Quantitative analysis of neonicotinoid insecticide residues in foods: implication for dietary exposures

A comprehensive analysis of the composition, health benefits, and safety of apple pomace

Apple processing results in peel, stem, seeds, and pulp being left as a waste product known as apple pomace. This review comprehensively assessed apple pomace composition for nutritional value and bioactive substances and evaluated potential health benefits and safety. Apple pomace is a rich source of health-benefitting nutrients, including minerals, dietary fiber, antioxidants, and ursolic acid, which suggests it has potential use as a dietary supplement, functional food, and/or food additive. Preclinical studies have found apple pomace and its isolated extracts improved lipid metabolism, antioxidant status, and gastrointestinal function and had a positive effect on metabolic disorders (eg, hyperglycemia, insulin resistance, etc.). Safety studies have shown apple pomace to be a safe livestock feed additive and to have pesticide concentrations within safety thresholds established for human consumption. Commercial development of apple pomace for human consumption requires more research focusing on standardized methods of nutrient reporting, mechanistic studies, and human clinical trials.

Quantification of DEET and neonicotinoid pesticide biomarkers in human urine by online solid-phase extraction high-performance liquid chromatography-tandem mass spectrometry

Neonicotinoid insecticides are widely used replacements for organophosphate and carbamate insecticides, but the extent of human exposure is largely unknown. On the other hand, based on urinary concentrations of DEET metabolites, human exposure to N,N-diethyl-m-toluamide (DEET) appears to be widespread. We developed a fast online solid-phase extraction high-performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in 200 μL of human urine the concentrations of six neonicotinoid biomarkers (acetamiprid, N-desmethyl-acetamiprid, clothianidin, imidacloprid, 5-hydroxy-imidacloprid, thiacloprid), and two DEET biomarkers (3-diethyl-carbamoyl benzoic acid, 3-ethyl-carbamoyl benzoic acid). Limits of detection ranged from 0.01 to 0.1 μg/L, depending on the biomarker. Accuracy ranged from 91 to 116% and precision ranged from 3.7 to 10 %RSD. The presented method can be used to increase our understanding of exposure to neonicotinoid insecticides and DEET, and to evaluate the potential health effects from such exposures.

Mammalian Susceptibility to a Neonicotinoid Insecticide after Fetal and Early Postnatal Exposure

Neonicotinoids have become the most widely used class of insecticides world-wide. Although numerous studies have documented neonicotinoid toxicity in bees and other insects, the effects of exposure during early development in mammals remain largely unexplored. We assessed the effects of the neonicotinoid imidacloprid (IMI) in adult male and female mice after in utero and early postnatal exposure. Pregnant mice were infused with IMI (0.5 mg/kg/day) from gestational day 4 to the end of nursing at postnatal day 21. The young adult offspring were studied in a series of biochemical and behavioral tests. To assess reproducibility, the behavioral analyses were conducted in three separate studies using multiple exposed litters. Exposure to IMI reduced fecundity, and in adult offspring, decreased body weight in male but not female pups. Offspring from IMI-treated mothers displayed lower triglycerides, elevated motor activity, enhanced social dominance, reduced depressive-like behavior, and a diminution in social aggression compared to vehicle treated controls. Low levels of IMI were detected in the brains and livers of the treated mothers, while trace levels were detected in some offspring. Our results demonstrate that transient exposure to a neonicotinoid over the early developmental period induces long-lasting changes in behavior and brain function in mice.

Identification and characterization of matrix components in spinach during QuEChERS sample preparation for pesticide residue analysis by LC-ESI-MS/MS, GC-MS and UPLC-DAD

In this article matrix components in spinach were investigated in detail. The samples were prepared using two QuEChERS (quick, easy, cheap, effective, rugged and safe) methods, AOAC and CEN. Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), gas chromatography-mass spectrometry (GC-MS) and ultra performance liquid chromatography-diode array detector (UPLC-DAD), were applied for component identification. The strategies of identification by LC-ESI-MS/MS include accurate mass spectra of the parent ion, comparison with previous literature data and investigation of the mass spectral decomposition pattern. Overall, fourteen components were identified by LC-ESI-MS/MS in each methods of AOAC and CEN, which were phytosteroids, flavonoids, fatty acids and fatty acid amides. Fifty components using AOAC method and fifty-seven components using CEN method were identified in GC-MS by comparing mass data with the National Institute of Standards and Technology (NIST, U.S.) database. The results indicate that the major components of the matrix are terpenoids, fatty acids and fatty acid esters. Moreover, three pigments (neoxanthin, violaxanthin and lutein) in the AOAC method and eight pigments (neoxanthin, violaxanthin, zeaxanthin, lutein, chlorophyll a, chlorophyll b, pheophytin a and beta-carotene) in the CEN method that gave a characteristics peak at 440 nm were identified by the UPLC-DAD. According to the sample preparation condition using different amounts of graphitized carbon black (GCB) in this study, the AOAC method had higher matrix component removal efficiency than the CEN method. A better understanding of matrix components would increase the current knowledge for improvement of existing QuEChERS methodology, as well as contribute to new method developments.

