Search

Endocrine disruptors chemicals (EDCs) pose significant health risks, including cancer, behavioral disorders, and infertility. In this study, we employed the photoelectrocatalysis (PEC) technique with optimized tungsten oxide (WO 3 ) nanostructures as a photoanode to degrade three diverse EDCs: methiocarb, dimethyl phthalate, and 4-tert-butylphenol. PEC degradation tests were carried out for individual contaminants and a mixture of them, assessing efficiency across different EDC families. Ultra High-Performance Liquid Chromatography and Mass Spectrometry was used to control the course of the experiments. For individual solutions, 4-tert-butylphenol and methiocarb were 100% degraded at 1 hour of PEC degradation. Among the tested EDCs, dimethyl phthalate showed the highest resistance to degradation when treated individually. However, when assessed in a mixture with the other EDCs, the degradation efficiency of dimethyl phthalate increased compared to its individual treatment. Furthermore, four degradation intermediates were identified for each contaminant. Finally, toxicity tests revealed that the initial solution was more toxic than the samples treated for all the contaminants tested, except for the phthalate., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The increasing use of pesticides in the agriculture fields strengthen the crop production to meet the needs of increasing population. The residues in water and food materials cause several health hazards. Herein, nitrogen-doped carbon quantum dot (N-CQDs) is designed for determination of methiocarb pesticide in vegetables by fluorescent paper sensor and compared the results with fluorimetry. The fluorescent paper-based detection is performed by recording the change in fluorescence of N-CQDs with introduction of methiocarb using smartphone and ImageJ software. Good linear range was acquired for analysis of methiocarb from 10 to 1000 μgL -1 with a low detection limit (LOD) of 3.5 μgL -1 in fluorimetry; and 700-10,000 μgL -1 with a LOD of 500 μgL -1 in fluorescent paper sensor. A better recovery from 92.0 to 95.4% illustrating the selectivity of both methods for analysis of methiocarb in vegetables. Thus, the advantage of using N-CQDs as a fluorescent sensor for analysis of methiocarb in vegetables is instrument free, portable and user-friendly., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Despite the high toxicity and resistance to conventional water treatments exhibited by methiocarb (MC), there are no reports regarding the degradation of this priority pesticide by means of alternative purification technologies. In this work, the removal of MC by means of ozonation was studied for the first time, employing a multi-reactor methodology and neutral pH conditions. The second-order rate constants of MC reaction with molecular ozone (O 3 ) and formed hydroxyl radicals (OH·) were determined to be 1.7·10 6 and 8.2·10 9  M -1  s -1 , respectively. During degradation experiments, direct ozone reaction was observed to effectively remove MC, but not its formed intermediates, whereas OH· could oxidize all species. The major identified TPs were methiocarb sulfoxide (MCX), methiocarb sulfoxide phenol (MCXP) and methiocarb sulfone phenol (MCNP), all of them formed through MC oxidation by O 3 or OH· in combination with hydrolysis. A toxicity assessment evidenced a strong dependence on MCX concentration, even at very low values. Despite the OH· capability to degrade MC and its main metabolites, the relative resistance of TPs towards ozone attack enlarged the oxidant dosage (2.5 mg O 3 /mg DOC) necessary to achieve a relatively low toxicity of the medium. Even though ozonation could be a suitable technique for MC removal from water compartments, strategies aimed to further promote the indirect contribution of hydroxyl radicals during this process should be explored., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A simultaneous analytical method was developed for the determination of methiocarb and its metabolites, methiocarb sulfoxide and methiocarb sulfone, in five livestock products (chicken, pork, beef, table egg, and milk) using liquid chromatography-tandem mass spectrometry. Due to the rapid degradation of methiocarb and its metabolites, a quick sample preparation method was developed using acetonitrile and salts followed by purification via dispersive- solid phase extraction (d-SPE). Seven-point calibration curves were constructed separately in each matrix, and good linearity was observed in each matrix-matched calibration curve with a coefficient of determination (R 2 ) ≥ 0.991. The limits of detection and quantification were 0.0016 and 0.005mg/kg, respectively, for all tested analytes in various matrices. The method was validated in triplicate at three fortification levels (equivalent to 1, 2, and 10 times the limit of quantification) with a recovery rate ranging between 76.4-118.0% and a relative standard deviation≤10.0%. The developed method was successfully applied to market samples, and no residues of methiocarb and/or its metabolites were observed in the tested samples. In sum, this method can be applied for the routine analysis of methiocarb and its metabolites in foods of animal origins., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this work, we examined the metabolism of the carbamate insecticides methiocarb and carbaryl by rat liver microsomes and plasma, and its effect on their endocrine-disrupting activities. Methiocarb and carbaryl were not enzymatically hydrolyzed by rat liver microsomes, but were hydrolyzed by rat plasma, mainly to methylthio-3,5-xylenol (MX) and 1-naphthol, respectively. When methiocarb was incubated with rat liver microsomes in the presence of NADPH, methiocarb sulfoxide was formed. The hydrolysis product, MX, was also oxidized to the sulfoxide, 3,5-dimethyl-4-(methylsulfinyl)phenol (SP), by rat liver microsomes in the presence of NADPH. These oxidase activities were catalyzed by cytochrome P450 and flavin-containing monooxygenase. Methiocarb and carbaryl both exhibited estrogen receptor α (ERα) and ERβ agonistic activity. MX and 1-naphthol showed similar activities, but methiocarb sulfoxide and SP showed markedly decreased activities. On the other hand, methiocarb and carbaryl exhibited potent antiandrogenic activity in the concentration range of 1×10(-6)-3×10(-5) M. Their hydrolysis products, MX, and 1-naphthol also showed high activity, equivalent to that of flutamide. However, methiocarb sulfoxide and SP showed relatively low activity. Thus, hydrolysis of methiocarb and carbaryl and oxidation of methiocarb to the sulfoxide markedly modified the estrogenic and antiandrogenic activities of methiocarb and carbaryl., (Copyright © 2016. Published by Elsevier B.V.)

