Distribution and Risk Assessment of Polychlorinated Biphenyls in Soil and Plants in Koko Town, Delta State, Nigeria

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Ekperusi, Ndu P. Okeke, Anthonia E. Gbuvboro This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7066469/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 13 You are reading this latest preprint version Abstract The distribution of Polychlorinated Biphenyls (PCBs) in Soils and Plants in Koko Town, Delta State, Nigeria, was studied using five soil samples and five edible plants collected from five industrial locations in the study area. Using Soxhlet apparatus and gas chromatography for the extraction of contaminants, and analysis, mean PCB concentrations were found to be significantly higher in plants (20.75mg/kg) than in soils (10.32mg/kg), exceeding the WHO safety thresholds. The sampled plants significantly accumulated PCBs in the following order; Pueraria phaseoloides > Ceiba pentandra > Chromolaena odorata > Vermonia amygdalina > Musa sapientum . Estimated daily intake of 0.000007mg/kg for adults and children and a hazard ratio of 1.0 as stipulated by USEPA, indicated substantial human health risks, especially among children. These findings underscore the ecological and toxicological urgency of controlling industrial PCB emissions in oil-producing regions. Biological sciences/Ecology Earth and environmental sciences/Ecology Earth and environmental sciences/Environmental sciences bio-accumulation Niger Delta PCBs PCBs in soils PCBs in plants human health risk Figures Figure 1 1. INTRODUCTION Polychlorinated biphenyls (PCBs) are dioxin-like chemicals of similar structure and chemistry to PCDD/Fs and, are of global concern due to their potential for long-range transport, persistence in the environment, ability to bio-magnify and bio-accumulate in biota as well as their toxicity [3]. There are no known natural sources of PCBs in the environment except anthropogenic activities such as petrochemical production, industrial and municipal wastes [21]. PCBs availability in soil and other related environmental media is determined by the chemical properties of the compound, the physical and chemical properties of the soil, and the environmental conditions at the time of exposure [26]. They are readily ingested by animals from contaminated soil and plants, and this increases the effects of this pollutant across the food web [12]. Their toxicological effects on humans have continued to evolve with a significant range of health impacts including chronic lymphocytic leukemia, soft-tissue sarcoma, hodgkin’s disease, non-hodgkin’s lymphoma, and limited evidence of association to lung cancer, prostate cancer, bronchus, laryngeal cancer, multiple myeloma, hypertension, spina bifida in offspring, early-onset transient peripheral neuropathy, and amyloidosis [7]. Studies have reported the cause-effect of consuming PCBs to significant concentrations of the lower chlorinated congeners (2-Cl to 5-Cl) above the higher chlorinated congeners (6-Cl to 10-Cl) in the environment [2,15]. In plants' potential to store contaminants, leafy vegetables have been investigated to have elevated bioaccumulating factors (BAF) for lower congeners than higher congeners [19]. Conversely, mean concentrations have been recorded low in leafy vegetables than in other crop yield [2]. The concentrations of PCB congeners vary at soil depth, in vegetables, and in other related transport systems in the environment [3]. This relative is attributed to factors such as differential adsorption rate in soils, soil abstraction, translocation, variation in aerial uptake, soil stability and composition, climatic conditions, resistance to degradation, and plant uptake [6]. These characteristics are typically exhibited in tropical soils as found in Koko Town [4]. Several research has shown that the concentrations of PCBs in vegetables fall below the World Health Organization (WHO) standards of ≥ 400 g/day and the Food and Drug Administration (FDA) [11] recommended tolerances of 200-3000ng/g [2,9,19,26]. Regardless of these discoveries, the sum of PCB concentrations can develop a high toxicity equivalent to the most toxic dioxin congeners [2]. The release of PCBs from industrial activities, the ability of lower congeners of PCBs to bioaccumulate significantly in soils, and the potential of leafy vegetables to absorb lower concentrations of PCBs from the environment has necessitated this study to be carried out in the oil-producing area of Koko. In Koko, historic and ongoing waste dumping has intensified concerns over plant and soil contamination. While previous studies have addressed individual congeners, comprehensive risk assessment for commonly consumed edible plants in this region remains limited. Hence, the present study focuses on the potential of vegetables to accumulate PCBs in general and not on specific congeners. The purpose was to investigate the distribution of polychlorinated biphenyls (PCBs) in soils and plants in Koko town, Delta State, Nigeria. The objectives were to determine: (1) PCB concentrations in soils and plants; (2) bioaccumulation concentrations in soils and plants; and (3) risk assessment to humans. 2. MATERIALS AND METHODS 2.1 Study Location The study area was Koko, which is the headquarters of Warri North Local Government Area, Delta State, Nigeria, with geographical coordinates of 5°44ʹ0ʺ, 6°08ʹ0ʺN and 5°4ʹ0ʺ, 5°36ʹ0ʺE (Fig. 1 ). The climatic condition of the area is of typical tropical rainforest with an annual rainfall of 2000mm to 3000mm yearly. It experiences the wet and dry seasons annually but more of the wet season. The area has a mean temperature of 21–35°C and a relative humidity of 90%-60% seasonally. It consists of adjoining rivers used for fishing and movement of commercial goods, flowing in and out of the town and empties in the Gulf of Guinea, of the Atlantic Ocean. The town is a hub of oil activities and other commercial farming products of palm oil, cassava, fruits, etc. Nevertheless, it became known globally following the dumping of hazardous wastes in the 1980s, which prompted international and national concerns about the effects it posed on human health, agriculture, and other commercial activities that were beneficial to the town. 2.2 Sample collection Plants and soil samples (PSS) were collected from the vicinity of the five industrial sites of potential sources of contamination, using a stratified random technique with the aid of a global positioning system (GPS 73-Garmin). The sample locations were categorized as follows: Koko Seaport (site 1), plant and lubricant production company (site 2), industrial waste treatment company (site 3), conglomerate of oil shipping companies (site 4), and bitumen production company (site 5). For soil representatives, the study area was divided into 10 by 10m area, and composite samples of topsoil (0–15cm) and subsoil (15–30cm) were collected in quintuplets using soil augers. In each sampling location, the soil samples were and wrapped in aluminum foil, labelled with markers, and placed in an ice chest to preserve their soil moisture while, leguminous plants such as silk-cotton ( Ceiba pentandra.) , kudzu (Pueraria phaseoloides)- an invasive vine used for medicinal purposes, bitter leaf (Vermonia amygdalina) , banana ( Musa sapientum) and awolowo leaf ( Chromolaena odorata) were sampled and 20–30 leaves per plant were collected, placed in zip-locks to keep plant texture and moisture and labelled properly. Plants were selected following Plank’s [20] method for the determination of plant growth and maturity. Identification was carried out by Amaka Michael and Akinnibosun H. Adewale. Voucher specimen of the plant species (UBH-C531 Ceiba pentandra , UBH-P565 Pueraria phaseoloides , UBH-V342 Vermonia amygdalina , UBH-M416 Musa sapientum. and UBH-C496 Chromolaena odorata) were deposited at the University of Benin Herbarium. Both soil and plants samples were transported to the EISL Laboratory in Port Harcourt for analysis. 