Assessment of Total Hydrocarbon Concentration in Four Fish Species of Degele Community, Nigeria and Their Dietary Intake in the Populace

Aims: To assess concentration of total petroleum hydrocarbons (TPHs) in four common fish species of Degele community, Nigeria and estimate their dietary intake in the populace through the consumption of studied fish species.

Study Design: Factorial design.

Place and Duration of Study: Degele, a fishing community in Sapele, Niger Delta, Nigeria between April to August, 2010.

Methodology: Four species of fish namely Tilapia (Oreochromis niloticus), Catfish (Clarias gariepinus and Heterobranchus longifilis), and Liza falcipinnis were collected from River Aqurinrin by the help of local fishermen. Fish were samples were stored at -20°C until further analysis. The scales (O. niloticus) were sloughed off and muscle tissues were dissected. Gas chromatography with flame ionization detector (GC-FID) was used for the evaluation of TPHs. Dietary intake concentration was calculated by multiplying the PAHs concentration measured in each species of fish by the per capita consumption for Nigeria.

Results: The concentration of aliphatic hydrocarbon in Clarias gariepinus ranged from non-detectable level of 0.001 to 46.7±16.7 µg/kg; wet weight.; Heterobranchus longifilis (0.001 to 42.7±17.4 µg/kg; wet weight); Oreochromis niloticus (0.001 to 1123.70±952.10 µg/kg; wet wt); Liza falcipinnis (0.001 to 29.0±1.4 µg/kg; wet wt). The highest level of aliphatic hydrocarbon concentration was obtained in Oreochromis niloticus. The less carcinogenic polyaromatic hydrocarbon of lower molecular weight (LMW PAHs) was detected with clearly observed naphthalene and its substituents in all the studied fish species. The more carcinogenic high molecular weight (HMW) PAHs (BaA, BbF, BkF, BaP,and InP) were not detected in the fish samples analysed. There was significant difference (P = 0.05) in the ΣAliphatic and ΣPAHs concentrations among the fish species. However, the levels are below EU recommended limit of 2µg/kg;wet weight for edible fish. The average intake of PAHs through fish consumption was calculated to be 0.02 – 0.94 mg/kg;body weight/day (O. niloticus), 0.02–0.12 mg/kg;body weight/day (C. gariepinus), 0.12–0.16 mg/kg;body weight/day (H. longifilis) and 0.14–0.58 mg/kg;body weight/day (L. falcipinnis). O. niloticus contributed to the highest intake.

Conclusion: The observed levels of TPH in fish species from this study indicate that River Aqurinrin in Degele community is not highly contaminated with petroleum hydrocarbons. Therefore, Degele community is less exposed to carcinogenic health risks associated with the consumption of the studied fish. However, continuous monitoring programme should be formulated and conducted to ensure that the concentrations of petroleum hydrocarbons is within the baseline levels established in the present study.