MATRIC NO: 2014/IK/0552









   NOVERMBER, 2017



This is to certify that this project work was carried out by AKIBU ZAINAB ABISOLA of the Department of Biology /Chemistry, College of Education, Ikere-Ekiti, Ekiti State.



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Project Supervisor                                                                  Date






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Head of  Department                                                    Date





          This project is dedicated to almighty Allah (SWT) for His Guidance, mercy and blessing upon me. Similarly it is also dedicated to my beloved parents Mr. and Mrs Akibu Kolawole and my siblings.



          All Praises and adoration belongs to none but Allah (SWT) for His divine love, protection, mercy, guardians, knowledge, wisdom  and  confidence which He gave me throughout the course of my study and also in carrying out this project, May His peace and blessing be upon our noble Prophet Muhammed (SAW) his household, companion and those who follow His guidance till Eternity.

I acknowledge the wonderful work done by my able supervisor Mrs. I O Ojo who painstaking corrections and suggestion were germane to the success of this project when convenient  and inconvenient. May almighty God continue to be with you.

My Immeasurable Appreciation goes to my beloved parents MR. Akibu Kolawole   and my dearest Mother Mrs. Akibu Yemisi. They serve as vehicle through which I came to this world they are the ones who stood by me through the thick and thin both morally and financially and made sure I lacked nothing which may hinder my Education. I pray to Allah (SWT) to make them live long to witness and reap the fruit of their labour. JAZAKULLLAH KYRAN.

My special thanks geos to my family members Akibu  Abdulmatin, Abdulwaris, Olamide, Grandma Mrs. Lamidi., Mrs Adepoju, May God continue to honour You all.

My acknowledgement would not be completed  without mentioning my friends and beloved ones Abdul-lateef Ismail, my school mother Basiru Ramatallahi, Abdul Gafar, Dosunmu Yetunde, Mr. Bakare Alfa Saheed, Olajumoke, MSSN  COEIK and other who have contributed in one way or the other to successful outcome of this work, You have all been very special people and I pray Almighty Allah to continue to bless you abundantly. I say JAZAKULLLAH KYRAN.

Lastly, I use this medium to congratulate myself to have accomplished the program through the unending grace of God Over my life. May Almighty Allah crown my effort with success (Ameen).


