Characteristics of neonicotinoid imidacloprid in urine following exposure of humans to orchards in China

Neonicotinoid insecticides in well-developed agricultural cultivation areas: Seawater occurrence, spatial-seasonal variability and ecological risks

Neonicotinoids (NEOs) are widely used insecticides and have been detected in aquatic environments globally. However, little is known about NEOs contamination in the coastal environments under the terrestrial pressure of multiple planting types simultaneously. This study investigated the occurrence, spatial-seasonal variability, and ecological risks of NEOs along the coast of the Shandong Peninsula during the dry and wet seasons, where located many largest fruit, vegetable, and grain production bases in China. The concentrations of ∑NEOs in seawater were higher in wet seasons (surface: 195.46 ng/L; bottom: 14.56 ng/L) than in dry seasons (surface: 10.07 ng/L; bottom: 8.45 ng/L). During the wet seasons, NEOs peaked in the northern and eastern areas of the Shandong Peninsula, where the inland fruit planting area is located. While dry seasons had higher concentrations in Laizhou Bay, influenced by rivers from vegetable-growing areas. Grain crops, fruit, and cotton planting were major NEOs sources during wet seasons, while wheat and vegetables dominated in dry seasons. Moderate or above ecological risks appeared at 53.8% of the monitoring sites. Generally, NEOs caused high risks in the wet seasons mainly caused by Imidacloprid, and medium risk in the dry seasons caused by Clothianidin, which should be prevented and controlled in advance.

Associations between neonicotinoids and liver function measures in US adults: National Health and Nutrition Examination Survey 2015-2016

Background

Toxicological studies indicate that neonicotinoids may be associated with disruptions in liver function due to an increase in oxidative stress. There are scant epidemiological studies investigating the chronic hepatotoxic effects of neonicotinoids.

Objective

To examine the association between detectable concentrations of parent neonicotinoids and neonicotinoid metabolites with liver function markers among US adults, and whether sex modifies this association.

Methods

National Health and Nutrition Examination Survey 2015-2016 data were used to estimate associations between detectable neonicotinoids and serum alkaline phosphatase (ALP), alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transaminase (GGT), albumin, total bilirubin, total protein, and Hepatic Steatosis Index (HSI) using multiple linear regression.

Results

Detectable levels of N-desmethyl-acetamiprid were associated with a decrease in GGT (β = -3.54 unit/l; 95% confidence interval [CI] = -6.48, -0.61) and detectable levels of 5-hydroxy-imidacloprid were associated with a decrease in HSI (β = -1.11; 95% CI = -2.14, -0.07). Sex modified the association between any parent neonicotinoid and ALP (Pint = 0.064) and the association between clothianidin and ALP (Pint = 0.019), with a pattern of positive associations in males and inverse associations in females, though stratified associations did not reach statistical significance. Sex also modified the association between 5-hydroxy-imidacloprid and total protein (Pint = 0.062), with a significant positive association in females (β = 0.14 g/dl; 95% CI = 0.03, 0.25) and a null association in males.

Conclusion

Detectable concentrations of neonicotinoid metabolites were inversely associated with GGT and HSI in US adults. Evidence suggests neonicotinoids may influence liver function differently depending on sex. Future research is recommended to replicate the findings as the study was limited in its cross-sectional nature and inability to examine continuous neonicotinoid concentrations with liver function.

Non-acute exposure of neonicotinoids, health risk assessment, and evidence integration: a systematic review

Neonicotinoid pesticides are utilized against an extensive range of insects. A growing body of evidence supports that these neuro-active insecticides are classified as toxicants in invertebrates. However, there is limited published data regarding their toxicity in vertebrates and mammals. the current systematic review is focused on the up-to-date knowledge available for several neonicotinoid pesticides and their non-acute toxicity on rodents and human physiology. Oral lethal dose 50 (LD50) of seven neonicotinoids (i.e. imidacloprid, acetamiprid, clothianidin, dinotefuran, thiamethoxam, thiacloprid, and nitenpyram) was initially identified. Subsequently, a screening of the literature was conducted to collect information about non-acute exposure to these insecticides. 99 studies were included and assessed for their risk of bias and level of evidence according to the Office of Health and Translation (OHAT) framework. All the 99 included papers indicate evidence of reproductive toxicity, hepatotoxicity, nephrotoxicity, neurotoxicity, immunotoxicity, and oxidative stress induction with a high level of evidence in the health effect of rodents and a moderate level of evidence for human health. The most studied type of these insecticides among 99 papers was imidacloprid (55 papers), followed by acetamiprid (22 papers), clothianidin (21 papers), and thiacloprid (11 papers). While 10 of 99 papers assessed the relationship between clothianidin, thiamethoxam, dinotefuran, and nitenpyram, showing evidence of liver injury, dysfunctions of oxidative stress markers in the reproductive system, and intestinal toxicity. This systematic review provides a comprehensive overview of the potential risks caused by neonicotinoid insecticides to humans and rodents with salient health effects. However, further research is needed to better emphasize and understand the patho-physiological mechanisms of these insecticides, taking into account various factors that can influence their toxicity.

Frequency of urinary pesticides in children: a scoping review

Pesticides are any mix of ingredients and substances used to eliminate or control unwanted vegetable or animal species recognized as plagues. Its use has been discussed in research due to the scarcity of strong scientific evidence about its health effects. International literature is still insufficient to establish a global recommendation through public policy. This study aims to explore international evidence of the presence of pesticides in urine samples from children and their effects on health through a scoping review based on the methodology described by Arksey and O'Malley. The number of articles resulting from the keyword combination was 454, and a total of 93 manuscripts were included in the results and 22 were complementary. Keywords included in the search were: urinary, pesticide, children, and childhood. Children are exposed to pesticide residues through a fruit and vegetable intake environment and household insecticide use. Behavioral effects of neural damage, diabetes, obesity, and pulmonary function are health outcomes for children that are commonly studied. Gas and liquid chromatography-tandem mass spectrometry methods are used predominantly for metabolite-pesticide detection in urine samples. Dialkylphosphates (DAP) are common in organophosphate (OP) metabolite studies. First-morning spot samples are recommended to most accurately characterize OP dose in children. International evidence in PubMed supports that organic diets in children are successful interventions that decrease the urinary levels of pesticides. Several urinary pesticide studies were found throughout the world's population. However, there is a knowledge gap that is important to address (public policy), due to farming activities that are predominant in these territories.

