Residue levels and risk assessment of acetamiprid-pyridaben mixtures in cabbage under various open field conditions.

Acetamiprid and pyridaben are highly efficient insecticides widely used to protect leafy vegetables against various pests, such as Phyllotreta striolata, but analyses of their residual behaviors applied in mixtures in cabbage fields are primarily lacking. Herein, field trials were performed by spraying 50% acetamiprid-pyridaben wettable powder (50% WP) once at a dose of 150 g of active ingredient per hectare in 12 representative provinces of China under Good Agricultural Practices. The residues of acetamiprid and pyridaben were detected using modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and liquid chromatography-tandem mass spectrometry, together with an assessment of their dietary risks. The average recoveries of the two insecticides were 84.6-104%, and the relative standard deviations were 0.898-10.1%. The residual concentrations of acetamiprid and pyridaben at the preharvest interval of 7 days were <0.364 and 0.972 mg/kg, respectively, and less than their maximum residue limits in cabbage (0.5 mg/kg for acetamiprid and 2 mg/kg for pyridaben) in China. The chronic and acute risk values of acetamiprid and pyridaben were 0.0787-33.3%, implying acceptable health hazards to Chinese consumers. In conclusion, applying 50% WP in cabbage fields under Good Agricultural Practices is acceptable. These results provide essential data for using mixtures of acetamiprid and pyridaben in cabbage fields.

Dissipation, residue distribution, and risk assessment of ethiprole and its metabolites in rice under various open field conditions.

BACKGROUND: Ethiprole has been registered to control planthoppers in rice fields for many years in Asia. However, its dissipation and residues in rice under natural field conditions and health hazards are largely unclear. In the present study, a modified QuEChERS (i.e. Quick Easy Cheap Effective Rugged Safe) and high-performance liquid chromatography-tandem mass spectrometry method was established to detect ethiprole and its metabolites, ethiprole amide and ethiprole sulfone, in brown rice, rice husks, and rice straw. The field experiments were implemented in 12 representative provinces of China under Good Agricultural Practices aiming to investigate the fate and terminal residues of ethiprole and its metabolites in rice. Finally, the dietary risk of ethiprole was evaluated. RESULTS: The average recoveries of these analytes in all matrices were 86.4-99.0% with a repeatability of 0.575-9.38%. The limits of quantification for each compound were 0.01 mg kg-1 . Dissipation of ethiprole followed the single first-order, first + first-order, and first-order multi-compartment kinetic models with a half-life of 2.68-8.99 days in rice husks. The dissipation half-life of ethiprole combining all metabolites was 5.20-16.2 days in rice husks. The terminal residues of ethiprole and its metabolites at preharvest intervals of 21 days were < 0.011, 0.25, and 0.20 mg kg-1 in brown rice, rice husks, and rice straw, respectively. Ethiprole amide was undetectable in all matrices, and the risk quotient of ethiprole was far less than 100%. CONCLUSION: Ethiprole rapidly converted to ethiprole sulfone in rice, and ethiprole and ethiprole sulfone mainly remained in rice husks and straws. The dietary risk of ethiprole was acceptable for Chinese consumers. © 2023 Society of Chemical Industry.

Dissipation Residue Behaviors and Dietary Risk Assessment of Boscalid and Pyraclostrobin in Watermelon by HPLC-MS/MS.

Fungicides containing active ingredients of boscalid and pyraclostrobin have been widely applied in watermelon disease control. To provide data for avoiding health hazards caused by fungicides, we investigated its terminal residues and evaluated the dietary risk. In this work, watermelon samples were collected from field sites in six provinces and analyzed with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The average recoveries of boscalid and pyraclostrobin in the watermelon matrix were 97-108% and 93-103%, respectively, with the relative standard deviations (RSDs) ≤ 9.1%. The limits of quantifications (LOQs) were 0.01 and 0.005 mg/kg for boscalid and pyraclostrobin. Twenty-one days after applying the test pesticide with 270 g a.i./ha, the terminal residues of boscalid and pyraclostrobin were all below 0.05 mg/kg and below the maximum residue limits (MRLs) recommended by European Food Safety Authority (EFSA). According to the national estimated daily intake (NEDI), the risk quotients (RQs) of boscalid and pyraclostrobin were 48.4% and 62.6%, respectively. That indicated the pesticide evaluated in watermelon exhibited a low dietary risk to consumers. All data provide a reference for the MRL establishment of boscalid in watermelon for China.

