High Levels Of Pesticide Residues Research Articles

Detection of Hydrogen Ions Resulting from the Inhibition of Acetylcholinesterase Using Indium Tin Oxide-Coated Nanostructures for Pesticide Sensing

The neurotransmitter acetylcholine (ACh) is hydrolyzed by acetylcholinesterase (AChE) into acetic acid and choline to terminate synaptic transmission (1). Organophosphorus (OPs) found in pesticides induce toxicity in organisms by irreversibly binding to AChE, leading to the phosphorylation of the serine residue at the active site. ACh cannot undergo hydrolysis by the phosphorylated enzyme, resulting in excessive stimulation of nerves and muscles, akin to a nerve agent (2). Our objective is to develop a rapid detection tool for determining the levels of pesticide residues in dairy products. In this study, we measured the release of hydrogen ions (H+) resulting from the hydrolysis of ACh by AChE, serving as an indirect method to evaluate the inhibitory effect of OPs on AChE. To detect the signals of H+ released during ACh decomposition, we used ITO-coated nanostructures modified with 3-aminopropyl trimethoxysilane (APTMS) as a sensing substrate integrated into the extended gate of a field-effect transistor (EGFET) biosensor. The amino group at the end of APTMS can bond with H+. By monitoring the changes in electrical signal from the EGFET biosensor, it is possible to know the concentration of H+ in the solution. The output characteristics (Id-Vd) of the APTMS-modified ITO-VASiNW EGFET were measured using ACh solutions at different concentrations. A correlation was observed between Id and ACh concentration within the tested range, exhibiting a sensitivity of 0.016 mA1/2 / mM and an R2 value of 0.9. A lower concentration of H+ indicates a more pronounced inhibitory effect on AChE by OPs and suggests higher levels of pesticide residues. References (1) Colović, M. B., Krstić, D. Z., Lazarević-Pašti, T. D., Bondžić, A. M., & Vasić, V. M. (2013). Acetylcholinesterase inhibitors: pharmacology and toxicology. Curr Neuropharmacol, 11(3), 315-335.(2) Rajagopalan, V., Venkataraman, S., Rajendran, D. S., Vinoth Kumar, V., Kumar, V. V., & Rangasamy, G. (2023). Acetylcholinesterase biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine neurotransmitter: A literature review. Environmental Research, 227, 115724. Figure 1

A new method based on melatonin-mediated seed germination to quickly remove pesticide residues and improve the nutritional quality of contaminated grains.

In the present study, we attempted to use melatonin combined with germination treatment to remove pesticide residues from contaminated grains. High levels of pesticide residues were detected in soybean seeds after soaking with chlorothalonil (10 mM) and malathion (1 mM) for 2 hours. Treatment with 50 μM melatonin for 5 days completely removed the pesticide residues, while in the control group, only 61-71% of pesticide residues were removed from soybean sprouts. Compared with the control, melatonin treatment for 7 days further increased the content of ascorbic acid (by 48-66%), total phenolics (by 52-68%), isoflavones (by 22-34%), the total antioxidant capacity (by 37-40%), and the accumulated levels of unsaturated fatty acids (C18:1, C18:2, and C18:3) (by 17-30%) in soybean sprouts. Moreover, melatonin treatment further increased the accumulation of ten components of phenols and isoflavones in soybean sprouts relative to those in the control. The ability of melatonin to accelerate the degradation of pesticide residues and promote the accumulation of antioxidant metabolites might be related to its ability to trigger the glutathione detoxification system in soybean sprouts. Melatonin promoted glutathione synthesis (by 49-139%) and elevated the activities of glutathione-S-transferase (by 24-78%) and glutathione reductase (by 38-61%). In summary, we report a new method in which combined treatment by melatonin and germination rapidly degrades pesticide residues in contaminated grains and improves the nutritional quality of food.