Co-exposure of polycarbonate microplastics aggravated the toxic effects of imidacloprid on the liver and gut microbiota in mice

The joint toxicity of microplastics (MPs) and pesticides may be different from MPs or pesticides individually, however, the information about the combined toxicity of MPs and pesticides is not well understood. Herein, we investigated the joint toxicity of polycarbonate (PC) MPs and imidacloprid (IMI) on mice. After orally exposure for 4 weeks, PC and/or IMI lowered the body weight gain of mice. Single exposure of IMI induced the tissue damage in liver by disturbing the redox homeostasis, and PC significantly aggravated the imbalance of redox homeostasis by facilitating the accumulation of IMI in liver. Additionally, compared to single exposure of PC or IMI, PC+IMI exposure caused more severe damage to the gut microstructure and microbial diversity. Several key metabolic pathways, especially the lipid metabolism, were significantly affected. Overall, these findings provide new insight into understanding the potential risk of co-exposure of microplastics and pesticides to animal and human health.

Maternal exposure to neonicotinoid insecticides and fetal growth restriction: A nested case-control study in the guangxi Zhuang birth cohort

BACKGROUND

Fetal growth restriction (FGR) is a major determinant of perinatal morbidity and mortality, with adverse long-term neurocognitive effects in childhood and adulthood. Prenatal exposure to environmental pollutants has been reported to be associated with FGR. Neonicotinoids (NEOs) are extensively used insecticides worldwide and are suggested to have embryonic and developmental neurotoxicity. However, the effects of NEOs exposure on FGR is unknown.

OBJECTIVES

We aimed to quantify the single and combined associations of maternal exposure to NEOs and FGR.

METHODS

We conducted a nested case-control study based on the Guangxi Zhuang Birth Cohort, China. A total of 387 with FGR cases and 1096 without- FGR controls were included between 2015 and 2018. Ten NEOs were measured by UPLC-MS from the maternal blood samples were pre-collected in the first trimester. After adjusting for potential confounders, multivariable logistic regressions, weighted quantile sum regression and quantile g-computation were performed for individual and NEOs mixtures.

RESULTS

In the individual exposure models, each 1-standard deviation increment of the natural-log in dinotefuran and acetamiprid concentrations were significantly associated with odds ratios of 1.93 (95% CI: 1.69, 2.20) and 1.31 (95% CI: 1.07, 1.59) higher odds of FGR, respectively. However, the FGR risk was negatively associated with thiacloprid, sulfoxaflor, and nitenpyram (OR = 0.23, 95%CI: 0.15, 0.34; OR = 0.48, 95%CI: 0.41, 0.56; OR = 0.86, 95%CI: 0.80, 0.93; respectively). Similar findings were found in the combined exposure analysis. Dinotefuran was the most strongly attributable to increase FGR, while sulfoxaflor and thiacloprid contributed the highest negative weighted on FGR. Furthermore, each quintile increase in all ten NEOs exposures was associated with FGR (OR = 0.21, 95% CI: 0.08, 0.54).

CONCLUSION

Our findings suggest that maternal single and combined exposures to NEOs were associated with varying FGR risks. They contribute to the mounting evidence on serum NEOs exposure impact on FGR. However, a replication of these associations in other populations is warranted.

Neonicotinoid insecticides and their metabolites: Specimens tested, analytical methods and exposure characteristics in humans

The use of neonicotinoid insecticides (NEOs) has been rising globally due to their broad-spectrum insecticidal activity, unique mode of neurotoxic action and presumed low mammalian toxicity. Given their growing ubiquity in the environment and neurological toxicity to non-target mammals, human exposure to NEOs is flourishing and now becomes a big issue. In the present work, we demonstrated that 20 NEOs and their metabolites have been reported in different human specimens with urine, blood and hair as the dominance. Sample pretreatment techniques of solid-phase and liquid-liquid extractions coupled with high performance liquid chromatography-tandem mass spectrometry have successfully achieved matrix elimination and accurate analysis. We also discussed and compared exposure characteristics of these compounds among types of specimens and different regions. A number of important knowledge gaps were also identified in order to further facilitate the understanding of health effects of NEO insecticides, which include, but are not limited to, identification and use of neuro-related human biological samples for better elucidating neurotoxic action of NEO insecticides, adoption of advanced non-target screening analysis for a whole picture in human exposure, and expanding investigations to cover non-explored but NEO-used regions and vulnerable populations.

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.

Infantile Internal and External Exposure to Neonicotinoid Insecticides: A Comparison of Levels across Various Sources

Little is known about exposure of infants to neonicotinoid insecticides (NEOs). In this study, concentrations of six parent NEOs (p-NEOs) and N-desmethyl-acetamiprid (N-dm-ACE) were measured in urine and whole blood samples from infants, in addition to breast milk, infant formula, and tap water collected in South China. The p-NEO with the highest median concentration in urine (0.25 ng/mL) and blood (1.30) samples was dinotefuran (DIN), while imidacloprid (IMI) was abundant in breast milk (median: 0.27 ng/mL), infant formula (0.22), and tap water (0.028). The older infants (181-360 days) might face higher NEO and N-dm-ACE exposure than younger infants (0-180 days). Blood samples contained a significantly (p < 0.01) higher median concentration of ∑₆p-NEOs (2.03 ng/mL) than that of urine samples (0.41), similar to acetamiprid (ACE), IMI, thiacloprid (THD), DIN, and N-dm-ACE, suggesting that NEOs readily partition into blood. Furthermore, breast-fed infants tend to have higher exposure levels than formula-fed infants. Infant formula prepared with tap water augmented the daily intake of ∑NEOs. The external sources contributed 80% of the total dose to IMI and clothianidin (CLO) exposure, while other unknown sources contributed to ACE, THD, and DIN exposure in infants. To the best of our knowledge, this is the first study to assess levels and sources of infantile exposure to NEOs through internal and external exposure assessment.

Degradation of imidacloprid and acetamiprid in tea (Camellia sinensis) infusion by ultraviolet light irradiation

The degradation of imidacloprid and acetamiprid in tea infusion by ultraviolet (UV) light irradiation was investigated in this study. Results showed that the influence of UV light irradiation on the quality of tea infusion was controllable and UV light irradiation was effective on the degradation of both pesticides. The maximum removal rates were 75.2% for imidacloprid and 17.6% for acetamiprid after irradiation (650 µW/cm,² 120 min). The degradation of both pesticides followed the first-order kinetics model. Three degradation products were identified for imidacloprid and one for acetamiprid based on liquid chromatography-tandem mass spectrometry analysis. The degradation pathway of imidacloprid involved in the cleavage of C-C bond with the loss of nitro group followed by the hydrogenation, oxidation and hydrolysis, while the degradation of acetamiprid involved in the oxidation at the chlorine atom with the bonding of C atoms at positions 1 and 4 on the pyridine ring. Simultaneously, the toxicity of both pesticides was mitigated by UV light irradiation according to LO2 cell toxicity evaluation. The study provided a low-cost and effective way to reduce imidacloprid and acetamiprid from tea infusion, and it has the potential to be applied to the ready-to drink tea beverage production in industrial scale.