2.3 Sample Preparation Reagents A measured 10g soil sample was extracted using Method 3540 (Soxhlet) to extract the nonvolatile and semi-volatile organic PCB compounds from the soil. The extracts for PCB analysis were subjected to a sequential hexane cleanup (Method 8082) according to USEPA [22]. After cleanup, the extract was analyzed by injecting a measured aliquot into a gas chromatograph (Agilent 7890A) equipped with a wide-bore fused silica capillary column, an electron capture detector (GC/ECD) and a GC-MS confirmation. Plant samples were air-dried for seven days in a fume hood at 60°C temperature to a constant weight of 10g and ground to powder. 2g of the plant material was placed in a cellulose thimble and extracted by heating the flask until the hexane solvent vaporizes, condenses, and drips on the plant material to extract the PCBs. This continued for 6 hours using a Soxhlet extractor until the solvent was colourless and odourless. Impurities were removed using column chromatography, and the extract was analyzed for PCBs using a GC-MS. 2.4 Quality Control and Quality Assurance All equipment used for analysis was calibrated to standards. The detected concentrations of targeted compounds were compared with certified reference materials following the Acq Method 3540 and multi-level calibration standards. For quantification, calibration curves were constructed for PCBs compounds using a series level of quantification values (Q- values) for both low and high chlorinated congeners. The quantitation ion (QIon) was a constant of 57 for higher congeners and precisely 149 for the PCB-167 in plant samples at sites 1,2 and 5 with varying responses. 2.5 Data Analysis Data of PSS were analysed using SPSS version 25.0. This supported the computation and presentation of the analysed results into mean and standard deviation. Comparative analysis using ANOVA was carried out at a probability level of 0.05 (95% confidence level). 2.6 Bioaccumulation factor The bioaccumulation factor was calculated by dividing the concentration of PCBs in plants as against the concentration in soil. BAF = Concentration Plant / Concentration Soil (1) 2.7 Human Health Risk Assessment To evaluate the human health risk associated with the consumption of edible plants contaminated with PCBs, the risk assessment was calculated using the estimated daily intake (EDI) and hazard ratio (HR). The EDI was calculated by using Eq. (2). EDI = C × CR/BW (2) where EDI = the estimated daily intake for edible plants (mg kg − 1 day − 1 ), C = PCB concentration in plant in mg kg − 1 , CR = plant ingestion rate using FAO Food Balance Sheets for Nigeria [10] and BW = average body weight for Nigerians, which is 60.7kg for adults [24] and 30kg for children [13]. The hazard ratio was calculated following Eq. (3). HR = EDI/RfD (3) where, RfD = reference dose factors according to the United States Environmental Protection Agency values [23]. 3. RESULTS AND DISCUSSION 3.1 Mean Concentration of PCBs The result revealed the concentrations of 28 PCB compounds in soils and five species of plants in Table 1 . Amongst the analyzed compounds are 12 dioxin-like PCBs (DL-PCBs) (77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and 189), which have similar toxicity as 2,3,7,8-TCDD and non-dioxin-like PCBs (NDL-PCBs). The concentrations of 27 compounds were higher than the permissible limits for soil except for PCB-167, with no recorded concentration, and all the analyzed compounds for plants [8]. PCB-66 exhibited the highest concentrations across both soil and plant samples in Table 1 , suggesting high mobility and uptake potential and, aligns with its known volatility and widespread industrial use. The higher chlorinated compounds were concentrated moderately in the PSS. The compounds were PCBs 114,118 in soils, while in plants, were PCBs 126, 153, 169, 170, 180, 187, 195, 206, and 209. The translocation of this persistent pollutant in biota has been elaborated previously by Cheng et al. [6] as against concentrations recorded in Arshad et al. [2]. Table 1 Summary concentration (mean + standard deviation) of PCB in soil and plants in Koko, Delta State Soil Plant P-Value PCB-8 8.52 ± 12.91 26.68 ± 12.29 P > 0.05 PCB-18 6.27 ± 8.74 9.01 ± 2.86 P > 0.05 PCB-28 1.27 ± 1.82 1.76 ± 0.71 P > 0.05 PCB-44 9.37 ± 11.99 11.9 ± 3.27 P > 0.05 PCB-52 9.4 ± 12.2 32.25 ± 51.67 P > 0.05 PCB-66 37.82 ± 46.27 116.72 ± 84.4 P > 0.05 PCB-77 3.55 ± 4.32 20.75 ± 28.37 P > 0.05 PCB-81 6.93 ± 8.09 16.06 ± 6.21 P > 0.05 PCB-101 6.27 ± 0.25 4.1 ± 1.16 P > 0.05 PCB-105 10.32 ± 15.25 11.36 ± 5.15 P > 0.05 PCB-114 12.49 ± 20.95 28.84 ± 16 P > 0.05 PCB-118 16.79 ± 16.96 13.04 ± 3.68 P > 0.05 PCB-123 5.68 ± 8.97 7.07 ± 6.92 P > 0.05 PCB-126 9.85 ± 14.23 12.49 ± 3.62 P > 0.05 PCB-128 1.85 ± 2.23 1.3 ± 0.81 P > 0.05 PCB-138 2.05 ± 2.08 2.71 ± 2.23 P > 0.05 PCB-153 4.32 ± 4.03 13.17 ± 15.03 P > 0.05 PCB-156 0.98 ± 1.3 0.95 ± 0.42 P > 0.05 PCB-157 1.57 ± 1.91 2.42 ± 8.17 P > 0.05 PCB-167 0 ± 0 4.57 ± 6.55 P > 0.05 PCB-169 4.47 ± 5.03 33.72 ± 65.45 P > 0.05 PCB-170 2.91 ± 2.57 12.32 ± 10.04 P > 0.05 PCB-180 2.96 ± 4.02 38.34 ± 37.37 P > 0.05 PCB-187 3.63 ± 5.1 13.78 ± 17.43 P > 0.05 PCB-189 11.85 ± 16.42 1.76 ± 2.32 P > 0.05 PCB-195 6.86 ± 7.95 22.02 ± 22.73 P > 0.05 PCB-206 10.91 ± 19.23 19.41 ± 20.32 P > 0.05 PCB-209 3.48 ± 1.83 46.68 ± 83.46 P > 0.05 3.2 Bioaccumulation factor (BAF) The bioaccumulation factor reflects the accumulation of contaminants in a biota compared to the concentration in the surroundings. This makes it important to determine the concentrations of PCBs in plants in contrast to those in soils. In this study, the calculated BAF values were > 1 except in Site 4 which recorded BAF value below 1 (Table 2 ). The significantly elevated BAF in P. phaseoloides may be due to its extensive root system and medicinal use, which raises further concerns over human exposure through traditional plant consumption. The BAF values for the sampled sites were in the decreasing order of Site 2 > Site 1 > Site 5 > Site 3 > Site 4. This is corroborated by studies of significant concentrations of PCBs in hyper-accumulating plant-based foods from the surroundings [16–18]. Table 2 Bioaccumulation factor for dioxins congeners in soil and plant collected from Koko, Delta State. Sites Plants Soil BAF Site 1 22.87 0.71 32.21 Site 2 18.53 0.42 44.12 Site 3 14.09 7.74 1.82 Site 4 8.96 14.91 0.6 Site 5 30.28 11.97 2.53 3.3 Health Risk Assessment to Humans The most notable pathway of exposure to PCBs is through ingestion (food or dietary) nevertheless, there have been inconsistent research on vegetables and other leguminous products which have been specified to the low concentrations of PCBs in