Determination of benzo[a]pyrene levels and establishment of limit of detection in smoked and oil fried Lates niloticus

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds included in the European Union and US Environmental Protection Agency (USEPA) priority pollutant list because of their mutagenic and carcinogenic properties. Several studies have shown that exposure to benzo[A]pyrene (BaP), a member of the PAHs increases the risk of cancer. PAHs have been the subject of much concern in the recent years due to their toxic potential. They are known as highly stable contaminants of foodstuffs and are found frequently in the environment, water and fish. Maximum residue limit (MRL) has been set by the European Commission at 5μg/kg in fish. However, despite the wide use of smoking and deep frying of fish in western Kenya there is limited information on the BaP residues in fish. This study investigated the effects of firewood smoking and oil frying on the BaP levels in Nile perch (Lates niloticus) sold in western Kenya. Sampling was done three times in ten randomly selected markets. The methodology involved BaP extraction with cyclohexane and dimethylformamide-water, clean up on silica gel column and determination by high performance liquid chromatography (HPLC) using fluorescence detection. Variable levels of BaP were detected ranging from 7.46 to 18.79μg/kg in smoked fish and 4.17 to 11.26μg/kg in oil fried fish. These levels were further compared with the regulatory limits. All smoked fish samples were found to be over the acceptable limit/ MRL of 5μg/kg set by the European Commission while only 20% of the oil fried samples were within the acceptable limit. The limit of detection (LOD) was established at 0.011μg/kg and defined as the smallest amount of BaP that was reliably detected from the background of the HPLC equipment. At the same time these findings indicate that firewood smoking resulted in higher levels of BaP contamination as compared to oil frying. The study also concluded that consumers of these products are exposed to levels that are above the MRL and hence a health risk.