Characterization of Daily Dietary Intake and the Health Risk of Neonicotinoid Insecticides for the U.S. Population

Although neonicotinoids have been the most commonly used insecticides globally, very limited data related to their dietary intake and health risks are available. In this study, we used the relative potency factor approach to aggregate individual neonicotinoids into a single metric (IMI_RPF) representing the intakes of total neonicotinoids in relation to imidacloprid for each food item. We then estimated the average daily intake (ADI) of neonicotinoids using residue data collected from U.S. Congressional Cafeteria study (USCC) and USDA/PDP and food consumption data from NHANES 2011-2012. Among the USCC and USDA/PDP samples, squash (427.2 ng/g) and spinach (569.2 ng/g), had the highest average IMI_RPF, respectively. The estimated ADIs were below the current chronic reference dose (cRfD) for imidacloprid. However, due to their wide use, it is logical to expect the ubiquity of neonicotinoids in foods. Therefore, the importance of conducting routine dietary intake assessment for neonicotinoids should not be ignored.

Simultaneous determination of nine neonicotinoids in human urine using isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry

Neonicotinoids (neonics), a class of systemic insecticides, have been frequently detected in pollen, vegetables, and fruits. Recently, an increasing concern has been aroused for human exposure to neonics. However, biological monitoring for quantifying body burden of neonics has rarely been reported. In this study, we developed an isotope-dilution ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method to simultaneously quantify nine neonics, including acetamiprid (ACE), thiamethoxam (THIAM), imidacloprid (IMIP), clothianidin (CLO), flonicamid (FLO), thiacloprid (THIAC), dinotefuran (DIN), nitenpyram (NIT), and imidaclothiz (IMIT) in urine. The limits of quantification were 0.1 μg/L for ACE, FLO, DIN, NIT and IMIT, and 0.2 μg/L for THIAM, IMIP, CLO, and THIAC. The overall recoveries were 80.8-103%, 81.5-91.7% and 83.0-92.3% for QA/QC samples fortifying at 1, 25, and 100 μg/L levels, respectively. UPLC/MS/MS method was used to analyze urine samples obtained from 10 children in Hangzhou, China. The detection frequencies were 80% for ACE and IMIP, 70% for THIAM and CLO, 20% for DIN and IMIT and 10% for THIAC. FLO and NIT were not detected in those urine samples. The data provided here will be helpful for conducting biological monitoring of neonics exposure in the future.

Effect of imidacloprid ingestion on immune responses to porcine reproductive and respiratory syndrome virus

Nicotine and acetylcholine cause immunosuppresion by signaling to the α7 nicotinic acetylcholine receptor (α7 nAChR) on immune cells. Neonicotinoids are nAChR agonists and widly used insecticides. We aimed to define the immunosuppressive potential of dietary exposure to the neonicotinoid imidacloprid (IMI) on the generation of innate and adaptive immune responses to porcine reproductive and respiratory syndrome virus (PRRSV). Piglets were randomized into groups based on diet and infection. Behavioral signs of illness were recorded. Urine IMI levels were measured by high performance liquid chromatography-mass spectrometry. Flow cytometry was used to determine the expression pattern of the α7 nAChR on porcine leukocytes as well as the effects of infection and treatment on circulating leukocyte populations. Serum cytokines and PRRSV-specific antibody levels were determined by ELISA. Viral RNA in lung, spleen and plasma was determined by RT-qPCR. Pigs in the treatment group had elevated urine levels of IMI. Treatment with IMI reduced body weight, caused bouts of hypothermia, increased serum IL-10 and elevated levels of virus-specific antibodies. Viral RNA levels in the spleen showed a trend toward being increased in pigs fed IMI. Our data indicates that IMI injection may modulate virus specific immune function during PRRSV infection.

