The effect of mixtures of organophosphate and carbamate pesticides on acetylcholinesterase and application of chemometrics to identify pesticides in mixtures

Integrated evaluation of the biological response of the earthworm Eisenia fetida using two glyphosate exposure strategies: soil enriched and soils collected from crops in Southeastern Mexico

Under laboratory conditions, the toxicological effects of pesticides tend to be less variable and realistic than under field conditions, limiting their usefulness in environmental risk assessment. In the current study, the earthworm Eisenia fetida was selected as a bioindicator for assessing glyphosate toxic effects in two different trials to solve this dilemma. In Trial 1, the worms were exposed for 7 and 14 days to concentrations of a commercial glyphosate formulation (1 to 500 mg a.i. kg-1) currently used in the field. In Trial 2, the worms were kept in nine soils collected from different plots with crops for 14 days of exposure. In both experiments, glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and acetylcholinesterase (AChE) activities and contents of lipid peroxidation (LPO) were evaluated. In T1, the glyphosate formulation produced a 40% inhibition of AChE activity and a significant increase in GST, SOD, CAT, and GPx activities and LPO contents in E. fetida on day 7. In T2, higher concentrations of glyphosate were detected in the soils of soybean, papaya, and corn (0.92, 0.87, and 0.85 mg kg-1), which induced a positive correlation between the levels of glyphosate residues with GST, SOD, CAT, GPx, and LPO and a negative correlation with AChE. These findings indicate that crop soils polluted with glyphosate elicited higher oxidative stress than under laboratory conditions, confirmed by IBRv2, PCA, and AHC analyses.

Pesticides impacts on human health and the environment with their mechanisms of action and possible countermeasures

Pesticides are chemical constituents used to prevent or control pests, including insects, rodents, fungi, weeds, and other unwanted organisms. Despite their advantages in crop production and disease management, the use of pesticides poses significant hazards to the environment and public health. Pesticide elements have now perpetually entered our atmosphere and subsequently contaminated water, food, and soil, leading to health threats ranging from acute to chronic toxicities. Pesticides can cause acute toxicity if a high dose is inhaled, ingested, or comes into contact with the skin or eyes, while prolonged or recurrent exposure to pesticides leads to chronic toxicity. Pesticides produce different types of toxicity, for instance, neurotoxicity, mutagenicity, carcinogenicity, teratogenicity, and endocrine disruption. The toxicity of a pesticide formulation may depend on the specific active ingredient and the presence of synergistic or inert compounds that can enhance or modify its toxicity. Safety concerns are the need of the hour to control contemporary pesticide-induced health hazards. The effectiveness and implementation of the current legislature in providing ample protection for human health and the environment are key concerns. This review explored a comprehensive summary of pesticides regarding their updated impacts on human health and advanced safety concerns with legislation. Implementing regulations, proper training, and education can help mitigate the negative impacts of pesticide use and promote safer and more sustainable agricultural practices.

Evaluation of multiple organophosphate insecticide exposure in relation to altered thyroid hormones in NHANES 2007-2008 adult population

The thyroid gland is susceptible to chemical exposure such as organophosphate insecticides (OPIs). With the ubiquitous nature of these products, humans are simultaneously exposed to a multitude of chemicals. This study aimed to evaluate the association between an individual and a mixture of OPI metabolites and changes in serum thyroid hormone (TH) concentrations. The analyzed data were 1,434 participants from the United States National Health and Nutrition Examination Surveys (NHANES) cycle 2007-2008. Generalized linear model (GLM) regression, weighted quantile sum (WQS), and adaptive least absolute shrinkage and selection operator (adaptive LASSO) regression were used to investigate the associations between urinary OPI metabolites and altered serum THs. In GLM, all of the five urinary OPI metabolites were inversely associated with free triiodothyronine (FT3) among the male subjects; meanwhile, higher thyroglobulin (Tg) was related to dimethylphosphate (DMP). Moreover, in WQS models, the metabolite mixture induced FT3 down-regulation (β = -0.209 (95% CI: -0.310, -0.114)), and caused an increased Tg concentration (β = 0.120 (95% CI: 0.024, 0.212)), however, any significant association was observed among female participants. Consistently, the weighted index and LASSO coefficient demonstrated dimethylthiophosphate (DMTP) as the strongest metabolite in the FT3 model (mean weight= 3.449e-01 and β =-0.022, respectively), and dimethylphosphate (DMP) represented the highest association in the Tg model (mean weight= 9.873e-01 and β =-0.020, respectively). Further research is required to confirm our results and investigate the clinical impacts of these disruptions.

Assessment of the impacts of GABA and AChE targeting pesticides on freshwater invertebrate family richness in English Rivers

Globally, riverine system biodiversity is threatened by a range of stressors, spanning pollution, sedimentation, alterations to water flow, and climate change. Pesticides have been associated with population level impacts on freshwater invertebrates for acute high-level exposures, but far less is known about the chronic impact of episodic exposure to specific classes of pesticides or their mixtures. Here we employed the use of the UK Environment Agency's monitoring datasets over 40 years (covering years 1980 to 2019) to assess the impacts of AChE (acetylcholinesterase) and GABA (gamma-aminobutyric acid) receptor targeting pesticides on invertebrate family richness at English river sites. Concentrations of AChE and GABA pesticides toxic to freshwater invertebrates occurred (measured) across 18 of the 66 river sites assessed. For one of the three river sites (all found in the Midlands region of England) where data recorded over the past 40 years were sufficient for robust modelling studies, both AChE and GABA pesticides associated with invertebrate family richness. Here, where AChE total pesticide concentrations were classified as high, 46 of 64 invertebrate families were absent, and where GABA total pesticide concentration were classified as high, 16 of 64 invertebrate families were absent. Using a combination of field evidence and laboratory toxicity thresholds for population relevant endpoints we identify families of invertebrates most at risk in the selected English rivers to AChE and GABA pesticides. We, furthermore, provide strong evidence that the absence of the invertebrate family Polycentropodidae (caddisfly) from one field site is due to exposure effects to AChE pesticides.

