EFFECT OF HEAVY METALS ON FISH AND WATER Fish is high in omega-3 and protein that the human body needs to stay healthy. However, potentially dangerous heavy metals are absorbed into the body tissues of fish that are transferred to humans on consumption of this affected fish. Good quality of food for human consumption can only be produced in an environment free from contamination and pollution. Fish are of great economic importance, but are affected immensely by various chemicals including heavy metals directly or indirectly in different ways.   

Several reports indicate high mortality of juvenile fish and reduced breeding potential of adults after long term exposure to heavy metals8. The freshwater fish, Labeorohita is of great commercial importance because it is the most common fish widely consumed worldwide. Therefore, it can be a good model to study the responses to heavy metal contaminations. Histopathological studies on fish are a noteworthy and promising field to understand the structural organization occurs in the organs due to pollutants in the environment. These structural changes vary with the body parts, nature of the pollutant, medium and duration of exposure. Water quality characteristics also influence histopathological manifestations of toxic effects2. The structural changes in the organs at microscopic cellular and organ level leads to alterations of the function systems. Hence the main objective of this study is to provide insight into the source of heavy metals and their harmful effects on environment and living organisms.










Heavy metal toxicity has proved to be a major threat as several health risks are associated with it. These metals have hardly any biological role to play in the human body but on the contrary their toxic effect causes malfunctioning of the body system. These elements may sometimes act as pseudo elements of the body, interfering with the metabolic processes that occur in the body. They accumulate in the body resulting into chronic diseases. In order to maintain public health, measures have been taken to control and prevent by treating metal toxicity occurring at various levels like occupational exposure, accidents and environmental factors. Metal toxicity depends on the absorbed dose, its route as well as duration of exposure. These heavy metals bind with protein sites which are not meant for them, by displacing original metals from their natural binding sites causing malfunctioning of cells by their toxicity. Oxidative deterioration of biological macromolecules is primarily due to binding of heavy metals to the DNA and nuclear proteins. Industrial waste contain large number of toxicants such as salts of heavy metals, acids, organic matter, pesticides and even cyanides which deteriorate the physico-chemical characteristics of water. These pollutants build up in the food chain and are responsible for adverse effects and even death of the organisms in the aquatic system. Fish serve as biomarkers of environmental pollution as studies on the overall health are widely carried out in order to evaluate the physiological changes of aquatic ecosystems. Heavy metals are generally referred to as those metals which possess a specific density of above 5 gm/cm3 and adversely affect the environment and living organisms. These metals are quintessential to maintain various biochemical and physiological functions in living organisms in very low concentrations only. These metals prove to be noxious when they exceed certain threshold concentrations. Heavy metals are significant environmental pollutants and their toxicity is a problem of increasing significance for ecological, evolutionary, nutritional and environmental reasons. The most commonly found heavy metals in waste water include copper, nickel, zinc, cobalt and cadmium all of which cause risks for human health and environment. Heavy metal toxicity can lower energy levels and damage the functioning of brain, lungs, kidney, liver and blood composition and other important organs. Long term exposure to high concentrations lead to gradual and progressive physical, muscular and neurological degenerative processes that initiate disease like multiple sclerosis, Parkinson’s, Alzheimer’s and muscular dystrophy. Repeated long term exposure of some metals and their compounds may cause cancer.








Copper is a trace element which is essential for the function of specific protein enzymes. However, at high concentrations it is toxic to the organisms. The increasing industrial activities and the use of CuSO4 as a fungicide in agricultural practices as well as in the control of algae and pathogens in fish culture ponds have increased the copper concentrations in aquatic systems. It is used in combination with lime and water as a protective agent3. Copper sulphate is very toxic to fish. Its toxicity to fish varies with the species and the physical and chemical characteristics of the water9.



Nickel finds numerous applications in many industries because of its resistance to corrosion, high strength and durability, pleasing appearance, good thermal and electrical conductivity and its ability in forming alloys with other metals. The production of alloys accounts for approximately 75% of total nickel consumption6, 7, 10. The pathogenesis of nickel toxicity is relatively complex because of the large number of chemical and physical forms.



