Polycyclic aromatic hydrocarbons (PAHs) are persistent, carcinogenic contaminants. We tracked the 16 U.S. Environmental Protection Agency (EPA) priority PAHs in surface waters of the Tigris River at five stations spanning 100 m upstream to 1.5 km downstream of Baghdad Medical City’s wastewater outfall during October 2024, January 2025, and April 2025. Samples underwent liquid–liquid extraction (LLE), copper desulfurization, and gas chromatography with flame ionization detector (GC FID) analysis. Total PAH concentrations (Σ16 PAHs) peaked at the sewer outlet in all seasons (up to 31 µg L⁻¹) and declined at 1.5 km downstream to levels close to the pre-sewage discharge point. Site explained 93.75 % of the spatiotemporal variance (p < 0.001). The share of high-molecular-weight PAHs rose from 48 % at the outfall to 67 % after 1.5 km. Total risk quotient (ΣRQ) peaked at 2.5 × 10³ in January, exceeding the safety threshold, while benzo[a]pyrene equivalent toxicity (BaP-TEQ) peaked at 1.9 µg BaP eq L⁻¹. Winter benzo[a]pyrene (0.262 µg L⁻¹) exceeded Dutch and Canadian aquatic criteria by 17–26-fold. Diagnostic ratios trace the origin of PAHs to medical waste and biomass combustion.