In one study, the tested samples were found to be 100% contaminated with low but measurable amounts of pesticideresidues. Among the four major chemical groups, residue levels of organophos- phorous insecticides were the highest, followed by carbamates, synthetic pyrethroids, and organo- chlorines. About 32% of the samples showed contamination with organophosphorous and carbamate insecticides above their respective MRL values. The monitoring study indicated that though all the vegetable samples were contaminated with pesticides, only 31% of the samples contained pesti- cides above the prescribed tolerance limit. Samples of vegetables collected at beginning, middle, and end of seasons were analyzed for organochlorine levels. Maximum pesticideresidues were detected in cabbage (21.24 ppm), caulifl ower (16.85 ppm), and tomato (17.046 ppm), collected at the end of season, and okra (17.84 ppm) and potato (20.60 ppm), collected at the middle of season. The organo chlorine pesticide (OCP) residue levels in majority of the samples were above the maximum acceptable daily intake (ADI) prescribed by WHO, 1973. Twelve most-commonly used pesticides were selected to study the residual effects on 24 samples of freshly collected vegetables. Most of the samples showed the presence of high levels of malathion. Furthermore, DDE, a metabolite of DDT, BHC, dimethoate, endosulfan, and ethion were also detected in few samples. However, leafy vegetables like spinach, fenugreek, and mustard seem to be the most affected. Radish also showed high levels of contamination. Vegetable samples collected at harvest from farmer’s fi elds around Hyderabad and Guntur recorded HCH residues above the MRL (0.25 ppm). However, residues of DDT and cypermethrin were found to be below the MRL (3.5 and 0.2 ppm, respectively), and man- cozeb residues were above the MRL (2 ppm) only in bitter gourd. Furthermore, residues of HCH, DDT, aldrin (including dieldrin), endosulfan, and methyl parathion in vegetables of Srikakulam were below the MRL. Detectable levels of residues of commonly used pesticides were observed in tomato (33.3%), brinjal (73.3%), okra (14.3%), cabbage (88.9%), and caulifl ower (100%) samples. How- ever, the levels of concentrated pesticideresidues were lower than the MRLs prescribed. In a study to estimate various OCPs in different food items collected from 10 localities in Lucknow city, wheat fl our and eggs were found to contain maximum concentration of OCP residues. Furthermore, the estimates of dietary intake of total HCH (1.3 g) and lindane (0.2 mg) was about one-and-a-half times higher than that of the ADI, and 100 times the values reported from the United Kingdom and the United States. Out of 400 food stuffs tested, 23.7% were positive for pesticideresidues. Higher rates were found in animal products (30%), cereals and pulses (26.3%), and vegetables (24%).
Study in this paper is based on distributions of pesticides in surface water and ground waters for a period of 2 year (from 2012-2013) from 18 districts of Haryana. Monitoring and assessment of pesticide contamination in farmland water has become a necessity. Particularly, there is need to determine, quantify and confirm pesticideresidues in water for both research and regulatory purposes. The pesticides are analyzed by gas chromatography Mass spectrometry. [10-12]
A recent inventory on pesticide use within Uganda  has shown a 6% re- sponse use of dieldrin among the commonly used pesticides in the country, sug- gesting that the pesticide was still being used by farmers to control various pests. Slow degradation of pesticides in the environment and extensive or inappro- priate use by farmers can lead to environmental contamination of water, soil, air, several types of crops and indirectly, humans  . Organochlorine pesticides can enter the environment after pesticide applications, disposal of contaminated wastes into landfills, incinerator emissions or runoff, or releases from manufac- turing plants that produce these chemicals . OCPs are harmful to
An awareness of the expected variability of residues is necessary. If the data truly reflect the range of conditions, application methods, seasons and cultural practices likely to be encountered commercially, then considerable variation in the resulting residue levels is expected. Analysis of supervised trials evaluated by the JMPR between 1997 and 2007 revealed that the coefficient of variation of residues between fields can sometimes be over 110%. Where copious data are available, consideration of the spread and variability of the residues helps to avoid misleading interpretations of small differences in estimates of the maximum level. Where only limited data are available, which is the case for the majority of supervised data sets (most frequently 8–9) 28 actual variability may be underestimated and judgement is required to arrive at an estimate that is realistic, practical and consistent. It is not a criticism to say that the data are widely spread and variable. If results have been obtained at a number of places over some years they are likely to be a better approximation to commercial practice and will be widely spread. In addition to the variability of residues within a confined area which can be considered uniform regarding climate, agricultural practices, pest situation and use recommendations, there may be an even greater variation of residues among areas of widely differing conditions, e.g., countries being in temperate, Mediterranean and tropical zones. The differences in use conditions can be so large that they result in different residue populations (see section 6.4 “Combining of data populations”).
