Measured and Modeled Residue Dynamics of Famoxadone and Oxathiapiprolin in Tomato Fields

Dissipation and metabolism of fluxapyroxad, oxathiapiprolin and penthiopyrad in grapes: A comprehensive risk assessment from field to raisins

Understanding the residue fate of new pesticides in crops is essential to ensure their safe use and to safeguard human health. The present study examined the dissipation, metabolism, processing factors (PFs) and risk assessment of fluxapyroxad, oxathiapiprolin and penthiopyrad in grapes from field to raisins. The half-lives of the three pesticides in grapes ranged from 9.00 to 12.60 days following first-order kinetics. PAM, a penthiopyrad metabolite, was detected in grapes at 28.10-51.37 μg/kg. Most pesticide residues were concentrated in raisins during sun, shade and oven drying of fresh grapes (PF range, 0.70-2.39, most >1). In contrast, peeling and washing removed different amounts of pesticide residues from grapes (PF range, 0.27-0.81). Results of chronic and acute dietary risk assessments suggest that dietary exposure to the selected pesticides from grapes does not pose a human health concern. This study offers reliable guidance for the rational use of these pesticides in grape plantations.

Dissipation and dietary risk assessment of fluoxapiprolin (and its metabolites) residues in cucumber and tomato samples under field conditions

The present study was undertaken to understand the dissipation behaviour/kinetics of fluoxapiprolin and its metabolites in cucumber and tomato under field conditions. A QuEChERS based extraction method followed by liquid chromatography coupled to mass spectrometry (LC-MS/MS) analysis showed that all method validation parameters were within the acceptable range as per international standards with a limit of quantitation (LOQ) of 0.01 mg kg-1 for all analytes. As significant matrix effects were observed with a few metabolites, matrix matched standards were used for the whole study. Residues of fluoxapiprolin in cucumber at standard dose were steady from 0 to 3 day after application and were below LOQ on the 5th day after application. In cucumber fruit at double dose and in tomato at both the doses the residues followed second-order kinetics and were respectively ≤ LOQ from days 7 and 14 onwards. Pre-harvest intervals (PHI) of 5 days and 14 days are proposed for cucumber and tomato fruits respectively. All the metabolites were ≤ LOQ from day 0 in all the matrices. The consumer risk, assessed as Hazard Quotient (HQ), showed that HQ was ≤1 in all the cases. The results of the present study and earlier studies on other similar fungicides suggest that the use of fluoxapiprolin in cucumber and tomato fruits may not pose health or environmental hazards provided that good agricultural practices are followed and the proposed waiting period is observed. The data from the present study can be used by regulatory bodies in establishing maximum residue limits.

Fate characteristics and risk quantification of cyflumetofen from tomato cultivation to processing based on large-scale applications

Elucidating the fate characteristics of cyflumetofen and its main metabolite 2-TFMBA in tomato from cultivation to processing is crucial for safeguarding the environment and humans from hazardous effects. Cyflumetofen and 2-TFMBA could exist stably in tomato matrices for at least 343 days under frozen and dark conditions according to UHPLC-MS/MS, with a limit of quantitation of 0.001 mg/kg and retention time within 2.12 min. The occurrence, dissipation, and concentration variation of cyflumetofen were reflected by original depositions of 0.02-0.44 mg/kg, half-lives of 1.7-7.2 days, and terminal magnitudes of 0.005-0.30 mg/kg, respectively, with various influencing factors, e.g., climate conditions and tomato cultivars. Additionally, 13.5-59.3% of cyflumetofen was metabolized to 2-TFMBA, showing significant toxicological effects ranging from cultivation to processing. When the concentration decreased by 0.06 mg/kg, cyflumetofen was effectively removed by peeling, while washing was the recommended method for removing 2-TFMBA with a processing factor of 0.70. The comparative dietary risks of sum cyflumetofen were assessed for all life cycle populations using deterministic and probabilistic models. The risk quotients decreased to 1.3-4.8 times during the preparation of home canning tomato paste. Despite the low exposure risk, the potential health hazards of sum cyflumetofen should be considered, given its ubiquity and cumulative effects.

