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Transcript of University of NigeriaVirginia... · the staff and students of the university of nigeria, nsukka a...
University of Nigeria Research Publications
Aut
hor
OKENYI, Calister Ekperechi
PG/M.Sc/05/40088
Title
Concentration of CADMIUM, Lead and
Chromium in Human Whole Blood
Facu
lty
Physical Sciences
Dep
artm
ent
Pure and Industrial Chemistry
Dat
e
December, 2007
Sign
atur
e
CONCENTRATIONS OF CADMIUM, LEAD AND CHROMIUM
IN HUMAN WHOLE BLOOD
OKENYI, CALISTER EKPERECHI
PG/MSc/05/40088
DEPARTMENT OF PURE AND INDUSTRIAL CHEMISTRY
FACULTY OF PHYSICAL SCIENCES
UNIVERSITY OF NIGERIA, NSUKKA
DECEMBER 2007
CONCENTRATIONS OF CADMIUM, LEAD AND CHROMIUM
IN HUMAN WHOLE BLOOD
OKENYI, CALISTER EKPERECHI
PG/MSc/O5/40088
DEPARTMENT OF PURE AND INDUSTRIAL CHEMISTRY
FACULTY OF PHYSICAL SCIENCES
UNIVERSITY OF NIGERIA, NSUKKA
DECEMBER 2007
) BEING A THESIS SUBMITTED IN PARTIAL FULFILLMENT
FOR THE AWARD OF MASTER OF SCIENCE DEGREE IN I
ENVIRONMENTAL CHEMISTRY.
CERTIFICATION
This research work on "Concentrations of Cadmium, Lead and Chromium
in tiurnan Whole Blood" is the original work of the author. I t has not been
presented to any organization or any body for academic award or the like except
to the Department Pure 2nd Industrial Chemistry of University of Nigeria,
Nsu kka.
All quotations are indicated and the sources of the information are
specially acknowiedged by means of references.
Dr. C.0.B QKOYE
SUPERVISOR-
Dr. C.0.B BKOYE
HEAD OF DEW.
DEDICATION
This research work is dedicated to those who contributed in different ways in
sanitizing our environments.
ACKNOWLEDGEMENT
My special gratitude goes to Almighty God who is the fountain-head of
knowicdge and the one that made it possible for me to have carried out this
research. My parents Late Mr. and Mrs. Kierian Okenyi are also remembered for r my procreation. Also my heart-felt gratitude goes to my project supervisor Dr.
C.0.B Okoye for his immense contributions towards the success of my research
work and the postgraciuate programme generally from its inception.
I am also very thankful to all the lecturei-s in the Department of Pure and
l~~dustr ial Chemistry U.N.IU who made my postgraduate programme a success.
Pioreover, I am indebted to my classn7ates eq~ecialiy Chidi mma Okpara for her
beiievolence to me during the period of our course works. I also appreciate the
efforts of some staff of Bishop Shanalian Hospital Nsukka, U.N.T.H. Enugu,
Eastern Nigeria Medical Centre, Enugu, and National Orthopaedic Hospital Enugu
fo'r their kindness to me during my period of sampling.
I wish all God's favour and protection.
Okenyi Calister Dept. of Pure & Ind Chem UNM. December 2087.
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 CONTENT3
Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....................... Dedication ... . . . . . . . . . . . . . . I I
Acknowledgement ............ .. .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Abstracts ............. .. ........... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv -- I ab!e o.i conterits .......................................................................................... v
List of tables ................................................................................................... vii
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~ivironrnental Pollution ............ ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Blood ................................................................................................. 14
h'aernatotoxicity ................................................................................... 17
Storage Of Toxicants ............................................................................ 18
.................................... Cadmium, Lead And Chromium Occurrences 18
Heavy Metal Metabolisms I17 Man ....................................................... 19
............................................................... t-ieavy Metal Toxicity I n Man 22
Detoxification Of Heavy Metals In Man .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 24
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cetection Of Heavy Metals 25
. . . . . . . . . . . . . . . . . i ieavy 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 31
................................................................................. 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 34
CHAPTER FOUR
..................................... ......... 4.0 RESULTS AND DISCUSSION .. 35
4.1 Resuks of the analysis .............................................................................. 35
............................................................................................ 4.2 3iseussion 36
LIST OF TABLES
Table 1: Natural Concentrations of some Heavy Metals
in Aquatic and Soil Environments -- -- -- -- 10
Table 2: Typical Concentrations of Some Heavy Metals in Humans -- 11
Table 3: Concentration Limits of some Heavy Metals in Human Tissues -- 24 . Table 4: Characteristic Wavelengths of some Metal Atoms -- -- 2 6
Table 5: Fuel/Oxidant Combination for Flame AAS -- -- - - 2 8
Table 6: Concentrations of Cadmium Lead and Chromium in
Human whole Blood -- -- -- -- -- -- 35
LIST O F FIGURE
Standard Calibration Curve for AAS Metal Determinations -- --- 33
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
I n 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.