The micropollution of drinking water sources with pesticides has become a global concern. This work investigated the degradation of methiocarb (MC), a most commonly-used carbamate pesticide, by monochloramine (NH2Cl) under simulated water treatment conditions. Results indicate that the reaction was of first-order in MC and varied orders in NH2Cl depending on water pH. The observed rate constant of MC degradation decreased quickly with either a decrease in the molar ratio of chlorine to ammonia (Cl2:N) or an increase in water pH. The apparent activation energy of the reaction was determined to be 34 kJ mol(-1). The MC degradation pathways also exhibited a strong pH dependence: at pH 6.5, MC was first oxidized by NH2Cl to methiocarb sulfoxide (MCX), and then hydrolyzed to methiocarb sulfoxide phenol (MCXP); while at pH 8.5, MCX, MCXP and methiocarb sulfone phenol (MCNP) were formed successively through either oxidation or hydrolysis reactions. Based on the identified byproducts and their concentrations evolution, the proposed pathways of MC degradation in the presence of NH2Cl were further validated through kinetic model simulations., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The western flower thrips, Frankliniella occidentalis (Pergande), is a serious pest in the south-east of Spain owing to its direct feeding on crops, transmission of the tomato spotted wilt virus and its very high level of resistance to insecticides. Mechanisms of resistance were examined using field populations of F. occidentalis with different susceptibilities to acrinathrin, methiocarb (selective insecticides), endosulfan, metamidophos and deltamethrin (broad-spectrum insecticides). Esterase activity towards alpha-naphthyl acetate and p-nitrophenyl acetate in resistant strains was significantly higher than in the reference strain (MLFOM) for both model substrates. This higher activity was significantly correlated with acrinathrin and methiocarb resistance., (Copyright 2006 Society of Chemical Industry.)

Biochemical mechanisms associated with methiocarb resistance were examined in laboratory-selected and field populations of the western flower thrips, Frankliniella occidentalis (Pergande). Seven populations were examined and they differed in their susceptibility to methiocarb by 30 times. Including the synergists piperonyl butoxide, a cytochrome P-450 monooxygenase inhibitor, or S,S,S-tributylphosphorotrithioate, an esterase inhibitor, in the methiocarb bioassays partially suppressed resistance in the most resistant populations. In vitro assays of general esterase, glutathione S-transferase, and acetylcholinesterase activities showed increased activity in some of the resistant populations and increased activity of the enzymes after methiocarb selection on one of the populations. Assays of acetylcholinesterase sensitivity to inhibition by methiocarb, dichlorvos, and eserine suggested insensitive acetylcholinesterase in two of the resistant populations. These results indicate that methiocarb resistance in F. occidentalis was polyfactorial and involved detoxification and altered target site. None of the biochemical assays showed interpopulation enzymatic differences strongly correlated with the level of methiocarb resistance. The possibilities for developing rapid biochemical diagnostic assays to detect methiocarb resistance in F. occidentalis are discussed.

The fact that Frankliniella occidentalis (Thysanoptera: Thripidae) completes its life cycle in a short time reveals the need for continuous pest control. Therefore, pest resistance may occur with the intensive use of chemicals by the growers. In this context, the current sensitivity of F. occidentalis to registered insecticides for carnation (methiocarb, formetanate hydrochloride), registered insecticides for vegetables (azadirachtin, malathion, and spinosad), and unapproved insecticides used extensively by growers needs to be determined. Moreover, it is important to test the chemicals (for example, pyridalyl) used against other pests whose spray period is the same as F. occidentalis. In this study, it was aimed to determine the sensitivity levels of F. occidentalis populations taken from the sites of intensive carnation production in Antalya province in 2018-2020 to these chemicals by the leaf dipping method. As a result of the study, resistance against spinosad (11.00-28.60 times), methiocarb (2.10-2.70 times), malathion (2.05-4.21 times), azadirachtin (3.00-7.00 times), formetanate hydrochloride (1.50-2.00 times) and pyridalyl (2.75-3.89 times) were determined. Given the high resistance to spinosad observed in the study, trials involving the combination of spinosad and formetanate hydrochloride were initiated as a strategy for managing resistance. The resistance against spinosad + formetanate hydrochloride was determined between 4.35 and 9.09 times. Our results suggest that resistance level can be reduced by using resistance management methods such as the use of mixed chemicals, although resistance was detected in all five locations against all active substances. [ABSTRACT FROM AUTHOR]

