TABLE OF CONTENTS

Title Page    –         –         –         –         –         –         –         –         –         i

Certification           –         –         –         –         –         –         –         –         ii

Dedication   –         –         –         –         –         –         –         –         –         iii

Acknowledgments –         –         –         –         –         –         –         –         iv

Table of Contents   –         –         –         –         –         –         –         –         v-vi

CHAPTER ONE: INTRODUCTION        –         –         –         –         1-3

CHAPTER TWO

2.1     Formation, Abundance and Occurrence of Heavy Metal    –         4-7

2.2     Sources of Heavy Metal Exposure to Humans         –         –         7-8

2.3     Toxic Metal in Industrial Effluents      –         –         –         –         9

2.4     Route of Exposure, Bio-uptake and Bioaccumulation

of Heavy Metals in Humans      –         –         –         –         –         9-11

2.5     Biological Role of Some Heavy Metals         –         –         –         11-12

CHAPTER THREE

3.1     Health Effects of Heavy Metals Toxicity in Humans         –         13

3.1.1  Arsenic        –         –         –         –         –         –         –         –         13-14

3.1.2  Lead  –         –         –         –         –         –         –         –         –         15-16

3.1.3  Mercury       –         –         –         –         –         –         –         –         16-18

3.1.4  Cadmium     –         –         –         –         –         –         –         –         18-19

3.1.5  Chromium   –         –         –         –         –         –         –         –         19-21

3.1.6  Iron   –         –         –         –         –         –         –         –         –         21-22

3.1.7  Manganese   –         –         –         –         –         –         –         –         22-23

CHAPTER FOUR: SUMMARY AND CONCLUSION

4.1     Summary     –         –         –         –         –         –         –         –         24

4.2     Conclusion  –         –         –         –         –         –         –         –         24

           REFERENCES

CHAPTER ONE: INTRODUCTION

Heavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context (Pourret et al., 2021).

In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. More specific definitions have been published, but none of these have been widely accepted. The definitions surveyed in this article encompass up to 96 out of the 118 known chemical elements; only mercury, lead and bismuth meet all of them. Despite this lack of agreement, the term (plural or singular) is widely used in science. A density of more than 5 g/cm³ is sometimes quoted as a commonly used criterion and is used in the body of this article (Pourret et al., 2021).

Metallic elements are intrinsic components of the environment. Their presence is considered unique in the sense that it is difficult to remove them completely from the environment once they enter in it. Metal constitute an important class of toxic substance which are encountered in numerous occupational and environmental circumstances. The impact of these toxic agents on human health is currently an area of intense interest due to the ubiquity of exposure. With the increasing use of a wide verity of metals in industry and in our daily life, problems arising from toxic metal pollution of the environment have assumed serious dimensions (Manju, 2015).

These heavy metals are distributed in the environment through several natural processes such as volcanic eruptions, spring waters, erosion, and bacterial activity, and through anthropogenic activities which include fossil fuel combustion, industrial processes, agricultural activities as well as feeding (Florea et al., 2004).

These heavy metals do bioaccumulate in living organisms and the human body through various processes causing adverse effects. In the human body, these heavy metals are transported and compartmentalized into body cells and tissues binding to proteins, nucleic acids destroying these macromolecules and disrupting their cellular functions. As such, heavy metal toxicity can have several consequences in the human body. It can affect the central nervous function leading to mental disorder, damage the blood constituents and may damage the lungs, liver, kidneys and other vital organs promoting several disease conditions (Monisha et al., 2014).

Also, long term accumulation of heavy metals in the body may result in slowing the progression of physical, muscular and neurological degenerative processes that mimic certain diseases such as Parkinson’s disease and Alzheimer’s disease (Monisha et al., 2014). More so, repeated long-term contact with some heavy metals or their compounds may even damage nucleic acids, cause mutation, mimic hormones thereby disrupting the endocrine and reproductive system and eventually lead to cancer (Jarup, 2003).