A nationwide survey of urinary concentrations of neonicotinoid insecticides in China

Occurrence and distribution of neonicotinoids and characteristic metabolites in paired urine and indoor dust from young adults: Implications for human exposure

Neonicotinoid insecticides (NEOs) are widely used for pest control worldwide. The profile of NEOs in paired urine and indoor dust has not yet been reported in China. In this study, 40 paired samples (i.e., 160 urine and 40 indoor dust) were collected from university students and dormitories from Guangzhou City of China to measure the concentrations of six NEOs and their three metabolites. Target analytes were frequently detected in paired urine (81%-98%) and indoor dust (75%-95%) samples, with median concentrations ranging from 0.02 [specific gravity (SG) adjusted: 0.02] to 2.08 (SG-adjusted: 2.38) ng/mL in urine and from 0.05 to 2.74 ng/g in indoor dust. 5-Hydroxy-imidacloprid was predominant in urine, while N-desmethyl acetamiprid was predominant in indoor dust samples, accounting for 56% and 37%, respectively. 1-Methyl-3-(tetrahydro-3-furylmethyl) urea, a dinotefuran degradate, was measured for the first time in indoor dust, with the median level of 1.02 ng/g. Significant gender-related differences (p < 0.05) in the urinary concentrations of most NEOs were found. We calculated the estimated daily intake (EDI) of target compounds from urine and indoor measurements. The EDIs of target analytes varied among all urine and indoor dust samples, with median values ranging from 0.51 (SG-adjusted: 0.56) to 51.6 (SG-adjusted: 52.8) ng/kg bw/day and from 0.04 to 2.10 pg/kg bw/day, respectively. Moreover, the median EDIs_urine of most target analytes in females were significantly higher than (p < 0.05) those in males. The median EDIs_dust of target compounds in dust from female dormitories were slightly higher than that in dust from male dormitories. These findings indicated that females were more exposed to NEO than males. Thus, the potential health risks of exposure to NEOs and their metabolites in female adults should be addressed in future studies. To our knowledge, this study is the first to report the profiles of NEOs and their metabolites in paired urine and indoor dust samples from young adults in China.

Serum concentrations of neonicotinoids, and their associations with lipid molecules of the general residents in Wuxi City, Eastern China

Exposure to neonicotinoid insecticides (NNIs) was proven to be harmful to organisms, however, there is a dearth of information regarding their occurrence and adverse effects on the general residents. Here, n = 120 human serum samples were collected from the same area of Wuxi city, Eastern China, and these serum samples were further analyzed for nine NNIs and nine target lipid molecules by use of ultrahigh performance liquid chromatography-quadrupole orbitrap high-resolution mass spectrometer. We observed that four out of nine NNIs exhibited relatively high detection frequencies (DF), and these NNIs were imidacloprid (IMI; DF = 28.3%), clothianidin (CLO; 16.7%), thiacloprid (THI; 14.2%), and acetamiprid (ACE; 12.5%), respectively, with 95th concentrations ranging from 32.0 to 427 pg/mL. Median concentrations of imidacloprid-equivalent total neonicotinoids (IMI_eq) and ∑₇NNI were 46.6 pg/mL and 26 pg/mL, respectively. Five out of nine lipid molecules exhibited higher levels, that were docosahexaenoic acid [FA(22:6)], 18:0 phosphocholine [LysoPC(18:0)], 18:0 phosphoethanolamine [LysoPE(18:0)], D18:1-18:0 sphingomyelin [SM(d18:1/18:0)], and 18:1-18:1 diglycerol [DG(18:1/18:1)], respectively. More interestingly, we observed statistically significant correlations (student's t-test, one-way ANOVA, or Mann-Whitney test; p < 0.05) between NNI levels and population characteristics (i.e. age, smoking, and health status). Beyond that, we also observed statistically significant correlations between levels of selected NNIs (CLO, ACE, or THI) and lipid molecules [LysoPE(18:0), SM(d18:1/18:0), and DG(18:1/18:1)]. Collectively, for the first time, we provided the information on contamination levels of NNIs in serum samples of general residents in China and demonstrated the associations between concentrations of NNIs and levels of lipid molecular species.

Non-Occupational Exposure to Pesticides: Experimental Approaches and Analytical Techniques (from 2019)

BACKGROUND

Pesticide residues are a threat to the health of the global population, not only to farmers, applicators, and other pesticide professionals. Humans are exposed through various routes such as food, skin, and inhalation. This study summarizes the different methods to assess and/or estimate human exposure to pesticide residues of the global population.

METHODS

A systematic search was carried out on Scopus and web of science databases of studies on human exposure to pesticide residues since 2019.

RESULTS

The methods to estimate human health risk can be categorized as direct (determining the exposure through specific biomarkers in human matrices) or indirect (determining the levels in the environment and food and estimating the occurrence). The role that analytical techniques play was analyzed. In both cases, the application of generic solvent extraction and solid-phase extraction (SPE) clean-up, followed by liquid or gas chromatography coupled to mass spectrometry, is decisive. Advances within the analytical techniques have played an unquestionable role.

CONCLUSIONS

All these studies have contributed to an important advance in the knowledge of analytical techniques for the detection of pesticide levels and the subsequent assessment of nonoccupational human exposure.

