ABSTRACT
The increasing levels of environmental pollution by toxic metals from various sources have generated a great concern on their impact on human health. Rapid developments, increase in mining activities, farming, insurgency, industrial activities and waste disposals have gradually redistributed many of the toxic metals from the earth crust to the environment, raising the chances of exposure through ingestion, inhalation or skin contact. This study is aimed at determining the concentrations of zinc, copper, nickel, lead and arsenic metals in four compound fish feeds [FA, FB, FC and FD] poultry feeds [PA, PB, PC and PD], forage grasses; animal manure and major rivers (Kaduna, Sokoto and Ngadda) obtained in northern Nigeria. Brands of compound fish and poultry feed samples were collected from five different distributors of the feeds. Forage grass and manure samples from five different grazing pasture stations in north central, north western and north eastern zones of Nigeria were collected. Water samples were also collected from the rivers Kaduna, Sokoto and Ngadda. The samples were digested with concentrated nitric acid (HNO3), concentrated sulphuric acid (H2SO4) and perchloric acid (HCIO4) in the ratio 1:2:1 (Uba et al.., 2000). The Percentage recovery of the metals using the analytical method adopted gave range of 92.07 to 101.02% for feeds and 92.22 to 103.13% for manure was determined for the heavy metals by atomic absorption spectrophometry. The results obtained expressed in mg/kg for livestock feeds showed mean concentration ranges between 5.10 ± 0.04 – 6.38 ± 1.50 mg/kg for zinc as the highest concentrated heavy metal, followed by 3.06 ± 1.08 mg/kg – 3.16 ± 1.65 mg/kg for copper, then 0.14 ± 0.08 – 0.38 ± 0.25 mg/kg for lead, 0.10 ± 0.44 – 0.19 ± 0.07 mg/kg for nickel, and 0.01 ± 0.02 – 0.05 ± 0.04 mg/kg for arsenic as the lowest concentrated metal in the compound fish feeds. For compound poultry feeds, the same trend as in fish feeds was observed with a concentration range of 5.06 ± 1.67 – 8.45 ± 1.91 mg/kg for zinc, 3.00 ± 3.06 – 35 ± 1.08 mg/kg for copper, 0.72 ±0. 81 – 1.41 ± 0.08 mg/kg for lead 0.04 ± 0.02z – 0.10 ± 0.06 mg/kg for nickel and non detection – 0.03 ± 0.01 mg/kg for arsenic. FA and PB feed brands contained higher concentrations of the essential metals than the other brands sampled. The levels of the metals in the feeds were below the permissible limit stipulated by European Union. The mean concentrations of these metals in forage grasses being grazed by cattle in northern Nigeria had highest zinc and copper levels (7.00 ± 2.04 mg/kg and 6.61 ± 0.82 mg/kg) respectively and highest arsenic concentration (0.33 ± 0.06 mg/kg) was obtained in Kagara areas while highest nickel level (0.83 ± 0 .56 mg/kg) was obtained in Zungeru area, all in
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North central zone. The levels were below the permissible limit (100 mg/kg) stipulated by European Union. The mean lead value 6.53 ± 0.51 mg/kg and 5.82 ± 0.63 mg/kg were obtained in Anka area, North west and Zungeru, North central Nigeria respectively and were above 5mg/kg stipulated by European Union for lead in feeds. The trend of the metal levels in poultry and cattle manures were Zn > Cu > Ni > Pb > As and Pb > Zn > Cu > Ni > As respectively. The highest mean concentration 4.15 ± 2.64mg/kg was obtained in poultry manure related to zinc in North central while highest mean concentration 3.22 ± 0.01mg/kg in cattle manure is related to lead in Anka area in North western Nigeria. The feeds are relatively safe for aquaculture and livestock production. However, the forage grasses are relatively not safe for grazing by animals due to high lead levels. The high lead values in water samples indicate that Northern Nigerian environment is critically contaminated with respect to this toxic metal and thus pose serious environmental concern and may pose as risk to public health.