Assessing potential soil pollution from plant waste disposal: A modeling analysis of pesticide contamination

Pesticide residues can be taken up by plants after pesticide application, potentially resulting in soil pollution following the disposal of plant wastes at harvest. Currently, there is a lack of simple and efficient methods that can conduct high-throughput simulations to explore this problem across various chemicals and plant species. We present a modeling approach to simulating pesticide residue concentrations in soil as a result of plant waste disposal to assess the impact of plant wastes on agricultural soil pollution with respect to pesticide residues. This modeling approach employs well-established plant uptake models, providing versatility in evaluating different chemicals and plant species. The simulation process was tabulated in the spreadsheet interface, providing users with the flexibility to adjust input values for specific chemicals, plant species, and regions. The simulation results revealed that pesticides with relatively low lipophilicity (i.e., log KOW < 2) had low simulated residue concentrations in the soil as a result of plant waste disposal at harvest, whereas soil concentrations for lipophilic pesticides dramatically rose. This indicated that disposal of plant waste in agricultural soils will not pose significant ecological concerns to pesticides with low lipophilicity. The variability analysis showed that for certain pesticides, environmental factors (such as temperature and humidity) had a significant impact on the simulated residue concentrations in the soil as a result of plant waste disposal, which aided in the assessment of regional ecological risk as well as plant disposal management. Although some modeling aspects such as plant decomposition process, advanced plant uptake models, heterological distribution of residue concentrations in the soil, and plant waste stacking patterns require further research, the proposed approach can be used to assist in managing soil pesticides from plant waste disposal in preliminary stages.

Thyroid Dysfunction Induced by Fungicide Famoxadone Exposure Contributes to Nonalcoholic Fatty Liver Disease in Male Mice: In Vivo, In Vitro, and In Silico Studies

Thyroid dysfunction has become a serious public health problem, which is considered a trigger of nonalcoholic fatty liver disease (NAFLD). Pesticide exposure could contribute to thyroid dysfunction and NAFLD, but the relationship between these factors remains unclear. In this study, the effects of subchronic famoxadone exposure on thyroid and liver at no observed adverse effect level (NOEL) related concentrations were investigated using in vivo, in vitro, and in silico models. Famoxadone caused hepatic steatosis, lipid metabolism disorder, and liver oxidative stress and induced NAFLD in male mice. The suppression of hepatic fatty acid β-oxidation was the key factor of NAFLD, which was highly associated with hypothalamic-pituitary-thyroid (HPT) axis hormones disorder. Famoxadone disrupted thyroid hormone biosynthesis by causing thyroid follicle aberrations and abnormal HPT axis-related gene expression. In vitro studies confirmed that famoxadone inhibited the transport of thyroxine (T4) into hepatocytes and the conversion of T4 to triiodothyronine (T3). In silico studies verified that famoxadone interfered with the binding of thyroid hormones to proteins mediating thyroid hormone transport, conversion, and activation. This study comprehensively reported the association between NAFLD and thyroid dysfunction caused by famoxadone, providing new perspectives for the health risk evaluation of pesticides with a similar structure in mammals.

Hydroxide-Mediated SNAr Rearrangement for Synthesis of Novel Depside Derivatives Containing Diaryl Ether Skeleton as Antitumor Agents

A simple and efficient hydroxide-mediated S_NAr rearrangement was reported to synthesize new depside derivatives containing the diaryl ether skeleton from the natural product barbatic acid. The prepared compounds were determined using ¹H NMR, ¹³C NMR, HRMS, and X-ray crystallographic analysis and were also screened in vitro for cytotoxicity against three cancer cell lines and one normal cell line. The evaluation results showed that compound 3b possessed the best antiproliferative activity against liver cancer HepG2 cell line and low toxicity, which made it worth further study.

Uptake, Translocation, and Subcellular Distribution of Oxathiapiprolin and Famoxadone in Tomato Plants (Lycopersicon esculentum Miller)

The uptake, translocation, and subcellular distribution of oxathiapiprolin and famoxadone in tomato plants were investigated using hydroponic experiments. Oxathiapiprolin and famoxadone mainly accumulated in the tomato roots with limited translocation capacity from the roots to the upper part. The root absorption and inhibitor results noted the dominance of the apoplastic and symplastic pathways in the oxathiapiprolin and famoxadone uptake by the tomato roots, respectively. Furthermore, the uptake process for the two fungicides followed passive and aquaporin-dependent transport. Insoluble cell components (cell organelles and walls) were the dominant storage compartments for oxathiapiprolin and famoxadone. In the protoplast, oxathiapiprolin in the soluble fraction had a higher proportion than that of famoxadone. Finally, the uptake and distribution of the two fungicides by the tomato plants was accurately predicted using a partition-limited model. Thus, this study provides an in-depth understanding of the transfer of oxathiapiprolin and famoxadone from the environment to tomato plants.