Profiles of neonicotinoid insecticides and characteristic metabolites in paired urine and blood samples: Partitioning between urine and blood and implications for human exposure

Neonicotinoid insecticides (NEOs) are widely used for pest control worldwide. However, only a few studies have analyzed NEOs and their metabolites in blood samples, and no study has measured the concentrations of NEOs and their metabolites in paired urine and blood samples. In this study, six NEOs and three characteristic metabolites were detected in 196 paired urine and blood samples collected from young adults from China. The NEOs and their metabolites were widely detected in paired urine (67%-91%) and blood (64%-97%) samples, and the median levels ranged within 0.01-1.15 ng/mL in urine and 0.08-0.80 ng/mL in blood. Olefin-imidacloprid (Of-IMI) and 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) were the most abundant target compounds in the urine (32.4%) and blood (26.4%) samples, respectively. Gender-related differences were observed in the concentrations of most NEOs and their metabolites in the urine and blood samples. The partitioning of target analytes between blood and urine (NEOs-B/NEOs-U ratios) was also calculated in this study. The B/U ratios of most NEOs and their metabolites were below 1, and positive correlations were observed between urine and blood in most levels of NEOs and their metabolites. This finding indicates that urinary levels are good predictors of human exposure to NEOs and their metabolites. The estimated daily intake (EDI) and the imidacloprid-equivalent (IMI_eq) levels of NEOs and their metabolites in 196 young adults were also determined. The median EDI values (ng/kg bw/day) of ΣNEOs (sum of NEOs and their metabolites) and IMI_eq in females (194.9 and 458.2) were slightly higher than (p > 0.05) those in males (157.1 and 439.7). This finding shows young adults are extensively exposed to NEOs and their metabolites. To our knowledge, this study is the first to report about NEOs and their metabolites in paired samples of urine and blood in China.

Measuring urinary concentrations of neonicotinoid insecticides by modified solid-phase extraction-ultrahigh performance liquid chromatography-tandem mass spectrometry: Application to human exposure and risk assessment

Neonicotinoid insecticides are the most widely used insecticides in the world. However, some experiments in vivo and vitro have shown association between neonicotinoids exposure and adverse effects in non-target mammals. The aims of this study were to 1) develop a robust method for simultaneous quantification of urinary neonicotinoids with a wide water solubility range by modified solid-phase extraction-ultrahigh performance liquid chromatography- tandem mass spectrometry and 2) quantify the concentrations of ten neonicotinoids in 386 adolescents in Chongqing of Southwest China by using the developed method and assess health risks of exposure to neonicotinoids. The introduction of extractive crystallization effectively removed interfering inorganic salts and improved the sensitivity of the method. The mean recoveries of all the analytes were satisfactory in the range of 89.1-104.8% and the limits of detection ranged from 0.001 to 0.02 ng/mL. The developed method was sensitive, accurate and suitable for trace detection and batch analysis in biomonitoring-based studies. Of the ten examined neonicotinoids, acetamiprid had the highest geometric mean concentration (49.43 μg/g creatinine), followed by clothianidin (5.01), imidacloprid (3.80), thiamethoxam (3.24), thiacloprid (2.25), nitenpyram (1.79), dinotefuran (1.76), sulfoxaflor (1.65), imidaclothiz (1.28) and flonicamid (1.01). High detection rates of neonicotinoids (79.3-100.0%) indicated a ubiquitous adolescents' exposure to neonicotinoids in urban areas of Chongqing. Nevertheless, hazard quotient and hazard index data exhibited a low health risk caused by the individual and cumulative exposure to neonicotinoids on the basis of the reference limit values recommended by the U.S. Environmental Protection Agency and the National Food Safety Standard of China.

Potential Environmental Health Risk Analysis of Neonicotinoids and a Synergist

The extensive use of neonicotinoid pesticides has led to their widespread presence in the environment, resulting in considerable safety risks to the ecosystem and human health. In this study, we investigated the biotransformation behavior of a cocktail of multiple neonicotinoids and piperonyl butoxide (PBO) synergist in vivo and their potential environmental health risk. It was found that neonicotinoids with a cyano group, such as acetamiprid and thiacloprid, tended to accumulate in liver and spleen tissues, while others with nitro groups (imidacloprid, thiamethoxam, clothianidin, dinotefuran, and nitenpyram) were mostly excreted in urine. In the presence of the synergist PBO, the metabolism of neonicotinoids in vivo changed, mainly through the nitro reduction pathway, while a low abundance of related metabolites was observed in the conventional hydroxylation and demethylation metabolic pathways, due to inhibition of CYP450 enzymes by the synergist. Furthermore, DNA methylation damage in vivo was exacerbated by the induction of hydroxylamine metabolites formed in the intermediate process of neonicotinoid metabolism with the synergistic effect of PBO, which resulted in a higher level of the O⁶-methyldeoxyguanosine (O⁶-medG) biomarker in the liver. Therefore, during the comprehensive evaluation of pesticide environmental risks, attention should be paid not only to the co-exposure mode under real environmental conditions but also to the potential risks of intermediate metabolism and related intermediate metabolites. This study provides a referential strategy and theoretical support for the health risk assessment of co-exposure of chemicals.

