Dietary Daily Intake, Toxic Equivalent Concentrations, and Excess Cancer Risk of Polycyclic Aromatic Hydrocarbons in Tympanotonus fuscatus Harvested from Woji– Elelenwo Creek, Rivers State, Nigeria

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental contaminants of concern due to their toxicity, carcinogenicity, and potential for bioaccumulation in aquatic organisms. This study evaluated the concentrations, sources, and human health risks of PAHs in periwinkle (Tympanotonus fuscatus) from the Woji–Elelenwo Creek, Niger Delta, Nigeria. Periwinkle samples were analyzed for sixteen priority PAHs using standard analytical methods, while dietary exposure and carcinogenic risks were assessed using established risk assessment models. Results showed that high molecular mass PAHs predominated over low molecular mass PAHs, indicating the persistence of combustion-derived hydrocarbons within the creek ecosystem. The mean total PAH concentration was 0.472 mg/kg, while carcinogenic PAHs contributed 0.388 mg/kg of the total burden. Fluoranthene recorded the highest mean concentration (0.098 ± 0.156 mg/kg), followed by benzo(b)fluoranthene (0.070 ± 0.157 mg/kg), chrysene (0.056 ± 0.114 mg/kg), and benzo(a)anthracene (0.056 ± 0.114 mg/kg). The PAH4 index and total toxic equivalency (TEQ) were 2.08 × 10⁻² mg/kg and 6.89 × 10⁻² mg/kg, respectively, with dibenz(a,h)anthracene contributing most to the toxic burden. Estimated dietary daily intake values were below international guideline limits, while the excess cancer risk (6.51 × 10⁻⁷) indicated negligible carcinogenic risk to consumers. Diagnostic ratios suggested predominantly petrogenic contamination with minor pyrogenic inputs linked to hydrocarbon-related activities. Although current health risks associated with periwinkle consumption appear low, the occurrence of carcinogenic PAHs highlights ongoing hydrocarbon pollution in the creek. Continuous environmental monitoring and pollution control measures are therefore recommended. This study provides baseline data for environmental management and risk assessment in the Niger Delta.