Title Page

Certificate page



Table of Contents



1.0  Introduction

1.1  Background of the study

1.2  Composition of Trace Metals In Foods


2.0  History of heavy metals

2.1  Toxicology of heavy metals

2.1.1 Symptoms of exposure and toxicity Lead

2.2.1 Symptoms of lead poisoning

2.2.2 General effect of lead poisoning

2.2.3 Acute toxicity

2.2.4 Chronic lead intoxication

2.2.5 Potential sources of lead poisoning

2.2.6 Population majorly affected

2.2.7  Lead  Removal by Chelation

2.3   Cadmium

2.3.1  Effect of cadmium on the environment

2.3.2  Acute toxicity

2.3.3   Chronic toxicity

2.3.4 Production and sources of cadmium

2.3.5   Uses of cadmium

2.3.6   Rates of Exposure to Cadmium

2.3.7  Population Exposure to cadmium

2.4      Copper

2.4.1   Sources of Copper on the Environment

2.4.2   Dietary Source of Copper

2.4.3   Effect of Copper

2.4.4   Copper in the Body

2.4.5   Copper toxicity

2.5      Zinc

2.5.1   Sources and requirement

2.5.2   Toxicity of zinc

2.5.3   Recommended dietary allowance

2.6    Preventing heavy metal poisoning


3.0    Design and   Methodology

3.1      Sampling sites

3.2′     sampling and sampling records

3.2.1   Discussion on vegetables

3.3      Sample preservation and pretreatment

3.3.1 Sample preservation and pretreatment for leafy &fruity vegetables

3.4         Total metal determination

.4.1     wet digestion method for leafy and fruity vegetables

3.5       Preparation of store solution

3.5.1    Cadmium stock solution (l000ppm)

3.5.2    Zinc stock solution (l000ppm)

3.5.3    Lead stock solution (1000pm)

3.5.4    Copper stock solution (l000ppm)

3.6       Preparation of standard

3.6.1    Preparation of 2M nitric acid

3.7       Calibration of atomic absorption spectrophotometer

3.8       Recovery study procedures

3.8.1    Preparation of standard for recovery studies Preparation of  1000ppm zinc stock to obtain l00ppm Zinc Recovery study Preparation of 1000ppm copper stock to obtain 100ppm Copper Recovery study Preparation of  1000ppm cadmium stock to obtain 100ppm  Cadmium Recovery study Preparation of 1000ppm lead stock to obtain 100ppm Lead Recovery study

3.9    Quality Assurance and Quality Control.

3.9.1  Cleaning of sample containers

3.9.2  Relative percent difference of duplicate samples


4.0   Result and discussion

4.1   Result

4.2   Discussion

4.2.1  Zinc

4.2.2  Copper

4.2.3  Lead

4.2.4  Cadmium

4.2.5  Recovery study result of all the metals (Zn, Cu, Cd and Pb)


5.0  Conclusion and recommendation

5.1  Conclusion

5.2  Recommendation

Further Research



Vegetables are kinds of food items grown to supply dietary vitamins and certain minerals. They may contain essential element which immunize against disease while some may be contaminated with toxic metals that are injurius to health. One gramme of the dried samples was digested and made to 25mls with demonized water. The digested vegetables solution were analysed fro Zn, Cu, Cd, and Pb with Buck Scientific Atomic Absorption Spectrometer (AAS).

The metal concentration for the vegetables are as follows Zn levels ranged from l00mg/kg in tomatoes to 18.4 mg/kg in okro, Cu levels ranged from 0.36mg/kg in tomatoes to 6.30 mg/kg in onion, Cd levels ranged from a non-detectable value (ND) in onion to-0.09mg/kg in okro and Pb levels ranged a non-detectable value in green vegetables to 0.05mg/kg in garden egg. All the metals concentration are within the recommended safe limit by FAO/WHO. The presence of essential Zn and Cu in this vegetables could a positive effect on the cognitive functioning of the pupils.



1.1       Background of the study

Heavy metal is member of a loosely subset of element hat exhibit metallic properties it mainly includes the transition metals some metalloids, lanthanides and actinides. Many different definitions have been proposed some based on density some on atomic number or atomic weight and some on chemical properties or toxicity.

The term heavy metal have been called a misinterpretation in an IUP AC technical report due it the contradictory definition and its lack of a coherent scientific basis there is an alternative term toxic metal for which no consensus of exact definition exist either. Example of heavy metal include lead, mercury and cadmium les commonly any metals with a potential negalre health effect or environmental impact may be termed a heavy metal such as cobalt chromium lithium and even iron

Heavy metals constitute a very heterogeneous group of elements widely varied in their chemical properties and biological function .heavy metals are kept under environmental pollutant category due to their toxic effect on plants, animals and human being. Heavy metals contamination of soil result from anthropogenic as well as natural activities such as mining, smelting operation and agriculture have locally increased the levels of heavy metal such as Cd, Co, Cr, Pb, As and Ni in soil up to dangerous level .heavy metal are persistent in nature therefore get accumulated in soil and plants. Heavy metal Interfax with physiological activities of plant such as photosynthesis, gaseous exchange and nutrient, absorption, and cause reductions in plant growth dry matter accumulation and yield .heavy metal also interface with the level of antioxidant in plant and reduce the nutrient value of the produce. Dietary intake of many heavy metals through consumption of plant has loan term detrimental effect on human heath.


The importance of food composition take in nutrition planning and provision of basic research data for epidemiological studies have been highlighted by brace and Barnstorm (1983) and Holden , Schubert and Wolf (1987) .The quantity and quantity of data available is however recognized to be several, limited (Bressani 1983).

