Detection of Neonicotinoid Insecticides and Their Metabolites in Human Cerebrospinal Fluid

Aptamer-based biosensors for the detection of neonicotinoid insecticides in environmental samples: A systematic review

Neonicotinoids, sometimes abbreviated as neonics, represent a class of neuro-active insecticides with chemical similarities to nicotine. Neonicotinoids are the most widely adopted group of insecticides globally since their discovery in the late 1980s. Their physiochemical properties surpass those of previously established insecticides, contributing to their popularity in various sectors such as agriculture and wood treatment. The environmental impact of neonicotinoids, often overlooked, underscores the urgency to develop tools for their detection and understanding of their behavior. Conventional methods for pesticide detection have limitations. Chromatographic techniques are sensitive but expensive, generate waste, and require complex sample preparation. Bioassays lack specificity and accuracy, making them suitable as preliminary tests in conjunction with instrumental methods. Aptamer-based biosensor is recognized as an advantageous tool for neonicotinoids detection due to its rapid response, user-friendly nature, cost-effectiveness, and suitability for on-site detection. This comprehensive review represents the inaugural in-depth analysis of advancements in aptamer-based biosensors targeting neonicotinoids such as imidacloprid, thiamethoxam, clothianidin, acetamiprid, thiacloprid, nitenpyram, and dinotefuran. Additionally, the review offers valuable insights into the critical challenges requiring prompt attention for the successful transition from research to practical field applications.

Ubiquity of Synthetic Phenolic Antioxidants in Children's Cerebrospinal Fluid from South China: First Evidence for Their Penetration across the Blood-Cerebrospinal Fluid Barrier

Synthetic phenolic antioxidants (SPAs) and relevant transformation products (TPs) are potentially neurotoxic pollutants to which humans are widely exposed. However, their penetration behavior across the brain barrier and associated exposure to the central nervous system (CNS) remain unknown. This study is the first to investigate a wide range of 30 SPAs and TPs, including emerging SPAs, in matched serum and cerebrospinal fluid (CSF) samples from children in Guangzhou, China. Sixty-two children of either sex aged <14 years with nonbloody CSF and complete clinical information were included. The findings demonstrated the ubiquitous occurrence of many SPAs and TPs, particularly BHT, 2,4-di-tert-butylphenol (DBP), AO 1010, AO 1076, BHT-Q, and BHT-quinol, not only in serum but also in the CSF. Median total concentrations of SPAs and TPs were up to 22.0 and 2.63 ng/mL in serum and 14.5 and 2.11 ng/mL in CSF, respectively. On calculating the penetration efficiencies across the blood-CSF barrier (BCSFB) (RCSF/serum, CCSF/Cserum) for selected SPAs and TPs, their RCSF/serum values (median 0.52-1.41) were highly related to their physicochemical properties, indicating that passive diffusion may be the potential mechanism of BCSFB penetration. In addition, the RCSF/serum values were positively correlated with the barrier permeability index RAlb (AlbuminCSF/Albuminserum), indicating that barrier integrity is an important determinant of BCSFB penetration. Overall, these results will improve our perception of human internal exposure to SPAs and lay a solid foundation for assessing the risk of CNS exposure to various SPAs.

Statement on the toxicological properties and maximum residue levels of acetamiprid and its metabolites

