HEAVY METALS DETERMINATION IN SOME SELECTED DUMP SITE AREA IN BAJOGA TOWN OF FUNAKAYE

1.0 BACKGROUND
Heavy metals are defined as metallic elements that have a relatively high density compared to water. With the assumption that heaviness and toxicity are inter-related, heavy metals also include metalloids, such as arsenic, that are able to induce toxicity at low level of exposure. In recent years, there has been an increasing ecological and global public health concern associated with environmental contamination by these metals. Also, human exposure has risen dramatically as a result of an exponential increase of their use in several industrial, agricultural, domestic and technological applications. Reported sources of heavy metals in the environment include geogenic, industrial, agricultural, pharmaceutical, domestic effluents, and atmospheric sources. Environmental pollution is very prominent in point source areas such as mining, foundries and smelters, and other metal-based industrial operations (Ogwueleka, 2003). Although heavy metals are naturally occurring elements that are found throughout the earth’s crust, most environmental contamination and human exposure result from anthropogenic activities such as mining and smelting operations, industrial production and use, and domestic and agricultural use of metals and metal-containing compounds. Environmental contamination can also occur through metal corrosion, atmospheric deposition, soil erosion of metal ions and leaching of heavy metals, sediment re-suspension and metal evaporation from water resources to soil and ground water. Natural phenomena such as weathering and volcanic eruptions have

also been reported to significantly contribute to heavy metal pollution. Industrial sources include metal processing in refineries, coal burning in power plants, petroleum combustion, nuclear power stations and high tension lines, plastics, textiles, microelectronics, wood preservation and paper processing plants (Dara, 1993).
It has been reported that metals such as cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se) and zinc (Zn) are essential nutrients that are required for various biochemical and physiological functions. Inadequate supply of these micro-nutrients results in a variety of deficiency diseases or syndromes (Nwajei et al., 2007) .
Heavy metals are also considered as trace elements because of their presence in trace concentrations (ppb range to less than 10ppm) in various environmental matrices]. Their bioavailability is influenced by physical factors such as temperature, phase association, adsorption and sequestration. It is also affected by chemical factors that influence speciation at thermodynamic equilibrium, complexation kinetics, lipid solubility and octanol/water partition coefficients. Biological factors such as species characteristics, trophic interactions, and biochemical/physiological adaptation, also play an important role (Dara, 1993).
The essential heavy metals exert biochemical and physiological functions in plants and animals. They are important constituents of several key enzymes and play important roles in various oxidation-reduction reactions. Copper for example serves as an essential co-factor for several oxidative stress-related enzymes including catalase, superoxide dismutase, peroxidase, cytochrome c oxidases, ferroxidases, monoamine oxidase, and dopamine β-monooxygenase (Osuj & Onojake, 2004). Hence, it is an essential nutrient that is incorporated into a number of metalloenzymes involved in hemoglobin formation, carbohydrate metabolism, catecholamine biosynthesis, and cross-linking of collagen, elastin, and hair keratin. The ability of copper to cycle between an oxidized state, Cu(II), and reduced state, Cu(I), is used by cuproenzymes involved in redox reactions. However, it is this property of copper that also makes it potentially toxic because the transitions between Cu(II) and Cu(I) can result in the generation of superoxide and hydroxyl radicals. Also, excessive exposure to copper has been linked to cellular damage leading to Wilson disease in humans. Similar to copper, several other essential elements are required for biologic functioning, however, an excess amount of such metals produces cellular and tissue damage leading to a variety of adverse effects and human diseases. For some including chromium and copper, there is a very narrow range of concentrations between beneficial and toxic effects. Other metals such as aluminium (Al), antinomy (Sb), arsenic (As), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), gallium (Ga), germanium (Ge), gold (Au), indium (In), lead (Pb), lithium (Li), mercury (Hg), nickel (Ni), platinum (Pt), silver (Ag), strontium (Sr), tellurium (Te), thallium (Tl), tin (Sn), titanium (Ti), vanadium (V) and uranium (U) have no established biological functions and are considered as non-essential metals (Fytianos etal., 2001).
