Leachable Lead: Overview

Toby Jug with lead glaze; V&A museum; ca 1782

Lead continues to lead the parade of prevalent and toxic art materials.

In November, the Food and Drug Administration (FDA) released the following fact sheet on Lead in Ceramic Ware.  Leachable lead in food ware is a important concern, and leachable lead levels are newly revised.  Potters and ceramicists should take note of the FDA revised guidelines as well as the California warnings and action filed against manufacturers who have not met these levels.  See the accompanying article on the California warnings.
Reducing Exposure to Lead from Ceramicware
-FDA Backgrounder, November, 1991

Since the 1930s, the Food and Drug Administration has acted to protect the public from the hazards associated with excessive exposure to lead.  These efforts, which have focused on lead from sources such as agricultural chemicals, lead-soldered cans, and glues for ceramic ware, have resulted in a substantial dietary lead exposure.  The daily lead exposure for infants and children today is about one-tenth what it was ten years ago.

In its continuing program to reduce the public's exposure to dietary lead, the FDA has revised its guidelines to lower the levels of lead that may leach from ceramic ware used to hold and store food.  The revised levels reflect the agency's increased concern about the health consequences of human exposure to lead.  The FDA is also advising ceramic ware manufacturers to maintain careful quality control to minimize or eliminate the leaching of lead from their products.  While the agency believes that most ceramic ware does not present a significant health hazard, it is concerned that some products can contribute lead to the diet. Consumers can take precautions to minimize lead exposure from ceramic ware.

Lead has long been recognized as a toxic substance.  Adverse health effects - such as damage to the liver and kidneys, and to the nervous, reproductive, cardiovascular, immune, and gastrointestinal systems may result from exposure to lead over months or years.  Infants and children are most sensitive to lead exposure.  Several recent studies have indicated that lead causes behavioral and performance deficiencies in children exposed to the substance at levels below those that produce physical effects.

Pregnant women should avoid lead exposure because of the sensitivity of the fetus to lead.  Recent studies have shown that exposure of the fetus to low levels of lead in the mother's blood can impair fetal development and cause low birth weight.
The Hazards of Lead in Ceramic Ware
Lead glazes are used to produce a smooth, lustrous, and sometimes decorative coating on ceramic ware such as pottery, earthen ware, bone china, and porcelain.  The nonporous, glazed surfaces permit easy cleaning and contribute to good sanitation.  If a glaze is improperly formulated or applied, however, or if the piece is improperly fired during the manufacturing process, large quantities of lead may leach from the glaze into food contained in the vessel.  Even with properly glazed pieces, some lead may migrate to food.  However, the amounts will be much lower than with poorly glazed pieces.
The FDA samples and tests for lead leaching from imported and domestic ceramic ware sold in this country.  However, the agency cannot check all ceramic ware.  In 1986 alone, 873 million pieces of ceramic ware were imported into the United States in 46,000 shipments.  In addition, products that enter the country through informal channels, such as those brought by travelers from abroad, are not monitored by the FDA.  These products may pose the greatest potential hazard because they may not have been produced using appropriate quality control procedures for glazing.
New Lead Levels
In 1971, the FDA set informal guidelines for levels of lead leaching from ceramic ware products.  These levels were tightened in 1979.  They are now being further reduced because new information shows that lead can adversely affect the fetus, young children, and adults in amounts well below those previously believed harmful.  The guideline levels for lead leaching from ceramic ware are being reduced as follows:

    •    from 7 to 3 parts per million (ppm) for plates, saucers, and other flatware
    •    from 5 to 2 ppm for small hollowware such as cereal bowls, but not cups and mugs
    •    from 2.5 to 0.5 ppm for cups and mugs
    •    from 2.5 to 1.0 ppm for large (greater than 1..1 liters) hollowware such as bowls, but not pitchers
    •    from 5 to 0.5 ppm for pitchers.