rGO-NS SERS-based coupled chemometric prediction of acetamiprid residue in green tea

Pesticide residue in food is of grave concern in recent years. In this paper, a rapid, sensitive, SERS (Surface-enhanced Raman scattering) active reduced-graphene-oxide-gold-nano-star (rGO-NS) nano-composite nanosensor was developed for the detection of acetamiprid (AC) residue in green tea. Different concentrations of AC combined with rGO-NS nano-composite electro-statically, yielded a strong SERS signal linearly with increasing concentration of AC ranging from 1.0 × 10⁻⁴ to 1.0 × 10³ μg/mL indicating the potential of rGO-NS nanocomposite to detect AC in green tea. Genetic algorithm-partial least squares regression (GA-PLS) algorithm was used to develop a quantitative model for AC residue prediction. The GA-PLS model achieved a correlation coefficient (Rc) of 0.9772 and recovery of the real sample of 97.06%–115.88% and RSD of 5.98% using the developed method. The overall results demonstrated that Raman spectroscopy combined with SERS active rGO-NS nanocomposite could be utilized to determine AC residue in green tea to achieve quality and safety.

Teratogenic effects of the neonicotinoid thiacloprid on chick embryos (Gallus gallus domesticus)

Thiacloprid is an insecticide belonging to the family of neonicotinoids, substances initially underestimated for their potential adverse effects, that they may manifest in the long term leading to an extensive use. The objective of this study was to evaluate the effect at increasing concentrations of thiacloprid on chick embryos development. The research was carried out on 75 fertile eggs of Gallus gallus domesticus. The eggs were opened after 10, 15 and 20 days of incubation and in treated embryos were observed developmental alterations, growth retardation, limbs defects and ectopia viscerale. The histological analysis showed hepatic steatosis and haemorrhages both in the liver and in the lungs. Moreover, the immunohistochemical analysis performed on the liver sections showed a strong positivity only for the erythrocytes to the anti-CYP1A antibody. Thiacloprid exposure increases the risks of teratogenic effects especially at the higher doses tested, therefore its use should be more controlled and limited. Since the literature on the topic is lacking, then the human health impacts resulting from neonicotinoids exposure is not yet fully understood, and, our data will be helpful to allow the assessment of an oral reference dose and health risk characterization.

Simultaneous determination of neonicotinoid insecticides and insect growth regulators residues in honey using LC-MS/MS with anion exchanger-disposable pipette extraction

In this study, we developed an anion exchanger-disposable pipette extraction (DPX) method to detect the residual concentrations of eight neonicotinoid insecticides (dinotefuran, acetamiprid, clothianidin, thiacloprid, imidachloprid, imidaclothiz, nitenpyram, and thiamethoxam) and eight insect growth regulators (IGRs; triflumuron, cyromazine, buprofezin, methoxyfenozide, tebufenozide, chromafenozide, fenoxycarb, and RH 5849) in Chinese honey samples collected from different floral sources and different geographical regions using liquid chromatography tandem mass spectrometry (LC-MS/MS). QAE Sephadex A-25 was used as the anion exchanger in the DPX column for the purification and cleanup of honey samples. Analytes were eluted with a mixture of acetonitrile and 0.1 M HCl, and the elution was subjected to LC analysis. This method was thoroughly validated for its reproducibility, linearity, trueness, and recovery. Satisfactory recovery of pesticides was obtained ranging from 72% to 111% with intraday RSDs (n = 5) of 1%-10%. High linearity (R² ≥ 0.9987) was observed for all 16 pesticides. Limits of detection and quantification for all 16 compounds ranged from 0.3 to 3 μg/kg and from 1 to 10 μg/kg, respectively. Pesticide residues (9-113 μg/kg) were found in Chinese honey samples. The anion exchanger-DPX method was effective for removing sugars and retaining target analytes. Moreover, this method was highly reliable and sensitive for detecting neonicotinoids and IGRs in different floral sources of honey and will be applicable to matrixes with high sugar content.

