Pesticide Residues in Commercial Lettuce, Onion, and Potato Samples From Bolivia-A Threat to Public Health?

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.

Upcycling Romaine lettuce outer leaves by infrared blanching and hot air drying

Romaine lettuce outer leaves, as opposed to the more commonly marketed heart, are typically discarded and present an opportunity for upcycling as dried powders. Duquesne Romaine lettuce was evaluated to quantify and compare quality attributes of fresh outer and heart leaves, dried powders following hot air drying, and dried powders following an infrared (IR) blanching pretreatment before drying. Attributes measured for fresh leaves included moisture, water activity (Aw), color, total soluble phenolics (TSP), and antioxidant capacity (AC). Drying kinetics and time/energy saving through IR blanching were evaluated. Attributes measured for dried powders included moisture, Aw, color, true density, water vapor isotherms, TSP, AC, cadmium (Cd) content, and pesticide residues. TSP, AC, Cd, and pesticide residues were higher, whereas moisture content and Aw were lower in fresh outer versus heart leaves. Hot air drying reduced TSP and AC to 63.6% and 35.2% of fresh values, respectively, whereas IR blanching further reduced TSP and AC to 37.3% and 25.4% in outer leave powders. On the other hand, TSP and AC increased 237% and 151%, respectively, for unblanched heart powders. Higher increase of TSP than AC in heart leaf powder may indicate synthesis of phenolic compounds activated by abiotic stresses such as cutting and high temperatures at the initial drying stage. IR blanching resulted in significant time/energy savings for drying of outer leaves. Microbial loads were substantially reduced during drying, although microbial population on outer leaves were more resistant. Safe to eat outer leaf Romaine lettuce powders can be produced, assuming appropriate agricultural practices.

Efficacy of some washing solutions for removal of pesticide residues in lettuce

Background

When previous studies were examined, it was reported that a wide variety of pesticide residues were detected in lettuce (Bakırcı et al. in Food Chem 160:379–392, 2014; Balkan and Yılmaz in Food Chem 384:132516, 2022; Qin et al. in Food Res Int 72:161–167, 2015; Selim et al. in Res J Environ Sci 5:248–258, 2011). In addition, pesticide-contaminated lettuce poses a risk to consumers as it is a fresh food that is eaten raw. Therefore, pesticide removal processes must be applied before consumption. Some pesticide removal process, such as storage and heat treatment cannot be applied to lettuce because of unshelled, no long shelf life and consuming as fresh. Different practical methods are needed for the removal of pesticides process. The recommendations of suitable methods for cleaning salad materials in ready-to-eat sector, hotels, restaurants and homes are very important. It is important to reduce pesticide residues in vegetables and fruits that are consumed raw by washing them with non-toxic solutions. These approaches aim to protect public health. The study conducted in 2021 determined the effect of various washing treatments. For this purpose, before the washing trials, QuEChERS method was validated for determination of 7 pesticides in lettuce, by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Lettuce plants were grown in the greenhouse for the study. Lettuces were brought to the laboratory 24 h after pesticides were applied in the greenhouse. The samples were kept in 2 L washing solution for pesticide analysis.

Results

The processing factor values of all washing applications were found below 1. This result shows that the residue level was reduced by washing solutions. Among the washing solution treatments, the rice vinegar washing solution was found to be most effective in reducing the pesticide residues which was due to the high degree in the pesticide degradation. Washing with filtered rice water also exhibited equivalent reduction capability similar to rice vinegar.

Conclusions

The effectiveness of washing solutions was different for boscalid, deltamethrin, fluopcolide, fluopyram, pyrimethanil, pyraclostrobin and sulfoxaflor. However, when the average removal of these pesticides was evaluated, the most effective solutions were rice vinegar, filtered rice water, carbonated water, NaCl + grape vinegar, hot tap water (40 °C), grape vinegar (6% acetic acid), grape vinegar + water, cold tap water (20 °C), lemon juice, baking soda water, grape vinegar (8% acetic acid), filtered mint water and grape vinegar (4% acetic acid), respectively. It was concluded that some of the solutions used in this study can significantly reduce exposure to pesticides for consumers.