Neurotoxicity in complex environmental mixtures-a case-study at River Danube in Novi Sad (Serbia) using zebrafish embryos

Acetylcholinesterase (AChE) inhibitors are an important class of neuroactive chemicals that are often detected in aquatic and terrestrial environments. The correct functionality of the AChE enzyme is linked to many important physiological processes such as locomotion and respiration. Consequently, it is necessary to develop new analytical strategies to identify harmful AChE inhibitors in the environment. It has been shown that mixture effects and oxidative stress may jeopardize the application of in vivo assays for the identification of AChE inhibitors in the environment. To confirm that in vivo AChE assays can be successfully applied when dealing with complex mixtures, an extract from river water impacted by non-treated wastewater was bio-tested using the acute toxicity fish embryo test (FET) and AChE inhibition assay with zebrafish. The zebrafish FET showed high sensitivity for the extract (LC10 = relative extraction factor 2.8) and we observed a significant inhibition of the AChE (40%, p < 0.01) after 4-day exposure. Furthermore, the extract was chromatographically fractionated into a total of 26 fractions to dilute the mixture effect and separate compounds according to their physico-chemical properties. As expected, non-specific acute effects (i.e., mortality) disappeared or evenly spread among the fractions, while AChE inhibition was still detected in five fractions. Chemical analysis did not detect any known AChE inhibitors in these active fractions. These results confirm that the AChE assay with Danio rerio can be applied for the detection of neuroactive effects induced in complex environmental samples, but also, they highlight the need to increase analytical and identification techniques for the detection of neurotoxic substances.

Nanozymes paper-based analytical device for the detection of organophosphate pesticides in fruits and vegetables

In this work, copper oxide nanoparticles (CuONPs) nanozymes paper-based analytical device was designed for the rapid detection of organophosphate pesticides in fruits and vegetables. The paper-based analytical device was modified with silica oxide nanoparticles to enhance the assay sensitivity. CuO nanozymes displayed peroxidase-like activity and catalyzed the oxidation of o-dianisidine in the presence of H₂O₂ from the hydrolysis of acetylthiocholine. This results in the formation of a brown-colored product. In the presence of organophosphate pesticides such as malathion, acetylcholinesterase activity was inhibited, resulting in reduced color intensity production, and which was measured with a smartphone. The proposed nanozymes paper-based analytical device exhibited a good linear detection range (0.1-5 mg L^-1), a low detection limit of 0.08 mg L^-1, and the analysis time was only about 10 min for malathion detection under optimal conditions. Moreover, the CuONPs had excellent catalytic activity and higher stability than peroxidase. Finally, this device can be applied to detect organophosphate pesticides in fruits and vegetables with rapidity, accuracy, portability, and ease of handling in the field.

Acetylcholinesterase biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine neurotransmitter: A literature review

Neurotoxic pesticides are a group of chemicals that pose a severe threat to both human health and the environment. These molecules are also known to accumulate in the food chain and persist in the environment, which can lead to long-term exposure and adverse effects on non-target organisms. The detrimental effects of these pesticides on neurotransmitter levels and function can lead to a range of neurological and behavioral symptoms, which are closely associated with neurodegenerative diseases. Hence, the accurate and reliable detection of these neurotoxic pesticides and associated neurotransmitters is essential for clinical applications, such as diagnosis and treatment. Over the past few decades, acetylcholinesterase (AchE) biosensors have emerged as a sensitive and reliable tool for the electrochemical detection of neurotoxic pesticides and acetylcholine. These biosensors can be tailored to utilize the high specificity and sensitivity of AchE, enabling the detection of these chemicals. Additionally, enzyme immobilization and the incorporation of nanoparticles have further improved the detection capabilities of these biosensors. AchE biosensors have shown tremendous potential in various fields, including environmental monitoring, clinical diagnosis, and pesticide residue analysis. This review summarizes the advancements in AchE biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine over the past two decades.

Data-driven learning of narcosis mode of action identifies a CNS transcriptional signature shared between whole organism Caenorhabditis elegans and a fish gill cell line

With the large numbers of man-made chemicals produced and released in the environment, there is a need to provide assessments on their potential effects on environmental safety and human health. Current regulatory frameworks rely on a mix of both hazard and risk-based approaches to make safety decisions, but the large number of chemicals in commerce combined with an increased need to conduct assessments in the absence of animal testing makes this increasingly challenging. This challenge is catalysing the use of more mechanistic knowledge in safety assessment from both in silico and in vitro approaches in the hope that this will increase confidence in being able to identify modes of action (MoA) for the chemicals in question. Here we approach this challenge by testing whether a functional genomics approach in C. elegans and in a fish cell line can identify molecular mechanisms underlying the effects of narcotics, and the effects of more specific acting toxicants. We show that narcosis affects the expression of neuronal genes associated with CNS function in C. elegans and in a fish cell line. Overall, we believe that our study provides an important step in developing mechanistically relevant biomarkers which can be used to screen for hazards, and which prevent the need for repeated animal or cross-species comparisons for each new chemical.

