Transfer and risk assessment of fipronil in laying hen tissues and eggs

Fipronil is a persistent insecticide known to transfer into hen eggs from exposure from animal drinking water and feed, but some questions remain regarding its transfer behavior and distribution characteristics. Therefore, the dynamic metabolism, residue distribution and transfer factor (TF) of fipronil were investigated in 11 edible tissues of laying hens and eggs over 21 days. After a continuous low-dose drinking water exposure scenario, the sum of fipronil and all its metabolites (defined as fipronilT) quickly transferred to each edible tissue and gradually increased with exposure time. FipronilT residue in eggs first appeared at 3 days and then gradually increased. After a single high-dose feed exposure scenario, fipronilT residue in edible tissues first appeared after 2 h, quickly peaked at 1 day, and then gradually decreased. In eggs, fipronilT residue first appeared at 2 days, peaked 6-7 days and then gradually decreased. The TF values followed the order of the skin (0.30-0.73) > egg yolk (0.30-0.71) > bottom (0.21-0.59) after drinking water exposure, and the order of the skin (1.01-1.59) > bottom (0.75-1.1) > egg yolk (0.58-1.10) for feed exposure. Fipronil sulfone, a more toxic compound, was the predominant metabolite with higher levels distributed in the skin and bottom for both exposure pathways. FipronilT was distributed in egg yolks rather than in albumen owing to its lipophilicity, and the ratio of egg yolk to albumen may potentially reflect the time of exposure. The distinction is that the residues after feed exposure were much higher than that after drinking water exposure in edible tissues and eggs. The study highlights the residual characteristics of two exposure pathways, which would contribute to the tracing of contamination sources and risk assessment.

Distribution of fluopyram and tebuconazole in pomegranate tissues and their risk assessment

Residue distribution of fluopyram and tebuconazole was assessed in pomegranate whole fruit, aril, outer peel (pericarp), inner peel (mesocarp) and leaves. The method LOQ of fluopyram and tebuconazole were 0.01 and 0.02 mg kg^-1, respectively. Both fungicides remained in fruit peel and residues in edible aril were < LOQ. In fruit peel major portion of the fungicides remained on pericarp with minimal movement to mesocarp. In mesocarp fluopyram was 5.7-14.2%; tebuconazole, 7.5-14.4% of the residues in pericarp. Terminal residues of fluopyram and tebuconazole in pomegranate whole fruit were 0.037-0.094 and 0.036-0.096 mg kg^-1. Half-life of fluopyram in pomegranate fruit and leaves were 7.3-9.1 and 15 days; tebuconazole, 8-10.3 and 11.2-12.6 days, respectively. Pre-harvest intervals for treatment of combination formulation of fluopyram and tebuconazole, were 47-59 days in fruits, 158-173 in leaves. Dietary risk assessment demonstrated that consumption of peel and leaves may pose risk to human health, whereas fruit consumption was considered safe.

Residue distribution and risk assessment of two macrocyclic lactone insecticides in green onion using micro-liquid-liquid extraction (MLLE) technique coupled with liquid chromatography tandem mass spectrometry

A micro-liquid-liquid extraction (MLLE) technique coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis was established and validated to determine the residues of two macrocyclic lactone insecticides (spinetoram and spinosad) in green onion. The limit of quantification (LOQ) of the method, as demonstrated by the lowest acceptable recovery level, was 0.01 mg kg^-1, and the obtained recoveries were 78.3-93.4% with relative standard deviations (RSDs) < 12.5%. The method was then applied for analyzing field samples collected after treatment with the tested insecticides under Egyptian open-field condition. The decline pattern, terminal residues, and dietary risk assessment of spinetoram and spinosad residues in green onion were evaluated for food safety. Spinetoram and spinosad residues' decline in green onion followed first-order kinetics with the half-lives of 1.2 and 1.42 days, respectively. Based on the results, the required period to reach their respective maximum residue limits (MRLs) was 1 and 0 days for spinetoram and spinosad residues in green onion, respectively, which indicates a short persistence level and high degradation rate. The results suggest that there is no unacceptable chronic or acute risk to human health from the consumption of green onion treated with spinetoram and spinosad according to the uses considered.