Pesticides are environmental contaminants of great interest because of their toxicity, persistence in the environment and bio-accumulative nature. However, there is a scarcity of literature concerning human exposure to pesticides through the consumption of contaminated drinking water. This study investigates the levels of multiple pesticides in drinking water and their subsequent carcinogenic and non-carcinogenic risk in five selected districts (Peshawar basin) of Khyber Pakhtunkhwa-Pakistan, to understand the exact scenario of pesticide toxicity in the sources of drinking water. The water samples were extracted by liquid–liquid extraction and analyzed using gas chromatography mass spectrometry (GCMS). Results obtained indicated that the detected concentrations of ∑21 pesticides ranged between 0 and 883.7 µg L−1 in the study area. The highest concentration was detected for methiocarb (mean 5.30 µg L−1), followed by acetamiprid (0.90 µg L−1), while the lowest was observed for cyhalothrin (0.01 µg L−1). The highest concentration of EU Watch List of Contaminants of Emerging Concern (methiocarb and acetamiprid) in the study area is alarming. Most of the pesticide residues recorded in the water samples exceeded the maximum residue limits except for dieldrin and cyhalothrin. Whereas, the residues of aldicarb, carbofuran deg, carbofuran, atrazine, alpha endosulfan, beta endosulfan, cypermethrin-1, difenoconazol-I and difenoconazol-II were not observed in any of the collected samples. The incremental lifetime cancer risk of endocrine disruptors such as dieldrin, o,p′ DDT, o,p′ DDD, and p,p′ DDE was > 10–6, posing potentially serious carcinogenic risk to the local inhabitants. Whereas, the non-carcinogenic risk through pesticide exposure was negligible, suggesting no/little risk to the inhabitants from these chemicals in drinking water. Regular monitoring is needed to evaluate pesticide concentrations not only in drinking water sources but also in soil and food crops as they pose serious eco-toxicological risks. [ABSTRACT FROM AUTHOR]

Present work reports preparation of colloidal single/few layer Ti 3 C 2 T x MXene flakes using minimally intensive layer delamination (MILD) method for rapid electroanalytical screening of carbamate pesticides. Lithium fluoride salt and hydrochloric acid (7.5 M LiF/9M HCl) was used to produce in-situ generated HF as etchant to remove Al successfully from Ti 3 AlC 2 MAX phase. Unlike the clay method (5 M LiF/6M HCl), this methodology simplified Ti 3 C 2 T x synthesis protocol resulting in Li+ ions intercalated Ti 3 C 2 T x which was delaminated without further sonication. The delaminated Ti 3 C 2 T x flakes were found to be single/few layered sheets with mostly –OH and –O terminated surface groups. The characteristic 002 peak observed in X-ray diffraction (XRD) at 2θ = 6.4° with interplaner distance of 1.1137 nm suggested broadening of the peak attributed to the presence of Li+ ions between Ti 3 C 2 T x flakes. Delaminated Ti 3 C 2 T x flakes were utilized as working electrode which demonstrated simultaneous and selective detection of carbamate pesticides methiocarb and diethofencarb by voltammetry. The oxidation peaks of the two pesticides were well separated by a potential difference of 0.35 V in 0.5 M H 2 SO 4 and DPV detection limits were calculated as 0.19 μg mL−1 and 0.46 μg mL−1 for methiocarb and diethofencarb respectively. Ti 3 C 2 T x flakes as electrochemical sensor exhibited long term stability and acceptable recoveries in real sample for environmental applications. [ABSTRACT FROM AUTHOR]

Systemic insecticides such as neonicotinoids are widely used in seed coating practices for pest control in many crops, e.g., corn. Their success is due to their ability to protect the whole plant, from the roots to the upper leaves, but their use at high amounts is causing possible adverse effects on non-target animals exposed to contaminated pollen, nectar, leaves, and dust emitted during sowing. In 2018, the European Union banned some neonicotinoids and fipronil as seed coating insecticides in open fields. Consequently, the methylcarbamate methiocarb and less-toxic neonicotinoids, e.g., thiacloprid, have been authorized and largely used as alternative pesticides for corn seed coating. Here, an analytical protocol based on QuEChERS extraction/purification procedure and analysis by liquid chromatography-mass spectrometry has been optimized for the identification and the quantification of methiocarb, thiamethoxam, thiacloprid, and their metabolites in guttation drops, the xylem fluid excreted at leaf margins, and in leaves of corn plants grown from coated seeds. Although methiocarb is a non-systemic pesticide, we unexpectedly found high concentrations of its metabolites in both guttations and leaves, whereas methiocarb itself was below detection limits in most of the samples. The methiocarb main metabolite, methiocarb sulfoxide, was found at a mean concentration of 0.61 ± 1.12 µg mL−1 in guttation drops and 4.4 ± 2.1 µg g−1 in leaves. Conversely, parent compounds of neonicotinoids (thiamethoxam, thiacloprid) are systemically distributed in corn seedlings. This result raises safety concerns given that methiocarb sulfoxide is more toxic than the parent compound for some non-target species. [ABSTRACT FROM AUTHOR]