In biological systems, heavy metals have been reported to affect cellular organelles and components such as cell membrane, mitochondrial, lysosome, endoplasmic reticulum, nuclei, and some enzymes involved in metabolism, detoxification, and damage repair. Metal ions have been found to interact with cell components such as DNA and nuclear proteins, causing DNA damage and conformational changes that may lead to cell cycle modulation, carcinogenesis or apoptosis. Several studies from our laboratory have demonstrated that reactive oxygen species (ROS) production and oxidative stress play a key role in the toxicity and carcinogenicity of metals such as arsenic, cadmium, chromium, lead, and mercury. Because of their high degree of toxicity, these five elements rank among the priority metals that are of great public health significance. They are all systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. According to the United States Environmental Protection Agency (U.S. EPA), and the International Agency for Research on Cancer (IARC), these metals are also classified as either “known” or “probable” human carcinogens based on epidemiological and experimental studies showing an association between exposure and cancer incidence in humans and animals (Fytianos etal., 2001).
Heavy metal-induced toxicity and carcinogenicity involves many mechanistic aspects, some of which are not clearly elucidated or understood. However, each metal is known to have unique features and physic-chemical properties that confer to its specific toxicological mechanisms of action. This review provides an analysis of the environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity of arsenic, cadmium, chromium, lead, and mercury (Ebong et al., 2008).
1.1 EFFECTS OF SOME HEAVY METALS
Heavy metals are toxic to soil, plants, aquatic life and human health if their concentration is high in the compost. Heavy metals exhibit toxic effects towards soil biota by affecting key microbial processes and decrease the number and activity of soil microorganisms. Even low concentration of heavy metals may inhibit the physiological metabolism of plant. Uptake of heavy metals by plants and subsequent accumulation along the food chain is a potential threat to animal and human health. Contaminants in aquatic systems, including heavy metals, stimulate the production of reactive oxygen species (ROS) that can damage fishes and other aquatic organisms. Hence the compost has to be use for agriculture it should be free from heavy metals. Therefore, the present study evaluated the effects of heavy metal containing compost on soil, plants, human health and aquatic life (Ebong et al., 2008).
1.2 SOURCES OF HEAVY METALS
Heavy metals are naturally present in our environment. They are present in the atmosphere, lithosphere, hydrosphere and biosphere. Although these heavy metals are present in the ecosystem, their exposure to humans is through various anthropogenic activities of man. In the earth crust, these heavy metals are present in ores which are recovered during mining activities as minerals. In most ores heavy metals such as arsenic, iron, lead, zinc, gold, nickel, silver and cobalt exist as sulfides while others such as manganese, aluminum, selenium gold, and antimony exist as oxides. Certain heavy metals such as copper, iron and cobalt can exist both as sulfide and oxide ores. Some sulfides may contain two or more heavy metals together such as chalcopyrite, (CuFeS2) which contains both copper and iron. During these mining activities, heavy metals are released from the ore and scattered in open in the environment; left in the soil, transported by air and water to other areas. Furthermore, when these heavy metals are used in the industries for various industrial purposes, some of these elements are released into the air during combustion or into the soil or water bodies as effluents. More so, the industrial products such as paints, cosmetics, pesticides, and herbicides also serve as sources of heavy metals. Heavy metals may be transported through erosion, run-off or acid rain to different locations on soils and water bodies (Ebong et al., 2008).
1.3 SOME SPECIFIC HEAVY METALS EFFECTS
1.3.1 CADMIUM (Cd)
Cadmium is a white shining but tarnish able metals similar in several characteristics to zinc and tin. Cadmium is not found to a great extend in nature its presence in the earth crust is estimated to a range between 0.15 to 0.11mg/g (67 elements in order of abundance), with a Zn/Cd ratio around 250:1 (the ratio depends strictly on the nature of rocks) (Nwajei et al., 2007).
