Mineral and Heavy Metal Contents of some Shellfish in Bonny River, Rivers State, Nigeria: Public Health Implication

Abstract

Background: Shellfish serve as sources of food nutrients to the consumers and provide means of livelihood, especially to riverine people. As much as important these values are, consumption of shellfish can also present health hazards to consumers, especially if the water where they live is contaminated with industrial wastes. The level of minerals and heavy metal content of shellfish from Bonny River in Niger Delta region of Nigeria has not been fully explored. Objective: This study was aimed at providing public health information on mineral and heavy metal contents of shellfish from Bonny River and compared the values with Provisional Tolerable level set by the Joint FAO/WHO Codex Committee on Contaminants in Foods. Materials and Methods: This was a descriptive and analytical study. Randomly selected samples of the five most commonly consumed fresh shellfish from Bonny River, which included prawns, crabs, periwinkles; oysters and cockle were purchased from local sellers in all the riverside markets. Standard methods of analysis, using the AOAC were adopted. Selected minerals and heavy metals content were determined using Flame Photometer and Atomic Absorption Spectrophotometer. Data were analyzed using frequency counts and student t-test for inferential statistics. Results: The ranges of minerals and heavy metals contents from all the samples were: sodium 178.6-280.5mg/100g, potassium 399.5-600.7mg/100g, calcium 8.0-9.2mg/100g, magnesium 4.7-5.1mg/100g, iron 1.4-1.6mg/100g, zinc 5.9-6.5mg/100g and chromium 0.5-0.6mg/100g; whereas the range values of heavy metals include: arsenic (0.04-0.10mg/100g), lead (0.22-0.33mg/100g), mercury (0.04-0.08mg/100g) and cadmium (0.07-0.10mg/100g). The concentration of analyzed heavy metals exceeded the permissible international standards, with the exception of cockles, which did not exceed the maximum level of cadmium. High levels of heavy metal in the flesh of these shellfish may be linked with the level of these metals in Bonny River. Conclusion: These findings signify potential public health problem for the consumers. Awareness should be created through community-based health education approaches on dangers associated with the consumption of shellfish from this river.