Effect of formulation on the indoxacarb and lufenuron dissipation in maize and risk assessment

Residue and dietary intake risk assessment of lufenuron and chlorfenapyr and its corresponding metabolite in cabbage under field conditions

A simple, low-cost, and highly sensitive method using a modified QuECHERS procedure based on a liquid chromatography-tandem mass spectrometer (LC-MS/MS) was established to simultaneously quantify lufenuron and chlorfenapyr and the corresponding metabolite tralopyril in cabbage for the first time. On the basis of this method, terminal residue and dietary risk of lufenuron and chlorfenapyr in cabbage were investigated. The recoveries of lufenuron, chlorfenapyr, and tralopyril ranged from 88 to 110%, with relative standard deviation of less than 12.4%. The field trial results showed that at the pre-harvest interval (PHI) of 21 days, the terminal residues of lufenuron, chlorfenapyr, and tralopyril in the supervised trials were not higher than 0.02 mg/kg, and the highest detected residue levels of lufenuron, chlorfenapyr, and tralopyril were 0.047, 0.055, and <0.02 mg·kg-1 at 14-day pre-harvest respectively, which were lower than the maximum residue limits (MRLs) for cabbage established in China. For the dietary risk assessment, the national estimated daily intakes (NEDIs) as proportion of acceptable daily intakes (ADIs) were 80.4% and 29.9% for chlorfenapyr and lufenuron respectively indicating an acceptable dietary risk to Chinese population.

Behavioral and Transcriptomic Analyses in the Indoxacarb Response of a Non-Target Damselfly Species

Ischnura senegalensis, which widely spreads in paddy fields, has the potential to be used as a natural predator of insect pests. However, the application of insecticides in the field could pose a threat to the survival of I. senegalensis. Among these pesticides, indoxacarb, an oxadiazine insecticide, is renowned for its broad-spectrum efficacy against numerous insect pests. In this study, we examined the toxicity of indoxacarb towards the larvae of I. senegalensis. Behavioral experiments and transcriptome analyses were conducted under indoxacarb treatments. Results revealed that indoxacarb induced abnormal body gestures and significant locomotory impairments, which could ultimately reduce the survival rate of the larvae in their natural habitat. Moreover, transcriptome analyses indicated that genes related to muscle function were significantly affected. Interestingly, at lower concentrations of indoxacarb (0.004 mg/L), the larvae seem to detoxify the indoxacarb with the aid of the cytochrome P450 gene. However, under higher concentrations (0.4 mg/L), the sensory abilities of the larvae were significantly diminished, and they were unable to degrade the toxicity of indoxacarb. Our study underscores the importance of carefully evaluating the impact of insecticides on non-target predatory insects before their widespread application.

Dissipation and evaluation of different treatments on the residues of different insecticides in/on cauliflower curd

A field study to understand dissipation rates and effect of various washing treatments on the residues of seven different insecticides, i.e. tetraniliprole 200 SC, emamectin benzoate 5 SG, lufenuron 5.4 EC, indoxacarb 14.5 SC, thiodicarb 75 WP, profenofos 50 EC and cypermethrin 25 EC in/on cauliflower curd has been conducted. The results showed that initial deposits (just after the last insecticide application, i.e. 0 d) of tetraniliprole, emamectin benzoate, lufenuron, indoxacarb, thiodicarb, profenofos and cypermethrin were 0.43, 0.03, 0.25, 0.28, 0.38, 6.70 and 0.68 mg kg-1, respectively. The dissipation pattern of all the tested insecticides followed monophasic, first order kinetics with the half-lives of 6.25, 8.85, 3.27, 7.71, 4.36, 2.98 and 3.76 d, respectively. Proposed pre-harvest intervals for these insecticides are 6, 9, 3, 8, 4, 3 and 4 d, respectively. All the decontamination techniques showed reductions in residue levels. However, treatment by soaking in 5% sodium bicarbonate aqueous solution showed 54%, 42%, 53%, 48%, 22%, 54% and 77% maximum reductions in residues of tetraniliprole, emamectin benzoate, lufenuron, indoxacarb, profenofos and cypermethrin, respectively, in cauliflower curds. The next best treatment was soaking cauliflower curds in water at 45-50 °C for 10 min, which reduced the residues of cypermethrin, profenofos, tetraniliprole, thiodicarb, emamectin benzoate and lufenuron.

Residue dissipation dynamics and dietary risk assessment of emamectin benzoate, chlorantraniliprole, chlorfenapyr, and lufenuron in cabbage

Emamectin benzoate (EB), chlorantraniliprole (CTP), chlorfenapyr (CFP), and lufenuron (LFR) are widely used to control Spodoptera exigua on cabbage. This study is aimed at establishing a universal, sensitive, accurate, and efficient method for the determination of these pesticide residues in cabbage using QuEChERS pretreatment combined with ultra-performance liquid chromatography or gas chromatography-tandem mass spectrometry (UPLC‒MS/MS or GC‒MS/MS). The recoveries of these pesticides (containing metabolites) in cabbage detected by the optimized method ranged between 80.9% and 99.9%, with relative standard deviations (RSDs) of 0.164-12.5%. The limit of quantification (LOQ) of the four pesticides was determined to be 0.01 mg/kg. The standard curve, accuracy, precision, and LOQ of the analysis method all met the requirements of pesticide residue detection. The optimized method was used to detect the dissipation dynamics and terminal residues in 12 regions. The dissipation half-lives of CTP, CFP, and LFR were 3.35-7.01 d, 2.29-4.75 d, and 3.24-6.80 d, respectively. The terminal residues of all these pesticides were below the maximum residue limits (MRLs). The dietary risk assessment indicated that the dietary risk probabilities for EB, CTP, CFP, and LFR were all less than 1 and were within the acceptable range. This study provides a comprehensive assessment of the residues and dietary risks of EB, CTP, CFP, and LFR for the scientific use of pesticides.

