Lettuce Samples Research Articles

Detection of Giardia spp. with formalin/ether concentration in Brassica oleracea (cabbage) and Lactuca sativa (lettuce)

Methods to detect protozoa are needed for food safety monitoring. We evaluated protocols to recover Giardia spp. cysts in Brassica oleracea (cabbage) and Lactuca sativa (lettuce) and then detection was performed by concentrating with formalin/ether solutions and microscopy or immunofluorescence or DNA amplification via PCR. To evaluate this methodology, G. duodenalis cysts were inoculated in triplicate (10 cysts) in 35-g samples of lettuce and cabbage. The method obtaining the highest percentage of recovery in cabbage was sulfamic acid solution plus stirring with stomacher (47.7% ± 7.5). For lettuce, the best method was glycine solution plus stirring with stomacher (46.6% ± 5.3). Inter-observer agreement was of 0.99. Giardia was detected by amplifying specific sequences for the DNA coding SSU rRNA. In 27 lettuce samples and 27 cabbage samples, obtained from supermarkets and street vendors, two lettuce samples (7.4%) and one cabbage sample (3.7%) were positive for Giardia via PCR assay and were sequenced, determining that they were two of assemblage B and one of lettuce to assemblage E. This method is proposed to detect Giardia in vegetables by PCR detection, enabling public health authorities to identify genotypes circulating in food, which will help to establish measures that reduce outbreaks of parasitic diseases associated with contaminated food.

Detection of Salmonella Typhimurium in Romaine Lettuce Using a Surface Plasmon Resonance Biosensor.

Leafy vegetables have been associated with high-profile outbreaks causing severe illnesses. Timely and accurate identification of potential contamination is essential to ensure food safety. A surface plasmon resonance (SPR) assay has been developed for the detection of Salmonella Typhimurium in leafy vegetables. The assay utilizes a pair of well characterized monoclonal antibodies specific to the flagellin of S. Typhimurium. Samples of romaine lettuce contaminated with S. Typhimurium at different levels (between 0.9 and 5.9 log cfu/g) were pre-enriched in buffered peptone water. Three SPR assay formats, direct assay, sequential two-step sandwich assay, and pre-incubation one-step sandwich assay were evaluated. All three assay formats detect well even at a low level of contamination (0.9 log cfu/g). The SPR assay showed a high specificity for the detection of S. Typhimurium in the presence of other commensal bacteria in the romaine lettuce samples. The results also suggested that further purification of flagellin from the sample preparation using immunomagnetic separation did not improve the detection sensitivity of the SPR assay. The functional protocol developed in this study can be readily used for the detection of S. Typhimurium in leafy vegetables with high sensitivity and specificity.

Using Machine Learning and Multi-Element Analysis to Evaluate the Authenticity of Organic and Conventional Vegetables

Concern for the consumption of organic vegetables is growing throughout the world. We verified the efficiency of machine learning techniques in the classification of vegetables produced under both organic and conventional systems in the state of Pernambuco, Brazil. The contents of 25 elements (Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Ti, V, Zn) were determined in 364 vegetable samples. Principal component analysis (PCA) was displayed to get a primary distribution overview of samples. Data mining techniques such as linear discriminant analysis (LDA) were carried out to develop discrimination models based on organic vegetable samples, and feature selection (F-score and chi-squared) combined with classification algorithms (support vector machine—SVM, multilayer perceptron—MLP, and random forest—RF) was applied to these samples. LDA reached 100% in the discrimination models in tomato samples and bell pepper samples, while SVM, combined with chi-squared, outperformed the other algorithms obtaining accuracy of 100% in bell pepper samples (Capsicum annuum) and onion (Allium cepa Hysam) and 97% in tomato (Solanum Lycopersicum) samples, of which 95% was the hit rate in organic samples. For lettuce (Lactuca sativa) samples, the accuracy obtained was 92%, with a 90% hit rate of samples grown in organic systems. This high success rate highlights the potential of using elemental quantification and algorithms as support techniques in the process of authenticity and inspection of organic products.