A survey was conducted in intensive vegetable growing area in the Narsingdi district of Bangladesh regarding pesticides used by farmers on three major vegetables like eggplant, cauliflower, and country bean. On the basis of questionnaires, 23 farmers were interviewed and it was noted that fourteen pesticides belonging to different groups were found to be commonly used on the selected vegetables by the respondent farmers to control the major pests. In two selected locations of Narsinghdi 8.33 to 45.00 percent farmers were recorded to apply different pesticides every day and in some cases even twice in a day on vegetables. A total of 42 samples were collected from fields and markets and multiple pesticide residue analysis was done by Gas Chromatography (GC) with Flame Thermionized Detector (FTD) and Electron Capture Detector (ECD). Out of 42 samples, 27 had pesticide residue. Among these 27 samples, 14 samples had pesticideresidues above the Maximum Residue Limit (MRL). The detected pesticides were Diazinon, Malathion, Quinalphos, Fenitrothion, Cypermethrin, Fenvalerate and Propiconazole.
Supercritical fluid extraction (SFE) is suitable for extraction of target compounds from relatively dry samples. Use of supercritical fluid with high isolation and purification effect is utmost advantage of this technique. Supercritical fluid can efficiently diffuse through matrix as a gas and effectively dissolve analytes like a fluid without any solvent load (Lehotay, 1996). This prevents need of an exuberant evaporation step required in many traditional methods. Method development is more difficult in SFE since more parameters need to be optimized. It also has disadvantage of manual operation in comparison to fully automated methods such as PLE (refer PLE). SFE results avidly depend on selectivity of matrix and nature of analyte, optimisation of extraction condition is hence advocated with each new class of pesticide or new matrix (Lehotay, 1996). Better recovery of several analytes in selective food matrices than others has been reported by Rissato and colleagues (2005). At temperature condition 70 °C, extraction pressures 44.935 MPa, and flow rate of 1.5 ml min-1 for SFE; pesticides not amountable by classical extractions such as imazalil, tebuconazole, triadimefon, chlorpyrifos and cypermethrin could easily be determined. Control of simple variables such as temperature, pressure and solvent polarity allow extension of extraction range of SFE. At lower pressures, constant temperatures are more efficient for less polar, lighter compounds, whereas higher pressures can extract large, more polar analytes. Elevated temperatures usually improve recoveries of compounds mainly due to better desorption from matrix. As an exception, decomposition of captan, captafol, chlorthalonil and diclorofluanid have been reported at higher temperatures yielding recoveries <70% (Ono et al., 2006). It is proposed that pH adjustments using phosphoric acid can be done for such problematic compounds. Din et al., 1997 investigated the use of modifiers, ion-pairing agents in an attempt to improve sulphonamide recoveries at lower density. Recoveries of the ionic metabolites were increased by up to 72% when employing tetramethylammonium hydroxide for ion pairing in-situ with SFE. Figure 1, lists several strategies involved to improvise SFE performance.
