J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 Journal of the Nigerian Society of Physical Sciences Characterization and Evaluation of Human Health Risk of Heavy Metals in Tin Mine Tailings in Selected Area of Plateau State, Nigeria D. D. Bwedea, R. A. Wuanab, G. O. Egahc,∗, A. U. Itodob, E. Ogahd, E. A. Yerimac, A. I. Ibrahimc aDepartment of Basic Sciences, Plateau State College of Health Technology Zawan, Nigeria bDepartment of Chemistry Federal University of Agriculture Makurdi, Benue State, Nigeria cDepartment of Chemical Sciences, Federal University Wukari, Taraba State, Nigeria dDepartment of Chemistry University of Jos, Jos, Plateau State, Nigeria Abstract Tin mining tailings are unprocessed waste materials that overlie an ore which are displaced during mining activities. This research work is aimed at characterizing and evaluating the human health risk of heavy metals in tin mine tailings in Zabot (S3) and Tafan (S4) districts in Barkin Ladi Local Government Area of Plateau State, Nigeria. The samples were characterized using EDX-XRF and SEM. The concentrations of seven heavy metals (Pb, Cr, As, Ni, Cd, Cu and Zn) were determined in S3 and S4. The results showed that Cr, Ni, Cd, Cu and Zn were within the USEPA permissible limits, except for Pb and As with range of (270-300) mg/kg and (40-70) mg/kg respectively for both mining and control sites of S3 and S4. The SEM results revealed small particles size with fine porous structure, and rough areas with varying sizes and pores distributed over the surface for S3 and S4 respectively. Results of the risk assessment showed that the hazard quotient HQ and HI values were greater than 1 indicating high risk. The Carcinogenic and non-carcinogenic risks associated with Pb, Zn, Cd, Cr, Ni and As were evaluated for S3 and S4 for the three exposure pathway and it was found that the mining sites pose more risk than the control and the children were more exposed than the adults. The carcinogenicity of these samples were due to the high hazard quotient for ingestion and dermal exposure pathway. The Rtotal results for As, Cr, Pb and Ni for mining site S3 were found to be (1.39 × 102, 2.02 × 10−7, 3.30 × 103 and 8.17 × 10−8), and control site (3.42 × 103, 2.64 × 10−5, 38.30 × 101, 6.90 × 10−8) for As, Cr, Pb and Ni respectively. From the Rtotal results As and Pb were more than the acceptable threshold, while Cr and Ni were below the threshold of 1×10−4. For the mining site S4, the Rtotal were found to be (5.70×102, 1.82×10−7, 3.63×104 and 9.64×10−9), and the control (1.16×103, 1.71×10−7, 31.1×102 and 1.51×10−8) for As, Cr, Pb and Ni respectively. From the results of the mining and control sites, As and Pb Rtotal were higher than the acceptable threshold, while Cr and Ni were below the threshold of 1 × 10−4. DOI:10.46481/jnsps.2021.262 Keywords: Tailings, Heavy metals, Hazard Index, Carcinogenic Risk and Hazard Quotient Article History : Received: 18 June 2021 Received in revised form: 16 September 2021 Accepted for publication: 17 September 2021 Published: 29 November 2021 c©2021 Journal of the Nigerian Society of Physical Sciences. All rights reserved. Communicated by: S. J. Adebiyi ∗Corresponding author tel. no: +2347061097995 Email address: egah.godwin@yahoo.com (G. O. Egah ) 1. Introduction Tin mining tailings are wastes fractions of an ore or min- eral body which are discarded during mining operations without being processed. Tin tailings contains both magnetic minerals 406 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 407 (iron ore, columbite) and non-magnetic minerals (cassiterite, monozite, zircon sand in large quantity and silica) [1]. They are used in preparation of fertilizer, animal feeds, refractory prod- ucts, for building roads and backfilling of tailing