Residues and Safety Evaluation of Etoxazole, Bifenazate and Its Metabolite Bifenazate-diazene in Citrus Under Open-Field Conditions.

The residues of bifenazate (sum of bifenazate and bifenazate-diazene) and etoxazole in whole citrus and pulp collected from twelve regions of China were monitored and their chronic dietary risk to consumer were also evaluated. The citrus samples were extracted by a QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, and analyzed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The average recoveries of target compounds were ranged from 83 to 100% with relative standard deviations (RSDs) of 0.59-11.8%. The limits of quantification (LOQs) for three analytes were 0.01 mg/kg. At the interval to harvest of 20 and 30 days, the residues of total bifenazate and etoxazole were from below 0.02 to 0.26 mg/kg and from below 0.01 to 0.30 mg/kg in citrus samples. The chronic risk quotients (RQs) were below 100%, indicating no unacceptable risk to consumers.

Residue and intake risk assessment of prothioconazole and its metabolite prothioconazole-desthio in wheat field.

In the environment, plants and animals in vivo, pesticides can be degraded or metabolized to form transformation products (TPs) or metabolites, which are even more toxic than parent pesticides. Hence, it was necessary to evaluate residue and risk of pesticides and their TPs (or metabolites). Here, a rapid, simple, and reliable method using QuEChERS and LC-MS/MS had been developed for simultaneous analysis of prothioconazole and its toxic metabolite, prothioconazole-desthio, in soil, wheat plant, straw, and grain. The average recoveries of prothioconazole and prothioconazole-desthio in four matrices ranged from 86 to 108% with relative standard deviations (RSDs) of 0.53-11.87% at three spiking levels. The method was successfully applied to investigate the dissipation and terminal residues of the two compounds in wheat field. It was shown that prothioconazole was rapidly degraded to prothioconazole-desthio, with half-lives below 5.82 days. Prothioconazole-desthio was slowly dissipated in soil and plant. The terminal residues of prothioconazole in wheat grain with a pre-harvest interval (PHI) of 21 or 28 days were below the maximum residue limits (MRLs) (0.1 mg/kg, Codex Alimentarius Commission (CAC)). We also evaluated the intake risk of prothioconazole-desthio residues in wheat grain in China. For long-term intake assessment, the hazard quotients (HQ) ranged from 1.30 to 5.95%. For short-term intake assessment, the acute hazard indexes (aHI) ranged from 1.94 to 18.2%. It indicated that the intake risk of prothioconazole-desthio in wheat consumption was acceptable. Thus, the prothioconazole application on wheat with the scientific practices would not pose public health risk.

Dissipation kinetics of emamectin benzoate and lufenuron residues in cabbage grown under field conditions.

Residue analysis of emamectin benzoate and lufenuron in cabbage matrices and soil was developed using a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and ultra high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The samples were extracted with 1% acetic acid in acetonitrile (v/v) or 1% acetic acid in acetonitrile/water (5:1, v/v) and cleaned up by dispersive solid-phase extraction. Mean recoveries and relative standard deviations (RSDs) in all samples ranged 87.8-100.0 % and 3.6-12.6% for emamectin benzoate and 87.8-104.8 % and 6.2-11.5% for lufenuron, respectively. The validated method was used to evaluate the dissipation rate of emamectin benzoate and lufenuron in cabbage and soil as well as the residual levels in harvested cabbage and soil at different preharvest intervals (PHI). The half-lives of emamectin benzoate and lufenuron were 1.08-2.70 and 1.74-5.04 days in cabbage, and 1.42-4.01 and 0.94-6.18 days in soil, respectively. The terminal residues were below the China maximum residue limits (MRLs) at 3 days for emamectin benzoate (0.1 mg kg(-1)) and European Union MRLs at 5 days for lufenuron (0.5 mg kg(-1)), which suggested that 5 days could be recommended as the PHI for the commercial formulation of emamectin benzoate and lufenuron application in the Chinese cabbage field.

Dissipation patterns, residue analysis, and risk evaluation of hexaflumuron in turnip and cauliflower under Chinese growth conditions.

