Risk assessment of broflanilide for human and non-target terrestrial organisms in cauliflower production.

Broflanilide is a newly-developed meta-diamide insecticide, proposed for the control of a wide variety of chewing pests on many crops. In view of the proposed use of broflanilide and its environmental fate, it may be exposed to consumers and non-target organisms, which adversely affect human and the environment. In this paper, a rapid, sensitive and valid UPLC-MS/MS method was established for simultaneous analysis of broflanilide and its two major metabolites, DM-8007 and S (PFP-OH)-8007, in cauliflower. Then, the dissipation behaviors and final residues of broflanilide and its two major metabolites in cauliflower from eight sites with different climatic conditions in China were studied via the described analytical method. In addition, the acute toxicity test of 9.5 % suspension concentrate of broflanilide, broflanilide standard, DM-8007 and S (PFP-OH)-8007 were conducted to non-target terrestrial organisms. Risk assessment for human and non-target terrestrial organisms in cauliflower production was evaluated based on the maximum annual application rates and intervals. The results showed that the highest residue of broflanilide detected in cauliflower samples was all lower than the corresponding MRLs (2 mg/kg) in Japan. Chronic food dietary risk estimates for broflanilide do not exceed 50 % for all the Chinese population groups. Moreover, broflanilide is of low acute toxicity to birds and earthworm, while broflanilide and its metabolites is classified as highly toxic to adult honeybees. Acute risks of broflanilide to birds and earthworms were deemed to be acceptable in a realistic worst-case scenario, while its risk to adult honeybees and ladybug was unacceptable. A protection statement for honeybees and ladybug is required to recognize the high toxicity of broflanilide on related product labels. The study will be conducive to provide guidance for the rational application of broflanilide in cauliflower production.

Dissipation and dietary exposure risk assessment of spinosad, thiocyclam, and its metabolite nereistoxin in cucumber and groundwater for different population groups.

A QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique using ultrahigh-performance liquid chromatography with tandem mass spectrometry for the analysis of spinosad (spinosyn A + spinosyn D), thiocyclam, and nereistoxin in cucumber was developed with mean recoveries of 93-104%, relative standard deviations of ≤9%, and limits of quantification of 0.01 mg/kg. Field trials of spinosad and thiocyclam were performed in 12 representative cultivating areas in China. Field trial results indicate that spinosyn A and spinosyn D easily dissipated in cucumber with half-lives of 2.48-6.24 and <3 days, respectively. Nereistoxin was produced after thiocyclam application and was more persistent than its parent. The terminal residues of spinosad were all below the maximum residue limits (0.2 mg/kg) in China, whereas the terminal concentration of nereistoxin (calculated as the stoichiometric equivalent of thiocyclam), which was much higher than that of thiocyclam, was far beyond the maximum residue limits of thiocyclam in cucumber (0.01 mg/kg) established by the European Union. The predicted no-effect concentrations of spinosyn A, spinosyn D, thiocyclam, and nereistoxin leaching into groundwater were estimated using China-PEARL (Pesticide Emission Assessment at Regional and Local scales) models after application. However, the dietary (food and water) exposure risk quotient for different populations was below 1 with a preharvest interval set at 5 days after the last application, indicating that the application of spinosad and thiocyclam in cucumber was unlikely to pose unacceptable risk for human health. This study provides data for the safe use of spinosad and thiocyclam in cucumber ecosystem.

Residue behavior and dietary risk assessment of spinetoram (XDE-175-J/L) and its two metabolites in cauliflower using QuEChERS method coupled with UPLC-MS/MS.

Spinetoram (XDE-175-J/L), a new spinosyn-based insecticide, is one of the most widely used bio-pesticide worldwide and its registration for direct application on cauliflower to control Plutella xylostella is currently under review in China. In this study, an accredited method for simultaneous determination of spinetoram and its two metabolites in cauliflower was established and validated using QuEChERS (quick, easy, cheap, effective, rugged, and safe) preparation coupled with ultra-liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The average recoveries using this method were ranged from 74 to 99% with relative standard deviations (RSDs) of 2.4-10.5%. The dissipation kinetics and terminal residues of spinetoram and its two metabolites in cauliflower were studied in Tianjin and Guizhou over two years under open field conditions. The dissipation experiments revealed that spinetoram was swiftly degraded in cauliflower, with the half-lives less than or equal to 4.85 days. The terminal residues of total spinetoram (sum of spinetoram and its two metabolites) detected in cauliflower samples were in the range of 0.009 mg/kg-0.337 mg/kg. Dietary risk assessment study was implemented based on the scientific data of field trials, food consumption and acceptable daily intake (ADI). The estimated long-term dietary risk probability (RQ) of total spinetoram from cauliflower was between 5.79% and 5.91%, indicating that spinetoram was associated with acceptable risk for dietary cauliflower consumption. The results would provide scientific guidance for proper usage of spinetoram in cauliflower field ecosystem.

Residue behavior and dietary risk assessment of chlorothalonil and its metabolite SDS-3701 in water spinach to propose maximum residue limit (MRL).

