Migration kinetics of cadmium and lead from ceramic mugs

Cadmium and Pb are heavy metals of high concern owing to their impacts on human health. In this study, the migration of Cd and Pb from both the interior and exterior (lip area) surfaces of new and second-hand ceramic mugs has been measured as a function of time over a 24-h period using 4 % acetic acid. Via regression analysis, data were fitted with a diffusion equation, yielding reaction rate constants and 24-h migratable concentrations. Migration was more significant from the external surfaces for both metals, and especially where the rim area was overglazed with decorative Cd sulphoselenide pigments. Here, diffusion rate constants ranged from 0.04 to 23.8 μg [L(h)^1/2]⁻¹ for Cd and about 0.2–185 μg [L(h)^1/2]⁻¹ for Pb, and exterior concentrations after 24 h ranged from about 0.2–115 μg L⁻¹ for Cd and 1.2–934 μg L⁻¹ for Pb. By comparison, diffusion constants for interiors were always < 10 μg [L(h)^1/2]⁻¹ and interior 24-h concentrations did not exceed 9 μg L⁻¹ for Cd and 6 μg L⁻¹ for Pb. Although migratable concentrations from interiors were well within present EU regulatory limits, proposals to drastically reduce these could prove challenging for the ceramics industry. Concentrations migrating from the lip area are not currently regulated in the EU but appear to result in greater exposures that warrant further consideration and investigation.