Hexaflumuron has been globally registered over 2 decades to control the pests in brassicaceous vegetables, while data on its dissipation and residues in turnip and cauliflower is scarce. Herein, field trials were carried out at six representative experimental sites to study the dissipation behaviors and terminal residues of hexaflumuron in turnip and cauliflower. The residual amounts of hexaflumuron were extracted using a modified QuEChERS and analyzed with liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the chronic dietary risk to Chinese populations was evaluated, and the maximum residue limit (MRL) in cauliflower, turnip tubers, and turnip leaves was calculated by the OECD MRL calculator. The single first-order kinetics model was the best-fitted kinetics model for hexaflumuron dissipation in cauliflower. The indeterminate order rate equation and first-order multi-compartment kinetic model were the best formulae for hexaflumuron dissipation in turnip leaves. The half-lives of hexaflumuron ranged from 0.686 to 1.35 and 2.41 to 6.71 days in cauliflower and turnip leaves, respectively. The terminal residues of hexaflumuron in turnip leaves of 0.321-9.59 mg/kg were much higher than in turnip tubers of < 0.01-0.708 mg/kg and cauliflower of < 0.01-1.49 mg/kg at sampling intervals of 0, 5, 7, and 10 days. The chronic dietary risk of hexaflumuron in the preharvest interval of 7 days was lower than 100% and much higher than 0.01%, indicating acceptable but nonnegligible health hazards for Chinese consumers. Therefore, MRL values of hexaflumuron were proposed as 2, 0.8, and 10 mg/kg in cauliflower, turnip tubers, and turnip leaves, respectively.

Abamectin induces cytotoxicity via the ROS, JNK, and ATM/ATR pathways.

Abamectin has been widely used in agriculture and animal husbandry. It has been shown that abamectin exposure could induce multiple toxic effects on non-target organisms, but the underlying mechanism is still largely unknown. In the current study, the mechanism of abamectin-induced cytotoxicity was investigated in mouse embryonic fibroblast cells. Abamectin treatment could cause oxidative stress in cells (beginning at 0.4 µg/ml, 0.5 µM) and the ROS overproduction was mainly induced by the impacts of abamectin on the activities of CAT (beginning at 4.4 µg/mL, 5 µM), SOD (beginning at 8.7 µg/mL, 10 µM), GPx (beginning at 4.4 µg/mL, 5 µM), and contents of GSH (beginning at 4.4 µg/mL, 5 µM), which are important components of the ROS elimination pathway in mammal cells. Abamectin could impair DNA integrity (as demonstrated by increased 8-OHdG/dG ratio) in cells, even at environmental level (0.4 µg/mL, NOAEL), and abamectin-induced oxidative stress was one of the main reasons for the DNA damage that occurred in cells. Moreover, pretreatment with the inhibitor of JNK and ATM/ATR signaling pathway could partially rescue the decreased cell viability, indicating that oxidative stress and DNA damage might be involved in abamectin-induced cytotoxicity. These findings could provide new insights into the mechanism of abamectin-induced cytotoxicity and should be useful for a more comprehensive assessment of the adverse effects of abamectin.

ROS generation and DNA damage contribute to abamectin-induced cytotoxicity in mouse macrophage cells.

The widespread use of abamectin has recently raised safety concerns as abamectin has yielded various toxicities to non-target organisms. However, the underlying mechanisms of abamectin-induced toxicity are still largely unknown. The present study aimed to investigate the abamectin-induced cytotoxicity in mouse macrophage cells (RAW264.7) and its underlying mechanisms. Abamectin treatment caused oxidative stress as characterized by increased intensity of the ROS indicator. Abamectin also led to DNA damage as demonstrated by increased 8-OHdG/dG ratio in cells even at a relatively low dose (NOAEL). Pretreatment with catalase-PEG, a ROS inhibitor, attenuated abamectin-induced DNA damage, indicating that ROS overproduction should be the reason for abamectin-induced DNA damage. The effects of abamectin on ROS elimination and generation were also investigated, and the results showed that abamectin induced concentration-dependent alteration in the expression and activities of CAT, SOD, GPx enzymes and GSH level (ROS elimination), but had limited effects on the expression and activities of NOX, mitochondrial complex I and III (ROS production) in RAW264.7 cells. Therefore, the effects of abamectin on ROS elimination should be the main reason for abamectin-induced oxidative stress in RAW264.7 cells. Abamectin treatment activated MAPK and ATM/ATR signaling pathways as demonstrated by increased phosphorylation of JNK, ATM and ATR. In addition, inhibiting JNK and ATM/ATR signaling pathways partially rescued the decrease in cell viability, indicating that abamectin-induced ROS overproduction and DNA damage might finally lead to cytotoxicity through JNK and ATM/ATR signaling pathways. These findings should be useful for the more comprehensive assessment of the toxic effects of abamectin.