A method for the analysis of 121 multi-class environmental chemicals in urine by high-performance liquid chromatography-tandem mass spectrometry

Biomonitoring of human exposure to environmental chemicals has gained momentum in recent years. Biomonitoring methods often include analysis of a single class of chemicals with similar chemical properties. In this study, we describe a method that involves solid-phase extraction (SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and capable of measuring 121 environmental chemicals comprising plasticizers (PMs; n = 45), environmental phenols (EPs; n = 45), and pesticides (n = 31) through a single extraction of urine. Urine samples were incubated with 20 µL of β-glucuronidase/arylsulfatase (4000 units/mL urine) (from Helix pomatia) buffered at pH 5.5 for 2 h at 37 °C for optimal deconjugation conditions. We compared two extraction methods, namely liquid-liquid extraction and SPE, and the latter with ABS Elut NEXUS® cartridges was optimized to yield best extraction efficiencies. For increased resolution and chromatographic separation, two methods involving Ultra AQ C18® and Betasil™ C18® columns were used. The MS/MS analyses were performed under both negative and positive ionization modes. The optimized method yielded excellent intra- and inter-day variabilities (relative standard deviation: 0.40-11%) and satisfactory recoveries (80-120%) for >95% of the analytes. The limits of detection were ≤ 0.1 ng/mL for 101 analytes and between 0.1 and 1.0 ng/mL for 18 analytes. The optimized SPE LC-MS/MS method was validated through the analysis of standard reference materials and proficiency test urine samples and further applied in the analysis of 21 real urine samples to demonstrate simultaneous determination of 121 environmental chemicals in urine samples.

Health risks to dietary neonicotinoids are low for Chinese residents based on an analysis of 13 daily-consumed foods

Neonicotinoid pesticide residues are ubiquitous in various foodstuffs and may adversely affect human health. We performed a nationwide survey of neonicotinoid residues in foodstuffs collected from Chinese markets and evaluated the risks of chronic and acute exposure in 1-6-year-old children and the general population. Among the 3406 samples of 13 commodities, 62.21% contained neonicotinoids with concentrations ranging from 0.1 to 1471.43 μg/kg, and 37.58% were simultaneously contaminated with 2-7 neonicotinoids. Acetamiprid, thiamethoxam, and imidacloprid were the top three detected neonicotinoids (22.14-34.32% of samples). Chronic and acute cumulative risk assessment using the relative potency factor method revealed that exposure to neonicotinoids was within established safety limits (below 1); however, the acute risk was much greater than the chronic risk (chronic hazard index range, 1.40 × 10^-6-2.33 × 10^-3; acute hazard index range, 1.75 × 10^-6-0.15). A relatively greater acute cumulative risk was found for children with respect to consumption of grapes, mandarins, and cowpeas (acute hazard index range, 0.11-0.15). Despite the low health risk, the potential health hazards of neonicotinoids should be continuously assessed, given their ubiquity and cumulative effects.

Profiles of neonicotinoid insecticides and their metabolites in paired saliva and periodontal blood samples in human from South China: Association with oxidative stress markers

Neonicotinoid insecticides (NEOs) are widely used around the world. The distribution of NEOs in paired saliva and periodontal blood samples was not previously documented in China. In this study, the concentrations of six NEOs and three corresponding metabolites were measured in 188 paired saliva and periodontal blood samples collected from South China. NEOs and their metabolites were frequently detected (68-94%) in paired saliva and periodontal blood, with median levels of 0.01-0.99 ng/mL. 1-Methyl-3-(tetrahydro-3-furylmethyl) urea was the most predominant NEO in paired saliva (39%) and periodontal blood (42%). Gender-related differences in NEOs and their metabolite concentrations were found: males showed lower levels than females. We calculated the concentration ratios between saliva and periodontal blood (S/PB ratios), and found that the median S/PB ratios of NEO and their metabolites were higher than 1, indicating that NEOs and their metabolites were easily excreted via saliva. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) was measured in paired saliva and periodontal blood as a marker of oxidative stress. 8-OHdG concentrations in saliva and periodontal blood were significantly and positively correlated (p < 0.05) with the concentrations of most NEOs and their metabolites in saliva and periodontal blood samples. These findings indicated that exposure to NEOs and their metabolites is associated with oxidative stress. This study is the first to report NEOs and their metabolites in paired saliva and periodontal blood samples collected from South China.

Functional alterations by a subgroup of neonicotinoid pesticides in human dopaminergic neurons

Neonicotinoid pesticides, originally developed to target the insect nervous system, have been reported to interact with human receptors and to activate rodent neurons. Therefore, we evaluated in how far these compounds may trigger signaling in human neurons, and thus, affect the human adult or developing nervous system. We used SH-SY5Y neuroblastoma cells as established model of nicotinic acetylcholine receptor (nAChR) signaling. In parallel, we profiled dopaminergic neurons, generated from LUHMES neuronal precursor cells, as novel system to study nAChR activation in human post-mitotic neurons. Changes of the free intracellular Ca²⁺ concentration ([Ca²⁺]_i) were used as readout, and key findings were confirmed by patch clamp recordings. Nicotine triggered typical neuronal signaling responses that were blocked by antagonists, such as tubocurarine and mecamylamine. Pharmacological approaches suggested a functional expression of α7 and non-α7 nAChRs on LUHMES cells. In this novel test system, the neonicotinoids acetamiprid, imidacloprid, clothianidin and thiacloprid, but not thiamethoxam and dinotefuran, triggered [Ca²⁺]_i signaling at 10-100 µM. Strong synergy of the active neonicotinoids (at low micromolar concentrations) with the α7 nAChR-positive allosteric modulator PNU-120596 was observed in LUHMES and SH-SY5Y cells, and specific antagonists fully inhibited such signaling. To provide a third line of evidence for neonicotinoid signaling via nAChR, we studied cross-desensitization: pretreatment of LUHMES and SH-SY5Y cells with active neonicotinoids (at 1-10 µM) blunted the signaling response of nicotine. The pesticides (at 3-30 µM) also blunted the response to the non-α7 agonist ABT 594 in LUHMES cells. These data show that human neuronal cells are functionally affected by low micromolar concentrations of several neonicotinoids. An effect of such signals on nervous system development is a toxicological concern.