Zinc, an essential trace metal becomes toxic when in the nutritional supply it becomes excessive. The main uses of zinc are in the manufacture of galvanized iron, bronze, white paint, rubber, glazes, enamel glass, paper, as a wood preservative (ZnCl2, fungicidal action), petrochemicals, and fertilizers and in steam generation power plants6. Some zinc is released into the environment by natural processes, but most comes from activities of people like mining, steel production, coal burning, and


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37th Annual Conference of the International Association for Impact Assessment 4 – 7 April 2017 | Le Centre Sheraton | Montréal | Canada | www.iaia.org burning of waste. It attaches to soil, sediments, and dust particles in the air. Zinc compounds can move into the groundwater and into lakes, streams, and rivers. Most of the zinc in soil stays bound to soil particles. Moderately increased zinc concentrations in water also stem from the release of zinc from drainage pipes due to corrosion. It accumulates in fish and other organisms4.





Cobalt is found in meteorites. Elemental cobalt is a hard, silvery grey metal. However, cobalt is usually found in the environment combined with other elements such as oxygen, sulfur, and arsenic. Small amounts of these chemical compounds can be found in rocks, soil and plants, Cobalt metal is usually mixed with other metals to form alloys, these alloys are used in a number of military and industrial applications such as aircraft engines, magnets, and grinding and cutting tools. Cobalt compounds are used as colorants in glass, ceramics, and paints, as catalysts, and as paint driers. Cobalt colorants have a characteristic blue color; however, not all cobalt compounds are blue. Cobalt compounds are also used as trace element additives in agriculture and medicine.



This metal was first used in World War I as a substitute for tin and in paint industries as a pigment. Today, it is also being widely used in rechargeable batteries, for production of special alloys, and is also present in tobacco smoke. About three-fourths of cadmium is used in alkaline batteries as an electrode component, the remaining part is used in coatings, pigments and in plating works and also as a plastic stabilizer. Humans may get exposed to this metal primarily by inhalation and ingestion and can suffer from acute and chronic intoxication.






1.2 Statement of the problem

Conditions like wrinkled cell membrane damaged or enlarged nucleus and vacullation lead either to anemic condition of animals or death in the long run. Anemic conditions and less iron content have been reported in fish, bird and mammal following exposure to pollutants by several researchers.

Heavy metals likecadmium (Cd), nickel (Ni), chromium (Cr)and lead (Pb) were tested in different organs like gills, livers, kidneys and flesh tissues of the control fish enduring in natural water system. And most of the metals are present in edible portion of fish. Humans are also affected by eating fish and can cause a few of health problems.The levels of toxic elements in different fishes depend on the fish sex,age, season and place. The pollution of waterways with anthropogenic activities are the major cause of aquatic loss and imbalanced food chain.


  • Objectives of the study


1.To understand the effect of heavy metals on fish and water

  1. To understand the relationship between effect of heavy metals on fish and public health health safety.


  • Research questions

1.What is the effect of heavy metals on fish and water

  1. What is the relationship between effect of heavy metals on fish and public health healthsafety.



  • Research hypothesis

H0: There is no relationship between effect of heavy metals on fish and public health health safety.

H1: There is a relationship between effect of heavy metals on fish and public health health safety.











Heavy metal pollution have dreadful effects on the environmental equilibrium and a variety of aquatic entities. In the list of animal species, detrimental effects of these pollutants, can never be negligible for fishes. The universal problem is the environmental pollution and most important pollutants are the heavy metals in aquatic network because of their toxicity, accumulation and bio-magnification by marine creatures. Domestic, industrial and anthropogenic activities may broadly become the source of natural aquatic systems contamination of heavy metals. The pollution caused by heavy metals might have.