Cadmium can be present as a results of volcanic emission and released from vegetation. It is not essential to plants growth, but under certain condition can accumulates in some plant to level that are hazardous to animal and human. Some sewage slugs contain enough cadmium to encourage accumulation. The chemistry of cadmium reaction in the soil is not well understood, but it is known that the uptake of these element is generally reduced by organic matter, silicate clay and hydro oxide or iron and aluminium when the soil is aerated. Cadmium uptake is high in excess. Soil and is reduced when soil is limits. This element has a wavelength of 228mm. it is a hazardous air pollutant which enter plants and animals from soil and water, thus cadmium has inhibitory effects on antioxidant processes, its interact with sulphide group of essential enzymes. Chronic exposure to cadmium is associated with a wide range of disease, including heart diseases, anaemia, skeletal weaken, depressed immune system responses. At extreme level it causes an illness called tai-‘’ital’’ disease characteristics by brittle bones and intense pain (Connell and miller 1984 )
1.3.2 CHROMIUM (Cr)
The most common forms of chromium are chromium (VI) and chromium (III) (Hilgenkamp, 2006). Although chromium toxicity in the environment is rare. It still presents some risks to human health since chromium can be accumulated on skin, lungs, muscle, fat, in liver, dorsal spin, hair, nails and placenta where it is traceable to various health conditions (Adeleken and Abegunde, 2011). The health effects brought about by the exposure to chromium (VI) include lung cancer, malignant neoplasia, chromium dermatitis and skin ulcers (Sarkar, 2005). Perforations and ulcerations of the nasal septum and bronchial asthma have also been reported. In one of the studies, a four-fold increase in childhood leukemia was attributed to possible consumption of water with chromium (VI) levels above standard recommended value of 300 mg/kg (Sarkar, 2005). The sources of chromium in the environment include, cement, leather, plastics, dyes, textiles, paints, printing ink, cutting oils, photographic materials, detergents, wood preservatives among others (Hilgenkamp, 2006). Other sources of chromium are power plants, liquid fuels, brown and hard coal and industrial and municipal wastes. Non biodegradability of chromium is responsible for its persistence in the environment and once mixed with soil, it undergoes transformation into various mobile forms before ending into environmental sink (Adeleken and Abegunde, 2011). The maximum allowable limit of chromium in the soil set by United Kingdom is 300 mg/kg (EU, 1986) while the limit set by FEPA (1991) is 0.03 mg/kg in Nigeria.
1.3.3 COPPER (Cu)Copper is an essential nutrient that is incorporated into a number of metalloenzymes involved in hemoglobin formation, drug/xenobiotic metabolism, carbohydrate metabolism, catecholamine biosynthesis, the crosslinking of collagen, elastin and hair keratin, and the antioxidant defense mechanism. Copper-dependent enzymes, such as cytochrome C oxidase, superoxide dismutase, ferroxidases, monoamine oxidase and dopamine β-monooxygenase, function to reduce activated oxygen species or molecular oxygen. Symptoms associated with copper deficiency in humans include normocytic, hypochromic anaemia, leukopenia, and osteoporosis (ATSDR, 2004).Although copper homeostasis plays an important role in the prevention of copper toxicity, exposure to excessive levels of copper can result in a number of adverse health effects including liver and kidney damage, anaemia, immunotoxicity and developmental toxicity. Many of these effects are consistent with oxidative damage to membranes or macromolecules. Copper can bind to the sulfhydryl groups of several enzymes, such as glucose-6-phosphatase and glutathione reductase, thus interfering with their protection of cells from free radical damage (ATSDR, 2004). A few examples of human activities that contribute to copper release are mining, metal production, wood production and phosphate fertilizer production. Because copper is released both naturally and through human activity, it is very widespread in the environment. The metal is often found near mines, industrial settings, landfills and waste disposals (Schult and Kelling, 1999)
1.3.4 ZINC (Zn)
Zinc was essentially established in 1869 for plants, in 1934 for experimental animals and in 1961 for human. Since the discovery of zinc deficiency as a human problem in 1961, interested in the biochemical and clinical aspects of zinc nutrition has increased markedly. In this paper, zinc is review in biochemical and physiological functions, metabolism including, absorption, excretion homeostasis, zinc bio availability (inhibitors and enhancers), human requirement, group at high-risk consequences and causes of zinc deficiency, evaluation of zinc status, and prevention strategies of zinc deficiency (Nazanin et al., 2013).
1.3.5 LEAD (Pb)
Lead is a soft heavy metallic element, it was one of the nine chemical elements known and used in the ancient world throughout history it has been widely employed in arts and architecture and in modern time, it has been used in making shield reaction. It is used as element in lead storage batteries, solder, plumbing, cable covering is also recognized. It is used in interior paints; it causes serious hazard because lead highly toxic if improperly handled (wajahat et’al 2006) lead in the solid is found into solution either by digesting it with hydrochloric acid solution. The extract is used to determine the element using atomic absorption spectroscopy (AAS) the element has a wavelength of 280mm (wajahat et’al 2006).
