Metal contents in traditional chewing sticks commonly used in Ethiopia: A comparative analysis

African toothbrush sticks have been used for centuries for the maintenance of oral hygiene. This is especially true in developing countries where economics, customs, religion and the availability of oral hygiene tools play a role in their continued use. Chewing sticks are used by the majority of the population in Ethiopia. The aim this study was to determine the levels of essential and non-essential metals in chewing sticks from three plants (Salix subserrata, Sida cuneifolia and Clausena anisata) in samples collected from three selected areas (Muger, Sendafa and Holleta) of Ethiopia. Samples were wet digested with mixture of HNO₃ and HClO₄ at optimized temperature and time. The levels of metals were determined by microwave plasma-atomic absorption spectrometry. The range of mean concentrations of the metals (mg/kg) in the S. subserrata, S. cunnefolia, and C. anisata samples were in the order of Ca (14150-25914) > Fe (514-1191) > Al (103-1263) > Zn (152-196) > Mg (46-102) > Ni (4-160) > Mn (25-78) > Cu (13-20) > Cr (7-8). The accuracy of the optimized procedure was evaluated by analyzing the digest of the spiked samples with standard solution and the percentage recoveries varied from 92% to 104%. The toxic metals Cd and Pb in the plant samples were not detected. Thus, people using “chewing stick” from studied plants are free from the risks of Cd and Pb toxicity.