storage facili- ties [2]. In the 1960s, Nigeria was regarded as one of the world’s leading tin producing country, but production later decreased towards the end of the twentieth century. However, mining ac- tivities are still going on in these areas. Apart from tin which is the primary target, tin mining generates tin tailings, which are by-product of the ore. The amount of tailings produced ranged from 90-98 % for copper ores and 20-50 % for other minerals [3]. Some of the heavy metals found in contaminated tailings are Pb, Cr, As, Zn, Cd, Cu, Ni and Hg [4, 5, 6]. Heavy metal contamination and their human health threats are some of the serious environmental problems limiting mining activities [7, 8]. With the development of mining, smelting and other indus- trial activities, heavy metals are increasingly being found in the environment which can pose severe threats to humans and the environment. Pollution by heavy metals such as lead (Pb), chromium (Cr), arsenic (As), nickel (Ni), cadmium (Cd), cop- per (Cu) and zinc (Zn), affects the quality of the ambient air, soil and water bodies which in turn threatens the life of both animals and humans through the food chain [2]. During mining activities huge waste tailing ponds are cre- ated which have a high environmental impact on the surround- ing ecosystems and populations when used [9, 10]. In order to evaluate the risk posed by tin mine tailings activities to human health, there is need to assess the level of heavy metal pollution in these sites and the rate at which they affects human life. This is based on preliminary studies on waste properties, heavy met- als concentration and their relation to the environment as they affect the individuals who participated in these tailings activi- ties and the community [11]. Human health risk assessment involves the evaluation of possible human health effect in the contaminated environmental media [12]. The health effect of contaminants on humans de- pends on the level of exposure, nature of the contaminants and vulnerability of the individual affected [13]. Health effects may include risk of cancer, hypertension, acute foetus neurological disorders, organ dysfunction, respiratory difficulties, physical and mental disorder, reduced life expectancy and weakening of the body’s immune system [12]. Therefore, this research is aimed at characterizing and eval- uating the human health risk of heavy metals in tin mine tail- ings in Zabot and Tafan district both represented by S3 and S4 respectively in Barkin Ladi Local Government Area, Plateau State, Nigeria. 2. RESEARCH METHODOLOGY 2.1. Sample Location and Description This research work was carried out in Zabot (S3) and Tafan (S4) district of Barkin Ladi Local Government Area of Plateau State, Nigeria. It is located between latitude 9051′30′′N and longitude 8048′00′′E. The state is located in the middle belt of Nigeria, with an area of 30.91 km (11936 square mile). The state has a population of about three million people in estimate. The name Plateau State was given because of its topography with wonderful rock formations. The height of the mountains ranges from 1,200 to 1,829 meters above sea level. Mining and subsistence farming are the major occupation of its residents. The sampling locations and points are as shown in Figure 1, us- ing the geographical positioning system (GPS) to locate Zabot (S3) and Tafan (S4). Figure 1. GPS Map Showing the Sites of Sample Collection. 2.2. Sampling collection and preparation The random sampling technique was applied for sample collection with little modification. Two samples of 50 g each were taken from mining sites in Zabot (S3) and Tafan (S4) in Barkin Ladi Local Government Area of Plateau State, with their respective control. The tin mine tailings and soil samples were washed, dried and pulverized into the required particle sizes of 2 mm. Pre-treatments which does not alter the chemical com- position of the analytes were done to obtain the original con- centration of the analyte found in the sample. 