Occurrence of neonicotinoid insecticides and their metabolites in tooth samples collected from south China: Associations with periodontitis

Neonicotinoid insecticides (NEOs) are widely used in agricultural production processes in China and worldwide. NEOs have been an increasing concern because of their potential toxicity to nontarget organisms. However, studies that focused on human exposure to NEOs in China are limited. In this study, levels of six parent NEOs (p-NEOs), namely imidacloprid (IMI), acetamiprid (ACE), clothianidin (CLO), dinotefuran (DIN), thiamethoxam (THIX), and thiacloprid (THI), and three metabolites (m-NEOs), such as 5-hydroxy-imidacloprid (5-OH-IMI), 1-methyl-3-(tetrahydro-3-furyl methyl) urea (UF), and N-desmethyl-acetamiprid (N-dm-ACE) were measured in 127 tooth samples collected from South China. P-NEOs and m-NEOs are frequently detected (76%-93%) in tooth samples, with median levels of 0.03-1.20 ng/g. UF is the most abundant NEOs in tooth samples (36%). Females have higher NEO levels than males, and gender-related differences in NEO levels are found. Associations among most p-NEOs are also found (p < 0.05), indicating the source of human exposure to p-NEOs is related. However, no significant relationships (p > 0.05) between levels of m-NEOs and their corresponding p-NEOs are found, suggesting that exogenous m-NEOs contribute to exposure. We have also examined the associations between human NEOs exposure and periodontitis, and associations between NEO exposure and periodontitis are observed (OR = 2.63-7.33; 95% CI = 1.01-21.1, p-trend < 0.05). Our results suggest that NEO levels are associated with increased odds of prevalent periodontitis. This study is the first to report about p-NEOs and m-NEOs in tooth samples collected from South China.

Study on the binding mechanism of thiamethoxam with three model proteins:spectroscopic studies and theoretical simulations

As a top-selling neonicotinoid insecticide widely used in the field, thiamethoxam is an environmental pollutant because of the accumulation in ecosystem and has also been reported that it has potential risks to the health of mammals even humans. In order to understand the binding mechanism of thiamethoxam with biological receptors, spectroscopic techniques and theoretical simulations was used to explore the specific interactions between thiamethoxam and proteins. Interestingly, the results indicated that hydrophobic interaction as the main driving force, thiamethoxam formed a single binding site complex with proteins spontaneously, resulting in a decrease in the esterase-like activity of human serum albumin. The results of computer simulation showed that there were hydrophobic, electrostatic and hydrogen bonding interactions between thiamethoxam and receptors. The results of experiment and computer simulation were mutually confirmed, so a model was established for the interaction between the two which uncovered the structural characteristics of the binding site. This research provided new insights for the structure optimization of thiamethoxam, as well as gave an effective reference for evaluating the risk of thiamethoxam systemically in the future.

Neonicotinoids, fipronil, chlorpyrifos, carbendazim, chlorotriazines, chlorophenoxy herbicides, bentazon, and selected pesticide transformation products in surface water and drinking water from northern Vietnam

Studies on the occurrence of emerging pesticides in surface and drinking water in Vietnam are limited. In this study, lake water (n = 7), river water (n = 1), tap water (n = 46), and bottled water (n = 3) collected from Hanoi and other four provinces in northern Vietnam were analyzed for selected pesticides (including insecticides such as neonicotinoids, fipronil, and chlorpyrifos; fungicide carbendazim; herbicides such as atrazine, terbuthylazine, simazine, 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and bentazon) and some of their degradates by liquid chromatography-tandem mass spectrometry. Carbendazim (median: 86.7 ng/L) and triazines (49.3 ng/L) were the major pesticides found in lake water samples, followed by neonicotinoids and their degradation products (15.1 ng/L), chlorpyrifos and its degradate (13.4 ng/L), fipronil and its degradates (3.76 ng/L), chlorophenoxy acid herbicides (2.10 ng/L), and bentazon (0.62 ng/L). Triazines (164 ng/L) were the major pesticides in river water. Higher concentrations (median: 39.3 ng/L; range: 1.20-127) of selected pesticides were found in tap water from Hanoi than those from four other provinces studied (5.49 ng/L; 4.73-66.8 ng/L). Bottled water samples collected from Hanoi contained lower concentrations of pesticide residues (median: 3.54 ng/L, range: 2.18-8.09) than those of tap water samples. The calculated risks from pesticide exposure through ingestion of tap water by the general populations were low. However, fipronil concentrations in lake water exceeded the benchmark value recommended for freshwater in the United States or the Netherlands. Degradation of acetamiprid into desmethyl-acetamiprid was found in lake water.

