Heavy Metals Concentration in Selected Rice Brands Sold in Port Harcourt, Nigeria

Introduction: Potentially harmful substances contaminating agricultural soil and crops pose a risk to human health and food safety. One of the main elements causing pollution in agriculture is heavy metals. Heavy metals can be found in cereal grains including rice, which absorb and store toxic metals including Lead (Pb), Cadmium (Cd), and Arsenic (As).

Objective: the objective of the study was to determine the concentration of heavy metals in selected rice brands sold in Port Harcourt, Nigeria.

Methodology: A total of ten samples of five local rice designated as Lo1, Lo2, Lo3, Lo4, and Lo5 and five foreign rice designated as Fo1, Fo2, Fo3, F04, and F05 were used for the study. Heavy metals were determined using Perkin Elmer atomic absorption spectrophotometer in Flame atomic absorption mode.

Results: The concentration of heavy metals (µg/kg) in selected local rice, showed that arsenic in Lo2 (4.20) was significantly higher than other rice brand while Lo3 (7 x 10-5) had the lowest value. The rice with the highest Pb concentration was Lo2(89.73). The concentration of Cr was significantly lower in Lo4 (1.3 x 10-4) in comparison to other groups. Finally, for Cd, Lo2 (7 x 10-5) had the lowest value, which was significant. While for foreign rice, arsenic concentration was significantly lower for Fo4 (0.88 µg/kg) in comparison to other groups. For Pb levels (µg/kg), Fo3 (61.30) and Fo4 (61.30) had higher concentrations. Fo2 (23.76) and Fo3 (25.76) were significantly lower than Fo1 (33.96) and Fo5 (47.63) for Cr levels. And for Cd, Fo1 (1.0 x 10-4) was lower than Fo2 (2.50), Fo5(2.70), Fo3(6.10), and Fo4(5.63). Overall, the concentration of Arsenic was lowest in Lo3 (7 x10-5) and highest in Lo2 (4.20), Lead was lowest in Fo1 (6.7 x 10-5) and highest in Lo2 (89.73), Chromium had the least value in Lo4 (1.3 x10-4) and the highest value in Fo5 (47.63) while cadmium was least in Fo2 (1 x 10-4) and highest in Fo3(6.10), all of which were significantly different (p<0.05).

Conclusion: the concentration of heavy metals in the samples was in no particular preference of either foreign or local rice. Although the concentration of the heavy metals was below the standard permissible limits, caution needs to be taken to avoid future possible bioaccumulation.