Facile synthesis, larvicidal activity, biological effects, and molecular docking of sulfonamide-incorporating quaternary ammonium iodides as acetylcholinesterase inhibitors against Culex pipiens L

Insecticides participate with a vital role in our lives especially in preventing the spread of human diseases via controlling the dangerous pests. It is a challenge to identify alternatives to the ordinary insecticides with new mode of action to be used for mosquitoes' control in an environmentally sustainable manner. Using a facile two-step procedure, three novel series of sulfonamide-incorporating quaternary ammonium iodides (3a-i, 4a-i and 5a-i) were synthesized and their chemical structures were successfully characterized. The uncharged sulfonamide intermediates (2a-i) were constructed through simple amidation of the corresponding (hetero)aryl sulfonyl chlorides then the cationic target molecules were formed by quaternizing the tertiary nitrogen with methyl, ethyl, and allyl iodides. The larvicidal activities and biological effects of most synthesized compounds against Culex pipiens L. were extensively investigated and they exhibited good and comparable activities to temephos. Among these hybrids, 4a showed the most potent activity with LC₅₀ = 26.71 ppm. Additionally, the developmental durations of larval and pupal stages were significantly prolonged after treatment with all concentrations of 4h. At high concentration (160 ppm) of 4a and 4b, no adults emerged due to the complete death of pupae, and consequently zero growth index. Moreover, the results of the molecular docking demonstrated that the activities of compounds correlate partially to their binding with acetylcholinesterase (AChE) and it is not the sole parameter for determining the activity.

Risk evaluation of occupational exposure of southern Brazilian flower farmers to pesticides potentially leading to cholinesterase inhibition and metals exposure

This work presents a frequency matched observational study comparing flower farmers exposed to pesticides and unexposed individuals as controls. All subjects were interviewed before plasma and urine collection. Manganese and Zinc were measured in theses samples by using dynamic reaction cell inductively coupled mass spectrometry. Cholinesterase activity was analyzed through spectrophotometry by using a modified version of the Ellman method. Seventy-eight percent of subjects reported occupational contact with pesticides, from which 37% reported exposure for over 9 years. Flower farms farmers had increased odds of having headache and irritability, respectively, by factors of 6.2 and 2.4 than the control subjects. While the odds of exposed subjects to have insomnia was smaller than control subjects by a factor of 0.34. Exposure to pesticides had a significant effect regarding the plasmatic plasma and urinary manganese levels and whole blood cholinesterase activity (p < 0.05). High levels of plasma and urinary manganese, as well as cholinesterase inhibition in whole blood, were evident in the flower farmers who participated in the study.

Residential proximity to pesticide applications in Argentine Patagonia: impact on pregnancy and newborn parameters

Among residents living close to agricultural fields who are potentially exposed to pesticides, pregnant women and their fetuses are of particular concern for their vulnerability to environmental chemicals. In this collaborative multicenter study, we covered a wide distribution of participants in the most important fruit production zone of north Patagonia (Argentina) to investigate whether maternal residential proximity to fruit croplands with intense pesticide applications (rural group -RG-) is associated with pregnancy complications and alterations in their newborn parameters compared to the urban population (urban group -UG-). A total of 776 pregnant women met the inclusion criteria. The percentage of threatened miscarriage was significantly higher in the RG than in the UG. The percentage of miscarriage, threat of premature labor, intrauterine fetal death, preterm premature rupture of membranes, and intrauterine growth retardation were similar in both groups. Newborn anthropometric parameters were corrected by sex and gestational age prior to statistical analysis. Length at birth and head circumference were lower in the RG than in the UG. Birth weight was similar in both groups. The percentage of head circumference less than the 5th percentile and the ponderal index were greater in the RG than in the UG. Our results suggest that proximity to pesticide applications may increase the risk of pregnancy complications and altered newborn parameters.

21-Day dermal exposure to aircraft engine oils: effects on esterase activities in brain and liver tissues, blood, plasma, and clinical chemistry parameters for Sprague Dawley rats

This dermal study tested the potential toxicity of grade 3 (G3) and 4 (G4) organophosphate-containing aircraft engine oils in both new (G3-N, G4-N) and used states (G3-U, G4-U) to alter esterase activities in blood, brain and liver tissues, clinical chemistry parameters, and electrophysiology of hippocampal neurons. A 300 µl volume of undiluted oil was applied in Hill Top Chamber Systems®, then attached to fur-free test sites on backs of male and female Sprague Dawley rats for 6 hr/day, 5 days/week for 21 days. Recovery rats received similar treatments and kept for 14 days post-exposure to screen for reversibility, persistence, or delayed occurrence of toxicity. In brain, both versions of G3 and G4 significantly decreased (32-41%) female acetylcholinesterase (AChE) activity while in males only G3-N and G4-N reduced (33%) AChE activity. Oils did not markedly affect AChE in liver, regardless of gender. In whole blood, G3-U decreased female AChE (29%) which persisted during recovery (32%). G4-N significantly lowered (29%) butyrylcholinesterase (BChE) in male plasma, but this effect was resolved during recovery. For clinical chemistry indices, only globulin levels in female plasma significantly increased following G3-N or G4-N exposure. Preliminary electrophysiology data suggested that effects of both versions of G3 and G4 on hippocampal function may be gender dependent. Aircraft maintenance workers may be at risk if precautions are not taken to minimize long-term aircraft oil exposure.

Behavioral changes occur earlier than redox alterations in developing zebrafish exposed to Mancozeb

As agriculture expands to provide food and wellbeing to the world's growing population, there is a simultaneous increasing concern about the use of agrochemicals, which can harm non-target organisms, mainly in the aquatic environment. The fungicide Mancozeb (MZ) has been used on a large-scale and is a potent inducer of oxidative stress. Therefore, there is an urgent need for the development of more sensitive biomarkers designed to earlier biomonitoring of this compound. Here we tested the hypothesis that behavioral changes induced by sublethal MZ concentrations would occur first as compared to biochemical oxidative stress markers. Embryos at 4 h post-fertilization (hpf) were exposed to Mancozeb at 5, 10 and 20 μg/L. Controls were kept in embryo water only. Behavioral and biochemical parameters were evaluated at 24, 28, 72, and 168 hpf after MZ exposure. The results showed that MZ significantly altered spontaneous movement, escape responses, swimming capacity, and exploratory behavior at all exposure times. However, changes in ROS steady-stead levels and the activity of antioxidant enzymes were observable only at 72 and 168 hpf. In conclusion, behavioral changes occurred earlier than biochemical alterations in zebrafish embryos exposed to MZ, highlighting the potential of behavioral biomarkers as sensitive tools for biomonitoring programs.

