ABSTRACT
Human whole blood samples obtained from blood banks in different hospitals in
Enugu State were analyzed for cadmium, lead and chromium concentrations
using atomic absorption spectrophotometric method. The results of the analysis
showed that about 72.7% of the samples had cadmium concentrations more
than the limit of safe exposure (5ug/l of blood). Also about 18.2% of the
samples had the concentrations of lead to be more than the maximum
permissible limit in adult human blood which is 300ug/l. On the other hand,
chromium concentrations in all the samples were within the range of its safe
exposure as it is a micro nutrient in man. The concentrations of cadmium and
lead could be indicative of both environmental and occupational exposure
hazards.
TABLE OF CONTENTS
Certification ………………………………………………………………………………. i
Dedication …………………… .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I I
Acknowledgement ………… .. ……………………………………………………………..i.i.i
Abstracts …………. .. …………………………………………………………………………. iv
—
I ab!e o.i conterits. …………………………………………………………………………….v.
List of tables ……………………………………………………………………………………..v. ii
CHAPTER ONE
1.0 INTRODUCTION ………. .. ………………………………………… I
1 1 Environmental pollutariis ………………………………………………………. 1
1.2 ..Trace met& in tiurnan Blood …………………………………………………. 2
3 Sources and effect of trace metals in humat-i blood ……………………. 2
1.4 A iins m d objectives of this research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.5 Scope of the study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
CHAPTER TWO
2.0 LITERATURE REVIEW ………………………………………………..6.
2.2 . Environment ………………………………………………………………………..6..
E~ivironrnentaPl ollution …………. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6. .
Blood ……………………………………………………………………………………. 14
h’aernatotoxicity ……………………………………………………………………….1. 7
Storage Of Toxicants …………………………………………………………………1.8
Cadmium, Lead And Chromium Occurrences ……………………………… 18
Heavy Metal Metabolisms I17 Man ………………………………………………. 19
t-ieavy Metal Toxicity In Man ……………………………………………………..2. 2
Detoxification Of Heavy Metals In Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . …. 24
Cetection Of Heavy Metals ………………………………………………………2..5.
iieavy Netai Analysis Iri Biologicai Sz;-n$cs ;;sing A9.S . . . . . . . . . . . . . . . . . 28
CHAPTER THREE
3.0 EXPERIMENTAL. ……. … …………… b
3.1 Sources and coliecticn of Lhe samples ……………………………………… 31
3.2 Apparatus and equipment used ……………………………………………..3..1.
3.3 Reagents used ……………………………………………………………………… 32
3.4 Preparation of the samples. …………………………………………………….. 32
3.5 Preparation of the heavy metal stock solutions …………………………… 32
3.6 Determinations of the metals …………………………………………………… 33
3.7 Calculation. ……………………………………………………………………………3..4.
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION ……… .. ………………………………. 35
4.1 Resuks of the analysis …………………………………………………………………… 35
4.2 3iseussion. ……………………………………………………………………………….3 6
CHAPTER ONE
1.0 INTRODUCTION
11 Environmental Pollutants
Human beings have significant impact on the environment especially now
that there has been much increase in human population. The increase in
population had led to corresponding increment in human activities like
industrialization, transportation, mining and agricultural processes which
generate different substances that can influence the environmental make ups
negatively. When these occur, our environment is said to be contaminated or
polluted.’
Environment can be defined as the place surrounding an organism. It
includes both biotic (living) and abiotic (non living) factors that affect the
organism in the surroundings. Land (lithosphere), water (hydrosphere), and air
(atmosphere) make up our environment and these serve as the buckets where
wastes are channeled or disposed.
Environmental pollution is the introduction of harmful substances or
toxicants into the environment thereby making it (environment) unsuitable for
both plants and animals living in it. It can be in form of land, water or air
pollution and some of the pollutants have cumulative effects in both plants and
animals. These effects depend on the biological chemical, and physical
characteristics, concentrations of the toxicant in the environment, and can lead
to either death, ill-health or both2.
