Organ-Specific Accumulation and Health Risk Assessment of Aliphatic and Polycyclic Aromatic Hydrocarbons in Tilapia zillii

Abstract

The Escravos River, located in Nigeria's Niger Delta, is severely impacted by chronic hydrocarbon contamination arising from oil exploration, refining, and gas flaring activities, raising substantial ecological and human health concerns. This study quantified aliphatic and polycyclic aromatic hydrocarbons (PAHs) in Tilapia zillii, a key dietary fish species, to elucidate tissue-specific accumulation patterns, biomarker responses, and associated health risks. Sixty specimens were collected across dry and wet seasons, and muscle, liver, kidney, and gill tissues were analyzed using GC-MS in accordance with US EPA procedures. Health risk indices including estimated daily intake (EDI), hazard quotient (HQ), toxic equivalency (TEQ), and excess lifetime cancer risk (ECR) were studied, while Monte Carlo simulations (10,000 iterations) and sensitivity analysis addressed uncertainty in exposure parameters. Total PAH concentrations ranged from 192.96 ± 0.45 to 313.43 ± 0.67 mg/kg, surpassing international maximum residue limits. Benzo(a)pyrene levels in muscle (20.95 mg/kg) exceeded EU/WHO permissible limits by over four orders of magnitude. Biomarker assays revealed elevated CYP1A and EROD activity alongside reduced SOD and CAT levels, indicating oxidative stress and metabolic activation of PAHs. The 95th percentile ECR (1.28 × 10-3) exceeded the USEPA carcinogenic threshold (1 × 10-4), confirming high lifetime cancer risk for frequent consumers. Sensitivity analysis identified BaP concentration and fish ingestion rate as primary determinants of risk. T. zillii from the Escravos River bioaccumulates carcinogenic hydrocarbons to hazardous levels, corroborated by biochemical biomarkers of sublethal stress. These findings emphasize the need for urgent dietary advisories, enforcement of effluent controls, and long-term biomonitoring of hydrocarbon-polluted freshwater systems.