Fishing is a also general pastime [8,9,10] including in urban areas.The pollutants such as heavy metals bioaccumulate in food chain and cause the antagonistic effects, even death so fish among other animals are used to determine the health condition of aquatic ecosystem. Accumulation patterns are more in some fish species than others because of the ability of fish to bioaccumulate metals. Heavy metals in fish come mainly from their diet, and levels of bioaccumulation of contaminants are higher in fish which comes higher in food chain . In this study, the levels of five heavy metals i.e. zinc, nickel, cadmium, lead and chromium has been determined from the fishes, sediments and water. Heavy metals concentrate in water and entered into the food chain. The patterns of bioaccumulation of heavy metals are determined by the absorbance and excretion rates of fish. Different factors such as physical and chemical properties of water as well as seasonal changes are the reason of significant augmentation of metals in different fish tissues. Metal residual problems in the fish epithelium are stern, because of the presence of higher metal concentrations in water and sediments.

On the contrary, heavy metals are of serious concern in this respect because they can be easily elevated in the food chain due to their bioaccumulation processes. The pattern of heavy metal uptake in fish is different in different species according to various factors i.e. the developmental and psychological factors and also the age of the fish. Fish can transport major dietary sources of arsenic and mercury to humans because of their higher uptake mechanism in their tissues towards these elements. Processed water from the, detergent, textile and cosmetic industries present near the river water have high concentrations of heavy metals, which cause the disruption of the ecological balance of river water if present in much higher concentrations. The scheme of accumulation regarding heavy metals in the liver and gills was found maximum forCd and Pb respectively. Similarly, forflesh tissues the maximum  concentration of Pb and Cd was found. In all heavy metals, the bioaccumulation of lead and cadmium proportions was extensively augmented in tissues of Cyprinus carpio (Common carp).



The toxic effects of heavy metals can affect the individual growth rates, physiological functions, mortality and reproduction in fish [20]Heavy metals entre in fish bodies by three possible ways:  by gills, by digestive track and body surface. The gills are considered as the significant site for direct uptake of metals from the water, though the body surface is normally estimated to take minor part in uptake of heavy metals in fish. Heavy metal accumulation can also be caused by the food source, possibly leading to bio-magnification, the augmentation of toxins up the food chain . The periodic difference of heavy metals based on the data of two consecutive years and samples gathered from the fish farmexposed the following result: summer > autumn >winter > spring.  As a human food, Fish are considered as an excellent source of polyunsaturated fatty acids (predominantly omega-3 fatty acids), protein, Zn, iron and calcium [8].  Seafood will be an even more important and safe source of food in future for protein and fatty acids for human intake and products made from aquaculture (WHO, 1999). Different factors that are considered to be critical are size, developmentalstage and salinity in heavy metal toxicityto marine and estuarine organisms .Affected organisms show response to heavy metals by accumulating in theirbodies or by shifting to the next trophic level of the food chain.

Effects of chromium on fish

Heavy metals accumulated in fish either from the surrounding water or by ingestion of food in environment [25]Due to anthropogenic activities natural water is being contaminated by this metal. The chromium concentration in rivers and lakes stated to range between 1 to 10 ug/L and EPA recommendation for permissible level are 50 to 100 ug Cr/L for protection of human health and aquatic life respectively.Some species of fishes have poisonous effect of chromium as echoed in the blood changes such as anemia, eosinophilia and lymphocytosis, bronchial and renal lesions.Chromium known for its lesser accumulation in fish bodies while the higher concentrations of Cr damages the gills of fish swimming near point of Cr disposal[26]. Effect of chromium on humans by fish intake

Fish being at the higher level of the food chain accumulate large quantities of metals and the accumulation depends upon the intake and elimination from the body [27]. Cr (VI) is harmful to human health, mainly for those who work in textile and steel industry.  The tobacco smokers also have higher possibility of disclosure to Cr. Chromium (VI) can cause many health effects. Chromium in leather products can cause skin rash like allergic reactions. After breathing in Cr can cause noseirritationsandnosebleeds[27]. Other health problems caused by Cr (VI) are:

  • Faded immune system
  • Skin diseases
  • Cause ulcer and upset stomach
  • Respiratory track problem
  • Alteration in genetic material
  • Lung cancer
  • liver and kidney damage
  • Death

Effects of cadmium on fish

Cadmium is the non-essential andmost toxic heavy metal which is widely distributed in the aquatic environment and earth’s crust. In the list of heavy metals such as lead, mercury and cadmium are considered to cause public health hazards [28]. Burning of fossil fuels and municipal waste are known to be largest sources of cadmium release to the environment (such as coal or oil) [29].