Acceptability of analytical method performance–extended method validation 59. A quantitative analytical method should be demonstrated at initial and extended validation as being capable of providing mean recovery values at each spiking level and for at least one representative commodity from each relevant group within the range 70–120%, repeatability RSD r and within laboratory reproducibility RSD wR ≤ 20%, for all compounds to be sought using the method In certain justified cases, typically with multiresidue methods, recoveries outside this range may be accepted. Where the method does not permit this, and there is no satisfactory alternative, the relatively poor mean recovery must be considered before taking enforcement action. Exceptionally, where recovery is low but consistent (i.e. demonstrating good precision) and the basis for this is well established (e.g. due to pesticide distribution in partition), a mean recovery below 70% may be acceptable. However, a more accurate method should be used, if practicable. Within- laboratory reproducibility (RSD wR ) should be ≤ 20%, excluding any contribution due to sample heterogeneity.
Our study is the first to compare vegetable pesticideresidues across different domestic markets to unravel evidence of potential public health risks. Irrespective of the market source, Thompson et al. (2017) showed the occurrence of organochlorines in 13 African countries not only in vegetables but also in human breast milk and blood serum. This calls for an urgent need for inter- vention to prevent insurmountable pesticide related public health burdens on already resource constrained African governments. Higher residue contamination on samples from the farms may be because on-farm sales are made more immediate to spraying time, not allowing for pesticide degradation in time. It could also be due to high frequency of application or higher than recom- mended dosages (Ngowi et al. 2007; Williamson et al. 2008; Machekano et al. 2019) or a combination thereof. Moreover, high residues reported here, may also be due to the intentional or unintentional failure to adhere to recommended pesticide withdrawal periods (as in e.g. Williamson et al. 2008; Ngowi et al. 2007; Machekano et al. 2019) owing to lack of knowledge and market compe- tition (Williamson et al. 2008; Machekano et al. 2019). Withdrawal periods for some of the pesticides detected here are high, e.g. 14 days for imidachloprid and 21 days for both methamidophos and chlorantraniliprole. How- ever, Machekano et al. (2019) reported that 71.6% of farmers waited for a mean ~ 10 days, indiscriminate of the applied active ingredient. Moreover, some pesticides, e.g. fenvalerate, are not recommended for use in crucif- erous crops. Nevertheless, these have been reported to be used indiscriminate of the crop type (see Machekano et al. 2019). Thus, existing regulations on pesticide mis- use are not being observed, and this malpractice exposes the public to indirect ‘pesticide’ consumption through highly contaminated ‘ fresh ’ produce as evidenced by our results.
proved adequate for monitoring FEN residues in toma- toes and pointed out selectivity and easy regeneration as well as its low cost. Other organophosphorus pesticide extensively used for crop protection and tree treatments, as an alternative to highly persistent ones, is dichlorvos. These compounds are highly toxic since they can cause protein adduction, are suspected to be mutagenic and carcinogenic and are endocrine disruptors . A sensi- tive and reliable method for their separation and quanti- fication in foods is mandatory. Dichlorvos is present in complex samples at trace levels requiring, for its analysis, an effective extraction and preconcentration step. A MISPE coupled to HPLC, for determination of trace di- chlorvos residues in cucumber and lettuce samples has been proposed; a novel imprinted functional material, by a molecular imprinting technique using a room tempera- ture ionic liquid-mediated template, was developed, the final showed improved stability, good selectivity and high adsorption capacity for dichlorvos, and proved to be more suitable for SPE than C18 . Regarding syn- thetic pyrethroid pesticides, MISPE can offer a reduction in the extensive clean up steps currently employed in the analysis of composite diet samples, while decreasing so- lvent consumption and increasing selectivity. Particularly when high fat matrices are considered, the complete ex- traction of pyretroid pesticides is usually accompanied by the simultaneous extraction of fatty material; hence MISPE appears as a good way around. Three parallel approaches have