Role of environmental pollutants in Alzheimer's disease: a review

Neurodegenerative disorders are commonly erratic influenced by various factors including lifestyle, environmental, and genetic factors. In recent observations, it has been hypothesized that exposure to various environmental factors enhances the risk of Alzheimer's disease (AD). The exact etiology of Alzheimer's disease is still unclear; however, the contribution of environmental factors in the pathology of AD is widely acknowledged. Based on the available literature, the review aims to culminate in the prospective correlation between the various environmental factors and AD. The prolonged exposure to the various well-known environmental factors including heavy metals, air pollutants (particulate matter), pesticides, nanoparticles containing metals, industrial chemicals results in accelerating the progression of AD. Common mechanisms have been documented in the field of environmental contaminants for enhancing amyloid-β (Aβ) peptide along with tau phosphorylation, resulting in the initiation of senile plaques and neurofibrillary tangles, which results in the death of neurons. This review offers a compilation of available data to support the long-suspected correlation between environmental risk factors and AD pathology. Graphical abstract .

Combined Toxicity of Cannabidiol Oil with Three Bio-Pesticides against Adults of Sitophilus Zeamais, Rhyzopertha Dominica, Prostephanus Truncatus and Trogoderma Granarium

The present study investigates the interaction between cannabidiol (CBD) oil and three biopesticides: Azatin and two baculovirus formulations (Madex and Helicovex), both separately and in combination, in order to investigate their interaction against adults of four major coleopteran stored-product pests: Sitophilus zeamais (Coleoptera: Curculionidae), Rhyzopertha dominica (Coleoptera: Bostrichidae), Prostephanus truncatus (Coleoptera: Bostrichidae) and Trogoderma granarium (Coleoptera: Dermestidae). CBD, which has been understudied for its insecticidal properties, was applied at three different doses (500, 1500 and 3000 ppm). The biopesticides were administered at 1500 ppm. Interactions in the combined treatments were mathematically estimated as not synergistic and mostly competitive except for the combined treatments of CBD (1500 and 3000 ppm) with Azatin (1500 ppm) which were marked by an additive interaction. In its individual application, CBD oil generated the highest insect mortality while its effect was clearly dose-dependent. The findings reveal a promising effect of CBD oil against these coleopterans which had not been previously tested together.

Biocontrol potential of methyl chavicol for managing Spodoptera frugiperda (Lepidoptera: Noctuidae), an important corn pest

Synthetic insecticides applied to control Spodoptera frugiperda (Lepidoptera: Noctuidae) can have negative impacts on environment and human health. Botanical essential oils can be sources of organic molecules with biocontrol potential and advantages, such as minor impacts on the selection of resistant pest insects and low toxicity to humans. The aim of this study was to investigate the biocontrol action of essential oils from Brazilian species and methyl chavicol compounds on the development and metabolism of S. frugiperda. Essential oils of Eremanthus erythropappus (Asteraceae), Ocimum selloi, Hyptis suaveolens, and Hyptis marrubioides (Lamiaceae) were distilled by the steam distillation method and analyzed by gas chromatograph techniques. The essential oils were incorporated into an artificial diet (at 1, 2, and 4 mg mL^-1) and offered to S. frugiperda caterpillars. Larvae of S. frugiperda at 48 h of age were fed an artificial diet containing the major constituent of O. selloi (methyl chavicol). The major compounds of the essential oils were methyl chavicol for O. selloi, α-bisabolol for E. erythropappus, bicyclogermacrene for H. suaveolens, and β-thujone for H. marrubioides. O. selloi caused 100% mortality in S. frugiperda larvae at a concentration of 1 mg mL^-1 after 48 h. H. marrubioides essential oil caused 100% mortality in larvae at a concentration of 4 mg mL^-1 after 48 h. O. selloi and H. marrubioides inhibited acetylcholinesterase (AchE) activity in 72.87% and 81.69% of larvae, respectively. O. selloi presented the highest toxicity to S. frugiperda and the lowest inhibition of AchE. Methyl chavicol was lethal to all larvae within 24 h at a concentration of 0.92 mg mL^-1 of diet. Methyl chavicol showed the best insecticidal activity and potential to be used as a natural insecticide to control S. frugiperda.

Immunological response of white shrimp (Litopenaeus vannamei) to sublethal concentrations of malathion and endosulfan, and their mixture

Cellular and humoral responses were evaluated in Litopenaeus vannamei juveniles when exposed to malathion, endosulfan, and their mixture. Each experiment was performed in the hemolymph collected at each exposure time (5 and 96 h) in duplicate; total hemocyte count, coagulation time, hemocyanin concentration, phenoloxidase (PO) and superoxide dismutase (SOD) activities were quantified. Survival was not affected by pesticides applied individually and mixed. Clotting time did not show significant differences concerning increase of concentration percentage of the pesticides tested. In organisms exposed to the pesticide mixture, hemocyanin decreased at 5 h of exposure as the concentration increased. Only in the malathion experiment did exposed shrimp to 10 and 50% of the LC₅₀-96 h show significantly (p < 0.05) higher hemocyte contents. For malathion, significantly (p < 0.05) lower PO values in shrimp exposed to higher concentrations (10 and 50% of the LC₅₀-96 h) were determined. While for the mixture treatment, high SOD value was determined at high exposure time and concentration. Malathion was the pesticide that showed an effect on some variables even at sublethal concentrations. The Continuous Concentration Criteria of the United States Environmental Protection Agency did not represent effects on the variables when they were compared with the averages of the control group.

