LEVELS OF HEAVY METALS IN PASTA AVAILABLE IN THE NIGERIAN MARKET ASSESSING THE HEALTH IMPLICATIONS

ABSTRACT

The concentrations of Ni, Mn, Cd, Cu, Zn, Pb and Cr, were determined in some pastas consumed in Nigeria, with a view to providing information on the dietary intakes of heavy metals and exposure of humans to toxic metals. The concentrations of these seven (7) elements were determined by atomic spectrometry after nitric acid/perchloric acid digestion. The concentrations of the metals (µg/g) in the locally manufactured pasta samples were in the following ranges: Ni (0.109 – 0.344); Mn (0.377 – 2.279); Cd (Nd to 0.011); Cu (0.115 – 0.287); Zn (0.162 – 4.846); Pb (0.315 – 0.542); Cr (0.003 – 0.178). The concentrations of the metals (µg/g) in the imported pasta samples were in the following ranges: Ni (0.077 – 0.234); Mn (Nd – 1.118); Cd (Nd – 0.779); Cu (0.028 – 0.289); Zn (0.015 – 2.141); Pb (0.328 – 0.847); Cr (Nd – 0.125). The estimated daily intakes of metals (µg/kg bw/day) from the consumption of local pasta were in these ranges, for noodles: (0.003 – 1.366) for generally exposed children and adults; (0.005 – 2.342) for typically exposed children and adult; for spaghetti  (0.003 – 3.382) for generally exposed children and adults; (0.005 – 6.764) for typically exposed children and adult; for macaroni: (0.007 – 6.118) for generally exposed children and adults; (0.014 – 12.236) for typically exposed children and adults.  The estimated daily intakes of metals (µg/kg bw/day) from the consumption of imported pasta were in these ranges, for noodles: (0.002 – 2.375) for generally exposed children and adult; (0.004 – 4.75) for typically exposed children and adults; for spaghetti: (0.002 – 0.965) for generally exposed children and adults; (0.003 – 1.93) for typically exposed children and adults, for macaroni: (0.028 – 3.285) for generally exposed children and adults; (0.055 – 6.569) for typically exposed children and adults. The estimated daily intakes of these pastas were below the provisional tolerable daily intake limits of the metals as stipulated by FAO/WHO and Expert Committee on Food Additives (ECFA). The  individual and combined metals total hazard quotient values were less than 1. However, the total hazard quotient in imported macaroni (0.919) was appreciable when compared to others. From the estimated total hazard index, no long life health concerns of metals are associated with the consumption of these pastas.

CHAPTER ONE

1.1      INTRODUCTION

1.2      BACKGROUND OF THE STUDY

In line with industrial development; pollution in the environment, and consequently agricultural raw materials, leads to high levels of food contamination across the world from the food safety viewpoint. Cases of environmental pollution confronted very frequently and threatening food safety is due to heavy metals. As a result of soil, atmosphere, underground and surface water pollution, our foods and beverages are getting contaminated by heavy metals [1]. Heavy metals occur in all food as natural or inherent component of plant and animal tissues and fluids and also maybe present as a result of contamination or deliberate addition [2].

Heavy metal is a term given to a group of metals and metalloids which in their standard states

have atomic density greater than 5g/cm3, usually associated with pollution and toxicological problems [3]. ASTDR states that heavy metals are a group of metals and semi-metals associated with contaminations and are potentially toxic [4]. Based on these definitions and observations, heavy metals are therefore classified as essentials if they play the basic role as components of vital biochemical or enzymatic activities in human body, for example, Fe, Mn, Mo, Cr, V, Zn and  as  non-essential  if  they  metals  are  classified  as  with  no  biological,  chemical  and physiological importance to man, for example, Cd, Pb, As and Hg [5].

Essentially, heavy metals have only become a focus of public interest since analytical techniques have made it possible to detect them even in very small traces [6]. This has made it possible for toxicologists, in animal experiments to follow up the effects of individual substances down to the smallest concentrations. The warnings they give particularly about the effects of these metals on the health of chronic consumers and the effects of the accumulations leaves the public disturbed and often times creates pandemonium among activists [6].

