicotinoid insecticides in source water and their fate during drinking water treatment in the Dongguan section of the Pearl River

Neonicotinoid insecticides (NEOs) as well as their metabolites are highly mobile on the subsurface and can potentially contaminate drinking water sources; however, their pollution status and fate in the drinking water system remains ambiguous. In this study, six parent NEOs and two characteristic metabolites were measured in drinking water source protection area (source water, n = 52) and two related drinking water treatment plants (DWTPs) (n = 88) located in the Dongguan section of the Pearl River. The ubiquitous of NEOs was observed in source water with the mean concentration of total NEOs (ΣNEOs) at 240 ng/L. Although advanced DWTP (A-DWTP; range: 26 % to 100 %) showed better removals of ΣNEOs and all individual NEOs rather than those in conventional DWTP (C-DWTP; range: -53 % to 28 %), the removals were still low for acetamiprid (ACE, 26 %), thiacloprid (THD, 59 %), thiamethoxam (THM, 56 %) and N-desmethyl-acetamiprid (N-dm-ACE, 45 %) in A-DWTP. Removal rates were positive in chlorination (48 %), final stage of sedimentation (F-Sed, 24 %), and granular activated carbon (GAC) filter effluent (19 %) in A-DWTP. It worthy to note that ΣNEOs has high negative removal rates at the start stage of sedimentation (S-Sed, -83 %), middle stage of sedimentation (M-Sed, -47 %), and sand filter effluent (-42 %) water in C-DWTP, which resulted in negative removals of ΣNEOs (-9.6 %), imidacloprid (IMI, -22 %), clothianidin (CLO, -37 %), flupyradifurone (FLU, -76 %), and N-dm-ACE (-29 %) in C-DWTP. Residual levels of NEOs were high in source water, and their low or negative removals in DWTPs should be highly concerning. Results would fill the existing knowledge gap of NEOs in aquatic environment and provide a scientific dataset for policy-making on pollution control and environmental protection.

Thiamethoxam adsorption by ZnCl2 modified cow manure biochar: Mechanism and quantitative prediction

The overuse of thiamethoxam (THM) has threatened the survival of living organisms and it is necessary to find an environmentally friendly material to remove THM frequently detected in water. Biochar prepared from cow manure modified with ZnCl2 (Zn-CBC) was used to remove THM. Compared to the unmodified cow manure biochar (CBC), the removal ratio of THM by Zn-CBC was enhanced 35 times. In the mechanistic analysis, SEM and BET showed that Zn-CBC had a good pore structure and its specific surface area (166.502 m2 g-1) increased to 17 times that of CBC, indicating that Zn-CBC had good pore adsorption properties. The adsorption kinetic and isotherm implied that the main mechanism was chemisorption including π-π interaction and H-bonding. Furthermore, the stable graphitized structure of Zn-CBC allowed for efficient adsorption and reusability. In addition, this study constructed an intelligent prediction model using batch experiment data, and the high R2 (0.978) and low RMSE (0.057) implied that the model could accurately and quantitatively predict the adsorption efficiency. This paper provides a novel perspective to simultaneously remove the neonicotinoid insecticides and realize the resource utilization of cow manure.

Uncovering the impact of agricultural activities and urbanization on rivers from the Piracicaba, Capivari, and Jundiaí basin in São Paulo, Brazil: A survey of pesticides, hormones, pharmaceuticals, industrial chemicals, and PFAS

Rivers in Southeast Brazil are essential as sources of drinking water, energy production, irrigation, and industrial processes. The Piracicaba, Capivari, and Jundiaí rivers basin, known as the PCJ basin, comprises major cities, industrial hubs, and large agricultural areas, which have impacted the water quality in the region. Emerging contaminants such as pesticides, hormones, pharmaceuticals, industrial chemicals, and per- and polyfluoroalkyl substances (PFAS) are likely to be released into the rivers in the PCJ basin; however, the current Brazilian legislation does not require monitoring of most of these chemicals. Thus, the extent of emerging contaminants pollution and their risks to aquatic and human life in the basin are largely unknown. In this study, we investigated the occurrence of several pesticides, hormones, pharmaceuticals, and personal care products in 15 sampling points across the PCJ basin, while industrial chemicals and PFAS were assessed in 11 sampling points. The results show that agriculture and industrial activities are indeed causing the pollution of most rivers. Multivariate analysis indicates that some sampling points, such as Jundiaí, Capivari, and Piracicaba rivers, are largely impacted by pesticides used in agriculture. In addition, to the best of our knowledge, this is the first study reporting the presence of PFAS in rivers in São Paulo, the most populous state in Brazil. Four out of eight species of PFAS assessed in our study were detected in at least 5 sampling points at concentrations ranging from 2.0 to 50.0 ng L-1. The preliminary risk assessment indicates that various pesticides, caffeine, industrial chemicals, and PFAS were present at concentrations that could threaten aquatic life. Notably, risk quotients of 414, 340, and 178 were obtained for diuron, atrazine, and imidacloprid, respectively, in the Jundiaí River. Our study suggests that establishing a comprehensive monitoring program is needed to ensure the protection of aquatic life and human health.