The ecotoxicity of methiocarb aqueous solutions treated by electrochemical oxidation was evaluated utilizing the model organism Daphnia magna. The electrodegradation experiments were performed using a boron-doped diamond anode and the influence of the applied current density and the supporting electrolyte (NaCl or Na2SO4) on methiocarb degradation and toxicity reduction were assessed. Electrooxidation treatment presented a remarkable efficiency in methiocarb complete degradation and a high potential for reducing the undesirable ecological effects of this priority substance. The reaction rate followed first-order kinetics in both electrolytes, being more favorable in a chloride medium. In fact, the presence of chloride increased the methiocarb removal rate and toxicity reduction and favored nitrogen removal. A 200× reduction in the acute toxicity towards D. magna, from 370.9 to 1.6 toxic units, was observed for the solutions prepared with NaCl after 5 h treatment at 100 A m−2. An increase in the applied current density led to an increase in toxicity towards D. magna of the treated solutions. At optimized experimental conditions, electrooxidation offers a suitable solution for the treatment and elimination of undesirable ecological effects of methiocarb contaminated industrial or agricultural wastewaters, ensuring that this highly hazardous pesticide is not transferred to the aquatic environment. [ABSTRACT FROM AUTHOR]

Cold plasma technology is an advanced oxidation process (AOP), which has shown significant potential for pesticide degradation. The aim of this study was to determine the degradation efficacy and transformation products for cold plasma treated carbamates in water. The dissipation of three carbamates, namely, carbaryl, methiocarb and aminocarb were evaluated as a function of treatment voltage (70, 80, and 90 kV) and duration (1 to 5 min) using a dielectric barrier discharge. Significant and rapid reduction in the concentrations of carbaryl, methiocarb and aminocarb were observed after cold plasma treatment. A maximum degradation of 50.5% in carbaryl, 99.6% in methiocarb and 99.3% in aminocarb was achieved after 5 min of treatment at an applied voltage of 90 kV. The plasma light emission was evaluated using optical emission spectroscopy revealing the production of reactive oxygen and nitrogen species, besides gas temperatures closer to ambient. The reaction intermediates were identified mostly as oxidation products from the respective carbamates, and reaction pathways were proposed. The toxicity of the degradation products, where available, was reviewed. Overall, this study shows the potential of cold plasma technology as an alternative approach for rapid dissipation of agrochemicals and other micro-pollutants in water and wastewater. [ABSTRACT FROM AUTHOR]

Background: Large amounts of insecticide-containing dusts produced from abrasion of the seed dressing can be released into the atmosphere during sowing operations. Neonicotinoid pesticides, introduced in the 1990s for several crops, are the leading products for seed-coating treatments in many countries. Neonicotinoid containing dusts can be effectively intercepted by bees in flight over the sowing field, inducing lethal acute effects, so that restrictions in the use of the main neonicotinoids have been adopted in the European Union. This led to the consequent introduction of replacement insecticides for seed-coating, i.e. methiocarb and thiacloprid, despite the lack of information on both the toxicity and the exposure scenarios for honeybees. Results: In this study, a laboratory apparatus was developed in order to quantify the toxicity of the dusts produced from the abrasion of the seed coating. This quantification is based on (i) an airstream transporting coating particles into an exposure chamber; (ii) exposure of bees to reproducible and measurable concentrations of insecticide, and (iii) direct measurement of the exposure dose on single bees. The method allowed us to perform in vivo experiments of honeybee exposure to provide toxicity data in more realistic exposure conditions. In fact, the formulation rather than the active principle alone can be tested, and the exposure is through dusts rather than a solution so that specific absorption behavior can be studied in representative environmental conditions. The method was used to quantify the acute toxicity (LD50) of dusts obtained from the abrasion of corn seeds coated with clothianidin, thiacloprid and methiocarb. Conclusions: Our results show that, surprisingly, the replacement insecticide methiocarb has a toxicity (LD50 = 421–693 ng/bee) in the same order of magnitude as clothianidin (LD50 = 113–451 ng/bee) through this specific exposure route, while thiacloprid (LD50 = 16.9·103 ng/bee) has a significantly lower acute toxicity. Moreover, dusts containing methiocarb and clothianidin show a significant increase in toxicity when, after exposure, bees are kept under high humidity conditions. This suggests that the method here presented can be used to obtain complementary toxicity data in the risk assessment procedure for the authorization of new seed-coating insecticides or new formulations. [ABSTRACT FROM AUTHOR]

Background: There has been a rising interest within the scientific community and the public about the environmental risk related to the abundance of microplastics in aquatic environments. Up to now, however, scientific knowledge in this context has been scarce and insufficient for a reliable risk assessment. To remedy this scarcity of data, we investigated possible adverse effects of polystyrene particles (104 particles/L) and the pesticide methiocarb (1 mg/L) in juvenile brown trout (Salmo trutta f. fario) both by themselves as well as in combination after a 96 h laboratory exposure. PS beads (density 1.05 g/mL) were cryogenically milled and fractionated resulting in irregular-shaped particles (< 50 µm). Besides body weight of the animals, biomarkers for proteotoxicity (stress protein family Hsp70), oxidative stress (superoxide dismutase, lipid peroxidation), and neurotoxicity (acetylcholinesterase, carboxylesterases) were analyzed. As an indicator of overall health, histopathological effects were studied in liver and gills of exposed fish. Results: Polystyrene particles by themselves did not influence any of the investigated biomarkers. In contrast, the exposure to methiocarb led to a significant reduction of the activity of acetylcholinesterase and the two carboxylesterases. Moreover, the tissue integrity of liver and gills was impaired by the pesticide. Body weight, the oxidative stress and the stress protein levels were not influenced by methiocarb. Effects caused by co-exposure of polystyrene microplastics and methiocarb were the same as those caused by methiocarb alone. Conclusions: Overall, methiocarb led to negative effects in juvenile brown trout. In contrast, polystyrene microplastics in the tested concentration did not affect the health of juvenile brown trout and did not modulate the toxicity of methiocarb in this fish species. [ABSTRACT FROM AUTHOR]