PRESENCE OF INTERNATIONALLY BANNED PESTICIDES IN DOMESTIC PERUVIAN QUINOA DURING COVID-19 PANDEMIC

The global showcase for the promotion of the Andean grain quinoa (Chenopodium quinoa Willd.) resulted in a rapid increase in international demand, which has had a direct impact on Peruvian food safety. The excessive use of pesticides results in high levels of pesticide residues in food, causing both environmental and health problems in the population. The objective of this article was to analyze if residues of internationally banned pesticides were present in the quinoa consumed by Peruvians during the COVID-19 pandemic. Twenty-seven different brands of packed white quinoa (10 sold as organically certified and 17 sold as conventional) were purchased in various supermarkets and bio-shops across metropolitan Lima on January 26, 2021. The pesticide residues in the samples were determined in a laboratory. The study found that Peruvian quinoa not only contained residues of internationally banned pesticides, but also had levels that exceed the maximum residue limits (MRLs) established by the European Union. For consumer safety, it is important that the government make the proposed regulations regarding hazardous pesticides clear to the public.

Honey bee queen health is unaffected by contact exposure to pesticides commonly found in beeswax

Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. Prior research has investigated the effects of indirect pesticide exposure on queens via workers, as well as direct effects on queens during development. However, as adults, queens are in constant contact with wax as they walk on comb and lay eggs; therefore, direct pesticide contact with adult queens is a relevant but seldom investigated exposure route. Here, we conducted laboratory and field experiments to investigate the impacts of topical pesticide exposure on adult queens. We tested six pesticides commonly found in wax: coumaphos, tau-fluvalinate, atrazine, 2,4-DMPF, chlorpyriphos, chlorothalonil, and a cocktail of all six, each administered at 1, 4, 8, 16, and 32 times the concentrations typically found in wax. We found no effect of any treatment on queen mass, sperm viability, or fat body protein expression. In a field trial testing queen topical exposure of a pesticide cocktail, we found no impact on egg-laying pattern, queen mass, emergence mass of daughter workers, and no proteins in the spermathecal fluid were differentially expressed. These experiments consistently show that pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics at the doses tested. We suggest that previously reported associations between high levels of pesticide residues in wax and queen failure are most likely driven by indirect effects of worker exposure (either through wax or other hive products) on queen care or queen perception.

Recent developments of pesticide adsorbents based on cyclodextrins

农药的研发与使用极大地提高了农作物的产量,为解决人类温饱、改善人类生活品质做出了贡献。但是,农药广泛残留于农副产品以及土壤和水体中,造成的污染日趋严重。残留的农药通常具有微量致毒、难生物降解、生物累积等特性,对生物健康与生态系统造成了巨大威胁。高效检测微量农药、减小污染危害是亟待解决的问题。吸附法具有成本低、操作简单、稳定性强、可重复性强的特点,在农药分离预富集领域得到了广泛关注。作为一种常用的农药吸附剂材料,环糊精是一类具有空腔的超分子化合物,能够作为主体通过主客体作用形成包合物;另外,可以通过醚化、酯化、氧化等化学反应对环糊精进行后修饰以提高其吸附性能。疏水作用、静电作用、范德华力、氢键作用、立体效应协同促进对农药的吸附。环糊精在农药吸附领域已经取得了一定进展,但是目前还没有基于环糊精的农药吸附剂的综述。该文针对杀菌剂、杀虫剂、除草剂、植物生长调节剂这4类农药,系统性地评述了基于环糊精的农药吸附剂的制备、吸附机理及应用,目前存在个别吸附剂吸附容量不高、降解机理不明确、降解产物对环境不友好、容易造成二次污染的问题,研发高吸附容量、易回收、易分离、易再生的基于环糊精的农药吸附剂是未来的主要研究方向。

False codling moth, Thaumatotibia leucotreta (Meyrick) a new threat to horticulture industry: Stakeholders’ perspectives on the status, impact and management in Kenya

