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Avoid Lead Glazed Pottery

A handmade Mexican olla or clay pot can be a beautiful work of folk-art and a pleasure to cook with, but unfortunately, it can also be poisonous. While lead-based paint, not lead-glazed pottery is the leading cause of lead poisoning in the US, for some populations, lead-glazed pottery and folk-remedies containing lead are significant factors in high levels of lead in the blood.

Throughout the world, most handmade pots are made of earthenware clay -- the type that our common clay flowerpots are made of. Since earthenware clay is by nature porous, it must be glazed if it is to hold liquid. Lead-based glazes offer many advantages to the potter: they are inexpensive, efficient and permit colorful decorative effects even at the low temperatures most folk potters fire their ware to. They offer only one disadvantage: they are poisonous. Lead compounds can be absorbed into the potter's skin and fumes from the firing process can poison the potter. For this reason, lead poisoning has been known throughout history as "the potter's disease." But the potter is not the only one in danger. If the glaze is not well formulated and not fired to high enough temperature, lead can leach from the glaze into foods the pottery is used for. Acidic foods such as fruit juice, wine or vinegar can leach lead from a glaze quickly, but even a bland pot of beans can collect some lead compounds as the heat of cooking accelerates the process.

How much lead leaches out of a lead-glazed utensil depends on how the pot was made. Lead glazes fired in high heat pose less danger than low-fire ware because higher heat causes more of the lead to fuse with non-lead compounds. Again, lead may be a minor component of the glaze, or it may be covered with a harmless non-lead glaze which effectively seals off the poison compounds. A lead-glaze on the outside of a utensil poses less risk than a pot with lead-glazed cooking-surfaces.

Should you worry about your everyday dishes? Probably not. Modern ceramics made by reputable commercial firms are usually harmless. Such firms have never used lead glazes, have given them up decades ago, or place them under safe glazes where they are rendered harmless. Neither does the problem lie with commercially imported pottery. Major importers of pottery such as Pier One and Williams-Sonoma voluntarily prohibit the sale of lead-glazed items in their stores. In addition, FDA regulations mandate that imported items not safe for food-use must have a permanent stamp to that effect, usually on the bottom of the piece. Likewise, most craft or hobby-potters have turned to non-lead glazes so you can safely use handmade pottery.

The problem centers chiefly around pottery made by artisans or folk-potters in other countries and brought into the U.S. by individuals for their personal use. In some homes, the family cazuela or cooking pot is an heirloom, passed from mother to daughter. Getting the family to abandon it is not always easy, however, that is what must be done because lead is an insidious poison which accumulates in the body.

Lead poisoning affects small children more than adults because of their low body mass. It can damage young nervous systems and cause physical and mental problems.

In Mexico, the government crafts-agency, FONEART is teaching local potters to glaze pottery with non-lead glazes and to fire lead-glazed pots at higher temperatures to minimize risk. However, reversing centuries of tradition takes time. Meanwhile, we can still buy, collect and display and use folk-art pottery, but not for food.

Home-testing kits for lead compounds can check pottery, paint, soil or other materials for lead compounds but they should not be relied upon exclusively. The kits range in price from $5 to $30 and vary in sensitivity and ease of use. Consumer Reports evaluated the kits in their July, 1995 issue. At the top of their list was the Lead Zone kit described as "very easy to use." This kit is available at Home Depot and Builders Square hardware stores and at Target stores. It costs $5 for 6 tests.

The Houston Department of Health and Human Services Childhood Lead Poisoning Prevention Program can test your children from six months to six years of age for blood lead levels. Call them at 713-794-9349.