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 ENVIRONMENT
The natural environment is the place surrounding an organism. It
comprises of living and non-living things that occur naturally on the earth or
some part of it. It is made of the following components:
a. Complete landscape unit that functions as a natural system without
massive human intervention e.g. all plants, animals, rocks, and natural
phenomena that occur within their boundaries.
b. Universal natural resources and physical phenomena lacking clear-cut
boundaries e.g. air, water, climate, radiation, electric charge and magnetism not
from emanating human activity.
c. Natural features, which occur within the area heavily influenced by man
e.g: wild birds in urban areasI2
A geographical area is regarded as a natural environment if human impact
on it is kept under a certain limited level. On,the other hand, built environment,
which comprises of the areas and components that are heavily influenced by
man is not actually a natural en~ironment.~
2.2 ENVIRONMENTAL POLLUTION
This is the introduction of dangerous or harmful substances into the
environment which render it unsafe for both plants and animals found in it.6
These substances are called pollutants and may be in the form of chemicals,
noise, heat, energy, particles and so on. hey have deleterious effects which
endanger human health, harm living resources and ecosystem and impair or
interfere with amenities and other legitimate use of environment.
2.2.1 Forms of Environmental Pollution
The major forms of pollution to the environment include
a. Air pollution: This involves the release of chemicals and particulates
into the atmosphere. Common examples of air pollutants are carbon (11)
oxide (CO), sulphur (IV) Oxide (SOz), chloroflurocarbons (CFCs), and
nitrogen (IV) oxides produced by industries and motor vehicles.
Photochemical ozone and smog are created as nitrogen and
hydrocarbons react with sun~ight.~
b. Water pollution: This occurs through runoff, leaching, liquid spills,
wastewater discharge, eutrophication and littering.
c. Soil or land pollution: I n some cases, chemicals are released by spill
or underground storage tanks leakage causing soil contamination.
Among the most significant soil pollutants are hydrocarbons, heavy
metals, herbicides, pesticides, chlorinated hydrocarbons and methyl-tert-
butylether (MTBE).
d. Radioactive pollution: Radioisotopes are radioactive forms of
chemical elements. The nuclei of their atoms radiate or emit particles
and rays during the process of radioactive decay and di~tingeration.~
Each radioisotope has half-life (length of time required for the number of
the atoms in a sample of that isotope to decay to half the original
con~entration)~.
e. Noise pollution: It encompasses roadway noise, air-craft-noise,
industrial noise, as well as high intensity sonar.'
f. Light pollution: This comes from light trespass, over-illumination and
astronomical interference.
g . Thermal pollution: Sometimes, the human influence may cause a
change in the temperature of natural water b ~ d i e s . ~
h. Visual pollution: This form of pollution refers to the presence of
overhead power lines, motorway bill boards, scarred of trash or municipal
solid wates.'
2.2.2 Sources of Environmental Pollution
I n air pollution, motor vehicle emissions are the leading causes. Principal
stationary pollution sources include chemical plants, coalfired power plants, oil
refineries, petrochemical plants, nuclear waste disposal activity and incinerators.
Others include large livestock farms, polyvinyl chloride (PVC), metal production,
plastic factories and other heavy industriesm5
Some of the most soil contaminants are hydrocarbons, heavy metal e.g.
chromium and cadmium found in rechargeable batteries, lead found in paint,
aviation fuel and gasoline. Other contaminants include methyl-tert-butylether
(MTBE), zinc, arsenic and benzene. Ordinary municipal landfills are the sources
of many chemical substances entering the soil environment, emanating from the
wide variety of refuse.
Moreover, pollution can occur as a result of natural disaster like hurricane
which causes water contamination from sewage and petrochemical spills from
boats or automobiles. Nuclear power plants or oil tankers can produce
widespread and potentially hazard-oil chemicals released when accidents occur.'
The dominant source of noise pollution are motor vehicles and airplanesg
2.2.3 Environmental Pollution by Heavy metals
Some metals are regarded as heavy metals because their densities are
more than 5 g ~ m - ~ . Typical examples include lead, cadmium, mercury, arsenic,
chromium, nickel, zinc, copper etc. Among these, some are called essential
elements because they are needed in small quantities in both plants and animals
for different metabolic processes. These include zinc, copper, chromium etc.
Their deficiencies in an organism may cause deficiency syndrome and
abnormalities. Other heavy metals are classified as toxic elements because they
- do not perform any useful function in an organism rather they pose some
significant prob~ems.~
' 2.2.4 Interaction of heavy metals with the environment
All the trace elements have their primary origins from the earth's crust
which is made up of rocks. These rocks form the soil and sediment layers by
undergoing some physical and chemical processes like erosion weathering. The
soil and sediments subsequently became the terrestrial and aquatic substratum
for plants which absorbed, translocated, and in some cases biaccumulated these
elements. I n the food chain, when animals consume the edible parts of the
plants, these elements become incorporated into their bodies.''
Water on the other hand is a natural source of heavy metals. This is made
possible when rock undergoes natural weathering and leaching processes, and
by dissolving and reacting with materials, mobilizes and distributes the metals.
Volcanic activity, forest fires, oil dusts and salt sprays contribute both
aerosol and particulate of these metals in the a tm~sphere.~~. . Table 1 shows
~a tu ra l concentrations of some heavy metals in aquatic and soil environments5.
Metal
Cadmium
Zinc r-
Freshwater (us/ 1) 0.03
- - -
Concentration
As the geological and biological alteration of the earth's surface are slow, man'
input to heavy metal composition of the biosphere has been drastic, resulting in
widespread heavy metals' changes in environmental, biological and marine
systems.
The heavy metal contents in animal or body fluids are dependent on the
metal(s) content and bioavailability in the soil or sediment-plant-animal-human
food chain1'. Some common components of food in given diet can affect both
amount of the metals and their chemical forms. These accumulate in different
parts of the organism. Table 2 shows typical concentrations of some heavy
metals in humans5.