Toxicokinetics of Two Oxathiapiprolin Enantiomers in Rats and Their Stereoselective Interaction with Oxysterol Binding Protein

Oxathiapiprolin is a chiral fungicide, and it can affect the metabolism of the cholesterol compounds by inhibiting oxysterol binding protein (OSBP) to exert its fungicidal effect. The application of oxathiapiprolin in agriculture is widespread, and its residue in the environment is a threat to both human and animal health. The two oxathiapiprolin enantiomers differ in their fungicidal activity, biotoxicity, and degradation by environmental forces. However, their biotoxicity has not been reported in animals. The toxicokinetics of a pesticide should be a crucial component for the evaluation of its toxicity in vivo. In this study, we investigated the absorption, bioavailability, tissue distribution, and excretion of the two oxathiapiprolin enantiomers in rats to verify their toxicokinetic process in animals. An ultrahigh-performance liquid chromatography triple quadrupole tandem mass spectrometry (UHPLC-QQQ/MS) method was established to quantify the two oxathiapiprolin enantiomers in vivo. The two oxathiapiprolin enantiomers were found to have approximately the same absorption rate and bioavailability, and both were excreted mainly in the feces. The half-life of R-(-)-oxathiapiprolin was nearly twice that of S-(+)-oxathiapiprolin. R-(-)-oxathiapiprolin also had greater distribution than S-(+)-oxathiapiprolin in the liver, lungs, heart, spleen, kidneys, stomach, large intestine, small intestine, brain, and pancreas, supporting the notion that R-(-)-oxathiapiprolin could better bind with OSBP. The stereoselectivity of S-(+)-oxathiapiprolin in these tissues may be responsible for it being readily metabolized in vivo. The molecular docking technique was subsequently used to verify the more superior binding between R-(-)-oxathiapiprolin and OSBP compared with the binding between S-(+)-oxathiapiprolin and OSBP. The findings of this study could provide more reliable data for determining the toxicokinetics of a single enantiomer of oxathiapiprolin in animals, thereby providing some theoretical basis for its subsequent toxicological study.

Uptake, translocation, and degradation of spirotetramat in tomato (Lycopersicon esculentum Miller): Impact of the mixed-application with pymetrozine

In this study, we investigated the impact of the mixed-application with pymetrozine on the behavior (i.e., uptake, translocation, and degradation) of spirotetramat in tomatoes under laboratory conditions. Results showed that pymetrozine promoted the uptake of spirotetramat from the nutrition solution after root application. The root concentration factor was 0.290 and 1.566 after spirotetramat single application and mixed-application with pymetrozine, respectively. It had little effect on the degradation of spirotetramat, with the metabolites of M-keto, M-enol, and M-glu in tomato issue (root, stems, and leaves). After foliar treatments, pymetrozine accelerated the translocation of spirotetramat from leaves to stems, with the translocation factor of 0.145 and 0.402 after spirotetramat single application and mixtures with pymetrozine, respectively. Pymetrozine also promoted the degradation of spirotetramat to M-kto and M-enol in leaves. Besides, a partition-limited model was used to describe the distribution processes of spirotetramat in the tomato-water system after root application. It showed that pymetrozine accelerated the distribution balance of spirotetramat in the whole system. Our result indicates that the interaction among pesticides should be considered when studied for the uptake, translocation, and degradation of pesticides in crops.

Dynamics and risk assessment of pesticides in cucumber through field experiments and model simulation

Pesticides are often applied multiple times during cucumber cultivation in China. In order to obtain the residue concentrations and subsequently human health risk assessment after pesticide multiple applications, plenty of field trials have been conducted, consuming a lot of labor force and funds. The application of kinetic models can address this problem to some extent by predicting the residue values of pesticides in cucumber. In this study, a dynamic model (dynamiCROP) was applied in combination with field experiments to investigate the distribution, translocation, and dissipation after the one-time application of seven pesticides in a cucumber-soil environment. Moreover, the residue concentrations after the second and third applications of the seven pesticides were estimated through a "simple superposition method", i.e., superimposing the output results of dynamiCROP after each single pesticide application. The estimated residue concentrations show good agreement with that measured through field experiments with R² = 0.865 and relative root mean squared error (RRMSE) = 13.2%. Meanwhile, the short- and long-term risks of each pesticide were assessed according to the concentrations estimated by the "simple superposition method" with the dynamiCROP model. It shows that the seven pesticides, applied multiple times during cucumber cultivation, pose a very low dietary risk to human health through cucumber intake. Our study presents a cost- and time-efficient way to investigate the dissipation of pesticides in the cucumber-soil environment, predicate the residue concentrations of pesticides after multiple applications and assess the dietary risk of pesticides to human health through cucumber intake.