Simultaneous determination of pyridaben, dinotefuran, DN and UF in eggplant ecosystem under open-field conditions: Dissipation behaviour and residue distribution.

A sensitive method for simultaneous determination of pyridaben, dinotefuran, DN and UF in eggplant ecosystem was established and validated through rapid resolution liquid chromatography triples quadrupole tandem mass spectrometry (RRLC-QqQ-MS/MS). Matrix-matched external calibrations were introduced to check matrix effects. Limits of quantification (LOQs) of pyridaben, dinotefuran, DN and UF in eggplant were 0.2, 0.2, 1.0 and 1.0 µg kg-1, and 0.2, 0.2, 5.0 and 1.0 µg kg-1 in soil, respectively. Limits of detection (LODs) of four pesticides were below 0.41 µg L-1. The mean recoveries (n = 5) of these insecticides varied from 79.4% to 103%, and the relative standard deviations (RSDs) ranged from 2.1% to 15.3% at three levels. This method was applied to Chinese open-field samples from two representative locations, which were previously treated with these insecticides at the doses of 210-315 g a.i. ha-1 twice or three times. The dissipations of pyridaben and dinotefuran in eggplant and soil followed first-order kinetics with the half-lives of 3.65-11.4 d. The residues of pyridaben and total dinotefuran (calculated as sum of dinotefuran parent, DN and UF) in eggplant were below 0.0311 mg kg-1 at the pre-harvest interval (PHI, 7 d). Presently, no maximum residue limit (MRL) of pyridaben and dinotefuran in eggplant was recommended by China, Codex Alimentarius Commission (CAC) or European Union (EU). This study was important for evaluation of environmental fate and food safety of pyridaben and dinotefuran in eggplant ecosystems, and facilitated China to establish maximum residue limits (MRLs) of pyridaben and dinotefuran in eggplant.

Residue dissipation and risk assessment of tebuconazole, thiophanate-methyl and its metabolite in table grape by liquid chromatography-tandem mass spectrometry.

An efficient method was developed and validated for simultaneous determination of tebuconazole, thiophanate-methyl and its metabolite carbendazim in grape and soil using QuEChERS procedure and liquid chromatography-tandem mass spectrometry. The average recoveries of the method were 83.2%-105.4%, the limit of detection (LOD) ranged from 2.1 × 10-5 to 8.7 × 10-4 mg L-1, and the limit of quantitation (LOQ) was 0.1 mg kg-1. The field results showed that tebuconazole and thiophanate-methyl in soil and grape were rapidly dissipated with half-lives less than 24.7 days. The terminal residues of all analytes in grape were lower than the maximum residue limit (MRL) set by China (2 mg kg-1 for tebuconazole; 3 mg kg-1 for both thiophanate-methyl and carbendazim). Risk assessment showed that tebuconazole, thiophanate-methyl and its metabolite would be unlikely to cause health problems. However, carbendazim, the higher active metabolites of thiophanate-methyl, should receive more concerns.

Dissipation, residues and risk assessment of metaldehyde and niclosamide ethanolamine in pakchoi after field application.

A method using LC-MS/MS after QuEChERS preparation for the simultaneous determination of metaldehyde and niclosamide ethanolamine residues in soil and pakchoi has been developed and validated. The mean recoveries were ranged from 90% to 101% with RSDs (relative standard deviations) less than 9.2%. The dissipation results showed that the half-lives of metaldehyde and niclosamide ethanolamine were 2.3-4.3d and 1.7-9.5d, respectively. The terminal residue results indicated that the residues of metaldehyde in pakchoi were lower than the temporary maximum residue limits (MRL) set by China on 1 d after last treatment and the maximum residue of niclosamide ethanolamine in pakchoi was 0.54mg/kg. The risk quotients of metaldehyde and niclosamide ethanolamine were ranged from 0.015 to 0.033 and from 0.00064 to 0.0014, respectively. This work could provide guidance on reasonable use of these molluscicides and aid in the establishment of MRL in China.