I Concentrations (uglg) dry weight
Cadmium 1 15 1 0.8 1 0.2 11 10.1
Kidney Hair Liver
Lead
Chromium
Mercury
Environmental pollution also occurs, when there is increase in the
concentrations of the heavy metals with respect to their natural concentrations in
the environmenf. Their increased concentrations are attributed to different
Arsenic --
Copper
Zinc
Milk
3
0.1
0.1
Blood
0.01
14
150
5
0.1
0.1
0.03
20
250
1 '
0.8
0.1
0.1
2 0
180
10
1.5
0.5
3
0.1
0.7
0.5
280
1500
1
1000
900.
anthropogenic activities like transportation, industrialization, mining, agricultural
practices and domestic activities.
2.2.5 Sources of heavy metals in the environment
Heavy metals sources to the atmosphere include coal and fuel power
generation plants, metal processing and smelting, transportation, combustion,
waste incineration and aerosol sprays (halocarbons). The major industrial
emissions are non-ferrous metal smelters, petroleum refining, cement
production, chloro-alkali production, aluminum smelters, petroleum refining and
chemical productions. The presence of small particulates of these metals in the
air poses global environmental pollution". These particles eventually descend on
vegetation and soil surfaces through brownian motion, sedimentation, impaction
and interception.
Mining and ore processing, coal and fuel combustion, industrial
*processing, agricultural (fertilizer, pesticides, and herbicides), domestic and
agricultural effluents are the major sources of heavy metal in natural water
bodies. Others are transportational (urban and motorway run-off), and nuclear
activity. They can also come from atmospheric fallout, leaching or dumping from
the lithosphere, or direct into the water bodies. The element concentrations of
these metals in water depends on magnitude of the input, duration of the input,
physical and chemical form of it etc. Some heavy metals undergo bio-
amplification or bio-transformation by plankton and bacteria respectively in water
bodies. Mercury, arsenic, tin, and lead undergo biomethylation in water sediment
interface, leading to the production of more toxic species which are concentrated
in shellfish.12
I n Nigeria, some researches carried out showed high concentrations of
some heavy metals (Cd, Fe, Mn, Ni, Zn, Pb, Co, Cu, Cr) in sediments from the
Lagos ~ a g o n ' ~ . Also the concentrations of Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb and Zn
were high in some fish and shellfish from the lagoon when compared to others
from rural rivers14. Analysis of some heavy metal concentrations in dried fish
from Nigerian markets revealed an enrichment of the metals in some of the fish
especially the ones from Lagos, Ilorin and Kano markets1'. The high
concentrations in the water bodies and fish are attributed to some of the sources
of these metals mentioned above.
Sources of heavy metals to the soil include metal smelting, chemical
process factories, coal and fuel, combustion plants, alongside motorways,
dsmestic and industrial waste incinerators. Different agricultural practices like
fertilizer, pesticides, sewage sludge and wastewater irrigation can also add these
metals to the soil.'
Plants can accumulate heavy metals from the soil, water and air thereby
becoming elemental sources for animals and man. The elemental absorption by
plants' root depends on the quantity and chemical form of the element present,
soil pH, moisture, aeration, temperature etc. Tobacco is a special food crop with
an unusual propinquity for bioaccumulation of Cd from the soil. Most times, the
accumulation of the heavy metals affects the metabolic processes in the plantslO.
However, analysis carried on the concentrations of some trace metals in some
Nigerian baked products showed low concentration of them in the products?
Besides other animals can serve as the source of heavy metals to man
when the later consumes the former. Although some of the metals are essential,
their concentrations more than the limit of safe exposure can lead to health
problems. Lead and cadmium concentrations were found to be above the
maximum permissible levels in meat samples obtained from different parts of the
country1'. These indicate that there is gradual contamination of our environment.
2.3 BLOOD
About 7-8% of human body weight is from blood. I t is an essential fluid
that carries out critical functions of oxygen and nutrient transportation to cells,
. as well as getting rid of carbon dioxide and other waste products from the body.
I t also plays a vital role in our immune system and in maintaining a relatively
constant body temperature. Human whole blood consists of different
components namely; red blood cells, white blood cells, platelets and plasma3.
2.3.1 Red Blood Cells ( ~ r ~ t h r o c ~ t e s )
These are relatively large microscopic cells without nuclei. They are similar
to the primitive prokaryotic cells of bacteria. They are biconcave disc with an
average diameter and their relative excess of surface over volume makes them
very deformable. These cells normally make up 40-50% of the blood volume.
They transport oxygen from the lungs to all living tissues of the body and carry
away carbon dioxide. Red cells are produced continuously in the bone marrow
from stem cells at about 2-3 million cells per second and they have life span of
about 120 days. The main contents are haemoglobin, variety of enzymes and
metabolic intermediates which are essential for the proper functioning of the
haemoglobin and for maintaining the integrity of the cel~s. '~
Haemoglobins are tetramer consisting of two y-and two non 7-globin
chains each with its own iron containing haem group. It makes up to 95% of a
red cell and performs the function of oxygen transportation. Each red cell has
about 270 million iron rich haemoglobin molecules.
When the cells are degraded by the reticulo-endothelial systems in the
spleen, the porphyrins of the haem portion of the haemoglobin are broken down
to bilirubin. The iron is released and transported to the bone marrow where it is
either incorporated into newly synthesized haem or stored in the reticulo-
endothelial cells as ferritin or haemosiderin. The globin peptide chains are
hydrolysed and their constituent amino acids re-enter the general metabolic
poollg. The bilirubin is excreted in the bile. People who are anaemic generally
have a deficiency in red blood cells. The red colour of the blood is primarily due
to oxygenated red cells.
