Levels of Heavy Metals in some Commercially available Rice on the Liberian Market

Abstract

Human activities such as agriculture, mining, urbanization and waste disposal can lead to heavy metals contamination of food crops, including rice meant for human consumption. In an effort to ensure quality and safe food consumption, this study determined the levels of toxic heavy metals, Arsenic (As), Cadmium (Cd), Chromium (Cr), Lead (Pb), Mercury (Hg) and Nickel (Ni) in rice brands widely consumed in Liberia. Hg was determined by AAS technique using a Lumex RA-915M portable Zeeman Automatic Mercury Analyzer. As, Cd, Cr, Pb and Ni were determined by ICP-MS technique using an Agilent 7900 ICP-MS. The levels of As, Cd, Cr, Pb, Hg and Ni concentrations ranged from 1.1 to 18.1, 4.8 to 117.9, 50 to 424.5, 1.1 to 37.1, 1.1 to 9.4 and 15.1 to 655.2 µg/kg respectively. The study revealed no significant statistical variability in the metal concentrations between the locally cultivated and imported rice, except for As (P = 0.002). The levels of As, Cd, Pb and Hg in all brands were below the World Health Organization/Food and Agricultural Organization guideline values. Cr and Ni levels were also below the European Commission Guidelines for all rice brands analyzed. The results imply that although the rice brands analyzed contain low heavy metal concentrations, the levels are unlikely to cause adverse health effects to the consuming populace.