Dietary risk assessment generally combines food consumption data and the concentration of pesticide by using the risk quotient (RQ) method. Chlorothalonil is the second popular fungicide in the world, and its residue and risk assessment in water spinach remain unknown. In this paper, the field trials of chlorothalonil in water spinach were operated under good agricultural practice (GAP) in China to human health protective. The dissipation experiments demonstrated that chlorothalonil was rapidly degraded in water spinach, with the half-lives of 1.8-3.2 days, and the amount of its metabolite SDS-3701 (4-hydroxy-2,5,6-trichloroisophthalonitrile) taken up through the water spinach roots from the soil was minor. The terminal experiments disclosed that the average residues of chlorothalonil and SDS-3701 in water spinach were below 6.59 mg/kg and 0.01 mg/kg, respectively. The results suggested the chronic dietary risk probability of chlorothalonil was 51.95-59.15% in terms of all registered crops, and the acute dietary risk probability of chlorothalonil was 12.30%-63.01% in water spinach, highlighting that the dietary risk of chlorothalonil in water spinach under GAP was acceptable. MRL of chlorothalonil was proposed as 7 mg/kg for water spinach and 5 days was recommended as a safe pre-harvest interval (PHI) for chlorothalonil application in water spinach field.

Photodegradation of fluazaindolizine in aqueous solution with graphitic carbon nitride nanosheets under simulated sunlight illumination.

The photodegradation of fluazaindolizine (FZDL) under simulated sunlight irradiation was accelerated by the catalysis of graphitic carbon nitride (g-C3N4). Under optimum conditions, such as 5 mg of amount and dispersion, the photodegradation half-life was dramatically enhanced to 2.7 h. More importantly, the pathway of degradation by g-C3N4 was different from both direct photolysis and the catalysis by titanium oxide, with particular negative ions of m/z 221 and 195, corresponding to the cleavage of sulfamide bond and the ring opening of imidazole, respectively. In addition, hydroxyl and superoxide radicals played important roles in photodegradation. The results enriched not only the study of FZDL photodegradation but also the application of g-C3N4. It also suggested the possibility of the water purification by photodegradation for pesticide removal in real life.

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.

Photodegradation of fluazaindolizine in water under simulated sunlight irradiation: Identification of transformation products and elucidation of transformation mechanism.

The photodegradation of fluazaindolizine in water was investigated under simulated sunlight irradiation. The effects of solution pH, humic acids (HA), nitrates (NO3-) and Fe(III) ions on photolysis of fluazaindolizine were studied. The results indicated that pH did not significantly affect its photodegradation. At low concentration (up to 5 mg/L), HA slightly facilitated the photodegradation of fluazaindolizine, while at high concentration (10-20 mg/L), HA inhibited its photodegradation. The presence of NO3- (0-10 mg/L) and Fe(III) (0-5 mg/L) noticeably accelerated the photodegradation of fluazaindolizine. Moreover, eleven direct transformation products (TPs) were isolated and identified by liquid chromatography quadrupole time-of-flight mass spectrometry. Density functional theory (DFT) calculation was utilized to characterize molecular property of fluazaindolizine and predict the potentiality of the possible photodegradation reaction. Ultimately, a possible transformation mechanism was proposed based on the identified TPs, degradation profiles and DFT calculation. The predominant photoproduct came from ring opening of imidazole-ring and dechlorination. Other TPs resulted from a series of photochemical reactions involving hydroxyl substitution, ring-opening, cleavage, oxidation and decarboxylation. These results were important in elucidating environmental fate of fluazaindolizine in aquatic system and further environmental risk assessment.

Residue analysis and dietary exposure risk assessment of tebufenozide in stem lettuce (Lactuca sativa L. var. angustana Irish).

Tebufenozide, a newly-developed nonsteroidal ecdysone agonist, is in pre-regulation phase (before approval for use) on stem lettuce in China. Aiming at the safe application of tebufenozide, the dissipation and terminal residue trials on stem lettuce were performed under good agricultural practice (GAP). The dissipation trials shown that tebufenozide was rapidly degraded in stem lettuce, with half-lives of 5.0-8.2 days. Pre-regulation dietary exposure risk assessments were evaluated to recommend maximum residue limits (MRLs) based on risk quotients (RQ) method. Relevant toxicological parameters including ADI (acceptable daily intake) and ARfD (acute reference dose) were applied to assess the potential dietary exposure risk. The results indicated the chronic dietary exposure risk probability (RQc) of tebufenozide ranged from 36.4% to 70.0%. The acute dietary exposure risk probability (RQa) of tebufenozide was 2.88%-8.49% in lettuce stems and 14.0%-20.0% in lettuce leaves, respectively. On the basis of supervised field trial data and dietary exposure risk assessment results, the MRLs of tebufenozide were recommended as 3 mg/kg for lettuce stems and 10 mg/kg for lettuce leaves, respectively. The results demonstrated that the dietary exposure risk of tebufenozide used in stem lettuce under GAP was negligible and would not pose unacceptable health risk to Chinese consumers.

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.

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.