Assessment of heavy metals leachability from traditional clay pots “inkono”and “ibibindi” used as food contact materials

Abstract

The clay pots may transfer ones of their constituents into foodstuffs when they are coated with glazes which are said to contain heavy metals like Pb and Cd. This study was conducted to determine if traditional clay pots (unglazed) can also behave the same way. Leachate from the clay raw pulp material was initially analysed for heavy metals determination followed by assessment of heavy metals leached from the final product “clay pot”. Leaching tests were conducted using acetic acid 4 % and juice from foodstuffs mostly cooked or brewed in clay pots (beans, tomatoes, carrots and banana juice). The concentrations of heavy metals in leachates were determined by flame atomic absorption spectrometry. By cooking beans in clay pots, the concentrations in leachates were in ranges of 0.385-2.692, 3.654-3.846, 470.000-682.692 and 1.731-1.923 mg/kg for Pb, Cd, Fe and Zn respectively while during cooking tomato-carrot sauce in these clay pots, these concentrations were found in ranges of 0.000-0.192, 1.731-3.076, 1023.077-2005.769 and 0.000-1.923 mg/kg for Pb, Cd, Fe and Zn respecetively. By brewing banana liquor in these clay pots, the concentrations in leachates were respectively evaluated in ranges of 0.224-1.092, 0.000-0.196, 37.676-57.990 and 0.000-2.204 mg/L for Pb, Cd, Fe and Zn. Results of this study showed that Pb, Cd and Fe were transferred in considerable amounts which exceeded the safe limits in food established by WHO. As heavy metals are toxic in trace concentrations, due to bioaccumulation, traditional clay pots constitute a public health hazard when used as food contact material. However, as the geochemical properties of clay are different from regions to region and the techniques of making them differ, further studies should be undertaken to check the leachability of these heavy metals from different type of pots.