2.3.2 White blood cells (Leucocytes)
White blood cells exist in variable numbers and types but make up a very
small part of blood's volume normally only about 1%. They occur elsewhere in
the body as well, most notably in the spleen, liver, and lymph glands. Most of
these cells are produced in the bone marrow while others are produced in the
thymus gland, which is at the base of the neck. The white cells called
lymphocytes are the first responders for our immune system. They seek out,
identify, and bind to alien protein or bacteria, virus, and fungi so that they can
be removed. Other white cells called granulocytes and macrophages then arrive
to surround and destroy the alien cells. They also have the function of getting rid
of dead or dying blood cells as well as foreign matters like dust and asbestors18.
White blood cells last for about 18-36 hours before they are removed although
some types live as much as a year. There are actually many specialized sub -
types of white cells but all participate in body defence mechanismlg.
2.3.3 Platelets (Thrombocytes)
They are cell fragments without nuclei that release blood clotting
chemicals at the sites of wounds. They do this by adhering to the walls of blood
vessels thereby plugging the rupture in the vascular walls.
There are more than a dozen types of blood clotting factors and platelets
that need to interact in the blood clotting process. Recent research has shown
that these platelets fight infections by releasing protein that kills the invading
bacteria and other micro-organisms. Also, the platelets stimulate the immune
system. They have a lifespan of 9-10 days and are about 113 the size of red
cells. They are also produced in bone marrow from stem cells20.
2.3.4 Plasma
Plasma is the non-cellular fraction of anti-coagulated blood. I t is the
relatively clear or yellow liquid water containing sugar, fats, protein and salt
solution which carries the red, and white cells, platelets and other chemicals.
About 95% of it is water. Plasma brings nutrients to different cells throughout
the body when the heart pumps the blood. I t also removes the waste products of
metabolism. Besides, plasma contains blood clotting factors, sugai-, lipids
vitamins, minerals, hormones, enzymes, antibodies and other proteins. Human
adult has a blood volume of roughly 5 litresZO *
2.4 HAEMATOTOXICIN
Apart from nutrients and waste products, some toxicants or poisons can
enter the body and get distributed by the blood to different organs and tissues
like kidney, liver, lung, heart and spleen etc. The factors that determine the rate
of. toxicant distribution include duration of exposure, dose, physical and chemical
nature of the toxicant, routes of administration, presence of lymphatic or blood
vascular components and volume of the toxicant etc.'
When there is presence of toxicants in the blood the quality and quantity
'
of the blood produced may be affected leading to impairment in the normal
functioning of the blood. This state of blood poisoning can be linked to the toxic
effects in the kidney, liver, skin, respiratory system, and central nervous and
peripheral nervous systems.
18 .
2.5 STORAGE OF TOXICANTS
Common storage locations for toxicants in humans include liver, kidney,
bone, lung, circulating plasma protein and fats2'. The kidney has he highest
blood flow/mass ratio (420m1/100g) of all the organs in the body. This is more
than four times greater than that of the heart muscles. This large volume of
blood exposes the organ to toxicants1.
Besides, liver is good for concentrating toxicants. This is because it has a
large blood flow/mass ratio. It receives the largest percentage of cardiac output
(27.8%). It is also the site where most toxicants undergo biotransformation
(process by which substances are changed from hydrophobic to hydrophilic
molecules to facilitate elimination form the body). Substances like lead and
strontium can substitute calcium ion in the bone. Fluoride may also be displaced
by hydroxyl ion and become incorporated into the bone matrix. Some poisons
can can be stored in albumin (plasma protein) and fat.'
- 2.6 CADMIUM, LEAD AND CHROMIUM OCCURENCES
Cadmium-containing ores are rare and when found, occur in small
quantities. Greenockite (CdS), the only cadmium mineral of importance, is nearly
always associated with sphalerite ( z ~ s ) ~ . CdS is released into the environment
naturally through volcanic actions. Other sources to the environment include
ocean sprays, and forest fires etc. Naturally occurring Cd is composed of 8
isotopes of which two of them show natural rad i~act iv i ty~~.
Lead is present at about 20ppm in the earth's crust and the medium of its
transport in the air are fine particulates ( 4 u m diameter). The residence time
for the particulates in the air is from several hours to several days. These
particles most often deposit on soil, get retained and eventually become mixed
into the surface layer and may be taken up directly by grazing animals and
micro-organisms22.
Chromium occurs in nature mostly as chrome iron ore (FeO. ~ r ~ 0 ~ ) ~ ~ . Its
concentration in the earth's crust is about 60ppb.
2.7 HEAVY METAL METABOLISM I N MAN
Cadmium is not essential in human and animal nutrition. Its
gastrointestinal absorption in humans is between 3-8010~~. The dietary level of
zinc and the solubility of cadmium salts influence this percentage. The absorption
of cadmium ions from the site of parenteral injection in the blood is rapid and
complete. Cadmium ion penetrates erythrocytes and gets distributed in the
blood. I t also binds to serum protein especially a-globulin and is readily
distributed to other tissues.25 Cadmium absorption through the skin is 'low but
absorption through the lungs during inhalation of its mist or aerosols from
tobacco smoking is fast and complete; only'the insoluble CdS remains in the
lungs unabsorbed thereby causing local inflammation and u~ceration*~. Greater
portion of the absorbed Cd is retained in the kidney, liver, reproductive systems
and lungs, but pancrease, aorta, oesephagus and omentum also accumulate Cd
under certain conditions, The reason for its retention in the soft tissues is
because of the presence of metallothionein in them for which cadmium has high
affinity for.