Suitability of centrifuge water for detecting the presence of Escherichia coli versus finished fresh-cut lettuce testing

Fresh produce causes most foodborne outbreaks in the USA, and it is also considered a hazardous food product in other areas of the world such as Europe. The outbreaks attributed to fresh produce increase the focus of producers on hygiene to minimize exposure to food hazards. The fresh produce industry has the urgent need to detect if there are production lots contaminated with pathogenic microorganisms before distribution. Although the industry is mostly using end-product testing for the detection of target microorganisms, previous studies have evaluated the suitability of different sampling points within the production line of a fresh-cut processing plant. In the present study, the centrifuge effluent water was assessed as an alternative sampling point to end-product testing. E. coli was selected as an index microorganism of the presence of pathogens. The presence of E. coli was assessed in centrifuge effluent water, and fresh-cut lettuce from a commercial fresh-cut produce processing line (n = 95). The rate of false positives and negatives, as well as the specificity, sensitivity, and efficiency of the alternative method were calculated. The mean population of E. coli in positive water samples was 0.86 log cfu/100 mL, while the mean population of E. coli in positive fresh-cut lettuce samples was 0.23 log cfu/g. The proportion of positive samples in centrifuge effluent water and lettuce was similar (≈20%), and most of the results in both matrices were coincident (81.1%). However, the alternative method was not reliable due to its low sensitivity, as only 47.6% of the lettuce samples positive for E. coli could be matched with positive water samples.

Effect of power ultrasound on quality of fresh-cut lettuce (cv. Vera) packaged in passive modified atmosphere

Effect of a combined power ultrasound (US) and chlorine disinfection treatment on quality of fresh-cut ready-to-eat lettuce (cv. Vera) was evaluated. Fresh-cut lettuce was disinfected using 100mgL−1 NaOCl solution alone and in combination with ultrasound (130W, 42kHz) for different times (0–30min). Lettuce samples (80g) were then packaged in polypropylene (PP) film and stored at 5°C for 8 d. Application of US improved microbial reduction on processing day: an additional reduction in the range of 0.5–2.5logcfug−1 was obtained with respect to NaOCl treatment alone. Combined US-NaOCl application did not cause visual changes to lettuce neither on processing day nor when samples were stored under refrigerated conditions in passive modified atmosphere. Confocal images evidenced that US application could affect lettuce surface wax layer, removing its natural defense against microorganisms. This resulted in higher microbial growth throughout storage in samples treated with combined US-NaOCl treatment. US appears as a promising technique for fresh-cut produce disinfection, but further studies are needed to optimize US treatment to allow important microbial reductions throughout all storage time without compromising lettuce shelf life during refrigerated storage.

Estudo da eficácia de saneantes comerciais de uso doméstico na redução da carga microbiana em alface (Lactuca sativa) crespa in natura

Introduction: Raw hardwood vegetables are possible sources of microbiological contamination and need to be sanitized before consumption. The different sanitizers vary in their ability to reduce microorganisms, and chlorine, in its different forms, is widely used in food for this purpose. Objective: To evaluate the efficacy of three different types of commercial domestic sanitizers in the reduction of microbial load on in natura crisplettuce from conventional cultivation. Method: Five lots of three different chlorine-based sanitizers used for lettuce sanitization were studied. Concentration of free chlorine and the existence of thermotolerant coliforms and Salmonella spp were investigated in the lettuce samples after sanitization. Results: Only one of the evaluated sanitizers obtained free chlorine concentration between 100 and 200 ppm. All lettuce samples showed an absence of Salmonella sp./25 g and 60% of them had no reduction of coliform at 45oC to acceptable evels for the product to be suitable for consumption. Conclusions: The tested products were not effective in reducing the microbial load of lettuce to safe levels, which may be putting the health of the consumer at risk. However, more studies are needed to elucidate issues related to the food hygiene process.

Spectral classification of lettuce cadmium stress based on information fusion and VISSA‐GOA‐SVM algorithm