A syringe-aided apta-nanosensing method for colorimetric determination of acetamiprid

A syringe-aided apta-nanosensing method is reported for the colorimetric determination of acetamiprid. The method employs double-stranded (ds) DNA-conjugated gold nanoparticle@magnetic agarose beads, i.e., dsDNA-AuNP@MABs as peroxidase-mimicking composite probes, in which the aptamer is indirectly attached to the AuNP surface through its hybridization with complementary DNA (cDNA). Upon contact with the acetamiprid target, the probes can give perceptible color change due to the possible conformation switch from dsDNA's brush-like to cDNA's 'pancake' regime. An "air-spaced pumping" procedure using a syringe equipped with ring magnets as the operation platform was proposed to facilitate the magnetic separation of the sensing probes. Therefore, the analytical steps can be easily accomplished in a syringe, including probe loading, acetamiprid capture and magnetic separation from crude samples, chromogenic reagent loading and colorimetric visualization. Acetamiprid concentration down to 3.3 ppb can be easily identified by the naked eye. The final solution also can be transferred for quantitative measurement. Under spectrometer, the ratio of the absorbance at 652 nm in the presence and absence of acetamiprid (A/A₀) is linearly related to the acetamiprid concentration in the 0.4-4.5 ppb range. The limit of detection is calculated to be 0.24 ppb. Moreover, satisfactory recoveries ranging from 90.90 to 91.82% with relative standard deviations of ≤2.96% were obtained in analyzing real spiked samples.

Profiles of urinary neonicotinoids and dialkylphosphates in populations in nine countries

The application of neonicotinoid insecticides (neonics) has increased dramatically as a replacement for organophosphate pesticides (OPs) in recent years. Nevertheless, little is known about human exposure to these pesticides in various countries. In this study, concentrations of 14 neonics and six dialkylphosphate metabolites (DAPs) were determined simultaneously in 566 urine samples collected from nine countries during 2010-2014. The highest sum concentration of 14 neonics was found in urine from Vietnam (median: 12.2 ng/mL) whereas that of six DAPs was from China (18.4 ng/mL). The median concentrations of ∑6 DAPs were twice higher than those of ∑14 neonics across the nine countries, which suggested a greater exposure to OPs than neonics. The overall pattern of urinary pesticide concentrations was similar among the nine countries with dimethylphosphate (DMP) and dimethylthiophosphate (DMTP) accounting for 51-89% of the total pesticide concentrations. Differences in urinary pesticide concentrations between genders (female and male), age groups (≤20, 21-49, and ≥50 years), and regions (cities of Shanghai, Guangzhou and Qiqihar) were examined. Total daily exposure doses to OPs were highest in China (515 μg/day) with 15% of the samples exceeding the U.S. Environmental Protection Agency's reference dose for chlorpyrifos (18 μg/day). This is the first study to establish baseline levels of OP and neonics exposure in general populations across nine countries.

Transformation and removal of imidacloprid mediated by silver ferrite nanoparticle facilitated peroxymonosulfate activation in water: Reaction rates, products, and pathways

Imidacloprid (IMI) is one of the most extensively used chlorinated organic pesticides and its widespread occurrence makes it attract increased public concern and scientific interest. Peroxymonosulfate (PMS) activation has been widely studied for the elimination of organic pollutants from water. But few studies are focused on their heterogeneous catalytic performance towards imidacloprid especially with the presence of silver ferrite nanoparticles (nAgFeO₂)-based catalysts. Herein, the catalyst, nAgFeO₂, was prepared via a co-precipitation method, and further applied to activate PMS for the removal of imidacloprid (IMI). Our results demonstrated that the prepared nAgFeO₂ significantly promoted the activation of PMS for removing IMI, and the removal of IMI followed a pseudo first-order kinetics model with the corresponding nAgFeO₂ dosage. Electron paramagnetic resonance (EPR) and quenching tests revealed the singlet oxygen (¹O₂)-mediated nonradical pathway, instead of hydroxyl radical (•OH) or sulfate radical (SO₄^•-), played the dominant role in the degradation of IMI. Eight products were identified and the degradation pathways of IMI were proposed. It is postulated that the primary site at the C-1 position of IMI was more easily attacked by the •OH yielding (6-chloropyridin-3-yl) methanol). While the site at the amidine nitrogen (2) of IMI was more likely attacked by the ¹O₂, and then reacted with •OH to produce 5-hydroxy imidacloprid. Overall, this study provides insights into the mechanisms of nonradical oxidation processes based on PMS for the elimination of pesticides from water, broadening the application of silver ferrite nanoparticles in wastewater treatment.