plants. Table 3 shows the calculated estimated daily intake and hazard ratio to estimate the risk levels associated with PCB concentrations in the studied plants for adults and children. The EDI reveals the average daily intake of PCBs through edible plants consumption for both adults and children compared to the reference dose. An HR value less than 1.0 indicates a low threat, while a value above 1.0 means a high threat. The permissible daily intake for PCBs by FAO [10] is 0.000007mg/kg and hazard ratio equal 1.0 by USEPA [23] however, the calculated EDI and HR was higher than the FAO [10] and USEPA [23] standards which clearly depicts health danger. From Table 3 below, the daily intake of PCB concentrates was highest in V. amygdalina except for C. pentandra whose values fell below the stipulated permissible limit. Hazard ratios exceeded 1.0 for all species except C. pentandra , indicating a considerable health risk. The highest HR values in C. odorata and P. phaseoloides highlight their role as hyperaccumulators. Given the widespread use of these plants in traditional medicine and diet, the implications for chronic exposure are significant. These results from both the estimated daily intake and the hazard ratio satisfy studies by Bantum et al. [4], Irerhievwie et al. [15], and Aziza et al. [3] whose work covers the soil contamination from PCBs along the borders of Warri North as well as the impacts associated from industrial activities, the seasonal variation of temperature, rainfall and other abiotic factors that aid the translocation of PCB pollutants in plants in the area from the environment. Furthermore, the rate of absorption of the contaminants in these plants and their translocation potentials from soil is confirmed to be true [6,25]. The results in Table 3 strongly contradicts the estimated daily intake from studies by Arshad et al ., Esposito et al ., Olatunji and Zhang et al ., [2,9,19,26], whose values fell below the WHO/FAO permissible limits. Table 3 Human Health Risk Assessment from Edible plants in Koko, Delta State. Risk Indicator Categories Ceiba pentandra Pueraria phaseoloides Vermonia amygdalina Musa sapientum Chromolaena odorata EDI Adult 0.000003 0.001562 0.000812 0.000152 0.002553 Children 0.000005 0.003161 0.001643 0.000307 0.005166 HR Adult 0.38 223.19 116.01 21.64 364.77 Children 0.76 451.60 234.73 43.82 738.05 The chief contributors to these values in the edible plants include shipment of oil and gas consignments, production of paints and lubricants, management of petroleum wastes as well as dumpsite of hazardous wastes and bitumen production. The edible hyper-accumulating plants such as C. odorata popularly known as Awolowo leaf in Africa and V. amygdalina also known as bitter leaf, have been discovered beneficial to human health because of their antibacterial and antioxidant properties [5,14]. Yet, the capacity of the studied plants to accumulate contaminants of concern, makes them good genetically-modified materials for phytoremediation while harmful to the ecosystem [26]. Environmental contamination of the persistent organic pollutant (PCBs) is comprehensive and serves as an interesting tool in the study of toxicity effects on humans [1,12]. CONCLUSION The study reveals critical levels of PCB contamination in soils and edible plants in Koko, Delta State. The substantial bioaccumulation, especially in P. phaseoloides and C. odorata , poses a serious threat to public health. These findings advocate for urgent regulatory action, phytoremediation strategies, and routine environmental monitoring to mitigate long-term exposure in oil-impacted communities. This is a red flag on fruit/vegetable consumption in this region which transcends globally in industrial areas, as this study provides baseline concentrations of PCBs on edible plants in Koko, Delta State, Nigeria. Lower congeners of PCBs are highly adsorbed in soils along the Niger Delta coasts which raises concern over industrial operations in Koko and its environs. Soil biodiversity and public health are at maximal danger and it is needful that anthropogenic sources be minimized to the barest levels to reduce PCB concentrations in the environment. Declarations All authors have read, understood, and have complied as applicable with the statement on "Ethical responsibilities of Authors" as found in the Instructions for Authors and are aware that with minor exceptions, no changes can be made to authorship once the paper is submitted. Acknowledgement The field experiment was carried out in Warri North, Niger Delta region of Nigeria. The laboratory analysis was done in Ebic Integrated Services Limited (EISL) Laboratory, Rivers state, Nigeria. Funding The authors declare that no funds, grants, or other support was received during the preparation of this manuscript. Author Contributions Amaka Michael, prepared the manuscript, interpreted the results and wrote the paper, Abraham O. Ekperusi revised the work, Ndu P. Okeke initiated the study, and Anthonia E. Gbuvboro wrote the summary. All authors read and approve the final manuscript. Ethical Approval No ethical approval is required for this study. Approval for Animal Experiments This is not applicable. Approval for Human Experiments This is not applicable. Research involving plants The study was conducted in accordance with relevant institutional guidelines and regulations. Consent to Participate/Consent to Publish This is not applicable. Dual Publication This is not applicable as the data represented in this study is original. Permission to use third-party material This is not applicable. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Data availability statement All data generated and analyzed during this study are included in this published article (and its supplementary files). References Akhionbare, S. M. O. The Environment “Concepts, issues and control of pollution”. 2 nd ed. 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Supplementary Files MichaelA.rawdata.xlsx Cite Share Download PDF Status: Published Journal Publication published 18 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 26 Aug, 2025 Reviews received at journal 22 Aug, 2025 Reviewers agreed at journal 17 Aug, 2025 Reviews received at journal 16 Aug, 2025 Reviewers agreed at journal 10 Aug, 2025 Reviewers agreed at journal 29 Jul, 2025 Reviewers agreed at journal 27 Jul, 2025 Reviewers agreed at journal 15 Jul, 2025 Reviewers invited by journal 15 Jul, 2025 Editor assigned by journal 15 Jul, 2025 Editor invited by journal 15 Jul, 2025 Submission checks completed at journal 13 Jul, 2025 First submitted to journal 13 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7066469","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":486763583,"identity":"6eb1ae05-3cf4-441d-ab3c-116fad2eb75d","order_by":0,"name":"Amaka Michael","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYDACZgaGAwwGDAlAVgPDhwqQCJBBpBbGBsYZZ0AijAS0QAFYCzNvG4hNQItuO3fioRsFdnn87Y3NH3jn1UbztwO1/KjYhlOL2WHeDYdzDJKLJc4cbJOQ3HY8d8ZhoAt7ztwmpOVAYsONxDYGw23HchuAWpgZ24jQMv/+w+YPiXOO5c4nWsuGG4wNEgcbanI3EKklOXHjmcQ2yYZjB3I3ArUcxOuX82c3f875Y5c47/jhw5//1NTlzjt/+OCDHxW4taCDw2DyANHqgaCOFMWjYBSMglEwQgAAvdJnfN/g0s0AAAAASUVORK5CYII=","orcid":"","institution":"Nigeria Maritime University","correspondingAuthor":true,"prefix":"","firstName":"Amaka","middleName":"","lastName":"Michael","suffix":""},{"id":486763584,"identity":"c297b668-9c7c-4611-8732-5516f60205dd","order_by":1,"name":"Abraham