Lead can cause several health problems at relatively low level of exposure. It is found in organic form, inorganic leads affect typically the nervous system (CNS), peripheral nervous system (PNS), haematopoietic, renal, cardiovascular and reproductive system. Organic leads toxicity tends to predominantly affect the central nervous system. Inorganic lead enters the body by way of ingestion or inhalation, for adult only about 10% of the ingestion dose is absorbed in contrast, children may absorb as much as 50% of ingested dose. lead affect the production of blood cell, kidneys and behaviour it poses the placenta and can damage the foetal nervous system this disease of the nervous system can affect every aspect of reproduction in woman from fertility to lactation, and maternal neurologic disease and its treatment may have an impact on the offspring of that pregnancy. (Michael et al., 2008).
Lead (Pb) is a well-known neurotoxin. Impairment of neuro development in children is the most critical effect of lead poisoning. Exposure in the uterus, during breastfeeding and in early childhood may all be responsible for the effect. Lead accumulates in the skeleton and its transfer from bones during pregnancy and lactation causes exposure to foetuses and breastfed infants (ATSDR, 2007). Chronic exposure to Pb can affect physical growth and cause anaemia, kidney damage, headache, hearing problems, speaking problems, fatigue or irritable mood (Simeonov et al., 2010). The toxicity by Pb has multiple biochemical effects. It has the ability to inactivate enzymes, compete with calcium for incorporation into bones and interfere with nerve transmission and brain development (Ediin et al., 2000). It has been suggested that lead on a cellular and molecular level may permit or enhance carcinogenic events involved in DNA damage, DNA repair and regulation of tumour suppressor and promoter genes (Silbergeld, 2003).The common sources of lead are car batteries, tyre materials, coals, plastics and insecticides. The high level of Pb in soil, could be attributed to Pb from car exhaust fumes not lined nor basement prepared for selective adsorption of toxic substances. Therefore, it is prone to release pollutants to nearby water and to the air through leachates and dumpsite gases respectively (Alimba et al., 2006). Many water resources have been rendered wholesome and hazardous to man and other living systems, as a result of indiscriminate dumping of refuse (Bakare et al., 2005).Most uncontrolled dumps are many years old, having grown over time from small dumps to large, unmanaged waste sites. Uncontrolled dumps have significant environmental impacts. Solid waste poses the greatest threat to life since, it has the potential of polluting the terrestrial, aquatic and aerial environments (Odukoya et al., 2000). Soil samples represent an excellent media to monitor heavy metal pollution resulting from anthropogenic activities. Heavy metal contaminated soil affects the ecosystem due to leaching into ground water or when they are taken up by plants and animals, which results in great risks due to bioaccumulation (Bhagure and Mirgane, 2010). Heavy metals and persistent organic pollution are of concern due to their potential harmful effects to humans and the environment. Wong et al. (2003) showed that heavy metals are potentially toxic to crops, animals and humans when contaminated soils are used for crop production. Pollution of the biosphere with heavy metals, induced by industrial, agricultural and domestic activities pose serious problems for safe use of agricultural lands (Fytianos etal., 2001). In some dumpsites, wastes are burnt in the open and the ashes abandoned at the sites, with no regard to environmental implications. This poses a direct safety threat because of the danger of explosion. The burning of wastes gets rid of the organic materials and oxidizes the metals, leaving the ash richer in metal contents. After the processes of (Momani, 1999). Cd is also found in lubricating oils as part of many additives and car tyres as a result of the vulcanization process. The industrial activities; the metal is widely used in electroplating, pigments, plastics, stabilizers and battery industries (Mehbrahtu and Zebrabruk, 2011). Cd is highly toxic and responsible for several cases of poisoning through food. Small quantities of Cd cause adverse changes in the arteries of human kidney. It replaces zinc biochemically and causes high blood pressures and kidney damage (Mehbrahtu and Zebrabruk, 2011). The recommended concentration of cadmium in soil is 3kg/mg (EU, 1986).1.3.6 IRON (Fe)
Iron is a chemical element with symbol Fe (from Latin: ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.
In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching 1,500 °C (2,730 °F) or higher, about 500 °C (900 °F) higher than that required to smelt copper. Humans started to master that process in Eurasia by about 2000 BCE,[not verified in body] and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. That event is considered the transition from the Bronze Age to the Iron Age. In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels are by far the most common industrial metals, because of their mechanical properties and low cost.