Ferroptosis contribute to neonicotinoid imidacloprid-evoked pyroptosis by activating the HMGB1-RAGE/TLR4-NF-κB signaling pathway

Imidacloprid (IMI) is among the common neonicotinoid insecticides used in agriculture worldwide, posing a potential toxic threat to non-target animals and humans. Numerous studies have shown that ferroptosis is involved in the pathophysiological progression of renal diseases. However, it remains unclear whether ferroptosis is involved in IMI-induced nephrotoxicity. In the present study, we investigated the potential pathogenic role of ferroptosis in IMI-induced kidney damage in vivo. Transmission electron microscopy (TEM) showed that the mitochondrial crest of kidney cells significantly decreased following IMI exposure. Moreover, IMI exposure triggered ferroptosis and lipid peroxidation in the kidney. We confirmed that nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant capability was negatively correlated with the ferroptosis induced by IMI exposure. Importantly, we verified that NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3)-driven inflammation occurred in the kidneys following IMI exposure, but pretreatment with the ferroptosis inhibitor ferrostatin (Fer-1) blocked this phenomenon. Additionally, IMI exposure induced F4/80⁺ macrophages to accumulated in the proximal tubules of the kidneys, and also increased the protein expression of high-mobility group box 1 (HMGB1), receptor for advanced glycation end products (RAGE), receptor for advanced glycation end products (TLR4), and nuclear factor kappa-B (NF-κB). In contrast, inhibition of ferroptosis by Fer-1 blocked IMI-induced NLRP3 inflammasome activation, F4/80 positive macrophages, and the HMGB1-RAGE/TLR4 signaling pathway. To the best of our knowledge, this is the first study to reveal that IMI stress can induce Nrf2 inactivation, thereby triggering ferroptosis, causing an initial wave of death, and activating HMGB1-RAGE/TLR4 signaling, which promotes pyroptosis that perpetuates kidney dysfunction.

Microporous carbon for fast and simple electrochemical detection of imidacloprid insecticide in fruit and water samples

Herein, a fast and sensitive electrochemical sensor was developed for imidacloprid detection using low-cost disposable microporous carbon screen-printed electrodes. The electrochemical behaviour of imidacloprid at the microporous material was investigated in detail. The developed sensor allowed imidacloprid detection in the linear range of 0.00-1.00 mM with a sensitivity of 14.43 ± 0.42 μA mM^-1 and a detection limit of 2.54 μM (3s _B/m). The sensor showed excellent selectivity and high tolerance to possible interference from other tested insecticides and ions. Excellent repeatability (3.42%, n = 3) and reproducibility (2.23%, n = 3) were demonstrated. Application of the sensor in various fruit and water samples without any treatment showed 96.2-103.0% recoveries. The developed sensor further revealed that the most effective method for removing imidacloprid residue from fruit samples was via washing with a mixture of 5% w/v NaCl and 5% w/v bicarbonate at 40 °C.

Neonicotinoid Insecticides and Their Metabolites Can Pass through the Human Placenta Unimpeded

Studies on neonicotinoid (NEO) exposure in pregnant women and fetuses are scarce, and transplacental transfer of these insecticides is unknown. In this study, parent NEOs (p-NEOs) and their metabolites (m-NEOs) were determined in 95 paired maternal (MS) and cord serum (CS) samples collected in southern China. Imidacloprid was the predominant p-NEO in both CS and MS samples, found at median concentrations of 1.84 and 0.79 ng/mL, respectively, whereas N-desmethyl-acetamiprid was the most abundant m-NEO in CS (median: 0.083 ng/mL) and MS (0.13 ng/mL). The median transplacental transfer efficiencies (TTEs) of p-NEOs and m-NEOs were high, ranging from 0.81 (thiamethoxam, THM) to 1.61 (olefin-imidacloprid, of-IMI), indicating efficient placental transfer of these insecticides. Moreover, transplacental transport of NEOs appears to be passive and structure-dependent: cyanoamidine NEOs such as acetamiprid and thiacloprid had higher TTE values than the nitroguanidine NEOs, namely, clothianidin and THM. Multilinear regression analysis revealed that the concentrations of several NEOs in MS were associated significantly with hematological parameters related to hepatotoxicity and renal toxicity. To our knowledge, this is the first analysis of the occurrence and distribution of NEOs in paired maternal-fetal serum samples.

Binding and Detoxification of Insecticides by Potentially Probiotic Lactic Acid Bacteria Isolated from Honeybee (Apis mellifera L.) Environment-An In Vitro Study

Lactic acid bacteria (LAB) naturally inhabiting the digestive tract of honeybees are known for their ability to detoxify xenobiotics. The effect of chlorpyrifos, coumaphos, and imidacloprid on the growth of LAB strains was tested. All strains showed high resistance to these insecticides. Subsequently, the insecticide binding ability of LAB was investigated. Coumaphos and chlorpyrifos were bound to the greatest extent (up to approx. 64%), and imidacloprid to a much weaker extent (up to approx. 36%). The insecticides were detected in extra- and intracellular extracts of the bacterial cell wall. The ability of selected LAB to reduce the cyto- and genotoxicity of insecticides was tested on two normal (ovarian insect Sf-9 and rat intestinal IEC-6) cell lines and one cancer (human intestinal Caco-2) cell line. All strains exhibited various levels of reduction in the cyto- and genotoxicity of tested insecticides. It seems that coumaphos was detoxified most potently. The detoxification abilities depended on the insecticide, LAB strain, and cell line. The detoxification of insecticides in the organisms of honeybees may reduce the likelihood of the penetration of these toxins into honeybee products consumed by humans and may contribute to the improvement of the condition in apiaries and honeybee health.

Trace determination of imidacloprid and its major metabolites in wheat-soil system

Trace analysis method is a reliable basis for studying the translocation and metabolism of imidacloprid used as an insecticide in wheat, and it clarifies whether biologically active metabolites including residual imidacloprid, have long-lasting insecticidal potency against wheat aphids under seed treatment during the entire growth period. In this study, a highly sensitive analytical method was established to determine the residues of imidacloprid and its six metabolites (5-hydroxy imidacloprid, imidacloprid olefin, imidacloprid guanidine, imidacloprid urea, 6-chloronicotinic acid and imidacloprid nitrosimine) in wheat-soil systems, such as in wheat leaves, wheat ears, wheat grains, roots and soil. All the compounds were extracted using an ACN:water (8:2, v/v) mixture and purified by dispersive solid-phase extraction. The average recoveries ranged from 74.4 to 109.5% for all matrices, with intra- and inter-day variations of less than 14.9%. The limit of quantitation was in the range of 0.001 to 0.005 mg/kg. The method is demonstrated to be sensitive and accurate for monitoring imidacloprid and its metabolites at trace levels during the entire growth period under field conditions. This article is protected by copyright. All rights reserved.

