Toxic metal accumulation in medicinal plants collected from roadside environments: Implications for human consumption

Abstract

Medicinal plants can absorb heavy metals from the environment, which may pose risks to human health when consumed. These elements can negatively affect plant growth and metabolism by disrupting key physiological and biochemical processes. This study aimed to evaluate environmental conditions and determine the concentrations of selected minerals (Ca, K, Na and Mg) and heavy metals (Cr, Ni, Pb, Zn, Cu, Mn and Fe) in three medicinal plant species [Silybum marianum (L.) Gaertn., Achillea millefolium L. and Convolvulus arvensis L.], as well as to assess potential human health risks associated with their consumption. Plant samples were collected from roadside areas in the municipality of Prizren, Kosovo, and elemental concentrations were measured using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The results revealed species-dependent variability in both mineral and heavy metal concentrations. S. marianum exhibited elevated levels of several essential minerals, whereas C. arvensis showed a higher accumulation potential for chromium and nickel, exceeding the permissible WHO/FAO limits. Correlation analysis indicated both synergistic and antagonistic relationships between minerals and heavy metals, suggesting shared sources of contamination and element-specific uptake mechanisms. Health risk assessment based on estimated daily intake (EDI), target hazard quotient (THQ) and hazard index (HI) values indicated no significant non-carcinogenic risk for adult consumers under the assumed consumption scenario. Nevertheless, the accumulation of certain toxic elements highlights the importance of regular environmental monitoring and preliminary assessment of medicinal plants harvested from roadside environments. Future studies should also include heavy metal content and physicochemical properties of soils from harvesting sites to better understand plant–soil interactions and contamination pathways.