Heavy metals and essential elements in table salt extracted from Bahi wetlands in Central Tanzania

Abstract

Salt from Bahi wetlands is allegedly containing high concentrations of heavy metals since the wetlands are in the proximity of the prospective uranium mining sites. This means Bahi salt could be an important route through which salt consumers are exposed to high concentrations of heavy metals. This study has analysed 50 salt samples of Bahi salt in order to determine the concentrations of both heavy metals and essential elements using the Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). Analytical results show that apart from Na and Cl, Bahi salt is composed of several elements including heavy metals such as Cr, Cd, Pb, Th and U. The salt also contains essential elements such as Mg, K, Ca, Mn, Fe, Co, Zn and Br. The mean concentrations of Cr, Cd, Pb, Th and U ranged from 20 - 25μg/g, 3.8 – 8.85 μg/g, 2.29 – 5.8 μg/g, 6.22 – 15.8 μg/g and 6.5 – 9.12 μg/g respectively. All these toxic elements were in higher concentrations than the recommended maximum tolerable limits (MTL). Meanwhile the daily intake rate of essential elements due consumption of Bahi salt leads to the hazard index (HI) greater than 1 for children. This implies that unless purified, Bahi salt may be unsafe for children. Thus, both salt producers and responsible authorities at Bahi wetlands should collaborate to introduce suitable production methods ensuring effective salt purification before it reaches its consumers.