RESEARCH ARTICLE Zita Naangmenyele, Somandla Ncube, Felix J. Akpabey, Simiso Dube and Mathew M. Nindi 111 S. Afr. J. Chem., 2021, 75, 111–116 https://journals.co.za/content/journal/chem/ *To whom correspondence should be addressed Email: ncubes@unisa.ac.za ISSN 1996-840X Online / South African Chemical Institute / http://saci.co.za/journal © The Author(s) Published under a Creative Commons Attribution 4.0 International Licence (CC BY 4.0) https://doi.org/10.17159/0379-4350/2021/v75a13 Bioaccumulation and Human Risk Assessment of Heavy Metals in Oreochromis niloticus and Clarias gariepinus Fish Species from the Golinga Reservoir, Ghana Zita Naangmenyele a , Somandla Ncube b* , Felix J. Akpabey a , Simiso Dube b and Mathew M. Nindi b a Council for Scientifc and Industrial Research-Water Research Institute, Tamale, NR, Ghana b Chemistry Department, The Science Campus, University of South Africa, Pretoria, South Africa Received 25 September 2020 , revised 24 December 2020, accepted 25 December 2020 ABSTRACT The Nile tilapia (Oreochromis niloticus) and African catfsh (Clarias gariepinus) from the Golinga reservoir in Northern Ghana are consumed as an alternative source of protein. In the current study, levels of selected metals (As, Cd, Fe, Co, Cr, Cu, Mn, Mo, Ni and Pb) in the two fsh species and the fsh condition were determined, and potential human health effects assessed. The metal concentrations in the edible fsh muscles ranged from 0.16 mg kg −1 (Mn) to 101 mg kg −1 (Pb). The weight-length relationships showed that both fsh were growing isometrically, and bioaccumulation of metals from the reservoir was considered insignifcant with bioconcentration factors below 100 except for Mn, whose value was 161 in the gills of Oreochromis niloticus. The health risk assessment showed that Pb, Cd and As had Target Hazard Quotient values above 1 for both fsh species, with that of As being as high as 19.6 for Oreochromis niloticus. The target cancer risk values for As, Cd, Cr and Pb were above the non-risk threshold of ≤10 −6, indicating the risk of cancer developing over the years due to fsh consumption. The metal concentration in the fsh in the reservoir should therefore be constantly monitored and potential health risks associated with frequent consumption of the fsh assessed. KEYWORDS fsh; health risk assessment; Nile tilapia; Target Hazard Quotient; trace metals 1. Introduction The Golinga reservoir has been a source of socio-economic survival for local communities in the Tolon District and other neighbouring districts and towns in the Northern region of Ghana, notably the Kumbungu District and Tamale Metropolitan. Application of agrochemicals, especially pesticides and fertilisers, and surface runoff from domestic and wastewater effuents from the communities residing on the reservoir watershed may lead to contamination. While the fsh from the reservoir is commonly consumed for their high protein value, the accumulation of heavy metals in fsh muscles and organs is possible, which negatively impacts the health of the consumers. Therefore, the determination of heavy metals in the fsh is necessary to assess the extent of metal bioaccumulation and perform a human health risk assessment, especially in areas where fsh is frequently consumed. In Ghana, the per capita fsh consumption is estimated at 28 kg yr −1 , which is well above the African and world per capita averages of 10.5 and 18.9 kg yr −1 , respectively. 1 Furthermore, fsh accounts for as much as 60% of animal protein in the average Ghanaian diet and 22.4% of household food expenditures. It is estimated that the consumption rate is high in regions where fsh from local dams form a major source of animal protein. As of 2010, the Tolon District population was 72 990, that of the Tamale Metropolis was 223 252 while the Northern Region as a whole is home to 2 479 461 inhabitants. 2 The Agency for Toxic Substances and Disease Registry has identifed some heavy metals notably As > Pb > Cd > Ni > Zn > Cr > Cu > Mn in descending order as priority metals. 3 The World Health Organization (WHO) and Food and Agricultural Organization (FAO) have provided guideline values for acceptable levels of some heavy metals in food sources. 4 In this regard, various studies have been reported in the past decade to determine levels of heavy metals in fsh species worldwide for health risk assessment towards humans, 3–11 heavy metal poisoning for fsh 12–17 and as a biomarker for environmental contamination. 18–22 Most of these studies have been done on commercial fsh collected mainly from the sea and estuaries, while river fsh 22−24 and cultured fsh 25,26 are also mentioned. In Africa, most communities catch fsh species found in local dams for domestic consumption, while some are sold in nearby towns. However, monitoring of heavy metals in fsh remains limited, with only a few studies reported. A few human health risk assessment studies due to heavy metals in non-commercial fsh have been done for fsh collected from African rivers, dams and reservoirs. 21,27,28 Thus, this study investigated the levels of heavy metals (concentrations and bioaccumulation factors) and determined human health risk assessment (hazard quotients and cancer risk) due to consumption of the Oreochromis niloticus and Clarias gariepinus, respectively. The two freshwater fsh species breed naturally in the Golinga reservoir and are consumed locally by the indigenes and nearby communities. 2. Experimental 2.1. Chemicals and Reagents Nitric acid (70%, v/v) and hydrochloric acid (32%, v/v) were of analytical grade and purchased from Sigma-Aldrich (Johannesburg, South Africa). Certifed reference standards for elements were purchased from Supelco Belefonte, USA. Ultra- high purity water was generated at 18.2 MΩ cm −1 from a Milli- QRO4 system 117 (Millipore, Bedford, MA, USA). 2.2. Instrumentation An Agilent ICP-OES 700 Series (Agilent Technologies, Santa