AbstractIn order to study the qualitative Vis–NIR spectra detection of cadmium stress in lettuce leaves, this article uses data‐level information fusion method coupled with VISSA‐GOA‐SVM algorithm for research and analysis. There were 140 pieces of lettuce leaves under four gradients of cadmium stress, as well as a total of 560 samples of lettuce were used to collect Vis–NIR spectral information. Wavelet transform (WT), first derivative (1st Der) and second derivative (2nd Der) were used to process original Vis–NIR spectral data, respectively. Besides, the data after different pretreatments will be fused in the data‐decision level and used as a new input layer. Principal component analysis (PCA), iteratively retaining informative variables (IRIV), and variable iterative space shrinkage approach (VISSA) were used to reduce the dimensionality of the data layer, respectively. Besides, support vector machine (SVM) was used to establish a classification model. The results showed that the RTD (initial fusion of three data input layers) combined with VISSA‐GOA‐SVM (VISSA combined with grasshopper optimization support vector machine) classification model was the best, and the accuracy of the calibration and prediction were 100% and 98.57%, respectively. Application of Vis–NIR hyperspectral imaging technique to detect cadmium stress gradient in lettuce leaves provided a new method for identifying different heavy metal residues in lettuce.Practical applicationsIt is of great significance to detect different cadmium stress levels through nondestructive testing. In order to effectively implement the rapid and nondestructive testing of lettuce leaves under different cadmium stress levels, Vis–NIR hyperspectral imaging technology coupled with data‐level fusion method was used in this article. In addition, VISSA‐GOA‐SVM model was established to detect cadmium stress level. It confirms that the Vis–NIR hyperspectral imaging technology is a feasible and effective method for discriminating different cadmium stress levels.

Occurrence of pesticides in fruits and vegetables from organic and conventional agriculture by QuEChERS extraction liquid chromatography tandem mass spectrometry

Human exposure to pesticides commands the implementation of food safety control, but few studies have provided a comparative assessment of conventional and organic products. This study set out to examine 22 pesticides in four distinct commodities (lettuce, apples, grapes, and tomatoes) from conventional and organic agriculture available to consumers. A multiresidue procedure based on QuEChERS extraction and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was first validated for its robustness. Suitable determination coefficients (R2 > 0.99) and recoveries generally between 70 and 110% were obtained. Intraday and interday variations were <20% and low matrix effects were noted with sample-to-sample variation. Method limits of detection (LOD) in the overall range of 0.05–2 μg kg−1 were obtained. The validated method was applied to 133 fruit and vegetable samples purchased in Canada, including conventional and organic culture samples. Overall, 47% of the 133 samples had levels above the LOD for at least one pesticide. Neonicotinoid insecticides were detected in all four product types. Imidacloprid (0.08–29 μg kg−1), acetamiprid (0.11–108 μg kg−1), and clothianidin (0.13–141 μg kg−1) were the most recurrent. Atrazine was reported in approximately a third of the lettuce samples (0.25–7.5 μg kg−1). For varieties with samples available from both organic and conventional agriculture, the proportion of insecticide levels > LOD was significantly higher (p < 0.05) for samples from conventional agriculture (9.7%) than from organic agriculture (2.0%). Measured levels were compliant to Canadian Maximum Residue Limits (MRLs), but a thorough human health risk assessment has yet to be conducted for many of these pesticides.

Determination of 20 perfluoroalkyl substances in greenhouse vegetables with a modified one-step pretreatment approach coupled with ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS-MS)

A new rapid modified one-step QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach was developed for the simultaneous determination of 20 perfluoroalkyl substances (PFASs) from samples of cucumber, lettuce, eggplant, tomato, and leek. Several parameters were optimized. Similar pretreatment approaches were employed for comparison; the results verified the satisfactory performance of this new method. The detection limits of this method for the selected matrices ranged from 0.003 to 0.034 μg kg−1, and the method was verified to be satisfactory in terms of precision, accuracy, and matrix effects. 35 greenhouse vegetable samples were determined. PFASs were detected in 26 samples, with perfluorooctanoic acid (PFOA) being detected most frequently and much higher levels of PFBA and PFPeA being found in some samples. The total PFAS concentrations ranged from not detectable to 0.683 μg kg−1. This method could be applied for large scale determination of vegetables to research the migration and accumulation trends of PFASs from the environment to crops in the future.