Cadmium may also enter into the atmosphere from zinc, lead or copper smelter [30]. It can enter into the fresh water by disposal of industrial and household waste. Fertilizers often contain some cadmium. Reproduction rate of aquatic organisms may also be affected due to Exposure to heavy metals and can lead to a gradual extinction of their generations in polluted waters [31].For example, Cd and mercury (Hg) damage the kidney and produced signs of chronic toxicity, including impaired reproductive capacity and kidney function,tumors, hypertension and hepatic dysfunction [32]. Fish creates major sources of human beings food which is protein.Fishes are major part of the human diet and it is therefore not surprising that numerous studies have been carried out on metal pollution in different species of edible fish [33, 34, 35]. The nutritiveneed of different tissues of fish depends on their biochemical configuration like mineral contents, amino acids, protein and vitamins,etc. The sub lethal concentration of Cd has showed deviations on the electrophoretic arrangements of protein segments in gills and muscle O. mossambicus.

Afshan  et al

Health effects of cadmium in humans by intake of fish

Unfortunately the chemical contaminants are stored within the lipid component of the fish[36]so they are well protected when entering the human body. Wild fish from certain polluted areas may be highly contaminated.[37] Metals such as cadmium, mercury, arsenic and lead are non-essential and therefore have toxic effects on living organisms [38, 39, 40]. These heavy metals accumulate in tissues and body of aquatic organisms in higher concentration than concentrations in water and biomagnified in food chain that cause physiological damages at higher trophic levels and in human consumers.

Human beingtakes Cd mainly through food. Foodmaterialscontains higher Cd can significantly increase the Cd concentration in human bodies.  The food materials that contain higher Cd are;fish liver, shellfish,mushrooms, dried seaweed etc. In start Cdtransported to liver through the blood where it bond to proteins to form complexes that are transported to kidneys where it harms the purifying mechanisms. In results, this causes the excretion of sugars and essential proteins from the body and further damage kidneys. It takes time before Cd that accumulated in kidneys and excreted from human body.  Other related health effects caused by cadmium are:

  • Diarrhea
  • Vomiting
  • Stomach problems
  • Fractures in bone
  • Damage to DNA
  • Failure in reproduction and fertility
  • Cause damage to nervous system
  • Damage to immune system
  • Cause cancer Effects of Zinc on Fish

Zinc can accumulate in the bodies of fish, when they live in Zn contaminated water courses. When zinc enters into the bodies of these fishes, it results inbio magnify up the food chain. The Zn concentrations in fish tissue decreased meaningfully with increasing length of the fish, is regarded as a controversial subject [8],Zinc, an essential element, is one of the most common heavy metal pollutants. The sources of zinc and other heavy metals in natural waters may be from geological rock weathering or from human activities such as industrial and domestic wastes water discharges and animals where it forms constituent functions in maintaining cytoplasmic veracity [14]. However at higher concentrations, Znproduced adverse effects in fish by structural damages, which affects the growth, improvement and survival of fish. Zinc accumulates in the gills of fish and this designates a depressing effect on tissue respiration leading tohypoxia which results in death. Zinc pollution also tempts changes in ventilator and heart physiology[5]. Sub-lethal levels of zinc have been known to unfavorably affect hatchability, existence and hematological strictures of fish. Zinc could cause sub-acute effects that change fish behaviors. Such observed behaviors include deficiency of balance since most fins are stationary in the affected fish, restless swimming, air guzzling, periods of dormancy and death. [42]The Zn danger is taken as very serious because of itsalmost unlimited persistence in the environment because it just transformed from one oxidation state or organic complex to another and cannot be destroyed biologically. Zinc is a potential toxicant to fish [4] which causes disturbances of acid-base and ion regulation, disruption of gill tissue and hypoxia [43].

