Uptake of Thallium by Medicinal Plants: First Data for Romanian Flora and Significance to Human Health

Thallium is one of the most toxic elements, without known biological function in living beings. While contents of other heavy metals like Cd, Hg and Pb are subject to strict limitations in foodstuffs and medicinal plants, and concentrations are routinely checked, in the case of Tl there are no regulations in prime matters intended for phytomedicines, and its monitorization is not performed. The present research provides for the first time data on the Tl content of over 50 species of wild-growing medicinal plants, measured through ICP-MS, and evaluates the results in the context of their significance to human health. Roots contain the highest Tl contents with an average of 25.5μg kg-1 dry weight, being followed by aerial parts, flowers and leaves with 19.3, 17.2 and 16.6 μg Tl kg-1, respectively. The highest Tl content was measured for the Boraginaceous species Echium vulgare, which may be used as a biomonitor of anthropogenic Tl contamination. This study shows that the Tl content of the investigated plants does not pose health risks, provides useful reference data for wild-growing plants from unpolluted sites, and documents the naturally low environmental level of Tl in South Western Romania.