Analysis of current chemical risks associated with vegetables in the commune of Yopougon following the application of various treatment methods

 Corresponding author: Koffi Morofie Justin KOUAME Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Analysis of current chemical risks associated with vegetables in the commune of Yopougon following the application of various treatment methods Koffi Morofie Justin KOUAME 1, *, Koffi David AKAKI 1, Adobi Christian KADJO 2, Ettien Léon HAMIAN 1 and Sylvestre DAGO 3 1 Nutrition and Food Technology Laboratory, Institute National Polytechnique Félix Houphouët-Boigny (INP-HB), BP 1093 Yamoussoukro, Côte d’Ivoire. 2 Laboratoire de Biotechnologie et Microbiologie des Aliments (LMBA), Unité de Formation et de Recherche en Sciences et Technologies Alimentaires (UFR STA), Université Nangui Abrogoua (UNA), 02 Bp 801 Abidjan 02, Côte d’Ivoire. 3 Laboratory of phytopathology and plant biology, Institut National Polytechnique Félix Houphouët-Boigny (INP-HB), BP 1093 Yamoussoukro, Côte d’Ivoire. World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 Publication history: Received on 16 April 2025; revised on 25 May 2025; accepted on 28 May 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.26.2.2058 Abstract This study evaluates the chemical risks linked to pesticide residues in vegetables from Yopougon (Côte d'Ivoire) and the effectiveness of washing methods to reduce these contaminants. The context reveals alarming contamination due to the intensive use of pesticides in urban agriculture, threatening consumer health through acute and chronic effects. The general objective is to compare three washing methods: sodium hypochlorite (1%, 5 min), sodium bicarbonate (1%, 10 min in ice-cold water), and their combination (5 min), on samples of lettuce, tomato, cucumber, and pepper analyzed by HPLC according to the NF EN 12393-3 standard. The results show that the combined method is the most effective, reducing residues by over 90%, compared to 49-87% for individual methods. However, pesticides such as ethylparathion and diuron persist, presenting high health risks (QD > 1). The conclusion emphasizes the need to combine preventive measures (pesticide reduction) and curative measures (optimized washing) to improve food safety. The outlook includes promoting sustainable agricultural practices and raising awareness among local stakeholders to minimize exposure to toxic residues. Keywords: Pesticide Residues; Contamination; Washing; Health Risk; Yopougon 1. Introduction Urban vegetable farming, which accounts for approximately 33% of global agricultural production and engages nearly 800 million people, plays a crucial socio-economic role, particularly in Côte d'Ivoire. In Abidjan, green spaces and lowlands are intensively cultivated for vegetable production, generating essential income for vulnerable populations in peri-urban areas (El-Sheikh et al., 2022; Gueye et al., 2020). However, the sanitary quality of these products is often compromised by the excessive use of pesticides, leading to chemical pollution and the presence of residues hazardous to human health (Ssemugabo et al., 2023). These residues can cause acute effects (dizziness, headaches) and chronic effects (cancers, endocrine disruptions) (Wanwimolruk et al., 2015; Ibrahim et al., 2018). Despite these risks, there is a lack of awareness among producers and consumers regarding the dangers of chemical contamination, exacerbating the situation (Ssemugabo et al., 2023). Studies reveal significant contamination of fruits and vegetables, with up to 63.3% of samples exceeding Maximum Residue Limits (MRLs) (El-Sheikh et al., 2022; Mwanja et al., 2017). The chemical families of organochlorines and organophosphates, particularly stable and toxic, represent World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3793 a major health risk, necessitating rigorous controls to ensure admissible residue levels and prevent misuse (El-Sheikh et al., 2022). It is therefore imperative to strengthen awareness and education among producers and consumers to minimize exposure to pesticide residues (Ssemugabo et al., 2023; Ibrahim et al., 2018). The adoption of sustainable agricultural practices and adherence to good phytosanitary practices are essential to mitigate this public