Excretion of Cd in mammals is slow and is predominantly faecal although
some quantity can also be removed in urine. The accumulation of it in humans
increases with age, with its level in kidney, liver and lungs increasing for
example, it is not detected in new borne babies but could be detected at 10
months of age2?
Inorganic forms of lead are absorbed through ingestion or inhalation
whereas organic Pb salts are absorbed through the skin. Only 10% of an
ingested dose of Pb is absorbed in adults but absorption in children may be up to
5 0 % ~ ~ . The absorption of Pb is enhanced by deficiencies of iron, calcium, and
zinc28. Under certain conditions, Pb is absorbed and stored in several body
compartments. About 5-10% of the absorbed Pb is found in blood, most of which
is. located in erythrocytes, hydroapatite crystals, where it is exchanged with the
blood. Inhaled Pb is absorbed more rapidly (about 90%) than by any other
route; lungs and the respiratory tract including nasal passages absorb Pb. About
40% of inhaled Pb gets trapped in the upper respiratory tract.
Intravenously administered Pb is distributed mostly in liver and bone,
while ingested one is distributed thus; bone (6O0/0), liver (25%), kidney (4%),
reticuloendothelial system (3%), intestinal walls (3%) and others (traces)26. Its
retention in mammalian skeleton is as follows; liver>
kidney>aorta>muscles> brain. I t can permeate the placental barrier and can be
found in milk.
Generally, excretion of Pb is slow with an estimated biological half-life (in
soft tissues) of 24-40days. The remainder of the stored Pb is found in some soft
tissues notably kidney and brain. The primary route of excretion is through
faeces (80-9O0/0). To a lesser extent, it is excreted through sweat and milk2'.
Tetraethyl lead (TEL) is readily absorbed from digestive, respiratory tracts
and skin due to its solubility in lipids and its diffusibility. Major portion of
absorbed TEL accumulates in the brain due to the special affinity of the organic
Pb to lipids in the nerve tissues26.
Chromium is essential in many aspects of animal life. It is an essential
component of the glucose tolerance factors2': Its requirement in normal human
adult is about 50ug and the average daily intake varies from 60-lOOug, This
represents about 5% of the total body contents, and there is a wide margin of
safety?
Gastrointestinal absorption of chromium ion is very low, less than 3%
regardless of nutritional status and dosage3'. The acidic value of the stomach
keeps it in trivalent form (cr3+) and reduces cr6+ to c?+ and the absorption of
c?+ from the stomach is negligible. Oxalates enhances this absorption while
phylates inhibit i t 2G. Intravenously administered cr3' salts and soluble form of
cr3+ absorbed from the alimentary tract into the blood bind progressively to
siderophilin, transferring albumins and y-globulin. Intravenously administered
cr6+ (chromates and dichromates) in physiological doses permeates the
erythrocyte membrane and is sequestered.
2.8 HEAW METAL TOXICITY I N MAN
Cadmium is a potential environmental hazard and is toxic in humans but
this depends on its dose and nature of its salt ingested. It induces depletion of
iron in liver causing anaemia due to lack of absorption of iron from the intestine.
I t also causes poor mineralization of vitamin D and absorption of calcium into the
bones leading to softening of the bones or osteomalacia". Besides cadmium
increases the retention of sodium ion in the kidney which leads to
hypertension32. Other symptoms of Cd toxicity are retardation in growth,
sterilization in sexes, tumour formation and tetratogenic effects (abnormal
structure) in children. Inhalation of dust Cd compound causes unnatural
distention and rupture of the air vesicles of the lungs (pulmonary emphysemia).
This is characterized by shortness of breath and bronchitis and so on.
Lead toxicity in man depends on the level of diffusibility and its
concentrations in soft tissues such as liver, kidney, and brain, than its total
concentration in the body33. Pb poisoning is cumulative in that its toxic symptoms
are not immediately seen after oral intake of a toxic dose, making it difficult to
assess the lethal doses2!
The major health effects of Pb manifest in three organ systems namely;
haematological, central nervous and renal systems. Its acute poisoning
symptoms include tiredness, vomiting, uncoordinated body movement,
convulsion, stupor, coma and death. Chronic toxicity systems are anaemia, brain
damage and general intellectual and psychological i m ~ a i r m e n t ~ ~ .
The effect of Pb on haematopoietic system are abnormal circulation of
erythrocytes, impairment of the production of haemoglobin and stimulation of
erythropoiesis in the marrow. This leads to morphological changes which cause
increased production of abnormal red cells, basophilic cells with nuclear
abnormalities and inadequate haemoglobin. Pb toxicity in central and peripheral
nervous systems affects the cerebellum, spinal cord, motor and sensory nerves.
Pb kncephalopathy is a disease of neonatal man and animal caused by transfer 1
of Pb through the maternal milk, the mothers are ~ n a f f e c t e d ~ ~ . Children are . P t , ~ ; l d r W A t t ~
more prone to central nervous dysfunction than adults. $3 %+ ,%,- F..#- -
Chromium poisoning in humans is caused by accidental ingestion of
chromates. cr3+ is one of the least toxic of the trace metals34. The cr6+ is more
toxic than c?+. cr6' is topically corrosive and its oral ingestion is toxic despite
the ability of the organism to reduce it to less toxic c?'. Accidental swallowing of
dichromates causes gastrointestinal ulceration and symptoms affecting the
central nervous system. Inhalation of cr6' compounds can cause injury to the
nasal mucosa leading to inflammation and ulceration. The larynx is also affected.