Exposure to neonicotinoid insecticides and their characteristic metabolites: Association with human liver cancer

Neonicotinoid insecticides (NEOs) are commonly applied for pest control in China and around the world. Previous studies reported that NEOs are hepatotoxic to mammals. However, limited studies have explored the associations between NEOs exposure and liver disease. In the present study, we detected six parent NEOs (p-NEOs), including acetamiprid, thiacloprid, dinotefuran, clothianidin, imidacloprid, and thiamethoxam, and five characteristic metabolites (m-NEOs), including 5-hydroxy-imidacloprid, olefin-imidacloprid, N-desmethyl-acetamiprid, 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine and 1-methyl-3-(tetrahydro-3-furyl methyl) urea, in blood samples collected from healthy donors (n = 100; females vs. males: 45 vs. 55; age: 22-91 years) and liver cancer patients (n = 274; females vs. males: 118 vs. 156; age: 11-88 years) in one hospital from Guangzhou city, South China. NEOs were frequently detected (61%-94%) in blood samples, with median concentrations ranging from 0.19 ng/mL to 1.28 ng/mL and 0.20 ng/mL to 2.03 ng/mL for healthy and liver cancer populations, respectively. olefin-imidacloprid was the most abundant NEOs in healthy and liver cancer populations, accounting for 23.4% and 20.7%, respectively. Significant positive correlations among most m-NEOs concentrations were found, and associations between m-NEOs and their corresponding p-NEOs were positively correlated. These findings indicated that the sources of m-NEOs were both endogenous and exogeneous. Females had higher median concentrations of NEOs and their metabolites than males. Moreover, the α-fetoprotein values and blood concentrations of target analytes (r = 0.428-0.601, p < 0.05) were positively correlated. Meanwhile, associations between the concentrations of p-NEOs and m-NEOs and liver cancer were found (odds ratio = 2.33-9.02, 95% confidence interval = 0.31-22.7, p < 0.05), indicating that human exposure to NEOs and their metabolites might increase the odds of liver cancer prevalence. Our work provided a new insight into the hepatotoxicity of NEOs and their metabolites, and human health risks of exposure to these pollutants warranted further studies.

Human exposure to neonicotinoids and the associated health risks: A review

Neonicotinoids (NEOs) are a class of broad-spectrum insecticides dominant in the global market. They were distributed extensively in the environment and occurred frequently in humans. Potential health effects of NEOs, such as neurological toxicity and diabetes to non-targeted mammals, have raised concerns. This review summarizes analytical methods of NEOs in human samples, their internal exposure levels and composition profiles in urine, blood, hair, breast milk, saliva and tooth samples with global comparisons, and daily NEOs exposure dose and relative health risks.Urinary NEOs levels in Asian populations were substantially higher than those in the U.S. and Europe, which may be due to different dietary patterns and insecticide applications across regions. N-desmethyl acetamiprid, 5-hydroxy-imidacloprid and olefin-imidacloprid were dominant among detected NEOs. NEO metabolites exhibited higher detection frequencies and levels than their parent compounds in humans, while investigations on NEO metabolites remain much limited. Current exposure assessments mainly focused on short-term urine analysis, while biomaterials for long-term monitoring, such as hair, nail and other alternatives, should also be considered. Large-scale epidemiological studies are critically needed to elucidate potential health outcomes associated with NEOs exposure.

Urinary neonicotinoid concentrations and pubertal development in Chinese adolescents: A cross-sectional study

BACKGROUND

Animal studies suggest that exposure to certain neonicotinoids may interfere with the normal function of endocrine system in mammals. However, evidence from human studies is limited.

OBJECTIVES

This study conducted a cross-sectional analysis to examine urinary neonicotinoids concentrations in Chinese adolescents and its association with pubertal development.

METHODS

774 urine samples from 439 boys (median age: 13.7 years; 25th-75th percentile: 12.7-14.5 years) and 335 girls (median age: 13.7 years; 25th-75th percentile: 12.7-14.5 years) were collected for determination of ten neonicotinoids (imidacloprid, nitenpyram, acetamiprid, thiacloprid, imidaclothiz, thiamethoxam, clothianidin, dinotefuran, flonicamid, sulfoxaflor) and one metabolite (N-desmethyl-acetamiprid). Urinary creatinine was detected for concentration adjustment. Pubertal development including pubic hair, axillary hair, genitalia (boys), testicular volume (boys) and breast (girls) assessed by Tanner stages and others (spermarche, facial hair for boys and menarche for girls) were obtained by physical examination and questionnaire. Logistic and bayesian kernel machine regression were used to investigate the association between neonicotinoids concentrations and pubertal developments.

RESULTS

High detection rates ranged from 72.0% to 100.0% for all neonicotinoids. Boys and girls with thiacloprid concentration at the >75th percentile had lower stage of genitalia development (OR: 0.83, 95% CI: 0.33-0.93) and higher stage of axillary hair development (OR: 1.46, 95% CI: 1.12-3.41), respectively, compared with those at the <25th percentile. The estimate change in genitalia stage was significantly different at or above the 75th percentile concentration of neonicotinoids mixture compared to the 50th percentile concentration. No associations were found between other urinary neonicotinoids and other indicators of puberty.

CONCLUSIONS

Higher thiacloprid concentration was associated with delayed genitalia development in boys and early axillary hair development in girls. Neonicotinoids mixture was negatively associated with genitalia stage in the joint effect. Given the characteristic of the cross-sectional study, our results need further confirmation of the causal relationship.

Assessment of ameliorative effects of organic dietary interventions on neonicotinoid exposure rates in a Japanese population

Neonicotinoid insecticides (NNIs) are a popular class of insecticides used in various pest management regimens worldwide. Biomonitoring studies continuously report high exposure rates of NNIs in various human populations across the globe. Yet, there is no validated countermeasure for combating the recent exponential rise in NNI exposure rates observed in human populations. The current study assessed the impacts of organic dietary interventions on NNI exposure rates in a Japanese population. A total of 103 volunteers were recruited into the study. Subjects were either served with Organic diets for 5 and 30 days or conventional diets. A total of 919 repeated urine samples were collected from the participants and then subjected to LC-MS/MS analysis to determine urinary concentrations of 7 NNIs parent compounds and an NNI metabolite. Eight NNIs were detected; with a decreasing detection frequency (%Dfs) pattern; desmethyl-acetamiprid (dm-ACE) (64.96%) > dinotefuran (52.12%), imidacloprid (39.61%) > clothianidin (33.95%) > thiamethoxam (28.51%) > acetamiprid (12.62%) > nitenpyram (5.33%) > thiacloprid (2.83%). Dinotefuran, dm-ACE, and clothianidin recorded the highest concentrations in the subjects. The %Df of NNIs in the 5-days or 30-days organic diet group were lower than those of the conventional diet consumers. The organic diet group showed lower rates of multiple NNI exposures than those of the conventional diet consumers. The mean and median cumulative levels of NNIs (median IMI_eq) were significantly lower in the organic diet group than the conventional diet group (p < 0.0001). The estimated daily intakes (EDIs) of NNIs were higher in adults than children, but less than 1% of NNI cRfDs, except for clothianidin, which exhibited a %cRfD of 1.32 in children. Compared to the conventional diet group, the 5- and 30-day organic dietary intervention showed drastic reductions in NNI EDIs. Findings from the present study give credence to organic dietary interventions as potential ameliorative strategies for NNI exposure rates in human populations.

