SUMMARY

Lead is a bioaccumulative heavy metal usually found in nature combined with other

elements to form lead compounds. Over 400 children were reported to have died as a

result of lead poisoning outbreak in Zamfara State, Nigeria and about 2000 children

are currently on treatment. The prevalence of lead residues in tissues of animals

slaughtered at Gusau abattoir, Zamfara State was determined using Atomic

Absorption Spectrophotometer. A total of 384 tissue samples were collected and their

lead content determined. About 95% of the 384 animals were purchased from markets

within Zamfara State and out of all the samples investigated 324(84.4%) had lead

residues. The lead residues in 314(81.80%) of the animals were above the permissible

limit of 0.1mg/kg recommended by World Health Organisation and European

Commission. Lead residues were not detected in about 60(16.60%) of the animals

sampled. There was no significant difference (p>0.05) observed in tissue

accumulation of lead in animals based on difference in age, sex, species or breed of

the animal. Gross contamination of the environment from where these animals were

sourced could therefore be inferred.

KEY WORDS: Lead residues, Animal tissues, Atomic Absorption

Spectrophotometer

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CHAPTER ONE: INTRODUCTION

1.1 Background Information

Lead is a bluish soft metal with atomic number 82; atomic weight 207.19, specific

gravity 11.34, melting point 327⁰C and boiling point 1740⁰C. It is the most common

industrial metal that has become widespread in air, water, soil and food.1 Metals are

often characterized and distinguished from non-metals by their physical properties

which include the ability to conduct heat, and an electrical resistance that is directly

proportional to temperature, malleability, ductility and even luster.2

Heavy metals can be classified into four major groups based on their health

importance.3, 4 Copper, zinc, cobalt, chromium, manganese and iron are essential and

also called micronutrients but are toxic when taken in excess of requirements.4, 5

Barium, lithium and zirconium are non – essential. Tin and aluminium are less toxic

whereas mercury, lead, cadmium and arsenic are highly toxic.

They are (lead, cadmium, mercury and arsenic) among the main toxic metals that

remain in the environment permanently because they cannot be degraded and thus

find their way into the food chain and ultimately into the tissues. They have direct

physiologically toxic effects when stored or incorporated in living tissues.6

Heavy metals are kept under environmental pollutant category due to their toxic

effects on plants, humans and food. Heavy metals such as lead, arsenic, cadmium and

mercury are persistent, accumulate and are not metabolized in to other intermediate

compounds and do not easily break down in environment.1

Poisoning by toxic chemicals can cause serious stock losses. Historically, lead and

arsenic have been the most common causes of inorganic chemical poisoning in farm

animals.7 The increase in industrial and agricultural processes has resulted in

increased concentrations of metals in the environment. These metals are taken in by

1

plants and consequently animals that graze on such contaminated plants and animals

that drink from polluted water also accumulate such metals in their tissues.8 Some

heavy metals like arsenic, cadmium and lead have been reported to have no known

bio-importance in human biochemistry and physiology and consumption even at very

low concentrations can be toxic.9, 10

Several organisations have pointed out the need for monitoring heavy metal

concentrations in the environment because of their persistence and accumulation in

the biota.11

Lead is a metabolic poison and a neurotoxin that binds to essential enzymes and

several other cellular components and inactivates them.12 Toxic effects of lead are

seen in haemopoeitic, nervous, gastrointestinal and renal systems.6

Lead poisoning is a medical condition caused by increased levels of the heavy metal

lead in the body. Lead interferes with a variety of body processes and is toxic to many

organs and tissues including the heart,