Polycyclic Aromatic Hydrocarbon Concentrations in Water, Sediments, and Biota (Oreochromis niloticus and Penaeus monodon) from the New Calabar River, Buguma, Niger Delta, Nigeria

The concentrations and distribution of the 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were determined in surface water, bottom sediment, liver tissue of Nile tilapia (Oreochromis niloticus), and whole tissue of black tiger prawn (Penaeus monodon) collected from three locations (upstream, midstream, and downstream) along the New Calabar River at Buguma, Rivers State, Nigeria, over two sampling events. PAH analysis was performed by gas chromatography–mass spectrometry. Cancer risk was estimated using the benzo[a]pyrene toxic equivalency quotient (BaPTEQ) approach and the incremental lifetime cancer risk (ILCR) model, with an ingestion rate of 0.2 kg/day representative of a Niger Delta fishing community. The PAH profile across all matrices was dominated by low molecular weight compounds (2–3 rings), particularly phenanthrene, fluorene, anthracene, fluoranthene, and pyrene, indicating petrogenic contamination consistent with illegal artisanal refining activities in the area. Benzo[a]pyrene was not detected in any sample. Among the high molecular weight PAHs, benzo[a]anthracene was the most widely distributed, detected across all matrices in both sampling events, and consistently exceeded USEPA permissible limits. Benzo[a]anthracene contributed over 97% of the total BaPTEQ in edible tissues. ILCR values in Sampling 1 were below the 10⁻⁶ threshold for both fish liver (1.46 × 10⁻⁸) and prawn (6.67 × 10⁻⁹), indicating negligible cancer risk. In Sampling 2, however, ILCR values for fish liver (1.41 × 10⁻⁶) and prawn (1.88 × 10⁻⁶) exceeded the 10⁻⁶ threshold, indicating low but potentially significant cancer risk requiring monitoring. These findings demonstrate that dietary exposure to carcinogenic PAHs through consumption of fish and shellfish from this river presents a measurable health risk.