Pesticide Residues and Health Risk Perceptions of Retail Vegetables in Warri and Environ, Delta State, Nigeria

charts. The appearance of distinct coloured bands confirmed the presence of specific organochlorine, organophosphorus, or carbamate compound structures before high-resolution automated injection protocols. Standards High-purity (> 98.5%) analytical pesticide reference standards for herbicides, insecticides, and fungicides were obtained from LUCO in Benin, Nigeria. Primary standard stock solutions were made at a concentration of 1000 mg/L in chromatographic grade acetone or n-hexane. Multi-level working calibration standards were diluted from the stock solutions to create clear five-point external calibration curves (0.01, 0.05, 0.10, 0.50, and 1.00 mg/L) with correlation coefficients (r2) greater than 0.998. Quantitative Analytical Methods Inline with Jan et al. (2025), quantitative tracking of pesticide residues was done using a Gas Chromatography system with an Electron Capture Detector (GC-ECD) and a Flame Photometric Detector (GC-FPD). A High-Performance Liquid Chromatography setup was used for polar fractions. We injected 1.0μL samples in splitless mode onto a capillary column measuring 30m × 0.25mm ID × 0.25μm film thickness. High-purity helium served as the carrier gas at a steady flow rate of 1.2mL/min. We quantified the samples by mapping their peak retention times and integration areas to standard linear regression equations. The Limit of Detection for the targeted agrochemicals ranged from 0.001 to 0.005mg/kg, while the Limit of Quantification ranged from 0.003 to 0.015mg/kg. This showed that the method can track residues well below regional enforcement thresholds. Quality Assurance As opined by Roy et al. (2025), quality assurance and strict contamination control procedures were implemented to ensure the integrity, accuracy, and reproducibility of the data. All laboratory glassware was cleaned with phosphate-free detergent, rinsed with high-purity solvents, and dried before use. Reagent blank checks were run with every batch of 10 samples to monitor background profiles and make necessary adjustments. Method validation was confirmed by checking spike recoveries using certified organic matrix reference materials. The average recovery rates for the target compounds consistently ranged from 87% to 104%, with a relative standard deviation below 5%. Consumer Awareness Survey A field tracking survey was carried out among consumers and retail buyers in the selected open- air retail market centres using structured questionnaires. The survey aimed to record buying patterns, pinpoint geographical farm supply sources, check pesticide application frequencies, and highlight important public knowledge gaps about food safety standards. Participation was completely voluntary and kept strictly confidential under signed informed consent agreements. Statistical Analyses Statistical evaluations were done on the quantitative laboratory data and survey parameters using IBM SPSS Statistics software, Version 26.0. Descriptive statistical measures, including mean, standard deviation, and concentration ranges in mg/kg units, summarized the baseline pesticide distributions across all vegetable groups. Inferential comparisons using one-way Analysis of Variance, or ANOVA, followed by Duncan’s Multiple Range Tests (P = 0.01), were used to assess variation thresholds of pesticide residue concentrations across different markets and vegetable species. To evaluate human dietary exposure indices, we calculated Hazard Quotients (HQ) and Cancer Risk (CR) margins and compared them to the permissible Maximum Residue Limits and safety baselines set by the WHO, FAO, and NAFDAC. 3.0 Results and Discussion The screening of pesticide residues, along with the survey results on consumer awareness from key open-air retail locations in Warri and the surrounding area, is shown in Tables 1 to 3 and Figures 1 to 3. The heavy and unchecked use of synthetic agrochemicals greatly affects the food safety of local agricultural products. This poses serious health and economic risks for urban populations. It is good to note that targeted organochlorine pesticides, which global regulatory bodies have banned (like DDT and Dieldrin), were found below the analytical Limit of Detection (LOD = 0.001 mg/kg) in several kinds of vegetables (Table 1). However, modern systemic and contact herbicides, insecticides, and fungicides were commonly detected. These