False codling moth (FCM) has emerged as a major constraint to the production of horticultural crops in Kenya and is currently the leading cause of interceptions of Capsicum and cut flowers exported to European Union. Use of pesticides to control this pest is not only unsustainable, uneconomical but also contributes to interceptions of export produce due to higher levels of pesticide residues in the produce. Further, due to cryptic nature of feeding by the pest, pesticides often do not result to efficient control. Growing crops under protected areas though effective is not affordable to smallholder resource poor farmers necessitating search for a holistic integrated approach to manage this pest. In order to gather baseline information about the pest and current practices being used to manage the pest, a national deliberative stakeholders’ workshop was held in August 2018 at Kenya Agricultural and Livestock Research Organization, Katumani, Machakos bringing together farmer organizations, research scientists, agricultural extension service providers, regulators, policy makers and farmers and followup national meetings and trainings to advance the workshop deliberations. The paper presents perspectives of different stakeholders on the status and impact of FCM in horticultural crops in Kenya.

Neurochemical and Behavioral Dysfunctions in Pesticide Exposed Farm Workers: A Clinical Outcome.

The problem of pesticides is not new and its exposure to human due to indiscriminate use is largely associated with the health related problems including neurotoxicological alterations. High levels of pesticide residues and their metabolites in the dietary constituents, food materials, maternal blood, cord blood, placenta breast milk have been reported and linked to alterations in birth weight, crown heel length, head circumference, mid-arm circumference and ponderal index of the neonates. Epidemiological studies have suggested that exposure of pesticide to human could be a significant risk factor for neurological disorders, including Parkinson's disease, Alzheimer's disease and multiple sclerosis. Cholinergic and non-cholinergic dysfunctions in pesticide exposed population, especially in children have also been frequently reported in recent years. Developmental neurotoxicity is another concern in the area where pregnant are more prone towards its exposure and which results in the abnormalities in the fetus. In view of the increasing risk of human health through pesticide exposure, the present review has been focused on the studies pertaining to pesticide induced neurochemical alterations and associated behavioral abnormalities in farm workers which could establish a possible link between the its exposure and associated health hazards.

Microbial flora analysis for the degradation of beta-cypermethrin.

In the Xinjiang region of Eurasia, sustained long-term and continuous cropping of cotton over a wide expanse of land is practiced, which requires application of high levels of pyrethroid and other classes of pesticides-resulting in high levels of pesticide residues in the soil. In this study, soil samples were collected from areas of long-term continuous cotton crops with the aim of obtaining microbial resources applicable for remediation of pyrethroid pesticide contamination suitable for the soil type and climate of that area. Soil samples were first used to culture microbial flora capable of degrading beta-cypermethrin using an enrichment culture method. Structural changes and ultimate microbial floral composition during enrichment were analyzed by high-throughput sequencing. Four strains capable of degrading beta-cypermethrin were isolated and preliminarily classified. Finally, comparative rates and speeds of degradation of beta-cypermethrin between relevant microbial flora and single strains were determined. After continuous subculture for 3weeks, soil sample microbial flora formed a new type of microbial flora by rapid succession, which showed stable growth by utilizing beta-cypermethrin as the sole carbon source (GXzq). This microbial flora mainly consisted of Pseudomonas, Hyphomicrobium, Dokdonella, and Methyloversatilis. Analysis of the microbial flora also permitted separation of four additional strains; i.e., GXZQ4, GXZQ6, GXZQ7, and GXZQ13 that, respectively, belonged to Streptomyces, Enterobacter, Streptomyces, and Pseudomonas. Under culture conditions of 37°C and 180rpm, the degradation rate of beta-cypermethrin by GXzq was as high as 89.84% within 96h, which exceeded that achieved by the single strains GXZQ4, GXZQ6, GXZQ7, and GXZQ13 and their derived microbial flora GXh.