health issue in the vegetable farming sector (Mazlan et al., 2017). Facing these challenges, this study aims to evaluate the effectiveness of different washing methods (sodium bicarbonate, sodium hypochlorite, or a combination of both) in reducing pesticide residues in cucumbers, tomatoes, peppers, and lettuce produced in Yopougon. The objective is to improve the sanitary quality of vegetable products and raise consumer awareness of proper washing practices to limit health risks 2. Material and methods 2.1. Study Site The study was conducted in the autonomous district of Abidjan, specifically in the commune of Yopougon, located between the Banco Forest and the Ebrié Lagoon, west of the northern geographical zone of Abidjan. The geographical coordinates of the commune are 5°20'56" North and 4°00'42" West. It has a population of 1,571,065 inhabitants, with a density of 9,568 inhabitants/km², and covers an area of 16,420 hectares (164.2 km²). Its altitude ranges from 40 to 132 meters above sea level. Directed by KOUAME Koffi Morofie Justin on 12/12/2023 Source: OCHA West and Africa (ROWCA) Figure 1 Location of vegetable production areas in the yopougon municipality World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3794 2.2. Study Material The study focused on samples of lettuce (Lactuca sativa), tomato (Lycopersicon esculentum), cucumber (Cucumis sativus), and pepper (Capsicum frutescens), collected from three major vegetable production zones in Yopougon: Adiopodoumé (Km 17), Niangon Adjamé (Lièvre-Rouge), and Niangon Attié (Attiesso). The sampling period extended from August 2024 to February 2025. A: Peppers (Capsicum annuum); B: Lettuce (Lactuca sativa); C: Cucumbers (Cucumis sativus); D: Tomatoes (Solanum lycopersicum).All products are collected aseptically at the production sites in BIOHAZARD weighing bags, using sterile, single-use latex gloves Figure 2 Photographs of vegetables 2.3. Sample Analysis Equipment 2.3.1. Laboratory Equipment The equipment for pesticide residue detection included: glassware, an electric mixer for grinding samples, an electronic balance for weighing, a shaker for homogenizing extracts, a centrifuge for phase separation, a vacuum pump for filtration, solvent evaporation, and sample concentration/purification, ensuring precise and reliable residue detection. Additional tools included Wattman filter paper, pro-pipettes (100 µL to 1000 µL), vials for extract collection, a microsyringe for HPLC injection, and an HPLC device for pesticide residue separation and identification. 2.3.2. Reagents and Solvents The solvents consisted of distilled water, methanol, dichloromethane (DCM), borate buffer, chloroformate chloride (9fluorenylmethyl), hexane, sodium hydroxide, and hydrochloric acid. World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3795 2.4. Site and Vegetable Selection The studied production zones included Adiopodoumé (Km 17), Niangon Attié (Attiesso), and Niangon Adjamé (Lièvre Rouge), representing the primary sources of fresh vegetable supply for Yopougon and its surroundings. Located in urbanized plains, these areas are bordered by factories and supplied with wastewater and runoff, with solid waste nearby. These sites were chosen for their accessibility and the availability of voluntary producers. Additionally, the Gouro Market in Adjamé, a major trading hub, concentrates wholesale sellers of vegetables, fruits, and other foodstuffs, serving as a strategic distribution point for farmers from Abidjan and inland regions. 2.5. Sample Collection For sampling, three production zones (Adiopodoumé, Niangon Adjamé, and Niangon Attié) were selected, with three production sites per zone. Within each site, plots managed by producers were chosen for sampling. A total of 1 kg of each vegetable (tomatoes, cucumbers, peppers, lettuce), freshly harvested from each plot, was randomly collected, placed in sterile BIOHAZARD plastic bags (Fisher Scientific), and handled with sterile Synguard latex gloves. All samples were collected between August 2024 and February 2025. Due to varying treatments applied to each vegetable type, three samples per product were taken per site, totaling 36 samples across all zones. The labeled samples were stored in coolers with dry ice for preservation and transported to microbiology and biotechnology laboratories for treatment. Subsequently, they were sent to the National Agricultural Development Support Laboratory (LANADA) for pesticide residue analysis via high-performance liquid chromatography (HPLC). 