been studied  for the development of MIP for pyretroids in composite diet samples: urea based MIPs, acrylate based MIPs and divinylbenzene based MIPs, the hydrophobic imprinting approach, pre- sented the best results for these samples. Benzimidazoles, and specially thiobendazole (TBZ), are among the most commonly used postharvest systemic fungicides for the control of diseases during fruit and vegetable storage and distribution. Maximum residue limits (MRLs) establi- shed for benzimidazoles are very low, analytical methods able to detect TBZ at trace levels are needed. The com- bination of molecular imprinting and capillary electro- chromatography (MIP-CEC) has been, for the first time, studied and successfully demonstrated, for citrus samples . The use of MIPs, not as a sorbent for solid phase extraction, but as selective stationary phases, in electro- chromatographic separations was proposed. A MIM (molecularly imprinted monolith) was developed to act as stationary phase for capillary electrochromatography, using the template molecule (TBZ), the functional monomer (MAA), the cross-linker (EDMA—ethylene glycol dimethacrylate) and the initiator (AIBN—2-2’- azobisisobutyronitrile) dissolved in a toluene: iso-octane (96:4) solution, that acts as porogen agent. The use of MIPs, either as a sorbent for solid phase extraction or as
subgroups. As such, efforts were not made to assess acute toxicity risks from pesticide residue exposure to determine the likelihood that a single person’s dietary exposure to a pesticide could exceed the acute RfD on a given day. More sophisticated risk assessment methods, using probabilistic models to study variability in pesti- cide residue levels and food consumption data, would be needed to achieve this task. Such approaches are com- monly performed by the EPA, however, and pesticides are not allowed to be registered for use unless EPA con- cludes that the pesticides pose a “reasonable certainty of no harm” when considering potential increased suscepti- bility for specific population subgroups, aggregate expos- ure to pesticides (water, food, and residential exposure) and cumulative exposure to families of pesticides posses- sing common mechanisms of toxicological action such as the organophosphate insecticides. For acute pesticide exposure, a pesticide poses a “reasonable certainty of no harm” when it can be established that acute exposure for sensitive population subgroups has at least a 99.9 % chance of being below the acute RfD (EPA 2014).
Analysis of PHI of chlorpyrifos showed that the amount of chlorpyrifos residues vary inversely with time. The levels on the first day were at their highest but decreased with time to very low levels on day 16. This decrease could be attributed to degradation of the active ingredients over time, washing off, metabolism by the plant and biotransformation by photolysis, oxidation, reduction and hydrolysis (Pilger, 2007. I.U.P.A.C, 1996). The amounts of chlorpyrifos obtained from the vegetables analyzed were almost equal to those obtained during the last days of PHI levels. This shows that most of the residues obtained occur when vegetables are harvested before their recommended PHI. This is in line with studies done by Gambarcorta et al, (2005) which showed that pesticides after spraying degraded by first order kinetics resulting in a decrease of levels with time.
Colloidal clays attracted much attention in the recent years and widely used to prepare chemically modified electrodes for the electrochemical analysis . It is abundant in nature, environment friendly and inexpensive. Recently, clay modified electrodes were used for the analysis of some toxic compounds such as pesticides  and nitro phenols . Chemical method is a versatile technique to prepare a gemini surfactant-intercalated clay-modified electrode for the determination of methyl parathion . Manisankar et al  have reported heteropolyacid montmorillonite clay- modified glassy carbon electrode for the determination of isoproturon, carbendazim and methyl parathion through SWV analysis and achieved the limit of detection value of 1, 10 and 20 ng mL -1 for isoproturon, carbendazim and methyl parathion respectively. Organo-smectite clay based composite was fabricated for the electro-oxidation of p-nitrophenol . In this composite electrode, when the loading of the benzyltrimethylammonium (BTMA) cation increases the oxidation peak current of p- nitrophenol simultaneously decreases. Xing and Willemure  have reported two types of clays based on cobalt smectites such as [(Si 8.05 )(Co 5.58 )O 20 (OH) 4 Na 0.66 and [(Si 7.93 )(Co 5.92 )O 20 (OH) 4 ] Na 0.42 .