Effect of Processing on Pesticide Residues in Some Edible Fresh Water Fishes

The present study was undertaken to ascertain the effect of processing on pesticide residues in edible fresh water fishes. The fish samples were collected from two different fish markets located in Ludhiana city. Pesticide residues were detected in five different fish species by employing Gas Liquid Chromatography. Major pesticides detected include β-HCH, γ-HCH and chlorpyriphos with levels 0.30 mg kg−1, 0.1–0.35 mg kg−1 and 0.14–0.58 mg kg−1, respectively. Catla catla, Labeo rohita and Cirrhinus mrigala were found to have higher levels of pesticide residues. These fish samples were then processed by four different processing methods viz. deep frying, steaming by pressure cooker, conventional oven baking and microwave oven baking to check the reduction in residue levels. Deep frying caused maximum reduction i.e. 40–45% as compared to other processing methods. Steaming reduced pesticide residues by 14–16%, microwave oven baking resulted in 17–20% and conventional oven baking resulted in 20–21% reduction.

A scientific note on seasonal levels of pesticide residues in honey bee worker tissues

Honey bees (Apis mellifera L.) provide essential pollination services for agricultural production worldwide. Recent declines in honey bee populations have been attributed to a multitude of potential stressors, such as pest pressure, nutritional stress, and exposure to pesticides (vanEngelsdorp et al. 2009b). One possible explanation for bee decline is the accumulation of pesticide residues in honey bee brood comb, resulting in chronic exposure to a suite of agrochemicals which may detrimentally influence honey bee health. Wu et al. (2011) demonstrated that bees reared in brood comb containing high levels of pesticide residues exhibit increased brood mortality and shorter adult longevity.

Fruit and vegetable intake and their pesticide residues in relation to semen quality among men from a fertility clinic.

Is consumption of fruits and vegetables with high levels of pesticide residues associated with lower semen quality? Consumption of fruits and vegetables with high levels of pesticide residues was associated with a lower total sperm count and a lower percentage of morphologically normal sperm among men presenting to a fertility clinic. Occupational and environmental exposure to pesticides is associated with lower semen quality. Whether the same is true for exposure through diet is unknown. Men enrolled in the Environment and Reproductive Health (EARTH) Study, an ongoing prospective cohort at an academic medical fertility center. Male partners (n = 155) in subfertile couples provided 338 semen samples during 2007-2012. Semen samples were collected over an 18-month period following diet assessment. Sperm concentration and motility were evaluated by computer-aided semen analysis (CASA). Fruits and vegetables were categorized as containing high or low-to-moderate pesticide residues based on data from the annual United States Department of Agriculture Pesticide Data Program. Linear mixed models were used to analyze the association of fruit and vegetable intake with sperm parameters accounting for within-person correlations across repeat samples while adjusting for potential confounders. Total fruit and vegetable intake was unrelated to semen quality parameters. High pesticide residue fruit and vegetable intake, however, was associated with poorer semen quality. On average, men in highest quartile of high pesticide residue fruit and vegetable intake (≥1.5 servings/day) had 49% (95% confidence interval (CI): 31%, 63%) lower total sperm count and 32% (95% CI: 7%, 58%) lower percentage of morphologically normal sperm than men in the lowest quartile of intake (<0.5 servings/day) (P, trend = 0.003 and 0.02, respectively). Low-to-moderate pesticide residue fruit and vegetable intake was associated with a higher percentage of morphologically normal sperm (P, trend = 0.04). Surveillance data, rather than individual pesticide assessment, was used to assess the pesticide residue status of fruits and vegetables. CASA is a useful method for clinical evaluation but may be considered less favorable for accurate semen analysis in the research setting. Owing to the observational nature of the study, confirmation is required by interventional studies as well. To our knowledge, this is the first report on the consumption of fruits and vegetables with high levels of pesticide residue in relation to semen quality. Further confirmation of these findings is warranted. Supported by National Institutes of Health grants ES009718, ES022955, ES000002, P30 DK046200 and Ruth L. Kirschstein National Research Service Award T32 DK007703-16. None of the authors has any conflicts of interest to declare.