O. Ekperusi","email":"","orcid":"","institution":"Nigeria Maritime University","correspondingAuthor":false,"prefix":"","firstName":"Abraham","middleName":"O.","lastName":"Ekperusi","suffix":""},{"id":486763585,"identity":"025356c1-4065-4429-8153-aec856b19d83","order_by":2,"name":"Ndu P. Okeke","email":"","orcid":"","institution":"Federal University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Ndu","middleName":"P.","lastName":"Okeke","suffix":""},{"id":486763586,"identity":"63df9a7a-4d57-4a34-a9b8-c499dc2d3e16","order_by":3,"name":"Anthonia E. Gbuvboro","email":"","orcid":"","institution":"Nigeria Maritime University","correspondingAuthor":false,"prefix":"","firstName":"Anthonia","middleName":"E.","lastName":"Gbuvboro","suffix":""}],"badges":[],"createdAt":"2025-07-07 14:23:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7066469/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7066469/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-33241-x","type":"published","date":"2025-12-18T15:58:40+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":87271964,"identity":"c37b3014-9eac-4cb8-b103-c0a906d743e4","added_by":"auto","created_at":"2025-07-22 08:25:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":557798,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Study Area\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7066469/v1/4147c4e9a1a72bbc53276451.png"},{"id":98815233,"identity":"4bd320b2-5eee-4879-bbed-bcd4a2fde7d9","added_by":"auto","created_at":"2025-12-22 16:14:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1283131,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7066469/v1/1371354f-22a1-41e3-a9a9-c2c38bf779d8.pdf"},{"id":87271960,"identity":"219b741f-75fa-4a49-9573-62a7d499beb3","added_by":"auto","created_at":"2025-07-22 08:25:08","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":17029,"visible":true,"origin":"","legend":"","description":"","filename":"MichaelA.rawdata.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-7066469/v1/af7b97fbb896b875f64eaee1.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Distribution and Risk Assessment of Polychlorinated Biphenyls in Soil and Plants in Koko Town, Delta State, Nigeria","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003ePolychlorinated biphenyls (PCBs) are dioxin-like chemicals of similar structure and chemistry to PCDD/Fs and, are of global concern due to their potential for long-range transport, persistence in the environment, ability to bio-magnify and bio-accumulate in biota as well as their toxicity [3]. There are no known natural sources of PCBs in the environment except anthropogenic activities such as petrochemical production, industrial and municipal wastes [21]. PCBs availability in soil and other related environmental media is determined by the chemical properties of the compound, the physical and chemical properties of the soil, and the environmental conditions at the time of exposure [26]. They are readily ingested by animals from contaminated soil and plants, and this increases the effects of this pollutant across the food web [12]. Their toxicological effects on humans have continued to evolve with a significant range of health impacts including chronic lymphocytic leukemia, soft-tissue sarcoma, hodgkin\u0026rsquo;s disease, non-hodgkin\u0026rsquo;s lymphoma, and limited evidence of association to lung cancer, prostate cancer, bronchus, laryngeal cancer, multiple myeloma, hypertension, spina bifida in offspring, early-onset transient peripheral neuropathy, and amyloidosis [7].\u003c/p\u003e\u003cp\u003eStudies have reported the cause-effect of consuming PCBs to significant concentrations of the lower chlorinated congeners (2-Cl to 5-Cl) above the higher chlorinated congeners (6-Cl to 10-Cl) in the environment [2,15]. In plants' potential to store contaminants, leafy vegetables have been investigated to have elevated bioaccumulating factors (BAF) for lower congeners than higher congeners [19]. Conversely, mean concentrations have been recorded low in leafy vegetables than in other crop yield [2]. The concentrations of PCB congeners vary at soil depth, in vegetables, and in other related transport systems in the environment [3]. This relative is attributed to factors such as differential adsorption rate in soils, soil abstraction, translocation, variation in aerial uptake, soil stability and composition, climatic conditions, resistance to degradation, and plant uptake [6]. These characteristics are typically exhibited in tropical soils as found in Koko Town [4].\u003c/p\u003e\u003cp\u003eSeveral research has shown that the concentrations of PCBs in vegetables fall below the World Health Organization (WHO) standards of \u0026ge;\u0026thinsp;400 g/day and the Food and Drug Administration (FDA) [11] recommended tolerances of 200-3000ng/g [2,9,19,26]. Regardless of these discoveries, the sum of PCB concentrations can develop a high toxicity equivalent to the most toxic dioxin congeners [2].\u003c/p\u003e\u003cp\u003eThe release of PCBs from industrial activities, the ability of lower congeners of PCBs to bioaccumulate significantly in soils, and the potential of leafy vegetables to absorb lower concentrations of PCBs from the environment has necessitated this study to be carried out in the oil-producing area of Koko. In Koko, historic and ongoing waste dumping has intensified concerns over plant and soil contamination. While previous studies have addressed individual congeners, comprehensive risk assessment for commonly consumed edible plants in this region remains limited. Hence, the present study focuses on the potential of vegetables to accumulate PCBs in general and not on specific congeners. The purpose was to investigate the distribution of polychlorinated biphenyls (PCBs) in soils and plants in Koko town, Delta State, Nigeria. The objectives were to determine: (1) PCB concentrations in soils and plants; (2) bioaccumulation concentrations in soils and plants; and (3) risk assessment to humans.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Study Location\u003c/h2\u003e\u003cp\u003eThe study area was Koko, which is the headquarters of Warri North Local Government Area, Delta State, Nigeria, with geographical coordinates of 5\u0026deg;44ʹ0ʺ, 6\u0026deg;08ʹ0ʺN and 5\u0026deg;4ʹ0ʺ, 5\u0026deg;36ʹ0ʺE (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The climatic condition of the area is of typical tropical rainforest with an annual rainfall of 2000mm to 3000mm yearly. It experiences the wet and dry seasons annually but more of the wet season. The area has a mean temperature of 21\u0026ndash;35\u0026deg;C and a relative humidity of 90%-60% seasonally. It consists of adjoining rivers used for fishing and movement of commercial goods, flowing in and out of the town and empties in the Gulf of Guinea, of the Atlantic Ocean. The town is a hub of oil activities and other commercial farming products of palm oil, cassava, fruits, etc. Nevertheless, it became known globally following the dumping of hazardous wastes in the 1980s, which prompted international and national concerns about the effects it posed on human health, agriculture, and other commercial activities that were beneficial to the town.