The amount of lead leaching from the pieces is measured in a standard test contact of the piece with an acid solution for a 24-hour period.
Guidelines for Consumers
The particular piece of ceramic ware and the conditions and patterns of its use affect the amount of lead to which a consumer may be exposed.  More attention should be given to items used daily rather than infrequently.

Acidic foods such as orange, tomato, and other juices; tomato--based products; wines; and vinegar-containing foods cause more lead to be leached into the food than do non-acidic foods such as water or milk.  Similarly, more lead will leach into hot liquids, such as coffee, tea, or tomato soup, than into cold beverages and foods.  For example, frequent use of a lead-glazed mug for hot beverages is likely to increase lead exposure.  Longer contact times, as when liquid foods are stored, may increase lead leaching.  On the other hand, foods that are dry, non-acidic, and have little contact with the container, such as pretzels or candy, are not a problem.
If you don't know whether a particular item is lead-glazed, follow these guidelines to minimize the potential for exposure to lead, especially for children and pregnant women:

    •    Do not store acidic foods in ceramic ware.
    •    Limit the use of antiques or collectibles for food or beverages to special occasions.
    •    Stop using items that show a dusty or chalky gray residue on the glaze after they are washed.
    •    Follow label directions on ornamental ware that states, "Not for Food Use - Plate May Poison Food.  For Decorative Purposes Only."
    •    Do not store food or beverages in vessels that are highly decorated on the inside.
    •    Be alert to conditions and patterns of use of ceramic ware that can increase lead exposure.

Acidic foods, high temperatures, and increased time of contact with food contribute to greater leaching of lead from the container to the food.  Frequent use of the piece will also increase exposure to lead.
Testing for Lead
The amount of lead leaching from suspect items, such as highly decorated ceramic ware, can be tested in a commercial laboratory, but these tests are relatively expensive.
The FDA is aware of three manufacturers marketing test kits for
consumers to use at home.  These kits were designed to test ceramic ware relative to the former guidelines, however, and their ability to detect lead release at the new, lower levels cannot be ensured.  Nevertheless, they continue to be valuable for identifying items that release larger amounts of lead and should be considered for checking suspect items.  These kits and their approximate costs are:

    •    Test for Lead in Pottery ($25) and The FRANDON Lead Alert Kit ($29.95), Frandon Enterprises, Inc., P.O. Box 300321, Seattle, WA, 98103; telephone (800) 359-9000.
    •    LeadCheck Swabs ($30), HybriVet Systems, Inc., P.O. Box 1210, Framingham, Mass. 01701; telephone (800) 262-LEAD.
    •    LEADCHECK II ($25), distributed by Michigan Ceramic Supplies, 4048 Seventh Street, P.O. Box 342, Wyandotte, MI. 48192, telephone (313) 281-2300.

If a newly purchased ceramic item is found to release significant quantities of lead, notify the local FDA office, listed in the blue pages of the phone directory under the Department of Health and Human Services, or call the FDA headquarters at (301) 443-4667.
Additional Reading
(For reprints, contact your local FDA office or write FDA, HFE-88, 5600 Fishers Lane, Rockville, MD 20857, telephone (301) 443-3170):
    •    "Getting the Lead Out," FDA Consumer, July-August 1991, pp. 26-31.
    •    "An Unwanted Souvenir: Lead in Ceramic Ware," FDA Consumer, December 1989-January 1990, pp. 18-21.
    •    Lead in Ceramic Ware," FDA Drug Bulletin, November 1988, pp. 31-32.
    •    "Pretty Poison: Lead and Ceramic Ware," FDA Consumer, July-August 1987, pp. 6-9.

Art Hazard News, Volume 14,  No. 6, 1991

This article was originally printed for Art Hazard News, © copyright Center for Safety in the Arts 1991. It appears on nontoxicprint courtesy of the Health in the Arts Program, University of Illinois at Chicago, who have curated a collection of these articles from their archive which are still relevant to artists today.