Pesticide residues in food of plant origin from Southeast Asia – A Nordic project

Fruits and vegetables from Souteast Asia were analysed for the presence of pesticide residues. A total of 721 samples of 63 different commodities were collected in 2011. The products were imported to Denmark, Finland, Norway and Sweden from ten countries; about 80% were imported from Thailand. The reason for the increased control for certain food products from Southeast Asia was that the official control had revealed many products with too high levels of pesticide residues. In 60% of the samples we did not find any residues, while 28% had residues below or at the MRLs. Results above the MRLs were found in 12% of the samples. In comparison 6% of surveillance samples from third countries and 1.5% of surveillance samples from the EU and EFTA countries exceeded the MRL in the EU monitoring program in 2011. The estimated acute intake was higher than 100% of the ARfD in several samples and some of the products were assessed to represent possible acute health risk for consumers.

Dynamic Analysis of Pesticide Degradation in Off-Season Vegetables Stored in Frozen Conditions

Nowadays, public concern over food safety, especially the potential health risk to humans cause by the high levels of pesticide residues, has increased. In general, people usually refrigerate fresh vegetable in order to keep their freshness intact for longer duration of time. Very few research studies have investigated the correlation between refrigerated vegetables and degradation of pesticide residue. Gas chromatography was used to conduct dynamic analysis of pesticide degradation in off-season vegetables, which are kept in cold storage conditions. Cowpea and balsam pear samples were extracted with acetonitrile. The resultant extracts were purified in SPE column filled with cleanert pesticarb. Thereafter, the eluant extracts were determined through gas chromatography coupled with μECD. Matrix-matched calibrations were analyzed through GC-ECD, where in the limits of quantification varied between 0.0005 and 0.0026mg/kg. The linear coefficients of correlation varied between 0.9916 and 0.9997. Recoveries on cowpea and balsam pear were in the range 74.7%~98.8%. Based on the residue dynamics study, the half-lives of the five pesticides in cowpea were as follows: chlorpyrifos: 247d, chlorfenapyr: 407d, bifenthrin: 462d, cyhalothrin: 346d, and cis-cypermethrin: 315d. In balsam pear samples, the half-lives of the five pesticides were as follows:chlorpyrifos: 150d, chlorfenapyr: 187d, bifenthrin: 433d, cyhalothrin: 266d, and cis-cypermethrin: 210d. The residue of five pesticides in cowpea and balsam pear underwent slow degradation in cold storage conditions. In this study, the findings serve as important reference data, which can be used by the concerned state authorities in formulating the limit of pesticide residue in food.

Honey bees (Apis mellifera) reared in brood combs containing high levels of pesticide residues exhibit increased susceptibility to Nosema (Microsporidia) infection

Nosema ceranae and pesticide exposure can contribute to honey bee health decline. Bees reared from brood comb containing high or low levels of pesticide residues were placed in two common colony environments. One colony was inoculated weekly with N. ceranae spores in sugar syrup and the other colony received sugar syrup only. Worker honey bees were sampled weekly from the treatment and control colonies and analyzed for Nosema spore levels. Regardless of the colony environment (spores+syrup added or syrup only added), a higher proportion of bees reared from the high pesticide residue brood comb became infected with N. ceranae, and at a younger age, compared to those reared in low residue brood combs. These data suggest that developmental exposure to pesticides in brood comb increases the susceptibility of bees to N. ceranae infection.

