Porcelain was first used in China in the 600s, but Europeans did not unlock the mystery of manufacturing it until almost the 18th century. Porcelain is made of clay and additives that have included glass, feldspar and even bone, which is then shaped and baked at high heats. Glazes are added at the end, sometimes to make the porcelain waterproof, and sometimes to add stunning colors to the porcelain. It is the lead that was used in these glazes that represent a danger.
In the 1970s and1980s, researchers discovered that the lead used in the glazes could leach into the foods served on porcelain dishes. The FDA set standards for lead use in dinnerware, but most domestic manufacturers have stopped using lead altogether in their glazes.
How It Leaches Out
The lead used in the glazes can leach out, particularly if the food served on the dishes has a high acid content. The acid in orange juice and tomato juices, for example, seeps into the glaze and dissolves the lead. The lead mixes with the food remaining on the plate so that as you eat, you are absorbing lead.
Lead poisoning from porcelain is rare, but lead can be toxic. It is particularly dangerous to children and pregnant women. Because children are still growing, they absorb more lead, and it stays in their systems longer. High levels of lead in children can cause learning problems, behavioral difficulties and struggles with coordination.
To keep your contact with lead to a minimum, do not store food in dishes with ceramic glaze. Because hot liquids can increase leaching of lead, pregnant women in particular should avoid drinking hot beverages out of ceramic mugs. If porcelain dishes show any signs of a chalky residue, do not use. Even though they may be family heirlooms, it is better not to use antique porcelain dishes.
The Yellow Triangle
Turn over your porcelain dishes and check for the symbols on the back. If there is a yellow triangle, it means that the manufacturers have tested the product in accordance with California's Proposition 65, and it is possible that the dish will leach lead.