Chromium compounds are not carcinogenic when taken orally but
epidemiologic evidence implicates fine particles of Cr salts in pulmonary cancer35.
cr6' is an established human carcinogen. Table 3 shows the concentration limit
of some heavy metals in human tissues35.
Metal
Cadmium (blood)
urine
Lead (children blood)
adult blood
Mercury (blood)
(urine)
Arsenic (whole blood)
Serum/Plasma
Urine
Hair & nai (ug/g)
Normal concentration I Conc associated with Or less than (ug/l) serious toxicity (ug/l) 5 2 0
2.9 DETOXIFICATION OF HEAVY METALS I N MAN
High dietary intake of zinc, copper and iron in more than adequate
quantities increase the formation of metallothionein in kidney and liver thereby
reducing the toxicity of cadmium in man. Ascorbic acid, cystein, glutathione and
selenium in the body have some ameliorative effects on Cd toxicity by reducing
. Cd absorption in the body37.
Also dietary intake of calcium, iron, zinc, copper and phosphorus reduce
Pb absorption and retention in the body by making the parathyroid hormone
increase the urinary excretion of Pb. Zinc reduces its distribution, increases the
formation of metallothioneine content of the liver and kidney and increases Pb
binding to this protein3'. Pb shows high affinity for the sulfhydryl groups of
methallothioneine.
There is no specific mechanism by which chromium can be removed from
living systems but a possible detoxification of it can be the increased formation
of ribonucleoprotein in the liver3g.
. 2.10 DETECTION OF HEAVY METALS
The techniques required for analyzing heavy metals in samples must offer
low detection limits, wide linear dynamic range, simple interference free data and
qualitative, semi quantitative and quantitative analysis. Others include possible
simultaneous multi-element capacity, simple sample preparation and high
throughput and low cost per determination. The methods that can be employed
in analyzing heavy metals are atomic absorption spectrometry (flame and
electrothermal), atomic fluorescence spectrometry, inductively coupled plasma .
optical, neutron activation analysis, x-ray fluorescence etc.
2.10.1 ATOMIC ABSORPTION SPECTROPHOTOMETRY (AAS) PRINCIPLES
This is an instrumental method of analysis that measures the intensity of
absorbed light when a sample is aspirated into a flame4'. Light beam is directed
through flame into a monochromator (wave-length selector) and then into a
detector that measures the intensity of light absorbed based on Beer-Lambert
law of absorption, which states that the amount of light absorbed in a solution of
low concentration is directly proportional to the absorbing atoms irrespective of
the intensity of the light source40. This method of analysis is sensitive and
depends upon the presence of free unexcited atoms. Each metal has its own
characteristic absorption wavelength, a source lamp made up of that element
and these make the method relatively free of spectral interferences. Table 4
shows the characteristic wavelengths of some metal atoms4.
Metal
Chromium / 357.9
Wavelengths (nm)
Cadmium
Lead
228.8
283.3
Mercury
2.10.2 Interferences in AAS determination
This generally occurs when there is unabsorption due to atoms that are
bound in molecular combination in the flame. It can occur when the flame is not
hot enough to dissociate the molecules. It' can also result from immediate
oxidation to a compound of dissociated atoms5.
476.0
Copper
2.10.3 Instrumental requirements for AAS
The basic ones are
Light source
Sampling unit
Wavelength selector or monochomator
324.7
Detector
Readout device
Hollow cathode lamp (HCL) is a device used for producing radiation with
the necessary characteristics. I t is made up of a glass envelope containing anode
and cathode electrodes. The cathode is either made from the analyte or packed
with a non-volatile form of it. On striking the cathode (sputtering), atoms of the
cathode material are ionized and volatilized. On relaxation, radiation with the
appropriate sharpline characteristic is produced.
The components of the sampling unit are nebulizer, spray chamber and
the burner. The nebulizer is used for the appropriate proportioning of the fuel
and support gasses and in breaking of the solution into fine vapour, liquid,
aerosol or mist. The burner on its part receives the mist, converting it into
unexcited state by evaporating the solvent followed by decomposition of the
molecules. Table 5 shows the fuel/oxidant combination for flame A A S ~ .
Cadmium
Lead
Chromium
Mercury , -. - - .. - -- Copper
Zinc
Aluminum
Fuel and oxidant combination
Air-Acetylene
Air-Acetylene
Air-Acetylene
Air-Acetylene
Nitrogen 1 oxide-Acetylene
Wavelength selector or monochromator is used to isolate light of narrow
bandwith. It may be made of quartz prism or gratings. The later consists of a
glass or shining metal sheets with equidistant drawn lines and can resolve light
better than the quartz prism. The detector is made of a photoelectric cell and
can convert light signal reaching it into electric current. Types of photoelectric
cells are barrier layer and photomultiplier cells. Read-out device is used to bring
out the result or output of the analysis .it can be meter, chart recorder, digital
display system or computer connected to printer4!
2.11 HEAW METAL ANALYSIS I N BIOLOICAL SAMPLES USING AAS
2 1 1 . 1 Sampling
Carefulness is needed for sampling of biological tissue and fluids. The
nature of the proposed analysis determines the type of the sample to be
collected. When human being is concerned, it may be required from neonatal,
postnatal, children, adult, pregnant or in some cases from chronic disorder
patients. The tissues or fluid that can be sampled include scalp hair, urine, blood,
and nail.