Potential human exposures to neonicotinoid insecticides: A review

Due to their systemic character and high efficacy to insect controls, neonicotinoid insecticides (neonics) have been widely used in global agriculture since its introduction in early 1990. Recent studies have indicated that neonics may be ubiquitous, have longer biological half-lives in the environment once applied, and therefore implicitly suggested the increasing probability for human exposure to neonics. Despite of neonics' persistent characters and widespread uses, scientific literature in regard of pathways in which human exposure could occur is relatively meager. In this review, we summarized results from peer-reviewed articles published prior to 2017 that address potential human exposures through ingestion and inhalation, as well as results from human biomonitoring studies. In addition, we proposed the use of relative potency factor approach in order to facilitate the assessment of concurrent exposure to a mixture of neonics with similar chemical structures and toxicological endpoints. We believe that the scientific information that we presented in this review will aid to future assessment of total neonic exposure and subsequently human health risk characterization.

Effects of Neonicotinoid Pesticides on Promoter-Specific Aromatase (CYP19) Expression in Hs578t Breast Cancer Cells and the Role of the VEGF Pathway

BACKGROUND

Aromatase (CYP19) is a key enzyme in estrogens biosynthesis. In the mammary gland, CYP19 gene is expressed at low levels under the regulation of its I.4 promoter. In hormone-dependent breast cancer, fibroblast cells surrounding the tumor express increased levels of CYP19 mRNA due to a decrease of I.4 promoter activity and an increase of PII, I.3, and I.7 promoter activity. Little is known about the effects of environmental chemicals on the promoter-specific CYP19 expression.

OBJECTIVE

We aimed to determine the effects of two neonicotinoids (thiacloprid and imidacloprid) on promoter-specific CYP19 expression in Hs578t breast cancer cells and understand the signaling pathways involved.

METHODS

Hs578t cells were exposed to various signaling pathway stimulants or neonicotinoids for 24 h. Promoter-specific expression of CYP19 was determined by real-time quantitative polymerase chain reaction and catalytic activity of aromatase by tritiated water release assay.

RESULTS

To our knowledge, we are the first to demonstrate that the normal I.4 promoter and the breast cancer-relevant PII, I.3, and I.7 promoters of CYP19 are active in these cells. We found that the expression of CYP19 via promoters PII, I.3, and I.7 in Hs578t cells was, in part, dependent on the activation of two VEGF signaling pathways: mitogen-activated protein kinase (MAPK) 1/3 and phospholipase C (PLC). Exposure of Hs578t cells to environmental concentrations of imidacloprid and thiacloprid resulted in a switch in CYP19 promoter usage, involving inhibition of I.4 promoter activity and an increase of PII, I.3, and I.7 promoter-mediated CYP19 expression and aromatase catalytic activity. Greater effects were seen at lower concentrations. Our results suggest that thiacloprid and imidacloprid exert their effects at least partially by inducing the MAPK 1/3 and/or PLC pathways.

CONCLUSIONS

We demonstrated in vitro that neonicotinoids may stimulate a change in CYP19 promoter usage similar to that observed in patients with hormone-dependent breast cancer. https://doi.org/10.1289/EHP2698.

Determination of thiamethoxam residues in banana stem and fruit through LC-MS/MS

An analytical method based on liquid chromatography coupled with mass spectroscopy/mass spectroscopy was developed and validated for the determination of thiamethoxam residues in banana fruit and stem tissue samples. In this study, Waters Alliance LC and Acquity TQD were used with an electrospray ionization interface in the positive ion mode. An isocratic flow of 0.5% HCOOH in water and 0.05% HCOOH in CH₃CN was used for separation. Thiamethoxam residue was extracted from the samples using CH₃CN and a dispersive solid-phase extraction method was used for subsequent cleanup. Linearity studies were conducted between 0.001 and 0.1 μg mL^-1 of standard solution with three replicates for each concentration. Satisfactory recoveries (107.21 to 115.16% and 90.94 to 109.22%) and high precision (relative standard deviations of 3.71 to 12.83% and 3.24 to 10.78%) were obtained for the banana stem and banana fruit matrix, respectively. The lower limits of detection and quantification achieved were 0.002 and 0.008 μg g^-1 for banana stem and 0.001and 0.005 μg g^-1for banana fruit, respectively. The developed method was used to analyze the banana stem and fruit samples collected from thiamethoxam-treated fields and stems from the local market.