Neurotoxicity of pesticides

Pesticides are unique environmental contaminants that are specifically introduced into the environment to control pests, often by killing them. Although pesticide application serves many important purposes, including protection against crop loss and against vector-borne diseases, there are significant concerns over the potential toxic effects of pesticides to non-target organisms, including humans. In many cases, the molecular target of a pesticide is shared by non-target species, leading to the potential for untoward effects. Here, we review the history of pesticide usage and the neurotoxicity of selected classes of pesticides, including insecticides, herbicides, and fungicides, to humans and experimental animals. Specific emphasis is given to linkages between exposure to pesticides and risk of neurological disease and dysfunction in humans coupled with mechanistic findings in humans and animal models. Finally, we discuss emerging techniques and strategies to improve translation from animal models to humans.

Structure-based design and application of an engineered glutathione transferase for the development of an optical biosensor for pesticides determination

In the present work, a structure-based design approach was used for the generation of a novel variant of synthetic glutathione transferase (PvGmGSTU) with higher sensitivity towards pesticides. Molecular modelling studies revealed Phe117 as a key residue that contributes to the formation of the hydrophobic binding site (H-site) and modulates the affinity of the enzyme towards xenobiotic compounds. Site-saturation mutagenesis of position Phe117 created a library of PvGmGSTU variants with altered kinetic and binding properties. Screening of the library against twenty-five different pesticides, showed that the mutant enzyme Phe117Ile displays 3-fold higher catalytic efficiency and exhibits increased affinity towards α-endosulfan, compared to the wild-type enzyme. Based on these catalytic features the mutant enzyme Phe117Ile was explored for the development of an optical biosensor for α-endosulfan. The enzyme was entrapped in alkosixylane sol-gel system in the presence of two pH indicators (bromocresol purple and phenol red). The sensing signal was based on the inhibition of the sol-gel entrapped GST, with subsequent decrease of released [H+] by the catalytic reaction, measured by sol-gel entrapped indicators. The assay response at 562 nm was linear in the range pH = 4-7. Linear calibration curves were obtained for α-endosulfan in the range of 0-30 μΜ. The reproducibility of the assay response, expressed by relative standard deviation, was in the order of 4.1% (N = 28). The method was successfully applied to the determination of α-endosulfan in real water samples without sample preparation steps.

Assessing interactive mixture toxicity of carbamate and organophosphorus insecticides in the yabby (Cherax destructor)

Carbamate (CB) and organophosphorus (OP) pesticides are commonly detected in aquatic ecosystems and predominantly occur as mixtures of varying complexity. These pesticides inhibit the activity of total cholinesterase (ChE) and thus have the potential to interfere with behaviours that may be essential for the survival of aquatic species. Although the effects of individual ChE insecticides on aquatic species have been reported for decades, the neurotoxicity of mixtures is still poorly understood. This study examined the chronic toxicities of two OP insecticides (chlorpyrifos (CPF) and malathion (MAL)) and one carbamate insecticide (methomyl (METH)) in binary and ternary mixtures on the ChE activity of the yabby (C. destructor). Using the concentration addition approach to estimate mixture toxicity, the observed inhibition of ChE activity caused by all binary mixtures of CPF plus MAL, CPF plus METH and MAL plus METH was additive. In ternary mixtures, all combinations of CPF, MAL and METH were either additive or antagonistic depending on the relative ratios of these chemicals in the mixtures. The effect of mixtures of these three insecticides on C. destructor has not previously been assessed, and the data suggest that individual chemical risk assessments are likely to incorrectly estimate the effect of these insecticides on C. destructor in the aquatic environment where combinations of such chemicals occur.

Advances in Enzyme-Based Biosensors for Pesticide Detection

The intensive use of toxic and remanent pesticides in agriculture has prompted research into novel performant, yet cost-effective and fast analytical tools to control the pesticide residue levels in the environment and food. In this context, biosensors based on enzyme inhibition have been proposed as adequate analytical devices with the added advantage of using the toxicity of pesticides for detection purposes, being more "biologically relevant" than standard chromatographic methods. This review proposes an overview of recent advances in the development of biosensors exploiting the inhibition of cholinesterases, photosynthetic system II, alkaline phosphatase, cytochrome P450A1, peroxidase, tyrosinase, laccase, urease, and aldehyde dehydrogenase. While various strategies have been employed to detect pesticides from different classes (organophosphates, carbamates, dithiocarbamates, triazines, phenylureas, diazines, or phenols), the number of practical applications and the variety of environmental and food samples tested remains limited. Recent advances focus on enhancing the sensitivity and selectivity by using nanomaterials in the sensor assembly and novel mutant enzymes in array-type sensor formats in combination with chemometric methods for data analysis. The progress in the development of solar cells enriched the possibilities for efficient wiring of photosynthetic enzymes on different surfaces, opening new avenues for development of biosensors for photosynthesis-inhibiting herbicides.

Blood cholinesterase activity levels of farmers in winter and hot season of Mae Taeng District, Chiang Mai Province, Thailand