A Critical Scoping Review of Pesticide Exposure Biomonitoring Studies in Overhead Cultures

The exposure of operators, workers, residents and bystanders to pesticides is of high potential concern. Yet, reports on pesticide residues in the environment and near treated fields often spark debates if such findings might indicate a health risk. Although the underlying models are considered conservative, there are only limited field data on systemic exposure available. As a first step to improve the situation, we conducted a scoping review of state-of-the-art pesticide exposure biomonitoring studies in operators, workers, residents or bystanders. In contrast to existing reviews, we focused on target cultures of potential high pesticide exposure such as tree-grown produce, vine or hops. The search was conducted in Web of Science, Scopus and PubMed. Out of 17 eligible articles, a total of 11 studies met our search criteria, and 6 of them quantified the systemic exposure of humans. The analysis revealed that exposure was mainly driven by application of pesticides and reentry work, resulting in a higher exposure of operators and workers than of residents and bystanders. In nearly all cases, the systemic exposure was below the relevant toxicological reference values. The studies were subsequently analyzed to identify key criteria for a reliable design of a biomonitoring study on pesticide exposure.

Translocation and metabolism of the chiral neonicotinoid cycloxaprid in oilseed rape (Brassica napus L.)

Neonicotinoids have been banned in some countries because of increased nontarget resistance and ecological toxicity. Cycloxaprid is a potentially promising substitute, but its metabolism in plants is still poorly understood. The study aims to clarify the translocation of cycloxaprid, identify its metabolites, propose possible metabolic pathways and compare differences between enantiomers in oilseed rape via ¹⁴C tracing technology and HPLC-QTOF-MS. The results showed that most cycloxaprid remained in the treated leaves, and only a small amount translocated to the anthers. Seven metabolites were identified, and the possible metabolic pathway was divided into two phases. Phase Ⅰ metabolism included two metabolites obtained via cleavage of the oxa-bridged seven-membered ring. Phase II metabolism was responsible for glucose conjugate formation. The possible metabolic pathways revealed that the proportion of phase I metabolites gradually decreased over time, and the phase II metabolites transformed from monosaccharide and disaccharide conjugates to trisaccharide and tetrasaccharide conjugates. The levels of metabolites were significantly different between the enantiomers. In particular, the main metabolite was M4, which has confirmed biological toxicity. M2 was the only metabolite detected in rapeseed. The results will promote the scientific application of cycloxaprid in agriculture and could have implications for assessing environmental risk.

Synergistic effect of ZnO NPs and imidacloprid on liver injury in male ICR mice: Increase the bioavailability of IMI by targeting the gut microbiota

Although many toxicological studies on pesticides and nanoparticles have been conducted, it is not clear whether nanoparticles will increase the toxicity of pesticides. In this study, we chose imidacloprid (IMI) as a representative pesticide, and explored the influence of ZnO NPs on the toxic effect of IMI. In addition, we studied the bioaccumulation of IMI in mice. Using biochemical index analysis, liver histopathological analysis, non-targeted metabolomics, and LC/MS analysis, we found that ZnO NPs increased the toxicity of IMI, which may be related to the increase in IMI bioaccumulation in mice. In addition, we used intestinal histopathological analysis, RT-qPCR, and 16sRNA sequencing to find that the disturbance of the gut microbiota and the impaired intestinal barrier caused by ZnO NPs may be the reason for the increase in IMI bioaccumulation. In summary, our results indicate that ZnO NPs disrupted the intestinal barrier and enhanced the bioaccumulation of IMI, and therefore increased the toxicity of IMI in mice. Our research has deepened the toxicological insights between nanomaterials and pesticides.

Associations of neonicotinoids with insulin and glucose homeostasis parameters in US adults: NHANES 2015-2016

Neonicotinoids are replacement insecticides increasingly used for organophosphates, methylcarbamates, and pyrethroids. Experimental evidence suggests neonicotinoids may affect glucose metabolism and insulin secretion through pancreatic β cell dysfunction, oxidative stress, and inflammation. However, no epidemiologic study has investigated neonicotinoids as potential diabetogens. We examined associations between neonicotinoids with insulin and glucose homeostasis parameters among 1381 non-diabetic adults in the National Health and Nutrition Examination Survey (2015-2016). Urinary concentrations of acetamiprid, clothianidin, imidacloprid, N-desmethyl-acetamiprid, and 5-hydroxy-imidacloprid were quantified. Fasting plasma glucose, insulin, and hemoglobin A_1c (HbA_1c) were assessed. Insulin resistance was defined as a homeostatic model assessment of insulin resistance ≥2.5. We used weighted linear and logistic regression to estimate associations between detectable neonicotinoids with insulin and glucose homeostasis parameters compared to non-detectable neonicotinoid concentrations. Weighted detection frequencies for imidacloprid, 5-hydroxy-imidacloprid, and N-desmethyl-acetamiprid were 4.4 %, 21.5 %, and 32.8 %, respectively. Detectable imidacloprid (β = -4.7 μIU/mL, 95 % confidence interval [CI] -8.5, -0.8) and 5-hydroxy-imidacloprid (β = -2.4 μIU/mL, 95 % CI -4.6, -0.2) were associated with lower fasting plasma insulin levels. Individuals with detectable 5-hydroxy-imidacloprid had lower odds of insulin resistance (odds ratio [OR] = 0.3, 95 % CI 0.2, 0.7). We observed evidence of sexually dimorphic associations between N-desmethyl-acetamiprid with glucose (p_int = 0.079) and 5-hydroxy-imidacloprid with HbA_1c (p_int = 0.038), with patterns suggesting positive associations in males and negative associations in females. Associations between 5-hydroxy-imidacloprid and insulin were modified by body mass index (BMI) (p_int = 0.013). We additionally observed age modified associations between 5-hydyroxy-imidacloprid and glucose (p_int = 0.048). Results suggest neonicotinoids may be associated with insulin and glucose homeostasis indices and call for prospective studies to examine the metabolic impact of these replacement insecticides in humans.

