HEAVY METALS

This study assessed the levels of selected heavy metals and polycyclic aromatic hydrocarbons (PAHs) in suya meat sold in Ugbowo, Benin City, to evaluate its safety for consumers. Ugbowo is a busy area with dense traffic and open-air vending that exposes food to contamination from vehicle emissions, dust, and smoke. Two composite suya samples were analyzed—one obtained from roadside vendors along major express routes and the other from residential areas including 19th Street, BDPA, and Edo Street in Ekosodin. The samples were oven-dried, homogenized, digested with nitric acid and hydrogen peroxide, and analyzed for heavy metals using Atomic Absorption Spectrophotometry (AAS). Polycyclic aromatic hydrocarbons (PAHs) were extracted and determined using Gas Chromatography–Mass Spectrometry (GC–MS). The AAS results showed the presence of lead (Pb), cadmium (Cd), copper (Cu), and nickel (Ni), while chromium (Cr) was below detection in both samples. Concentrations (mg/kg) for express road samples and residential sample were Pb (4.348, 5.002), Cr (<0.001, <0.001), Cu (1.635, 0.654), Cd (4.381, 3.988), and Ni (9.578, 5.230), all exceeding WHO/FAO permissible limits, indicating contamination likely from road dust, metal grills, or fuel combustion. GC–MS analysis revealed that all sixteen priority PAHs were below the detection limit (0.000 mg/kg) in both samples, suggesting minimal formation during grilling. Overall, the results indicate that while PAH contamination was negligible, heavy metal levels were significantly high, posing potential health risks to frequent consumers. The study recommends regular monitoring of street-vended foods and improved hygiene and roasting practices among suya vendors in Benin City.

Food processing methods, particularly mechanical grinding, have been identified as potential sources of heavy metal contamination in daily diets. This study assessed the concentrations and health risks of heavy metals introduced into common Nigerian food items (tomato, pepper, melon, beans, groundnut, white and yellow corn, and crayfish) during grinding with various equipment types including blenders, milling machines, hand-crank grinders, mortars, and grinding stones. Heavy metals (Fe, Mn, Zn, Ni, Cd, and Pb) were analyzed using Atomic Absorption Spectrophotometry (AAS), and potential health risks were evaluated using Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) models. Results revealed elevated levels of essential metals such as Fe, Mn, and Zn, with concentrations highest in foods ground with older milling machines and mechanical grinders, reflecting increased leaching due to metallic wear. Toxic metals (Pb and Cd) were mostly below detection limits, indicating minimal immediate toxicity but potential for chronic accumulation. Fe showed the highest EDI (up to 5.35 mg/kg/day in hand-crank grinder samples), while THQ values exceeded 1.0 in several processed beans samples, suggesting possible non-carcinogenic risk upon prolonged exposure. Traditional grinding methods (mortar and pestle) exhibited significantly lower contamination levels compared to mechanical ones. These findings highlight that metal leaching from food processing equipment constitutes a significant but often overlooked route of dietary exposure to heavy metals in Nigeria.

This study assessed the human health risks associated with heavy metals in groundwater from Oluku, Edo State, Nigeria, with a focus on dermal exposure. Groundwater, a primary domestic water source, is vulnerable to contamination by both natural and anthropogenic activities, including industrial discharge, agricultural runoff, and improper waste disposal. Key heavy metals analyzed included zinc (Zn), cadmium (Cd), manganese (Mn), iron (Fe), and Lead (Pb). Fifteen groundwater samples were collected and analyzed using atomic absorption spectrometry (AAS) following standard procedures. Concentrations were compared against World Health Organization (WHO, 2017) and Nigerian Standard for Drinking Water Quality (NSDWQ, 2007) limits, while potential human health risks were estimated using the United States Environmental Protection Agency (USEPA, 2004) Human Health Risk Assessment (HHRA) framework. Results indicated that zinc (Zn) and iron (Fe) were present at relatively higher levels, with mean concentrations of 3.05 mg/L and 1.53 mg/L, respectively, while lead (Pb) and cadmium (Cd) recorded concentrations of 0.604 mg/L and 0.462 mg/L, exceeding WHO and NSDWQ limits. Chronic Daily Intake (CDI) and Hazard Quotient (HQ) analyses revealed that non-carcinogenic risks from Zn, Fe, and Mn were minimal. However, Pb and Cd posed significant health risks, particularly for children, who exhibited higher exposure levels due to lower body weight and greater dermal contact. Carcinogenic risk assessment further indicated that both Pb and Cd exceeded acceptable USEPA limits, with cadmium presenting the highest lifetime cancer risk. The study concluded that Fe and Zn likely originated from natural geogenic sources within the Benin Formation, while Pb and Cd contamination was predominantly anthropogenic, linked to industrial, domestic, and agricultural activities. The uneven spatial distribution of metals highlighted the influence of proximity to pollution sources. These findings underscore the urgent need for continuous groundwater monitoring, effective waste management, and public health interventions to mitigate exposure risks in Oluku, ensuring the safety of groundwater resources for domestic use.

