Comparative assessment of the levels of some heavy metals in virgin and used water plastic bottles and sachets in Nigeria

Abstract

Plastic bottles and sachets for water packaging manufactured from 3 different factories in Minna, Niger State of Nigeria were collected and analyzed to determine the concentration of heavy metals (Mn, Fe, Cu, Zn, Co, Cd, Pb and Ni) in them. The plastics are categorized as virgin and used plastics. The plastics were first processed by dry ashing and then digested with analar grade HNO3 in accordance with CPSC-CH-E 1002-08 method. Thereafter, the samples were quantitatively analyzed using AAS. The total mean and the standard deviation of the concentration of Mn, Fe, Cu, Zn, Co, and Ni in all the virgin plastic bottles are given as: 18.3±0.86 μg/g, 333.3±1.47μg/g, 8.3±0.68 μg/g, 889.2±1.98μg/g, 72.0±0.10μg/g and 2.5±0.10 μg/g, respectively. The total mean and the standard deviation of the levels of Mn, Fe, Cu, Zn, and Pb in the virgin plastic sachets are: 53.3±1.19μg/g, 1150.8±3.08μg/g, 206.7±2.80μg/g, 1048.3±1.91μg/g and 630.0±0.83μg/g, respectively. Cd and Pb were not detected in the virgin bottles while Cd and Co were not detected in the virgin sachets. Generally, the concentrations of these metals in the virgin plastics were found to be very low when compared with their concentration in used plastics. It was also noted that the detected heavy metals have lower concentration in virgin plastic bottles than in virgin sachets. It is concluded that environmental pollution with heavy metals arising from various human activities accounted for the relatively high concentration of these heavy metals in used plastics. On the other hand, the high concentration of these metals in plastic sachets was attributed to the colorants used to provide manufacturers’ information directly on the sachets unlike plastics bottles, which bears such information on stick label.