Determination of Mineral and Toxic Elements in Rice (Oryza Sativa L.) Produced in Three Locations of Niger State, North-Central, Nigeria

Abstract

Background: Accumulation of heavy metals in the human body may result in toxic effects. They are universally found in the earth's crust and tend to accumulate in crops grown in heavily contaminated soil and hence enter the food chain. On the other hand, some mineral elements are required in a small amount (micronutrients) or large quantity (macronutrients) for the proper functioning of both plant and animal body systems. Objectives: This study determined the toxic and mineral elements in rice (Oryza sativa) varieties produced in three locations of Niger State, North-Central, Nigeria.  Methods: Toxic and mineral elements analysis was conducted on rice samples obtained from three locations in Niger State. Calcium (Ca), Magnesium (Mg),  Phosphorus (P), Copper (Cu), Manganese (Mn), Zinc (Zn), Nickel (Ni), Cadmium (Cd), Chromium (Cr) and Lead (Pb) were analyzed using Atomic Absorption Spectroscopy, while Sodium (Na) and Potassium (K) were determined using a photoelectric flame photometer. Results: Sodium concentrations ranged from 1.33 mg/kg to 1.41 mg/kg; potassium, 3.22 mg/kg to 3.97 mg/kg; calcium, 0.67 mg/kg to 0.88 mg/kg; magnesium, 7.20 mg/kg to 8.25 mg/kg;  phosphorus, 5.82 mg/kg to 7.22 mg/kg; copper, 0.40 mg/kg to 1.35 mg/kg; manganese, 0.15mg/kg to 0.25 mg/kg; zinc, 1.60 mg/kg to 2.90 mg/kg; and nickel, 2.21 mg/kg to 2.24 mg/kg. Lead, cadmium and chromium were not detected in the rice samples. Conclusions: While the toxic metals (Pb, Cd and Cr) were not detected, the concentrations of heavy metals (Cu, Mn, Zn and Ni) were lower than the FAO and WHO recommended level. It can therefore be concluded from this study that rice produced from these locations at the time of study is safe and may not pose immediate health hazards to consumers.  

Keywords: Rice, toxic elements, mineral elements