Cereals are the  main source of food  in many countries. Concerning human diet, the  most important cereals are wheat (Titicum), rice (Oryza Sativa), oats (Avena Sativa), barley (Ordeum vulgare), rye (Secale cereale), corn (Zea mays), and millet (Panicum miliaceum)[6]. Among them

wheat is one of the most consumed and spread [6]. Nowadays, the derived products of wheat are

more relevant than wheat itself, especially wheat flour. Wheat flour is the irreplaceable raw material of a group of basic and essential food in a balanced diet like bread, pastries and cookies as well as pizzas, sponge cakes and other starchy products [7].

Increasing demand for flour-based products such as bread, pasta, semolina, meat pies, sausage

rolls, and so on etc has continued to expand market for wheat flour. The pastas produced in Nigeria are wheat-based. This commodity is mainly produced by processing wheat, and processing involves sorting and milling of dry grains, and addition of some adjuncts; sugar, honey and dried raisins [8]. Minerals constitute 1 to 3 percent of the weight of a cereal grain and concentrate more in the external areas of the wheat grain [8]. From a nutritional and toxicological point of view, their presence is very important. The metallic content is very variable and will depend on the variety, the type of land where it has been cultivated, the fertilization that has been used and  the  weather. Concerning wheat  flour,  the  content of heavy metals  like  lead  and cadmium is usually very low [8].

Pastas commonly consumed in Nigeria include noodles, macaroni and spaghetti. These commodities serve as quick foods for children and adults in more than one third of homes in Nigeria and beyond [8]. The import ban, changing consumption patterns, increasing demand for more nutritious and easy-to-cook food and the more expensive local substitutes, all have also contributed to the growing demand of domestic pasta products [3]. The high food demand, due principally to the increasing population and urbanization, the severe shortage of time on part of bachelors, spinster and the working mothers and the change in feeding habits and way of life

have combined to make the eating of pasta very popular. Regardless of the wide consumption of this group of food (pasta) by Nigerians, little data are available as regards heavy metal levels in them; hence the need for this study. Food safety is an important aspect of a nation’s economic stability and due to previous reports on the degree of pollution of some other food items [9-13] this study was aimed at assessing some heavy metal like Cr, Cd, Cu, Mn, Ni, Pb, and Zn levels in locally produced and imported pasta (noodles, spaghetti and macaroni), and also estimate the associated health risk involved in their consumption by both adults and children.

1.3      Statement of the Problem:

Heavy metals are persistent in the environment and are subject to bioaccumulation in food chains. Monitoring the concentrations of various metals in food is critical because these contaminants have deleterious effects on humans. Many illnesses and diseases such as hypertension, cancer, depression and metal disorders have been associated with increased concentrations of heavy metals such as cadmium, lead, copper, chromium, nickel, manganese and zinc in human organs [5, 12, 13]. However exposure does not result only from the presence of a harmful agent in the environment. The key word in the definition of exposure is contact [3]. Exposure is often defined as “an event that occurs when there is contact at a boundary between a human and the environment with a contaminant of a specific concentration for an interval of time

[4]. Since our nation is fast turning into a ‘fast food’ society, it is imperative for a research to be carried out to ascertain if these packaged products are actually good for our health. Considering that food including pasta is a particularly important source of the overall metals exposure, undertaking a risk assessment appears to be justified. This can be done by intake measurement which is a quantitative evaluation of exposure. Several organizations such as FAO, WHO, CDC, USFDA etc provided guidelines on the intakes of metal elements by humans. The acceptable

daily intake (ADI) or tolerable daily intake (TDI) or provisional tolerable weekly intakes (PTWI) are  used to  describe safe  levels of intake  for  several toxicants  including toxic  metals  [14]. Exposure exceeding the TDI value for short periods should not have deleterious effect upon health, however acute effects may occur if the TDI is substantially exceeded even for short periods of time [14].

1.4 Objective of Study

1.4.1   General Objectives

      To determine the levels of Cd, Pb, Zn, Mn, Cu, Cr and Ni in locally produced and imported pasta in the Nigerian market.

1.4.2   Specific Objectives

             To determine the levels of Cd, Pb, Zn, Mn, Cu, Cr and Ni in the locally manufactured and imported pasta available in the Nigerian market.

          To compare the levels of these metals in the locally produced and imported pasta.

          To determine any correlation in the metal levels in each pasta product.

          To  compare  the  extent  of compliance  to  guideline  values  of these  metals  to  some

International Standards.

             To estimate the daily intake (DI) of these metals through pasta consumption for adults and children.

          To  compare  the  DI  values  with  accepted  daily  intakes  stipulated  by  International

Standard bodies.

          To estimate any associated health risk in the consumption of pasta by children and adult.

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