2.6. Pre-Analysis Treatment For each treatment, a 100 g portion of each fresh vegetable was accurately weighed using an analytical balance. The treatment methods were implemented as described below, with three replicates per method. 2.6.1. Untreated Control For each analyzed vegetable, 500 g of fresh samples were weighed without prior treatment. Portions of 100 g were then placed in labeled Stomacher bags for traceability. 2.6.2. Running Water Wash A total of 500 g of each fresh vegetable sample was washed under running water for 5 minutes. After drying with absorbent paper, the samples were allocated based on treatment plans and collection sites. 2.6.3. Soaking Treatments for Chemical Contamination Reduction Vegetable samples underwent various soaking treatments to reduce chemical contamination. For the first treatment, a 1% sodium hypochlorite solution was prepared by mixing 250 mL of 8% bleach with 1750 mL of tap water in 5000 mL beakers, totaling 2000 mL. Each 100 g sample was immersed for 5 minutes. For the second treatment, a 1% sodium bicarbonate solution was prepared by dissolving 20 g of sodium bicarbonate in 2000 mL of ice-cold water, with samples soaked for 10 minutes. A third combined treatment was performed by mixing 250 mL of 8% bleach with 1750 mL of ice-cold water, adding 20 g of sodium bicarbonate, for a total volume of 2000 mL. Samples were immersed in this combined solution for 5 minutes. After each treatment, the vegetables were thoroughly rinsed, drained, and prepared for analysis. Treated samples were stored in coolers with dry ice for transport to LANADA, where extraction analyses were conducted. These treatments leverage the complementary properties of sodium hypochlorite and sodium bicarbonate, two safe and widely available agents. Sodium bicarbonate, a safe alkaline cleaner, acts against microorganisms and pesticide residues, while sodium hypochlorite, an affordable disinfectant, eliminates a broad spectrum of pathogens due to its strong oxidizing power. 2.7. Pesticide Analysis 2.7.1. Sample Preparation Fresh vegetable samples (lettuce, tomatoes, cucumbers, peppers) were prepared following a standardized protocol for pesticide quantification. After washing, 100 g of each vegetable were precisely weighed, ground into a homogeneous paste, and stored in sterile containers at low temperatures before chromatographic analysis. World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3796 2.7.2. Pesticide Quantification Pesticide residue analysis in vegetables was conducted according to the NF EN 12393-3 (December 2013) standard using HPLC. A 50 g homogenized sample was mixed with 30 mL of distilled water, blended, and centrifuged. The supernatant was filtered through Wattman No. 114 paper and further purified using a C18 column activated with methanol and distilled water. Pesticide residues were eluted with 2 mL of methanol, collected in sterile vials, and injected into the HPLC for detection and quantification. Identification relied on chromatographic peak analysis, while quantification was based on calibration curves from certified standards. 2.7.3. Quality Assurance Quality criteria were strictly applied to evaluate method performance. The Limit of Quantification (LOQ) was set at 0.009 mg·kg⁻¹, varying by pesticide type, while the Limit of Detection (LOD) was 0.017 µg/kg. Residue quantification (mg/kg) was performed via HPLC peak area analysis and calibration curves, ensuring precise, reproducible results compliant with European regulatory standards. 2.7.4. Concentration Quantification Pesticide detection and quantification by HPLC were based on calibration curves expressed as: A = k·C + b, where A: peak area; k: slope; b: y-intercept (He et al., 2019). Critical parameters (temperature, flow rate, mobile phase composition) were rigorously controlled for accuracy (Khotimah et al., 2020). Residue confirmation was achieved via HPLC-MS/MS, analyzing mass/charge ratios (m/z) for precise identification and quantification, complying with ISO/IEC 17025 standards for reliable regulatory analysis. 