1.2 Trace Metals in Human Blood
In man, blood is one of the body fluids and serves as a medium for
toxicant distribution because it is connected to other tissues and organs in the
. body. The distribution of the toxicants occurs when they are ingested, inhaled or
absorbed through the skin. Human blood is made up of the solid cells or
corpuscles namely; red blood cells (erythrocytes), white blood cells (leucocytes),
and platelets (thrombocytes). The liquid portion of the blood where the cells are
suspended is called the plasma. Functions of blood include; distribution of
oxygen carrying pigment called haemoglobin, protection of the body against the
invasion of micro-organisms, formation of blood clots to prevent excessive blood
loss when injury occurs and so on. Other substances found in blood are mineral
salts, food materials, hormones etc. An adult man contains about 5.5 litres of
blood and this constitute about 7% of the total body eight.^
P.3 Sources and Effects of Trace Metals in Human Blood
Haematotoxicity is the state of blood contamination as a result of the
presence of toxicant(s) in it. This state of blood affects its quality or quantity
produced in the bone marrow. I t can be linked to malfunctioning of other tissues
like kidney, liver, lung, bone, and the peripheral and central nervous systems etc.
1
Heavy metals are those metals that have their densities to be more than
5g/cm3. They include; cadmium, lead, chronlium, mercury, arsenic, tin and so
on4. Some of them like cadmium, lead, arsenic and mercury are considered toxic
in man no mater their concentrations5. They are also called trace elements
because their concentrations in the natural environment are low. Among these
elements, some are called essential elements in man because they are needed in
small quantities for different metabolic processes in the body e.g. chromium,
copper, zinc, iron, selenium etc.
The earth’s crust is the major source of cadmium, lead and chromium of
the various environmental systems. The rocks that form the soils were initially
subjected to various physical and chemical processes like erosion weathering.
Subsequently, soils and sediments became the terrestrial and aquatic substratum
for plants which absorbed, translocate and in some cases bioaccumulate some of
these elements. These lead to the incorporation of these elements in man and
other animals when they consume the plants.
Water gets contaminated with heavy metals through natural weathering
and leaching, and by dissolving and reacting with them. I t also mobilizes and
distributes them to different sites. Volcanic activity, forest fire, soil dusts and salt
sprays bring about both aerosols and particulates which are the major sources of
the metals to the atmosphere5. Some quantity of these elements in the
atmosphere can deposit on the plants, soil, water or can be inhaled directly by
human beings and other animals thereby increasing the concentrations of the
metals in the body.
As the effects of cadmium, lead and chromium are cumulative, they
accumulate in target organs and soft tissues like kidney and liver thereby causing
4
some impairment in the functioning of these organs. This is made possible
because of a protein called metallothionein found i
and lead bind to very strongly.
More concentrations of cadmium are found
liver while liver accuinulate most of the lead than
in soft tissues which cadmium
in the kidney followed by the
the other soft tissues. Equal
concentrations of chromium are obtained in kidney, liver and blood.
1.4 AIMS AND OBJECTIVES OF THIS PROJECT
This research is aimed at evaluating the extent of environmental pollution
by heavy metals in Nigeria. It is meant to ascertain quantitatively the
concentrations of cadmium, lead and chromium in the blood of adult Nigerians as
a result of their exposures to different environmental and occupational hazards.
Besides it is expected to serve as an eye-opener on environmental
degradation and will go a long way in enlightening the general public on the
importance of keeping good environment. This will inculcate good habits of
proper waste disposals in individuals. It is also targeted at making people
understand the problems associated with heavy metals and will help the public in
protecting themselves against the sources of these metals in order to reduce
pre-mature death and ill-health.
1.5 SCOPE OF THE STUDY
The scope of this study is quantitative determination of the concentrations
of cadmium, lead and chromium in human whole blood of adult Nigerians. The
modes of administrations, rates of accumulations, sources and speciations of
these metals in the blood samples are not included.
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