Bird repellents to protect seeds are a potentially important aspect of integrated vertebrate pest management strategies. Yet, there currently are no repellents registered for seed treatment uses. This is due not to lack of effective candidate compounds, but to monetary and regulatory constraints that inhibit commercialization of promising compounds. Two examples of this dilemma are methiocarb and anthraquinone, each of which has considerable potential for bird repellent uses and each of which faces considerable registration hurdles as prospective seed treatment compounds. A concerted, coordinated effort among private industry, producer groups, and state and federal agencies may be the best strategy to bring potentially useful repellents to commercial reality.

The ecotoxicity of methiocarb aqueous solutions treated by electrochemical oxidation was evaluated utilizing the model organism Daphnia magna. The electrodegradation experiments were performed using a boron-doped diamond anode and the influence of the applied current density and the supporting electrolyte (NaCl or Na2SO4) on methiocarb degradation and toxicity reduction were assessed. Electrooxidation treatment presented a remarkable efficiency in methiocarb complete degradation and a high potential for reducing the undesirable ecological effects of this priority substance. The reaction rate followed first-order kinetics in both electrolytes, being more favorable in a chloride medium. In fact, the presence of chloride increased the methiocarb removal rate and toxicity reduction and favored nitrogen removal. A 200× reduction in the acute toxicity towards D. magna, from 370.9 to 1.6 toxic units, was observed for the solutions prepared with NaCl after 5 h treatment at 100 A m−2. An increase in the applied current density led to an increase in toxicity towards D. magna of the treated solutions. At optimized experimental conditions, electrooxidation offers a suitable solution for the treatment and elimination of undesirable ecological effects of methiocarb contaminated industrial or agricultural wastewaters, ensuring that this highly hazardous pesticide is not transferred to the aquatic environment.

Abstract The conclusions of EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State the United Kingdom and co‐rapporteur Member State Germany for the pesticide active substance methiocarb are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative use of methiocarb as an insecticide and a bird repellent on maize. The reliable end points, appropriate for use in regulatory risk assessment, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.

Repellents substances and devices cause pest species to avoid otherwise attractive or palatable materials. For birds, repellents can be visual, auditory, pyrotechnic, tactile, chemosensory, physiologic, or physical. Here, we consider chemical agents only. Few substances are registered with the U.S. Environmental Protection Agency (EPA), and thus legally available for use. This lack of available bird repellent technology reflects the small demonstrable economic impact of many agricultural bird damage problems. Accurate information about damage and market size is virtually nonexistent, and private companies are reluctant to invest resources in the unknown. To successfully commercialize new repellents, clearly lucrative markets must be identified. Efforts must be made to empirically quantify damage and to estimate whether control methods are economical relative to the protection that they confer. We intend the present manuscript as a first step in these directions.

Molecular descriptors (including quantum chemical, topological and physicochemical descriptors) were calculated for five m-tolyl derivatives insecticides [namely, carbosulfan (CBS), carbofuran (CBF), isoprocab (IFP), methiocarb (MTC) and isocarbophos (ICP)]. Calculated quantum chemical parameters included the total energy, the electronic energy, the binding energy, the core-core repulsion energy, the heat of formation, the dipole moment and the frontier molecular orbital energies. All the calculated quantum chemical parameters (except dipole moment) exhibited strong correlation with the experimental LD values of the studied insecticides (at various Hamiltonians). Calculated topological parameters included the molecular topological index (MTI), polar surface area (PSA), total connectivity (TC), total valence connectivity (TVC), Wiener index (WI), topological diameter (TD) and Balaban index (BI). However, only MTI, PSA, WI and BI exhibited excellent correlation with the toxicological activity of the insecticides. Also among all the calculated physicochemical parameters [logP, surface area (SA), surface volume (SV), hydration energy (E), polarizability (PLZ) and refractivity (RFT)], only SV, E, PLZ and RFT were useful in establishing quantitative structure activity relationship (QSAR). Application of QSAR indicated that the calculated theoretical LD values for the studied insecticides displayed excellent correlation with experimentally derived LD values. However, best results were obtained from quantum chemical descriptors under modified neglect of atomic overlap (MNDO). The toxicity profile of the insecticides also correlated strongly with ionization energy, electron affinity, global softness and global harness. Reactive sites of each of the insecticides were established using Fukui function, Huckel charges and HOMO/LUMO diagrams. Six new molecules were proposed and their theoretical activities were estimated. The proposed molecules included 2-methyl-2-(methylthio)-2,3-dihydrobenzofuran-7-yl methylcarbamate, O-methyl O-2-((methylaminooxy)carbonyl)phenyl phosphoramidothioate, 2-((methylaminooxy)carbonyl)phenyl methylcarbamate, 2-(1-(methylthio)ethyl)phenyl methylcarbamate, N-methyl- O-(2-(methylthiooxy) benzoyl) hydroxyl amine and 4-methyl naphthalen-2-yl methylcarbamate. Some of the proposed molecules exhibited negative values of LD (indicating extreme toxicity) while two of them exhibited values that are comparable to existing insecticides. [ABSTRACT FROM AUTHOR]