Heavy metals composition of foods is of interest because of their essential or toxic nature ‘ Onianura et, al. 1999). The accumulation of heavy metals can have middle term and long heath risks and strict periet severance of these contaminant is therefore advisable (Cabrera et, al. 1995). 19100 nutrients constitute a small fraction of the entre diet but plan important role :n different metabolic process (Akhter et, al 2002). Vegetable originated from plants and some cash crop.

Vegetable are derived from these plants which are consumed in relatively small quantities as an side dishor a relish with sample food. Most vegetable are leaves, root or stem of herbaceous plants although flowers, claviers, immature seed or fruit may also be consumed as vegetables. Nutritionally, vegetable are good source of vitamin, protein minerals fibers and the form part of the composition of same of the important dishes in the tropical area .

In African, three major classes of vegetable are consumed (i)those that are gathered from the wild such as baobab leaves of purslane (portulica) (ii) indigenous vegetable which are gathered bill are also cultivated . Such as amarathus, (iii) important vegetables species which are cultivated. Only been known, this selection should not however be consumed as diminishing the important of gathered vegetables

Heavy metals such as cadmium, lead, copper and zinc of food is of interest because they know toxic metals with on beneficial effort to man and wildlife. (Tyler, 1981, boraman 1983). Environmental pollution is the main cause of heavy metal contamination in food chain (Canoe et, al 1995). Cadmium can enter the agricultural food chain through uptake by plant of cadmium naturally present in soil, from anthropogenic inputs a the atmosphere, disposal of sludge on agricultural land and from the application of phosphate fertilizes (Wotlaros and David, 1976). The degree of heavy metal uptake by plants is know to be influenced by factor such as oil PH (Alloway, 1990: Fade et, al, 1971.). Soil organic matter and sesquiotxide content fertilize practices, choice of crop and seasonal influence (Oliver et, al 1994).

Trace of these metals can be round naturally in the environment but industrial activities can increase their levels and lend to pollution Adeniran et, al 1990).

According to flam (1978), root absorbed most of the environment cadmium nickel whereas pb is mainly absorbed through leaves and aecral deposition. A number of author have reported that cd accumulation by crops can be influenced by Zn supply to the plant. (Haghiri 1974; Homa and Hirata, 1978 Abbl Sabour et; al, 1988). Feed chain ph has very chorinie health implication. Ingestion could lead metal retardation in children (Hughes et, al, 1980). Colic anemia and renal disease (chban 1992) in recent times, heavy metals have metals have been reported in vegetable grown on abandoned Ph-Zn tailings pvod (Jeanne and side, 1991) and lead (ph)on vegetable grown hear busy traffic high Mays (Ihenyen, 1991, Ndiokure, 1984), heavy metals on some Nigeria beverages and food drinks (Owanwa et, al, i995) and cadmium, lead and nickel contamination on vegetable content (Alegroa et, al 1991). Environmental pollution is the main cause of heavy .metal contamination in food chain the trace metal content of individual food varies and is dependent upon the trace metals introduced in the growing , transport , processing and fornication of food Anderson et,al 1992).the other technological processes used to bring the food the consumer can significantly increase the total trace metal contents of the food (Carbrera, et , al, 2003).wide variation in concentrations of trace metal have been reported in boilon cubes, minced speas, natural plant spices and nuts (Akpanying, 2005, Garcir et al 200: scatter et, al 1989; Ansani et, al 2004). Zinc is a metal with great importance and in particular necessary in collection replication and development of the immune response (Salgveiro et al, 2002).

Similarly iron plays an essential role in any metabolic processes including oxygen transport, oxidative metabolism and cellular growth. In human beings it is absorbed primary in the dueodenum, transported through the blood stream and extra cellular fluid bound to transferring, and stored intracellulary predominantly in the form of feritin (Lunch, 1997). Environment pollution is the main cause of heavy metal contamination in the food chain and pb and are two potential harmful metals that have aroused considerable concern (Cabrera et, al, 2003).








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