Neonicotinoid Residues in Fruits and Vegetables: An Integrated Dietary Exposure Assessment Approach

Neonicotinoids have become the most widely used insecticides in the world since introduced in the mid 1990s, yet the extent of human exposure and health impacts is not fully understood. In this study, the residues were analyzed of seven neonicotinoids in fruit and vegetable samples collected from two cross-sectional studies: the U.S. Congressional Cafeteria study (USCC) and the Hangzhou China (HZC) study. We then employed a relative potency factor method to integrate all neonicotinoids in each food sample using the respective reference dose values as the basis for summation. The findings were compared with data published by the U.S. Department of Agriculture Pesticide Data Program (USDA/PDP). Imidacloprid and thiamethoxam were the most commonly detected neonicotinoids in fruits and vegetables with 66 and 51% detection in the HZC study and 52 and 53% detection in the USCC study, respectively. The overall frequency of detection for neonicotinoids in the USDA/PDP samples was much lower than those reported here for the USCC or HZC studies, with imidacloprid being the most frequently detected neonicotinoid at 7.3%. The high frequencies of neonicotinoid detection in fruits and vegetables in the USCC and HZC studies give us a snapshot of the ubiquity of neonicotinoid use in global agriculture and make it clear that neonicotinoids have become part of the dietary staple, with possible health implications for individuals.

Photochemistry of Solid Films of the Neonicotinoid Nitenpyram

The environmental fates of nitenpyram (NPM), a widely used neonicotinoid insecticide, are not well-known. A thin solid film of NPM deposited on a germanium attenuated total reflectance (ATR) crystal was exposed to radiation from a low-pressure mercury lamp at 254 nm, or from broadband low pressure mercury photolysis lamps centered at 350 or 313 nm. The loss during photolysis was followed in time using FTIR. The photolysis quantum yields (ϕ), defined as the number of NPM molecules lost per photon absorbed, were determined to be (9.4 ± 1.5) × 10^-4 at 350 nm, (1.0 ± 0.3) × 10^-3 at 313 nm, and (1.2 ± 0.4) × 10^-2 at 254 nm (±2σ). Imines, one with a carbonyl group, were detected as surface-bound products and gaseous N₂O was generated in low (11%) yield. The UV-vis absorption spectra of NPM in water was different from that in acetonitrile, dichloromethane, and methanol, or in a thin solid film. The photolytic lifetime of solid NPM at a solar zenith angle at 35° is calculated to be 36 min, while that for NPM in water is 269 min, assuming that the quantum yield is the same as in the solid. Thus, there may be a significant sensitivity to the medium for photolytic degradation and the lifetime of NPM in the environment.

Exposure to neonicotinoid insecticides induces embryotoxicity in mice and rabbits

The potential toxicity of neonicotinoids (thiacloprid, acetamiprid, thiamethoxam and clothianidin) as well as related commercial products Calypso 480SC (thiacloprid mixture), Mospilan 20SP (acetamiprid mixture) and Agita 10WG (thiamethoxam mixture) on developmental capacities and quality of preimplantation embryos was evaluated. During in vitro tests, isolated 2-cell stage mice embryos were cultured in media with various concentrations of active compounds or commercial products until blastocyst formation. As found using stereomicroscopic examination, all neonicotinoids at highest (100μM) concentration negatively affected embryonic development (P<0.001). Fluorescence staining revealed that the blastocysts obtained displayed lower numbers of blastomeres and elevated incidence of cell death. Thiacloprid and acetamiprid decreased quality of blastocysts also at 10μM concentration. From the tested products only Calypso 480SC containing 10μM of thiacloprid showed harmful impact on embryo quality. In an experiment using rabbit embryos, similar negative effect of thiacloprid in vitro was recorded. In vivo testing confirmed that blastocysts collected from thiacloprid-treated mice displayed lower total cell counts than blastocysts from controls. The sensitivity of embryonic cells to neonicotinoids is in the order of thiacloprid>acetamiprid, thiomethoxam>clothianidin. Thiacloprid impairs development and quality of both mouse and rabbit preimplantation embryos, and shows embryotoxicity even at acute reference dose.

