Determination of benzo(a)pyrene and heavy metals contamination in smoked Lates niloticus and Oreochromis niloticus from Lake Victoria

Abstract

Fish remains to be an important source of proteins in developing countries including Tanzania. Fish processing methods like smoking aim at improving the shelf-life of smoked fish as well as taste and aroma. During smoking, smoke by-products from different materials used as source of heat are deposited on the fish. The deposited by-products include the carcinogenic polyclic aromatic hydrocarbons (PAHs) and heavy metals. Benzo(A)pyrene has been used as a marker for the occurrence of carcinogenic PAHs. The purpose of this study was to assess the different materials that are used in fish smoking practices, determine the levels of benzo(A)pyrene, mercury, cadmium and lead in smoked Lates niloticus (Nile Perch) and Oreochromis niloticus (Nile Tilapia) from different fish smoking areas in Mara and Mwanza regions. A total of 32 fish smokers were interviewed to assess the material used and how they use them to smoke their fish. This was followed by collection of 32 smoked fish samples for laboratory analysis of heavy metals (mercury, Cadmium and Lead) and concentration of benzo(A)pyrene. The findings of this study indicated that people engaged in smoking fish in the study areas are mostly using firewood and charcoal as their source of heat. There were no cases of the use of plastic materials. The laboratory results indicated that mercury and cadmium were not detected in all fish species while lead was detected at a mean concentration level of 0.28 μg/kg which is below the recommended level of 0.3 μg/kg as set by the EU. This indicated that smoked fish from Mara and Mwanza did not contain heavy metals to a harmful level. The Mean benzo(a)pyrene concentration detected was 4.79 μg/kg. This amount is higher compared to a level of 2 μg/kg set by the EU in 2014. There is therefore, a need for people who smoke fish to use other improved methods which will lower the levels of benzo(a)pyrene and the Government to have a continuous monitoring plan for these contaminants.