Novel and Rapid Deep Eutectic Solvent (DES) Homogeneous Liquid–Liquid Microextraction (HLLME) with Flame Atomic Absorption Spectrometry (FAAS) Detection for the Determination of Copper in Vegetables

Novel and fast deep eutectic solvent (DES)-based homogeneous liquid–liquid microextraction (HLLME) was applied for the extraction of copper from vegetable samples followed by flame atomic absorption spectrometry (FAAS). 1,5-diphenyl carbazone (DPC) was used as the chelating agent, and a DES was used as the extraction media. The utilized DES was based on benzyl triphenyl phosphonium bromide and ethylene glycol in a 1:8 mole ratio. The phase separation phenomenon was occurred by changing of sample temperature. Several factors influencing the extraction efficiency were investigated and optimized. Under the optimized conditions, an enhancement factor of 64 was obtained. The limit of detection, based on three signal-to-noise ratio, and limit of quantification were found to be 0.13 µg L−1 and 5.0 µg L−1, respectively. The calibration curve was linear within the range of 5.0–250 µg L−1 with r 2 > 0.9957. Intra- and inter-day relative standard deviations (%) of 2.1% and 2.6% were obtained at the concentration of 25 µg L−1. The accuracy of the proposed method was evaluated by analyzing a tomato leaves certified reference material and the results were to be in agreement with the certified value. Finally, the feasibility of the method was successfully confirmed by determination of copper in spinach, lettuce, broccoli, potato, carrot and parsley samples.

Organic methods of control of the invasive plant Cyperus rotundus L. in culture of Lactuca sativa L. (mimosa var) in an ecological agrosystem

Nut sedge is a weed that releases allelopathic substances in the environment that damage cultivars. This plant is difficult to control and eradicate, causing quantitative and qualitative reductions in the world production of several economically valuable species, among them is roman lettuce (var. mimosa). The objective of this study was to evaluate and compare three biological treatments of lettuce control in an organic agrosystem, determining among them the highest yield of lettuce. The experiment tested the treatments in lettuce cultivation in a consortium with jack beans, sage and soil cover by eucalyptus sawdust. Three replicates were made of each treatment (n=3), and named as C1 (control), C2 (jack beans), C3 (sage) and C4 (sawdust). Ten individuals of lettuce and nut sedge were planted in each plot, and in the C2 and C3 treatments 10 individuals of jack beans and sage were planted, respectively. The quantitative data of all plants, temperature, pH and humidity were measured weekly. After 44 days of the experiment, the lettuce samples were collected and taken to laboratory incubators for drying at ±60°C, obtaining the dry mass. In the C1 (control) treatments there was a growth of 566% of the nut sedge population, in C2 (pork bean) a population increase of 393% and in C3 (sage) a 443% increase of the population. In the C4 plots, where the eucalyptus sawdust cover was used, there was a 64% reduction of the invasive plant. It was concluded that the best method was to cover with eucalyptus sawdust, by reducing the nut sedge population with higher yield of lettuce biomass.

Heavy metal pollution in soils and urban-grown organic vegetables in the province of Sevilla, Spain

ABSTRACTSources of heavy metal pollution in vegetables can be varied. The focus of this study was to determine the factors affecting trace metal pollution in soils and vegetables that are grown on community urban and periurban organic farms in Spain. The results showed that soil and dust deposition affected plant composition more than other anthropogenic sources, such as traffic loads. Lettuce and broad bean samples collected from one urban farm showed high concentrations of crustal metals Fe, Ca, Mn and Cr, which was thought be due to Saharan dust deposition. The build-up of soil Cu concentration, due to the use of Cu-based fungicide over a long term, was observed on the farm where vegetables had been grown over a long period of time. On the same farm, concentrations of Pb in the soil and the vegetables were noted to be at levels that could pose a risk to human health and/or the environment and this was concluded to be due to the random and uncontrolled disposal of demolition waste containing lead-based white paints. The increased risks for consumers due to these different sources of pollution acting simultaneously demonstrated the need for careful selection of urban soils intended for agricultural use. Soil organic matter counteracted Pb availability, hence organic management and intensive use of organic amendments were recommended for urban farms.Abbreviation: SOM- Soil organic matter

Multi walled carbon nanotubes embedded conducting polymer based electrochemical aptasensor for estimation of malathion

The present manuscript deals with the preparation of conducting polymer poly-3,4 ethylenedioxythiophene (PEDOT) and carbon nanomaterials such as carboxylated multi-walled carbon nanotubes (c-MWCNTs) based aptasensor for the detection of malathion organophosphate (OP). For the development of an aptasensor, PEDOT-c-MWCNTs was electropolymerized on the fluoride tin oxide (FTO) sheets by chronoamperometry at a potential of 1 V for 180 s. The aminylated aptamer (Apt) molecules were immobilized on the surface of PEDOT-c-MWCNTs/FTO through covalent linkage. The fabrication of aptasensor was characterized using chemical and electrochemical studies. The comparison of aptasensor with high performance liquid chromatography (HPLC) was done in terms of detection limit. Under all the optimum conditions, the aptasensor displayed 0.5 fM as a detection limit of malathion after 8 min incubation whereas HPLC displayed 8.4 pM. Aptasensor showed high specificity for malathion as there was no elevated electrochemical response with other OPs. The recoveries of malathion from the spiked lettuce sample was obtained both by aptasensor as well as HPLC and the recovery% was found more satisfactory for sensor.