Acetamiprid is a pesticide active substance with insecticidal action whose approval was renewed by Commission Implementing Regulation (EU) 2018/113. In January 2022, the EFSA PPR Panel published a statement following a request from the European Commission to advise on human health or the environment based on new scientific evidence presented by France during the decision-making phase. In July 2022, by means of a further mandate received from the European Commission, EFSA was requested to provide advice if new information and any other scientific evidence that has become available since the assessment conducted for the renewal in 2018 warrant re-evaluation of (i) toxicological parameters used for the risk assessment of acetamiprid during the renewal process, including toxicological endpoints; (ii) the residue definition for acetamiprid in products of plant origin; and (iii) the safety of existing maximum residue levels (MRLs). Meanwhile, the applicant of acetamiprid in the EU submitted new toxicology studies regarding the toxicological profile of the metabolite IM-2-1. Furthermore, the European Commission was made aware that several recent publications in scientific literature were made available after the literature searches conducted by EFSA. As the new data could affect the advice that EFSA was expected to deliver through the 2022 mandate, EFSA was further requested to consider this information by means of a revised mandate received in September 2023. As regards re-evaluation of point (i) in this statement, this was addressed by an EFSA Working Group integrating all the available evidence. The results of the weight of evidence indicated that there are major uncertainties in the body of evidence for the developmental neurotoxicity (DNT) properties of acetamiprid and further data are therefore needed to come to a more robust mechanistic understanding to enable appropriate hazard and risk assessment. In view of these uncertainties, the EFSA WG proposed to lower the acceptable daily intake (ADI) and acute reference dose (ARfD) from 0.025 to 0.005 mg/kg body weight (per day). A revised residue definition for risk assessment was proposed for leafy and fruit crops as sum of acetamiprid and N-desmethyl-acetamiprid (IM-2-1), expressed as acetamiprid. Regarding pulses/oilseeds, root crops and cereals, the new data received did not indicate a need to modify the existing residue definition for risk assessment, which therefore remains as parent acetamiprid. Regarding the residue definition for enforcement, the available data did not indicate a need to modify the existing definition because acetamiprid is still a sufficient marker of the residues in all crop groups. Considering the new health-based guidance values derived in the present statement, a risk for consumer has been identified for 38 MRLs currently in place in the EU Regulation. Consequently, EFSA recommended to lower the existing MRLs for 38 commodities based on the assessment of fall-back Good Agricultural Practices received within an ad hoc data call. Some fall-back MRLs proposals require further risk management considerations.

Exposure levels and health implications of fungicides, neonicotinoid insecticides, triazine herbicides and their associated metabolites in pregnant women and men

Exposure to pesticides can pose a series of advance effects on human health. However, the exposure levels and health implications of the current use pesticides and their metabolites in both men and pregnant women remain unclear. In this study, an analytical method was developed to quantify fungicides, neonicotinoid insecticides, triazine herbicides, and their metabolites in the human serum. Fifty of the 73 target pesticides and metabolites were detected in the human serum of men and pregnant women from Wuxi, China, which included 11 triazine herbicides and metabolites, 17 neonicotinoid insecticides and metabolites, and 22 fungicides. Fungicides had the highest cumulative concentration (49.5 ng/mL), followed by neonicotinoid insecticides and metabolites (6.38 ng/mL), and triazine herbicides and metabolites (5.10 ng/mL). Moreover, the estimated daily intake (EDI) of fungicides was 10.4 and 12.7 times higher than that of triazine herbicides (included their metabolites) and neonicotinoid insecticides (included their metabolites), respectively. Of the three categories of pesticides, exposure to fungicides contributed to the highest exposure risk within the hazard quotient in the range of 5.1 × 10-3-0.17. Correlation analysis revealed that the pesticide exposure levels in human serum were correlated with their maximum residue levels in vegetables and fruits. Pesticide exposure has also been correlated with the weight and Body Mass Index (BMI) of humans based on structural equation modeling. This study provides new insights into the exposure of men and pregnant women to a cocktail of fungicides, neonicotinoid insecticides, triazine herbicides and their metabolites.

Pesticide residues in adults living near a bioenergy plant with 85,000 tons of contaminated wetcake

Neonicotinoid insecticide use is on the rise worldwide due to its broad-spectrum insecticidal action and exclusive approach of neurotoxic action. Besides application during the cultivation of several crops, all seed companies coat their seeds with neonicotinoids to have increased protection against insects during germination. Despite reduced mammalian toxicity, neonicotinoids have harmful effects on non-target non-mammalian organisms such as bees, an essential part of maintaining the ecosystem. In addition, epidemiologic studies have linked human exposure to neonicotinoids with poor developmental and neurological outcomes. Starting in 2015, the AltEn bioenergy plant near Mead, Nebraska, USA, used coated seeds for their ethanol production and failed to properly dispose of byproducts, causing environmental contamination that still exists. This pilot study reports the human urinary levels of neonicotinoids in samples collected during 2022-2023 in the population living in areas close to this now-closed bioenergy plant. Our results show that approximately 30% of the urine samples are contaminated with at least one of the targeted neonicotinoids or their transformed products. The most frequently detected parent neonicotinoid was clothianidin, which accounts for 13% of the samples. However, 5-hydroxy-imidacloprid, the transformed imidacloprid product, is detected in 27% of the samples, ranging from 1.2 to 42 ng/mL. In conclusion, the environmental contamination near Mead, Nebraska, due to improper storage and disposal of highly contaminated byproducts, puts the nearby population at risk from continuous exposure to neonicotinoids through air and dust particles and possible water contamination.

