Polycyclic Aromatic Hydrocarbons (PAHs) in Waters and Sediments of Oil Impacted Communities in Ogbia, Bayelsa State: Concentrations, Health and Ecological Risks Assessment

Abstract

Polycyclic aromatic hydrocarbons (PAHs) in water and sediments from oil-impacted communities in Ogbia Local Government Area, Bayelsa State, Nigeria, were investigated to determine their concentrations, spatial variability, source characteristics, and associated ecological and human health risks. Water and sediment samples were extracted using liquid–liquid and Soxhlet extraction methods, respectively, with dichloromethane (DCM) and analyzed by gas chromatography–mass spectrometry (GC–MS). Total concentrations of the sixteen priority PAHs (∑16PAHs) in water ranged from 91.40 to 191.30 µg/L (mean: 128.44 ± 40.81 µg/L), while sediment concentrations ranged from 15,572.35 to 46,043.75 µg/kg (mean: 27,258.72 ± 12,137.95 µg/kg). High-molecular-weight PAHs dominated over low-molecular-weight compounds in both matrices, with dibenzo[a,h]anthracene, benzo[a]pyrene, benzo[k]fluoranthene, benzo[b]fluoranthene, and indeno[1,2,3-cd]pyrene being the most abundant, indicating aged petroleum-related contamination. Statistical analysis revealed high spatial variability, with coefficients of variation of 33.4% and 44.5% for water and sediments, respectively, reflecting heterogeneous anthropogenic inputs. A strong positive correlation (r > 0.90) was observed between total PAH concentrations and total toxicity equivalence quotients (∑TEQs) in sediments, confirming that elevated PAH burdens directly translated into increased toxic potency. Sediment ∑16PAHs values largely fell between effects range-low and effects range-median guidelines, suggesting a possible-effect range where adverse ecological effects may occasionally occur. Non-carcinogenic risk assessment showed hazard indices below unity for both dermal contact and ingestion pathways, indicating negligible non-cancer risks. However, incremental lifetime cancer risk values for both adults and children exceeded the 1.0 × 10⁻⁶ benchmark, implying elevated carcinogenic risk, particularly from dermal exposure. The persistence, variability, and strong toxicity–concentration relationship observed in sediments highlight their role as long-term secondary sources of contamination and underscore the urgent need for remediation and strengthened environmental management in the affected communities.