TABLE OF CONTENTS
Cover ……………………………………………………………………………. i Fly leaf ………………………………………………………………………….. ii Title …………………………………………………………………………….. iii Declaration ………………………………………………………………………. iv Certification …………………………………………………………………….. v Acknowledgement ………………………………………………………………. vi Abstract …………………………………………………………………………… vii Table of Content ………………………………………………………………… viii List of Figures ……………………………………………………………………… ix List of Tables …………………………………………………………………….. x List of Appendices ……………………………………………………………….. xi Abbreviations ……………………………………………………………………. xii CHAPTER ONE 1 1.0 INTRODUCTION ……………………………………………………… 1 1.1 Background ……………………………………………………………. 1 1.2 Heavy Metals and Human Health ……………………………………… 12 1.3 Routes of Heavy Metal Exposure ………………………………………… 14 1.4 Hazardous Effects of Heavy Metal on Human Health ……………… 15 1.5 Statement of the Problem …………………………………………………… 15 1.6 Justification of Study ………………………………………………… 18 1.7 Research Hypothesis ………………………………………………… 20 1.8 Research Aim and Specific Objectives …………………………………… 20 1.9 Research Limitations ………………………………………………………… 21 CHAPTER TWO 2.0 LITERATURE REVIEW ………………………………………………… 22 2.1 Selected Heavy Metals ……………………………………………………… 22 2.1.1 Zinc ……………………………………………………………………… 22 2.1.2 Copper ……………………………………………………………………. 23
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2.1.3 Nickel ……………………………………………………………………… 24 2.1.4 Lead ……………………………………………………………………… 25 2.1.5 Arsenic ……………………………………………………………………. 29 2.2 Heavy Metal Toxicity …………………………………………………… 33 2.3 Sources of Heavy Metal Contamination…………………………………… 34 2.3.1 Heavy metal in water ……………………………………………………… 34 2.3.2 Heavy metal in soil ……………………………………………………… 38 2.3.3 Heavy metal in fodder ……………………………………………………… 40 2.3.4 Heavy metal in air …………………………………………………………… 43 2.3.5 Animal manure ……………………………………………………………… 43 2.4 Mechanism of Action of Heavy Metals ……………………………………… 44 2.5 Management of Heavy Metal Poisoning ……………………………………. 44 CHAPTER THREE 46 3.0 MATERIALS AND METHODS ………………………………………….. 46 3.1 Materials …………………………………………………………………… 46 3.1.1 Compound fish feeds ………………………………………………………… 46 3.1.2 Compound poultry feeds ……………………………………………………. 46 3.1.3 Feedstuffs for cattle ………………………………………………………… 47 3.2 Reagents …………………………………………………………………… 47 3.3. Equipment ………………………………………………………………….. 47 3.4 Methods ……………………………………………………………… 48 3.4.1 Study area ………………………………………………………………… 48 3.4.2 Sample collection …………………………………………………………… 58 3.3 Sample Preparation …………………………………………………………….. 59
3.3.1 Feeds and manure samples …………………………………………………….. 59
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3.3.2 Water samples ………………………………………………………………… 59 3.4 Analytical Method ……………………………………………………………… 60 3.4.1 Procedure …………………………………………………………………….. 60 3.4.2 Calibration curves …………………………………………………………… 60 3.4.3 Method validation …………………………………………………………… 60 CHAPTER FOUR 63 4.0 RESULTS …………………………………………………………………… 63 4.1 Method Validation …………………………………………………………… 63 4.2 Fish Feeds …………………………………………………………………… 64 4.3 Poultry Feeds …………………………………………………………… 70 4.4 Pasture Grasses ……………………………………………………………… 76 4.5 Animal Manure ……………………………………………………………… 82 4.6 Water Samples ………………………………………………………… 88 CHAPTER FIVE 95 5.0 DISCUSSION …………………………………………………………… 95 5.1 Method Validation …………………………………………………………… 95 5.2 Livestock Feeds ……………………………………………………………… 95 5.3 Animal Manure ……………………………………………………………… 98 5.4 Water Samples …………………………………………………………… 100
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CHAPTER SIX 102 6.0 SUMMARY, CONCLUSSION AND RECOMMENDATION…………… 102 6.1 Summary ……………………………………………………………………. 102 6.2 Conclusion ………………………………………………………………….. 102 6.3. Recommendations ………………………………………………………. 103
CHAPTER ONE
INTRODUCTION 1.1 Background
Environmental problems are becoming global issues because of their effects on all nations of the world. These are present day major interests of political, economic, social and environmental concerns because of their potential negative impacts to our lives and the ecosystem in general (Costa, 2000). Environmental pollution is a major global problem posing serious risk to man and animals. From 1900 to 2000 have seen an increase in global concern over the public health impacts attributed to environmental pollution, in particular, the global burden of disease United Nations Development Project (UNDP, 2010). The development of modern technology and the rapid industrialization are among the foremost factors for environmental pollution. The environmental pollutants are spread through different channels, many of which finally enter into food chain of livestock and man (Kaplan et al., 2010). There is increasing concern about environmental pollutants emanating from the livestock production systems (Kaplan et al., 2010). Pollution of the environment has significant impact on living organisms. Various anthropogenic activities such as burning of fossil fuel, mining and metallurgy, industries and transport sectors redistribute toxic heavy metals into the environment, which persist for a considerably longer period and are translocated to different components in environment affecting the biota (Kaplan et al., 2010). These toxicants are accumulated in the vital organs including liver and kidney and exert adverse effects on domestic and wild populations (Khan et al., 2012). The effluents from livestock systems can affect the micro and macro environment, viz., water, atmosphere and
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food chain. Heavy metals or trace elements are a large group of elements with higher density generally greater than 5 gm/cm3. These elements are important both industrially and biologically. Heavy metals occur naturally in earth‟s crust and surface soils in varying concentrations. Natural Processes like weathering, erosion remove small amounts of metals from the bed rocks and allow them to circulate in water and air. Heavy metals like Zn, Se, Cu, and Fe are essential to maintain the metabolism of the human body and play important role in chemical, biological, biochemical and enzymatic reactions in the cells of plants, animals and human beings. Heavy metals are also known as „trace inorganic‟ micronutrients‟, „toxic elements‟ etc. More than 60 elements in various parts of human body have been detected, but only 17 are available in living cells.
