Surface water samples were collected from the Okpoka Creek, Niger-Delta using the grab samples method and were analytically investigated for petroleum contamination. The liquid-liquid extraction of petroleum hydrocarbons was carried out following standard procedures of U.S EPA 3510; 1664 method and ASTM D3695 -95(2013). The US EPA 3005A method was adopted for acid wet digestion (Aqua regia mixture of concentrated HNO3 and HCl  in ratio 1:3) for toxic heavy metal (HMs) determination. Total petroleum hydrocarbons (TPHs) was analytically identified and quantified with the representative extract (sample) using Gas chromatography mass spectrometry detection (GC-MSD) Agilent Technologies 7890A in adherence to the standard analytical method of U.S EPA 8270;625. Atomic absorption spectrophotometer (AAS) Buck Scientific 210VGP in adherence in to the manufacturer’s specifications was employed for HMs. The recorded elevated levels of the TPHs were significantly above the permissible limit of DPR/EGASPIN and HMs were also overwhelmingly above permissible limits of relevant regulatory agencies. The elevated concentrations of these contaminants of concern provided evidences of severe contamination in the study site and severe threats to environment and human health.

The chronic human health effects of the 17 US Environmental Protection Agency [USEPA] priority pollutants of polycyclic aromatic hydrocarbons [PAHs] were investigated and characterized in petroleum contaminated wastewater discharged indiscriminately into the surface water of Okpoka creek off the upper Bonny River estuary in the Niger-Delta. Collections and sampling were conducted under the standard specifications, ethics and protocols of U.S Environmental Protection Agency (EPA). The liquid-liquid extraction of Petroleum contaminated wastewater samples were conducted in accordance with standard procedure of US EPA. Identification and quantification of 17 PAHs were performed by Gas chromatograph with Mass spectrometric detection (GC/MSD) in accordance with standard analytical method of US EPA. The result showed presence of Naphthalene [2.6000 mg/l], Acenaphthylene [8.0000 mg/l], Acenaphthene [0.0000 mg/l], Fluorene [9.0008 mg/l], Anthracene [0.0000 mg/l], Phenanthrene [0.0000 mg/l], O-Terphenyl [5.0200 mg/l], Fluoranthene [1.1000 mg/l], Pyrene [8.0000 mg/l], Benz[a]anthracene [1.0900 mg/l], Chrysene [0.0000 mg/l], Benzo[b]fluoranthene [10.0000 mg/l], Benzo[k]fluoranthene [0.0000 mg/l], Benzo[e]pyrene [0.0000 mg/l], Dibenzo [a,h] anthracene [4.0100 mg/l], Indeno[1,2.3-cd]pyrene [9.2000 mg/l] and Benzo[g,h,i]perylene [3.0000 mg/l]. The results also indicated that some of the 17 PAHs constituents were above the PAHs World Health Organization [2003] maximum permissible limits (MPL) in drinking water (0.0020 mg/l) with 64% and 35.29% below the MPL. The low molecular weights of PAHs [LPAHs] were 40.60% and high molecular weights of PAHs [HPAHs] were 59.40%. Human teratogenic PAHs [9.09%], Human mutagenic PAHs [24.24%], Human carcinogenic PAHs [24.24%], Human genotoxic PAHs [18.18%] and other toxics [24.24%]. Thus, total PAHs concentrations gave 61.2800 mg/l of the petroleum contaminated wastewater sample.