2.3. Determination soil pH and Temperature 1.0 g of soil sample from both mining and control sites were mixed with 100 cm3 of deionized water in 250 cm3 conical flask and stirred using a magnetic stirrer for 10 minutes. The temper- ature and pH were determined using Hanna portable pH meter (model HI8043) and thermometer respectively. The readings were taken in triplicates and the average recorded accordingly. 407 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 408 2.4. Sample Characterization 2.4.1. Elemental analysis The concentrations of the various heavy metals contained in the samples were determined using Energy dispersive X-ray fluorescence spectrometer EDX-XRF (MiniPAL4). The XRF analysis was done directly on solid powdered specimen for ac- curate results with no risk of contamination. Sample prepara- tion involves milling of the sample to less than 75 µm in frac- tion. Retsch RS 200 vibratory disk milling machine was used at 1500 min−1 motor speed for 5 minutes. The milled sample was collected in XRF cup and placed in the XRF spectrometer and analyzed for chemical composition. 2.4.2. Determination of Surface Morphology The surface morphology of the tailings was determined us- ing scanning electron microscope (SEM-MVE016477830). The sputter coater was operated in an argon atmosphere using a cur- rent of 6 mA for 3 minutes. 2.5. Human Health Risk Assessment Parameters The carcinogenic and non-carcinogenic risks were evalu- ated using the human health risk assessment model for dermal contact, ingestion and inhalation exposure pathways [13]. The health risk assessment is centered on the exposure factors and guidelines handbook of United States Environmental Protec- tion Agency (USEPA) [14]. The average daily dose (ADD) via inhalation (ADDinh), ingestion (ADDing) and dermal con- tact (ADDderm) for both children and adults were evaluated us- ing equations (1) - (3) as adopted from Qing et al., [13]. Ingestion dose Ding−s = CS × IngR × EF × ED × CF BW × AT (1) Inhalation dose (Dinh−s) = CS × InhR × EF × ED BW × AT × PEF (2) Dermal dose (Dder−s) = CS × S A × S L × EF × ED × CF BW × AT ,(3) where CS is the concentration of the analyte in the tailing from the exposure point (mg/kg), IngR - tailing ingestion rate for the receptor (mg/d), InhR - soil inhalation rate for the recep- tor (m3/d), EF - exposure frequency (days/year), ED - exposure duration (years), PEF - soil-to-air particulate emission factor (m3/kg), SA - skin surface area available for exposure (cm2), SL - soil-to-skin adherence factor (mg/cm2/event), BW - time- averaged body weight (kg), AT - average time of non-carcinogenic and carcinogenic risks (days) and ABS - dermal absorption fac- tor (dimensionless). The hazard quotient, hazard index and total cancer risk were evaluated using equations (4) – (6) as adopted from Man et al., [15]. The Hazard Quotient is given as: HQ = D RfD , (4) where D = Dose (ingestion, inhalation or dermal), RfD = Ref- erence dose. The Hazard index HI is given as: HI = HQing + HQinh + HQderns (5) Total cancer risk (RT) is given as: RT = D × S F, (6) where D = Dose, SF=Slope factor. Risk characterization was considered separately for carcino- genic and non-carcinogenic effects [16, 17]. Health risks were obtained by comparing the calculated HQ, HI and Rtotal values with recommended maximum values shown on Table 1. 