Human health risk assessment of heavy metal in common traditional herbs sold in Ibadan markets

Concerns about the safety and quality of African medicinal herbs are increasing due to potential heavy metal contamination, which poses significant health risks. This study aimed to assess the concentrations of heavy metals—including Ca, Mg, K, P, Na, Fe, Cu, Zn, Cr, Cd, Co, Ni, Pb, and Se in 180 traditional herbs sourced from ten local government areas in Ibadan, Nigeria. The herbs were processed using the aqua-regia wet digestion method and analyzed using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Health risks associated with herb consumption were evaluated using metrics such as Chronic Daily Intake (CDI), Hazard Quotient (HQ), Hazard Index (HI), and Target Carcinogenic Risk (TCR). Descriptive and inferential statistical analyses were applied to the data. The findings revealed that the herbs were rich in essential nutrients like Mg, Ca, P, and K, with concentrations ranging from 0.72 × 10⁴ to 2.25 × 10⁴ mg/kg for Mg, 0.25 × 10⁴ to 0.78 × 10⁴ mg/kg for Ca, 0.54 × 10⁴ to 1.71 × 10⁴ mg/kg for P, and 0.07 × 10⁴ to 0.23 × 10⁴ mg/kg for K. This suggests their potential as dietary supplements. However, some heavy metals, such as Cr, Ni, and Pb, were found at levels exceeding safe limits. The TCR values for these metals surpassed the USEPA threshold of 1 × 10⁻⁴, indicating a potential cancer risk for both adults and children. While most metals had HQ values below 1, implying no significant non-carcinogenic risk, some herbs posed higher risks.