ABSTRACT
In this study, the degree of contamination with selected heavy metals were determined in fifty common food spices in Southeastern Nigeria.Samples were purchased from three major markets namely, Nkwo market Nnewi, Ose market Onitsha and Ogbete main market Enugu. Two grams of dried ground spice samples were digested using 2:1 HNO3/HClO4, mixture and analysis of metals were carried out using a GBC Avanta ver. 2.02 atomic absorption spectrophotometer. Results (in µg/g) show that the range of detectable values of the fruits, vegetables, and other natural spices were Cd (0.02 –3.1), Co (0.009 –12.25), Cu (0.06 –15.08), Cr (0.14-23.43), Fe (0.40-472.33), Mn (0.098-182.00), Ni (0.15-11.05), Pb (0.08-125.77). Other metals in mg/g are Na (0.0056-6.75), K (0.053-481.91), Ca (0.18-3.497), Mg (0.068-1.641). Values obtained for the processed spice samples in µg/g were Cd (0.03-93.28), Co (0.132-20.19), Cu (0.020-11.38), Cr (1.27-27.64), Fe (1.26-395.27), Mn (1.28-74.55), Ni (0.58-9.72), Pb (0.122-60.24). Others in mg/g are Na (0.011-7.15), K (0.017-4.69), Ca (0.006-0.127) and Mg (0.021-0.907). The natural spice samples from Onitsha contained the highest concentrations of Cd, Fe and Pb, those from Nnewi contained the highest concentrations of Co, Mn, Ni, Na, K, and Mg while Enugu samples contained the highest concentrations of Cu,Cr and Ca. Mean concentrations of Cd, Pb, Na, K and Mg were above international maximum permissible levels in some of the natural samples while the Mean concentrations of Cd, Na, K and Mg were within international maximum permissible levels in some of the processed samples. One way analysis of variance showed no significant difference in levels of Cd, Co, Cu, Cr, Ni, Pb, Na, K and Mg in the natural and processed spice samples (P>0.05) while Fe, Mn and Ca showed significant difference (P<0.05). However, Fe and Ca showed significant difference (P<0.05) in the processed smaples. Cd, Fe and Ca accumulated mostly in smaples from Onitsha; Co, Cu, Na, Cr, Ni and Mg accumulated mostly in samples from Enugu while Mn and K accumulated mostly in samples from Nnewi. Smaples of natural spices from Onitsha had the lowest concentrations of Co, Cu, Cr, Mn, Ni, Na and Pb. Those from Nnewi contained the lowest concentrations of Cd, K and Mg while those from Enugu contained the lowest concentrations of Fe and Ca. These show peculiarities in geochemistry and contamination levels of the areas studied. The concentration of heavy metals determined in this study when compared with the Food and Agriculture Organization (FAO) dietary guideline values were found to be within safe levels. From previous survey, the levels of consumption of natural and processed spices of our people were quite low, therefore the consumption of heavy metals from the sources studied would not pose any danger to the consumers if the level of consumption of spices is maintained as previously reported.
TABLE OF CONTENTS
Title Page i
Approval Page ii
Certification iii
Dedication iv
Acknowledgements v
Abstract vi
Table of Contents vii
List of Tables viii
CHAPTER ONE
1.0 INTRODUCTION 1
1.1 Food spices and their uses 2
1.2 Importance of spices and culinary herbs 3
1.2.1 Health benefits of Food and culinary Herbs: 3
1.3 Heavy metals bioavailability and effects 4
1.3.1 How to use Spices and Herbs 4
1.4 Sources of Food Spices in South East Nigeria 5
1.5 Contamination of Food Spices 5
1.6 Toxic Metals in Food Spices and their Effect 6
1.7 Importance of mineral elements 8
1.7.2 Calcium 8
1.7.3 Iron 8
1.7.4 Cobalt 8
1.7.5 Magnesium 9
1.7.6 Copper 9
1.7.7 Sodium and potassium 10
1.8 Effects of Deficiency in mineral elements 10
1.8.1 Copper 10
1.8.2 Iron 10
1.8.3 Cobalt 11
1.8.4 Magnesium 11
1.9 Procedure for Heavy Metal Analysis 11
1.9.1 Sampling 12
1.9.2 Sample preparation 12
1.9.3 Precautionary measures in Heavy metals Analysis 12
1.9.4 Wet digestion 13
1.9.5 Dry ashing 14
1.9.6 Instrumental analysis of metals 15
1.9.6.1 Atomic Absorption spectroscopy 15
1.9.6.2 Atomic emission spectrometry 17
1.9.6.3 Atomic Fluorescence Spectrometry 17
1.9.6.4 Anodic stripping voltametry 18
1.9.6.5 Inductively coupled plasma-mass spectrometry (ICP-MS) 18
1.9.6.6 X-ray fluorescence spectrometry 19
1.9.6.7 Neutron activation analysis 19
1.10 Statement of Problem 19
1.11 Aim and Objectives of the study 20
CHAPTER TWO
2.0 Literature Review 21
2.1 Contamination of Processed Food Spices 21
2.2 Occurrence and characteristics of some metals in the environment 21
2.2.1 Lead 22
2.2.2 Cadmium 22
2.2.3 Nickel 23
2.2.4 Manganese 23
