Quest Journals Journal of Research in Environmental and Earth Sciences Volume 7 ~ Issue 8 (2021) pp: 12-16 ISSN(Online) :2348-2532 www.questjournals.org *Corresponding Author: Aliyu Kangiwa Ibrahim 12 | Page Research Paper Assessment of Heavy Metals Contamination in Some Selected Fish Species in Ajiwa Dam and Their Impact on Human Health Aliyu Kangiwa Ibrahim 1 *, Sadiq Alhaji Sani 2 and Anas Haruna 3 1 Department of Science Laboratory Technology, Federal Polytechnic Kaura Namoda, Zamfara State, Nigeria. 2 Department of Pure and Industrial Chemistry, Federal University Dutsin-ma, Katsina State, Nigeria. 3 Department of Chemistry, Federal University Gusau, Zamfara State, Nigeria. ABSTRACT Chemical pollution in marine ecosystems is leading towards an increase in the concentrations of heavy metals in fish body, which might have a negative impact on human health through consumption of fish. This study revealed that the highest EDI value in the studied fish species (Tilapia zillii, Catfish, Marcusenius brachiystius and Bagrus bayad) was found to be for Zn followed by Fe˃ Pb ˃Cu˃Cd; respectively. THQ values for all studied metals for all the fish species were˃1, which indicates cancer risk due to consumption of those fish species. On the other hand, the target cancer risk for Pb was found to be within an acceptable level (10 −4 to 10 - 6 ). KEYWORDS: Pollution, aquatic environment, toxic metals, carcinogenicity and consumption. Received 24 July, 2021; Revised: 07 August, 2021; Accepted 09 August, 2021 © The author(s) 2021. Published with open access at www.questjournals.org I. INTRODUCTION In recent years, the pollution of aquatic environment with heavy metals has become a worldwide problem because of their potential toxic effect and accumulation in tissues and organs of aquatic organisms. Heavy metals can enter the human food through water, air, soil, plants and animals[1]. The determination of toxic elements in food has prompted studies on toxicological effects of these elements in food. Fish is an important component of the human diet. It is generally appreciated as one of the healthiest and cheapest source of protein; with amino acid compositions that are richer in cysteine than most of the other sources of protein[2]. Aquatic environment is one of the receiving ends for pollutants, particularly heavy metals which are ploughed back into the food chains through bioaccumulation in plankton and invertebrates; to fishes and finally biomagnified in man. Heavy metal concentrations in aquatic ecosystems are usually monitored by measuring their concentrations in water, sediments and associated biota, which generally exist in low levels in water and attain considerable concentration in sediments and biota. Sediments are important sinks for various pollutants like pesticides and heavy metals while also playing a significant role in the remobilization of contaminants in aquatic systems under favorable conditions and in interactions between water and fish species[2,3]. Heavy metals pollution in fish has become a crucial worldwide concern, not only because of the threats to fish, but also due to the public health risks combined with fish consumption[4-8]. Unfortunately, however, published research concerning heavy metals contamination in most commercial fish species and their health risk assessment is very limited. Therefore, this study was designed with the aim of filling that gap, with the following specific objectives: estimating the concentrations of chromium (Cr), copper (Cu), zinc (Zn), and cadmiun (Cd) in some commercially important fish species, assessing the present status of heavy metals pollution in commercially important fish species, and assessing the human health risk for heavy metals by consuming the fishes under the study.