Protective effect of Nigella sativa oil against acetamiprid induced reproductive toxicity in male rats

The present study was designed to investigate the adverse reproductive effects of acetamiprid, besides the possible protective role of Nigella sativa oil (NSO), as a potential antioxidant agent. Thirty-two male Wistar rats were allocated into four equal groups of eight, control (CRL), acetamiprid (ACMP, 27 mg/kg), Nigella sativa oil (NSO, 0.5 ml/kg) and in combination (ACMP + NSO). The experimental animals were dosed by gavage (5 days per week) for 45 consecutive days. Body weight gain, reproductive organs weights, sperm characteristics, testosterone, and thiobarbutiric acid-reactive substances (TBARS) levels were investigated. The obtained results showed that ACMP decreased significantly (p < 0.001) the body weight gain and the absolute weights of reproductive organs (testes, epididymis, and seminal vesicles). Furthermore, significant alterations at least (p < 0.01) in semen characteristics were noted in ACMP group as evidenced by a decline in spermatids number, sperm count, sperm motility, and testosterone level with an increase in abnormal and dead sperm and TBARS level. Treatment with NSO alone may stimulate spermatogenesis, increased significantly (p < 0.001) spermatids number and the weight of seminal vesicles. On the other hand, the co-administration of NSO along with ACMP can mitigate more efficiently and modulate in certain cases the adverse effects induced by ACMP on reproductive organs weights, semen quality, testosterone, and TBARS levels (at least p < 0.001). This obvious protective role of NSO against ACMP induced reproductive toxicity may be due to its antioxidant properties and ability to reduce TBARS levels as shown in this work.

Developmental neurotoxicity of succeeding generations of insecticides

Insecticides are by design toxic. They must be toxic to effectively kill target species of insects. Unfortunately, they also have off-target toxic effects that can harm other species, including humans. Developmental neurotoxicity is one of the most prominent off-target toxic risks of insecticides. Over the past seven decades several classes of insecticides have been developed, each with their own mechanisms of effect and toxic side effects. This review covers the developmental neurotoxicity of the succeeding generations of insecticides including organochlorines, organophosphates, pyrethroids, carbamates and neonicotinoids. The goal of new insecticide development is to more effectively kill target species with fewer toxic side effects on non-target species. From the experience with the developmental neurotoxicity caused by the generations of insecticides developed in the past advice is offered how to proceed with future insecticide development to decrease neurotoxic risk.

Effects of Neonicotinoid Pesticide Exposure on Human Health: A Systematic Review

BACKGROUND

Numerous studies have identified detectable levels of neonicotinoids (neonics) in the environment, adverse effects of neonics in many species, including mammals, and pathways through which human exposure to neonics could occur, yet little is known about the human health effects of neonic exposure.

OBJECTIVE

In this systematic review, we sought to identify human population studies on the health effects of neonics.

METHODS

Studies published in English between 2005 and 2015 were searched using PubMed, Scopus, and Web of Science databases. No restrictions were placed on the type of health outcome assessed. Risk of bias was assessed using guidance developed by the National Toxicology Program's Office of Health Assessment and Translation.

RESULTS

Eight studies investigating the human health effects of exposure to neonics were identified. Four examined acute exposure: Three neonic poisoning studies reported two fatalities (n = 1,280 cases) and an occupational exposure study of 19 forestry workers reported no adverse effects. Four general population studies reported associations between chronic neonic exposure and adverse developmental or neurological outcomes, including tetralogy of Fallot (AOR 2.4, 95% CI: 1.1, 5.4), anencephaly (AOR 2.9, 95% CI: 1.0, 8.2), autism spectrum disorder [AOR 1.3, 95% credible interval (CrI): 0.78, 2.2], and a symptom cluster including memory loss and finger tremor (OR 14, 95% CI: 3.5, 57). Reported odds ratios were based on exposed compared to unexposed groups.

CONCLUSIONS

The studies conducted to date were limited in number with suggestive but methodologically weak findings related to chronic exposure. Given the wide-scale use of neonics, more studies are needed to fully understand their effects on human health. Citation: Cimino AM, Boyles AL, Thayer KA, Perry MJ. 2017. Effects of neonicotinoid pesticide exposure on human health: a systematic review. Environ Health Perspect 125:155-162; http://dx.doi.org/10.1289/EHP515.

Early-life chemical exposures and risk of metabolic syndrome

The global prevalence of obesity has been increasing at a staggering pace, with few indications of any decline, and is now one of the major public health challenges worldwide. While obesity and metabolic syndrome (MetS) have historically thought to be largely driven by increased caloric intake and lack of exercise, this is insufficient to account for the observed changes in disease trends. There is now increasing evidence to suggest that exposure to synthetic chemicals in our environment may also play a key role in the etiology and pathophysiology of metabolic diseases. Importantly, exposures occurring in early life (in utero and early childhood) may have a more profound effect on life-long risk of obesity and MetS. This narrative review explores the evidence linking early-life exposure to a suite of chemicals that are common contaminants associated with food production (pesticides; imidacloprid, chlorpyrifos, and glyphosate) and processing (acrylamide), in addition to chemicals ubiquitously found in our household goods (brominated flame retardants) and drinking water (heavy metals) and changes in key pathways important for the development of MetS and obesity.

