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24 samples of different brands of yoghurt were collected from 2 popular Lagos market and Atomic Absorption Spectrophotometer was used for the determination of heavy metals i.e. Lead, Cadmium and Chromium.   100% of the samples were found to have the concentration of heavy metals below the safe limit recommended by world health Organization (WHO).  The concentration of Lead, Cadmium and Chromium fall between 0.52ppm – 0.92ppm, 0.14ppm – 0.49ppm and 0.26ppm – 0.75ppm respectively.  The group mean of concentration of each elements (Lead, Cadmium and Chromium) in all brands are 0.70ppm, 0.27ppm and 0.41ppm respectively.  This findings suggest that the concentration of all the heavy metals in yoghurt falls within the safe limits.  The recommended Lead (pb), Cadmium and Chromium are 0.2 – 2.0ppm, 0.5ppm and 1.0ppm respectively according to World Health Organisation, but the relatively increase of Lead (pb) in yoghurt could be attributed to the industrialized status of Lagos State which if not checked might lead to greater value eventually.



Increasing industrialization has been accompanied throughout the world by the extraction and distribution of mineral substances from their natural deposits.

Following concentration, many of these undergone chemical changes through technical processes and finally pass by way of effluent, sewage dumps and dust into the water, the earth and the air and thus into the food chain.

The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at high concentrations. Examples of heavy metals include Mercury (Hg), Cadmium (Cd), Arsenic (As), Lead (Pb), Chromium (Cr), Thallium (Ti). Heavy metals are natural components of the earth’s crust.  They cannot be degraded or destroyed.  To a small extent they enter bodies via food, drinking water and air.  For food analyst they are termed contaminants which are undesirable materials, which have been added to advertently before, during or after processing of foods.  Heavy metals are dangerous because they tend to bioaccumulate.  Bioaccumulation means an increase in the concentration of the chemical in biological organism overtime compared to the chemical concentration in the environment, compounds accumulate in living things anytime they are take up and stored faster than they are broken down or excreted.

During the early life most substances that people were likely to encounter in their daily lives were derived with little modification from the earth, the animals, vegetables, crops or the mineral sources. Today, there is an extensive existence of synthetic chemical in the environment a class, which was not present until their creation by human scientific and industrial effort.  The domination of chemicals is increasing in our lives, can we imagine life without Agrochemicals, pharmaceuticals, preservatives, colourants, plastics, etc. (Envis Newsletter, 2002).  Heavy metals can enter a waste or even from acidic rain breaking down soils and many heavy metals into streams, lakes, rivers and ground water. The presence of the most undesirable elements in foods can usually be attributed to any of the following causes:

·        Natural occurrence e.g. deposition in the liver of animals.

·        Sprays used as insecticides during cultivation e.g. Lead arsenate.

·        Accidental contamination due to confusion of materials of similar appearance.

·        Food may dissolve metals from the equipment and containers e.g. from Tin plate, foils, solders galvanized iron and cheap enamels and glazes.  Fermented dairy products such as yoghurt are among the recreational drinks taken paramount to boost appetite and could also be taken at leisure.  Yoghurt is a fermented milk product, which has its origin in Eastern Europe, but it is now consumed throughout the world.  The French called it “milk of eternity” as it was believed to have therapeutic powers and gave life to those who consumed it.

Yoghurt is about the most consumed milk product in Lagos State which may partly be accounted for by the fact that, it is the most readily available milk product and since cheese is difficult to come by in Lagos unlike the 
other parts of the country.  In the above sense the investigation of heavy metals should be a paramount and essential topic.  Because the toxicity of the heavy metals such as Lead causes miscarriage in pregnant women, sudden and infant death syndrome and stillbirth. (Boekx, 1986).  The increase in Lead in the body is also known for its devastating effects on brain development (Bryee – Smith and Stephenes, 2001).  Chromium causes kidney and liver damage and Cadmium also causes renal problem, anaemia and reproductive failure. (Murthy and Reha 2001).  Heavy metals such as Lead, Cadmium and Chromium have been recognized to be potential toxic within specific limiting values, a considerable potential hazard exit for human nutrition.

The metals are useful to man, but their usefulness depends on the chemical specification for examples their salts could be used as preservatives, disinfectants, fumigant and so on in the industries producing yoghurt.


·        To detect the occurrence of heavy metals, Lead, Chromium, Cadmium contaminating yoghurt sold in Lagos market.

·        To determine the concentration of these heavy metals in yoghurt sold in Lagos market.

·        To give review on the health implication of these heavy metals at high concentration.

This material content is developed to serve as a GUIDE for students to conduct academic research

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