Selected neonicotinoids and associated risk for aquatic organisms

Neonicotinoids are one of the newest groups of systemic pesticides, effective on a wide range of invertebrate pests. The success of neonicotinoids can be assessed according to the amount used, for example, in the Czech Republic, which now accounts for 1/3 of the insecticide market. The European Union (EU) has a relatively interesting attitude towards neonicotinoids. Three neonicotinoid substances (imidacloprid, clothianidin and thiamethoxam) were severely restricted in 2013. In 2019, imidacloprid and clothianidin were banned, while thiamethoxam and thiacloprid were banned in 2020. In 2022, another substance, sulfoxaflor, was banned. Therefore, only two neonicotinoid substances (acetamiprid and flupyradifurone) are approved for outdoor use in the EU. Neonicotinoids enter aquatic ecosystems in many ways. In European rivers, neonicotinoids usually occur in nanograms per litre. Due to the low toxicity of neonicotinoids to standard test species, they were not expected to significantly impact the aquatic ecosystem until later studies showed that aquatic invertebrates, especially insects, are much more sensitive to neonicotinoids. In addition to the lethal effects, many studies point to sublethal impacts - reduced reproductive capacity, initiation of downstream drift of organisms, reduced ability to eat, or a change in feeding strategies. Neonicotinoids can affect individuals, populations, and entire ecosystems.

Induction of apoptosis, oxidative stress, hormonal, and histological alterations in the reproductive system of thiamethoxam-exposed female rats

The present study aimed to investigate the oral toxic effects of 1/10 LD50 and 1/5 LD50 of thiamethoxam (TMX), a neonicotinoid insecticide, on the reproductive system of female Wistar rats. Thirty female rats were divided into three groups and supplied orally with either; saline solution, 1/10 LD50 of TMX (156 mg/kg) or 1/5 LD50 of TMX (312 mg/kg). The daily administration was extended for 30 days. Investigating the parameters of oxidative stress, hormonal levels, histopathological alterations, and the apoptotic markers (P53, BAX, BCL-2, and caspase-3) was performed in the uterus and ovary of rats. Results showed significant changes in the body weight gain, and relative weight of the left and right ovaries and uterus. Moreover, luteinizing hormone (LH), estradiol (ED), and progesterone (PG) serum levels were not significantly altered following TMX oral administration. The level of follicle-stimulating hormone in the TMX-exposed group (156 mg/kg) was significantly increased; however, a significant decrease was observed in TMX-exposed animals (312 mg/kg). TMX induced significant oxidative stress in exposed groups by reducing the activities of superoxide dismutase (SOD), glutathione (GSH), and catalase (CAT), and elevating malondialdehyde (MDA) levels. Following hematoxylin and eosin staining, the microscopic examination revealed deteriorated luteal cells with vacuolation in the corpus luteum, a follicle containing a degenerated oocyte and degeneration/necrosis of the circular muscle layer with a high rate of apoptotic cells in TMX-exposed animals. TMX induced transcriptional alterations in apoptosis-related genes shifting towards the activation of the intrinsic apoptotic pathway. Collectively, results suggest the toxic effect of the TMX on the reproductive health of female Wistar rats.

Urinary neonicotinoid insecticides and adiposity measures among 7-year-old children in northern China: A cross-sectional study

BACKGROUND

Neonicotinoid insecticides (NEOs) are emerging synthetic insecticides used in various pest management regimens worldwide. Toxicology studies have indicated the obesogenic potential of NEOs, but their associations with adiposity measures are largely unknown.

OBJECTIVES

We aimed to assess urinary levels of NEOs/metabolites and their associations with children's adiposity measures, and to further investigate the potential role of oxidative stress.