3. RESULTS AND DISCUSSION 3.1. Determination soil pH and Temperature The results of the pH and Temperature obtained from the study area are presented in Table 2. The pH and temperature results of the samples are presented in Table 2. The pH obtained from the mining and the control sites were (5.23, 5.11) and (7.48, 7.21) for Zabot and Tafan re- spectively. The pH results showed that the two mining sites were slightly acidic, while the control sites were slightly alka- line. The soil temperatures were within the range of 29 to 30◦C, which are suitable for plants growth [19]. 4. Scanning Electron Microscopy of Tin Mines Tailings The results of scanning electron microscopy (SEM) for tin mine tailing site S3 and S4 are as shown in Plates 1 (Figure 2) and 2 (Figure 3), respectively. Figure 2. Plate 1: The Scanning Electron Microscope Micrograph (SEM) of Zabot S3. Result of S3 on Plate 1, showed homogenous small size par- ticles with fine porous structure. While results on plate 2 (S4), showed a micrograph with rough area having different irregu- lar shapes of varying sizes and pores distributed over the sur- face. The more the number of pores the better the soil aeration [20, 21]. From the two results (Plates 1 and 2), it can be seen that the S4 has more pores than the S3. 408 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 409 Table 1. USEPA Reference Doses for Non carcinogens and Slope Factor for Carcinogens Source: [18] Rf Ding Rf D/mg.kg−1.d−1 Rf Ddermal SFing SF/kg.d,mg−1 SFinh SFdermal As 3.00E-04 1.23E-04 1.50 E+00 1.51 E+00 3.66 E+00 Cr 3.00E-03 2.86 E-05 6.00 E-05 4.2 E+01 Cu 4.00 E-02 4.02 E-02 1.20 E-02 Pb 1.40 E-03 3.52 E-03 5.25 E-05 8.50 E-03 Ni 2.00 E-02 2.06 E-02 5.40 E-03 8.40 E-1 Zn 3.00 E-01 3.00 E-01 6.00 E-02 Hg 3.00 E-04 8.57 E-05 3.00 E-05 RfD=Reference dose and SF=Slope factor Table 2. pH and Temperature of Tin mine Tailings and Control Soil Sample pH Temperature ◦C Tin Mine Site S3 5.23 30 Control S3 7.48 29 Tin Mine Site S4 5.11 29 Control S4 7.21 30 Figure 3. Plate 2: The Scanning Electron Microscope Micrograph (SEM) of Tafan (S4). 4.1. Heavy Metal Concentration in Tin Mine Tailings and Con- trol Sites The heavy metals concentrations of Pb, Cr, As, Zn, Cd, Ni and Cu in Tin mine tailings and control sites are presented in Table 3. The results on Table 3, belong to the heavy metals concen- trations of the tin mine tailings and the control site in Zabot of Barkin Ladi Local Government Area. These were determined using Energy dispersive X-ray fluorescence spectrometer EDX- XRF (MiniPAL4). The results showed that the heavy metals concentrations were within the USEPA permissible limits of the soil, except for Pb and As with range of (270-300) mg/kg and (40-70) mg/kg respectively, which are higher than the USEPA permissible limits of 80 and 0.07 mg/kg for both Pb and As re- spectively [22]. The high concentration of As and Pb may be traceable to the tin mining activities, farming activities such as application of agricultural chemicals and atmospheric deposi- tions by transport mechanism on the site [19]. This agrees with the work reported by Bwede et al., [3]. The extreme concentra- tion of As and Pb may be via bioaccumulation in plant which then enters the food chain when these plants are consumed [22]. Also, the concentrations of the heavy metals from the mining sites are significantly higher than the control sites which may be due to anthropogenic activities within the environment [23]. Zn found in the area may be as a result of its natural abundance in the parent material [24]. This agrees with the work reported by Banerjee [25], that iron oxides adsorb some quantities of Zn in the lattice structure. 