Copper Clad Pans
Copper-clad pans are made of a copper core that is sheathed in a different metal, usually stainless steel. These pans are considered reasonably safe because the copper heats up to a high temperature and generally does not harbor bacteria. Copper is toxic unless taken in minute amounts, but the stainless steel sheath protects food from tainting. Take care when scrubbing copper-clad pots so that the steel coating is not damaged to reveal any copper.
Enamel-coated pans, also known as French casseroles, are made of cast iron, coated with white porcelain. Regular cast iron pans have been found to leach some iron into food and the enamel coating alleviates this problem. As with the copper-clad pots, you must be careful not to chip or crack the coating on the pan, so that the iron is not exposed. The higher priced your enamel cookware is, the less likely it is to scratch or chip.
Stainless steel is not as ideal as its copper-clad cousin, but it is a less expensive and relatively safe choice. Stainless steel can leach nickel, but because steel is relatively inert, only a very small amount of nickel can be transferred to your food, and the alloy is not particularly harmful to humans in trace amounts. There are concerns about steel scratching and holding on to bacteria, so be careful not to scour steel pans with abrasive cleaners or brushes.
Regular aluminum pans can leach metal, especially if they are damaged, but anodized aluminum pans are much safer. Anodized aluminum pans are made by a process in which they are submerged in an acidic solution which is then exposed to an electric current. As a result, the aluminum is coated in a thin layer of aluminum oxide. The process reduces the alloy that is leached onto food and also makes the pan resistant to scratches and dents that cause bacteria problems.