TABLE OF CONTENTS

Title page    –         –         –         –         –         –         –         –         –         i

Certification –         –         –         –         –         –         –         –         –         ii

Dedication   –         –         –         –         –         –         –         –         –         iii

Acknowledgement –         –         –         –         –         –         –         –         iv

Table of contents   –         –         –         –         –         –         –         –         v-vi

CHAPTER ONE: INTRODUCTION

1.0     INTRODUCTION –         –         –         –         –         –         –         1-5

CHAPTER TWO: HEAVY METALS IN ROUTE AQUATIC SYSTEMS

2.1     Transport of Heavy metals in the environment        –         –         6

2.1.1  Atmospheric transport     –         –         –         –         –         –         7

2.12   Biological Transport        –         –         –         –         –         –         7

2.1.3  Aquatic Transport  –         –         –         –         –         –         –         7-8

2.2     Transformation of Heavy metals in the environment         –         8-9

CHAPTER THREE: CONTAMINATED FISH WITH HEAVY METALS

3.1     Health Hazards of fish     –         –         –         –         –         –         10-11

3.1.1  Health effects of Cadmium        –         –         –         –         –         11-12

3.1.2  Health effects of Lead     –         –         –         –         –         –         12-13

3.1.3  Health effects of Mercury          –         –         –         –         –         13-15

3.1.4  Health effects of Arsenic –         –         –         –         –         –         15-16

CHAPTER FOUR: SUMMARY AND CONCLUSION

4.0     SUMMARY AND CONCLUSION

4.1     Summary     –         –         –         –         –         –         –         –         17-18

4.2     Conclusion  –         –         –         –         –         –         –         –         18-19

             References

CHAPTER ONE: INTRODUCTION

1.0 Introduction

Fish, an important source of food for humans is also a key component in many natural food webs. Fats, fat-soluble vitamins and protein is obtained from fish. The high quality protein from fish is better for human health than that in meat and poultry. Fish consists of 15 – 24% protein; 1 – 3% carbohydrate; 0.1 – 22% lipid; 0.8 – 2% inorganic substances and 66 – 84% water. Akman et al., (2012).

Each of these is important for human health, growth and intelligence. Fish play an important role as it is an important source of trace minerals and calcium. It also provides calories, nutrients such as fat, vitamins (B complex and D), elements such as, phosphorus, sodium as well as trace elements. Fish may easily absorb pollutants from the ambient water and from their food and then deposit them in the

tissue through the effects of bioconcentration and bioaccumulation. In this regard, heavy metals have long been recognized as an important pollutant due to their toxicity and ability to accumulate in marine organisms. Some of the identified toxic metals are arsenic, beryllium, cadmium, chromium, cobalt, tin, zinc, copper, iron, lead, manganese, aluminium, mercury, and selenium. Intengite et al., (2010).

Heavy metals differ widely in their chemical properties, and are used extensively in electronics, machines and the artifacts of everyday life as well as in high-tech applications. As a result, they are able to enter into the aquatic environment and food chains of humans and animals from a variety of anthropogenic sources as well as from natural sources Al. Yousuf et al., (2000). The main sources of contamination include; mining wastes, landfill leaches, municipal wastewater, urban runoff, and industrial waste waters particularly from electroplating, electronic and metal finishing industries. Many aquatic environments face metal concentrations that exceed water quality criteria designed to protect the environment, animals and humans. The problems are exacerbated because metals have the tendency to be transported with sediments, are persistent in the environment and can bio-accumulate in the food chain. ATSDR et al., (2007).

Cadmium is used widely in electroplating industries, solders, batteries, television sets, ceramics, photography, insecticides, electronics, metal finishing industries, and metallurgical activities. It can be introduced into the environment by metal-ore refining, cadmium containing pigments, alloys and electronic compounds, cadmium containing phosphate fertilizers, detergents, and refined petroleum products.

Rechargeable batteries with nickel cadmium compounds are also sources of cadmium Dojlido et al., (1993). Arsenic is found naturally in the deposits of earth’s crust worldwide. The word “arsenic” is taken from Zarnikh in Persian literature, which means yellow pigment Mudhoo et al., (2001). It was first isolated as an element by Albert Magnus in 1250AD. Arsenic exists in powdery amorphous and crystalline forms in the ores. In certain areas, the concentration of arsenic may

be higher than its normal dose and creates severe health hazards to human beings and animals. It enters the environment through the natural weathering of rocks and anthropogenic activities, mining and smelting processes, pesticide use and coal combustion.

The toxicity of arsenic as a result of the contamination of ground water bodies and surface waters is of great concern. Arsenic exists as arsenate, As (v), and arsenite, As (iii), in most of the groundwater Berg et al., (2001). Adsorption and solution pH commonly controls the mobility of arsenic in the aqueous environment. Metal oxides of Fe, Al, and Mn play a role adsorption of arsenic in aquatic bodies. The natural sources of mercury are volcanic eruption, weathering of rocks and soils, whereas anthropogenic mercury comes from the extensive use of the metal in the industrial applications, its mining and processing applications in batteries and mercury vapor lamps Berg et al., (2001).

Extensive use of chromium compounds in industrial applications has discharged huge amounts of waste water containing toxic chromium species into water bodies. Chromium enters into the environment by natural inputs and anthropogenic sources. Volcanic eruptions geological weathering of rocks, soils and sediments are the natural sources of chromium whereas, anthropogenic contributions of chromium come from the burning of fossil fuels, production of chromates, plastic manufacturing, electroplating of metals and extensive use in leather and tannery industries Mohan D, et al., (2006). Nickel occurs naturally in the soils and volcanic rocks. Nickel and its salts are used in several industrial applications such as in electroplating, automobile and aircraft parts, batteries, coins, spark plugs, cosmetics and stainless steel and is used extensively in the production of nickel-cadmium batteries on an industrial scale. It enters into the water body naturally by weathering of rocks and soils and through the leaching of minerals. The water soluble salts of nickel are the major problems of contamination in aquatic systems. Paint formulation and enameling industries discharges nickel containing effluents to the nearby water bodies. Nickel is also found in cigarettes as a volatile compound commonly known as nickel carbonyl WHO.