The quality of aquatic environments is an important contributor to good environmental health. This study assessed the ecological risk assessment of heavy metals in sediments from Ossiomo River, Edo State in order to ascertain the status and degree of contamination. Nine sediment samples were collected using an Eckman Grab from Ossiomo River from November 2021 to January 2022. Samples collected were air-dried, crushed and sieved through a 2mm sieve, pre-treated using standard methods before determining the heavy metal concentrations in Atomic Absorption Spectrophotometer according to the method of the Association of Analytical Chemists. The average mean concentration of heavy metals in sediments from Ossiomo river were1137±760.55 for Fe, 6.83±1.24 for Cu, 28.94±11.93 for Zn, 0.14±0.06 for Cd, 5.80±5.27 for Pb, 9.02±3.80 for Mn, 4.30±1.04 mg/kg for Cr respectively while total hydrocarbon content had an average mean value of 826.80±457.27 mg/kg. The result showed that the concentration of heavy metal were in the following decreasing order: Fe>Zn>Mn>Cu> Pb> Cr>Cd. The composition of
computed Enrichment factor (EF) indicated that there is a moderate enrichment for Fe and Zn, a significant enrichment for Fe, Cr, Cd and a very high enrichment for Pb. Geo accumulation index (Igeo)
showed that sediments from Ossiomo River indicates Cu and Mn were practically unpolluted, Cr and Cd were moderately to heavily polluted, Pb was heavily polluted and extremely polluted. The contamination factor showed a moderate contamination exist for Cu and Mn across the sampled stations from Ossiomo River, a very high contamination exist for Cr, Cd, and Pb across the three sample stations. The contamination degree (CD) showed that a very high degree of contamination(CD ≥ 24) exists across all the three sample stations. Pollution load Index (PLI) showed that Ossiomo river is polluted (PLI>1) by metals. Potential ecological risk index (PERI) showed slight pollution degree of Cu, Zn, and Mn, a medium pollution degree of Cr, a strong pollution degree and a very strong pollution degree of Pb while Cd exhibited an extremely strong pollution degree. The risk level or risk degree for Ossiomo River indicated an extremely strong risk degree or level Dacross the sediments across the stretch of Ossiomo River. The potential ecological risk showed that station1and 3 indicates considerable ecological risk (300<RI≤600), while station 2 indicates a very high ecological risk (RI>600). The heavy metals content exhibited a positive and significant correlation. Therefore the pollution by heavy metals in sediments from Ossiomo River should not be ignored.

