Occurrence, Distribution and Food-Safety Implications of Priority Polycyclic Aromatic Hydrocarbons in Edible Grains Consumed in Enugu State, Nigeria

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are persistent contaminants generated mainly through the incomplete combustion of fossil fuels, biomass and other carbonaceous materials. Grains may become contaminated during cultivation, transportation, processing, storage and marketing. This study investigated the occurrence, distribution and food-safety implications of sixteen United States Environmental Protection Agency priority PAHs in edible grains consumed in Enugu State, Nigeria. Wheat, oat, Bambara nut, millet and guinea corn were collected from three markets representing Enugu East, Enugu West and Enugu North senatorial zones, with three replicate samples of each grain collected from each market. Samples were extracted by Soxhlet extraction using dichloromethane/n-hexane (1:1, v/v), purified by silica-gel column chromatography and analysed using gas chromatography-mass spectrometry (GC-MS). Instrument calibration with certified PAH standards and identification based on retention times and mass spectral characteristics supported quality control. All sixteen priority PAHs were detected. Total Σ16 PAHs ranged from 1.523 mg/kg in oat to 3.365 mg/kg in guinea corn, following the order guinea corn > millet > Bambara nut > wheat > oat. HMW PAHs accounted for 79.54–80.24% of total PAHs, while LMW PAHs contributed 19.76–20.46%. LMW/HMW ratios ranged from 0.246 to 0.257, indicating consistent HMW predominance. This profile is consistent with possible combustion-related or pyrogenic influences, although molecular-weight ratios alone cannot establish definitive source attribution. Benzo[k]fluoranthene was the most abundant PAH, while acenaphthene and acenaphthylene were among the least abundant. The observed PAH burden has food-safety implications and highlights the need for routine monitoring, improved post-harvest practices, quantitative dietary exposure assessment and further source-apportionment studies.