METHODS

This study included 380 children who participated in the 7th year's follow-up of the Laizhou Wan Birth Cohort in northern China. Urinary levels of seven NEOs and two metabolites and a biomarker of lipid peroxidation named 8-iso-prostaglandin-F2α (8-iso-PGF2α) were detected. A total of nine indicators of adiposity were measured. Body mass index (BMI) z-score ≥85th percentile was defined as overweight/obesity, and waist-to-height ratio (WHtR) ≥0.5 was considered as abdominal obesity. Multiple linear regression, binary logistic regression and mediation analysis were performed.

RESULTS

Six NEOs [imidacloprid (IMI, 99.7%), clothianidin (CLO, 98.9%), dinotefuran (DIN, 97.6%), thiamethoxam (THM, 95.5%), acetamiprid (ACE, 82.9%), thiacloprid (THD, 77.6%)] and two metabolites [N-desmethyl-acetamiprid (N-DMA, 100.0%), 6-chloronicotinic acid (6-CINA, 97.9%)] exhibited high detection rates. Multiple linear regressions showed positive associations of waist circumference with urinary levels of IMI and THM, of WHtR with IMI and THM levels, and of body fat percentage with 6-CINA levels. In contrast, exposure to N-DMA was negatively associated with body fat percentage and fat mass index. Binary logistic regressions further revealed that higher IMI levels were associated with overweight/obesity (OR = 1.556, 95% CI: 1.100, 2.201) and abdominal obesity (OR = 1.478, 95% CI: 1.078, 2.026) in children. 8-iso-PGF2α demonstrated 27.92%, 69.52% and 35.37% mediating effects in the positive associations of IMI, THD and THM with WHtR, respectively. Sex modified the associations of DIN with body fat mass (p_int = 0.032), body fat percentage (p_int = 0.009), fat mass index (p_int = 0.037) and the overweight/obesity rate (p_int = 0.046), with negative associations in girls and nonsignificant positive associations in boys.

CONCLUSIONS

School-age children in northern China were widely exposed to NEOs/metabolites. Urinary levels of NEOs/metabolites were associated with adiposity measures through the mediating role of 8-iso-PGF2α. These associations were mixed, and a sex-specific effect might exist.

Abnormal fluoride distribution, human health risk assessment, predicted no-effect concentration (PNEC) and environmental hazards in an Egyptian lake connected to the Mediterranean Sea

Fluoride can affect the metabolism and physiological functioning of humans and aquatic organisms like any hazardous substance when it exceeds its permissible limits and PNEC values. The fluoride content of the lake water and sediment samples collected from different locations was determined to assess its risks to humans and its ecological toxicity in Lake Burullus. Statistical analyses show that the proximity of the supplying drains had an impact on the fluoride content. Fluoride ingestion and skin contact in lake water and sediment during swimming for child, female and male were evaluated at 95, 90, and 50%. The values of hazard quotient (HQ) and total hazard quotient (THQ) for children, females and males were less than one, reflecting that exposure to fluoride through ingestion and skin-to-skin contact while swimming poses no risks to human health. PNEC values for fluoride in lake water and sediment were estimated using the equilibrium partitioning method (EPM). The ecological risk assessment of fluoride for acute and chronic toxicity was performed for the three trophic levels based on the PNEC, the half-maximal effective concentration (EC₅₀), the median lethal dose (LC₅₀), the no-observed effect concentration (NOEC), and the 5% lethal concentration (EC₀₅). The risk quotient (RQ), mixture risk characterization ratios (RCR_mix), relative contribution (RC), toxic unit (TU), and sum of toxic units (STU) were estimated. The acute and chronic RCR_mix(STU) and RCR_{mix(MEC/PNEC)} produced similar values for the three trophic levels in lake water and sediment, indicating that invertebrates are the most sensitive species to fluoride. These results of evaluating the environmental risks of fluoride in lake water and sediments reflected its significant impact on aquatic organisms living in the lake area in the long term.