Heavy metals like Mn, Mo, Fe are more important as micronutrients while Ni, Cu, Co, V, Zn, W and Cr are of lower importance and can be toxic beyond the limits (Duruibe et al., 2007). Heavy metals like Cd, Pb, Mg, As, Sb, have no biological functions, but are rather toxic to living organisms (Duruibe et al., 2007). Injury to human caused by heavy metals has been well recognized in many botanical and chemical investigations during past years. Heavy metals occur in all ecosystems of the world. The total concentration of heavy metals in soil and water however varies from local to regional and further to continental level. Heavy metals are very harmful in reference to their non biodegradable nature, long biological half lives and their potential to accumulate in different body parts. Most of the heavy metals are extremely toxic. Even at low concentrations heavy metals can have damaging effects in human beings and animals as there is no good mechanism for their elimination from the body. The heavy metals are taken up faster than they are metabolized or excreted. Even those
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heavy metals which are considered to be essential can become toxic when present in excessively high levels (Gabriel et al., 2007).
The heavy metals can impair important biochemical processes posing a threat to human health (UNDP, 2010). As the usage of metals increased inexorably, so did the pollution associated with it. Changes in the environment due to anthropogenic activities may have strong impact on the physiology and ecology of the organisms. Human activities and consequent developments have brought about degradation of all facets of the natural environment; physical, chemical, biological and social which are adversely affecting the quality of life (Morison, 2011). Rapid developments, increase in mining, industrial activities, have gradually redistributed many of the toxic metals from the earth crust to the environment, raising the chances of exposure through ingestion, inhalation or on skin contact. Heavy metals can have different sources or origin e.g. smelters, tannery, mines, steel mills, coal fired power plants which can lead to metal pollution. Other sources of metal pollution are sewage sludge, compost refuse, fly ash, industrial wastes or effluents. Emission of heavy metals as particulate matter and gases from volcanoes, forest fires, crusted materials and continental dust have always been a natural input sources to soils and ecosystems. The spreading of urban waste and sewage sludge in agricultural fields has been a common practice since decades. Sewage sludge, live stock manure, waste water irrigation are feasible alternatives for reutilization of residual resource of high nutrient and organic matter contents representing a good fertilizer or soil conditioner for plants and soil (Singh et al., 2012). Cattle and poultry manure generally contains elevated concentrations of Cu and Zn which improve food conversion efficiency. Arsenic was also used for this purpose (Giacomino et al., 2007). Beneficial properties of sludge and manures are limited by their contents of potentially harmful substances such as heavy metals and organic micro pollutants (Nicholson et al., 2000).