Listeria species as contaminants of lettuce and its resistant genes in Benin city, Nigeria

This study was aimed at determining the level of Listeria contaminants and subsequently detects some resistance genes among the isolated Listeria species from lettuce sold in some vegetable markets in Benin City, Nigeria. Twenty-four lettuce samples were purchased from three vegetable markets in Benin City, Nigeria and examined using standard microbiological methods. Microbial characterization revealed Listeria monocytogenes and L. grayi as the predominant species isolated. Plate count analysis on Listeria selective agar revealed that lettuce sold in Oba market and Forestry market had the highest and lowest mean count of Listeria species 224.00 x 10 2 CFU/g and 83.00 x 10 2 CFU/g respectively. Most (63.75%) of the Listeria species isolates were found to be susceptible to Ofloxacin (5 μg), Ciprofloxacin (10 μg), Streptomycin (10 μg), Gentamycin (10 μg), Pefloxacin (5 μg) whereas species harbouring tetracycline (65%) and erythromycin (60%) resistant genes. The study provides an evidence of the colonization of Listeria species in lettuce sold in Benin City which may pose serious public health threat to the populace. Keywords: Listeria monocytogenes , Listeria grayi , Lettuce, Resistance genes

Tracking plasmid-mediated antibiotic resistance from environmental reservoirs to the food chain

It has been well documented that antibiotic resistance (AR) is a clinical concern that affects both human and animal health but AR in the environment and food-chain is not as well understood. AR bacteria can occur naturally in soil, water and organic fertilizers used in agriculture so there is a risk that AR can pass to humans via the food-chain. This study focuses on lettuce cultivation undergoing four treatments (Normal irrigation water+normal soil, normal irrigation water+manure, UV irrigation water+normal soil, UV irrigation water+manure)to determine the mechanisms by which the AR is transferred to the plants over the growth period of the lettuce (7 time-points – week 0 to week 6). Plasmids (n=318) have been isolated from irrigation water (n=36), soil (n=45) and lettuce (n=42) samples using the exogenous isolation method for week 0 and week 6 initially. Antibiotic susceptibility testingto amikacin, cefotaxime, ciprofloxacin, imipenem, kanamycin, tetracycline has been carried out. Multi-drug resistance profiles were established for soil taken at timepoint 0 and lettuce taken at timepoint 6. Extracted plasmid DNA was sent for metagenomic analysis to determine which genes are involved in the transfer of AR at the interfaces. The results of the sequencing showed that there are multiple AR genespresent, including Tet, Sme, Cmy, Oxa and ANT(4’)-Ib, that confer resistance to bacteria. The identification of multi-drug resistance in soil and lettuce samples is concerning and highlights the need to determine the mechanisms leading to antibiotic resistance in food.

Effect of Harpin protein as an elicitor on the content of phenolic compounds and antioxidant capacity in two hydroponically grown lettuce (Lactuca sativa L.) varieties.

Harpin protein was used as an elicitor in green (butterhead) and red (oak leaf type) varieties of hydroponically grown lettuce (Lactuca sativa L.). Its impact on polyphenolic content and antioxidant capacity was evaluated. Harpin protein was sprayed three days before harvesting in concentrations of 45, 60, and 120 mg/L. Green lettuce samples showed a positive response to Harpin by significantly increasing its phenolic content from 12 (control) to 16.43 mg gallic acid equivalents (GAE)/100 g dry weight (DW) (120 mg/L Harpin treatment) which means a 36.9% increase. Chlorogenic acid was the only phenolic compound that increased its concentration after lettuce induction with Harpin treatment. Antioxidant capacity, evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH˙) and ferric reducing antioxidant power (FRAP) methods, also showed a significant increase (46.5 and 64.3%, respectively) in Harpin-treated green lettuce. The red lettuce variety showed none or a negative response to Harpin treatment for all parameters evaluated. These results show that elicitation may be an effective strategy to enhance phenolic content in lettuce varieties.