Neonicotinoid insecticide and their metabolite residues in fruit juices: Implications for dietary intake in China

Neonicotinoid insecticides (NEOs) have become the most widely used insecticides worldwide, and they are ubiquitous in food (i.e., fruit juices). In the present study, occurrence of seven NEOs and four metabolites (m-NEOs) in 400 fruit juice samples were investigated. NEOs and m-NEOs were frequently detected (65%-86%) in fruit juice samples. The median residues of NEOs and m-NEOs were ranged from 0.06 ng/mL to 0.94 ng/mL. Seasonal variations in NEOs and m-NEOs in fruit juices were found, indicating that the target analyte residues during the dry season were remarkably higher than those of residues during wet season. The relative potency factor (RPF) method was used to integrate individual NEOs into a single metric [imidacloprid (IMI_RPF)] representing the intakes of IMI equivalent to total NEOs for each fruit juice sample. The estimated daily intake (EDI) of total NEOs for the general Chinese population was obtained. The median IMI_RPF for total fruit juices was 13.4 ng/g, and the median EDI of NEOs was 18.2 ng/kg bw/day for the general population. Although the EDIs in this study were considerably lower than the acceptable daily intake (60 μg/kg bw/day, ADI), the dietary exposure risks for total NEOs should not be ignored because of the increasing usage of NEOs and their ubiquitous presence in fruit juices in China. To the best of our knowledge, this report was the first time to document residues of NEO and m-NEO in fruit juice samples collected from China.

Nationwide Biomonitoring of Neonicotinoid Insecticides in Breast Milk and Health Risk Assessment to Nursing Infants in the Chinese Population

Presently, the potential health risks of neonicotinoid insecticides (neonics) are now receiving much attention, but no data regarding the exposure of infants to neonics via human breast milk intake have been reported. In this study, a nationwide survey was conducted during the period of 2017-2019, wherein 97 pooled breast milk samples were collected from 3570 lactating women of 23 provinces in China. Nationally, acetamiprid-N-desmethyl was the most predominant compound, accounting for 61.2% of the total amount of neonics, followed by imidacloprid (15.6%). The concentration of the sum of acetamiprid and its metabolite acetamiprid-N-desmethyl in breast milk was positively correlated with corresponding dietary exposure, while no statistically significant association between the other neonic levels in breast milk and dietary exposure was found. The cumulative daily intakes of neonics (9.40-249 ng kg^-1 of body weight day^-1) were estimated for breastfed infants, indicating a minuscule risk to Chinese infants from neonic exposure via breastfeeding.

Characteristics of Exposure of Reproductive-Age Farmworkers in Chiang Mai Province, Thailand, to Organophosphate and Neonicotinoid Insecticides: A Pilot Study

Exposure to insecticides containing organophosphate (OP) and neonicotinoid (NEO) compounds has been associated with adverse reproductive health outcomes. This study characterized and identified predictors of exposure to OP and NEO among 100 reproductive-age farmworkers from two intensive farming areas in Chiang Mai Province, Thailand, including 50 each from the Fang (FA) and Chom Thong (CT) districts. OP exposure was determined by measuring the urinary concentrations of six dialkylphosphates (DAPs), whereas NEO exposure was determined by measuring the urinary concentrations of NEO compounds and their metabolites (NEO/m). The most frequently detected OPs were diethylphosphate (DEP) and diethylthiophosphate (DETP), with DETP having the highest geometric mean (GM) concentration, 8.9 μg/g-creatinine. The most frequently detected NEO/m were N-desmethyl-acetamiprid (N-dm-ACE), imidacloprid (IMI), and thiamethoxam (THX), with IMI having the highest GM concentration, 8.7 μg/g-creatinine. Consumption of well water was the predominant determinant of OP and NEO exposure in this population. In addition to encouraging workers to use personal protective equipment, exposure of farmworkers to these compounds may be reduced by nation-wide monitoring agricultural insecticides and other pesticides in community drinking water resources.

Evaluation of modes of action of pesticides to Daphnia magna based on QSAR, excess toxicity and critical body residues

Agricultural pesticides serve as effective controls of unwanted weeds and pests. However, these same chemicals can exert toxic effects in non-target organisms. To determine chemical modes of action, the toxicity ratio (TR) and critical body residues (CBRs) of 57 pesticides were calculated for Daphnia magna. Results showed that the CBR values of inert compounds were close to a constant while the CBR values of pesticides varied over a wider range. Although herbicides are categorized as specifically-acting compounds to plants, herbicides did not exhibit excess toxicity to Daphnia magna and were categorized as inert compounds with an average logTR = 0.41, which was less than a threshold of one. Conversely, fungicides and insecticides exhibited strong potential for toxic effects to Daphnia magna with an average logTR >2. Many of these chemicals act via disruption of the nervous, respiratory, or reproductive system, with high ligand-receptor binding activity which leads to higher toxicity for Daphnia magna. Molecular docking using acetylcholinesterase revealed that fungicides and insecticides bind more easily with the biological macromolecule when compared with inert compounds. Quantitative structure-activity relationship (QSAR) analysis revealed that the toxicity of fungicides was mainly dependent upon the heat of formation and polar surface area, while the toxicity of insecticides was more related to hydrogen-bond properties. This comprehensive analysis reveals that there are specific differences in toxic mechanisms between fungicides and insecticides. These results are useful for determining relative risk associated with pesticide exposure to aquatic crustaceans, such as Daphnia magna.

Predictors, sources, and health risk of exposure to neonicotinoids in Chinese school children: A biomonitoring-based study

BACKGROUND

Recent studies have suggested an extensive exposure to neonicotinoids in human, but the information on predictors, sources, and health risk remains limited in children.

OBJECTIVE

To explore the predictors, sources, and health risk for exposure of Chinese school children to neonicotinoids by biomonitoring method.