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Sludge and manure Atmospheric emissions are also a matter of great concern. Leaded gasoline in vehicles is one of the major sources of Pb pollution in the cities worldwide (Azeez et al., 2012). Ramadan (2007) reported that only 3% of Pb in the soil is translocated through roots to the shoots and fruits, rest are due to absorption through foliage. Sources like engine oils, corrosion of batteries, wear and tear of tyres, vehicular parts contribute for Cu, Pb and so on (Duruib et al., 2007). Moreover bitumen, mineral filler materials in asphalt road surfaces has also been reported to contain metals like Cu, Zn, Cd and Pb (Haque et al., 2005). It is not completely possible to avoid exposure to toxic metals because people who are not occupationally exposed carry certain heavy metals into their body due to food, beverages or inhalation of air. It is however possible to reduce metal toxicity risk through life style choices that diminish the probability of harmful heavy metals uptake such as dietary measures that may promote safe metabolism or excretion of ingested heavy metals. Food chain contamination by heavy metals has become a blazing issue in recent years because of their accumulation in the bio-system through contaminated water, soil and air. Fertilizers may be responsible for heavy metal addition in very small amounts however on the other hand sewage sludge may add them 100 times more in short duration (Cang et al., 2012). Toxic metals in the atmosphere also get accumulated in soils through precipitation and fallout. Availability of heavy metals to plants is due to mining activities, industrial exhausts and effluents, atmospheric depositions, waste disposals, agro-chemicals. However availability of heavy metals to plants depends on various physicochemical properties of soil. Metal toxicity in plants is aggravated at higher temperature and low pH as it facilitates the mobility from roots to shoots. Therefore a better understanding of heavy metal sources, their accumulation in Soil and water and their effect on the ecosystem is an important issue of the present day researches or risk assessment (Abulude et al., 2000).The
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heavy metals which are a great threat to the environment and the biosphere as a whole are being derived from various anthropogenic sources. The heavy metals are biopersistent, once absorbed by an organism, may remain resident for years or over decades. In humans, most eventually excreted but on exposure causes various ailments. It may disturb the normal functions of central nervous system, liver, lungs, heart, kidney and brain; it produces hypertension, abdominal pain, skin eruption, intestinal ulcer & different types of cancer (Arogunjo et al., 2006).To protect public health, Nigerian government has developed guidelines as well as regulations that can be enforced by laws. Many agencies that have developed regulations for toxic substances include the United States Environmental Protection Agency (EPA), and Food and Drug Administration (FDA). Federal organizations that develop guide lines or recommendations for toxic substances include the National Agency for Foods, Drugs, Administration and Control (NAFDAC). Earlier studies by researchers have inferred that rapid urbanization, increased transportation, industrial revolution have posed a serious threat to the environment (Menzi and Kessler, 2001). Among other heavy metals, Pb and Cd have more hazardous effects on the environment and have widely polluted the urban agricultural lands (Menzi and Kessler, 2001). Thus it has been recommended earlier as well as from recent studies that leafy vegetables should be grown at least 30 m away from roads having high traffic. Studies revealed that plants accumulated small amount of Pb when the density of traffic was about 5000 vehicles per day, but there was a substantial increase in absorption of Pb when it reached to approx 35,000 vehicles per day (Menzi and Kessler, 2001).
Heavy metals like Fe, Cu, Zn, Ni and other trace elements are important for proper biological functions. However, their deficiency or excess may cause a number of disorders (Akan et al., 2010). Prolonged consumption of food stuffs having higher concentration of heavy metals may
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result in various types of problems, disruption of numerous biochemical processes leading to cardiovascular, nervous, renal, kidney, liver and bone diseases (Akan et al., 2010). Under EPA regulations, public drinking water supplies are expected not to exceed 5 ppb of Cadmium (Cd) in it. EPA also restricts the use of Cd in pesticides, so that they are not washed off into lakes, rivers, reservoirs, agricultural lands. Different techniques were used by different researchers to determine heavy metal contents including modern analytical techniques such as AAS and ICP-AES. However, there was no established quantitative method for determining directly the exact or fractional amount of metals that are bio-available to plants. Many factors such as variation in pH, temperature, nature of soil, redox condition, plant species, maturity or plant age play important role in the uptake of heavy metals (Menzi and Kessler, 2001). Climate change is characterized by increased frequency and intensity of extreme weather patterns including storms, floods, droughts and irregular rain over time (FAO, 2006). Nigeria‟s population has doubled in the past quarter of a century to 200 million, thus putting greater strain on natural resources (Uba et al., 2013). The infrastructure is still poor and the means of agricultural production and marketing remain the same. The agricultural sector in Nigeria contributes 50% to the Gross Domestic Product (GDP) and is a way of life for 85% of the population according to 2011 census).The major land uses in Nigeria are livestock grazing and crop production causing depleted natural conservation in forests and woodlands. According to Bioresource development and conservative programme (BDCP) in 2001, more than 50% of Nigeria‟s land is used for livestock grazing. Grazing occurs mainly in open grasslands, around cultivated areas, shrub lands, road sides and wetlands. Crop production forms the second largest (± 23%) land use while forests and woodlands cover about 7% of the country. Bare lands constitute 16% in the form of exposed rock, salt flats and sand dunes.