2.2.5 Chromium 24
2.2.6 Copper 24
2.2.7 Calcium 24
2.2.8 Sodium 25
2.2.9 Iron 25
2.2.10 Magnesium 26
2.2.11 Cobalt 26
2.2. 12 Potassium 26
2.3 Heavy Metals in Nigerian Soils 27
2.4 Heavy Metals in Plants 28
2.5 Food and Environmental Contamination in Nigeria 30
2.6 Improper waste disposal 36
2.7 Heavy metals in processed materials in Nigeria 40
2.8 Review of heavy metals pollution in different parts of the world 40
2.8.1 Lead 41
2.8.1.1 Air 41
2.8.1.2 Water 41
2.8.1.3 Soil 42
2.8.2 Cadmium 43
2.8.2.1 Air 43
2.8.2.2 Water 43
2.8.2.3 Soil 44
2.8.3 Nickel 44
2.8.3.1 Air 44
2.8.3.2 Soil/Water 44
2.8.4 Chromium 46
2.8.4.1 Air 46
2.8.4.2 Water 46
2.8.4.3 Soil 49
2.9 Biological functions of heavy metals 52
2.10 Detrimental effects of heavy metals 52
2.10.1 Lead 52
2.10.2 Cadmium 52
2.10.3 Chromium 53
2.11 Methods for reducing toxic effects of heavy metals 54
2.11.1 Lead 54
2.11.2 Cadmium 56
2.11.3 Manganese 57
2.11.4 Chromium 58
2.11.5 Nickel 59
2.12 Bioavailability of heavy metals 60
2.12.1 Factors that influence bioavailability of heavy metals 61
2.12.2 Geochemical and environmental processes that affect bioavailability of Heavy metals
61
2.12.3 Brief summaries of some factors controlling unavailability of heavy metals 62
2.12.3.1 Lead 62
2.12.3.2 Cadmium 62
2.12.3.3 Nickel 63
2.12.3.4 Manganese 64
2.12.3.5 Chromium 65
2.13 Variables influencing tolerance of heavy metals by humans 65
2.13.1 Stage of physiological development 65
2.13.2 Nutrition and Metal-Metal Interaction 66
2.13.3 Liquid Diets 67
CHAPTER THREE
3.0 Experimental 69
3.1 Sample collection and identification 69
3.2 Washing of glass wares 69
3.2.1 Preparation of Sample 73
3.3 Digestion of samples 73
3.4 Preparation of metal standard solution 74
3.4.1 Preparation of stock solutions (1000 ppm) 74
3.4.2 Preparation of mixed standard solutions 74
3.5 Determination of metal concentrations 75
3.6 Determination of Moisture content 75
3.7 Determination of Daily Dietary intake 75
CHAPTER FOUR
4.0 Results 77
CHAPTER FIVE
5.0 Discussion and Conclusion 106
5.1 Quality Assurance 106
5.2 Heavy metals in fruits, vegetables and other natural spices 107
5.2.1 Cadmium 107
5.2.2 Cobalt 108
5.2.3 Copper 108
5.2.4 Chromium 109
5.2.5 Iron 110
5.2.6 Manganese 110
5.2.7 Nickel 111
5.2.8 Lead 111
5.2.9 Sodium 113
5.2.10 Potassium 113
5.2.11 Calcium 114
5.2.12 Magnesium 115
5.3 Variation in values of Metals in Fruits, Vegetables and Other Natural Spices 115
5.4 Daily Intake Rate 117
5.5 Conclusion 119
5.6 Contribution to knowledge 119
5.7 Recommendations 120
References 121
Appendix I 148
 
LIST OF TABLES
Table 2.1: Average concentrations of cadmium in foods (mg/kg) 32
Table 2.2: Lead levels in canadian foods 43
Table 2.3: Content of nickel in natural water 46
Table 2.4: Chromium content in naturally occurring waters 48
Table 2.5: Chromium content in various foods in United States of America 50
Table 2.6: Manganese concentrations in selected foods in United States of America 51
Table 3.1: Fruits and vegetables and other natural spices 70
Table 3.2 Processed spice sample used for the study 72
Table 4.1: Concentration of Cd, Co, Cu and Cr in Natural spices in South Eastern Nigeria (µg/g) 78
Table 4.2: Concentrations of Fe, Mn, Ni and Pb in Natural spices in South Eastern Nigeria (µg/g) 80
Table 4.3: Concentration of Na, K, Ca and Mg in Natural spices in South Eastern Nigeria (mg/g) 82
Table 4.4: Concentration of Cd, Co, Cu and Cr in Processed spices in
Southm Eastern Nigeria (µg/g) 84
Table 4.5: Concentration of Fe, Mn, Ni and Pb in Processed spices in South Eastern Nigeria (µg/g) 85
Table 4.6: Concentration of Na, K, Ca and Mg in Processed spices in South Eastern Nigeria (mg/g) 86
Table 4.7: Mean Concentrations (n = 3) of heavy metals in all samples [fruits, vegetables and natural spices) (dry weight) (µg/g)] from the various markets 87
Table 4.8: Mean Concentrations (n= 3) of heavy metals in all samples [fruits, vegetables and natural spices (dry weight) (µg/g)] from the various markets continued 89
Table 4.9: Mean Concentrations (n= 3) of essential elements in all samples [fruits, vegetables and natural spices (dry weight) (µg/g)] from the various markets 91
Table 4.10: Mean concentrations of heavy metals (µg/g) (dry weight) in processed spices 94
Table 4.11: Mean concentrations of essential elements (µg/g) (dry weight) in processed spices continue 95
Table 4.12: Variation in Concentrations of Metals in natural spices in various markets 96
Table 4.13: Mean Concentrations of heavy metals (µg/g) (dry/wt) in processed spices from each markets 97