Bioefficacy of Composite Medicinal Plant Extracts and Gum Arabic on Improving Postharvest Quality in Dragon Fruit

Several natural preservative techniques including plant extracts are used to minimize postharvest losses caused by pathogens. Our recent findings elucidated that the application of crude extracts of ginger, turmeric, and “dukung anak” (Phyllanthus niruri Linn.) alone causes phytotoxicity and adversely affects the postharvest quality of dragon fruit, especially at high concentrations. This study investigated the effect of a composite coating of 10% gum arabic (GA) and crude extracts of ginger, turmeric, and “dukung anak” separately at 5, 10, and 15 g L⁻¹ on postharvest quality of dragon fruit stored at 11 ± 2°C, 80% RH for 28 days. After 28 days of cold storage, anthracnose was significantly reduced in fruit coated with 10% GA plus 10 or 15 g L⁻¹ of any of the crude extracts and resolved the problem of phytotoxicity while maintaining the postharvest quality of fruit for 28 days. The reduction of anthracnose was pronounced at 10% GA+10 g L⁻¹ of turmeric extract (38.6%) which was not significantly different at 10% GA+10 g L⁻¹ of ginger extract compared to control (41.3%). Composite coating of 10% GA+10 g L⁻¹ of turmeric extract maintained the postharvest quality of dragon fruit as was evident with a reduction in weight loss (2.53%), delayed degradation of titratable acids (0.15%), and maintained fruit firmness (28.72 N) and the overall acceptability of the fruit after 28 days. We conclude that incorporation of 10% GA with turmeric extract at a high concentration can serve as a potential biofungicide in postharvest management of fresh produced by reducing phytotoxicity while improving the overall acceptability of fruit.

Improving pesticide uptake modeling and management in potatoes: A simple and approximate phloem-adjusted model

To evaluate the impact of the phloem flux on the pesticide uptake process in potatoes, this study developed a phloem-adjusted model based on the classic model that focuses mainly on the diffusion process. To achieve high-throughput simulations, we introduced an approximate method to convert the phloem flux transport process into a simple specific uptake rate of pesticides. In comparison to the classic model (non-phloem model), the phloem-adjusted model generated higher pesticide concentrations and bioconcentration factors (BCFs) in potatoes, owing to the additional pesticide uptake route introduced to the adjusted model. However, the simulation, which was conducted for 740 pesticides, indicated that for most pesticides, the phloem flux route did not contribute a significant portion of the pesticide uptake to potato tubers compared with the soil diffusion route. This was further characterized, using the differential factor (DF), to evaluate the difference in the simulated results between the proposed model and classic models. The largest DF (~0.11) was obtained for pesticides with moderate lipophilicity (i.e., log K_OW of 3.0), indicating that only a difference of 10% was generated between the two models. The 10% increase in pesticide concentration (or BCFs) in potatoes, simulated by the phloem-adjusted model, was within the acceptable uncertainty interval of the classic model, thus confirming the validity of using the classic model to predict the pesticide uptake process in potato tubers. However, we found that the negligibility of the phloem flux route was not merely due to hydrophobicity (i.e., hypothesis of the classic model), but was related to the i) plant physiology of potatoes, ii) lipophilicity of a pesticide, and iii) the diffusivity of a pesticide in water. Although future studies on pesticide concentrations in phloem sap and the dynamic growth of potatoes need to be undertaken, the model developed in this study reveals a more comprehensive pesticide uptake process in potatoes, which can promote the understanding of the pesticide uptake mechanism in potatoes.