Pristine and smooth pure iron surfaces are mirror-like silvery-gray. However, iron reacts readily with oxygen and water to give brown to black hydrated iron oxides, commonly known as rust. Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion. Although iron readily reacts, high purity iron, called electrolytic iron, has better corrosion resistance.
The body of an adult human contains about 4 grams (0.005% body weight) of iron, mostly in hemoglobin and myoglobin. These two proteins play essential roles in vertebrate metabolism, respectively oxygen transport by blood and oxygen storage in muscles. To maintain the necessary levels, human iron metabolism requires a minimum of iron in the diet. Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals.
Chemically, the most common oxidation states of iron are iron(II) and iron(III). Iron shares many properties of other transition metals, including the other group 8 elements, ruthenium and osmium. Iron forms compounds in a wide range of oxidation states, −2 to +7. Iron also forms many coordination compounds; some of them, such as ferrocene, ferrioxalate, and Prussian blue, have substantial industrial, medical, or research applications.
1.3.7 NICKEL (Ni)Nickel is an essential trace element in animals, although the functional importance of nickel has not been clearly demonstrated. However, there is evidence of uptake and accumulation in certain plants. Nickel deficiency is manifested primarily in the liver. Its effects include abnormal cellular morphology, oxidative metabolism and increase and decrease in lipid levels. The essentiality of nickel in humans has not been established and nickel dietary recommendations have not been established for humans (ATSDR, 2003).Nickel compounds are known carcinogens in both human and animal models (Feder et al., 1996). There is evidence that the geno-toxic effects of nickel compounds may be indirect through the inhibition of DNA repair systems. As a result of this inhibition it has been suggested that accumulation of nickel in breast tissue may be closely related to malignant growth process (ATSDR, 2005).1.3.8 ARSENIC
Arsenic occur naturally in the environment on the earth crust, it is an essential element that becomes toxic when ingested at high level, Arsenic is combined with other elements such as oxygen, chlorine, sulphur to form inorganic arsenic compounds. Arsenic enter into the environment primarily from air and by seeping in to the soil and ground water from hazardous water dumps (kristeen cherney2018).
Arsenic poisoning, or arsenicosis, occurs after the ingestion or inhalation of high levels of arsenic. Arsenic is a type carcinogenic that’s gray, silver, or white in colour. Arsenic is extremely poisonous to humans. What makes arsenic especially dangerous is that it doesn’t have teste or odour, so you can be exposed to it without knowing it. (kristeen cherney2018). Some toxic effects of arsenic poisoning are gastrointestinal complain, diarrhoea, constipation, gastrointestinal, disturbance, loss of appetite, and weight loss exposure to arsenic at low level for extended period of time can cause discordant for skin and the appearance of small corns and warts. Exposure to high level of arsenic can lead to death (Ebong et al., 2008).
1.4 AIMS AND OBJECTIVES OF THE STUDY
The aim of this research is to determined the level of some heavy metals in some selected dump site soil samples in bajoga town of gombe state, Nigerian with following sets of objectives.
(i) To collect the soil samples in the v.cinity of the selected dump sites in bajoga town.
(ii) To determine the level of concentration of the heavy metals ( Cd,Cr,Cu,Pd,Ar,Ni and Fe) in the various dump sites.
(iii) To proffer recommendations based on the findings of the research.
1.5 STATEMENT OF THE PROBLEMS
Like many cities in Northern Nigeria, Bajoga town in Gombe State faces problems of environmental sanitation such as improper disposal of refuse near residential areas; poor refuse collection and handling, it is common to find huge refuse dumpsite within
residential areas and farmers use them as fertilizers. This however, leads to accumulation of heavy metals in plants grown on dumpsite soils or fertilsed with dumpsite manure, which on subsequent transfer through food chain end up in man, posing potential health risk.
The rise in population and civilization in Bajoga town has increased the number of dumpsite due to poor waste management schemes. It is a common practice to burn dumpsite wastes, this burning gets rid of organic matter and become ashes which are richer in metal contents. These ashes are either dissolved in rain water and leached into the soil contaminating the underground water, or washed away by runoff into streams and rivers, thereby contaminating the environment, it is based on these facts that this study is aimed at determining the total concentration of cadmium, copper, nickel, lead and chromium in dumpsite soils and Abelmochus esculentus fruit planted on dumpsite soil in Bajoga town, Gombe State, Nigeria.