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According to Food and Agricultural Organisation (FAO, 2012) the population of livestock in Nigeria in 2012 was estimated at 50.9 million Chicks, 26 million cattle and 22 million goats; that is a total of 108 million heads, which is ranked the largest in West Africa and the 10th in the world. About 95% of the livestock population is kept by subsistence farmers. It forms a large component of the Nigerian agricultural sector and is well integrated with the crop production systems in the highlands and provides the sole means of subsistence for the nomadic pastoralists in the lowlands. It is the source of many social and economic values such as food, draught power, fuel, cash income, security and investment in both the highlands and the lowlands/pastoral systems (Haque et al., 2005). Livestock production accounts for 27% of total agricultural GDP. Livestock is a key development sector because it involves the livelihoods of the poor as much as it is the source of animal protein for the emerging middle class who consume 5 increasing amounts of meat, milk and eggs. Thus livestock serves the interest of both the poor and the middle class (FAO, 2012). However, the livestock sector has also been identified as one of the top two or three most significant contributors of the most serious environmental problems from local to global scale (FAO, 2012). The sector has gradually evolved to become an environmental threat to the survival of ecosystems. The danger of to the environment varies according to whether the country is developed and developing as wells as to the type of production systems. Food safety is a major public concern worldwide. During the last decades, the increasing demand of food safety has stimulated research regarding the risk associated with consumption of food stuffs contaminated by pesticides, heavy metals and/or toxins (Igwebe, 2013). The implication associated with heavy metal contamination is of great concern. Heavy metals, in general are not biodegradable, having long biological half-lives and
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having the potential for accumulation in the different body organs leading to unwanted side effects (Mamud et al., 2004). As developing countries of’ West African become industrialized and urbanized, heavy metal pollution is likely to reach disturbing levels, It has been pointed out that African’ s contribution to global lead pollution has increased from just 5% in 1980’s to 20% in 1996 (WHO, 1996). The critical issues however are that preparations are not being made towards the protection of the environment. Excessive levels of heavy metals may occur in the biosphere as a result of normal geological phenomena such as ore formation, weathering of rocks and leaching. Other activities that could contribute to excessive release of these metals into the environment include burning of fossil fuels, smelling, and discharges of industrial, agricultural and domestic wastes as well as deliberate application of pesticides. Coastal areas are sites of discharge and accumulation of a range of environmental contaminants. Studies on heavy metals in rivers, lakes, fish and sediments have been a major environmental focus especially during the last decade (Ikem et al., 2012). Heavy metals contamination of coastal water and sediment has been identified as a serious pollution resulting from industrialization (Ramos et al., 2000). Heavy metals contamination of river water is one of the major quality issues in fast growing cities because maintenance of water quality and sanitation infrastructure do not increase along with population and urbanization growth especially in developing countries. There are five major sources of heavy metals namely geological weathering through natural phenomenon, industrial processing of ore and metals, the disposal of metals and metal components, leaching of metals from garbage and solid waste heaps and animal and human excretions. The single largest source of heavy metals in most coastal ecosystems in the United States is residential waste water effluents (Ramos et al., 2000).
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Over the last few decades, there has been growing interest in determining heavy metal levels in the marine environment and attention was drawn to the measurement of contamination levels in public food supplied, particularly fish. Although heavy metal is a loosely defined term, it is widely recognized and usually applied to the wide spread contaminants of terrestrial and fresh water ecosystems. Some examples of heavy metal include lead, zinc, cadmium, copper and manganese. Many of these heavy metals are toxic to organisms at low concentration (Ramos et al., 2000).
The concentration of metals in bio-available form is not necessarily proportional to the total concentration of the metal. The concentration of various elements in the air, water and land may be increased beyond their natural level due to the agricultural, domestic and industrial effluents. These substances are described as “contaminants” when discharged to the environment (Dike et al., 2004). In water, insoluble heavy metals may be bound to small silt particles. Metals and other fluvial contaminants in suspension or solution, do simply flow down the stream, they form complexes with other compounds settle to the bottom and ingested by plants and animals or adsorbed to sediments (Dike et al., 2004). Consequently, aquatic organisms may acquire heavy metals in body directly from the water via gills or food chain mechanisms. Water, a prime need for human survival and industrial development is being affected by various activities of man which alters its composition physically, chemically or biologically. Pollution of coastal waters by heavy metals has been widely reported (Oduemeran, 2005). Sources of pollution by trace metals include atmospheric release from fossil fuels burning domestic sewage discharge, land run-off and release from industrial operations such as mining, canning and electroplating (Akan et al., 2010). With increased diversification in industrialization and particularly with the extensive
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farming activities in Northern Nigeria, especially in the urban areas, the concentration of metal pollutants in the ecosystem has risen (Akan et al., 2010). Northern Nigeria lies between 10‟ North latitude and 8‟ South longitude with a total area 660,000 square kilometers. The main rivers are Niger and Benue Rivers which converge at Kabba province and empty into the Atlantic ocean. The expansive valleys of the Niger and Benue River valleys dominate the Northern areas of the country. To the southeast of the Niger and Benue Rivers, hills and mountains which form the Mambilla Plateau create the highest Plateau in Northern Nigeria. This plateau extends to the border with Cameroon, this montane land forms part of the Bamenda Highlands in Cameroon. The Great savannah belt of the Great Plains of Hausa land dominates much of the rest of the country. This region experiences rainfall between 20 and 60 inches (508 and 1,524 mm) per year. The savannah zone’s three categories are Guinean forest-savanna mosaic, Sudan savannah, and Sahel savannah. Guinean forest-savanna mosaic is plains of tall grass which are interrupted by trees. Sudan savannah is similar but with shorter grasses and shorter trees. Sahel savannah consists of patches of grass and sand, found in the northeast. In the Sahel region, rain is less than 20 inches (508 mm) per year and the Sahara Desert is encroaching. In the dry north-east corner of the country lies Lake Chad, which Northern Nigeria shares with Niger, Chad and Cameroon. Thus much of Nigeria and the region to the west experiences two rainy periods as the inter tropical convergence move north or south; but in the north the two rainy seasons merge to give a single wet season between July and September. The major rivers are rivers Niger and Benue with confluence at Lokoja, North central Nigeria (Arogunjo, 2006).
