Evaluation of Some Toxic Heavy Metals in Rice and Beans Samples Cultivated in Yobe State, Nigeria

Abstract

Grains have become an integral part of the human diet due to their nutritional values, thus any form of contamination especially by heavy metals is of great concern. This research evaluated the level of Cadmium, Chromium, Lead and Mercury in the commonly consumed foods (Rice and Beans) across Yobe State, North-eastern Nigeria. A composite sample from each of the three Senatorial Zones was collected from farm harvests and designed as ZAR, ZAB, ZBR, ZBB, ZCR and ZCB for Zone A Rice, Zone A Beans, Zone B Rice, Zone B Beans, Zone C Rice and Zone C Beans respectively. The metal Concentration was determined using atomic absorption spectroscopy (AAS). Results in mg/Kg across the local governments indicates respective ranges for Hg, Pb, Cd, and Cr of 0.30 - 4.04, 0.16 - 0.92, 0.03 - 0.05 and 0.02- 0.52 in Rice, 0.14-3.73, 0.05-0.33, 0.05-0.07 and 0.00-0.14 in beans. Comparison of the results showed that with the exception of mercury, all metals are within the tolerable ranges set by International Standard Tolerable Limits and European Regulatory Standard. Potential hazards may be speculated because the detected levels are on the higher side of the tolerable ranges. A higher level of mercury in samples collected from Zone C might be associated with the reported cases of chronic kidney diseases from those areas.