Comparison of Organic and Conventional Food and Food Production Part V: Human Health – Pesticide Residues

The present report is based on data from the 2010 EFSA Report on pesticide residues in food, the Norwegian monitoring programmes 2007-2012 and data from peer reviewed literature and governmental agencies. It is a challenge to perform quantitative estimates and comparative studies of residue levels due to large variation in the measured levels, and the large number of different pesticides present in the samples. Thus, the focus is on the frequency of observed contaminations in relation to regulatory limits and to present examples to illustrate the variation in residue values and number of detected substances. &#x0D; Pesticide residues in conventional and organic products:&#x0D; Of the 12,168 samples (plant- and animal products) in the 2010 EU-coordinated programme, 1.6% exceeded the respective maximum residue level (MRL) values, and 47.7% had measurable residues above the limit of quantification (LOQ), but below or at the MRL. Of the 1168 samples analysed in Norway in 2012 (from both imported and domestic products), 1.9% exceeded MRL and 53% contained measurable pesticide residues. Direct comparison of these values is however not possible, since they contain different types of food samples, and are analysed for a different number of pesticides.&#x0D; When organic and conventional samples from fruit, vegetables and other plant products in the 2010 EU-coordinated programme were compared, 4.2% of the conventional and 1.0% of the organic samples exceeded the MRL values, while 43.2% of the conventional and 10.8% of the organic samples had measurable residues below or at the MRL value. Most of the pesticide residues detected in organic samples are not permitted for use in organic farming. &#x0D; Of the 624 organic samples analysed in Norway 2007 - 2012, 0.2% (one sample) had residues exceeding MRL, while measurable residues were detected in 1.8% of the samples (11 samples).&#x0D; Conventional products were often found to contain different pesticides while most organic samples were found to contain few or only one type of pesticide. &#x0D; Lack of data on pesticide residue levels of organic samples in the EU-coordinated programme, and few Norwegian samples do not allow for a quantitative comparison of pesticide residue levels in organic and conventional samples. Comparative estimation of pesticide residues faces a number of challenges and uncertainties. However, it seems unquestionable based on available data that organic plant products contain fewer and substantially lower amounts of pesticide residues than conventional products.&#x0D; Health risk associated with pesticide residues:&#x0D; The general level of pesticide residues in both conventional and organic food is low, and well below what is likely to result in adverse health effects. This conclusion is based on the comparison of estimated dietary exposure with toxicological reference values i.e. acceptable daily intake (ADI) for chronic effects, and acute reference dose (ARfD) for acute effects. The finding of pesticide residues that exceeds established regulatory limits in a minority of tested samples is not considered to represent a health risk.&#x0D; When dietary exposure that was estimated in six different food commodities in the 2010 EUcoordinated programme was compared with their relevant reference values, EFSA concluded that for 79 of 18243 conventionally grown fruit and vegetable samples, a short-term acute consumer health risk could not be excluded. The conclusion was based on the exceeding of ARfD. None of these 79 samples were organic. It is important to also consider that the exceeding of the acute reference value only occurred in 0.4% of the samples and that the scenario used for acute intake assessment is conservative, suggesting that the toxicological implications are limited. This is also reflected in the chronic exposure assessment, where none of the samples were found to exceed the toxicological reference value ADI. &#x0D; Dietary exposure assessments on the basis of Norwegian samples of apples, tomatoes, carrots, strawberries and lettuce did not show an exceeding of any toxicological reference value. &#x0D; Combined exposure and cumulative risk assessment of pesticide residues:&#x0D; No generally accepted methodology is at present established for cumulative risk assessment of combined exposure to pesticide residues. Available data suggest however that combined exposure is not likely to result in increased human health risk.

