Polycyclic aromatic hydrocarbons and trace metals contents of Pterocarpus Mildbraedii and Ocimum gratissimum grown near markets within Aba Metropolis, Nigeria: An evaluation of dietary intake risks

Abstract

Consuming contaminated vegetables is one recognised method that people are exposed to polycyclic aromatic hydrocarbons (PAHs) and trace metals (TMs). For this reason, it is important to constantly keep an eye out for these potentially fatal toxins in vegetables. Eighteen PAHs and TMs were investigated in the leaves of Pterocarpus mildbraedii and Ocimum gratissimum grown near Afule, Ahiaohuru, and Umuocham market locations within Aba metropolis using high-performance liquid chromatography (HPLC) for PAHs while an Inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) for trace metals and Hg was analysed using a Cold Vapour Atomic Fluorescence Spectrophotometer (CV-AFS). The results from the study showed that Afule samples gave (mg kg-1 PAHs) 6.84, 8.12; Ahiaohuru samples gave (mg kg-1 PAHs) 11.34, 17.68; and Umuocham samples gave (mg kg-1 PAHs) 0.17, 0.16 for P. mildbraedii and O. gratissimum leaf samples, respectively. As per the estimated data, the concentrations of trace metals in vegetables and soil are found in the range of 0.432–6.03 mg/kg for Al, 0.133–0.867 mg/kg for Cd, 0.003–0.840 mg/kg for Co, 1.400–2.933 mg/kg for Cr, 0.933–4.533 mg/kg for Cu, 132.233–198.197 mg/kg for Fe, BDL–0.0002 mg/kg for Hg, 0.002–0.004 mg/kg for Li, 8.007–19.067 mg/kg for Mn, 0.533–1.633 mg/kg for Pb, 0.300–0.667 mg/kg for V, and 2.050–6.103 mg/kg for Zn. The trace metals observed are compared to the literature reported values. It was discovered that the average metal concentrations were below the FAO/WHO maximum allowable values. Every metal in the study had estimated daily intake (EDI) values that were lower than the reference oral dosage (RfD) for that metal. The health risk index (HRI), target health quotient (THQ) and hazard index (HI) values for both vegetables were much lower than 1 implying that the exposed population is safe from potential toxic metal.