Microbiological quality and determination of pesticide residues in the lettuce produced in Bahía Blanca's horticultural belt, Argentina

The aims of this research were 1) to find out the possible microbiological contamination and residues of pesticides (chlorpyrifos and cypermethrin) in lettuce grown in Bahía Blanca's horticultural belt, and bacteriological quality of waters used for irrigation and post-harvest washing, 2) to investigate and compare the internalization capacity of a strain of Escherichia coli isolated from irrigation water with another hospital uropathogenic strain. Some strains of bacteria can internalize into the plant tissue. This capability presents food safety threats as they cannot be removed with standard sanitation practices. To determine bacteriological quality of lettuce, E. coli, Salmonella spp and E. coli O157: H7/NM (n = 10) were investigated. Bacteriological quality of water was determined by quantification of fecal coliforms/100 mL (n = 20). Pesticides were determined by using an improved and validated QuEChERS method combined with GC-MSD. Irrigation water in 19/20 samples did not present health risk. Bacteriological quality of lettuce met demands in 9/10 samples. Pesticides were detected in half of the samples, values exceeding the FAO recommendations. An effort is strongly recommended to implement both, best phytosanitary practices and monitoring programmes. Uropathogenic strain was able to internalize into plant tissue, while the nonpathogenic one was not.

Pesticide traces in local crops of Sancti Spíritus, Cuba: risk assessment study

Background

Vegetables and rice produced in Cuba may contain residue of pesticides that exceed the maximum residue limits (MRLs). Pesticide residues on crop samples from Sancti Spíritus province were analyzed. Based on these residue data, a risk assessment of consumer exposure was conducted.

Methods

Samples collected during the 2017, 2018, and 2019 periods were analyzed using UPLC-MS/MS and GC/ECD chromatography techniques. A deterministic risk assessment was performed, using consumption data collected by the authors. Also, a probabilistic risk assessment was worked out with @RISK for the Monte Carlo simulation.

Results

A broad range of pesticides were detected in the samples. Most of the detected active ingredients were insecticides and fungicides. A considerable part of the detected pesticide residues exceeded the EU and Cuban MRLs. However, the deterministic risk assessment revealed that the consumer risk of pesticide exposure is low. Only in the maximum exposure scenario children and adults were exposed to methamidophos residues in tomatoes higher than the acceptable daily intake.

Conclusions

When a more realistic consumption (50th percentile) and higher (95th percentile) consumption pattern for tomatoes was assumed, the deterministic risk assessment found no chronic risk for children and adults being exposed to methamidophos present in the tomato samples. Furthermore, the probabilistic risk assessment concerning methamidophos exposure in tomato for children and adult strata showed no risk. To perform in the future a more accurate risk assessment for Cuban consumers it is important to have more detailed consumption data and an expanded dataset of the residues in different crops.

Dynamics of the Degradation of Acetyl-CoA Carboxylase Herbicides in Vegetables

(1) Background: Aryloxyphenoxy-propionates and cyclohexanediones are herbicides most widely used in dicot crops worldwide. The main objective of the study was to determine the dynamics of herbicide residues in carrot, lettuce, cauliflower, and onion in order to suggest a low level of residues in harvested vegetables. (2) Methods: Small plot field trials were carried out in four vegetables in the Czech Republic. The samples of vegetables were collected continuously during the growing season. Multiresidue methods for the determination of herbicide residues by LC-MS/MS were used. Non-linear models of degradation of individual herbicides in vegetables were calculated using the exponential decay formula. Action GAP pre-harvest intervals for the 25% and 50% maximum residue limit (MRL) and 10 µg kg⁻¹ limit (baby food) were established for all tested herbicides. (3) Results: The degradation dynamics of fluazifop in carrot, onion, and cauliflower was significantly slower compared to quizalofop and haloxyfop. The highest amount (2796 µg kg⁻¹) of fluazifop residues was detected in cauliflower 11 days after application. No residue of propaquizafop and cycloxydim was detected in any vegetable samples. (4) Conclusions: Aryloxyphenoxy-propionate herbicide (except propaquizafop) could contaminate vegetables easily, especially vegetables with a short growing season. Vegetables treated with fluazifop are not suitable for baby food. Lettuce and cauliflower treated by quizalofop are not suitable for baby food, but in onion and carrot, quizalofop could be used. Propaquizafop and cycloxydim are prospective herbicides for non-residual (baby food) vegetable production.