According to 1991 census total population of Northern Nigeria is put at about 86,950,491 covering 62% of Nigeria total land mass. The main occupation of the populace is fishing and
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farming. There is object poverty and illiteracy among the people. In the desire to make quick money for survival out of anything available mining activities of abundant natural resources especially Gold is being embark upon by communities without any regard for environmental implications. There are well known industrial cities having big commercial centers along with hundreds of small scale industries. The old cities being comparatively congested due to search for better livelihood is favored by economically weaker sections of the society and most of the people of these sections are unresponsive to the environmental quality. The climate of Northern Nigeria is characterized with a long and intense hot summer, medium rainfall and a short mild winter. The temperature normally varies from 32 – 48oC in April/May to 18 – 30 ºC in July/August. The hot weather usually extends from the beginning of March to the end of June. The area is agriculturally rich, and use of fertilizers, insecticides and pesticides is common. In northern Nigeria highlands, negative livestock-environment interaction impacts are mainly associated with overgrazing and use of organic fertilizer from animal dung (Webber et al., 2004). Overgrazing causes chemical and physical soil degradation which reduces infiltration and increases run-off into our rivers and streams. Moreover, socio-economic changes in the rural areas such as population growth, has forced people to turn to cultivating crops with increasing use of organic fertilizer (FAO, 2006). Livestock play an important role as a source of power for crop production and manure as organic fertilizer (Webber et al., 2004). However, no detail study has so far been done on the contribution of manure as a source of environmental heavy metal pollution. The shift in the use of manure as a fertilizer to a source of soil manure became evident very recently, because of continuous deforestation for firewood and increased level of poverty in the rural areas that compelled farmers to use animal farm manure in place of modern chemical fertilizers (Gabriel et al., 2007).
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The vast majority of small-scale farmers in northern Nigeria highlands are into nutrient recycling through manure, to compensate for lack of access to chemical fertilizer (Konegay et al. 1976). The traditional practice of adding manure to the soil and allowing crop residues to decay in the fields has also dropped due to use of animal dung (Konegay et al., 1976). Nutrients and heavy metals are moved from the soil through plant root systems, transported to plants tissues and leaves being consumed as vegetable, exported in the form of grain and straw. Therefore, organic matter and metal content in the soil is increasing fast. Farmers rely on organic fertilizer from animal feaces to meet crop needs for nutrients over short term, but over the long-term large off-farm fertilizer inputs would be required to maintain soil nutrient balance and crop yields. The current prices of commercial fertilizer are beyond the reach of resource-poor farmers, which will force some farmers to drop the use of chemical fertilizers (Endale, 2014). 1.2 Heavy Metals and Human Health
Strictly speaking, heavy metals are defined as those with higher density than 5 mg ml-1 (Duda, 2008) but the collective term now includes arsenic, cadmium, chromium, copper, lead, nickel, molybdenum, vanadium and zinc. Some interest also exists in aluminium, cobalt, strontium and other rare metals (Ihedioha and Okoye, 2012). A heavy metal is not toxic per se and it is only toxic when its concentration in the plant and animal exceeds a certain threshold (it is the dose that makes the effect). Some elements, called trace elements or micronutrients, have essential functions in plant and animal cells. This has been shown for Co, Cu, Fe, Mn, Mo, Ni and Zn. Only when the internal concentration exceeds a certain threshold do they demonstrate toxic effects, and then they are commonly termed “heavy metals.” Studies of heavy metal in water, sediments and plants carried out in Sosiani River, Uasin Gishu County, Kenya reveal that the plants found in the study area showed a preferential zinc metal uptake and may lead to
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accumulation in exposed plants posing Zn exposure risks along the food chain (Duda et al, 2008). The same study showed that the site near the Moi Teaching and Referral Hospital (MTRH) Uasin Gishu County in Kenya had the highest total heavy metals concentrations in water : Cu (0.18 ppm); Pb (0.46 ppm) and Zn (0.70 ppm) and sediments: Cu (1.62 ppm); Pb (1.27 ppm) and Zn (6.73 ppm) respectively. Other studies carried out to monitor exposure to heavy metals among children in Lake Victoria reported significant correlations between Pb, Cd and Cu in hair, nails and heavy metals from fish consumed. The study suggested fish consumption as a possible pathway of heavy metals in humans and possible health risks from heavy metals toxicity. This was due to consumption of higher quantities of fish from the geological basins. Concentration of Pb and Cu in water reflected anthropogenic pathways; while Cd and Cr reflected accumulation from the catchment basin (Ogabiola et al., 2013) reported that there was evidence of bioaccumulation of heavy metals in the fish. The study also showed that the concentrations of heavy metal found in the water from the Athi River tributaries and gills of the tilapia fish examined was higher than the WHO limits, therefore posing potential risk for inhabitants that depended on the river (Eddy et al., 2006). 1.3 Routes of Heavy Metal Exposure