Improving Pesticide Uptake Modeling into Potatoes: Considering Tuber Growth Dynamics

To explore pesticide uptake from soil into a growing potato, a moving-boundary dynamic model is proposed on the basis of the radical diffusion process of a chemical to a sphere. This model, which considers the logistic growth of the potato tuber, describes two hypothetical processes of chemical diffusion within a growing tuber. The model was tested in an illustrative case study for an application of chlorpyrifos. Results indicate that the distribution of chlorpyrifos concentrations along the potato radius is significantly affected by the tuber development. In comparison of our results to results from a classic model using a fixed boundary, the proposed dynamic model yields a quick and big jump for both the average concentration and bioconcentration factor (BCF) of chlorpyrifos in the potato as a result of the sigmoid expansion boundary. Overall, the dynamic model predicts that chlorpyrifos BCFs in the potato at harvest are higher than those using the classical model. In comparison of model results to measured uptake of chlorpyrifos into potato at harvest, the dynamic model shows better performance than the classical model. Our results provide a new perspective on pesticide uptake into potatoes and inform human health risk assessment for pesticides applied at different tuber growth stages.

Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra-high performance liquid chromatography-tandem mass spectrometry

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultra-high performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5 mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (-)-oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (-)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005 mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01 mg/kg in soybean and pea, and 0.025 mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (-)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

The immunotoxicity and neurobehavioral toxicity of zebrafish induced by famoxadone-cymoxanil

As a new protective and therapeutic fungicide, studies on famoxadone-cymoxanil are rare, and its toxicity to aquatic organisms has not been reported. In the present study, zabrafish embryos were exposed to several concentrations of famoxadone-cymoxanil at 10 hpf. Then, the changes of their shape, heart rate, development and function of innate and adaptive immune cells, oxidative stress, apoptosis, the expression of apoptosis-related genes and immune-related genes, the locomotor behavior were observed and detected in acute toxicity of famoxadone-cymoxanil. Our studies showed that, after exposure to famoxadone-cymoxanil, zebrafish embryos had decreased heart rate, shortened body length, swollen yolk sac. Secondly, the number of innate and adaptive immune cells was significantly reduced; and neutrophil migration and retention at the injury area were inhibited, indicating the developmental toxicity and immunotoxicity of famoxadone-cymoxanil on the zebrafish. We also found that the oxidative stress related indicators of embryos were changed significantly, and apoptosis were substantially increased. Further investigation of changes of some key genes in TLR signaling including TLR4, MYD88 and NF-κB p65 revealed that the mRNA expression of these genes was up-regulated. Meanwhile, the mRNA expression of some proinflammatory cytokines such as TNF-α, IFN-γ, IL6 and IL-1β was also up-regulated. In addition, the activity, the total distance, time and average speed were decreased along with the increase of exposure concentration. The absolute turn angle, sinuosity and the enzymatic activity of acetylcholinesterase (AChE) were also increased. These results suggested that famoxadone-cymoxanil can induce developmental toxicity, immunotoxicity and neurobehavioral toxicity in zebrafish larvae.

Dynamics and dietary risk assessment of thiamethoxam in wheat, lettuce and tomato using field experiments and computational simulation

Thiamethoxam is a widely used pesticide applied to different field crops. To inform risk assessment for this pesticide across relevant crops, we usually rely on field trials, which require time, costs and energy. For providing reliable data across crops and reduce experimental efforts, field trials should be complemented with dynamic modelling. In the present work, we hence focused on combining field trials with dynamic modelling to simulate mass evolutions of the pesticide-plant-system for thiamethoxam applied to wheat, lettuce and tomato as three major food crops. Field trials were conducted with QuEChERS (quick, easy, cheap, effective, rugged and safe) liquid chromatography-mass spectrometry, which gave consistent maximum residue concentrations for thiamethoxam in wheat, lettuce and tomato. We used these residues to evaluate the related dietary risk of humans consuming these food crops. Our results indicated that thiamethoxam did not provide any unacceptable dietary risk for humans across these three food crops, which is in line with findings from previous studies. Results for the studied crops could be extrapolated to other crops and with that, our study constitutes a cost- and time-efficient way of providing reliable input for risk assessment of pesticides across crops, which is relevant for both practitioners and regulators.

