Health Risk Assessment of Heavy Metals in Selected Culinary and Medicinal Herbs: A Case Study of Rose, Thyme, Turmeric, Chamomile, and Fennel

Plants are a significant source of heavy metals, with humans consuming large quantities of plants daily. Evaluating the levels of certain heavy metals (Pb, Cr, Cd, and Ni) is crucial for determining the potential risks associated with commonly used medicinal plants. This study aimed to estimate the concentrations of heavy metals in Curcuma longa, Rose rubiginosa, Thymus vulgaris, Foeniculum vulgare, and Matricaria chamomilla, utilizing Atomic Absorption Spectrophotometer. The results revealed that the concentrations of the studied heavy metals varied across the plant species. The concentrations of Pb, Cd, Cr, and Ni in the studied plants ranged between 2.5*10-5 - 0.44, 0.24 – 0.43, 0.40 – 0.84, and 4.83 – 4.82 respectively. While the Pb and Cr concentrations remained under the permissible limits set by WHO/FAO (Pb = 10 and Cr = 2 mg.kg-1) in all studied herbs, Cd and Ni showed exceedance in concentration in all herbs except Cd in Chamomile was below the addressed limit. Furthermore, the relationship between the studied heavy metals among the herbs in soil was mainly determined by the origin (natural or anthropogenic) and other factors such as environmental factors, genetic makeup as well as plant uptake mechanism and affinity for certain heavy metals. Moreover, the Tue key analysis at the p-value ≤ 0.05 showed no significant differences among the studied herbs for the studied heavy metals. On the other hand, the Health Risk Index has shown that HQ and HI for all studied metals were < 1, which means pose no risk to human health. Additionally, the carcinogenic risks were all under acceptable limits.