Heavy metals enter the human body mainly through two routes which are inhalation and ingestion. Ingestion is the main route of exposure to these elements in human population (Cui et al., 2007). Absorption through the skin is another route of exposure when the metals come in contact with humans in agriculture and in manufacturing, pharmaceutical, industrial, or residential settings. Industrial exposure accounts for a common route of exposure for adults (Dimerizen, 2006). Ingestion is the most common route of exposure in children. Children may acquire toxic levels from the normal hand-to-mouth activity with contaminated soil or by
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actually eating objects that are not food (Uba et al., 2013). Exposure to toxic heavy metals is generally classified as acute, 14 days or less; intermediate, 15-354 days; and chronic, more than 365 days. Chronic low level intakes of heavy metals have adverse effects on human beings and other animals due to the fact that there is no effective mechanism for their elimination from the body (Fatoki, 2000). Metals such as lead, mercury, cadmium and copper are cumulative poisons. These metals cause environmental hazards and are reported to be exceptionally toxic (Finster et al., 2004). Additionally, acute toxicity is usually from a sudden or unexpected exposure to a high level of the heavy metal. Chronic toxicity results from repeated or continuous exposure, leading to an accumulation of the toxic substance in the body. Chronic exposure may result from contaminated food, air, water, or dust; living near a hazardous waste site; spending time in areas with deteriorating lead paint; maternal transfer in the womb; or from participating in hobbies that use lead paint or solder. Chronic exposure may occur in either at home or workplace. Symptoms of chronic toxicity are often similar to many common conditions and may not be readily recognized (Miranda et al., 2005). Chronic accumulation of heavy metals in the kidney and liver of humans causes disruption of numerous biochemical processes, leading to cardiovascular, nervous, kidney and bone diseases. Furthermore, the consumption of heavy metal-contaminated food can seriously deplete some essential nutrients in the body causing a decrease in immunological defenses, intrauterine growth retardation, impaired psycho- social behaviour, disabilities associated with malnutrition and a high prevalence of upper gastrointestinal cancer (Garcia et al., 2007). 1.4 Hazardous Effects of Heavy Metals on Human Health
Food safety issues and potential adverse health risks made metal consumptions one of the most serious environmental concerns (Bakare-Odunola, 2005). Mercury and lead are associated with
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the development of abnormalities in children (Finster et al., 2004) also reported that long term intake of cadmium causes renal, prostate and ovarian cancers. Generally, at the biochemical levels, the toxic effects caused by excess concentrations of heavy metals include competition for sites with essential metabolites, replacement of essential ions, reactions with –SH groups, damage to cell membranes and reactions with the phosphates groups (Finster et al., 2004). 1.5 Statement of Research Problem Environmental pollution is one of the problems that pose serious health threats to animals and humans worldwide. Metals and metalloids tend to bioaccumulate in the environment and biomagnified in food chains where their levels might reach toxic limits even when found in low concentrations in environmental samples (Caggiano et al., 2004). Therefore monitoring the levels of heavy metals in the food chain is of great importance for the well being of all life forms. The traditional system of management of livestock, free ranging, which involves animals taken from place to place in search for water and pasture, has remained the most practiced in the country. Free ranged animals can pick toxicants such as heavy metals from the environment by feeding on fodder in the open or from waste dumps, drinking polluted water from drains and streams, and intake of atmospheric depositions especially from vehicular emission and fumes from open burning of wastes (Ihedioha and Okoye, 2012). The water sources in northern Nigeria also get contaminated with the heavy metals as a result of leaching and from rain water which drains into them. This water is then used for irrigating crops around and domestic use including drinking and may directly cause heavy metal poisoning to the consumer.