Computer-aided toxicity prediction and potential risk assessment of two novel neonicotinoids, paichongding and cycloxaprid, to hydrobionts

Paichongding (IPP) and cycloxaprid (CYC) have been effectively used as the alternative products of imidacloprid (IMI) against IMI-resistant insects and exhibit a great market potential. However, risk assessment of IPP and CYC for non-target organisms, especially ecological risk assessment for non-target aquatic organisms, is still lacking. Here, we predicted the toxicity and potential risks of IPP, CYC, and their transformation products (TPs) to hydrobionts. The results indicated that IPP and CYC could generate 428 and 113 TPs, respectively, via aerobic microbial transformation. Nearly half of the IPP TPs and nearly 41 % of the CYC TPs exhibited high or moderate toxicity to Daphnia or fish. Moreover, we found that IPP, CYC, and 80 TPs of them posed potential risks to aquatic ecosystems. Almost all harmful TPs contained a 6-chloropyridine ring structure, suggesting that this structure may be associated with the strong toxicity of these TPs to aquatic organisms, and these TPs (IPP-TP2 or CYC-TP2, IPP-TP197 or CYC-TP71, IPP-TP198 or CYC-TP72, and IPP-TP212 or CYC-TP80) may appear in aquatic environments as final products. The risks posed by these TPs to aquatic ecosystems require more attention. This study provides insights into the toxicity and ecological risks of IPP and CYC.

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.

Response of microbial community to the remediation of neonicotinoid insecticide imidacloprid contaminated wetland soil by Phanerochaete chrysosporium

Imidacloprid (IMI), a typic neonicotinoid insecticide, is widely used and persist in soils with long half-time causing serious threat to ecosystem and human health. It is urgent to develop suitable and effective methods to accelerate it degradation and alleviate its negative impacts in soil. In this study, the introduction of functional microbe white-rot fungus Phanerochaete chrysosporium to remediate IMI contaminated wetland soil was carried out. The remediation performance and the response of the soil microbial community were examined. The results showed that P. chrysosporium could improve the degradation of IMI in soil no matter the soil was sterilized or not. The bioaugmentation was especially observed in non-sterilized soil under the inoculation patterns of FE and SP with the maximum IMI degradation rate of 91% and 93% in 7 days, respectively. The invertase activity in soil was also enhanced with P. chrysosporium inoculation. Microbial community analysis revealed that P. chrysosporium inoculation could increase the diversity and richness of bacterial community, and stimulate some IMI degraders genera including Ochrobactrum, Leifsonia, Achromobacter, and Bacillus. Moreover, the xenobiotic degradation and metabolism pathway was generally enhanced with P. chrysosporium inoculation based on PICRUSt analysis. These obtained results demonstrated that the introduction of white-rot fungus is of great potentially enabling the remediation of neonicotinoids contaminated soil.

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.

Physiological and metabolic alterations induced by commercial neonicotinoid formulations in Daphnia magna

Neonicotinoid insecticides are widely used agents in agriculture to control a broad range of insect pests. Although use of neonicotinoid pesticides has resulted in the widespread contamination of surface waters, sublethal toxicity data of these products in relation to non-target aquatic biota are still poor. Therefore, the objective of this study was to assess the effects of two neonicotinoid pesticides with widespread use on the basic physiological functions: the thoracic limb activity and heart rate of Daphnia magna, and to screen for their potential to affect the cytochrome P450 monooxygenase system (ECOD activity) of daphnids. The considered pesticides were the acetamiprid- and thiacloprid based products Mospilan 20 SG and Calypso 480 SC, respectively. The dose-dependent variation in the three biological endpoints considered were assessed following 24 h exposures. The two neonicotinoid formulations elicited significant depression on the thoracic limb activity and heart rate of daphnids at doses close to the immobility thresholds of formulations (48h-EC₅₀: Mospilan 20 SG = 190 mg L^-1; Calypso 480 SC = 120 mg L^-1), an effect mainly attributable to the overall drop in the general health status of the organisms. The alterations in the physiological traits were significant at exposures to 190 mg L^-1 for Mospilan 20 SG and 48 mg L^-1 for Calypso 480 SC. The dose related variation in the ECOD activity of daphnids exposed to the selected neonicotinoid formulations followed a biphasic pattern, with starting effective doses for Mospilan 20 SG of 6.3 mg L^-1 (=1/20 of 48h-EC₅₀ for Daphnia neonates), and for Calypso 480 SC of 0.034 mg L^-1 (=1/4000 of 48h-EC₅₀). Maximal ECOD activity (2.2 fold increase vs. controls) was induced by Mospilan 20 SG in daphnids exposed to 114 mg L^-1 product (=48 h-EC₂₀), and by Calypso 480 SC (1.8 fold increase) at 5.2 mg L^-1 dose (=1/20 of 48 h-EC₅₀). Our results outlined significant alterations in the physiological traits and ECOD activity in exposed daphnids at concentrations below the immobility thresholds (48 h-EC₅₀) of the products used as benchmarks to rate their toxicity risks to aquatic biota. Therefore, we think our findings might deserve consideration in the environmental risk evaluation of these products.