4.2. Human Health Risk Assessment of the Site The human health risk assessment results for the non-carcinogenic and carcinogenic are shown in Tables 4 - 7 for children and adult respectively. For the non-carcinogenic risk (Tables 4 and 5), if the hazard quotient (HQ) and hazard index (HI) are greater than 1, then adverse health effects may occur [15, 16]. Also for carcinogenic risk level (Table 6-7), total cancer risk (Rtotal) val- ues greater 1 × 10−4 represents elevated risks, Rtotal less than 1 × 10−6 does not pose any significant health risk, and Rtotal values between 1 × 10−4 and 1 × 10−3 are generally considered acceptable [26, 17]. 4.2.1. Non-carcinogenic risk assessment (NCR) for S3 and S4 The results on Tables 4 - 5, are the non-carcinogenic risk assessment of (Pb, Zn, Cd, Cr, Ni and As) for S3 and S4. The three human exposure routes considered in this study were in- gestion, inhalation and dermal exposure. For mining site S3, values of HQ for ingestion and dermal for children are all greater than 1, except for inhalation which are all less than 1. Accord- ing to Huang et al., [16], HQ and HI greater than 1 are indi- cation of high cancer exposure risk, while values less than 1 indicates that there are no significant effects. Therefore, since the ingestion and dermal values are greater than 1, they have high risk exposure. Similar results were observed for adults, except for Cr (1.69 × 10−1) which is less than 1 for ingestion. For the control (S3), the results of children for the three ex- posure pathways are greater than 1, except for Cr, Pb and Ni with values (7.05 × 10−5, 1.32 × 10−4 and 0.60 × 10−6), respec- tively which are less than 1 indicating no risk [16]. Similar results were observed for adults, except for Ni (2.10 × 10−6) 409 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 410 Table 3. Heavy Metals Concentration in Tin Mine Tailings and Control Samples in Zabot, and Tafan in Barkin Ladi Local Government Area of Plateau State, Nigeria in (mg/kg) Heavy metal Tin mine Tailing Control USEPA (2009) S3 S4 S3 S4 Pb 300 1,900 280 270 80 Cr 900 1,000 170 1,600 100,000 As 40 60 70 60 0.07 Zn ND 200 BDL 180 23,000 Cd ND ND BDL BDL 1.7 Ni 210 50 70 79 1,600 Cu ND ND BDL BDL 3,000 BDL: Below detection limits Table 4. Human Health Risk Assessment of Non-Carcinogenic Hazard of Heavy Metals for Zabot (S3) Non Carcinogenic hazards S3 Group Heavy Metal HQing HQinh HQdern-s HI Tin mine tailing from mine site Children As 2.65×106 NC 2.19×105 2.87×106 Cr 9.43×106 8.78×10−5 4.84×105 9.91×106 Pb 1.9×107 1.67×10−4 5.83×105 1.95×107 Ni 3.43×104 0.74×10−6 0.15×103 3.46×104 Zn 7.73×104 2.33×10−7 4.43 7.73×103 Sum 3.12×107 2.56×10−4 1.29×106 3.23×107 Adult As 4.03×105 NC 4.46×104 4.48×105 Cr 1.69×10−1 4.44×10−3 1.21×102 1.27×102 Pb 2.91×106 0.86×10−4 1.17×105 3.02×106 Ni 0.53×104 3.85×10−7 0.03×103 5.33×103 Zn 1.18×103 1.06×10−7 8.87 1.19×103 Sum 3.35×106 4.53×10−3 1.62×105 3.48×106 Soil from agricultural farmland around mine site Children As 2.03×106 NC 1.79×105 2.21×106 Cr 7.86×106 7.05×10−5 4.02×104 7.72×106 Pb 1.50×107 1.32×10−4 4.60×105 1.54×107 Ni 2.76×104 0.60×10−6 0.12×103 2.77×104 Zn 7.33×103 1.96×106 4.22×101 7.37×103 Sum 2.49×107 1.96×106 6.79×105 2.54×107 Adult As 3.37×105 NC 3.71×104 3.71×104 Cr 0.68×103 5.56×103 0.51×105 5.72×104 Pb 2.29×106 0.66×104 0.92×105 2.88×106 Ni 4.22×103 2.10×10−6 0.02×103 4.24×103 Zn 1.12×104 1.43×10−7 8.43×10−3 1.12×104 Sum 2.64×106 1.22×104 1.80×105 2.99×106 NC: Not Calculated 410 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 411 Table 5. Human Risk Assessment of Non-carcinogenic Hazard of Heavy Metals in Tafan (S4) Non Carcinogenic hazards S4 Group Heavy Metal HQing HQinh HQdern−s HI Tin mine tailing from mine site Soil from agricultural farm- land around mine site Children As 1.80×10−8 2.70×101 2.19×104 2.87×106 Cr 9.43×106 2.54×101 4.84×105 9.91×106 Pb 1.9×107 1.67×104 5.83×105 1.95×107 Ni 3.45×104 0.74×10−6 0.15×103 3.46×104 Zn 7.73×104 2.33×107 4.43×101 7.73×103 Sum 2.85×107 2.33×107 1.09×10−6 3.23×107 Adult As 4.03×105 5.48×107 4.46×104 