lasting synthetic chemicals should only be present in very small amounts in food for consumers. Table 1: Pesticide Residue Screening Results Vegetable Species Herbicides (Glyphosate/Atrazine) Insecticides (Permethrin/Chlorpyrifos) Fungicides (Mancozeb/ Carbendazim) Fluted Pumpkin Leaf (Telfairia occidentalis) + + + African Spinach (Amaranthus hybridus) + + - Bitter Leaf (Vernonia amygdalina) - + + Waterleaf (Talinum triangulare) + + + Scent Leaf (Ocimum gratissimum) - + - Key: (+) Detected (-) Not detected Observations from the data in Table 1 show that organophosphate and pyrethroid insecticides (Chlorpyrifos and Permethrin) were found in all five sampled vegetable species. This indicates a heavy reliance on these chemicals for pest control in the study area. Fluted Pumpkin Leaf and Waterleaf tested positive for all three types of agrochemicals: herbicides, insecticides, and fungicides. However, Scent Leaf had the lowest occurrence, testing negative for both herbicides and fungicides. This might be partly due to the plant's natural antimicrobial and insect-repellent essential oils. The findings in Table 1 show that chemical insecticides were present in all five common leafy vegetables collected from local markets. Additionally, the trace analysis in Table 2 found significant levels of herbicide residues, especially in Fluted Pumpkin Leaf and Waterleaf. This ongoing presence is linked to farmers choosing intensive chemical weed control methods instead of traditional manual clearing during the early stages of crop growth. Waterleaf, which has high moisture content and effective root-to-shoot translocation rates, absorbs polar pesticide fractions well from contaminated topsoil and runoff water. Table 2: Pesticide Residue Concentrations (mg/kg) Pesticide Class/Compound Fluted Pumpkin Leaf African Spinach Bitter Leaf Waterleaf Scent Leaf Herbicides Glyphosate 0.42 0.18 ND 0.55 ND Atrazine 0.28 ND ND 0.34 ND Insecticides Chlorpyrifos 1.15 0.74 0.62 1.38 0.45 Permethrin 0.88 0.92 0.44 0.96 0.22 Fungicides Mancozeb 0.35 ND 0.51 0.48 ND Carbendazim 0.19 ND 0.26 0.22 ND Key: ND - Not Detected (below the Limit of Detection, LOD = 0.001mg/kg). All values signify triplicate mean distributions expressed in mg/kg wet weight. Findings from the quantitative analysis in Table 2 show that waterleaf had the highest concentrations of both Glyphosate (0.55 mg/kg) and Chlorpyrifos (1.38 mg/kg), with Fluted Pumpkin Leaf close behind. Since these are two of the most commonly consumed soup ingredients in Delta State, these numbers are important for assessing dietary exposure risks. In general, insecticides, especially Chlorpyrifos and Permethrin, had much higher average values than herbicides and fungicides. All five vegetables had pesticide levels above 0.20 mg/kg for both compounds, indicating intensive application close to harvest times. Supporting the qualitative screening data, Scent Leaf had the lowest pesticide load, showing “Not Detected” for four out of the six target compounds. Thus, the data shows that fluted pumpkin leaf and waterleaf had the highest levels of pesticide residues among the selected metropolitan open markets. These high residue levels likely result from frequent chemical treatments used on peri-urban farms, along with a complete disregard for necessary pre-harvest intervals. Pesticides are stable chemicals that penetrate deep into the cellular structure of leafy greens, meaning that regular washing or home preparation routines cannot effectively remove them. Statistically, several mixtures of insecticides and fungicides exceed both national and international maximum allowable limits (Table 3). This creates serious non-carcinogenic and long-term carcinogenic health risks for consumers who may not be aware of these problems. Table 3 presents a structured comparison of the vegetable pesticide concentrations against the statutory Maximum Residue Limit standards. Table 3: Comparison of Residue Concentrations with Regulatory MRL Values Pesticide Compound Regulatory MRL (mg/kg) Fluted Pumpkin Leaf African Spinach Bitter Leaf Waterleaf Scent Leaf Glyphosate 0.10 0.42* 0.18* ND 0.55* ND Atrazine 0.05 0.28* ND ND 0.34* ND Chlorpyrifos 0.05 1.15* 0.74* 0.62* 1.38* 0.45* Permethrin 0.05 0.88* 0.92* 0.44* 0.96* 0.22* Mancozeb 0.10 0.35* ND 0.51* 0.48* ND Carbendazim 0.10 0.19* ND 0.26* 0.22* ND Key: MRL - Maximum Residue Limit established jointly by WHO / FAO (Codex Alimentarius) and NAFDAC. ND - Not Detected. (*) Asterisk - Denotes mean concentration significantly exceeds the regulatory MRL threshold based on a one-sample Student t-test at a 99% confidence interval (P = 0.01). From Table 3, every instance of pesticide residue found in all samples was well above the legal safety limits for consumers (P = 0.01). There were no cases where pesticide levels were detected safely at or below the MRL. Chlorpyrifos and Permethrin pose the greatest public health risks. For instance, the Chlorpyrifos level in Waterleaf (1.38mg/kg) is 27.6 times higher than the safety limit (0.05mg/kg), while Fluted Pumpkin Leaf is 23 times higher (1.15mg/kg). Even Scent Leaf, which had the fewest positive detections, surpassed the insecticide limit by 4 to 9 times. This widespread violation of MRL limits points to local misuse of agrochemicals, like not following proper pre- harvest intervals or over-application by farmers in the Warri and Environ agricultural supply chains. Figure 2 shows findings from the average pesticide residue concentrations compared to regulatory thresholds, highlighting selected peak exceedances from Warri and Environ. Figure 2: Comparison of Mean Pesticide Residue Concentrations vs. Regulatory MRL Limits Analysis from Figure 2 shows that chlorpyrifos in waterleaf measures 1.38 mg/kg, which is well above the safety limit of 0.05 mg/kg. This insecticide is over-concentrated by a factor of 27.6. In lumpkin leaf , chlorpyrifos levels are at 1.15 mg/kg, exceeding safety limits by 23 times. Permethrin in African spinach is also a concern, measuring 0.92 mg/kg, which is 18.4 times higher than its 0.05 mg/kg threshold. These values represent severe peaks and highlight an urgent public health issue in the agricultural networks of Warri and Environ. The data suggests that chemicals may be applied too close to harvest time, violating withholding periods, or that there is an excessive application of chemicals on crops to combat heavy tropical insect pressure. Figure 3 presents results from the survey data, mapping the main geographical supply pathways for retail vegetables in the study region. Figure 3: Primary Geographical Supply Sources of Retail Market Vegetables The findings in Figure 3 show that nearly half (46.0%) of the vegetable volume comes from the intense, localized farming areas near Effurun and the surrounding metropolitan limits of Warri. These areas often have frequent cropping cycles, which limits the time for chemical residues to break down naturally. Rural channels from the wider Outer Delta account for 38.0% of the supply. Though transport delays can sometimes act as informal waiting periods for unstable chemicals, bulk handling at these distribution points keeps a consistent level of regional exposure. In total, 84.0% of all staple leafy greens entering retail markets come from outside the immediate city limits. This reveals a direct path through which intensive agricultural chemical practices reach urban consumers. Figure 4 shows a significant lack of food safety awareness about pesticide contamination among retail buyers in Warri and the surrounding areas. Figure 4: Consumer Safety Awareness Scores and Risk Perceptions (n=200 Survey Respondents) Deductions from Figure 4 show that the largest group of respondents, 41.0% (n=82), fell into the “Critically Low” (0-2 score) category. These consumers showed little to no awareness of the health risks linked to chronic pesticide ingestion. When combined with the “Moderate” scoring group, which made up 27.0% (n=54), a large majority of consumers, 68.0%, prioritize the visual brightness and physical size of leafy greens over their safety from toxins. Only 13.0% of the surveyed population were classified as “Highly Aware” of these food safety issues related to chemistry. Conclusion Based on the experimental data from this study, highly toxic chemicals from banned pesticide classes were mostly absent in the vegetable samples collected from major retail markets in Warri and the surrounding areas. However, the leftover amounts of commonly used herbicides, insecticides, and fungicides, specifically Glyphosate, Chlorpyrifos, and Permethrin, were significantly above the maximum limits set by WHO, FAO, and NAFDAC. This poses a serious health risk through diet. Regular monitoring of pesticide residues is necessary over the long term because fresh agricultural products constantly come into the city from various peri-urban sources. 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