Quantification of Heavy Metal Levels in Some Locally Produced Rice (Oryza Sativa) from the South-East and South-South Geopolitical Zones of Nigeria

Abstract

The contamination of our foods with heavy metals has predisposed humans and even animals to heavy metal toxicity which is of public health importance. These findings have drawn the interest of biochemist, nutritionist, health workers and researchers all over the world. Rice is one of the most widely consumed staples in Nigeria. This study investigated the concentration of heavy metals in locally produced rice from the South-East and South-South geopolitical zones of Nigeria. A total of ten (10) samples were collected from various locations in the South-East and South-South geopolitical zones and five (5) heavy metals (As, Cd, Cr, Pb and Hg) were analyzed from each samples. The result showed that of Cr and Pb concentrations ranged from 0.019-0.282mg/kg and 0.000-1.722mg/kg respectively. The average mean for chromium (Cr) and lead (Pb) concentrations were 0.060 and 0.777mg/kg respectively. Mercury, chromium and arsenic were below detectable concentration of <0.001mg/kg. To assess the safety of dietary intake, weekly intake of heavy metals contaminated rice, was calculated based on the intake of a typical 60kg body weight Nigerian. The result indicated that weekly intake of heavy metals from rice was above the provisional tolerable weekly intakes recommended by FAO/WHO and USNAS (United States National Academy of sciences). This study also showed that Cr and Pb concentration were high and frequent consumption of these rice samples may lead to bioaccumulation of these metals in our body which may lead to serious health implications.

Keyword: heavy metal, rice, toxicity, health, tolerable weekly intake.