1.6 SIGNIFICANCE OF THE STUDY
The research will help the people of Bajoga to be aware with the effects and maintenance of heavy metals in human body and environmental conditions.
1.7 SCOPE AND LIMITATION OF THE STUDY
This project limits its work on six (6) heavy metals in some selected soil of the study area of Bajoga town of Funakaye Local Government Area namely:
1. Unguwar Sarkin Yaki
2. Unguwar Zamfara
3. Unguwar Isah
4. Unguwar Barde-kolo
5. Unguwar Leggel
6. Unguwar Bamalu
CHAPTER TWO
2.0 LITERATURE REVIEW2.1 MUNICIPAL SOLID WASTE MANAGEMENT
Municipal solid waste management is a major responsibility of state and local government agencies. In order to curtail the problems associated with solid waste generation and other related problems, the Federal Government of Nigeria has promulgated various laws and regulations to safeguard the environment. The Federal Environmental Protection Agency Act of 1988, pursuant to the FEPA Act, each state and local Government in the country set up its own environmental protection body within its jurisdiction. The agencies arecharged with the responsibility of handling, employing and disposing of solid waste generated. The state and local government agencies generate fund from subvention from internally generated revenue through sanitary levy and stringent regulations with heavy penalties for offenders of illegal dumping and littering of refuse along streets (Ogwueleka, 2003). Waste handling facilities are lacking in many highly populated areas in most developing and underdeveloped countries due to cost and lack of enforcement of relevant enactment. Poor regional and urban planning, lack of enforcement of relevant laws and edicts on waste disposal, lack of organized landfill sites contribute to the presence of dumpsites within living areas in developing nations. This results in the discharge of household sewage and refuse into the environment untreated. The surface runoff and leachates from dumpsites are sources of fresh water contamination (Abdus-Salam et al., 2011).The recent population and industrial growth has led to increasing production of domestic, municipal and industrial wastes, which are indiscriminately dumped in landfill and water bodies without treatment (Ogunyemi et al., 2003). Municipal solid waste management constitutes one of the most crucial health and environmental problems facing governments of African cities. This is because even though these cities are using 20-50 percent of their budget on solid waste management, only 20-80 percent of the waste is collected. The uncollected or illegally dumped wastes constitute a disaster for human health and result to environmental degradation (Achankeng, 2003). Thousands of old landfills and dumpsites exist throughout developing countries that may pose threat to human health in the next decades, unless appropriate measures are taken. Most developing countries follow the practice of open dumping of solid wastes causing environmental and health risks(Kurian et al., 2003). Industrialization, population growth and unplanned urbanization have partially or totally turned our environment to dumping sites for waste materials (Ikem et al., 2002). A metal of relative high density (specific gravity greater than about 5) or of high relative atomic weight is defined as heavy metal. The term heavy metal is used to describe more than a dozen element that are metals or metalloid (vogels 1989) e.g chromium, arsenic, cadmium, lead, zinc nickel e.t.c heavy metals are natural constituents of the earth crust because they cannot be degraded or destroyed heavy metals are persisted in all part of the environment. In small amounts they enter the human body via food, drinking water and air. living organism require varying amounts of heavy metals iron, cobalt, copper, manganese, molybdenum and zinc are required by human. excessive levels can be described as many metallic elements that has a relatively high density and is toxic or poisonous at low concentration.
Human activities effect the natural geological and biological distribution of heavy metals through pollution of air, water, and soil. Humans are also responsible for altering the chemical formed of heavy metals released to the environment. Such as alterations of often effects a heavy metals toxicity by hollowing it to bioaccumulation in plants and animals. Bio concentrates in the food chain or attack specific organ of the body bioaccumulation refers to an increase in the concentration of heavy metal in biological organism or targeted organ over time until they become hazardous to health (mata et al.,2008). Many metals and other chemicals accumulates in living things anytime they taken up and store faster than they are broken down (metabolized or excreted).


2.2 BEHAVIOUR OF INORGANIC (HEAVY METAL)CONTAMINATION IN THE SOIL
The most prevalent group of elements in the sub soil is the transition metals otherwise called heavy metals. Example includes zinc (Zn), arsenic (As), lead (Pb), nickel(Ni), cadmium(Cd), chromium(Cr) etc. these metals may occur in soil due to industrial or from refused dumps.