Organophosphate and carbamate pesticides have been widely used by farmers for crop protection and pest control. Inhibition of acetylcholinesterase (AChE) in erythrocyte and butyrylcholinesterase (BChE) in plasma is the predominant toxic effect of organophosphate and carbamate pesticides. Mae Taeng District, Chiang Mai Province, is one of the large areas of growing vegetables and fruits. Due to their regular exposure to these pesticides, the farmers are affected by this toxicity. The objective of the study was to examine the AChE and the BChE activity levels in the blood of 102 farmers for comparison of exposure in two cropping seasons, winter and hot. Blood samples were collected in December 2013 (winter) and April-June 2014 (hot). A total of 102 farmers joined the study, represented by 76 males (74.5 %) and 26 females (25.5 %). The age of most of the farmers was 53.4 ± 8.7 years. Out of 102, 21 farmers used carbamate pesticides. The results showed that the AChE and the BChE activity levels of all the farmers were 3.27 ± 0.84 Unit/mL and 2.15 ± 0.58 Unit/mL, respectively. The AChE and the BChE activity levels in males were 3.31 ± 0.88 Unit/mL and 1.97 ± 0.60 U/mL, respectively, during winter and 3.27 ± 0.82 Unit/mL and 2.15 ± 0.58 U/mL, respectively, during the hot season, and AChE and the BChE activity levels in females were 3.27 ± 0.82 U/mL and 2.44 ± 0.56 U/mL, respectively, during the hot season. The cholinesterase activity levels, both AChE and BChE, in the male farmers' blood had significant difference between the two seasons, while in the case of the female farmers, there was significant difference in the BChE activity levels, at p < 0.05. The BChE activity level was found to significantly correlate with self-spray (p < 0.05), which implies that the BChE activity decreased when they sprayed by themselves. The cholinesterase activity levels of the present study were lower than those of the other studies, which may be an indication of some chronic effect of exposure to anticholinesterase pesticides. Thus, it is recommended that the use of pesticides be decreased, together with increase in the awareness of the impact of pesticides on health; also recommended is regular monitoring of blood cholinesterase.

In search of a comprehensible set of endpoints for the routine monitoring of neurotoxicity in vertebrates: sensory perception and nerve transmission in zebrafish (Danio rerio) embryos

In order to develop a test battery based on a variety of neurological systems in fish, three sensory systems (vision, olfaction, and lateral line) as well as nerve transmission (acetylcholine esterase) were analyzed in zebrafish (Danio rerio) embryos with respect to their suitability as a model for the screening of neurotoxic trace substances in aquatic ecosystems. As a selection of known or putative neurotoxic compounds, amidotrizoic acid, caffeine, cypermethrin, dichlorvos, 2,4-dinitrotoluene, 2,4-dichlorophenol, 4-nonylphenol, perfluorooctanoic acid, and perfluorooctane sulfonic acid were tested in the fish embryo test (OECD test guideline 236) to determine EC₁₀ values, which were then used as maximum test concentration in subsequent neurotoxicity tests. Whereas inhibition of acetylcholinesterase was investigated biochemically both in vivo and in vitro (ex vivo), the sensory organs were studied in vivo by means of fluorescence microscopy and histopathology in 72- or 96-h-old zebrafish embryos, which are not regarded as protected developmental stages in Europe and thus - at least de jure - represent alternative test methods. Various steps of optimization allowed this neurotoxicity battery to identify neurotoxic potentials for five out of the nine compounds: Cypermethrin and dichlorvos could be shown to specifically modulate acetylcholinesterase activity; dichlorvos, 2,4-dichlorophenol, 4-nonylphenol, and perfluorooctane sulfonic acid led to a degeneration of neuromasts, whereas both vision and olfaction proved quite resistant to concentrations ≤ EC₁₀ of all of the model neurotoxicants tested. Comparison of neurotoxic effects on acetylcholinesterase activity following in vivo and in vitro (ex vivo) exposure to cypermethrin provided hints to a specific enzyme-modulating activity of pyrethroid compounds. Enhancement of the neuromast assay by applying a simultaneous double-staining procedure and implementing a 4-scale scoring system (Stengel et al. 2017) led to reduced variability of results and better statistical resolution and allowed to differentiate location-dependent effects in single neuromasts. Since acetylcholinesterase inhibition and neuromast degeneration can be analyzed in 72- and 96-h-old zebrafish embryos exposed to neurotoxicants according to the standard protocol of the fish embryo toxicity test (OECD TG 236), the fish embryo toxicity test can be enhanced to serve as a sensitive neurotoxicity screening test in non-protected stages of vertebrates.

Neonatal, placental, and umbilical cord blood parameters in pregnant women residing in areas with intensive pesticide application

In rural populations, the proximity to areas with intensive pesticide application represents a risk factor of xenobiotic exposure. Here, we investigated whether newborns born to mothers residing in an area with intensive pesticide application show alterations in placental and neonatal morphometric standards, umbilical cord blood (UCB) biochemical parameters, and/or biomarkers related to oxidative stress and oxidative damage. Samples were collected from 151 healthy pregnant women residing in a rural area (rural group; RG) during the pesticide spraying (SS) and nonspraying (NSS) seasons, as well as from women from an urban population (control group; CG), and grouped according to the delivery type (vaginal or cesarean). In the vaginal delivery group, the placental weight and placental index were higher in the RG groups than in the CG (p = 0.01), whereas in the cesarean delivery group, newborn weight was lower in the RG-SS group than in the CG. In the RG-SS group, UCB erythrocyte osmotic fragility and the DNA damage index (DI) were higher, and superoxide dismutase (SOD) activity was lower than in the RG-NSS group. Acetylcholinesterase and SOD activities were found to be inversely correlated with the DI.

Prenatal Residential Proximity to Agricultural Pesticide Use and IQ in 7-Year-Old Children

BACKGROUND

Residential proximity to agricultural pesticide use has been associated with neural tube defects and autism, but more subtle outcomes such as cognition have not been studied.

OBJECTIVES

We evaluated the relationship between prenatal residential proximity to agricultural use of potentially neurotoxic pesticides and neurodevelopment in 7-year-old children.

METHODS

Participants included mothers and children (n=283) living in the agricultural Salinas Valley of California enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. We estimated agricultural pesticide use within 1 km of maternal residences during pregnancy using a geographic information system, residential location, and California’s comprehensive agricultural Pesticide Use Report data. We used regression models to evaluate prenatal residential proximity to agricultural use of five potentially neurotoxic pesticide groups (organophosphates, carbamates, pyrethroids, neonicotinoids, and manganese fungicides) and five individual organophosphates (acephate, chlorpyrifos, diazinon, malathion, and oxydemeton-methyl) and cognition in 7-year-old children. All models included prenatal urinary dialkyl phosphate metabolite concentrations.