Animal manure is applied to agricultural land to improve the soil fertility and organic matter content. However, this practice also results in serious environmental problems, such as heavy
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metal contamination of surface waters through runoff and also promotes metal migration through leaching to the underground waters. Another important problem induced by animal manure application is metal pollution as residues of heavy metals in manure can be accumulated in surface soils as a result of long-term agricultural use and in plants through uptake in crops and being primary producers contaminate the eco system. The metals present in animal manure are largely derived from feeds. 1.5 Justification of the study
Nigeria as a developing country, currently depend on fish and livestock for her primary source of protein but animal feed supplies also have to cope with increasing safety concerns, optimized by contaminations from chemicals e.g. heavy metals. In Northern Nigeria, the farming communities contribute about imminent environmental contaminations and the likely impacts on our livelihoods. There is the need for people and government bodies to be aware of the consequences of our activities and the need to safeguard health. There has been indiscriminate local gold mining activities in North central and Northwest Nigerian communities by the inhabitants evident in 2010 Medecins Sans Frontieres (MSF) discovery of an epidemic of lead poisoning in Zamfara state in North–Western Nigeria particularly in Anka and Bukkuyum Local Government Areas of the state (MSF, 2010). Subsequent investigations by the Centers for Disease Control (CDC), the World Health Organization (WHO) and the Zamfara State Ministry of Health (ZMoH) confirmed that hundreds of children under ages of five were at risk of death or serious acute and chronic health effects due to extremely high levels of lead and mercury (WHO, 2011). At least 10,000 people were estimated to be affected overall (MSF, 2010). The source of the
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outbreak was associated with artisanal gold ore processing that occurs in the villages (Udiba et al., 2013). The medium through which the people were affected include drinking water, food, and inhalation of contaminated dust, oral ingestion of particles especially by children and through breast feeding. Mining of gold has being left in the hands of artisanal miners who do not have enough resources and adequate equipment and technology required for the mining activities. Many of these communities make their living from subsistence farming, growing food from the surroundings, and obtaining drinking water from nearby surface and sub-surface water sources. Farming is the main occupation of Northern populace primarily due to poverty leading to extensive use of animal manure on farm lands which is the major route of heavy metal inputs to agricultural soils. Expansion of processing industries, farms and abattoirs produce chemical discharge into the soil and water bodies that are used by livestock and people. These animals when exposed to toxic metals accumulate them in their tissues and organs which are considered delicacies in Nigeria. Meat produced from these animals is considered rich and convenient source of nutrients such as proteins and micronutrients and consumption of these contaminated meat may pose public trait to human health. Despite the high concentrations of heavy metals in some environmental samples from Nigeria, no precise studies to the best of my knowledge have been conducted to determine metal contamination levels in animal feeds for fish, poultry and cattle and from major rivers as the source of drinking water in Northern part of the country. 1.7 Research Hypothesis The levels of heavy metal concentration in livestock feeds, manure and rivers and streams in Northern Nigeria have reached detrimental levels to animals and human. 1.8 Aim of research
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The aim of this study was to determine the level of some heavy metals (Zn, Cu, Ni, Pb and As) in fish and livestock feeds, animal manure and rivers in selected states in northern Nigeria. 1.8.1 Specific objectives of the study The objectives of this study were: 1. Adopt and validate atomic absorption spectrometric method for determination of heavy metals via percentage extraction recovery and precision of the method adopted. 2. Determine the heavy metal concentrations in compound fish and livestock feeds in selected states in northern Nigeria. 3. Determine the heavy metal concentrations in major rivers in selected states in northern Nigeria 4. Assess the heavy metal concentrations in poultry and cattle manures in selected states in northern Nigeria 5. Compare all the heavy metals concentrations determined in fish and livestock feeds, manures and rivers within the selected states of northern Nigeria 1.9 Research Limitations The forage grasses collected for sampling excludes those identified as poisonous to the ruminants that are not palatable or grazed by the cattle. These include lupine (Lupinus spp), death camas (Amsinckia intermedia), nightshades (Solanum spp), poison hemlock (Apocynum spp), water hemlock (Aconitum spp) and larkspurs (Asclepias spp). It is critical that overgrazing pastures that contain these plants are avoided to prevent livestock toxicity and the right pastures that are being grazed by the animals are analyzed.
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