Studies on Dissipations and Residues of Indoxacarb under Different Field and Environmental Conditions

Indoxacarb is a broad-spectrum insecticide and widely used in agriculture. The dissipations and residues of indoxacarb were researched at three different field sites in Beijing, Hunan, and Zhejiang provinces in China. Analytical methods for determining the residue of indoxacarb in paddy water, paddy soil, rice straw, rice hull, and brown rice were described. Indoxacarb residues were extracted from samples, cleaned up by solid phase extraction, and determined by high-performance liquid chromatography coupled with tandem mass spectrometry in the selected ion monitoring mode. The recoveries in paddy water, paddy soil, rice straw, rice hull, and brown rice matrices at three spiking levels ranged from 79.7% to 98.3%, respectively. The field and environmental conditions would affect the dissipations and residues of indoxacarb. The time to dissipate 50% of indoxacarb in paddy water, paddy soil, and rice straw was less than 9 days. The terminal residues obtained from Beijing at preharvest interval of 14 and 21 days were higher than the maximum limit of European Union. Therefore, a dosage of 24 g a. i. ha-1 at 28 days preharvest interval with 3 spraying times was recommended. Such accumulation of measured data is necessary to provide guidance for the proper and safe use of this pesticide.

Resolving the twin human and environmental health hazards of a plant-based diet

Food can be health-giving. A global transition towards plant-based diets may equally help curb carbon emissions, slow land-system change and conserve finite resources. Yet, projected benefits of such 'planetary health' diets imperfectly capture the environmental or societal health outcomes tied to food production. Here, we examine pesticide-related hazards of fruit and vegetable consumption, and list proven management alternatives per commodity, geography and chemical compound. Across countries, pesticide use in these alleged healthful foods is extensive with up to 97% food items containing residues and up to 42% posing dietary risks to consumers. Multiple residues are present in 70-92% of US- and China-grown stone fruit while 58% US cauliflower is tainted with neonicotinoid insecticides. Science-based alternatives and decision-support frameworks can help food producers reduce risks and potential harm by deliberately abstaining from pesticide use. As such, opportunities abound to advance 'win-win' diets that simultaneously nurture human health and conserve global biodiversity.

Evaluation of Pesticide Residue Dynamics in Lettuce, Onion, Leek, Carrot and Parsley

The dynamics of 32 active substances contained in pesticide formulations (15 fungicides and 17 insecticides) were analyzed in iceberg lettuce, onion, leek, carrot, and parsley. Pesticide residues were monitored from the time of application until harvest. In total, 114 mathematical models of residue dissipation were developed using a first-order kinetic equation. Based on these models, it was possible to predict the action pre-harvest interval (the time between the last pesticide application and crop harvest) needed to attain a targeted action threshold (value significantly lower than the maximum limit) for low-residue vegetable production. In addition, it was possible to determine an action pre-harvest interval based on an action threshold of 0.01 mg kg-1 to produce vegetables intended for zero-residue production. The highest amount of pesticide residues were found in carrot and parsley leaves several days after treatment, and pesticide dissipation was generally slow. Lower amounts were found in leeks and lettuce, but pesticide dissipation was faster in lettuce. According to our findings, it seems feasible to apply reduced pesticide amounts to stay below unwanted residue levels. However, understanding the effectivity of reduced pesticide application for controlling relevant pest organisms requires further research.

