Determination, residue analysis and risk assessment of thiacloprid and spirotetramat in cowpeas under field conditions

Deposition, dissipation, metabolism and honey bee exposure risk of thiacloprid in greenhouse scenario

The degradation and non-target risks of neonicotinoids under greenhouse scenarios remain poorly understood. Thiacloprid' deposition, dissipation, metabolism and honey bee exposure risk on greenhouse-grown cowpea, cucumber and melon were analyzed using a rapid detection method for thiacloprid and five metabolites. The initial concentration ratios and half-lives in plant tissues were highest in leaves (67.8 % and 3.13 days), followed by flowers (19.8 % and 1.17 days), stems (9.2 % and 2.07 days) and fruits (3.1 % and 2.40 days). Except for flower part, cowpea exhibited the most robust initial deposition values-1.40, 13.54, and 1.06 mg kg-1 (stem, leaf, fruit)-outstripping other crops corresponding tissues by a staggering 1.18-15.20 times. In the 12-24 h following application, a surge in thiacloprid content within the fruits of cowpea, cucumber, and muskmelon was observed, escalating by 31.6 % (0.33 mg kg-1), 46.0 % (0.13 mg kg-1), and 105.4 % (0.07 mg kg-1), respectively. In addition to M31, four thiacloprid metabolites were identified, with peak concentrations occurring in 1-7 days. Metabolite concentration ratios were highest in fruits (33.9 %), followed by leaves (26.9 %), stems (24.3 %), and flowers (14.9 %). 20.3 % of the time and space sampling was higher than the exposure risk concern value (HQ > 50), and 46.43 % was higher than the oral risk concern value (HQ > 50). Leaves and flowers were identified as high-risk tissues, requiring 2-20 days to reach low-risk levels for pollinator exposure. The research provides insights into the environmental behavior of neonicotinoids and the associated risks to pollinating bees in greenhouse scenarios.

Exploring the dynamic behaviors of five pesticides in lettuce: Implications for consumer health through field and modeling experiments

Lettuce, a globally consumed nutritious vegetable, is often linked to concerns regarding pesticide residues. To address this issue, we conducted field trials and utilized dynamiCROP modeling to examine the uptake, distribution, translocation, and dissipation of five pesticides (λ-cyhalothrin, difenoconazole, acetamiprid, dimethomorph, and β-cypermethrin) commonly detected in lettuce. At harvest, pesticides residues were below the maximum residue limits (MRLs) at 0.05, 0.39, 0.047, 0.72, and 0.072 mg kg-1, respectively. Simulation results elucidated distinct behaviors of the pesticides following application to lettuce foliage across various compartments. However, all pesticides exhibited a common dissipation trend, initially stabilizing or increasing before gradually declining. For all five pesticides, the largest contribution of residues on lettuce leaves came from the leaf surface during the early period after application, and from the soil in the long term. Health risk assessments indicated negligible risks associated with consuming lettuce containing these pesticides, both in the short and long term.

In vivo tracing of cyromazine and three neonicotinoids in cowpea under field conditions by solid-phase microextraction combined with ultra-performance liquid chromatography-tandem mass spectrometry

BACKGROUND

Excessive pesticide residues in agricultural products could accumulate in organisms through the food chain, causing potential harm to human health. The investigation of dissipation kinetics and residues of pesticides in crops is crucial for the scientific application of pesticides and the mitigation of their adverse effects on human health. In vivo solid-phase microextraction (in vivo SPME) has unique advantages, but the research on field plants is still lacking and the quantitative correction methods need to be further developed.

RESULTS

A method combining in vivo solid-phase microextraction with ultra-performance liquid chromatography-tandem mass spectrometry (in vivo SPME-UPLC-MS/MS) was developed to monitor the presence of acetamiprid, cyromazine, thiamethoxam and imidacloprid in cowpea fruits grown in the field. The sampling rates (Rs) were determined using both in vitro SPME in homogenized cowpea samples and in vivo SPME in intact cowpea fruit samples. The in vivo-Rs values were significantly higher than the in vitro-Rs for the same analyte, which were used for in vivo SPME correction. The accuracy of this method was confirmed by comparison with a QuEChERS-based approach and subsequently applied to trace pesticide residues in field-grown cowpea fruits. The residual concentrations of each pesticide positively correlated with application doses. After 7 days of application at two different doses, all of the pesticides had residual concentrations below China's maximum residue limits. Both experimental data and predictions indicated that a safe preharvest interval for these pesticides is 7 days; however, if the European Union standards are to be met, a safe preharvest interval for cyromazine should be at least 13 days.

SIGNIFICANCE

This study highlights the advantages of in vivo SPME for simultaneous analysis and tracking of multiple pesticides in crops under field conditions. This technique is environmentally friendly, minimally invasive, highly sensitive, accurate, rapid, user-friendly, cost-effective, and capable of providing precise and timely data for long-term pesticide surveillance. Consequently, it furnishes valuable insights to guide the safe utilization of pesticides in agricultural production.

In situ mass spectrometry imaging reveals pesticide residues and key metabolic pathways throughout the entire cowpea growth process

Cowpea plants, renowned for their high edibility, pose a significant risk of pesticide residue contamination. Elucidating the behavior of pesticide residues and their key metabolic pathways is critical for ensuring cowpea safety and human health. This study investigated the migration of pesticide residues and their key metabolic pathways in pods throughout the growth process of cowpea plants via in situ mass spectrometry. To this end, four pesticides--including systemic (thiram), and nonsystemic (fluopyram, pyriproxyfen, and cyromazine) pesticides--were selected. The results indicate the direct upward and downward transmission of pesticides in cowpea stems and pods. Systemic pesticides gradually migrate to the core of cowpea plants, whereas nonsystemic pesticides remain on the surface of cowpea peels. The migration rate is influenced by the cowpea maturity, logarithmic octanol-water partition coefficient (log Kow) value, and molecular weight of the pesticide. Further, 20 types of key metabolites related to glycolysis, tricarboxylic acid cycle, and flavonoid synthesis were found in cowpea pods after pesticide treatment. These findings afford insights into improving cowpea quality and ensuring the safe use of pesticides.