Effects of Zinc on Humans by Intake of Fish

Its need of time to define the concentrations of heavy metals in commercial fish and shrimps in order to determine the possible risk of human consumption. Accumulation of heavy metals in tissues mainly depends upon concentration of metals in water and exposure period; although some other environmental factors such as salinity, pH, hardness and temperature play significant roles in metal accumulation [44]. Zinc isunique element that is little essential for human health. When people exposed to little Zn they can experiencedecrease in sense of taste and smell,loss of appetite, slow wound healing and skin sores while Zn deficiencies can even cause birth defects.

Although humans’beings can manage large concentrations of Zn, too much Zn can cause prominent health problems such as skin annoyances, such as stomach cramps, anemia, vomiting and nausea. High levels of Zn damages the pancreas and disturb the protein metabolism, and cause arteriosclerosis. Extensive exposure to Zn chloride can cause respiratory disorders. However, it is worth mentioning that some of the researchers are of the view that adverse effects of the fish are neutralized in the process of cooking. Moreover, such negative effects are further reduced while p7r4`acking the fish for human feasting.

Effects of Lead in Fish

When accumulation reaches a substantially high level, accumulated heavy metals in the tissues of aquatic animals and may become toxic [45]. Aquatic organisms exposed to a higher concentration of heavy metals

Afshan  et al

in water may take up substantial quantities of these metals. Bio-magnification of a pollutant may lead to toxic levels in species high up in the trophic chain and in freshwater systems. Lead (Pb) is as a potent environmental pollutant. Lead toxicity has become very important due to its great concern for human health [46, 47, 48]. Fish are usually among the top consumers. [41]. Fish and people are primarily exposed to Pb by food ingestion and breathing. Lead accumulates in the muscles, bones, blood and fat. Newborns and young children are especially delicate to even low levels of lead. [49]

  • Effects organs – Pbseverely damage to liver, kidneys, brain, nerves and other organs. Exposure to Pb may also lead to reproductive disorders osteoporosis (brittle bone disease) and
  • Affects the blood and heart – Pb exposure causes increases in heart disease, high blood pressure, especially in men. Pb also causes anemia.
  • Affects the nerves and brain – Extensive exposure to Pb causes memory problems appropriations, behavioral disorders, mental retardation while lesser levels of Pb damage the nerves and brain in fetuses and young children, resulting inlowered IQ and learning deficits.
  • Effects on Fish – Lead enters in water systems through runoff, industrial and sewage waste streams. Increasing levels of Pb in the water can cause generative damage in some aquatic life and cause blood and nervous changes in animals and fish and other [50, 51,52]



3.1 Methodology and procedure

In this research the researcher among other methods used the analystical research method. The analystical research is concerned with the collection, presentation, analysis and interpretation of data for the purpose of describing vividly existing conditions, prevailing practices and beliefs, attitudes, on-going procures etc. the analystical research goes beyond the description of the conditions or phenomena to include discovery of meaning. It also focuses a discovery of trends that are developing. The main objectives of analystical research is to get detailed and factual information about issues, events, problems and describe the events as they are.

The analystical research method enabled the researcher to describe in a systematic manner effect of heavy metals on fish and water

. The essentials of the analystical research cannot be over-looked, it is a research that gives the true picture of the whole situation or problem. It gives the basis for eliciting possible policies for alleviating problems. It also saves time. The data for the descriptive analysis was generated through various types of data collection; they are interviews, which are structured interview and unstructured interview, also through an empirical investigation. They all will be discussed below.


Interviews involve eliciting information from the respondent through some verbal interaction between the interview and the respondent. It is a face to face interaction situation in which one person the interviewer questions, which are responded to orally. The questions which are properly framed, allows the respondent easy understanding of the information that are being sort for.