A salting-out assisted liquid-liquid extraction method for 25 emerging pesticides in follicular fluid

Emerging pesticides of neonicotinoids (NEOs) and "Universal Pesticides" (UPs) are a growing global concern due to their growing commercial importance and potential risks to human health. The currently available analytical methods for these pesticides in biomonitoring were usually tailored for limited number of analytes, or were time consuming and costly. In this study, an efficient and sensitive method for the analysis of 16 NEOs and nine UPs in human follicular fluid (FF) was developed by using a salting-out assisted liquid-liquid extraction (SALLE) method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method performance was evaluated by calibration linearity (r > 0.99), sensitivity at limits of quantification (0.01-0.50 ng/mL), accuracy at relative recoveries (81-117%) and precision at relative standard deviations (≤16%). The developed method was further validated by analyzing 21 human FF samples that were collected from a hospital in Guangzhou, China. Among the 25 study analytes, two NEOs and six UPs had their detection rates over 85% and medians at 0.048-0.808 ng/mL in the FF samples. Considering the well-known toxicity of these pesticides and their metabolites, it is urgent to figure out exposure profiles of study pesticides and potential reproductive risk for women. To the best of our knowledge, this study is the first to develop and apply the SALLE method in the extraction of 16 NEOs and nine UPs simultaneously in human FF.

Neonicotinoids residues in cow milk and health risks to the Chinese general population

The application of neonicotinoid insecticides (NEOs) has increased dramatically in the world since being introduced in 1990s, yet the extent of human exposure and potential health risk is not fully unraveled. In this study, the residues were analyzed of 16 NEOs and their metabolites in 205 commercial cow milk samples circulating in Chinese market. All the milk samples contained at least one quantified NEO, and over 90% of samples contained a cocktail of NEOs. Acetamiprid, N-desmethyl acetamiprid, thiamethoxam, clothianidin and imidaclothiz were the most commonly detected analytes with detection frequencies of 50-88% and medians of 0.011-0.038 ng/mL in milk. Geographical origin was an important factor to influence abundances and levels of NEOs contamination in milk. Chinese local milk bore a significant higher risk from NEOs contamination than the imported milk. In China, the northwest presented the greatest concentrations of the insecticides relative to the north or south. Organic farming, ultra heat treatment and skimming could significantly reduce levels of NEOs contamination in milk. A relative potency factor method was used to evaluate estimated daily intake of NEO insecticides, and found the children had 3.5-5 times higher exposed risk via milk ingestion than the adults. The high frequency of NEOs detection in milk offers us a snapshot of the ubiquity of NEOs in milk, with possible health implications especially for children.

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.

Photolysis mechanism of eleven insecticides under simulated sunlight irradiation: Kinetics, pathway and QSAR

Insecticides are widely used in crop protection against insects and frequently detected in aquatic environment. Photolysis kinetics are directly related with exposure assessment and risk assessment. However, the photolysis mechanism of neonicotinoid insecticides with different structures has not been studied and compared systematically in the literature. In this paper, the photolysis rate constants in water were determined for eleven insecticides under irradiation of simulated sunlight. At the same time, the photolysis mechanism and effect of dissolved organic matter (DOM) on their photolysis were studied. The results showed that photolysis rates of eleven insecticides vary in a large range. The photolysis rates of nitro-substituted neonicotinoids and butenolide insecticide are much faster than that of cyanoimino-substituted neonicotinoids and sulfoximine insecticide. The ROS scavenging activity assays reveal that direct photolysis dominates the degradation of seven insecticides and, on the other hand, self-sensitized photolysis dominates four insecticides. The shading-effect from DOM can reduce the direct photolysis rates, on the other hand, ROSs generated by triplet-state DOM (³DOM*) can also accelerate photolysis of insecticides. According to the photolytic products identified from HPLC-MS, these eleven insecticides have different photolysis pathways. Six insecticides are degraded from the removal of nitro group from their parent compounds and four insecticides are degraded through ·OH reaction or singlet oxygen (¹O₂) reaction. QSAR (quantitative structure-activity relationship) analysis showed that photolysis rate was directly related to the energy gap between the highest occupied molecular orbital to the lowest unfilled molecular orbital (E_gap = E_LUMO-E_HOMO) and dipole moment (δ). These two descriptors reflect the chemical stability and reactivity of insecticides. The pathways developed from identified products and the molecular descriptors of QSAR models can well verify the photolysis mechanisms of eleven insecticides.