Enantioselectivity of indoxacarb enantiomers in Bombyx mori larvae: toxicity, bioaccumulation and biotransformation

BACKGROUND

Indoxacarb is a chiral insecticide with excellent insecticidal activity against lepidopterous insects. Because of their enantioselectivity, chiral pesticides' environmental behavior at the enantiomeric level has been highlighted. The chiral stability, enantioselective bioaccumulation, biotransformation behavior of indoxacarb to a non-target insect silkworm are still unclear.

RESULTS

A chiral analysis method for indoxacarb and its metabolite DCJW in silkworm was developed using liquid chromatography and high-resolution mass spectrometry (HPLC/HRMS). In silkworms, the recoveries of indoxacarb and DCJW were 86.06%-104.52% with relative standard deviation (RSD) < 9.01%. The 96-h lethal concentration (LC₅₀ ) values of R-indoxacarb, S-indoxacarb, and enriched S-indoxacarb (2.333 S/1R) were 1.08 × 10² , 1.92, and 6.89 mg a.i. L^-1 , respectively, according to the acute toxicity test results. When silkworm larvae were exposed to 1/50 of the LC₅₀ concentration, the bioconcentration factor (BCF) of R-indoxacarb was 0.0296-0.318, and the BCF of S-indoxacarb was 0.0125-0.211. In silkworm larvae, the amount of R-DCJW produced by R-indoxacarb was 0.00610 to 2.34 times that of the parent R-indoxacarb, and the amount of S-DCJW produced by S-indoxacarb was 0.125-36.9 times that of the parent S-indoxacarb.

CONCLUSION

There was no chiral transition from S-indoxacarb to R-indoxacarb or a transformation from R-indoxacarb to S-indoxacarb. Indoxacarb was preferentially bioaccumulated in silkworm larva, while S-indoxacarb bioconversion into the metabolite S-DCJW was much greater than R-indoxacarb bioconversion into R-DCJW. This study could improve understanding of the indoxacarb accumulation and transformation process in insects, as well as provide more scientific data for indoxacarb environmental and ecological risk assessment. © 2023 Society of Chemical Industry.

Fate and occurrence of indoxacarb during radish cultivation for multi-risk assessment

Agrochemical indoxacarb is an important tool for selective pest control in radish that be consumed globally. A rapid and sensitive analytical method UHPLC-MS/MS was developed for tracing indoxacarb in radish leaves and roots with LOQ of 0.001 mg/kg and RT within 2 min, which were confirmed the satisfied storage stability of indoxacarb in radish matrixes with degradation rates less than 30 %. The occurrence, pharmacokinetics dissipation and concentration variation of indoxacarb were reflected by the original deposition of 2.23-4.12 mg/kg, half-lives of 2.6-8.0 d and terminal magnitude of 0.17 × 10^-2-25.46 mg/kg in radish, and the influencing factors were further illustrated in terms of climate factors, crop cultivars and soil properties. The highest residues of indoxacarb were 25.46 mg/kg in leaves and 0.12 mg/kg in roots, which were higher than international maximum residue limits. A probabilistic model, as well as deterministic model, were introduced to evaluated the health risks of indoxacarb offering a better description for uncertainty. The total chronic dietary risk values of indoxacarb were 146.961-482.065 % in 12 registered crops, of which ADI % in radish was accounted for 19.8 % with risk dilution effects. The unacceptable acute dietary risks of 121.358-220.331 % were observed at 99.9th percentile, whereas the high-potential non-carcinogenic effects were observed over 90th percentile (105.035-1121.943 %). The health risks should be continuously emphasized given the increasing applications and persistent characteristics of indoxacarb, which is vital to protect the human population from hazardous effects, particularly for vulnerable children.

Incorporating Bioaccessibility into Inhalation Exposure Assessment of Emamectin Benzoate from Field Spraying

The inhalation exposure of pesticide applicators and residents who live close to pesticide-treated fields is a worldwide concern in public health. Quantitative assessment of exposure to pesticide inhalation health risk highlights the need to accurately assess the bioaccessibility rather than the total content in ambient air. Herein, we developed an in vitro method to estimate the inhalation bioaccessibility of emamectin benzoate and validated its applicability using a rat plasma pharmacokinetic bioassay. Emamectin benzoate was extracted using the Gamble solution, with an optimized solid-to-liquid ratio (1/250), extraction time (24 h), and agitation (200 rpm), which obtained in vitro inhalation bioaccessibility consistent with its inhalation bioavailability in vivo (32.33%). The margin of exposure (MOE) was used to assess inhalation exposure risk. The inhalation unit exposures to emamectin benzoate of applicators and residents were 11.05-28.04 and 0.02-0.04 ng/m³, respectively, varying markedly according to the methods of application, e.g., formulations and nozzles. The inhalation risk assessment using present application methods appeared to be acceptable; however, the MOE of emamectin benzoate might be overestimated by 32% without considering inhalation bioaccessibility. Collectively, our findings contribute insights into the assessment of pesticide inhalation exposure based on bioaccessibility and provide guidance for the safe application of pesticides.