2.8. Health Risk Assessment Health risk assessment for pesticide residues compared measured concentrations in vegetables to MRLs established by regulatory bodies (EU/FAO/Codex). The Hazard Quotient (HQ) was calculated as follows: HQ =C MRL • C: Pesticide residue concentration in the vegetable (mg/kg or ppm). • MRL: Maximum Residue Limit (mg/kg). If HQ ≥ 1: The risk is deemed concerning (residue exceeds toxicological reference values). 2.8.1. Standards, Acceptable Daily Intake (ADI), and Maximum Residue Limits (MRLs) Table 1 Quality Standards and Pesticide Residue Limits Pesticide ADI (mg/kg bw/day) MRL - Fresh Vegetables (mg/kg) References (EU/FAO/Codex) Métamitron 0.01 0.05 EU Regulation 2023/814 Crimidine 0.0005 0.01 Codex STAN 193-1995 Monuron 0.02 0.1 EU Regulation 2020/856 Monolinuron 0.025 0.2 EU Regulation 2019/1797 Chlortoluron 0.015 0.5 EU Regulation 2021/1902 Terbuthylazine 0.004 0.05 EU Regulation 2022/1434 Métazachlore 0.01 0.3 EU Regulation 2020/1085 Diuron 0.001 0.1 EU Regulation 2023/771 Linuron 0.005 0.2 EU Regulation 2018/832 Prometryne 0.01 0.05 EU Regulation 2021/1099 Isoproturon 0.006 0.1 EU Regulation 2019/1862 Chlorprophame 0.03 0.5 EU Regulation 2022/1015 World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3797 Métolachlore 0.005 0.05 EU Regulation 2020/1248 Vinclozoline 0.01 0.05 EU Regulation 2018/1480 Parathion-éthyl 0.004 0.02 Codex STAN 197-1995 2.9. Statistical Analysis Descriptive statistics (mean, standard deviation) and histograms were generated using Excel (Microsoft Office 2019). For statistical comparisons, XLSTAT (2006 version) was employed, including ANOVA followed by Duncan’s post-hoc test (significance threshold: p < 0.05). 3. Results and Discussion The pesticide residue results presented in this study derive from vegetable samples subjected to different treatments, as described in the Materials and Methods section. These treatments were implemented to evaluate the efficacy of decontamination practices in reducing pesticide residues in fresh vegetables. 3.1. Mean Total Concentrations of Active Substances in Different Vegetables This study highlights the varying efficacy of three vegetable decontamination protocols against pesticide residues. Initial residue concentrations in controls followed this hierarchy: pepper (1.078 mg/kg) > lettuce (0.778 mg/kg) > cucumber (0.656 mg/kg) > tomato (0.492 mg/kg). This diversity reflects species-specific accumulation mechanisms, corroborated by research on pesticide bioaccumulation variations due to anatomical and physiological plant traits (AlSaikhan et al., 2021; Bars et al., 2020). Plants with thinner cuticles (e.g., tomato) showed higher contamination levels, facilitating chemical absorption, while thick-cuticle peppers acted as more effective barriers, requiring tailored decontamination strategies. T: Treatment; J: Bleach; B: Sodium bicarbonate; J+B: Bleach + sodium bicarbonate Figure 3 Pesticide residue concentrations in Yopougon vegetables after decontamination For the 1% sodium hypochlorite (NaClO) treatment (5 min), average residue reduction efficacy ranged between 49.07% and 65.40%, aligning with prior studies (Park et al., 2022). The oxidative mechanism of NaClO is well-documented, but operational parameters must be strictly followed to avoid toxic byproduct formation (AlSaikhan et al., 2021). The 1% sodium bicarbonate (NaHCO₃) treatment (10 min) showed improved efficacy (65.45–87.35%), consistent with alkaline hydrolysis’s potential for pesticide degradation (Ramadan et al., 2020). However, prolonged exposure or higher concentrations may compromise vegetable texture (Bars et al., 2020), underscoring the need for adherence to guidelines. World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3798 The combined protocol (NaClO 1% + NaHCO₃ 1%) achieved exceptional performance, exceeding 90% reduction for most vegetables, validating the synergy between oxidative and alkaline treatments (Chouti et al., 2018). However, this approach risks tissue degradation and byproduct formation, necessitating stringent parameter control for commercialscale application (Dakuyo et al., 2020). Anatomically, decontamination efficacy varied with vegetable morphology. Tomatoes, with thinner cuticles, allowed better agent penetration, while thick-cuticle peppers required adapted treatments (El-Mageed et al., 2022). Despite its efficacy, the combined method faces three major constraints: operational control, regulatory compliance for hypochlorite, and economic implications of complex procedures. 