3.2   The empirical investigation

The researcher conducted a detailed empirical investigation in selected states of Nigeria. The method here was based on sustained participant observation approach (Scott, 1965). Data were collected through interviews, study of secondary material and observation. The observation is an investigation method used to obtain direct information method used to obtain direct information on the behavior of individuals, objects or situations. It involves watching people, situations phenomena and getting first-hand information relating to particular aspects of such people, events, situations or phenomena.

Information relating to certain aspects of human behavior can only be obtained in the particular settings where such behaviors are exhibited. Use of interviews are discussed above. Secondary materials are those source of information which other people did not participate or witness the events. The author of a secondary source material tries to collect and synthesize a pool of materials, which include encyclopedia, dictionaries, textbooks, journals and periodicals, newspapers and magazines as well as publications. Extensive use was made of personnel interviews. In this research the researcher concentrated on focused interviews. This involved the use of guided questionnaire sheet which are designed to assist the researcher to obtain desired information from the respondents. This technique was aimed at giving the respondents the freedom to answer questions asked, while the interviewer occasionally directed the discussion towards the    course that will enable him obtain the required information.

3.3   Reliability of data collected

interviews used where the structured interviews and unstructured interview. The structured interview is a rigidly standardized and formal kind of interview. The questions were presented to the different respondents, in the same order and choice of alternative responses, and it is restricted to predetermined list. The structured approach allowed for reliable data analysis. In the unstructured interview, which is a flexible type of interview which contains very few restrictions on the respondent’s answers, the respondents were encouraged to express their thoughts freely.

The secondary materials that were studies were those relating to internal topic. These include textbooks, publications of government, newspapers, journals and periodicals. The textbooks were gotten from the library to provide detailed information and knowledge. Generally, the textbooks provided interpretation in the topic. The government publications like books, pamphlets, e.t.c. from different government agencies and parastatals contain very rich information concerning the topic, they included statistical reports, research reports, official reports, laws and other materials that are not readily available elsewhere.

The newspapers on the other hand provided current information concerning peoples’ views and opinions in the area of study. The formed valuable sources of information from where good ideas have been obtained to be helpful in designing and executing a very good work




In this study, the research method had great emphasis toward the descriptive sample survey. This approach was adopted here because the researcher worked with a much number of potential variable of interest with little previous knowledge of theory that would inform us on where to begin.  It is considered that a more flexible and exploratory approach will be needed.

A possible compromise between the exploratory research of the single participant observer and a much more systematic and standardized approach is the descriptive sample survey.  In this sample survey, a premium is placed on certain kinds of standardization, here the research was concerned with the methodology areas.

This final to collect data in such a way that all respondents are confronted with rarely identical questions.This seems is concerned with sampling are the question of generalization in making results.  The third is with specifying standard criterion for data analysis procedure so that different analysis may reach similar conclusion based on the available data.

3.5 Population of the study

The available population of the affected states is two hundred and fourteen (200), the information was obtained from the records of various sources.

3.6 Instrument for data collection

Two instruments where used in the study and it yields a lot of contribution and contents.

  1. Oral Interview: The research used face-to-face interview with the interviews with the respondents to obtain the necessary information needed from the organization.
  2. Questionnaire: The research used questionnaires to gather information from the respondents.  The questionnaire contains difference questions.  Some option from which the respondents were, required to choose

iii. Secondary data

3.7 Validation of the instrument

The instrument was subjected to both content and face validity by supervision, after all the corrections, the validated instrument was taken back for conformation to ensure that suggestions and observation were incorporated.

3.8 Reliability of the instrument

The instrument was subjected to test, retest reliability test.  The result showed a good internal consistency.

3.9 Methods of data collection

The data for this study where obtained from primary data where obtained from respondents, through direct interview and questionnaire method.

The secondary data were obtained through the stocks of material from the researchers’ friends and associates and National library.  More so, an experience from observation was very helpful in this research work.


3.10 Methods of data analysis

The analysis of data was organized along the following lines. Quantitative analysis was used.

















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