4.48×105 Cr 5.63×101 7.24×103 1.21×102 1.27×102 Pb 2.91×106 0.86×10−6 1.17×105 3.02×106 Ni 0.53×104 3.85×107 0.03×103 5.33×103 Zn 1.18×103 1.06×107 8.87×105 1.19×103 Sum 3.32×106 1.45×108 1.62×105 3.47×106 Children As 2.03×106 2.20×101 1.79×105 2.21×106 Cr 7.86×106 2.11 4.02×104 7.72×106 Pb 1.50×102 4.64×107 4.60×105 1.54×107 Ni 5.51×102 2.76×104 0.12×103 2.77×104 Zn 7.33×103 1.96×107 4.22×101 7.37×103 Sum 2.49×107 6.60×107 6.79×105 2.32×107 Adult As 3.37×105 NC 3.71×104 3.74×105 Cr 2.03×103 5.56×103 0.51×105 5.72×104 Pb 2.29×106 0.66×10−4 0.92×105 2.38×106 Ni 4.22×103 2.10×106 0.02×103 4.24×103 Zn 1.12×104 1.43×10−7 8.43×10−3 1.12×104 Sum 2.65×106 2.11×106 1.80×105 2.83×106 NC: Not Calculated Table 6. Individual Carcinogenic Risk at the site Zabot (S3) Group Heavy Metal Carcinogenic Risk S3 Rtotal Ring−s Rinh−s Rdern−s Tin mine tailings from mine site As 1.17 × 102 1.14 × 10−8 22.18 1.39 × 102 Cr NC 1.64 × 10−7 NC 2.02 × 10−7 Pb 3.30×103 NC NC 3.30 × 103 Ni NC 8.17 × 10−8 NC 8.17 × 10−8 Sum 3.41 × 103 2.57 × 10−3 22.18 16.41 × 106 Soil from agricultural farmland around mine site As 7.61×102 2.12×10-8 1.60×101 3.42×103 Cr NC 2.64×10−5 NC 2.64×10−5 Pb 2.16 ×101 NC 1.67×101 38.30×101 Ni NC 6.90×10−8 NC 6.90×10−8 Sum 78.26×102 2.64×10−5 32.70×101 3.80×109 NC: Not Calculated 411 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 412 Table 7. Individual Carcinogenic Risk at the site Zabot (S3) Group Heavy Metal Carcinogenic Risk S3 Rtotal Ring−s Rinh−s Rdern−s Tin mine tailings from mine site As 4.55×102 4.16×10−8 115.14 5.70×102 Cr NC 1.82×10−7 NC 1.82×10−7 Pb 3.63×104 NC NC 3.63×104 Ni NC 9.64×10−9 NC 9.64×10−9 Sum 36.76×103 2.33×10−4 115.14 9.64×109 Soil from agricultural farmland around mine site As 1.14×103 3.46×10−8 2.4×101 1.16×103 Cr 1.71×10−7 NC NC 1.71×10−7 Pb 2.05×102 NC 106.11 31.1×102 Ni NC 1.51×10−8 NC 1.51×10-8 Sum 1.34×103 4.97×10−2 130.11×102 4.27×103 NC: Not Calculated and Zn (1.43 × 10−7) that are less than 1 and pose no risk [16]. Also, the HI values were all greater than 1, indicating signifi- cant effects. The summation of HQ for ingestion in the mining and control sites are (3.12×107 and 3.35×106), and (2.49×107 and 2.64 × 106) for children and adults respectively. From the results, it is observed that the mining site poses higher risk than the control site, and the children are at higher risk than the adults due to their high values [27]. Similar results were reported by Ngole-Jeme and Fantke [28] for, studies on eco- logical and human health risks associated with abandoned gold mine tailings contaminated soil. The non-carcinogenic risk (NCR) results for Tafan (S4) are presented in Table 5. For mining site, the HQ values for chil- dren were found to be greater than 1, except for As and Ni with values (1.80×10−8 and 0.74×10−6) via ingestion and inhalation respectively. According to Man et al., [15], HQ greater than 1 is an indication of high risk exposure. For the adults, the HQ were found to be greater than 1, except for Pb with value 0.86×10−6 which is less than 1 indicating significant and no significant ef- fect respectively [28]. For the control site (S4) results for children (Table 5), it was observed that both the HQ and HI values were all greater than 1 representing significant effects [16]. The adults result for As, Cr, Pb, Ni and Zn also showed that HQ and HI values were all greater than 1, except for Zn which has values of 1.43 × 10−7 and 8.43×10−3 for inhalation and dermal less than 1, indicating cancer and non-cancer risk respectively [15]. The summation of HQ for ingestion in the mining and control sites are (2.85×107 and 3.32×106), and (2.49×107 and 2.65×106) for children and adults respectively. In terms of population group for NCRs, it is observed that the mining site pose more risk than the control site, and the children are at higher risk than the adults due to their high values [28]. From the results for the three different exposure pathways of metals for children and adults, the con- tribution of HQ is in the order of ingestion greater than dermal and dermal greater than inhalation for As, Cr, Pb, Ni and Zn in the studied mining and control areas for S4. 