3.2. Pesticide Residues in Treated Vegetables This study detected 17 pesticide molecules from six chemical families in four commonly consumed raw vegetables in Yopougon. Herbicides dominated (70.59%), followed by insecticides (23.53%) and fungicides (5.88%), reflecting intensive agricultural practices (Rimayi et al., 2018). Significant interspecies variations were observed, with elevated concentrations in peppers and lettuce, indicating crop-specific residue selectivity (Mazibuko et al., 2023). Triazines and urea derivatives were most concerning. Chlortoluron (0.388 mg/kg) is linked to endocrine disruption and liver depression (Abass et al., 2021). Metamitron (0.091 mg/kg) poses potential carcinogenic risks, while diuron (0.271 mg/kg) is associated with renal and thyroid disorders (Banjac et al., 2022). Organophosphates like ethyl-parathion (0.109 mg/kg) exhibit acute neurotoxicity via acetylcholinesterase inhibition (D’Amico et al., 2021). Carbamates and dicarboximide fungicides, with estrogenic properties, raise endocrine disruption concerns (Мilićević et al., 2024). Herbicide predominance underscores excessive chemical reliance, a documented issue in sub-Saharan Africa (Rimayi et al., 2018). This poses multifaceted health risks, from carcinogenicity to neurological impairments (Rives et al., 2020; Goh et al., 2022). As vegetables are typically consumed raw, the absence of thermal treatment exacerbates concerns. The findings urge revised agricultural practices in Yopougon, emphasizing reduced triazine/urea herbicide use and enhanced residue monitoring (Mazibuko et al., 2023). Policy reforms should promote sustainable practices, minimize pesticide impacts, and educate consumers, integrating this study into broader urban African food safety frameworks (Dhagat & Jujjavarapu, 2021). In conclusion, integrated crop management strategies—including conservation agriculture and alternative pest control—are needed to reduce synthetic pesticide dependence and mitigate human/environmental harm (Manzoor & Pervez, 2022; Mazibuko et al., 2023). World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3799 Table 2 Mean Concentrations of Active Substances in Yopougon Vegetables After decontamination Pesticide Lettuce Tomato Cucumber Pepper Famille Molécules control J B J+B control J B J+ B control J B J+B contr ol J B J+B TRIAZINE Métamitron 0.050 ± 0.002b 0,016 ± 0,001d 0,001 ± 0e ND ND ND ND ND 0.088 ± 0.002a 0,029 ± 0,003c ND ND ND ND ND ND Crimidine 0.041 ± 0.004a 0,015 ± 0,002c 0,002 ± 0d ND ND ND ND ND 0.027 ± 0.003b 0,002 ± 0d ND ND ND ND ND ND Métoxuron 0.080 ± 0.005a 0,034 ± 0,003c 0,032 ± 0,002c 0,003± 0,001d 0.030 ± 0.003c ND ND ND 0.070 ± 0.003a 0,046 ± 0,005b ND ND ND ND ND ND Monuron ND ND ND ND ND ND ND ND 0.299 ± 0.03a 0,025 ± 0,001b ND ND ND ND ND ND UREA DERIVATIVES Chlortoluro n 0.300 ± 0.03a 0,168 ± 0,01c ND ND ND ND ND ND ND ND ND ND 0.232 ± 0.002b 0,017 ± 0,002d ND ND Terbuthyla zine 0.081 ± 0.008a 0,023 ± 0,001b 0,008 ± 0c 0,006± 0c ND ND ND ND ND ND ND ND ND ND ND ND Métazaclor ND ND ND ND ND ND ND ND ND ND ND 0.337 ± 0.003a 0,133 ± 0,001b ND ND Diuron 0.072 ± 0.004g ND ND ND 0.257 ± 0.003b 0,15 ± 0,006d 0,122 ± 0,009e 0,0 15 ± 0.0 01h 0.217 ± 0.002c 0,112 ± 0,002f 0,09 ± 0fg 0,028 ± 0,001 0.271 ± 0.04a 0,156 ± 0,003d 0,127 ± 0,003e 0,051± 0,001gh Linuron ND ND ND ND 0.143 ± 0.005a 0,082 ± 0,002c 0,023 ± 0g ND 0.077 ± 0.004d 0,023 ± 0,001g 0,00 8 ± 0i ND 0,103± 0.012b 0,064 ± 0,001e 0,037 ± 0,001f 0,014±0 ,002h Prometryn ND ND ND ND 0.042 ± 0.005b 0,015 ± 0,001d ND ND 0.025 ± 0.001c 0,005 ± 0e ND ND 0.067 ± 0.003a 0,026 ±0,002 c 0,014 ± 0,002d 0,008±0 ,002de World Journal of Advanced Research and Reviews, 2025, 26(02), 3792–3804 3800 Isoproturo n ND ND ND ND ND ND ND ND ND ND ND ND 0.22 ± 0.002a 0,17 ± 0,001b ND ND CARBOM ATE Chlorproph am ND ND ND ND ND ND ND ND ND ND ND ND 0.052 ± 0.002a 0,019 ± 0,002b ND ND ORGANOP HOSPHOR E Vinclozolin ND ND ND ND ND ND ND ND 0.017 ± 0.003a 0,008± 0b ND ND ND ND ND ND Parathionéthyl 0.109± 0.002a 0,08 ± 0,004b 0,068 ± 0,001bc 0,013± 0,001e ND ND ND ND ND ND ND ND 0,045± 0,003d 0,013± 0,002e ND ND