RISK ASSESSMENT OF TRACE METAL INDUCED BY CONSUMPTION OF SELF ROASTED AND STREET ROASTED COW MEAT(SUYA) FROM SANI OGUN MARKET IKOT EKPENE, AKWA IBOM STATE
CHAPTER ONE
1.0 Introduction
1.1 Background of the Study
Meat makes up an essential part of food we eat and is mainly composed of protein, fat and some important essential elements(Akan et al.,2010). It is also a good source of niacin, vitamin B6 and B12,phosphorous,zinc and iron(Williams 2007).Animal proteins have a high biological value(Ziegler 1968),and the presence of essential amino acids in them makes a complete protein(Bastin 2007).
Apart from meat and meat products forming an important part of the human diet as well as an important source of a wide range of nutrients, they may also carry certain toxic substances (Fathy etal., 2011). Toxic substances in meat tissues can be caused by a variety of sources including animal drugs, pesticides, feeds and other agricultural or industrial chemical substances (Fathy et al., 2011).
Instances of trace metal contamination in meat products during processing have also been reported (Akan etal., 2010).Methods such as singeing of the hairs of the animals in flame fuelled by various substances such as wood mixed with spent engine oil, plastics mixed with refuse or tyres. These materials contain toxic substances such as trace metals which can contaminate the meat and render them unfit for human consumption(Okiei et al.,2009).In other cases, contaminated animal feed and rearing of livestock in proximity to polluted environment were responsible for trace metal contamination in meat(Fathy et al.,2011).
Toxic metal is defined as that metal which is neither essential nor has beneficial effect on the contrary, it display severe toxicological symptoms at low levels and is defined as a metal with a specific weigh more than 5g/cm3.With increasing industrialization, more and more metals are entering into the environment.
These metals stay permanently because they cannot be degraded in the environment. They enter into the food material and from there they make their passage into the tissue (Baykov et al.,1996).Lead, Cadmium, Mercury and Arsenic are among the main toxic metals which accumulate in food chains and have accumulative effect (Cunningham and Saigo,1997).
Trace metals often have direct physiologically toxic effects and are stored or incorporated in living tissues (Baykov et al., 1996). Toxic effects of Lead are seen on haemopoietic, nervous, gastrointestinal and renal systems(Baykov et al.,1996). Food is one of the principal environmental sources of Cadmium. As Cadmium moves through the food chain it becomes more and more concentrated as it reaches the carnivores where it increases in concentration by a factor of approximately, 50 to 60 times (Daniel and Edward,1995).
Toxic effects of cadmium are kidney dyfuncton, hypertension, hepatic injury and lung damage(John and Jeanne,1994).Cadmium chloride at tetratogenic dose induced significant alterations in the detoxification enzymes in the liver and kidney(Reddy and Yellamma,1996).Animals vary in their arsenic accumulation depending upon the type of food they consume(John andJeanne,1994).
Acute arsenic exposure can give symptoms with rapid onset of headache,nausea and severe gastrointestinal irritation(Allan et al.,1995).Similarly,increase in levels of copper causes liver,kidney and brain damage,which may follow haemolytic crisis(Judith,1994).
Streets foods are foods and beverages prepared and or sold by vendors and hawkers in streets and other public places for immediate consumption or at a later time without further processing. These foods are consumed worldwide by an estimate 2.5billion people per day due to low cost and convenience (Steyn and Labadarios,2011).They account for 70% of the energy intake in African cities. However, street meat may contain substantial amounts of toxic metals resulting from mode of preparation and exposure to polluted environment.
Food safety is a major public health concern and its demand by consumers worldwide has stimulated research regarding the risk associated with consumption of foodstuffs contaminated by trace metals. Trace metals occur naturally in the environment and can be found in virtually all plant, animal and food substances (Schuhmacher et al.,1991).
Although small quantities of metals are necessary for human development,continuous and excessive exposure of trace metals can lead totoxicity threathening human health. Due to their non-biodegradability and toxicity at low concentration, Trace metal-intake through the food chain is a problem receiving increasing attention (Liu et al.,2013).
In particular, the general handling of street roasted and vended meats poses a safety threat because they are prepared and sold in open and dusty environment with high levels of contamination from various sources.
Food is the most common non-occupational source of exposure of trace metals for humans. Although human bodies have homeostatic mechanisms that enable them to tolerate small fluctuations in meat consumption, concentrations far above or below certain levels can result in a range of acute and chronic negative health effects.
Two common routes of exposure to trace metals in the food supply are through crops grown in soil with high concentrations of metal and/or irrigated with polluted water and when animals graze in pastures with increased concentrations of trace metals. The latter results in the bioaccumulation and/or biomagnification of metals in animal tissue.
In Nigeria, cattle are free grazing and drink water from any available source including ditches, streams, rivers and other sources that may be contaminated with trace metals. They graze along roadways and other sites that have high contaminations of toxic substances. Previous research in Nigeria has identified high levels of some trace metals in meat. Iwegbue and Iwegbue(2008) found levels of Chromium and nickel above the acceptable limit in beef and some chicken and turkey meat from southern Nigeria.
In recent times, one of the fascinating aspects of present day urban social life around the world is the widespread presence of street food and street food vendors. Street vending is an activity that provides employment to many, while providing nutritious, inexpensive and ready-to-eat food to millions of workers(Shekhar,2010).Some of these foods include grilled/roasted meat.
Grilled meat is known to be an important source of vitamins B and
