ABSTRACT

People in Jema’a Local Government Area of Kaduna State, consume both imported and local

fish without adequate information of likely health consequences from contamination. This

knowledge gap is filled by this study. The aim of this work was to assess the heavy metals

concentration in local and imported fish, as well as river water and sediment in the study area.

To achieve the aim, a total of 21 fish samples comprising of local fish (Barbus occidentalis,

Tilapia oreos, Clarias gariepinus) and imported fish (Ethmalosa fimbritus, Alosa fallax,

Clupea harengus), 6 water samples and 6 sediment samples from Wonderful and Magami

Rivers were collected and analysed for concentration of zinc, cadmium, iron, lead and

mercury using atomic absorption spectrophotometer. Degree of sediment contamination was

assessed using geoaccumulation index. Target hazard quotient was used to assess human

health risk in both local and imported fish. Awareness of risk associated with heavy metals in

fish consumed in the study area was also examined and three hundred and eighty four copies

of questionnaire were distributed to respondents using random sampling technique. Eight (8)

wards namely Kafanchan A, Kafanchan B, Bedde, Kagoma, Jagindi, Asso, Kaninkon, and

Gidan – Waya were chosen using purposive sampling. Data gathered from the questionnaire

were summarized using simple statistics such as tabulation frequency and percentage. Forty –

nine percent (49%) of respondents had some form of general awareness of risk in fish.

However awareness was low on chemical specific risk in fish. People were unaware of metals

in the order cadmium > iron > mercury > zinc > lead. Results of laboratory analysis shows

that cadmium risk is significant in all fish species, while risk of lead is significant in Barbus

occidentalis, Tilapia oreos, Ethmalosa fimbritus and Clupea harengus. Values of water

samples compared with NESREA guideline showed that all water samples were above

NESREA minimum acceptable standard. Geoaccumulation Index for sediments revealed that

mercury (45.2 and 44.5), cadmium (2.3 and 1.6) and lead (4.47 and 3.74) are at higher vi

INTRODUCTION

1.1 Background to the Study

Fish is an important source of protein which is an element necessary for the maintenance of

healthy body. It is one of the most important animal protein sources which is beneficial. It has

low saturated fat, high protein content, and Omega-3 Polyunsaturated fatty acids, all of which

are known to support good health (Burger and Gochfeld, 2004). Fish is highly recommended

by the American Heart Association to be included in the human diet at least twice a week

because it helps to lower the risk of cardiovascular diseases (AHA, 2013).

Therefore, they are consumed on the basis that they promote good health. Nevertheless, in

addition to the nutrients they provide, they contain other substances that are injurious to

health. These are called contaminants. Notable among such contaminants are heavy metals

(Costenla, 2014). Heavy metals are stable metals with density greater than 5 to 6 g/cm3 which

can have hazardous effects when present in higher concentrations (Keepax, Moyes and

Livens, 2011). Arsenic, cadmium, chromium, copper, nickel, lead and mercury are common

heavy metals among others which pollute the environment.

Natural sources such as geologic weathering of the earth crust, volcanic eruptions, soil

erosions as well as anthropogenic sources such as industrial and municipal wastes, as well as

leakages from boats and also emissions via shipping traffic, all cause heavy metals to enter

aquatic environments through the agents of wind and rain where they are ingested by aquatic

organisms.

Fish accumulates substantial amounts of heavy metals in their tissues including the muscles

and thus represent a major dietary source of these metals for humans. When ingested in

excess amounts, heavy metals combine with the body’s biomolecules, like proteins and

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enzymes to form stable biotoxic compounds. These compounds mutilate their structures and

hinder them from carrying out bioreaction functions. As a result, they have been considered

the most dangerous category of pollutants in the aquatic environment (Kalay, Ay and Canli,

1999; Hassaan, Al-Kahali and Al-Edres, 2007).

This present a significant amount of danger due to their ability to bioaccumulate.

Bioaccumulation occurs when there is an increase in the concentration of a chemical in a

biological organism over time, compared to the chemical’s concentration in the environment.

Heavy metals are easily stored in their fatty tissues and will bioaccumulate if fish is exposed

to further contamination. This means an increase in the concentration of heavy metals in fish

over time. (Duruibe, Ogwuegbu and Egwurugwu, 2007). While they are not very visible in

the aquatic environment, their impacts on delicate aquatic ecosystems can be large (Yilmaz,

2003), affecting both fish and human population.

Metals such as copper and zinc can leach into river water from mining industries, and has

been found to affect fish population when present in water even at low doses (Saei-Dehkordi

and Fallah, 2011). Higher level of copper in fish can cause diarr