. Samples are to be collected with clean and sterile material in order to
prevent contamination. Stainless steel blades, biopsy needles, metal scissors or
tweezer are to be avoided if the analysis is for metals. Blood samples are to be
taken using Teflon or polyethylene catheters. Urine requires mid-stream samples
to be put into a covered acid washed polyethylene container. Animal organs
should be collected with a quartz or tantalum blade5.
2.11.2 Sample preparation
The method of sample preparation to be used should be one devoid of
contamination of the sample. Hair sample require ultrasonication with 0.1%
tritonTm ~ 1 0 0 , filtration, washing with methanol and repeated double -distilled
deionised water. Blood, urine, milk and tissue sample may require dry freezing
before digestion.
2.11.3 Dry Ashing
Muffle ashing occurs at 500-550% and can decompose most organic matter. The
problem associated with dry ashing is that it may lead to volatilization of
mercury, arsenic, tin, selenium, lead, nickel and chromium in the sample
although this problem can be reduced by adding an ashing aid like concentrated
nitric acid. On the other hand, this method is always simple and convenient.
2.11.4 Wet Digestion
This method is always preferred for biological tissues and blood. This is
because much of the elements components of the sample are not lost through
vapourization. The mineral acids that can be used include perchloric acid, nitric-
hydrofluoric acid mixtures. (1 : l HN03/HF), nitric acid and hydrogen peroxide,
aqua regia etc. Biological tissues and fluids can be digested in Kjeldahl digestion
vessels, with controlled temperature heating mantle. Digestion in open vessel
may lead to volatility of some element but it can be controlled using pressurized
decomposition with nitric acid in Teflon digestion bombs. .
2.11.5 Precautions needed in wet digestion
i . Digestion of very fine powdered samples must be restricted to less than
50mg of samples, and only a maximum of 2ml of H N 0 3 should be added.
ii. Avoiding the digestion of biological materials containing more than 20% fat
content.
iii Digestion of organic material generate large amount of vapour, therefore
'
carefulness is needed and warm vessels should not be opened.
Wet digestion limitation is that it is slow, labour intensive, and
requires strict carefulness by the analyst"
CHAPTER THREE
3.0 EXPERIMENTAL
3.1 SOURCES AND COLLECTION OF THE SAMPLES
Whole human blood samples were obtained from different blood banks in
Enugu state. Samples 1-5 were obtained from the University of Nigeria Teaching
Hospital (UNTH) ltuku - Ozalla, Enugu; samples 6 and 7 were from Eastern
Nigeria Medical Centre, Enugu; samples 8, 9 and 10 were from the National
Orthopaedic Hospital, Enugu; and sample 11 was from Bishop Shanahan Hospital
Nsukka. Each sample contained little quantity of citrate phosphate dextrose
adenine solution which served as the anticoagulant.
3.2 APPARATUS AND EQUIPMENT USED
i Syringe (10 ml capacity )
ii. Evaporating dishes / crucibles
iii: Electric heater
iv. Tongs
v. Electric oven
vi. Muffle furnace
. vii. Beakers
viii. Standard flasks (25 ml capacity)
ix. Atomic absorption spectrophotometer, Model Pye Unican sp 1900.
3.3 REAGENTS USED
i Hydrochloric acid (BDH AnalaR grade)
i. Nitric acid (BDH AnalaR grade)
iii. Stock and standard solutions of cadmium, lead and chromium.
iv. Distilled - deionized water.
3.4 PREPARATION OF SAMPLES (ASHING)
1Oml of each of the samples were drawn into a clean and dry evaporating
dish using a 1Oml capacity syringe. The samples in the evaporating dishes were
heated to dryness using an electric heater. This was followed by addition of l m l
conc nitric acid to each of the samples to serve as an ashing aid. After a little
while, these acidified samples were re-heated in the fume cupboard until they
started charring. The samples were loaded into a muffle furnace and were
allowed to ash at 500°C for four hours. The dishes with their contents were
allowed to cool in the furnace before removing them. Each of the resulting
sample ash was dissolved in aqueous 1M HCI solution, and made up to 25mI with
distilled - deionized water using a 25ml standard flask. These were used for the
AAS analysis.
3.5 PREPARATION OF HEAVY METALS STOCK SOLUTIONS
a 1.63099 of cadmium chloride CdCI2 was dissolved in distilled-deionized
water and made up to 1 litre to give 1000 ppm of cadmium solution.
b 1.59859 of lead nitrate Pb(N03)2 was dissolved in distilled-deionized water
and made up to 1 litre mark to give 1000ppm of lead solution ,
c 2.82859 of anhydrous potassium heptachromate (K2 Cr2 O7 ) was dissolved
in distilled-deionized water and made up to 1 litre mark to give 1000ppm
of chromium solution .
Each of these stock solutions was diluted to obtain the working standard .
solutions of cadmium, lead and chromium which were used for the AAS analysis.
3.6 DETERMINATION OF THE METALS
A Pye Unican Sp 1900 atomic absorption spectrophotometer (AAS) was
used. The hollow cathode lamp for the metal to be analysed was installed and
aligned. The wavelength was set according to the user's manual for the metal to
be analysed (see table 4). The flame was put on and the flow rates of the fuel
(acetylene) and oxidant (air) were regulated accordingly to optimize the flame.
The burner was adjusted for stability and maximum absorption.
The standard solutions were run and their concentrations against
absorbances were plotted as in figure 1 b,elow to check for linearity. Each
standard solution was run three times to check for accuracy and precision.
Fig 1: A standard calibration curve
Metal concentration
Afterwards, blank was run to check instrumental drift or contamination followed
by the aspiration of each sample into the flame. The concentrations of the
analytes in each sample were obtained from the instrument directly.