Sub-Lethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis mellifera) Development and Longevity

BackgroundNumerous surveys reveal high levels of pesticide residue contamination in honey bee comb. We conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan.Methodology/Principal FindingsWorker bees were reared in brood comb containing high levels of known pesticide residues (treatment) or in relatively uncontaminated brood comb (control). Delayed development was observed in bees reared in treatment combs containing high levels of pesticides particularly in the early stages (day 4 and 8) of worker bee development. Adult longevity was reduced by 4 days in bees exposed to pesticide residues in contaminated brood comb during development. Pesticide residue migration from comb containing high pesticide residues caused contamination of control comb after multiple brood cycles and provided insight on how quickly residues move through wax. Higher brood mortality and delayed adult emergence occurred after multiple brood cycles in contaminated control combs. In contrast, survivability increased in bees reared in treatment comb after multiple brood cycles when pesticide residues had been reduced in treatment combs due to residue migration into uncontaminated control combs, supporting comb replacement efforts. Chemical analysis after the experiment confirmed the migration of pesticide residues from treatment combs into previously uncontaminated control comb.Conclusions/SignificanceThis study is the first to demonstrate sub-lethal effects on worker honey bees from pesticide residue exposure from contaminated brood comb. Sub-lethal effects, including delayed larval development and adult emergence or shortened adult longevity, can have indirect effects on the colony such as premature shifts in hive roles and foraging activity. In addition, longer development time for bees may provide a reproductive advantage for parasitic Varroa destructor mites. The impact of delayed development in bees on Varroa mite fecundity should be examined further.

Pesticide residues in apples grown under a conventional and integrated pest management system

This paper describes method validation for determination of more than 40 pesticides in apples using a GC technique. Target compounds belonged to the organochlorine, organophosphorus, carbamates, pyrethroids, triazoles, dicarboximides and strobilurins groups, among others. Sample preparation consisted of acetone extraction and subsequent cleanup/concentration by SPE with a polymer-based sorbent. Single quadrupole GC–MS operating in SIM mode and electron impact ionization was used for identification and quantification of the pesticides. Average recoveries for analytes ranged between 70 and 110% at three fortification levels – 0.01, 0.1 and 0.2 mg kg−1. Relative standard deviations were lower than 20% for all tested compounds. Calculated limits of detection and limits of quantification were below 0.01 mg kg−1, which were sufficiently low compared to the maximum residue levels (MRLs) established by European legislation. The proposed method was applied for determination of pesticide residue in four selected apple varieties after harvesting. Whole and processed fruits (peel and peeled fruits) were analyzed from different treatment systems: two conventional, one based on integrated pest management (IPM) and two variants based on organic production (controls). Higher levels of pesticide residues were found in apple fruits under conventional conditions. Fenitrothion and chlorpyrifos residues were detected frequently in apple peel at concentrations up to 0.45 and 0.77 mg kg−1, respectively. The levels found in the whole fruits of the same samples were much lower than in peel and below the respective MRLs (0.5 mg kg−1 for both pesticides). Measurable residues of triadimenol only, up to 0.05 mg kg−1, concentrated in the peel, were found in the apples from IPM.

PESTICIDE PRACTICES IN SOME EGYPTIAN EXPORTATION FARMS

Information related to pesticide practices in green beans and strawberry fields in some selected exportation farms in Egypt was obtained through questionnaire forms. Such forms were randomly distributed among different target exporters at Giza, Ismaellia, Sharkia, Behirah and Alfayoum governorates. Questionnaire outputs indicated that the percent of the rejected export by importers due to high levels of pesticide residues reached 11.11 and 7.69% in green beans and strawberry respectively. The recommended rates of the used pesticides established by the Ministry of Agriculture and/or EU guidelines were followed by 86.67 and 69.23% of these vegetables growers, respectively. Questionnaire outputs indicated that the percent of exporters who were repeating the application of all or each pesticide during the same season of green beans and strawberry reached 48.89 and 42.31%, respectively. Furthermore, 15.56 and 7.69% of growers followed the recommended Pre Harvest interval (PHI) for each pesticide used in green beans and strawberry. On the other hand, no storage period was followed by 40 and 76.92% of the exporters for green beans and strawberry, respectively. Concerning the transportation conditions data showed that 55.56 and 88.46% of the exporters used cooling trucks with green beans and strawberry, respectively.