2.3 EFFECTS OF MUNICIPAL SOLID WASTE ON THE ENVEROMENT
Poor waste management poses a great challenge to the well-being of city residents, particularly those living adjacent to dumpsites due to the potential of the waste to pollute water, food, land, air and vegetation. The poor disposal and handling of waste thus leads to environmental degradation, destruction of the ecosystem and may cause great risks to public health. The resultant accumulation of waste poses a health hazard to urban inhabitants, and also threatens the surrounding environment (UNDP, 2006).The environmental problems posed by solid waste ranges from health hazards, soil and water pollution, repulsive sight and offensive odour. The resultant effect of these is the degradation of environmental quality (Abdus-Salam et al., 2011). Dumpsites are usually located within the vicinity of living communities and wetlands. These dumpsites are often not lined nor basement prepared for selective adsorption of toxic substances. Therefore, it is prone to release pollutants to nearby water and to the air through leachates and dumpsite gases respectively (Alimba et al., 2006). Many water resources have been rendered wholesome and hazardous to man and other living systems, as a result of indiscriminate dumping of refuse (Bakare et al., 2005).
2.4 SOIL POLLUTIONSoil is a very important natural resource to man as it is a source of life on planet, earth. Without soil, the earth would be as barren as the moon, hence lifeless (Misra and Mani, 2009). Despite its importance, soil is often contaminated by human activities and this is reflected in the high horizontal and vertical variability brought about by the anthropogenic influence on soil formation and development (Fong et al., 2008). A variety of human activities including municipal waste disposal, industrial emissions, military testing and agricultural practices have left their impacts on soils in the form of elevated and high level of toxicants (Van and Krivolutsky, 1996). Materials that find their entry into the soil system persist and accumulate in toxic levels, hence becoming sources of pollution in the soil (Misra and Mani, 2009). The concentration of heavy metals in soil and their impact on ecosystems can be influenced by many factors such as the parent rock, climate and anthropogenic activities (Jia et al., 2010).
2.5 EXPOSURE OF HUMAN TO HEAVY METALS
Since the industrial revolution, the production of heavy metals such as lead, zinc etc. has increased exponentially, production of this metals has increase nearly 10 – fold with emissions rising in tandem, once emitted, metals can reside in the environment for hundreds of years or more human beings may be exposed to these metals through the food chain after the food has been contaminated. Heavy metals have been used in a variety of ways for at least two millennia, for example, lead has been used in plumbing and lead arsenate has been used to control insects in apple orchards. Lead was added to wine to improve its taste and mercury was used to alleviate teething pair in infants, many metals are essential to life and only become toxic when exposures to life become excessive. (i.e. exceed some threshold for the introduction of adverse effect) (Nwajei et al., 2007).
Exposure to heavy metals has been linked with developmental retardation, various cancers, kidney damage and even death in some instances of exposure to high concentrations. Despite abundant evidence of these deleterious health effects, exposure to heavy metals continues and may increase in the absence of concerted policy actions. Exposures to unhealthy elements remain common throughout both developed and developing countries. Unlike most chemicals for which health impacts of low level dose are still uncertain, exposure of lead even at low level is highly toxic
(Ademoroti, 1996). The natures of biological response to metal exposures are direct consequences of exposure and are defined through dose-effect relationship.
2.6 BIOACCUMULATION OF HEAVY METALS IN LIVING SYSTEM
The word environment and society where we live have made bodily contamination impossible to ignore – through eating, smoking, breathing, skin absorption and every day exposure to limitless products and chemicals made and used by human, contaminants find their way into the body. Over time these heavy metals, toxic chemicals and residues, plagues and other natural intruder continue to slowly accumulate. If the body natural detoxification pathways (such as blood lymph and cerebral spinal fluid) cannot eliminate them faster that they enter the body, the build up can eventually reach toxic levels.
“Bioaccumulation of metals is the process whereby organisms stored up metals from the surrounding medium into their tissues by chelating process”. It is the product of equilibrium between the concentration of the metal in organisms, environment and the rate of ingestion and excretion, for example inorganic mercury present in product like pesticide, insecticides, fungicides etc. usually deposit in water to form sediments. These chemicals may be absorbed by Aquatic organisms and the organisms are eventually eaten up by fish, the fish are caught and eaten by man, as such the chemicals may bio-accumulate in man on exposure for a long time. The consequence of this may result to various ailments which may sometime life threatening (Osuj & Onojake, 2004).

    Date: 2026-08-06 00:00:00.000000