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Sample collection\u003c/h2\u003e\u003cp\u003ePlants and soil samples (PSS) were collected from the vicinity of the five industrial sites of potential sources of contamination, using a stratified random technique with the aid of a global positioning system (GPS 73-Garmin). The sample locations were categorized as follows: Koko Seaport (site 1), plant and lubricant production company (site 2), industrial waste treatment company (site 3), conglomerate of oil shipping companies (site 4), and bitumen production company (site 5). For soil representatives, the study area was divided into 10 by 10m area, and composite samples of topsoil (0\u0026ndash;15cm) and subsoil (15\u0026ndash;30cm) were collected in quintuplets using soil augers. In each sampling location, the soil samples were and wrapped in aluminum foil, labelled with markers, and placed in an ice chest to preserve their soil moisture while, leguminous plants such as silk-cotton (\u003cem\u003eCeiba pentandra.)\u003c/em\u003e, kudzu \u003cem\u003e(Pueraria phaseoloides)-\u003c/em\u003e an invasive vine used for medicinal purposes, bitter leaf \u003cem\u003e(Vermonia amygdalina)\u003c/em\u003e, banana (\u003cem\u003eMusa sapientum)\u003c/em\u003e and awolowo leaf (\u003cem\u003eChromolaena odorata)\u003c/em\u003e were sampled and 20\u0026ndash;30 leaves per plant were collected, placed in zip-locks to keep plant texture and moisture and labelled properly. Plants were selected following Plank\u0026rsquo;s [20] method for the determination of plant growth and maturity. Identification was carried out by Amaka Michael and Akinnibosun H. Adewale. Voucher specimen of the plant species (UBH-C531 \u003cem\u003eCeiba pentandra\u003c/em\u003e, UBH-P565 \u003cem\u003ePueraria phaseoloides\u003c/em\u003e, UBH-V342 \u003cem\u003eVermonia amygdalina\u003c/em\u003e, UBH-M416 \u003cem\u003eMusa sapientum.\u003c/em\u003e and UBH-C496 \u003cem\u003eChromolaena odorata)\u003c/em\u003e were deposited at the University of Benin Herbarium. Both soil and plants samples were transported to the EISL Laboratory in Port Harcourt for analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Sample Preparation Reagents\u003c/h2\u003e\u003cp\u003eA measured 10g soil sample was extracted using Method 3540 (Soxhlet) to extract the nonvolatile and semi-volatile organic PCB compounds from the soil. The extracts for PCB analysis were subjected to a sequential hexane cleanup (Method 8082) according to USEPA [22]. After cleanup, the extract was analyzed by injecting a measured aliquot into a gas chromatograph (Agilent 7890A) equipped with a wide-bore fused silica capillary column, an electron capture detector (GC/ECD) and a GC-MS confirmation. Plant samples were air-dried for seven days in a fume hood at 60\u0026deg;C temperature to a constant weight of 10g and ground to powder. 2g of the plant material was placed in a cellulose thimble and extracted by heating the flask until the hexane solvent vaporizes, condenses, and drips on the plant material to extract the PCBs. This continued for 6 hours using a Soxhlet extractor until the solvent was colourless and odourless. Impurities were removed using column chromatography, and the extract was analyzed for PCBs using a GC-MS.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Quality Control and Quality Assurance\u003c/h2\u003e\u003cp\u003eAll equipment used for analysis was calibrated to standards. The detected concentrations of targeted compounds were compared with certified reference materials following the Acq Method 3540 and multi-level calibration standards. For quantification, calibration curves were constructed for PCBs compounds using a series level of quantification values (Q- values) for both low and high chlorinated congeners. The quantitation ion (QIon) was a constant of 57 for higher congeners and precisely 149 for the PCB-167 in plant samples at sites 1,2 and 5 with varying responses.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Data Analysis\u003c/h2\u003e\u003cp\u003eData of PSS were analysed using SPSS version 25.0. This supported the computation and presentation of the analysed results into mean and standard deviation. Comparative analysis using ANOVA was carried out at a probability level of 0.05 (95% confidence level).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Bioaccumulation factor\u003c/h2\u003e\u003cp\u003eThe bioaccumulation factor was calculated by dividing the concentration of PCBs in plants as against the concentration in soil.\u003c/p\u003e\u003cp\u003eBAF\u0026thinsp;=\u0026thinsp;Concentration\u003csub\u003ePlant\u003c/sub\u003e / Concentration\u003csub\u003eSoil\u003c/sub\u003e (1)\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7 Human Health Risk Assessment\u003c/h2\u003e\u003cp\u003eTo evaluate the human health risk associated with the consumption of edible plants contaminated with PCBs, the risk assessment was calculated using the estimated daily intake (EDI) and hazard ratio (HR). The EDI was calculated by using Eq.\u0026nbsp;(2).\u003c/p\u003e\u003cp\u003eEDI\u0026thinsp;=\u0026thinsp;C \u0026times; CR/BW (2)\u003c/p\u003e\u003cp\u003ewhere EDI\u0026thinsp;=\u0026thinsp;the estimated daily intake for edible plants (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), C\u0026thinsp;=\u0026thinsp;PCB concentration in plant in mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, CR\u0026thinsp;=\u0026thinsp;plant ingestion rate using FAO Food Balance Sheets for Nigeria [10] and BW\u0026thinsp;=\u0026thinsp;average body weight for Nigerians, which is 60.7kg for adults [24] and 30kg for children [13].\u003c/p\u003e\u003cp\u003eThe hazard ratio was calculated following Eq.\u0026nbsp;(3).\u003c/p\u003e\u003cp\u003eHR\u0026thinsp;=\u0026thinsp;EDI/RfD (3)\u003c/p\u003e\u003cp\u003ewhere, RfD\u0026thinsp;=\u0026thinsp;reference dose factors according to the United States Environmental Protection Agency values [23].\u003c/p\u003e\u003c/div\u003e"},{"header":"3. RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Mean Concentration of PCBs\u003c/h2\u003e\u003cp\u003eThe result revealed the concentrations of 28 PCB compounds in soils and five species of plants in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Amongst the analyzed compounds are 12 dioxin-like PCBs (DL-PCBs) (77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and 189), which have similar toxicity as 2,3,7,8-TCDD and non-dioxin-like PCBs (NDL-PCBs). The concentrations of 27 compounds were higher than the permissible limits for soil except for PCB-167, with no recorded concentration, and all the analyzed compounds for plants [8]. PCB-66 exhibited the highest concentrations across both soil and plant samples in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, suggesting high mobility and uptake potential and, aligns with its known volatility and widespread industrial use. The higher chlorinated compounds were concentrated moderately in the PSS. The compounds were PCBs 114,118 in soils, while in plants, were PCBs 126, 153, 169, 170, 180, 187, 195, 206, and 209. The translocation of this persistent pollutant in biota has been elaborated previously by Cheng et al. [6] as against concentrations recorded in Arshad et al. [2].