4.2.2. Carcinogenic Risk Assessment for S3 and S4 The Carcinogenic risks associated with As, Cr, Pb and Ni were evaluated as presented in Table 6. From the S3 results, the Rtotal for mining site were found to be (1.39 × 102, 2.02 × 10−7, 3.30×103 and 8.17×10−8), and control site (3.42×103, 2.64× 10−5, 38.30 × 101, 6.90 × 10−8) for As, Cr, Pb and Ni respec- tively. For carcinogenic risk (Table 6), total cancer risk (Rtotal) values greater than 1×10−4 represents elevated risks, Rtotal less than 1 × 10−6 represents no significant health risk, and Rtotal values between 1 × 10−4 and 1 × 10−3 are generally considered acceptable [26, 17]. From the mining and control results, it was observed that the values of the Rtotal for As and Pb were more than the acceptable threshold, while Cr and Ni were be- low the threshold representing elevated risks and no significant health risk respectively [17]. Similar results were observed by Narsimha and Haike [26] for, studies on distribution, contam- ination, and health risk assessment of heavy metals in surface soils from northern Telangana, India. From results of the mining site S4 (Table 7), the Rtotal were found to be (5.70×102, 1.82×10−7, 3.63×104 and 9.64×10−9), and the control were found to be (1.16 × 103, 1.7110−7, 31.1 × 102 and 1.51 × 10−8) for As, Cr, Pb and Ni, respectively. From the results of the mining and control sites, it is observed that the values for As and Pb Rtotal were higher than the acceptable threshold, while Cr and Ni were below the threshold. These re- sults showed that As and Pb pose elevated risks, while Cr and Ni does not pose any significant health risk [26, 17]. Further- more, values from the mining site indicate more pollution than the control. 5. Conclusion The results of the analysis of this research work showed that both the mining and control sites in Zabot and Tafan in Barkin Ladi L.G.A and environs contains certain concentra- tion of heavy metals (Pb, Ni, Zn, Cr, Cd, As and Cu) in dif- ferent fractions. The surface morphology of the tin mine tail- ings through the use of scanning electron microscopy (SEM) 412 Bwede et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 406–413 413 technique revealed homogenous sized particles with fine porous structure, and rough area having different irregular shapes of varying sizes and pores distributed over the surface for both S3 and S4 respectively. From the hazard quotient (HQ) and human health risk derived from carcinogenic and non-carcinogenic haz- ards for adults and children, it is observed that the mining site pose more risk than the control site, and children are at higher risk than the adults due to their high values. From the results for the three different exposure pathways of metals for children and adults, the contributions of HQ are in the order of ingestion > dermal > inhalation for As, Cr, Pb, Ni and Zn in the studied mining and control areas for S4. Acknowledgements We wish to thank those who work on the abandoned open tin mine tailings site for giving us permission to collect samples for this research. We wish to acknowledge the effort of Godwin Mafuyai and Kelvin Guyit of the department of Natural Sci- ences, University of Jos, Nigeria for their technical assistance in the course of this research work. References [1] V. Aigbodion, A. Abdulrasheed, S. Olajide, J. Agunsoye & I. 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