Residue behaviors and risk assessment of flonicamid and its metabolites in the cabbage field ecosystem

Flonicamid, a novel selective systemic pesticide, can effectively control a broad range of insect pests. However, the dissipation behaviors and the terminal residues of flonicamid and its metabolites in some crops and soils remain unclear. Herein, an easy, sensitive and reliable method using a modified QuEChERS extraction coupled with LC-MS/MS for the simultaneous analysis of flonicamid and its metabolites in cabbage and soil was developed. Based on this method, the dissipation behaviors of flonicamid and its metabolites as well as their persistence in cabbage and soil during harvest were investigated. Flonicamid degraded rapidly, and the half-lives of flonicamid only and total residues (the sum of flonicamid and its metabolites) were 1.49-4.59 and 1.97-4.99 days in cabbage, and 2.12-7.97 and 2.04-7.62 days in soil, respectively. When 50% flonicamid WG was sprayed once or twice at the recommended dose and 1.5-fold the recommended dose, the highest residues of total flonicamid in cabbage and soil from different pre-harvest intervals (3, 7 and 14 days) were 0.070 and 0.054 mg kg^-1, respectively. The risk quotient (RQ) of flonicamid based on the consumption data from China was below 16.84%, indicating that the use of flonicamid is non-hazardous to humans. These results could not only guide the safe and responsible use of flonicamid in agriculture but also help the Chinese government establish the maximum residue level (MRL) for flonicamid in cabbage.

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.

Dissipation behaviour, residue distribution and dietary risk assessment of tetraconazole and kresoxim-methyl in greenhouse strawberry via RRLC-QqQ-MS/MS technique

20% commercial suspension emulsion (SE) of (8% tetraconazole + 12% kresoxim-methyl), as a pre-registered product in China, was firstly investigated under Chinese greenhouse-field conditions. A MWCNTs-based QuEChERS method for simultaneous determination of tetraconazole and kresoxim-methyl in strawberry was developed and validated via RRLC-QqQ-MS/MS. On basis of this method, the dissipation behaviours, residue distributions and dietary risk probability of these fungicides in strawberry were further investigated for food safety. The dissipations of tetraconazole and kresoxim-methyl followed first-order kinetics with the half-lives of 8.0-18.2 days. The highest residues (HRs) of these fungicides in the supervised trials at the pre-harvest interval (PHI, 3 days) were below 0.8970mgkg^-1. The total national estimated daily intake (NEDI) of tetraconazole and kresoxim-methy in strawberry at the PHI 3day was 0.2784mg and 0.4031mg, respectively, based on Chinese dietary pattern and terminal residue distributions under good agricultural practices (GAP) conditions. The risk quotients (RQs) of tetraconazole and kresoxim-methy at PHI 3 days were below 82.7% and 1.6%, respectively, showing that the evaluated strawberry exhibited an acceptably low dietary risk to consumers. The current study could not only guide reasonable usage of the formulation, but also facilitate the setting of maximum residue limits (MRLs) of tetraconazole in strawberry.

Dissipation behavior and residue distribution of fluazaindolizine and its seven metabolites in tomato ecosystem based on SAX SPE procedure using HPLC-QqQ-MS/MS technique

Fluazaindolizine suspension concentrate (500gL^-1 SC), as a pre-commercialized product, was firstly investigated under open-field conditions. A sensitive method for simultaneous determination of fluazaindolizine and seven metabolites (IN-QEK31, IN-F4106, IN-A5760, IN-UJV12, IN-UNS90, IN-QZY47 and IN-TMQ01) was established and validated using HPLC-QqQ-MS/MS technique. The LOQs of these pollutants in tomato were 0.01mgkg^-1, and their recoveries were 81.1%-117% with the relative standard deviations (RSDs <11.8%). The dissipation behaviours of fluazaindolizine in soil followed first-order kinetics with the half lives of 4.6-32.4days, whilst the residues in plant were below its LOQ after 7days. The fluazaindolizine residues in soil were below 0.963mgkg^-1, based on root irrigation applications (50-75mg a.i. per plant) twice and pre-harvest interval (PHI, 3days), while the residues of IN-QEK31, IN-F4106 and IN-A5760 were below 3.9mgkg^-1, excluding other four metabolites (<0.01mgkg^-1). The residues of fluazaindolizine in tomato were below 0.01mgkg^-1, and IN-QEK31 remained 0.135mgkg^-1. The current study could not only guide reasonable usage of the formulation, but also facilitate the setting of residue definition and its maximum residue limits (MRLs) of fluazaindolizine in tomato.