There have been concerns over indiscriminate use of pesticides by farmers to grow vegetables especially for local markets since there are no guidelines on Maximum residue levels. This study was done to determine the concentration of cypermethrin and lambda-cyhalothrin pesticideresidues in Collard (Brassica oleracea var. acephala) Tomatoes (Solanum lycopersicum) and swiss chard (Beta vulgaris subsp. cicla). The samples included both organic and conventional vegetables that use chemical pesticides. Experimental study design was used which involved laboratory analysis of the samples. Sample extraction was done using AOAC official method 2007.01 known as Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. The method involves use of Acetonitrile, sodium chloride and anhydrous magnesium sulphate for extraction. Clean-up was done using dispersive-solid phase extraction method using Primary-Secondary Amine and anhydrous magnesium sulphate. Residuesanalysis was done using Reverse- phase High Performance Liquid chromatography. Peak areas of the curves were calculated using Motic Images plus 2.0 and data analysis was done using SPSS 22. Recovery rates of pesticide ranged from 87.78% to 97.93% for cypermethrin and 90.65% to 95.72% for lambda-cyhalothrin. The results indicated that organic vegetable samples had pesticideresidues below detectable levels while conventional vegetable samples had levels ranging from 2.495mg/kg to 0.238mg/kg for cypermethrin and 0.352mg/kg to 0.119mg/kg for lambda-cyhalothrin. The residues of both pesticides were above the recommended, this is likely to cause negative health effects such as uncoordination, whole-body tremors and seizures. This indicates that conventional vegetable consumers are exposed to pesticideresidues. Farmers should strictly adhere to good agricultural practice to reduce pesticideresidues.
(b) The pesticide is authorised for the use on the concerned crop, but was not used on the sample analysed because the crop disease or the pest did not occur or because alternative products were used; (c) The pesticide was used, but due to its degradation the residue concentration declined to a concentration which could not be quantified with the analytical method used in the control laboratory. While in case (a) and (b) the sample should be considered as free of the respective residue, in case (c) traces of the pesticide may be present on the crop which should be considered in the consumer risk assessment. In its scientific opinion on risk assessment for the triazole pesticides, the EFSA PPR Panel highlighted that the methods for handling non-detects (ND) can have a great impact on the extent of the estimated exposure, in particular when using deterministic models. The Panel made several proposals how to handle non-detects (assume ND samples as being zero, treat them as containing the full LOQ or treat them as containing a concentration between zero and the LOQ) and recommended to perform sensitivity analysis to assess the impact of the different assumptions. In its guidance on the use of probabilistic methodology for modelling dietary exposure to pesticideresidues (EFSA, 2012b), the Panel proposes to treat all samples with residues below the limit of reporting as true zeroes or as containing residues at the level of the limit of reporting in the optimistic and pessimistic runs of the basic assessments respectively. The same assumptions could be considered in the deterministic assessments. A refined approach is to take into account the percentage of crops non- treated as being a true zero. However, as reliable data on the use pattern of the individual chemicals are not available, this option is not easy to be implemented in practice (EFSA, 2009).
During the last few decades numerous research efforts to identified and adverse health affect the environment fate of persistent organic populants (Pops) have resulted in a variety of field method for the sampling and analysis of vegetables. The roles of organochlorine pesticides have been very vital in public health and agriculture production in developing countries including India. Further the enormous uses of organochlorine pesticides (OCPs) in developing countries have been of serious concern because of there persistent in nature. Large amount of pesticide are used in agriculture sector and public health programmers every year [1,2].Continuous use of OCPs lead to there presence in water, soil, air, crop plant and biological tissue. A multi residue method for determining pesticideresidues in large no of vegetable samples was studied .Although pesticide residue analysis has been done in several food/product [4-5]However, pesticideresiduesanalysis in vegetables was carried out in recent years .
done in Wumbei et al. (2018) and Wumbei et al. 2019.
Pesticides residue data of Wumbei et al. (2018) and Wumbei et al. (2019) were pooled for the consumer exposure assessment. This was done by calculating the EDI i.e. chronic exposure. The residues of each pesticide were mostly below the LOD. Therefore, in the dietary exposure assessment, the upper bound scenario, also known as the pessimistic was adopted. The exposure was compared with the toxicological limits i.e. ADI of the pesticides. Three approaches were adopted for the exposure assessment, i.e. the deterministic, the simple distribution and the probabilistic, as prescribed by the European Food Safety Authority (EFSA 2012). Fenitrothion and fenpropimorph were assessed deterministically and probabilistically and the rest were assessed by simple distribution. An independent t- test was conducted to compare the estimated dietary exposure of the farmers to the two pesticides derived from the probabilistic and deterministic approaches.
