Study of Potentially Toxic Metals (PTMS) from Two Nigerian Clays and Related Clay Pottery Used Locally as Foodwares

There is presently lack of data on composition of potentially toxic metals and their leaching from clay based foodwares into food. Therefore, in present study we evaluated the leaching of cadmium, chromium, copper, manganese, nickel, lead and zinc from raw clays and traditional clay posts from two locations, Ara-Ekiti, Ekiti State and Kono-Boue, Rivers State in Nigeria. Samples were digested with aqua regia and analysed using atomic absorption spectrometry and also with energy dispersive X-ray fluorescence. Tap water set at different temperatures (27oC and 100oC) and pH values (4.2 and 9.2) were used to leach the pots. The pH of the raw clays ranges from 2.08–6.50. The order of concentrations is Fe>Mn>Pb>Zn>Ni>Cr>Cu>Cd for both clays and this was consistent with XRF data. The results from this study indicate that Cd, Cr, Cu and Pb were not in leachable forms in clay pots. The concentration ranges of Fe and Mn leached were 0.16–8.37 ppm and 0.08–10.00 ppm, respectively. In all cases the Kono-Boue pots indicated more leached concentrations of metals than Ara-Ekiti pots. It is essential to assess traditional clay pots for leachability of xenobiotics.