This paper describes a simple and low-cost test strip for on-site monitoring of methiocarb insecticide. Hydrophilic filter paper soaked in agarose solution was bounded by hydrophobic solid wax and then was coated with unmodified gold nanoparticles (AuNPs). AuNPs aggregation caused by methiocarb served as colorimetric response. We demonstrated detection capability of methiocarb both in solution- and substrate-based sensor. A good linear relationship was obtained between the colorimetric response and the concentration of methiocarb ranging from 20 to 80 ng mL ^-1 with a limit of detection of 5 ng mL ^-1 . Excellent selectivity toward methiocarb was observed among various pesticides and cationic and anionic ions. Furthermore, the proposed assay could successfully detect methiocarb in paddy and tap water with satisfactory results. It would be of interest for use as rapid, portable, and technically simple test strip in water quality monitoring. [ABSTRACT FROM PUBLISHER]

• Immobilisation of human FMO1 on glassy carbon electrode with cation surfactant DDAB. • Contact angle and AFM surface measurements of graphene oxide-DDAB. • Enhanced electrochemical signal of FMO1 in presence of graphene oxide. • FMO1 bioelectrode activity towards pesticides; phorate, methiocarb and fenthion. • Successful tandem oxidation of phorate with FMO1 and CYP3A4 bioelectrodes. It is highly advantageous to devise an in vitro platform that can predict the complexity of an in vivo system. The first step of this process is the identification of a xenobiotic whose monooxygenation is carried out by two sequential enzymatic reactions. Pesticides are a good model for this type of tandem reactions since in specific cases they are initially metabolised by human flavin-containing monooxygenase 1 (hFMO1), followed by cytochrome P450 (CYP). To assess the feasibility of such an in vitro platform, hFMO1 is immobilised on glassy carbon electrodes modified with graphene oxide (GO) and cationic surfactant didecyldimethylammonium bromide (DDAB). UV–vis, contact angle and AFM measurements support the effective decoration of the GO sheets by DDAB which appear as 3 nm thick structures. hFMO1 activity on the bioelectrode versus three pesticides; fenthion, methiocarb and phorate, lead to the expected sulfoxide products with K M values of 29.5 ± 5.1, 38.4 ± 7.5, 29.6 ± 4.1 µM, respectively. Moreover, phorate is subsequently tested in a tandem system with hFMO1 and CYP3A4 resulting in both phorate sulfoxide as well as phoratoxon sulfoxide. The data demonstrate the feasibility of using bioelectrochemical platforms to mimic the complex metabolic reactions of xenobiotics within the human body. [ABSTRACT FROM AUTHOR]

The overuse of pesticides to increase essential food production adversely affects the environment and human health. Methiocarb (MTC) is the most effective insecticide (acaricide) for controlling mollusks in soil and plants. However, MTC has poisoning effects on non-targeted living organisms and soil. Therefore, MTC monitoring in soil and water samples is necessary to mitigate its poisoning effect on living organisms. In this study, we explored novel architectures of barium vanadate multi-layered graphene (BaV 2 O 6 -ML-Gr) nanocomposites as highly selective and sensitive electrodes for MTC detection. These materials were synthesized using a facile precipitation method and ultrasonication. They were then utilized as electrode matrices for the electrochemical quantification of MTC in environmental samples. Subsequently, the electrochemical performance of the BaV 2 O 6 -ML-Gr/screen-printed carbon electrode (SPCE) was evaluated using differential pulse voltammetry, which revealed a high sensitivity of 1.0805 µA/(µM−1 cm−2) with a low detection limit of 8 nM and an adequate linear response of 0.01–64.9 µM. The real-time quantification of MTC using BaV 2 O 6 -ML-Gr/SPCE was conducted with different soil and water samples, which provided acceptable recovery results for MTC. The results showed that BaV 2 O 6 -ML-Gr/SPCE can be used for the on-site electrochemical analysis of MTC. • We prepared a BaV 2 O 6 -ML-Gr nanocomposite via co-precipitation and sonication. • Novel architecture BaV 2 O 6 -ML-Gr/SPCE was used for electrochemical detection of MTC. • BaV 2 O 6 -ML-Gr/SPCE exhibits an adequate linear range and lower LOD. • The BaV 2 O 6 -ML-Gr/SPCE provides an excellent sensing ability to the MTC in different soil and water samples. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Polonorum. Agricultura is the property of University of Technology & Life Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The oxidative, reductive, and hydrolytic metabolism of methiocarb and the hydrolytic metabolism of carbaryl by liver microsomes and plasma of rats or humans were examined. The effects of the metabolism of methiocarb and carbaryl on their nuclear receptor activities were also examined. When methiocarb was incubated with rat liver microsomes in the presence of NADPH, methiocarb sulfoxide, and a novel metabolite, methiocarb sulfone were detected. Methiocarb sulfoxide was oxidized to the sulfone by liver microsomes and reduced back to methiocarb by liver cytosol. Thus, the interconversion between methiocarb and the sulfoxide was found to be a new metabolic pathway for methiocarb by liver microsomes. The product of methiocarb hydrolysis, which is methylthio-3,5-xylenol (MX), was also oxidized to sulfoxide form by rat liver microsomes. The oxidations were catalyzed by human flavincontaining monooxygenase isoform (FMO1). CYP2C19, which is a human cytochrome P450 (CYP) isoform, catalyzed the sulfoxidations of methiocarb and MX, while CYP1A2 also exhibited oxidase activity toward MX. Methiocarb and carbaryl were not enzymatically hydrolyzed by the liver microsomes, but they were mainly hydrolyzed by plasma and albumin to MX and 1-naphthol, respectively. Both methiocarb and carbaryl exhibited PXR and PPARa agonistic activities; however, methiocarb sulfoxide and sulfone showed markedly reduced activities. In fact, when methiocarb was incubated with liver microsomes, the receptor activities were decreased. In contrast, MX and 1-naphthol showed nuclear receptor activities equivalent to those of their parent carbamates. Thus, the hydrolysis of methiocarb and carbaryl and the oxidation of methiocarb markedly modified their nuclear receptor activities. [ABSTRACT FROM AUTHOR]

