An Evaluation of Polycyclic Aromatic Hydrocarbons in Hemichromis fasciatus (Peters, 1857) from an Urban Reservoir in Southern Nigeria

Abstract

The concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) were analysed in Hemichromis fasciatus netted from the Ikpoba reservoir in Benin City, Nigeria, using Gas chromatographic technique, in order to evaluate the potential ecological risk of these organic pollutants on the investigated ecosystem. The mean concentrations in μg/kg of 2-methynaphthalene,1-methynapthalene, acenaphthylene, acenaphthene, flourene, phenanthrene, anthracene, flouranthene, pyrene, benzo(a)anthracene, benzo(k)flouranthene, benzo(b)flouranthene, indeno(123-cd)pyrene and benzo(ghi)perylene in the fish species were 0.0034, 0.0025, 0.0047, 0.0007, 0.0093, 0.0023, 0.0178, 0.0147, 0.0039, 0.0185, 0.0014, 0.0152, 0.0012 and 0.0027respectively. There were significant differences (P < 0.05) in the mean concentrations of PAHs in fish between stations with the exception of phenanthrene and indeno (123 cd) pyrene. The peak concentrations of the PAHs in H. fasciatus were generally observed in the month of August with the exception of benzo(ghi)perylene, whose peak concentration was observed in October. The Hazard Quotient values for PAHs ranged from 0.0014 for acenaphthene to 0.037 for benzo(a)anthracene while the estimated daily intake of PAHs ranged from 0.000028 mg/person/day for acenapthene to 0.00074 mg/person/day for benzo(a)anthracene. The Toxic Equivalency Quotient (TEQ) values ranged from 0.000014 for benzo(k)flouranthene to 0.00185 for benzo(a)anthracene. The mean concentrations of PAHs detected in H. fasciatus in this study, did not exceed the World Health Organisation (WHO) recommended background concentration of 0.5μg/kg for benzo(a)pyrene in food samples. This finding indicates that the consumption of this fish species by man, does not present an immediate health risk and it is therefore safe to eat as it is relatively free from hazardous levels of PAHs. However, the TEQ values recorded in this study revealed that benzo(a)anthracene poses the greatest potential risk in the reservoir and should thus be closely monitored by relevant authorities in order to avert unwholesome ecological impacts.

Keywords: Polycyclic Aromatic Hydrocarbons, Potential Ecological Risk, Ikpoba reservoir, Nigeria.