Heavy metal pollution has become a critical environmental challenge, particularly due to the persistence and toxicity of metals such as copper in aquatic ecosystems. Conventional treatment methods for metal removal, including chemical precipitation, ion exchange, and membrane filtration, are often costly, inefficient at low metal concentrations, and produce secondary waste. In response, biosorption has emerged as an eco-friendly and sustainable alternative. This study investigates the potential of corn cobs, an abundant agricultural by-product, as a low-cost biosorbent for the removal of Cu2+ ions from aqueous solutions. The biosorbent was prepared through collection, washing, drying, crushing, and sieving of corn cobs to obtain uniform particle sizes. A Box-Behnken Design (BBD) under the Response Surface Methodology (RSM) framework was employed to optimize process parameters such as adsorbent dosage, contact time, and metal concentration. Experimental data were fitted to a quadratic model, and statistical analysis through ANOVA revealed that the model was highly significant (F-value = 116.31 , P < 0 .0001) with strong correlation coefficients (R2 = 0.9934, Adjusted R2 = 0.9848, Predicted R2 = 0.9135). Optimization results indicated maximum copper ion removal of 94.73% at the optimal conditions of 5.5g/L adsorbent dosage, 67.5 minutes contact time, and 6 mg/L initial metal concentration. The model validation confirmed close agreement between predicted and experimental results, demonstrating the reliability of the developed model. Thermogravimetric and differential thermal analyses (TGA/DTA) suggested that the corn cob biosorbent possessed good thermal stability, which supports its suitability for adsorption applications. The study concludes that corn cobs are an effective, sustainable, and economical biosorbent for copper ion removal from wastewater. It further recommends their potential application in small- to medium-scale industrial effluent treatment systems. Future research should focus on kinetic and isotherm modeling, column adsorption studies, and biosorbent modification to enhance adsorption efficiency and extend applicability to other heavy metals.

Research has been ongoing on many plant materials, especially those discarded as waste, to exploit their nutritional and antinutritional properties. Generally, plant parts (seeds, leaves, bark, fruits, stems) contain bioactive agents with medicinal properties but require proper assessment. Avocado (P. americana) seeds are often discarded after taking the pulp of the fruit. Until recent times, Researchers have identified a wealth of therapeutic compounds in the husk of avocado seeds which are normally discarded. The present study was aimed at determining the level of anti-nutrients and possibly heavy metals in the seed of Avocado. The seeds were removed from the pulp, washed, dried, cut into smaller pieces and allow to air dry completely and then pulverised. The seed powder of P. americana was analysed to determine its mineral contents and some antinutritional properties (oxalate and phytate). The quantitative analysis of these parameters showed that the anti-nutritive components are Phytate (1.07%) and oxalate (6.16%) respectively. The mineral analysis revealed zinc (3.415 mg/kg ±0.145), Lead (0.035 mg/kg ±0.005), iron (2.775 mg/kg ± 0.105), Nickel (0.115 mg/kg ±0.005), Copper(0.265 mg/kg ±0.015), Cobalt (0.14 mg/kg ±0.01), Chromium (0.08 mg/kg ±0) respectively. This study, therefore revealed that P. americana seeds have a low level of oxalate and phytate contents while there were low levels of some heavy metals as seen in the result. In conclusion, the seeds of P.
Americana were found to be a beneficial potential therapeutic agent.

This study investigates the contents of some heavy metals (Cadmium (Cd) and Chromium (Cr)) concentrations in the soils of a dumpsite located within Egor Local Government Area in Benin City. Soil samples were randomly obtained from different locations within the dumpsite while the control soils were obtained from the Faculty of Agriculture University of Benin. A total of 18 samples were collected, with nine from the dumpsite and nine from the
control site at three different depths (0-15cm, 15-30cm, and 30-45cm). The experiment was thereafter laid out in a Completely Randomized Design (CRD). Results from the investigations shows that the dumpsite soils exhibited higher organic matter content (47.73, 38.00 and 31.03 gkg -1) that ranged from the topsoil to the subsoil while the control had 13.79, 10.57 and 10.51 gkg -1 respectively. The dumpsite also recorded reduced (5.04 – 6.13) acidity, which resulted in increased nutrient (N, P, K, Ca and Mg) release so was the cadmium (Cd) concentrations significantly elevated in the dumpsite soils, ranging from 5.14 - 8.18 mgkg -1 , compared with the content in the control (0.31 - 0.66 mgkg -1 .). The Cd (19.93 – 36.78 mgkg -1) and Cr (5.14 – 8.18 mgkg -1) contents in the dumpsite were highly above the permissible limit defined by World Health Organization. These findings underscore the potential impact of waste deposition, emphasizing the need for proper waste management practices to mitigate heavy metal contamination from getting into the food chain and as such it is recommended that the dumpsite investigated should not be used in the production of food crops intended for human consumption.