However, since these pesticides act through inhibition of acetylcholinesterase (AChE), they also represent a risk to human health. For several years, some researches have shown that excessive exposure to pesticides can lead to various diseases [5, 6]. Rapid detection of pesticides was more and more necessary due to their toxicity, persistence and stability . The implications of pesticideresidues for human health and the environment were reviewed in the literatures [8-10]. Therefore, for the sake of food safety and environment protection, it is of great importance to find ways to rapidly estimate the level of grain contamination with pesticideresidues and the risk these residues pose to human and animal health [11–13]. For this reason, the detection technology and method of pesticideresidues remaining on the food were described [14-17]. Numerous analysismethods such as gas chromatography–mass spectrometry (GC–MS) [18-20] and liquid chromatography–mass spectrometry (LC–MS) [21-23], capillary electrophoresis (CE) [24-26], flow injection immunoanalysis and fluorimetry  have been developed for pesticidesresidues detection. The QuEChERS [28-30], pressurized liquid extraction (PLE) [31, 32] and liquid–solid extraction (LSE) [33, 34] were mainly used concerning the extraction procedure for pesticides which have been described and reviewed extensively in the literatures [35, 36].
Brinjal is the most popular vegetable in India, and state of Andhra Pradesh is third most important growing Brinjal producing 1.615 M mt with a share of 12% (NHB, 2013) during 2012-13. In India, about 13-14% of the total pesticides used in agriculture are used for fruits and vegetables covering only 3% of the cropped area. Repeated application of pesticides on vegetables often results in the buildup of their residues. Surveys carried out in the country indicated that 50-70% of vegetables are contaminated with insecticide residues).Studies on farm gate monitoring of vegetables carried out in different places revealed contamination mostly with organophosphorous and synthetic pyrethroids insecticides, indicating clearly the changes in the usage pattern from organochlorine to other groups of pesticides.
Of course, this study was referenced to the methods of pesticideresidues in drinking water exposure to human health risk assessment in USEPA, and we only considered the exposure way of water intake average, and other exposure ways, such as food intake, swimming, bathing, and skin exposure pathway, were out of consideration. The reference dose selection, ethnicity, living habits, and the mechanism of various pesticides are different because of the lack of exposure parameter standards in China. Therefore, there may be some bias in the results of this evaluation   . The comprehensive study of environmental ex- posures to pesticides, including food and water intake, skin and respiratory ex- posures, is needed in the further.
The USDA’s Pesticide Data Program (PDP) has generated high quality and extensive data on pesticides in the US food supply . Established in 1991 to support more accurate pesticide dietary risk assessments by the Environmental Protection Agency (EPA), the PDP annually selects a range of fresh and processed foods, focusing on those that make up a significant share of the diets of infants and children and which often contain pesticideresidues. Samples are selected to be representative of market shares by country of origin, and within the U.S., by state. In addition, PDP sample records include the following market claims: “organic product,” “pesticide free,” “IPM-grown,” and “no claim.” The PDP annually reports the levels of all pesticide parent compounds, and selected metabolites and isomers, found above applicable limits of quantification (LOQs). The period of study of 2002–2011 was selected based on implementation of the final NOP rule in the last quarter of 2002. Operations were assumed to be largely in compliance with NOP-related pesticide use provisions for the entire year of 2002 prior to full implementation on 22 October. Supplemental Table 1 contains the raw data supporting this analysis. The table encompasses 1,168 pesticideresidues detected in organic food samples tested by PDP between 2002 and 2011. Several data points appear in the Supplemental Table on each residue-food combination including the food group, year country of origin, whether the residue is a post-harvest fungicide, a legacy chemical, or organic allowed, the residue level reported, the tolerance level, the “Action Threshold” (5% of the tolerance), and dietary risk index values.