Migration of metals from ceramic food contact materials. 2: Migration kinetics under various conditions and the influence of conventional thermal heating and microwave heating on migration

The release of metals from ceramic ware has raised public concerns, especially in the case of lead. The Directive 84/500/EEC monitors the compliance of ceramic food contact articles within the European Union. It sets the migration limits of lead and cadmium, and the corresponding testing conditions. The present research was aimed at investigating the migration kinetics of different metals under a range of testing conditions beyond those stated in the Directive and at evaluating the protectiveness of the Directive testing conditions. This research analyzed the release of metals from ceramic articles under a series of temperatures for a variety of contact times with 4% acetic acid and 5 g/L citric acid. It compared the release of metals under the Directive conditions and under cooking conditions. Overall, the amounts of metals increased steeply with time at the beginning of the migration test, after which the growth was less pronounced and arrived at a plateau. A square root dependence between the amount released and migration time was evidenced, providing an appropriate estimate of migration at low temperatures and short times. The amounts of metals released under the cooking conditions significantly exceeded those released under the Directive testing conditions, indicating that the current Directive testing conditions may not be adequately protective. Testing conditions can be specified on the basis of the use of ceramic ware, and a migration test under cooking conditions is probably required for ceramic cookware.