METHODS

In 2019, 309 school children aged 7-11 years were selected from a dynamic cohort of children established in Shanghai, East China. Eight neonicotinoids and four metabolites were determined in first morning urine. After detailed information on demographic and socioeconomic indices, intake of drinking water, food consumption, and anthropometric measurements was collected, the predictors and sources of exposure to neonicotinoids were explored by binary and ordinal logistic regression models. Health risk was assessed by the hazard quotient (HQ) and hazard index (HI) based on estimated daily exposure dose.

RESULTS

Six neonicotinoids (thiamethoxam, clothianidin, imidacloprid, acetamiprid, nitenpyram, and dinotefuran) and three metabolites (N-desmethyl-thiamethoxam, N-desmethyl-clothianidin, and N-desmethyl-acetamiprid) were detected in 81.3% of urine samples. Children in nuclear family or girls had a higher detection frequency of thiamethoxam. N-desmethyl-acetamiprid was more likely to be detected in children who were older, physically active, or obese. Parents' occupation was heterogeneously associated with the detection of thiamethoxam and clothianidin. Thiamethoxam and clothianidin were more likely to be detected in children consuming more fresh vegetables in all or its specific items of cabbage, nori, and kelp. N-desmethyl-acetamiprid was more likely to be detected in children who drank more tap water. The maximum HQ and HI were 0.3522 and 0.5187, respectively, and 2.8% of children had a HI between 0.1 and 1.

CONCLUSION

Predictors for the exposure of children to neonicotinoids included demographic and socioeconomic factors, physical exercise, and relative body weight. Tap water and fresh vegetables were potential sources. A low risk was posed on children's health by the neonicotinoids.

Serum concentrations of pesticides including organophosphates, pyrethroids and neonicotinoids in a population with osteoarthritis in Saudi Arabia

Human exposure to pesticides is widespread and has received much attention in recent years because of its link to adverse health outcomes. Measurement of urinary concentrations of pesticides and their metabolites is often used in the assessment of body burdens of these chemicals. However, pesticides and their metabolites can be present in blood circulatory system, although little is known on serum levels of pesticides. In this study, we aimed to examine the occurrence and profile of four organophosphate (OP), five pyrethroid (PYR) insecticides, two phenoxy acid (PA) herbicides, 14 neonicotinoid (neonic) insecticides and six dialkylphosphate metabolites in serum from 25 individuals diagnosed with osteoarthritis in Jeddah, Saudi Arabia. 2-Isopropyl-4-methyl-6-hydroxypyrimidine (IMPY), 3,5,6-trichloro-2-pyridinol (TCPY), 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, 3-phenoxybenzoic acid, N-desmethyl acetamiprid, dimethylphosphate (DMP) and dimethylthiophosphate (DMTP) were detected in ≥80% of the serum samples analyzed. Metabolites of OPs, DMTP (median concentration: 2.14 ng/mL), DMP (1.04 ng/mL) and TCPY (0.84 ng/mL), collectively accounted for 67-83% of the total serum pesticide concentrations. Serum concentrations of pesticides were similar to or lower than those reported in urine. Our preliminary evidence suggests that serum can be used as a matrix for the assessment of exposure to OPs, PYRs, PAs and neonics.

Evaluating imidacloprid exposure among grape field male workers using biological and environmental assessment tools: An exploratory study

Imidacloprid is a neonicotinoid insecticide commonly injected through agricultural drip irrigation systems to reduce the population of vine mealybugs (P. ficus) in grape farms. There is a growing concern of potential human health effects of imidacloprid, however, there is limited information on the exposure to imidacloprid in farm workers. Imidacloprid exposure was evaluated in this exploratory study of 20 male migrant grape workers sampled five days after imidacloprid was injected in the irrigation system during winter and summer seasons. We administered a questionnaire on work activities, exposure characteristics, and socio-demographics and collected personal air, hand wipe, and spot urine samples. Heat exposure was also assessed. Spearman's correlation coefficients and Wilcoxon rank-sum tests were utilized to evaluate associations and differences in imidacloprid exposures with socio-demographic, occupational, and environmental characteristics. All participants had less than a high school education and about half identified an Indigenous language as their primary language. Although not detected in air samples, imidacloprid was detected in 85% of the hand wipes (median: 0.26: 0.41 μg/wipe, range: 0.05-7.10 μg/wipe). The majority of participants (75%) had detectable urinary concentrations of imidacloprid (median: 0.11 μg/g creatinine, range: 0.05-3.90 μg/g of creatinine), and nearly all (95%) had detectable urinary concentrations of 5-hydroxy-Imidacloprid (5-OH-IMI), a metabolite of imidacloprid (median: 1.28 μg/g creatinine, range: 0.20-27.89 μg/g creatinine). There was a significant correlation (p < 0.001) between imidacloprid in hand wipes and urinary imidacloprid and 5-OH-IMI (rs: 0.67 for imidacloprid and 0.80 for 5-OH-IMI). Hand temperature was significantly and positively correlated (p < 0.05) with imidacloprid concentration on hand wipes (rs: 0.70), and urinary biomarkers (rs: 0.68 for imidacloprid, and 0.60 for 5-OH-IMI) suggesting that working in high temperatures may influence the exposure and absorption of imidacloprid. Thus, research on farm workers would benefit in the future by evaluating imidacloprid exposure in relation to heat stress and other occupational factors.