Heavy metal contamination of freshwater bodies poses a significant environmental and public health concern, particularly in urban regions with increasing anthropogenic activities. This study aimed to evaluate the concentrations and health risks of selected heavy metals in the Ogba River, Benin City, Nigeria. Water samples were collected across three locations (upstream, midstream, and downstream) over three months to assess both spatial and temporal variations. The samples were analyzed for copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), manganese (Mn), and cadmium (Cd) using an atomic absorption spectrophotometer. The data were analysed using SPSS version 22, and descriptive statistics and one-way ANOVA were employed to assess variations, with p < 0.05 considered statistically significant. Results revealed that Ogba River water showed elevated levels of Cr, Ni, Pb, Mn, and Cd, often exceeding WHO and, in some cases, NESREA permissible limits, while Cu remained within safe limits. Children had higher Chronic Daily Intake (CDI) values than adults. Hazard Quotient (HQ) indicated low risk for Cu, Ni, and Mn, but potential non-carcinogenic risk from Cr, Cd, and Pb. Combined Hazard Index (HI) exceeded 1 at all stations, with children more vulnerable. Incremental Lifetime Cancer Risk (ILCR) for Cr, Cd, and Pb surpassed USEPA limits, with Cr posing the highest cancer risk. In conclusion, Ogba River is contaminated with heavy metals exceeding safe limits and posing health risks, particularly to children. Immediate monitoring and pollution control are needed to protect human health and the river ecosystem

This study assessed the physicochemical parameters and heavy metals content in sediments from Orhiomwon River, Edo state, Nigeria. A total of nine (9) sediment samples were collected from the sampling stations from May, 2025 to July, 2025. Physicochemical parameters of sediments were analysed following standard laboratory procedures while selected heavy metals were determined following the method of the association of analytical chemistry. The average mean concentration of physicochemical and heavy metals parameters of sediments were 5.03±0.20 (pH), 43.67±10.44 (EC), 1212.61±165.52 (Ca), 287.33±93.92
(Mg), 297.91±81.39 (K), 161.62±32.71 (Na), 0.05±0.01 (N), 0.51±0.16 (TOC), 92.18±2.39 (sand), 5.94±2.38 (clay), 1.88±0.03 (silt), 2366.74±817.55 (Fe), 18.92±4.58 (Cu), 69.20±19.63 (Zn), 0.04±0.06 (Cd), 6.66±1.48 (Pb), 33.55±23.38 (Mn), 1.49±0.47 (Cr) and
27.24±10.41 (THC) respectively. Heavy metal concentrations followed the order: sand, silt and cadmium showed no significant differences (p > 0.05) across the three stations. On the other hand, pH, electrical conductivity (EC), calcium, magnesium, total organic carbon (TOC), clay, manganese, chromium, and total hydrocarbon content (THC) exhibited significant differences (p < 0.05) while potassium, nitrogen, sodium, iron, copper, zinc and lead showed a high significant difference (p<0.01) among the sediment samples from the different stations of Orhiomwon River. Fe>Zn>Pb>Cu>Mn>Cr>Cd. The results obtained in
this study showed that natural geochemical processes remained the dominant influence on Orhionmwon River sediments as signs of human activity especially from anthropogenic activities are evident.

This study was conducted in the Greenhouse of the Department of Soil Science and Land Management, Faculty of Agriculture, University of Benin, Benin City, to determine the heavy metal concentration of Celosia argentae raised on soils from dumpsites in Benin City, Edo State. Soil samples were collected from dumpsites from three different land uses around Ugbowo Campus of University of Benin City. The soils from the dumpsites were filled into plastic buckets and used to raise Celosia argentae. The experiment was laid out in a Completely Randomized Design (CRD) with three treatments and replicated three times. Soil and plant sample were collected and taken to the laboratory for analysis and standard
procedures were used to analyze the samples. Data obtained were subjected to analysis of variance (ANOVA) and Duncan’s New Multiple Range Test was used to separate the means at 5% level of significance. The parameters measured include: pH, Total organic carbon, Total nitrogen, Available phosphorus, Sand, Silt, Clay, Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Zinc, Lead, Chromium and Cadmium for the dumpsite soils, while the micro nutrients (Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Zinc) and heavy metals (Lead, Chromium and Cadmium) for the plant samples. The results show that the pH of the soils from the dumpsites were moderately acidic (5.66 – 5.92). The soils belong to the textural class sand