Photodegradation of the novel fungicide fluopyram in aqueous solution: kinetics, transformation products, and toxicity evolvement.

The aqueous photodegradation of fluopyram was investigated under UV light (λ ≥ 200 nm) and simulated sunlight irradiation (λ ≥ 290 nm). The effect of solution pH, fulvic acids (FA), nitrate (NO3 (-)), Fe (III) ions, and titanium dioxide (TiO2) on direct photolysis of fluopyram was explored. The results showed that fluopyram photodegradation was faster in neutral solution than that in acidic and alkaline solutions. The presence of FA, NO3 (-), Fe (III), and TiO2 slightly affected the photodegradation of fluopyram under UV irradiation, whereas the photodegradation rates of fluopyram with 5 mg L(-1) Fe (III) and 500 mg L(-1) TiO2 were about 7-fold and 13-fold faster than that without Fe (III) and TiO2 under simulated sunlight irradiation, respectively. Three typical products for direct photolysis of fluopyram have been isolated and characterized by liquid chromatography tandem mass spectrometry. These products resulted from the intramolecular elimination of HCl, hydroxyl-substitution, and hydrogen extraction. Based on the identified transformation products and evolution profile, a plausible degradation pathway for the direct photolysis of fluopyram in aqueous solution was proposed. In addition, acute toxicity assays using the Vibrio fischeri bacteria test indicated that the transformation products were more toxic than the parent compound.

Identification of photoproducts of fungicide cyprodinil and elucidation of transformation mechanism in water using LC-IT-TOF-MS/MS technique.

This study aimed at investigating photodegradation of cyprodinil in aquatic solution under the simulated natural light or UV-visible irradiation (290-800 nm) using LC-MS/MS techniques. Effects of pH, nitrate ion, Fe (III), humic acid and TiO2 on photolysis kinetics of cyprodinil were explored. The photodegradation followed first-order reaction kinetics, and linear accelerating effects of Fe (III), nitrate ion and TiO2 with concentrations ranging from 0.1 to 5.0 mg L(-1) on photodegradation were remarkably observed. HA at low concentration ranges (<3.0 mg L(-1)) enhanced cyprodinil photodegradation while the photocatalytic rate was weakened with more addition of HA. The degradation rate in alkaline solutions was greater than in acidic solutions. Six main transformation products (TPs) were separated and identified based on mass spectra data and density functional theory (DFT) quantum calculations, and their kinetic evolutions were also investigated. Ultimately, a tentative transformation mechanism was proposed based the identified TPs and their kinetic evolutions. The results indicated that one α-H on pyridine ring of cyprodinil was hydroxylated to form TPs 1. TPs 1 underwent a series of photochemical reactions involving ring-opening, addition of one H2O molecule and demethylation on three-member ring to form TPs 2, which was further hydroxylated on benzene ring to form TPs 6. TPs 3-5 were three isomers from Hofmann-Martius rearrangement of cyprodinil. These findings were of utmost importance for elucidating environmental fate of cyprodinil in aquatic ecosystem and further environmental risk evaluation.

Dissipation kinetics and residues of florasulam and tribenuron-methyl in wheat ecosystem.

The dissipation kinetics and residual levels of florasulam and tribenuron-methyl in wheat field ecosystem were determined using a quick, easy, cheap, efficient, rugged and safe method (QuEChERS) with rapid resolution liquid chromatography tandem mass spectrometry (RRLC-MS/MS). The average recoveries of florasulam and tribenuron-methyl at three spiking levels in wheat plant, soil, wheat straw and wheat grain ranged from 72.8% to 99.2% with relative standard deviations (RSDs) were less than 10.1% and 82.5% to 103.8% with RSDs were less than 9.4%, respectively. The limits of quantification (LOQs) of florasulam and tribenuron-methyl for wheat plant, wheat straw, wheat grain and soil were 0.01, 0.01, 0.005, 0.005 mg kg(-1), respectively. The field trials results showed that the half-lives of florasulam were 2.76-10.83 d. Half-lives for tribenuron-methyl were found to be 1.27-5.37 d. The terminal residues in wheat grain were much lower than maximum residue limits (MRLs) set by China (0.01 mg kg(-1) for florasulam and 0.05 mg kg(-1) for tribenuron-methyl), which considered to be safe for human beings. These results will contribute to establishing the scientific basis of the dosage of florasulam and tribenuron-methyl for use in wheat field ecosystems.