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

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

Effects of imidacloprid on viability and increase of reactive oxygen and nitrogen species in HepG2 cell line

Imidacloprid (IMD) is a neonicotinoid insecticide used in large quantities worldwide in both veterinary and agronomic applications. Several studies have shown adverse effects of IMD on non-target organisms, with the liver being identified as the main affected organ. This study aimed to evaluate the effects of IMD on human hepatoblastoma (HepG2) cells. HepG2 were exposed to IMD (0.25-2.0 mM) for 24 and 48 h. IMD treatment resulted in cytotoxicity in the HepG2, inhibiting cell proliferation in a dose- and time-dependent manner, starting at concentrations of 0.5 mM (24 h) and 0.25 mM (48 h), and reducing cell viability from 0.5 mM onwards (24 and 48 h). IMD significantly decreased the mitochondrial membrane potential at both time points investigated (2.0 mM), and also induced damage to the cell membrane, demonstrated by significant dose and time-dependent increases in lactate dehydrogenase (LDH) release from concentrations of 1.0 mM (24 h) and 0.5 mM (48 h) upwards. IMD treatment also increased the production of reactive oxygen and nitrogen species (ROS/RNS) at rates above 50% following 0.5 mM (24 h) or 0.25 mM (48 h) concentrations, and caused a significant decrease in reduced/oxidized glutathione ratio (GSH/GSSG), indicating oxidative stress. Furthermore, the antioxidant dithiothreitol, which reacts with ROS/RNS and acts as a thiol reducing agent, inhibited the cytotoxic effect of IMD. In addition, the metabolite IMD-olefin was more toxic than IMD. Our results indicate that IMD induces cytotoxicity in HepG2 cells and that this effect may be associated with an increase in the generation of ROS/RNS.

Simultaneous quantification of imidacloprid and its metabolites in tissues of mice upon chronic low-dose administration of imidacloprid

This study aimed to (i) develop a sensitive method for simultaneous detection and quantification of imidacloprid (IMI) and seven of its metabolites in tissue specimens, and to (ii) determine the biodistribution of the IMI compounds in tissues of C57BL/6J male mice; after exposure to 0.6 mg/kg bw/day of IMI (10% of no observable adverse effect level of IMI) through a powdered diet for 24 weeks. We successfully developed a method which was accurate (recoveries were ≥ 70% for most compounds), sensitive (LODs ≤ 0.47 ng/mL and LOQs ≤ 1.43 ng/mL were recorded for all detected compounds, R2 ≥ 0.99) and precise (RSDs ≤ 20%) for routine analysis of IMI and seven of its metabolites in blood and various tissue matrices. After bio-distributional analysis, IMI and five of its metabolites were detected in mice. Brain, testis, lung, kidney, inguinal white adipose tissue and gonadal white adipose tissue mainly accumulated IMI, blood and mesenteric white adipose tissue mainly accumulated IMI-olefin; liver mainly accumulated desnitro-IMI; pancreas predominately accumulated 4-hydroxy-IMI. The desnitro-dehydro-IMI and the desnitro-IMI metabolites recorded tissue-blood concentration ratios ≥ 1.0 for testis, brain, lung and kidney. The cumulative levels of the six detected IMI compounds (Σ6 IMI compounds) were found in the decreasing order: blood > testis > brain > kidney > lung > iWAT > gWAT > mWAT > liver > pancreas. Altogether, this study provided essential data needed for effective mechanistic elucidation of compound-specific adverse outcomes associated with chronic exposures to IMI in mammalian species.

Neurotoxic Effects of Neonicotinoids on Mammals: What Is There beyond the Activation of Nicotinic Acetylcholine Receptors?-A Systematic Review

Neonicotinoids are a class of insecticides that exert their effect through a specific action on neuronal nicotinic acetylcholine receptors (nAChRs). The success of these insecticides is due to this mechanism of action, since they act as potent agonists of insect nAChRs, presenting low affinity for vertebrate nAChRs, which reduces potential toxic risk and increases safety for non-target species. However, although neonicotinoids are considered safe, their presence in the environment could increase the risk of exposure and toxicity. On the other hand, although neonicotinoids have low affinity for mammalian nAChRs, the large quantity, variety, and ubiquity of these receptors, combined with its diversity of functions, raises the question of what effects these insecticides can produce in non-target species. In the present systematic review, we investigate the available evidence on the biochemical and behavioral effects of neonicotinoids on the mammalian nervous system. In general, exposure to neonicotinoids at an early age alters the correct neuronal development, with decreases in neurogenesis and alterations in migration, and induces neuroinflammation. In adulthood, neonicotinoids induce neurobehavioral toxicity, these effects being associated with their modulating action on nAChRs, with consequent neurochemical alterations. These alterations include decreased expression of nAChRs, modifications in acetylcholinesterase activity, and significant changes in the function of the nigrostriatal dopaminergic system. All these effects can lead to the activation of a series of intracellular signaling pathways that generate oxidative stress, neuroinflammation and, finally, neuronal death. Neonicotinoid-induced changes in nAChR function could be responsible for most of the effects observed in the different studies.

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.

Insights into the degradation and toxicity difference mechanism of neonicotinoid pesticides in honeybees by mass spectrometry imaging

Honeybees are essential for the pollination of a wide variety of crops and flowering plants, whereas they are confronting decline around the world due to the overuse of pesticides, especially neonicotinoids. The mechanism behind the negative impacts of neonicotinoids on honeybees has attracted considerable interest, yet it remains unknown due to the limited insights into the spatiotemporal distribution of pesticides in honeybees. Herein, we demonstrated the use of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) for the spatiotemporal visualization of neonicotinoids, such as N-nitroguanidine (dinotefuran) and N-cyanoamidine (acetamiprid) compounds, administered by oral application or direct contact, in the whole-body section of honeybees. The MSI results revealed that both dinotefuran and acetamiprid can quickly penetrate various biological barriers and distribute within the whole-body section of honeybees, but acetamiprid can be degraded much faster than dinotefuran. The degradation rate of acetamiprid is significantly decreased when piperonyl butoxide (PBO) is applied, whereas that of dinotefuran remains almost unchanged. These two factors might contribute to the fact that dinotefuran affords a higher toxicity to honeybees than acetamiprid. Moreover, the toxicity and degradation rate of acetamiprid can be affected by co-application with tebuconazole. Taken together, the results presented here indicate that the discrepant toxicity between dinotefuran and acetamiprid does not lie in the difference in their penetration of various biological barriers of honeybees, but in the degradation rate of neonicotinoid pesticides within honeybee tissues. Moreover, new perspectives are given to better understand the causes of the current decline in honeybee populations posed by insecticides, providing guidelines for the precise use of conventional agrochemicals and the rational design of novel pesticide candidates.

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.

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.

Determinants of non-dietary exposure to agricultural pesticides in populations living close to fields: A systematic review

BACKGROUND

There is growing evidence in the scientific literature that individuals living near fields are more exposed to agricultural pesticides than people living further away.

OBJECTIVE

The main objective of this systematic review was to identify the non-dietary determinants of pesticide exposure related to the drift pathway in residents living in agricultural areas, including spatial indictors related to agricultural activities, hygiene practices, behaviors and sociodemographic parameters.