Status and Perspective on Green Pesticide Utilizations and Food Security

Pesticides protect crops against pests, and green pesticides are referred to as effective, safe, and eco-friendly pesticides that are sustainably synthesized and manufactured (i.e., green chemistry production). Owing to their high efficacy, safety, and ecological compatibility, green pesticides have become a main direction of global pesticide research and development (R&D). Green pesticides attract attention because of their close association with the quality and safety of agricultural produce. In this review, we briefly define green pesticides and outline their significance, current registration, commercialization, and applications in China, the European Union, and the United States. Subsequently, we engage in an in-depth analysis of the impact of newly launched green pesticides on the environment and ecosystems. Finally, we focus on the potential risks of dietary exposure to green pesticides and the possible hazards of chronic toxicity and carcinogenicity. The status of and perspective on green pesticides can hopefully inspire green pesticide R&D and applications to ensure agricultural production and safeguard human and ecological health.

Residue behavior and consumer risk assessment of spirotetramat and chlorpyrifos on cabbage heads and cropped soil

A field experiment following good agricultural practices was laid out to study the dissipation of spirotetramat (90 g a.i. ha-1 and 180 g a.i. ha-1) and chlorpyrifos (400 g a.i. ha-1 and 800 g a.i. ha-1) on cabbage heads and soil. Samples were processed using quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for residue estimation of spirotetramat and chlorpyrifos, which were further detected using HPLC-PDA and GC-FPD respectively. The residues of spirotetramat on cabbage heads reached below detection limit (BDL) (< 0.05 mg kg-1) on 7th and 10th day and for chlorpyrifos, BDL (< 0.01 mg kg-1) was achieved on 10th and 15th day for X and 2X dose, respectively. On 20th day after second spray, residues in soil were found to be BDL for both the pesticides. Half-life of spirotetramat and chlorpyrifos was found to be 3 and 2 days, respectively while a safe pre-harvest interval (PHI) of 9 days for spirotetramat and 10 days for chlorpyrifos is suggested on cabbage. The dietary risk assessment studies for various age groups of Indian population, ascertained safety of treated cabbage heads for consumption, as current study revealed that hazard quotient (HQ) < 1 and theoretical maximum dietary intake (TMDI) < maximum permissible intake (MPI) for both the pesticides at respective PHI.

Dissipation, accumulation, distribution and risk assessment of fungicides in greenhouse and open-field cowpeas

Pesticide residues in cowpeas have raised worldwide concern. However, only a few studies have focused on pesticide accumulation and distribution in greenhouse and open-field cowpeas. Field trial results suggest that difenoconazole, dimethomorph, thifluzamide and pyraclostrobin dissipated faster in open fields (mean half-lives, 1.72-1.99 days) than in greenhouses (2.09-3.55 days); moreover, fungicide residues in greenhouse cowpeas were 0.84-8.19 times higher than those in the open-field cowpeas. All fungicides accumulated in the greenhouse and open-field cowpeas after repeated spraying. Fungicide residues in old cowpeas were higher than those in tender cowpeas, and residues in the upper halves of cowpea pods were higher than those in the lower halves. In addition, cowpeas distributed in the lower halves of the plants had higher fungicide residues. Our findings suggest that greenhouse cultivation contributed to the pesticide residues in cowpeas after repeated spraying, although the levels of dietary health risks remained acceptable under both cultivation scenarios.

Greenhouse cultivation enhances pesticide bioaccumulation in cowpeas following repeated spraying

Understanding pesticide residue patterns in crops is important for ensuring human health. However, data on residue accumulation and distribution in cowpeas grown in the greenhouse and open field are lacking. Our results suggest that acetamiprid, chlorantraniliprole, cyromazine, and thiamethoxam residues in greenhouse cowpeas were 1.03-15.32 times higher than those in open field cowpeas. Moreover, repeated spraying contributed to the accumulation of pesticide residues in cowpeas. Clothianidin, a thiamethoxam metabolite, was detected at 1.04-86.00 μg/kg in cowpeas. Pesticide residues in old cowpeas were higher than those in tender cowpeas, and the lower half of the plants had higher pesticide residues than did the upper half. Moreover, pesticide residues differed between the upper and lower halves of the same cowpea pod. Chronic and acute dietary risk assessments indicated that the human health risk was within acceptable levels of cowpea consumption. Given their high residue levels and potential accumulation, pesticides in cowpeas should be continuously assessed.

CAN-Promoted Thiolative ipso-Annulation of Unactivated N-Benzyl Acrylamides: Access to SCN/SCF3/SO2Ar Containing Azaspirocycles

A variety of acrylamides holding an unactivated N-benzyl group underwent dearomative ipso-cyclization induced by sulfur-centered radicals (SCN/ SCF₃/ SO₂Ar) in the presence of ceric ammonium nitrate (CAN) as the oxidant to furnish azaspirocycles in good yields. This is the first report on ipso-dearomatization of N-benzyl acrylamides that proceeds without a substituent at the para-position of the aromatic ring. The developed conditions are also found to be suitable for substrates holding substituents such as F, NO₂, OMe, OH, and OAc at the para-position. The reaction features water as the source of oxygen, is compatible with a variety of functional groups, and proceeds in a short time.