Pesticides in Urban Multiunit Dwellings: Hazard Identification Using Classification and Regression Tree (CART) Analysis

Many units in public housing or other low-income urban dwellings may have elevated pesticide residues, given recurring infestation, but it would be logistically and economically infeasible to sample a large number of units to identify highly exposed households to design interventions. Within this study, our aim was to devise a low-cost approach to identify homes in public housing with high levels of pesticide residues, using information that would allow the housing authority and residents to determine optimal strategies to reduce household exposures. As part of the Healthy Public Housing Initiative, we collected environmental samples from 42 public housing apartments in Boston, MA, in 2002 and 2003 and gathered housing characteristics; for example, household demographics and self-reported pesticide use information, considering information available with and without a home visit. Focusing on five organophosphate and pyrethroid pesticides, we used classification and regression tree analysis (CART) to disaggregate the pesticide concentration data into homogenous subsamples according to housing characteristics, which allowed us to identify households and associated networks impacted by the mismanagement of pesticides. The CART analysis demonstrated reasonable sensitivity and specificity given more extensive household information but generally poor performance using only information available without a home visit. Apartments with high concentrations of cyfluthrin, a pyrethroid of interest given that it is a restricted use pesticide, were more likely to be associated with Hispanic residents who resided in their current apartment for more than 5 yr, consistent with documented pesticide usage patterns. We conclude that using CART as an exploratory technique to better understand the home characteristics associated with elevated pesticide levels may be a viable approach for risk management in large multiunit housing developments.

Consumer perceptions of organic foods in Bangkok, Thailand

In response to food scares related to high levels of pesticide residues sometimes found on vegetables and fruits, consumers in Thailand increasingly demand ‘safe’ foods. This has resulted in a number of initiatives and labels indicating ‘pesticide safe’ vegetables. However, the pesticide-residue problem has proved enduring. This opens a market opportunity for organic foods, which are produced entirely without using synthetic chemicals. As little is known on consumer perception of organic foods in Thailand, a survey was conducted in Bangkok. More than a third of the 848 respondents reported having purchased organic vegetables or fruits in the past. The main reasons for purchasing organic products are that consumers expect them to be healthier, that organic products are environmentally friendly. The respondents who have bought organic vegetables tend to be older, have a higher education level and a higher family income than those who have not bought them. The main barrier to increasing the market share of organic vegetables is that consumers do not clearly differentiate between the various ‘pesticide safe’ labels and the organic labels. Informing consumers about unique characteristics of organic production methods, the strict inspection and required third party certification might be a promising strategy to develop the market for organic vegetables in Thailand’s urban centers.

Organochlorine pesticide residues in catfish, Tachysurus thalassinus (Ruppell, 1835), from the South Patches of the Bay of Bengal

Organochlorine pesticides (p,p′-DDT, p,p′-DDD, p,p′-DDE, aldrin, lindane, and heptachlor) were measured in muscle tissue of catfish (Tachysurus thalassinus) during the dry and wet season. Catfish were collected from the South Patches of the Bay of Bengal during October–December 1997 and May–July 1998. Tissue residues were analyzed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). The pesticide residues levels were found in order of Σ DDT>Heptachlor>Lindane>Aldrin. Higher levels of pesticide residues were found in all samples during dry season, as compared with the wet season, primarily due to elevated lipid content in fishes. A positive correlation and linear relationship was observed between the pesticide residues (ΣDDT and ΣOCs) and lipid content of fishes. However, the concentrations of pesticide residues in the muscle were found to be lower than the FAO/WHO [(1993) Food standards programme. Codex Alimentarius Commission, vol. 9 (4) pp. 149–158] recommended permissible limit for human consumption.