POLYCYCLIC AROMATIC HYDROCARBONS AND HEAVY METALS CONTAMINANTS IN PALM OIL FROM SELECTED AREAS OF NIGER DELTA REGION, NIGERIA

Abstract

The polycyclic aromatic hydrocarbon (PAH) components are often targets in environmental check. It is usually relied upon as an indicator of heavy environmental pollution. The study investigates the concentration levels of seventeen (17) environmental priority PAHs as well as the determination of the concentration levels of Cd, Pb, Ni, Cr, Cu, Fe, Zn, Mg, Ca, K, and Na in palm oil locally produced in some selected areas of Niger Delta region of Nigeria. The samples were hydrolyzed using 0.5M methanolic potassium hydroxide and the PAHs extracted in n-hexane. The PAHs extracted were cleaned up using solid phase extraction (SPE), separated and quantified using analytical HPLC (Agilent Tech. 1120 Compact LC, while concentrations of 11 elements were determined using Atomic Absorption Spectrometer and Flame Photometer. Result obtained showed that the concentrations of PAHs detected in the palm oil varied significantly (p< 0.05). The LMW-PAHs ranged from< 0.001 to 56.79μg/kg, while HMW –PAHs range from <0.001 to36.66 μg/kg. The flu, pyre, fluo, were LMW-PAHs while, chry, BaA, BaP, Bkf, DBahP, B,g,h, B,g,h,iP, are HWM-PAHs predominant in the nineteen (19) samples analyzed. The apportionment sources indicate that Vehicular or auto emission, diesel and gas, diesel engine, and wood and coal combustion are the major sources of PAHs in the study areas. The margin of exposure (MOE) indicates the potential risk of some samples (C, D, E, F, H, I, M, N, O, P and R) are below the standard of 10,000 ng BaP kg bw day-1. Source apportionment showed that emission from heavy vehicles, gas discharged, wood and coal combustion are the reasons for PAHs contamination. Also, the mean concentrations of the metals (mg/100g) in the samples ranged from (<0.001 to 1.15) Cd; (0.03 to 0.78) Pb; (0.25 to 1.03) Ni; (0.03 to 0.45) Cr; (0.70 to 1.15) Cu; (7.23 to 24.20) Fe; (3.73 to 17.03) Zn; (14.90 to 232.00) Mg; (71.03 to 146.15) Ca; (21.23 to 91.53) K and (12.28 to 46.15) Na. The estimated daily intakes (EDIs) of Cr, Cd, Ni and Pb were within the minimum tolerable daily intake (MTDI). However, due to combined metal hazard quotients (ΣHQs) from other food sources in the area, which may be higher than one (1), the metals may pose a considerable risk to local inhabitants due to consumption of combined foods from the area (fish, vegetable, fruits, etc). The study showed that both LMW-PAHs and HMW-PAHs and some selected metals were significantly present (p < 0.05). The potential consequences of dietary exposure could include bio-accumulative deleterious effect such as carcinogenic effect and genotoxicity. Interestingly, it also provides information on the dietary intakes of essential metals, as the level of Pb and Cd are still within dietary recommended intake.