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary concentration (mean\u0026thinsp;+\u0026thinsp;standard deviation) of PCB in soil and plants in Koko, Delta State\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSoil\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePlant\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-Value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e8.52\u0026thinsp;\u0026plusmn;\u0026thinsp;12.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e26.68\u0026thinsp;\u0026plusmn;\u0026thinsp;12.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.27\u0026thinsp;\u0026plusmn;\u0026thinsp;8.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e9.01\u0026thinsp;\u0026plusmn;\u0026thinsp;2.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e1.27\u0026thinsp;\u0026plusmn;\u0026thinsp;1.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e9.37\u0026thinsp;\u0026plusmn;\u0026thinsp;11.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e11.9\u0026thinsp;\u0026plusmn;\u0026thinsp;3.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e9.4\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e32.25\u0026thinsp;\u0026plusmn;\u0026thinsp;51.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e37.82\u0026thinsp;\u0026plusmn;\u0026thinsp;46.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e116.72\u0026thinsp;\u0026plusmn;\u0026thinsp;84.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e3.55\u0026thinsp;\u0026plusmn;\u0026thinsp;4.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e20.75\u0026thinsp;\u0026plusmn;\u0026thinsp;28.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.93\u0026thinsp;\u0026plusmn;\u0026thinsp;8.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e16.06\u0026thinsp;\u0026plusmn;\u0026thinsp;6.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-101\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-105\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e10.32\u0026thinsp;\u0026plusmn;\u0026thinsp;15.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e11.36\u0026thinsp;\u0026plusmn;\u0026thinsp;5.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-114\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e12.49\u0026thinsp;\u0026plusmn;\u0026thinsp;20.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e28.84\u0026thinsp;\u0026plusmn;\u0026thinsp;16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-118\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e16.79\u0026thinsp;\u0026plusmn;\u0026thinsp;16.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e13.04\u0026thinsp;\u0026plusmn;\u0026thinsp;3.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-123\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5.68\u0026thinsp;\u0026plusmn;\u0026thinsp;8.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e7.07\u0026thinsp;\u0026plusmn;\u0026thinsp;6.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-126\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e9.85\u0026thinsp;\u0026plusmn;\u0026thinsp;14.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e12.49\u0026thinsp;\u0026plusmn;\u0026thinsp;3.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-128\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e1.85\u0026thinsp;\u0026plusmn;\u0026thinsp;2.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-138\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e2.05\u0026thinsp;\u0026plusmn;\u0026thinsp;2.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e2.71\u0026thinsp;\u0026plusmn;\u0026thinsp;2.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-153\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e4.32\u0026thinsp;\u0026plusmn;\u0026thinsp;4.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e13.17\u0026thinsp;\u0026plusmn;\u0026thinsp;15.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-156\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e0.98\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e0.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-157\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e1.57\u0026thinsp;\u0026plusmn;\u0026thinsp;1.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e2.42\u0026thinsp;\u0026plusmn;\u0026thinsp;8.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-167\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e4.57\u0026thinsp;\u0026plusmn;\u0026thinsp;6.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-169\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e4.47\u0026thinsp;\u0026plusmn;\u0026thinsp;5.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e33.72\u0026thinsp;\u0026plusmn;\u0026thinsp;65.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-170\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e2.91\u0026thinsp;\u0026plusmn;\u0026thinsp;2.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e12.32\u0026thinsp;\u0026plusmn;\u0026thinsp;10.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-180\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e2.96\u0026thinsp;\u0026plusmn;\u0026thinsp;4.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e38.34\u0026thinsp;\u0026plusmn;\u0026thinsp;37.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-187\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e3.63\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e13.78\u0026thinsp;\u0026plusmn;\u0026thinsp;17.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-189\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e11.85\u0026thinsp;\u0026plusmn;\u0026thinsp;16.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e1.76\u0026thinsp;\u0026plusmn;\u0026thinsp;2.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-195\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.86\u0026thinsp;\u0026plusmn;\u0026thinsp;7.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e22.02\u0026thinsp;\u0026plusmn;\u0026thinsp;22.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-206\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e10.91\u0026thinsp;\u0026plusmn;\u0026thinsp;19.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e19.41\u0026thinsp;\u0026plusmn;\u0026thinsp;20.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCB-209\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e3.48\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e46.68\u0026thinsp;\u0026plusmn;\u0026thinsp;83.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Bioaccumulation factor (BAF)\u003c/h2\u003e\u003cp\u003eThe bioaccumulation factor reflects the accumulation of contaminants in a biota compared to the concentration in the surroundings. This makes it important to determine the concentrations of PCBs in plants in contrast to those in soils. In this study, the calculated BAF values were \u0026gt;\u0026thinsp;1 except in Site 4 which recorded BAF value below 1 (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The significantly elevated BAF in \u003cem\u003eP. phaseoloides\u003c/em\u003e may be due to its extensive root system and medicinal use, which raises further concerns over human exposure through traditional plant consumption. The BAF values for the sampled sites were in the decreasing order of Site 2\u0026thinsp;\u0026gt;\u0026thinsp;Site 1\u0026thinsp;\u0026gt;\u0026thinsp;Site 5\u0026thinsp;\u0026gt;\u0026thinsp;Site 3\u0026thinsp;\u0026gt;\u0026thinsp;Site 4. This is corroborated by studies of significant concentrations of PCBs in hyper-accumulating plant-based foods from the surroundings [16\u0026ndash;18].