3.7 CALCULATION
Each of the concentrations of sample obtained from the instrument was
multiplied by the dilution factor which was 2.5 to get the actual concentrations of
the metals in 1 litre of blood sample.
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
4.1 RESULTS
Table 6 below shows the results of the analysis on the concentrations of
cadmium, lead and chromium in human whole blood samples.
Table 6 Concentrations of cadmium, lead and chromium in .human
whole blood (pg/l).
Note: B.D.L = Below detection limit.
Sample No Concentrations in pg/l' blood I ~d I ~b ~r
4.2 DISCUSSION
From Table 6, all except samples 3, 7 and 10 have concentrations of
cadmium more than the limit of safe exposure which is 5 u g / 1 ~ ~ . This suggests
that the donors of these blood samples were exposed to cadmium sources like
smoking, cadmium containing diets, water, and cadmium compounds. The
cadmium may also had found its way into the donors by ingestion and inhalation.
The effect of Cd toxicity is cumulative as its half- life is more than 10
years25. Cadmium toxicity causes kidney, liver, reproductive organ, and lung
dysfunctions as these are the major organs of, accumulation. This is as a result of
the metallothionein found in them for which cadmium has high affinity33. Other
effects of cadmium poisoning are hypertension, osteomalacia, cancer and
teratogenic effects in women2?
Nevertheless, cadmium detoxication can be enhanced by dietary intake of
zinc, copper and iron38. Also ascorbic acid, vitamin D, cystein, glutathione and
selenium have ameliorative effects on cadmium toxicity. Chelating agents like
edetate calcium disodium (CaNa-EDTA) can be used to eliminate Cd from the
body since it can form Cd complex which can be removed through urine.
The concentrations of lead in samples 5, and 9 were found to be more
than the maximum permissible limit in adult which is 300ug/l of blood36. All other
ones were within the range of safe exposures. Lead contamination has therefore
not been as serious as calcium in the environment. Donors of samples 5 and 9
may have been exposed to lead through ingestion, inhalation or even absorption
3 7
through the skin. I t is possible that motor mechanics absorb lead through the
skin.
Lead toxicity manifest mainly in three organs namely; haematological,
central nervous and renal systems. The symptoms include mild anaemia,
production of abnormal red cells, and basophilic cells with nuclear abnormalities.
Others include central and peripheral nervous systems dysfunction leading to
cerebellum, spinal cord, motor and sensory nervous problems26. As Pb toxicity is
cumulative, it also affects kidney function. Other symptoms are liver dirrhosis,
bone 'deformity and brain damage which may lead to general intellectual and
psychological impairment in children27.
Lead toxicity symptoms sometimes do not manifest immediately as it
depends on the concentration of diffusible lead in soft tissues. However, the
body can convert the diffusible form to non-diffusible state in ~ i d n e ~ ~ ~ . Lead
poisoning can also be reduced by intake of diets rich in zinc which enhances the
formation of metallothionein in soft tissues. Dietary intake of Ca, Fe, Cu and P
reduces Pb metabolism in the body. Chelating agents like CaNa-EDTA,
dimercaprol and 2-3 dimercaptosuccinic acid (succimer DMSA) can be used.
These provide sulfhydryl groups of metallothionein for which lead has much
affinity'. The complex can be eliminated through urine, faeces, sweat and milk".
Chromium is a micro nutrient in man. I t is needed in insulin activity and
membrane transport of cell metabolites. The results of the analysis revealed that
the concentrations.of chromium in the blood samples were low and could not be
detected in most of the samples. This may probably be as a result of low
absorption of the ingested metal into the body irrespective of its dose. The body
can also convert the hexavalent chromium to trivalent chromium in the stomach.
Thus there is wide margin of safety with regards to chromium toxicity.
4.3 CONCLUSION
The results of the analysis of human (adult) whole blood samples indicate
the extent of environmental pollution. From the result, about 72.7O/0 of the
samples have cadmium concentration more than 5ug/l. 18.2O/0 of the samples
have concentrations of lead to be more than the limit of safe exposure which is
300ug/l. All the samples had low concentrations of chromium.
All these indicate that our environment is getting more contaminated with
cadmium as a result of different human activities like transportation, and
emission of urban and industrial wastes into the total environment (air, water,
and land).
4.4 RECOMMENDATIONS
From the results of this research work, the followings are recommended:
1. People should be made to understand the importance of safe environment.
This will encourage them to maintain good and clean environment.
2. The public should be given the awareness on what environmental pollution is
all about, its dangers and effects on living organisms including man. This will
educate everyone to protect himself well against pollutants and encourage
. proper disposal of wastes.
3. New technologies should be adopted for recycling of wastes (where
applicable) to reduce the volume of wastes that will be channeled into the
environment.
4. The use of toxic materials should be substituted with the ones less toxic
(where there are alternatives).
5. The effluents from industries should be properly treated before releasing into
the environment.
6. Government should make it a point of duty to provide funds and facilities for
proper disposal of wastes especially in urban areas.
7. Bio-degradable materials should be used as containers and wrappers more
than the non-bio-degradable ones.
' 8. Scientists should be encouraged to go into environmental analysis in order to
ascertain the levels of pollution and the possible solutions that can be
proffered.
. 9. Individuals should be encouraged to know the level of heavy metal- in their
systems. This will help in directing them to the required diets or treatments
that could be given to reduce the toxicities of the metals (where applicable).
This will save much and even increase life spans of individuals.
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