RESULTS

We observed a decrease of 2.2 points [95% confidence interval (CI): −3.9, −0.5] in Full-Scale IQ and 2.9 points (95% CI: −4.4, −1.3) in Verbal Comprehension for each standard deviation increase in toxicity-weighted use of organophosphate pesticides. In separate models, we observed similar decrements in Full-Scale IQ with each standard deviation increase of use for two organophosphates (acephate and oxydemeton-methyl) and three neurotoxic pesticide groups (pyrethroids, neonicotinoids, and manganese fungicides).

CONCLUSIONS

This study identified potential relationships between maternal residential proximity to agricultural use of neurotoxic pesticides and poorer neurodevelopment in children. https://doi.org/10.1289/EHP504.

Residential proximity to organophosphate and carbamate pesticide use during pregnancy, poverty during childhood, and cognitive functioning in 10-year-old children

BACKGROUND

Low-income communities and communities of color have been shown to experience disproportionate exposure to agricultural pesticides, which have been linked to poorer neurobehavioral outcomes in infants and children. Few studies have assessed health impacts of pesticide mixtures in the context of socioeconomic adversity.

OBJECTIVES

To examine associations between residential proximity to toxicity-weighted organophosphate (OP) and carbamate pesticide use during pregnancy, household- and neighborhood-level poverty during childhood, and IQ scores in 10-year-old children.

METHODS

We evaluated associations between both nearby agricultural pesticide use and poverty measures and cognitive abilities in 10-year-old children (n = 501) using data from a longitudinal birth cohort study linked with data from the California Pesticide Use Reporting system and the American Community Survey. Associations were assessed using multivariable linear regression.

RESULTS

Children of mothers in the highest quartile compared to the lowest quartile of proximal pesticide use had lower performance on Full Scale IQ [β = -3.0; 95% Confidence Interval (CI) = (-5.6, -0.3)], Perceptual Reasoning [β = -4.0; (-7.6, -0.4)], and Working Memory [β = -2.8; (-5.6, -0.1)]. Belonging to a household earning an income at or below the poverty threshold was associated with approximately two point lower scores on Full Scale IQ, Verbal Comprehension, and Working Memory. Living in the highest quartile of neighborhood poverty at age 10 was associated with approximately four point lower performance on Full Scale IQ, Verbal Comprehension, Perceptual Reasoning, and Working memory.

CONCLUSIONS

Residential proximity to OP and carbamate pesticide use during pregnancy and both household- and neighborhood-level poverty during childhood were independently associated with poorer cognitive functioning in children at 10 years of age.

Acetylcholinesterase in zebrafish embryos as a tool to identify neurotoxic effects in sediments

In order to clarify the suitability of zebrafish (Danio rerio) embryos for the detection of neurotoxic compounds, the acetylcholinesterase assay was adapted and validated with a series of priority pollutants listed as relevant for the European water policy (Aroclor 1254, 2,3-benzofuran, bisphenol A, chlorpyrifos, paraoxon-methyl, quinoline, and methyl mercury chloride) as well as acetonic extracts from three sediments of known contamination. The acute toxicities of the model substances and the sediment extracts were determined by means of the fish embryo test as specified in OECD TG 236, and concentrations as low as the effective concentration at 10% inhibition (EC10) were used as the highest test concentration in the acetylcholinesterase test in order to avoid nonspecific systemic effects mimicking neurotoxicity. Among the model compounds, only the known acetylcholinesterase inhibitors paraoxon-methyl and chlorpyrifos produced a strong inhibition to about 20 and 33%, respectively, of the negative controls. For the sediment extracts, a reduction of acetylcholinesterase activity to about 60% could only be shown for the Vering Canal sediment extracts; this could be correlated to high contents of acetylcholinesterase-inhibiting polycyclic aromatic hydrocarbons (PAHs) as identified by chemical analyses. Co-incubation of the Vering Canal sediment extracts with chlorpyrifos at EC10 concentrations each did not significantly increase the inhibitory effect of chlorpyrifos, indicating that the mode of action of acetylcholinesterase inhibition by the sediment-borne PAHs is different to that of the typical acetylcholinesterase blocker chlorpyrifos. Overall, the study documents that zebrafish embryos represent a suitable model not only to reveal acetylcholinesterase inhibition, but also to investigate various modes of neurotoxic action.

Biosensor technology for pesticides--a review

Pesticides, due to their lucrative outcomes, are majorly implicated in agricultural fields for crop production enhancement. Due to their pest removal properties, pesticides of various classes have been designed to persist in the environment over a longer duration after their application to achieve maximum effectiveness. Apart from their recalcitrant structure and agricultural benefits, pesticides also impose acute toxicological effects onto the other various life forms. Their accumulation in the living system may prove to be detrimental if established in higher concentrations. Thus, their prompt and accurate analysis is a crucial matter of concern. Conventional techniques like chromatographic techniques (HPLC, GC, etc.) used for pesticides detection are associated with various limitations like stumpy sensitivity and efficiency, time consumption, laboriousity, requirement of expensive equipments and highly trained technicians, and many more. So there is a need to recruit the methods which can detect these neurotoxic compounds sensitively, selectively, rapidly, and easily in the field. Present work is a brief review of the pesticide effects, their current usage scenario, permissible limits in various food stuffs and 21st century advancements of biosensor technology for pesticide detection. Due to their exceptional performance capabilities, easiness in operation and on-site working, numerous biosensors have been developed for bio-monitoring of various environmental samples for pesticide evaluation immensely throughout the globe. Till date, based on sensing element (enzyme based, antibody based, etc.) and type of detection method used (Electrochemical, optical, and piezoelectric, etc.), a number of biosensors have been developed for pesticide detection. In present communication, authors have summarized 21st century's approaches of biosensor technology for pesticide detection such as enzyme-based biosensors, immunosensors, aptamers, molecularly imprinted polymers, and biochips technology. Also, the major technological advancements of nanotechnology in the field of biosensor technology are discussed. Various biosensors mentioned in manuscript are found to exhibit storage stability of biocomponent ranging from 30-60 days, detection limit of 10(-6) - 10(-16) M, response time of 1-20 min and applications of developed biosensors in environmental samples (water, food, vegetables, milk, and juice samples, etc.) are also discussed. Researchers all over the globe are working towards the development of different biosensing techniques based on contrast approaches for the detection of pesticides in various environmental samples.

