Occurrence, Health Risk and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Borehole Water Around Fuel Stations in Owerri West Local Government Area, Imo State, Nigeria

Abstract

Borehole water is a major drinking water source in Owerri West LGA, Imo State, Nigeria, but fuel stations within residential areas raise concerns over groundwater contamination by polycyclic aromatic hydrocarbons (PAHs). This study assessed concentrations of the 16 USEPA priority PAHs in borehole water near three fuel stations (Nekede, Orogwe, Obinze), evaluated health risks to adults and children, and identified probable contamination sources. Twenty-seven samples were collected in the dry season from fuel-station and nearby residential boreholes (25–625 m away). Physicochemical parameters were analyzed per APHA (2017); PAHs were extracted (USEPA Method 3510C) and quantified by GC-MS. Health risk was assessed using the USEPA (2014) deterministic model, with source apportionment via diagnostic ratios and PCA. All physicochemical parameters met WHO/USEPA limits. Total PAHs (Σ16PAHs) ranged from 0.112–0.217 mg/L, with benzo(a)pyrene exceeding the USEPA limit (0.01 µg/L) in all fuel-station boreholes. Hazard quotients were below 1, but benzo(a)pyrene cancer risk (7.15×10⁻⁵ adults; 1.67×10⁻⁴ children, Nekede) exceeded the USEPA threshold (1×10⁻⁶), with children ~2.3 times more at risk. Diagnostic ratios indicated predominantly pyrogenic sources with petrogenic contribution from fuel leaks. Despite meeting potability standards, the water posed unacceptable carcinogenic risk, warranting setback regulations and household treatment.