Human-health probabilistic risk assessment: the role of exposure factors in an urban garden scenario

Despite the environmental, economic and social benefits of urban gardening, there are also potential threats to human health due to the possible enrichment of urban soils in anthropic contaminants. As of today, our knowledge about the influence of population characteristics and local habits of garden use on risk estimates is incomplete. This work studies the effect of the variability of local exposure factors on the output of a risk assessment in an urban garden scenario through a probabilistic risk assessment (PRA) and an uncertainty analysis. A total of 24 soil samples and 23 samples of lettuce were collected in six urban gardens. Trace element concentration were analysed in both matrices with an atomic absorption spectrometer. Relevant exposure factors were characterized by onsite and online surveys. The results showed that the use of widely accepted, default exposure values overestimate the risk when compared with the result of an assessment with local information. In this study, the 95th percentile of the risk distribution did not exceed human health unacceptability thresholds. Exposure frequency and vegetable consumption rates were the variables to which the risk outcome was most sensitive. This study highlights the importance of characterizing urban gardeners’ local activity patterns when assessing the acceptability of urban agriculture in terms of human health.

Application of deep brief network in transmission spectroscopy detection of pesticide residues in lettuce leaves

AbstractTo realize the quick, nondestructive detection of pesticide residues in lettuce leaves, a new method based on deep brief network (DBN) combined with near‐infrared transmission spectroscopy, was studied in this article. Two kinds of pesticide residues (fenvalerate and triazoline) and distilled water were sprayed on the surface of lettuce leaves, respectively. In addition, near infrared transmission spectroscopy was used for collecting spectral data of 240 lettuce samples. Furthermore, Savitzky–Golay combined with multiplicative scatter correction was used to denoise the raw spectral data. Then, after preprocessing spectral data, DBN was used to extract features and identify kinds of pesticide residues in lettuce leaves. Moreover，successive projection algorithm (SPA) was used to select characteristic wavelengths. After all, support vector machine (SVM), PLS‐DA, and k‐nearest neighbor were carried out to establish classification models based on full spectral data, data extracted by DBN and data extracted by SPA. Consequently, DBN–SVM performed best and the accuracy of training set and test set reached 98.89 and 95.00%, respectively. Hence, the method of near infrared transmission spectroscopy combined with DBN–SVM is practical for the qualitative analysis of pesticide residues in lettuce leaves.Practical applicationsUsing near infrared spectroscopy could detect the kinds of pesticide residues in lettuce leaves quickly and effectively. A new method involving deep brief network (DBN) was proposed to extract the features of spectral data. Results in this study showed that the DBN is feasible and effective for building classification models of different pesticide residues.

A study on the prevalence of heavy metals, pesticides, and microbial contaminants and antibiotics resistance pathogens in raw salad vegetables sold in Dhaka, Bangladesh

The presence of undesirable heavy metals, pesticide residues, and microbial contaminants in fresh produces is a worldwide public health concern. This study was undertaken to evaluate the residual pesticides (Diazinon, Malathion, Cypermethrin, Dimethoate, Quinalphos, and Chloropyrofos), heavy metal contamination (Pb, Cd, and Cr), and microbiological quality and safety of 4 common raw salad vegetables (RSVs) samples from different local markets in Dhaka. Results showed the presence of heavy metals residues were within the acceptable limits of local and international standards. None of the above-mentioned pesticides were found in tomato and cucumber samples but presence of Dimethoate was noticed in 13 coriander samples (12.94–158.3 μg/kg) and 7 lettuce samples (9.6–74.8 μg/kg) exceeding the maximum permissible limit of EU guideline. The microbiological analysis showed irrespective of RSV types, total aerobic bacteria was present in higher number (4.0–7.0 log CFU/g), whereas 3.36–5.57 log CFU/g coliform count was recorded. In comparison with retail markets, lower level of total aerobic, and coliform bacterial presence was observed in the samples collected from sophisticated shops, but presence of E. coli and Salmonella spp. were evident in more than 60% samples in these shops. However, 50% and 33% samples from wholesale and retail markets respectively were noticed to be contaminated with Staphylococcus spp. Irrespective of RSV types, isolated E. coli were found resistance to 2–5 different antibiotics, where Salmonella spp. isolated from cucumber and coriander leaves showed resistance against 4–8 different antimicrobials. Therefore, the study results demonstrated that, the presence of residual pesticides, multidrug resistant E. coli and Salmonella spp. in the RSV samples posing concern when consumed raw. The regulatory bodies are expected to monitor and ensure the overall quality standards are in place and practiced by food producers and marketers responsible for handling and distribution of RSVs.