Procter Silex, Precise Heat and VitaClay sell slow cooker models that are lead-free. Other brands, including KitchenAid and Cuisinart, also carry some slow-cookers that are lead free, but consumers should contact the manufacturers to ask about specific models before purchasing them.
Most slow cookers use glazed ceramic inserts, which is the part of the appliance that comes in contact with the food. In many cases, the glaze contains small amounts of lead that can leach into the food at temperatures as low as 80 degrees Fahrenheit. While the Food and Drug Administration calls lead leach levels as small as 1 mcg/mL acceptable for slow cookers, the Mayo Clinic states that "small amounts of lead can cause lead poisining," and that lead poisoning is often a cumulative issue since it builds up in the body over time.
Slow cookers made of metal or glass do not contain lead, but they are difficult to find. Precise Heat does make a metal model, but Elite Gourmet no longer sells its glass model. Disposable slow cooker inserts create a barrier that prevents lead from leaching into the food, but some of them contain BPA. Reynolds slow cooker liners are BPA free, making them a good choice for consumers who want to keep toxins away from their families.