METHODS

Three databases were consulted (PubMed, Web of sciences, Scopus). At least two experts selected the eligible studies.

RESULTS

A total of 27 original studies (2002-2020) fulfilled the eligibility criteria of this review. These publications explored pesticide exposure of individuals through measurements in biological samples (n = 13), environmental samples (n = 11) or both (n = 3). Spatial indicators, including residential proximity to fields, crop acreage around the residence and amounts of pesticides applied in the vicinity were identified as determinants of pesticide exposure in many studies (n = 17), including publications considered to be of very good or good quality (n = 12). Season of spraying tended to increase the levels of pesticides measured in five publications out of seven. Meteorological parameters and physical barriers showed an inconsistent and complex influence on the presence and levels of pesticides in urine samples and house dust. Frequent housekeeping reduced the presence of pesticides at home and consequently in biological matrices in three studies out of six. Finally, the effect of the occupants' sociodemographic characteristics, behaviors, and hygiene practices on the exposure measurement was less well documented and results were fairly inconsistent.

DISCUSSION AND CONCLUSION

This study consolidates our knowledge of the determinants influencing pesticide exposure levels in people living in agricultural areas. Nevertheless, the available scientific data is still too limited to serve as a basis for developing risk management measures. More research is needed to improve knowledge of the determinants of exposure.

Characterizing imidacloprid and metabolites in songbird blood with applications for diagnosing field exposures

Neonicotinoids are the most widely used insecticides globally, but their rapid metabolism in vertebrates makes diagnosing wildlife exposure challenging. More detailed information on the pattern of imidacloprid metabolites over time could be used to better approximate the timing and level of exposure. Here, we applied recently developed sensitive analytical methods to measure imidacloprid (IMI) parent compound along with an expanded suite of metabolites (5-OH-IMI, IMI-olefin, desnitro-IMI, IMI-urea, 6-chloronicotinic acid, 5-AMCP, 6-OH nicotinic acid) and six other neonicotinoids in adult red-winged blackbirds (Agelaius phoeniceus) that were experimentally exposed to one of two field-realistic concentrations of imidacloprid (0.8 or 6.9 mg/kg bw). We measured concentrations in small (25 μL) plasma samples collected pre-exposure and at 1-, 6-, 24- and 48-h post-exposure. Imidacloprid was rapidly absorbed and metabolized within 48 h at both doses, with the largest decrease within 6 h post-exposure. The average proportion of parent IMI decreased from 68% of total detectable residues at 1-h to 34% at 6-h post-exposure. Two primary metabolites in blood were 5-OH-IMI and IMI-olefin, and 5-OH-IMI was the most persistent marker of exposure at 48-h. Desnitro-IMI was consistently detected following very recent (≤ 1-h) IMI exposure, and a higher ratio of parent IMI to metabolites also indicated recent exposure. Other metabolites were only detected in the higher dose group, and could be used as indicators of exposure to higher IMI concentrations. This sensitive analytical method and the observed metabolite patterns could be used to inform a growing body of field studies linking neonicotinoid exposure and effects in free-living birds.

Aging-related changes in the sensitivity of behavioral effects of the neonicotinoid pesticide clothianidin in male mice

Neonicotinoids, which act as agonists of the nicotinic acetylcholine receptors of insects, are widely used pesticides worldwide. Although epidemiological studies revealed that the detection amounts of neonicotinoids in urine are higher in the elderly population than other age-groups, there is no available information regarding the risks of neonicotinoids to older mammals. This study was aimed to investigate aging-related differences in the behavioral effects of the neonicotinoid pesticide clothianidin (CLO). We acutely administered a sub-NOAEL level (5 mg/kg) of CLO to adult (12-week-old) and aging (90-week-old) mice and conducted four behavioral tests focusing on the emotional behavior. In addition, we measured the concentrations of CLO and its metabolites in blood, brain and urine. There were age-related changes in most parameters in all behavioral tests, and CLO significantly decreased the locomotor activity in the open field test and elevated plus-maze test in the aging group, but not in the adult group. The concentrations of most CLO and its metabolites were significantly higher in the blood and brain and were slightly lower in the urine in the aging group compared to the adult group. These findings should contribute to our understanding of age-related differences in the adverse effects of neonicotinoids in mammals.

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.

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.

Evaluation of 1-year urinary excretion of eight metabolites of synthetic pyrethroids, chlorpyrifos, and neonicotinoids

Synthetic pyrethroids, chlorpyrifos, and neonicotinoids are representatives of non-persistent insecticides ubiquitously used against insects all over the world. Their widespread use causes prevalent exposure to these compounds, which may be hazardous to human health. The insecticides have short biological half-lives and are mostly excreted in urine within 24 h after entering the human body; thus, the urinary concentration of their metabolites is highly dependent on the time elapsed between exposure and sample collection. Considering the within-day fluctuations in urinary concentration, one randomly collected sample may cause misclassification of long-term exposure. We evaluated the variability of excretion of eight insecticide metabolites in 24-h urine samples collected from 14 volunteers once or twice per month over 12 consecutive months. High detection frequency above 70% for non-specific metabolites of pyrethroid, chlorpyrifos, and neonicotinoids confirmed widespread exposure to these insecticides in the studied population. A long-term variability of exposure was assessed based on intraclass correlation coefficient (ICC). We found relatively low variability of excretion for non-specific pyrethroid metabolites and 3,5,6-trichloro-2-pyridinol (ICC > 0.75), but poor repeatability for 6-chloronicotinic acid. Constantly higher ICCs were observed for daily excretion than for unadjusted concentrations. Seasonal differences were observed for 3,5,6-trichloro-2-pyridinol and 6-chloronicotinic acid, with the highest and the lowest median concentration, respectively, in the summer. Due to high ICC values and lack of seasonal variations, one 24-h urine sample was considered sufficient to characterize long-term excretion of non-specific pyrethroid metabolites in non-occupationally exposed population. In addition, we calculated the daily intake (DI) for cypermethrin, permethrin, deltamethrin, and chlorpyrifos. The estimated DI values were mostly below the acceptable daily intake, which indicates that the evaluated exposure is non-hazardous to the population.

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.

Functional and Pharmacological Comparison of Human, Mouse, and Rat Organic Cation Transporter 1 toward Drug and Pesticide Interaction

Extrapolation from animal to human data is not always possible, because several essential factors, such as expression level, localization, as well as the substrate selectivity and affinity of relevant transport proteins, can differ between species. In this study, we examined the interactions of drugs and pesticides with the clinically relevant organic cation transporter hOCT1 (SLC22A1) in comparison to the orthologous transporters from mouse and rat. We determined K_m-values (73 ± 7, 36 ± 13, and 57 ± 5 µM) of human, mouse and rat OCT1 for the commonly used substrate 1-methyl-4-phenylpyridinium (MPP) and IC₅₀-values of decynium22 (12.1 ± 0.8, 5.3 ± 0.4, and 10.5 ± 0.4 µM). For the first time, we demonstrated the interaction of the cationic fungicides imazalil, azoxystrobin, prochloraz, and propamocarb with human and rodent OCT1. Drugs such as ketoconazole, clonidine, and verapamil showed substantial inhibitory potential to human, mouse, and rat OCT1 activity. A correlation analysis of hOCT1 versus mouse and rat orthologs revealed a strong functional correlation between the three species. In conclusion, this approach shows that transporter interaction data are in many cases transferable between rodents and humans, but potential species differences for other drugs and pesticides could not be excluded, though it is recommendable to perform functional comparisons of human and rodent transporters for new molecular entities.