The application of molluscicides baits on the soil surface is the most common practice to control terrestrial gastropods. There seems to be a gap in the accurate evaluation of molluscicidal baits effects to soil arthropods, since their hazard to non-target organisms has been considered low after mixing baits into soil. In this work the ecotoxicological effects of two molluscicide baits (metaldehyde and methiocarb) to the collembolan Folsomia candida were evaluated using two different approaches: (1) molluscicidal baits were applied to the top soil once and only at the beginning of the exposure and avoidance behaviour and reproduction were evaluated; and (2) baits were replaced by new ones after 14-d of exposure, simulating the recommended application rate recommended by the manufacturer and reproduction was assessed (repeated/pulse exposure). A preference for the side contaminated for methiocarb was observed but the distribution of collembolans in the avoidance test with metaldehyde was random. Exposure to metaldehyde resulted in a significant increase in mortality. For methiocarb, a reduction in the juveniles produced but no acute effects were observed. In the bait pulse test, the toxic effects of each chemical was significantly increased compared with the single exposure test, for all treatments used (both reproduction and mortality). In summary, molluscicides have an adverse effect on F. candida , with severe effects on their behaviour (only for methiocarb), reproduction and survival (for both), which can lead to population collapse with time. [ABSTRACT FROM AUTHOR]

A two-part review is presented relating historical tests of the toxicity of pesticides toTyphlodromus pyriand their relevance to modern pest management in New Zealand pome-fruit orchards. Over the past 30 years, the initial need forT. pyrito be resistant to broad-spectrum pesticides has substantially declined as a growing array of new selective chemicals have come into use. In Part 2, a short-term field test is described for determining the toxicity of single applications of pesticides at recommended rates to European red mite (ERM),Panonychus ulmi, and its predator, an organophosphate (OP)-resistant strain ofT. pyrion apples in New Zealand. For each pesticide, changes in mite density were measured from pre-treatment to 2, 7 and up to 25 days post-treatment compared with a water-sprayed control. Density was recorded and analysed for live adult and immature ERM, and live and dead eggs, larvae, nymphs and adults ofT. pyri. Fifteen acaricides, 17 fungicides and 17 insecticides were evaluated. Chemicals more toxic toT. pyrithan ERM were aminocarb, amitraz, binapacryl, chlordimeform, etrimphos, fenvalerate + azinphos-methyl, mancozeb + dinocap, methidathion, methiocarb, omethoate, oxamyl, pirimiphos-methyl and pyrazophos. Chemicals equally or less toxic toT. pyrithan to ERM were acequinocyl, azocyclotin, benzoximate, bromopropylate, chlorpyrifos, clofentezine, cycloprate, cyhexatin, dinocap, mineral oil, propargite, triazophos and vamidothion. The remaining 23 chemicals (primarily fungicides and OP insecticides) had slight or no toxicity to ERM andT.pyri. The short-term field tests provided a useful guide to the long-term effects on ERM andT. pyripopulations of almost all the pesticides. However, the potential disruptive effect of pyrazophos was not found in long-term field trials, and conversely, the apparently harmless dithiocarbamate fungicides were later shown to be highly disruptive when repeatedly sprayed, as in commercial practice. Most of the chemicals tested are no longer used in commercial pome-fruit orchards in New Zealand, all of which now practise integrated fruit production or organic fruit production based on selective pest management methods. The tested pesticides of continuing importance are identified and discussed with special emphasis on the current need to retest for dithiocarbamate resistance inT. pyri, some populations of which have been exposed to these compounds for up to 40 years. This and the changes in pesticide use in New Zealand are paralleled by similar developments in most pome-fruit growing areas of the world. [ABSTRACT FROM AUTHOR]

The conclusions of the European Food Safety Authority (EFSA) following the peer review of the initial risk assessment carried out by the competent authority of the rapporteur Member State the United Kingdom, for the pesticide active substance methiocarb are reported. The context of the peer review was that requested by the European Commission following the submission and evaluation of confirmatory data on the risk assessment for birds. The conclusions were reached on the basis of the evaluation of the representative use of methiocarb as a molluscicide on oilseed rape. The reliable endpoints concluded as being appropriate for use in regulatory risk assessment, derived from the available studies and literature in the dossier peer reviewed, are presented. Concerns were identified.