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBioaccumulation factor for dioxins congeners in soil and plant collected from Koko, Delta State.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSites\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePlants\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSoil\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBAF\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e32.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e18.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e44.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e14.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.82\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite 4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite 5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e11.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.53\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Health Risk Assessment to Humans\u003c/h2\u003e\u003cp\u003eThe most notable pathway of exposure to PCBs is through ingestion (food or dietary) nevertheless, there have been inconsistent research on vegetables and other leguminous products which have been specified to the low concentrations of PCBs in plants. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the calculated estimated daily intake and hazard ratio to estimate the risk levels associated with PCB concentrations in the studied plants for adults and children. The EDI reveals the average daily intake of PCBs through edible plants consumption for both adults and children compared to the reference dose. An HR value less than 1.0 indicates a low threat, while a value above 1.0 means a high threat. The permissible daily intake for PCBs by FAO [10] is 0.000007mg/kg and hazard ratio equal 1.0 by USEPA [23] however, the calculated EDI and HR was higher than the FAO [10] and USEPA [23] standards which clearly depicts health danger.\u003c/p\u003e\u003cp\u003eFrom Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e below, the daily intake of PCB concentrates was highest in \u003cem\u003eV. amygdalina\u003c/em\u003e except for \u003cem\u003eC. pentandra\u003c/em\u003e whose values fell below the stipulated permissible limit. Hazard ratios exceeded 1.0 for all species except \u003cem\u003eC. pentandra\u003c/em\u003e, indicating a considerable health risk. The highest HR values in \u003cem\u003eC. odorata\u003c/em\u003e and \u003cem\u003eP. phaseoloides\u003c/em\u003e highlight their role as hyperaccumulators. Given the widespread use of these plants in traditional medicine and diet, the implications for chronic exposure are significant. These results from both the estimated daily intake and the hazard ratio satisfy studies by Bantum et al. [4], Irerhievwie et al. [15], and Aziza et al. [3] whose work covers the soil contamination from PCBs along the borders of Warri North as well as the impacts associated from industrial activities, the seasonal variation of temperature, rainfall and other abiotic factors that aid the translocation of PCB pollutants in plants in the area from the environment. Furthermore, the rate of absorption of the contaminants in these plants and their translocation potentials from soil is confirmed to be true [6,25]. The results in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e strongly contradicts the estimated daily intake from studies by Arshad \u003cem\u003eet al\u003c/em\u003e., Esposito \u003cem\u003eet al\u003c/em\u003e., Olatunji and Zhang \u003cem\u003eet al\u003c/em\u003e., [2,9,19,26], whose values fell below the WHO/FAO permissible limits.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eHuman Health Risk Assessment from Edible plants in Koko, Delta State.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRisk Indicator\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCategories\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eCeiba pentandra\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003ePueraria phaseoloides\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eVermonia amygdalina\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cem\u003eMusa sapientum\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003eChromolaena odorata\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eEDI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAdult\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.000003\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.001562\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.000812\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.000152\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.002553\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChildren\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.000005\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.003161\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.001643\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.000307\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.005166\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAdult\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e223.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e116.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e21.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e364.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChildren\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e451.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e234.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e43.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e738.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe chief contributors to these values in the edible plants include shipment of oil and gas consignments, production of paints and lubricants, management of petroleum wastes as well as dumpsite of hazardous wastes and bitumen production. The edible hyper-accumulating plants such as \u003cem\u003eC. odorata\u003c/em\u003e popularly known as Awolowo leaf in Africa and \u003cem\u003eV. amygdalina\u003c/em\u003e also known as bitter leaf, have been discovered beneficial to human health because of their antibacterial and antioxidant properties [5,14]. Yet, the capacity of the studied plants to accumulate contaminants of concern, makes them good genetically-modified materials for phytoremediation while harmful to the ecosystem [26]. Environmental contamination of the persistent organic pollutant (PCBs) is comprehensive and serves as an interesting tool in the study of toxicity effects on humans [1,12].\u003c/p\u003e\u003c/div\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThe study reveals critical levels of PCB contamination in soils and edible plants in Koko, Delta State. The substantial bioaccumulation, especially in \u003cem\u003eP. phaseoloides\u003c/em\u003e and \u003cem\u003eC. odorata\u003c/em\u003e, poses a serious threat to public health. These findings advocate for urgent regulatory action, phytoremediation strategies, and routine environmental monitoring to mitigate long-term exposure in oil-impacted communities. This is a red flag on fruit/vegetable consumption in this region which transcends globally in industrial areas, as this study provides baseline concentrations of PCBs on edible plants in Koko, Delta State, Nigeria. Lower congeners of PCBs are highly adsorbed in soils along the Niger Delta coasts which raises concern over industrial operations in Koko and its environs. Soil biodiversity and public health are at maximal danger and it is needful that anthropogenic sources be minimized to the barest levels to reduce PCB concentrations in the environment.