Table 4.14: Daily intake (g/person/day) of heavy metals (DIM) through Consumption of contaminated fruits, vegetable and other natural spices 98
Table 4.15: Daily intake (g/person/day) of heavy metals (DIM) through Consumption of contaminated fruits, vegetable and other natural spices 99
Table 4.16: Daily intake (g/person/day) of essential elements (DIM) through Consumption of contaminated fruits, vegetable and other natural spices 101
Table 4.17: Daily intake (g/person/day) of heavy metals (DIM) through consumption of Contaminated processed spices 103
Table 4.18: Daily intake (g/person/day) of essential elements (DIM) through consumption of contaminated processed spices 104
Table 4.19: Daily intake (g/person/day) of essential element (DIM) through consumption of contaminated processed spices 94
CHAPTER ONE
1.0 INTRODUCTION
Since the 1980s, the use of spices and culinary herbs has increased tremendously in most regions of the world, including Europe and North America, mainly because of their medicinal values. For instance, during this period, herbal medication in the USA has grown into an industry worth yielding an average of $1.5 billion per year, with projected annual growth of 15% (Abebe, 2006). Many common spices have outstanding antimicrobial effects. However, the process of preparation and handling can make them a source of food poisoning (Sherman et al., 1998). With the current emphasis on eating more healthy diets that are low in fat and salt, people are turning to various herbs and spices to flavor their food. The culinary herbs and spices that are used to enhance the flavor of food, soup, stir-fry, and pasta dishes can be derived from the bark, buds, flowers, leaves, fruits, seeds, rhizomes, or roots of plants. The presence of essential elements like iron, copper, nickel, sodium, potassium, calcium, magnesium and zinc are very useful for the healthy growth of the body, though very high levels are intolerable. Metals like mercury, lead and cadmium are toxic at very low concentrations and are are always checked in foods. Frequent use of spices that may have been contaminated with heavy metals as a habit may result in accumulation of these toxic metals in human organs and could pose different health challenges (Al-Eed, et al., 1997). These metals may contaminate vegetables, fruits and canned foods through air, water and soil and during industrial processing and packaging (Ozores-Hampton et al., 1997). Food spices sold in Nigerian markets are often exposed to diversity of conditions and environments before they reach the consumers. There is no doubt that along the route from the producer to the users, as well as during processing, these commodities, could become contaminated with sand and grit, dust, smoke, particulates, pathogens and heavy toxic metals.
The study of heavy metals in the environment and organisms is crucial because they have potential hazardous effects on human. Although, they are generally present in agricultural soils at low levels (Ozkutlu, et al., 2006), monitoring the levels of heavy metals in spices would help ascertain the health impacts of consuming these spices, and provide relevant data on heavy metals content of spices. Regulatory bodies such as National Agency for Food and Drug Administration and Control (NAFDAC) would be aided or informed of the safety or otherwise of the use and circulation of these spices especially the processed ones. Metallic elements are of significance in daily diets because of the nutritional value of some and possible harmful effects of others. Metals like iron, copper, chromium, nikel, zinc, cobalt and manganese are essential elements since they play important roles in biological systems; whereas mercury, lead and cadmium, are non-essential and toxic even in trace amount (Reilly, 1991; Skuvikhin, 1993; Iyengar, 1989). However, these elements can also have harmful effects when their intake significantly exceeds the recommended values. Spices are important sources of nutrition and flavoring for humans (Somer, 1974; Graham et al., 1976; Prasad, 1976). Some are parts of plants which have been used as diet components are often used to improve color, aroma, palatability and acceptability of food. They consist of rhizomes, barks, leaves, fruits, seeds and other parts of the plant (Sattar, et al., 1989). Most of these are fragrant, aromatic and pungent. The bulk of dry material of spices contains carbohydrate, and organic compounds having diverse functional groups. 1.1 Food Spices and their Uses
