Many ceramic and painted dishes manufactured before 1977 contain small amounts of lead. In some cases, lead may leech into food or drinks served in these dishes. While each dose of lead is likely to be minuscule, it is still a serious concern. Lead is a cumulative toxin, which means that it is not excreted from the body and builds up over the entire lifetime of the person ingesting it. Lead has been linked to serious physical and mental damage, particularly in those who were exposed to it as children. Coffee cups are especially vulnerable to lead leaching, as the low melting point of lead makes it more active in the presence of hot liquids. Fortunately, you can easily find out if there is lead in your coffee cups with a home testing kit, available at hardware stores.
Clean the coffee cups you wish to test thoroughly. Once they are clean, rinse them with distilled water. This will prevent environmental factors from causing a false positive.
Swab the inside of the coffee cup with a moist test swab from the lead testing kit. Most non-scratch testing kits will require you to rub the swab over the surface for a minute or two.
Apply the test swab to the testing card. Consult the kit's instructions to translate the results.