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAll authors have read, understood, and have complied as applicable with the statement on \u0026quot;Ethical responsibilities of Authors\u0026quot; as found in the Instructions for Authors and are aware that with minor exceptions, no changes can be made to authorship once the paper is submitted.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe field experiment was carried out in Warri North, Niger Delta region of Nigeria. The laboratory analysis was done in Ebic Integrated Services Limited (EISL) Laboratory, Rivers state, Nigeria.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support was received during the preparation of this manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAmaka Michael, prepared the manuscript, interpreted the results and wrote the paper, Abraham O. Ekperusi revised the work, Ndu P. Okeke initiated the study, and Anthonia E. Gbuvboro wrote the summary. All authors read and approve the final manuscript.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo ethical approval is required for this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproval for Animal Experiments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproval for Human Experiments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch involving plants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was conducted in accordance with relevant institutional guidelines and regulations.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate/Consent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDual Publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable as the data represented in this study is original.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePermission to use third-party material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated and analyzed during this study are included in this published article (and its supplementary files).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAkhionbare, S. M. O. The Environment \u0026ldquo;Concepts, issues and control of pollution\u0026rdquo;. 2\u003csup\u003end\u003c/sup\u003e ed. Springfield publishers Ltd. Pp.223-256. ISBN:978-978-8500-40-7 (2015).\u003c/li\u003e\n \u003cli\u003eArshad, M., Ahmed, A. M. S., Ahmed, K. S. \u0026amp; Hussain, S. M. Monitoring of level of mean concentration and toxicity equivalence (TEQ) of polychlorinated biphenyls (PCBs) to selected vegetables, beans and grains to Khanewal and multan, Pakistan. \u003cem\u003eSaudi Journal of Biological Sciences\u003c/em\u003e 29(\u003cstrong\u003e4\u003c/strong\u003e):2787-2793. https://doi.org/10.1016/j.sjbs.2022.01.009 (2022).\u003c/li\u003e\n \u003cli\u003eAziza, A. E., Iwegbue, C. M. A., Tesi, G. O., Nwajei, G. E. \u0026amp; Martincigh, B. S. Concentrations, sources and exposure risk of polychlorinated biphenyls in soil profiles of the floodplain of the lower reaches of the River Niger, Nigeria. \u003cem\u003eEnviron. Monit. 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Uptake and translocation of organic pollutants in plants: A review. \u003cem\u003eJournal of Integrative Agriculture\u003c/em\u003e 16(8):1659-1668. https://doi.org/10.1016/S2095-3119(16)61590-3 (2017).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"bio-accumulation, Niger Delta, PCBs, PCBs in soils, PCBs in plants, human health risk","lastPublishedDoi":"10.21203/rs.3.rs-7066469/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7066469/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe distribution of Polychlorinated Biphenyls (PCBs) in Soils and Plants in Koko Town, Delta State, Nigeria, was studied using five soil samples and five edible plants collected from five industrial locations in the study area. Using Soxhlet apparatus and gas chromatography for the extraction of contaminants, and analysis, mean PCB concentrations were found to be significantly higher in plants (20.75mg/kg) than in soils (10.32mg/kg), exceeding the WHO safety thresholds. The sampled plants significantly accumulated PCBs in the following order; \u003cem\u003ePueraria phaseoloides\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;\u003cem\u003eCeiba pentandra\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;\u003cem\u003eChromolaena odorata\u0026thinsp;\u0026gt;\u0026thinsp;Vermonia amygdalina\u0026thinsp;\u0026gt;\u0026thinsp;Musa sapientum\u003c/em\u003e. Estimated daily intake of 0.000007mg/kg for adults and children and a hazard ratio of 1.0 as stipulated by USEPA, indicated substantial human health risks, especially among children. These findings underscore the ecological and toxicological urgency of controlling industrial PCB emissions in oil-producing regions.\u003c/p\u003e","manuscriptTitle":"Distribution and Risk Assessment of Polychlorinated Biphenyls in Soil and Plants in Koko Town, Delta State, Nigeria","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-22 08:25:03","doi":"10.21203/rs.3.rs-7066469/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-26T05:44:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-22T11:25:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"313874907954271869211961024828632532103","date":"2025-08-17T07:37:30+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-16T11:04:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"303339741127736391403807525893211204435","date":"2025-08-10T14:29:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"330472540435739997766684623226568689815","date":"2025-07-29T11:31:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"113765376299529663633489856401640174324","date":"2025-07-27T10:08:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"247354104565165148124249729110942850916","date":"2025-07-15T10:04:12+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-15T06:45:15+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-15T06:35:57+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-15T06:32:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-13T13:11:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-07-13T13:08:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"63cff03f-06f2-416c-9b89-75923d0e6e97","owner":[],"postedDate":"July 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":51676473,"name":"Biological sciences/Ecology"},{"id":51676474,"name":"Earth and environmental sciences/Ecology"},{"id":51676475,"name":"Earth and environmental sciences/Environmental sciences"}],"tags":[],"updatedAt":"2025-12-22T16:11:40+00:00","versionOfRecord":{"articleIdentity":"rs-7066469","link":"https://doi.org/10.1038/s41598-025-33241-x","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-12-18 15:58:40","publishedOnDateReadable":"December 18th, 2025"},"versionCreatedAt":"2025-07-22 08:25:03","video":"","vorDoi":"10.1038/s41598-025-33241-x","vorDoiUrl":"https://doi.org/10.1038/s41598-025-33241-x","workflowStages":[]},"version":"v1","identity":"rs-7066469","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7066469","identity":"rs-7066469","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}