Metal(loid)s in herbal medicines and their infusions: Levels, transfer rate, and potential risks to human health

Since ancient times, communities have widely used herbal medicines and their teas for therapeutic properties. In the present study, the concentration, transfer rate, and potential health risks of metal(loid)s (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Pb, Sr, and Zn) in 30 traditional herbal medicines (ten species from various countries) collected from Persian markets were investigated. The results indicated the wide variations of detected metals in the medicinal herbs. Mn and Sr had the highest concentrations in the herbal medicine and their infusions. Also, Cd levels of five dried plants exceeded the recommended values. Base on the findings of discriminant analysis, the dried Cheeseweed, Hollyhocks, Thymus, Pennyroyal, and Bugloss had the lowest metal levels. Furthermore, Cd in Senna and Marjoram infusions was displayed a carcinogenic risk for children. Considering that some of the studied plants were imported, a high level of Cd in medicinal plants and their products could pose a serious risk to human health worldwide. On the other hand, due to the poor extractability of analyzed metals (transfer rate < 30%), their levels in herbal infusions and their hazard indices were lower than international guidelines for adults. Hence, although preparing water-based extract may be an effective way to reduce the intake of toxic metals from herbal medicines, the presence of toxic metals in infusions may pose a risk to vulnerable groups, such as children.