Dissipation studies of famoxadone in vegetables under greenhouse conditions using liquid chromatography coupled to high-resolution mass spectrometry: putative elucidation of a new metabolite

BACKGROUND

Famoxadone is a pesticide that is used to control fungal diseases and its dissipation in vegetables should be monitored. For that purpose, liquid chromatography coupled to mass spectrometry has been used.

RESULTS

The dissipation of famoxadone has been monitored in cucumber, cherry tomato and courgette under greenhouse conditions at different doses (single and double), using ultra high-performance liquid chromatography coupled to Orbitrap mass spectrometry (Thermo Fisher Scientific, Bremen, Germany). The concentration of famoxadone increased slightly just after the application of the commercial product and then decreased. The half-lives (DT₅₀ ) of famoxadone are different for each matrix, ranging from 2 days (courgette single dose) to 10 days (cucumber double dose). The main metabolites, 4-phenoxybenzoic acid and 1-acetyl-2-phenylhydrazine, were not detected in vegetable samples. Other metabolites described by the European Food and Safety Authority, such as IN-JS940 [(2RS)-2-hydroxy-2-(4-phenoxyphenyl)propanoic acid], IN-KF015 [(5RS)-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione] and IN-MN467 [(5RS)-5-methyl-3-[(2-nitrophenyl)amino]-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione], were detected in the three matrices. Untargeted analysis allowed for the putative elucidation of a new metabolite of famoxadone in cucumber (up to 290 μg kg^-1 ) and cherry tomato (up to 900 μg kg^-1 ) samples.

CONCLUSION

The dissipation of famoxadone has been investigated in three vegetables: tomato, cucumber and courgette. The persistence of famoxadone was low in the three matrices (DT₅₀ less than 10 days). Metabolites of famoxadone were monitored, detecting IN-JS940, IN-MN467 and IN-KF015, and the putative elucidation of a new metabolite of famoxadone was performed by applying software tools. © 2019 Society of Chemical Industry.

Residues and dissipation kinetics of famoxadone and its metabolites in environmental water and soil samples under different conditions

The dissipation of famoxadone as well as the behaviour of its metabolites in environmental samples such as water and soil is a major concern. In this study, the dissipation of the target compound in both matrices was carried out applying an analytical method based on ultra-high performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS). The dissipation of famoxadone was monitored over a period of 100 days after the plant protection product, Equation Pro^®, was administered to the target matrices. This study was performed at two doses, normal and double in the case of soils and fivefold instead of double dose in water. The concentration of famoxadone steadily decreased during the monitoring period in both matrices. Half-life (DT₅₀) values were lower than 30 days in most cases except for loam soils, for which it was 35 days. Therefore, persistence of this pesticide in both matrices was low. Famoxadone metabolites such as IN-KF015 ((5RS)-5-methyl-5-(4-phenoxyphenyl)-1,3- oxazolidine-2,4-dione) and IN-JS940 ((2RS)-2-hydroxy-2-(4- phenoxyphenyl)propanoic acid) were detected in both matrices and their concentration increased while the concentration of the parent compound decreased. Metabolite IN-JS940 was the compound detected at highest concentration for both matrices. In water the maximum concentration was 20% of the initial famoxadone content and in soils it was 50% of initial famoxadone content. In addition, another metabolite, IN-MN467 ((5RS)-5-methyl-3-[(2-nitrophenyl)amino]- 5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione), was detected in soils, following the same behaviour as the other metabolites. These results provided ample information about the behaviour of metabolites and the necessity of knowing their toxicity in both matrices in order to detect possible risks for living beings.

