Polycyclic Aromatic Hydrocarbons Contamination in Selected Rice Grains Sold in Port Harcourt, Nigeria

Background and Objective: Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants and a significant group of carcinogens. Rice has been shown to contain certain PAHs, which could be a result of environmental and soil pollution, as well as manufacturing and cooking methods. The study’s objective was to assess the concentration of polycyclic aromatic hydrocarbons in rice grains; both local and foreign, sold in Port Harcourt, Nigeria. Materials and Methods: Five samples each of local and foreign rice designated as L₀₁, L₀₂, L₀₃, L₀₄ and L₀₅ for the local rice samples and F₀₁, F₀₂, F₀₃, F₀₄ and F₀₅ for the foreign rice samples were used. For the determination of polycyclic aromatic hydrocarbon, gas chromatography with a flame ionization detector, GC-FID (HP 6890) was used. Values are expressed as Mean±Standard Deviation and ANOVA (SPSS version 21) was used to assess significant differences within groups at p<0.05. Results: The concentrations of polycyclic aromatic hydrocarbons (PAHs) in local rice showed that naphthalene concentration (×10^–2 μg/kg) was highest in L₀₁ (1.027) and L₀₂ (0.596), L₀₃had benzo[a]anthracene (0.824), L₀₄ was Indeno[123-cd] pyrene (0.618) and L₀₅ had anthracene (0.787) with the highest value. The concentrations (×10^–2 μg/kg) of PAHs with the highest concentration in the foreign rice samples are as follows; 2-methylnaphthalene in F₀₁ (1.016), benzo[a]anthracene in F₀₂ (0.984), F₀₃was acenaphthylene (0.81), F₀₄ was fluorene (0.698), while F₀₅ was naphthalene (0.825). The Σ₁₆ polycyclic aromatic hydrocarbons (×10^–2 μg/kg) in both local and foreign rice grains was as follows: L₀₅ (5.05)>F₀₃ (4.782)>L₀₁ (4.573)>L₀₃(4.488)>F₀₄ (4.407)>L₀₄ (4.018)>F₀₂ (3.714)>F₀₅ (3.052)>F₀₁ (2.715)>L₀₂ (2.328). Conclusion: The Σ₁₆ PAHs were in no pattern, there were concentrations in both local and foreign rice samples with the least concentration in L₀₂, although they were lower than the permissible limits. This indicates long-term possible contaminations could occur and since some PAHs are carcinogenic, regulatory bodies need to monitor the level of PAHs in rice sold in Port Harcourt.