Role of environmental contaminants in the etiology of Alzheimer's disease: a review

Alzheimer's dis ease (AD) is a leading cause of mortality in the developed world with 70% risk attributable to genetics. The remaining 30% of AD risk is hypothesized to include environmental factors and human lifestyle patterns. Environmental factors possibly include inorganic and organic hazards, exposure to toxic metals (aluminium, copper), pesticides (organochlorine and organophosphate insecticides), industrial chemicals (flame retardants) and air pollutants (particulate matter). Long term exposures to these environmental contaminants together with bioaccumulation over an individual's life-time are speculated to induce neuroinflammation and neuropathology paving the way for developing AD. Epidemiologic associations between environmental contaminant exposures and AD are still limited. However, many in vitro and animal studies have identified toxic effects of environmental contaminants at the cellular level, revealing alterations of pathways and metabolisms associated with AD that warrant further investigations. This review provides an overview of in vitro, animal and epidemiological studies on the etiology of AD, highlighting available data supportive of the long hypothesized link between toxic environmental exposures and development of AD pathology.

Pesticide use and cholinesterase inhibition in small-scale agricultural workers in southern Brazil

A controlled cross-sectional study of family growers of fruit and vegetables was conducted between October 2009 and October 2010 to characterize the use of pesticides, establish the socio-demographic profile, and analyze cholinesterase activity in small-scale agricultural workers in Southern Brazil. Data was collected for 173 workers and 179 controls. A structured questionnaire was applied collecting socio-demographic information and determining knowledge and work practices in relation to pesticide use. The benchmarks for total cholinesterase (ChEs) and butyrylcholinesterase (BuChE) were obtained from the average enzymatic activity of the occupationally unexposed group (control). The mean age of the exposed population was 40.0 ± 11.2 years. The symptoms differed significantly (p<0.05) between the exposed and unexposed populations. Forty (23.1%) workers showed symptoms associated with exposure to pesticides. The average value of enzymatic activity in the occupationally unexposed group for ChEs was 6.3 μmol/mL/min among males and 5.6 μmol/mL/min among females while for BuChE was 2.4 μmol/mL/min among males and 2.0 μmol/mL/min among females. Eight (4.6%) workers had high inhibition (>30%) of ChEs activity, whereas no workers showed high inhibition (>50%) of BuChE. Potential factors involved include gender, education, pesticide orientation, exposure, and hygiene measures.

Piezoelectric biosensors for organophosphate and carbamate pesticides: a review

Due to the great amount of pesticides currently being used, there is an increased interest for developing biosensors for their detection. Among all the physical transducers, piezoelectric systems have emerged as the most attractive due to their simplicity, low instrumentation costs, possibility for real-time and label-free detection and generally high sensitivity. This paper presents an overview of biosensors based on the quartz crystal microbalance, which have been reported in the literature for organophosphate and carbamate pesticide analysis.

Effect of diffusion limitations on multianalyte determination from biased biosensor response

The optimization-based quantitative determination of multianalyte concentrations from biased biosensor responses is investigated under internal and external diffusion-limited conditions. A computational model of a biocatalytic amperometric biosensor utilizing a mono-enzyme-catalyzed (nonspecific) competitive conversion of two substrates was used to generate pseudo-experimental responses to mixtures of compounds. The influence of possible perturbations of the biosensor signal, due to a white noise- and temperature-induced trend, on the precision of the concentration determination has been investigated for different configurations of the biosensor operation. The optimization method was found to be suitable and accurate enough for the quantitative determination of the concentrations of the compounds from a given biosensor transient response. The computational experiments showed a complex dependence of the precision of the concentration estimation on the relative thickness of the outer diffusion layer, as well as on whether the biosensor operates under diffusion- or kinetics-limited conditions. When the biosensor response is affected by the induced exponential trend, the duration of the biosensor action can be optimized for increasing the accuracy of the quantitative analysis.

An acetylcholinesterase-based chronoamperometric biosensor for fast and reliable assay of nerve agents

The enzyme acetylcholinesterase (AChE) is an important part of cholinergic nervous system, where it stops neurotransmission by hydrolysis of the neurotransmitter acetylcholine. It is sensitive to inhibition by organophosphate and carbamate insecticides, some Alzheimer disease drugs, secondary metabolites such as aflatoxins and nerve agents used in chemical warfare. When immobilized on a sensor (physico-chemical transducer), it can be used for assay of these inhibitors. In the experiments described herein, an AChE- based electrochemical biosensor using screen printed electrode systems was prepared. The biosensor was used for assay of nerve agents such as sarin, soman, tabun and VX. The limits of detection achieved in a measuring protocol lasting ten minutes were 7.41 × 10⁻¹² mol/L for sarin, 6.31 × 10⁻¹² mol/L for soman, 6.17 × 10⁻¹¹ mol/L for tabun, and 2.19 × 10⁻¹¹ mol/L for VX, respectively. The assay was reliable, with minor interferences caused by the organic solvents ethanol, methanol, isopropanol and acetonitrile. Isopropanol was chosen as suitable medium for processing lipophilic samples.