Occurrence and Profile Characteristics of the Pesticide Imidacloprid, Preservative Parabens, and Their Metabolites in Human Urine from Rural and Urban China

Knowledge of human exposure to imidacloprid, the most extensively used insecticide, and para-hydroxybenzoic acid esters (parabens), the most extensively used preservative, is insufficient. In this study, 295 urine samples collected from subjects in rural and urban areas in China were analyzed for imidacloprid and four parabens (namely, methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) as well as their major metabolites (namely, 6-chloronicotinic acid (6-ClNA) and para-hydroxybenzoic acid (p-HB)). Imidacloprid was detected in 100% of the urine samples from rural Chinese subjects and 95% of the urine samples from urban Chinese subjects. Concentrations of urinary imidacloprid detected in rural Chinese subjects (geometric mean (GM) = 0.18 ng/mL) were slightly higher than those detected in urban Chinese subjects (GM = 0.15 ng/mL) when the effect of pesticide spraying was excluded. However, concentrations of urinary imidacloprid detected in rural adults increased significantly in the subsequent days of pesticide spraying (GM = 0.62 ng/mL), which could return to the normal levels within 3 days. In contrast, concentrations of urinary parabens detected in rural Chinese subjects (GM = 6.90 ng/mL) were lower than that in urban Chinese subjects (GM = 30.5 ng/mL). In addition, the metabolism characteristics of imidacloprid to 6-ClNA and parabens to p-HB were discussed preliminarily.

Neonicotinoid insecticides inhibit cholinergic neurotransmission in a molluscan (Lymnaea stagnalis) nervous system

Neonicotinoids are highly potent and selective systemic insecticides, but their widespread use also has a growing impact on non-target animals and contaminates the environment, including surface waters. We tested the neonicotinoid insecticides commercially available in Hungary (acetamiprid, Mospilan; imidacloprid, Kohinor; thiamethoxam, Actara; clothianidin, Apacs; thiacloprid, Calypso) on cholinergic synapses that exist between the VD4 and RPeD1 neurons in the central nervous system of the pond snail Lymnaea stagnalis. In the concentration range used (0.01-1 mg/ml), neither chemical acted as an acetylcholine (ACh) agonist; instead, both displayed antagonist activity, inhibiting the cholinergic excitatory components of the VD4-RPeD1 connection. Thiacloprid (0.01 mg/ml) blocked almost 90% of excitatory postsynaptic potentials (EPSPs), while the less effective thiamethoxam (0.1 mg/ml) reduced the synaptic responses by about 15%. The ACh-evoked membrane responses of the RPeD1 neuron were similarly inhibited by the neonicotinoids, confirming that the same ACh receptor (AChR) target was involved. We conclude that neonicotinoids act on nicotinergic acetylcholine receptors (nAChRs) in the snail CNS. This has been established previously in the insect CNS; however, our data indicate differences in the background mechanism or the nAChR binding site in the snail. Here, we provide the first results concerning neonicotinoid-related toxic effects on the neuronal connections in the molluscan nervous system. Aquatic animals, including molluscs, are at direct risk while facing contaminated surface waters, and snails may provide a suitable model for further studies of the behavioral/neuronal consequences of intoxication by neonicotinoids.

Injection of insect membrane in Xenopus oocyte: An original method for the pharmacological characterization of neonicotinoid insecticides