Assessment of imidacloprid related exposure using imidacloprid-olefin and desnitro-imidacloprid: Neonicotinoid insecticides in human urine in Wuhan, China

While neonicotinoid insecticides (NNIs) have been widely used worldwide, limited studies have measured specific metabolites of imidacloprid (IMI, the most commonly used NNI) in human urine. To better understand human exposure to NNIs, 10 parent compounds, and 6 of their metabolites were analyzed in 408 urine samples collected from 129 healthy adults in Wuhan, Central China, during autumn and winter of 2018. These specimens included repeated urine samples taken in 3 d from 75 volunteers. The urinary concentrations of desnitro-imidacloprid (DN-IMI), imidacloprid-olefin (IMI-olefin), and desmethyl-acetamiprid (DM-ACE) were higher (4-40 times) than those of their parent compounds (IMI and acetamiprid, ACE). DN-IMI and IMI-olefin accounted for 92% of the urinary Σ₃IMI (the sum of IMI and its specific metabolites measured). Positive correlations (r) were observed between DN-IMI and IMI (0.50), IMI-olefin and IMI (0.75), and DM-ACE and ACE (0.53). Good to excellent inter-day reliabilities (unadjusted intraclass correlation coefficients) were observed for IMI-olefin (0.61) and DM-ACE (0.81), while moderate inter-day reliability was observed for DN-IMI (0.43). The urinary NNI concentrations were significantly higher in autumn than in winter, and higher in urban areas than in rural areas, while no significant gender or age-related differences were observed. To our knowledge, this is the first report on DN-IMI and IMI-olefin in human urine.

Urinary Metabolites of Neonicotinoid Insecticides: Levels and Recommendations for Future Biomonitoring Studies in China

Neonicotinoids (NEOs) are insecticides that are widely used around the world. Following exposure, NEOs get metabolized in human bodies. The biomarkers to assess human NEO exposure are not well described because of the lack of information on the metabolites of NEOs (m-NEOs). In this study, five m-NEOs including N-desmethyl-acetamiprid (N-dm-ACE), 5-hydroxy-imidacloprid (5-OH-IMI), olefin-imidacloprid (Of-IMI), 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine (DIN-G), and 1-methyl-3-(tetrahydro-3-furylmethyl) (DIN-U) were measured in 275 urine samples collected from 10 cities in China. All of the m-NEOs were frequently detected in urine samples with the median concentrations ranging from 0.42 (DIN-G) to 1.02 (5-OH-IMI) ng/mL. The urinary concentrations of N-dm-ACE and 5-OH-IMI measured in China were higher than those reported from Japan and the USA. In comparison to the parent NEO (i.e., acetamiprid, ACE; imidacloprid, IMI; and dinotefuran, DIN) concentrations reported in the same set of samples by our research group, the median ratios of m-NEO to the corresponding parent NEO (m-NEO/NEO) ranged from 4.95 (DIN-G/DIN) to 37.7 (N-dm-ACE/ACE), indicating that NEOs are mainly present as metabolites rather than the parent forms. Furthermore, the ratio of Σm-NEOs/ΣNEOs was significantly (p < 0.01) higher in females than in males, suggesting that NEOs are more readily metabolized in females or females are more highly exposed to m-NEOs. To our knowledge, this is the first study to measure Of-IMI, DIN-G, and DIN-U levels in urine samples from China. We recommend biomonitoring studies to include N-dm-ACE, 5-OH-IMI, and DIN-U (and DIN-G) for clear understanding of human exposure to ACE, IMI, and DIN, respectively.

A critical review on the potential impacts of neonicotinoid insecticide use: current knowledge of environmental fate, toxicity, and implications for human health

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.

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.

Variability in urinary neonicotinoid concentrations in single-spot and first-morning void and its association with oxidative stress markers

Human exposure to neonicotinoid insecticides (hereafter "neonics") is a concern. Spot urine samples have been widely used in the assessment of exposure to neonics. Urinary concentrations, however, can vary greatly over time due to variable exposure, potentially leading to exposure misclassification. In this study, within- and between-individual variability of urinary concentrations of 13 neonics and their metabolites collected consecutively for up to 44 days from 19 individuals were examined. We also measured seven oxidative stress biomarkers (OSBs) in repeated urine samples to elucidate their relationship with neonic exposure by mixed regression models. Intraclass correlation coefficients (ICCs, a ratio of between-individual variance to total variance) were used to assess the reproducibility of neonic/metabolite concentrations. Sensitivity and specificity were used to evaluate how well spot urine samples determined an individual's average exposure over 44 days. A fair to good reproducibility was observed for N-desmethyl-acetamiprid (ICC = 0.42), whereas thiamethoxam, imidacloprid, clothianidin, imidaclothiz, 6-chloronicotinic acid, and sulfoxaflor showed poor reproducibility (ICC = 0.02-0.37). Use of single-spot urine samples to classify high (top 33%) exposure showed higher specificities (0.68-0.92) than sensitivities (0.32-0.88). The minimum number of specimens (k) required to estimate participant-specific mean for neonic exposures within 20% of the "true" values ranged from 16 to 172. Significant positive correlations were found between some of neonic and OSB concentrations. The high variability found in the urinary concentrations of most neonics/metabolites suggests that a single measurement can result in exposure misclassification.