Contemporary PAH contamination in the Niger Delta mangrove ecosystem: Implications for ecological and human health...

This study presents the first integrative assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments from the Nembe mangrove ecosystem (Niger Delta, Nigeria), evaluating contamination levels, probable sources, and associated ecological and human health risks. Sediment samples collected from three stations were analysed for the 16 priority PAHs using gas chromatography-flame ionization detection (GC-FID). Fourteen PAH compounds were detected, with a mean concentration of 4728 ± 2745 mg/kg, far exceeding both the Nigerian intervention limit (4 mg/kg) and international guideline values. Multivariate statistical methods were employed for source apportionment, and the 5th and 95th percentile health risks were estimated using Monte Carlo simulation. Diagnostic ratios, and correlation analysis indicated mixed petrogenic (oil-derived) and pyrogenic (combustion-related) inputs, consistent with oil spillage events and biomass burning activities. Ecological risk assessment showed that several PAHs exceeded the effect range-median (ER-M) thresholds, suggesting a high probability of adverse biological effects. The total 5th and 95th Percentile carcinogenic risk were 2.20 × 10^-3 and 3.73 × 10^-3 for children, and 1.60 × 10^-3 and 2.77 × 10^-3 for adults, respectively, all exceeding the United States Environmental Protection Agency maximum acceptable risk threshold (>1 × 10^-4). Dermal contact and ingestion were identified as the dominant exposure pathways. Overall, the findings reveal severe PAH contamination in Nembe mangrove sediments, with substantial ecological and public health implications. Targeted public health interventions, stricter regulation of PAH sources, and sustained seasonal monitoring are urgently needed to mitigate oil spills, reduce human exposure, and guide remediation and policy development.