Dynamic modeling of famoxadone and oxathiapiprolin residue on cucumber and Chinese cabbage based on tomato and lettuce archetypes

We analyzed the uptake and distribution of two pesticides (famoxadone and oxathiapiprolin) in herbaceous vegetables (cucumber and tomato) and leafy vegetables (Chinese cabbage and lettuce) to test the viability of applying existing archetypes in the dynamic plant uptake model dynamiCROP to modeling pesticide residue in other crops. Using field data and modeling, we showed that tomato was an unsuitable match for cucumber (R2 of 0.5325-0.6862) though lettuce was a good fit for Chinese cabbage (R2 of 0.8649-0.8862). We then used our cucumber data to add this as a new crop species archetype in dynamiCROP; further tests proved the accuracy of this approach (R2 of 0.8097-0.9152). In addition, we analyzed the distribution, uptake, and translocation of the two pesticides in cucumber and Chinese cabbage, using the model to better understand the mechanisms of pesticide residues over time and evaluate potential human exposure to pesticide residues from consumption of these crops. The fractions of famoxadone and oxathiapiprolin eventually ingested by humans based on our field trials ranged from 10-4 to 10-3 kg intake kg applied-1; that is, per kilogram of pesticide applied, humans would eventually consume less than one gram.

Dissipation kinetic studies of fenamidone and propamocarb in vegetables under greenhouse conditions using liquid and gas chromatography coupled to high-resolution mass spectrometry

In this study, fenamidone, propamocarb and their transformation products were monitored in cherry tomato, cucumber, and courgette samples. A mixture of both compounds, which have different physico-chemical characteristics, are commercially available (Consento^®). For analysis, ultra high-performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) and gas chromatography coupled to Q-Orbitrap mass spectrometry (GC-Q-Orbitrap-MS) were used. The dissipation of these active ingredients was monitored at two doses (normal and double dose) from 1 to 40 days after the application of the commercial product. Half-lives (DT₅₀) were lower than 30 days for both compounds, which indicates low persistence. Metabolites of both compounds were also monitored due to in some cases these can be more dangerous for human health than the parent compounds. The metabolites monitored were RPA 410193 ((5S)-3-anilino-5-methyl-5-phenylimidazolidine-2,4-dione), acetophenone, 2-phenylpropionic acid, 5-methyl-5-phenylhydantoin and 5-methylhydantoin for fenamidone, and propamocarb hydrochloride (propyl 3-(dimethylamino)propylcarbamate hydrochloride), N-oxide propamocarb (propyl [3-(dimethylnitroryl)propyl]carbamate), oxazoline-2-one propamocarb (3-[3-(dimethylamino)propyl]-4-hydroxy-4-methyl-1,3-oxazolidin-2-one), 2-hydroxypropamocarb and n-desmethyl propamocarb (propyl [3-(methylamino)propyl]carbamate) for propamocarb. In addition, they were detected one day after the application of commercial product, being RPA 410193, the metabolite detected at the highest concentration in samples. Retrospective analysis of incurred samples allowed putative identification of four possible new metabolites of propamocarb and one of fenamidone.

Modelling the behavior of pesticide residues in tomatoes and their associated long-term exposure risks

This study is focused on the dissipation behavior of 7 fungicides and 5 insecticides applied in tomatoes after a third spraying at recommended and double doses by considering 6 kinetic models which allow estimating the pesticides half-lives (t_1/2). Except studying the pesticides dissipation, another scope of our manuscript was investigating the risk to human health after application of different pesticide treatments in tomatoes. The pesticides analysis in tomatoes at harvest showed that the residues were below the maximum residue level (MRL), with the exception of chlorotalonil (included in Group 2B - "Possibly carcinogenic to humans") and bifenthrin for recommended dose treatments, while for double dose treatments, the MRLs was exceeded for 7 pesticides, once again including chlorotalonil. For recommended dose treatments, the 1st order kinetic model is confirmed only for metalaxyl-M. The values of pesticides t_1/2 ranged from 0.006 days (for chlorothalonil) to 48.59 days (for myclobutanil). For double dose treatments, the 1st order kinetic model is confirmed for deltamethrin and triadimenol. In this case, the values of pesticides t_1/2 ranged from 0.32 to 10.67 days. Further, consumers' exposure was estimated by calculating the long-term risk based on hazard quotient (HQ). The results indicated that the risks generated by pesticide residues in tomatoes applied in recommended or double doses are in an acceptable limit, except for chlorothalonil which may pose a threat for children health. However, if we consider the cumulative hazard index (HI) values which were higher than 1, consumption of tomatoes containing pesticides residues may cause harmful non-carcinogenic health effects.