Pesticide residues in tomato and tomato products marketed in Majmaah province, KSA, and their impact on human health

Over 22 samples of tomato, tomato paste, and ketchup collected from local markets, located in Majmaah Province, Saudi Arabia, were tested for the presence of 412 pesticide residues using the modified QuEChERS method, followed by LC-MS/MS and GC-MS/MS. About eight pesticide residues were detected in 36% of analyzed samples. The amount and frequency of detected pesticide residues were higher in tomato samples. All detected residues were below the maximum residue limits (MRLs). Multiple residues were detected in 27% of analyzed samples. Of the pesticides, cypermethrin was the most detected one followed by carbendazim. The average daily intake and health risk indices for Majmaah region population were estimated. The results showed that consumption of tomato and its products do not represent a risk to human health in this region. However, the presence of multiple residues in some samples necessitates regular monitoring of pesticide residues in tomato crop.

Automated Photochemically Induced Method for the Quantitation of the Neonicotinoid Thiacloprid in Lettuce

In this work, we present an automated luminescence sensor for the quantitation of the insecticide thiacloprid, one of the main neonicotinoids, in lettuce samples. A simple and automated manifold was constructed, using multicommutated solenoid valves to handle all solutions. The analyte was online irradiated with UV light to produce a highly fluorescent photoproduct (λexc/λem = 305/370 nm/nm) that was then retained on a solid support placed in the flow cell. In this way, the pre-concentration of the photoproduct was achieved in the detection area, increasing the sensitivity of the analytical method. A method-detection limit of 0.24 mg kg-1 was achieved in real samples, fulfilling the Maximum Residue Limit (MRL) of The European Union for thiacloprid in lettuce (1 mg kg-1). A sample throughput of eight samples per hour was obtained. Recovery experiments were carried out at values close to the MRL, obtaining recovery yields close to 100% and relative standard deviations lower than 5%. Hence, this method would be suitable for routine analyses in quality control, as an alternative to other existing methods.

Effect of Vegetal- and Seaweed Extract-Based Biostimulants on Agronomical and Leaf Quality Traits of Plastic Tunnel-Grown Baby Lettuce under Four Regimes of Nitrogen Fertilization

Nitrogen (N) fertilizers play a crucial role in agriculture, representing a powerful tool for farmers for increasing yields throughout the seasons under both optimal and suboptimal conditions. At the same time, their synthetic/chemical nature could have several influences on ecosystems and human health. For this reason, there is an urgent need to find new and more sustainable means of production to increase plant productivity and optimize nitrogen use. An experiment was conducted in a plastic tunnel to assess the response of baby lettuce crop to the foliar application of three plant biostimulants (PBs): Legume-derived protein hydrolysate (LDPH) ‘Trainer®’, tropical plant extract (TPE) ‘Auxym®’ and seaweed extract (SwE) from Ecklonia maxima ‘Kelpak®’ under different N rates of 0, 10, 20 and 30 kg N·ha−1. The responses of baby lettuce plants were assessed in terms of yield, growth parameters and physicochemical composition of the leaves. The fresh yield of baby lettuce in both biostimulant-treated and untreated plants was positively affected by increasing N rates from 0 to 20 kg N·ha−1, reaching a plateau thereafter indicating luxury N conditions at 30 kg N·ha−1. However, high N fertilizer application (20 and especially 30 kg N·ha−1) resulted in undesirable decreases in antioxidant activities and total ascorbic acid (TAA). Under non-fertilized regimens, foliar PBs application boost growth and yield of baby lettuce in comparison to non-treated plants. Foliar spray with LDPH and especially SwE elicited significant increases in marketable fresh yield (averaging 14%, 6% and 7% at 10, 20 and 30 kg N·ha−1, respectively) compared to TPE and untreated plants. Improved agronomical performance of baby lettuce under optimal (10 kg N ha−1) and especially suboptimal N regimens (0 kg N ha−1) was associated with increasing photochemical efficiency and a better activity of photosystem II (higher Soil Plant Analysis Development-SPAD index and chlorophyllous pigments biosynthesis). The application of LDPH enhanced antioxidant capacity and TAA in baby lettuce leaf and did not increased nitrate content as recorded in SwE and TPE treatments. Overall, plant biostimulants may be considered as a sustainable tool of production to increase leafy vegetable productivity in low fertility soils.

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.