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.

Levels and inhalation health risk of neonicotinoid insecticides in fine particulate matter (PM2.5) in urban and rural areas of China

Neonicotinoid insecticide (NEO) concentrations in ambient fine particulate matter (PM_2.5) and daily exposure via inhalation were investigated during spring and fall in an urban area in Beijing and in urban and rural areas of Zhengzhou, Henan Province, China. Four NEOs, including imidacloprid, acetamiprid, thiamethoxam and clothianidin, were assessed using a QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction procedure coupled to liquid chromatography-tandem mass spectrometry. Of 64 PM_2.5 samples, 100% contained at least two NEOs (imidacloprid and acetamiprid). Imidacloprid was detected at the highest levels, ranging from 4.33 to 1.13 × 10² pg m^-3. A relative potency factor method that considered different toxicities was used to integrate the four NEO concentrations. The total NEO concentrations in air in the Zhengzhou rural area (mean: 80.86 pg m^-3) were higher than those in urban areas. Differences between seasons were not significant (p > 0.05). The highest value for the total average daily dose via inhalation of four NEOs (ADD_inh,total), 91.0 pg kg^-1 day^-1, was found in rural children <6 years old. The ADD_inh,total of rural residents was significantly higher than that of urban residents when there was no intensive pesticide application. Although the ADD_inh,total values were below the current chronic reference dose, when possible joint toxicity and the increasing use of NEOs are considered, a potential health risk via inhalation is evident. We believe this study is the first to characterize NEO levels in fine particulate matter and to evaluate inhalation exposure in urban and rural residents under nonoccupational scenarios in China. It will enhance our understanding of exposure to NEOs and provide a basis for risk management decisions.

Insights into the Toxicity and Degradation Mechanisms of Imidacloprid Via Physicochemical and Microbial Approaches

Imidacloprid is a neonicotinoid insecticide that has been widely used to control insect pests in agricultural fields for decades. It shows insecticidal activity mainly by blocking the normal conduction of the central nervous system in insects. However, in recent years, imidacloprid has been reported to be an emerging contaminant in all parts of the world, and has different toxic effects on a variety of non-target organisms, including human beings, due to its large-scale use. Hence, the removal of imidacloprid from the ecosystem has received widespread attention. Different remediation approaches have been studied to eliminate imidacloprid residues from the environment, such as oxidation, hydrolysis, adsorption, ultrasound, illumination, and biodegradation. In nature, microbial degradation is one of the most important processes controlling the fate of and transformation from imidacloprid use, and from an environmental point of view, it is the most promising means, as it is the most effective, least hazardous, and most environmentally friendly. To date, several imidacloprid-degrading microbes, including Bacillus, Pseudoxanthomonas, Mycobacterium, Rhizobium, Rhodococcus, and Stenotrophomonas, have been characterized for biodegradation. In addition, previous studies have found that many insects and microorganisms have developed resistance genes to and degradation enzymes of imidacloprid. Furthermore, the metabolites and degradation pathways of imidacloprid have been reported. However, reviews of the toxicity and degradation mechanisms of imidacloprid are rare. In this review, the toxicity and degradation mechanisms of imidacloprid are summarized in order to provide a theoretical and practical basis for the remediation of imidacloprid-contaminated environments.

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.

Development of immunoassays with high sensitivity for detecting imidacloprid in environment and agro-products using phage-borne peptides

Imidacloprid is the most widely used neonicotinoid insecticide and has been reported to pose a threat to ecological security and human health. Therefore, simple-to-operate and highly sensitive methods for the detection of trace levels of imidacloprid are necessary. Here, we isolated two phage-borne peptides that compete with imidacloprid to bind the monoclonal antibody (mAb) 3D11 from phage display peptide libraries. A phage-enzyme-linked immunosorbent assay (P-ELISA) and two phage time-resolved fluoroimmunoassays (P-TRFIAs) for the detection of imidacloprid were developed using the phage-borne peptides as substitutes for chemically synthesized antigens. After systematic optimization, the half-maximum inhibition concentrations (IC₅₀) of the P-ELISA, P-TRFIA-1, and P-TRFIA-2 were 0.067 ng mL^-1, 0.085 ng mL^-1, and 0.056 ng mL^-1, respectively. Based on their IC₅₀ values, the sensitivities of the P-ELISA and P-TRFIAs were more than four times greater than those of previous immunoassays. Additionally, the immunoassays showed satisfactory recovery in the detection of spiked samples and good correlation with high performance liquid chromatography (HPLC) for the detection of samples containing incurred residues.

Spatial and temporal distribution, degradation, and metabolism of three neonicotinoid insecticides on different parts, especially pests' target feeding parts of apple tree

BACKGROUND

Neonicotinoid insecticides (NIs) have been recently banned in some countries because of increased pest resistance and deleterious risks to non-target organisms. Recent studies considered all parts of crops as a whole part in plant protection. However, there are few reports focused on the distribution and metabolic trends of NIs on target feeding sites of different pests in apple orchards.

RESULTS

The spatial and temporal distribution, absorption, degradation, and metabolism of three NIs, imidacloprid, acetamiprid, and thiamethoxam, on different parts of apple trees were studied under foliar spray and root irrigation treatments. In the spray treatment, the initial average concentration ratios (TCRs) were 31.6% for lower shoots, 23.3% for upper leaves, 23.2% for upper shoots, 21.0% for lower leaves, and 0.5% and 0.4% for upper and lower fruits, respectively. The average half-lives of the three NIs were 2.9 days for shoots, 7.4 days for leaves, and 10.8 days for fruits. The degradation rate of shoots was 2.5 times that of leaves, and 3.6 times that of fruits. Imidacloprid olefin and N-methyl acetamiprid were two of the main metabolites. In the root treatment, both roots and soils had high TCRs during the whole sampling period. Only imidacloprid was transmitted to above-ground parts of the plants, with TCRs of 0.38-50.94%.

CONCLUSION

This study found significant differences in spatial and temporal distribution, degradation, metabolism, and trends of NIs on different pest target sites of apple trees. The data obtained may help promote scientific control of target pests and evaluation of safety for non-target species in orchards. © 2020 Society of Chemical Industry.