In this work preliminary studies on application of immunochromatographic method to detection of pesticides in food samples, in particular fruit juices, are presented. The aim was to develop immunochromatographic technique on a porous membrane for rapid detection of the pesticides thiabendazole and methiocarb in fruit juices. For detection colloidal carbon conjugated with secondary antibody was used. The tests were evaluated visually. Our results show that in the fruit juices samples examined the detection limit for thiabendazole covered the MRL (maximum residue limit) for food of plant origin established by the legislative and for methiocarb the method has to be further optimised in order to decrease the detection limit below the MRL.

Highlights: [•] A stoichiometric ratio of 1:1 was determined for MC reacting with free chlorine. [•] MC reacted with free chlorine at an intrinsic rate constant of 2.42×108 M−1 s−1. [•] MCX and MCN were identified as the major degradation byproducts. [•] The further degradation of MCX to MCN (or MCXP) was highly pH dependent. [•] The toxicity of MC solution increased obviously after chlorination. [ABSTRACT FROM AUTHOR]

Cyclic voltammogram of methiocarb in 0.1 M HSO exhibited an irreversible anodic peak at about +1285 mV versus Ag/AgCl. Electro-oxidation and determination of methiocarb in spiked soil, river water and agrochemical formulation were realized on a newly prepared carbon-nanotube paste electrode by applying square wave voltammetry (SWV). The d E/d pH value indicated that the oxidation mechanism involved the coupling of H with the oxidation process. The peak signals were linearly related to methiocarb concentration in the range of 1.5-59.1 mgL with a detection limit of 0.45 mgL. The accuracy and selectivity of the proposed method were shown by calculating the recoveries of methiocarb from soil, river water and pesticide formulation Mesurol. The calculated percent recoveries for soil and river water samples spiked with 30.0 μg g and 40.0 μg mL levels were 99.3 ± 1.2 and 98.5 ± 0.3 at 95 % confidence limit, respectively. [ABSTRACT FROM AUTHOR]

Methiocarb (MC) is a widely used carbamate pesticide in agriculture and health programs. Although the main molecular mechanism of carbamate toxicity involves acetylcholinesterase inhibition, studies have also implicated the induction of oxidative stress. Therefore, the present study was aimed to evaluate the effect of acute MC exposure on lipid peroxidation, antioxidant defense systems, histological changes in Wistar rats and the protective effect of pretreatment with vitamin E and taurine. A total of 48 rats were randomly divided into six groups. Rats in group I were given corn oil, while those in group III were dosed with vitamin E (100 mg/kg body weight (b.w.)) and in group V were dosed with taurine (50 mg/kg b.w.). Rats in group II were administered with MC only (25 mg/kg b.w., 1/4 of median lethal dose (LD50)), while those in groups IV and VI were pretreated with vitamin E (100 mg/kg b.w.) and taurine (50 mg/kg b.w.) for 20 days, respectively, and then exposed to MC (25 mg/kg b.w.). The rats administered with MC showed significant increase in the levels of malondialdehyde in the liver and kidney as an index of lipid peroxidation. Levels of glutathione and activities of superoxide dismutase, catalase and glutathione peroxidase were significantly increased, while activity of glutathione reductase remained unchanged in both the tissues after MC treatment. Mild degenerative histological changes were observed in liver tissue, while the changes in kidney tissue were more severe then liver after MC treatment. Pretreatment with vitamin E and taurine resulted in a significant decrease in the lipid peroxidation and alleviating effects on antioxidant defense systems in both the tissues, while protective effects on the histological changes were shown only in kidney when compared with liver. In conclusion, the study has demonstrated that the acute MC exposure in Wistar rats caused oxidative damage on liver and kidney, which were partly ameliorated by the pretreatment of vitamin E and taurine. [ABSTRACT FROM PUBLISHER]

Statistical design and environmental relevance are important aspects of studies of chemical mixtures, such as pesticides. We used a dose-additivity model to test experimentally the default assumptions of dose additivity for two mixtures of seven N-methylcarbamates (carbaryl, carbofuran, formetanate, methomyl, methiocarb, oxamyl, and propoxur). The best-fitting models were selected for the single-chemical dose-response data and used to develop a combined prediction model, which was then compared with the experimental mixture data. We evaluated behavioral (motor activity) and cholinesterase (ChE)-inhibitory (brain, red blood cells) outcomes at the time of peak acute effects following oral gavage in adult and preweanling (17 days old) Long-Evans male rats. The mixtures varied only in their mixing ratios. In the relative potency mixture, proportions of each carbamate were set at equitoxic component doses. A California environmental mixture was based on the 2005 sales of each carbamate in California. In adult rats, the relative potency mixture showed dose additivity for red blood cell ChE and motor activity, and brain ChE inhibition showed a modest greater-than additive (synergistic) response, but only at a middle dose. In rat pups, the relative potency mixture was either dose-additive (brain ChE inhibition, motor activity) or slightly less-than additive (red blood cell ChE inhibition). On the other hand, at both ages, the environmental mixture showed greater-than additive responses on all three endpoints, with significant deviations from predicted at most to all doses tested. Thus, we observed different interactive properties for different mixing ratios of these chemicals. These approaches for studying pesticide mixtures can improve evaluations of potential toxicity under varying experimental conditions that may mimic human exposures. [ABSTRACT FROM PUBLISHER]