INTRODUCTION

Insect nicotinic acetylcholine receptors (nAChRs) represent a major target of insecticides, belonging to the neonicotinoid family. However, the pharmacological profile of native nAChRs is poorly documented, mainly because of a lack of knowledge of their subunit stoichiometry, their tissue distribution and the weak access to nAChR-expressing cells. In addition, the expression of insect nAChRs in heterologous systems remains hard to achieve. Therefore, the structure-activity characterization of nAChR-targeting insecticides is made difficult. The objective of the present study was to characterize insect nAChRs by an electrophysiological approach in a heterologous system naturally devoid of these receptors to allow a molecular/cellular investigation of the mode of action of neonicotinoids. Methods To overcome impediments linked to the expression of insect nAChR mRNA or cDNA, we chose to inject insect membranes from the pea aphid (Acyrthosiphon pisum) into Xenopus oocytes. This microtransplantation technique was designed to gain access to native nAChRs embedded in their membrane, through direct stimulation with nicotinic agonists. Results We provide evidence that an enriched-nAChR membrane allows us to characterize native receptors. The presence of such receptors was confirmed with fluorescent α-BgTX labeling. Electrophysiological recordings of nicotine-induced inward currents allowed us to challenge the presence of functional nAChR. We compared the effect of nicotine (NIC) with clothianidin (CLO) and we assessed the effect of thiamethoxam (TMX). Discussion This technique has been recently highlighted with mammalian and human material as a powerful functional approach, but has, to our knowledge, never been used with insect membrane. In addition, the use of the insect membrane microtransplantation opens a new and original way for pharmacological screening of neurotoxic insecticides, including neonicotinoids. Moreover, it might also be a powerful tool to investigate the pharmacological properties of insect nAChR.

Neonicotinoid Insecticides and Their Impacts on Bees: A Systematic Review of Research Approaches and Identification of Knowledge Gaps

It has been suggested that the widespread use of neonicotinoid insecticides threatens bees, but research on this topic has been surrounded by controversy. In order to synthesize which research approaches have been used to examine the effect of neonicotinoids on bees and to identify knowledge gaps, we systematically reviewed research on this subject that was available on the Web of Science and PubMed in June 2015. Most of the 216 primary research studies were conducted in Europe or North America (82%), involved the neonicotinoid imidacloprid (78%), and concerned the western honey bee Apis mellifera (75%). Thus, little seems to be known about neonicotinoids and bees in areas outside Europe and North America. Furthermore, because there is considerable variation in ecological traits among bee taxa, studies on honey bees are not likely to fully predict impacts of neonicotinoids on other species. Studies on crops were dominated by seed-treated maize, oilseed rape (canola) and sunflower, whereas less is known about potential side effects on bees from the use of other application methods on insect pollinated fruit and vegetable crops, or on lawns and ornamental plants. Laboratory approaches were most common, and we suggest that their capability to infer real-world consequences are improved when combined with information from field studies about realistic exposures to neonicotinoids. Studies using field approaches often examined only bee exposure to neonicotinoids and more field studies are needed that measure impacts of exposure. Most studies measured effects on individual bees. We suggest that effects on the individual bee should be linked to both mechanisms at the sub-individual level and also to the consequences for the colony and wider bee populations. As bees are increasingly facing multiple interacting pressures future research needs to clarify the role of neonicotinoids in relative to other drivers of bee declines.

Control of Pierce's Disease by Phage

Pierce's Disease (PD) of grapevines, caused by Xylella fastidiosa subsp. fastidiosa (Xf), is a limiting factor in the cultivation of grapevines in the US. There are presently no effective control methods to prevent or treat PD. The therapeutic and prophylactic efficacy of a phage cocktail composed of four virulent (lytic) phages was evaluated for control of PD. Xf levels in grapevines were significantly reduced in therapeutically or prophylactically treated grapevines. PD symptoms ceased to progress one week post-therapeutic treatment and symptoms were not observed in prophylactically treated grapevines. Cocktail phage levels increased in grapevines in the presence of the host. No in planta phage-resistant Xf isolates were obtained. Moreover, Xf mutants selected for phage resistance in vitro did not cause PD symptoms. Our results indicate that phages have great potential for biocontrol of PD and other economically important diseases caused by Xylella.

Monitoring Pesticide Residues in Surface and Ground Water in Hungary: Surveys in 1990–2015

Over 2000 surface, ground and raw drinking water samples have been analyzed in the frame of different monitoring projects in Hungary and watercourses in neighboring countries between 1990 and 2015. Effects of pesticide contamination on ecological farming and drinking water supply have been assessed. Main water pollutant ingredients of agricultural origin in Hungary are herbicides related to maize production. After EU pesticide re-registration, diazinon, atrazine, and trifluralin gradually disappeared as contaminants. High levels of water soluble pollutants (e.g., acetochlor) in surface water result in temporarily enhanced levels in raw drinking water as well. Extreme levels observed for herbicide residues were of agrochemical industrial origin.