HAZARDS FROM LEAD IN CERAMIC DINNERWARE: ANTIQUITY TO THE YEAR 2000

Ralph W. Sheets, Department of Chemistry, Southwest Missouri State University, Springfield, MO 65804, USA, e-mail: rws080f@mail.smsu.edu

ABSTRACT

Lead has been used in ceramicware for thousands of years, but it is only within the past century that serious attempts have been made to protect consumers from ingestion of lead leaching from ceramic dinnerware into food. In the U. S., the Food and Drug Administration is responsible for ensuring the safety of food and dinnerware. In 1971 guidelines were established for maximum concentrations of lead that can be leached from ceramic ware. These limits were lowered in 1979 and again in 1991 as more toxic effects of lead were discovered. The FDA has also set provisional total tolerable intake levels (PTTILs) of lead for pregnant women and for children younger than 6 years. Several recent studies have found that dishes in use in U.S. homes can release lead into food in amounts that could cause these intake values to be exceeded.

INTRODUCTION

Lead has been used in ceramic glazes and decorations for thousands of years, and its use continues today. Both old and new dinnerware can present health hazards. The amounts of lead ingested by humans from dinnerware are typically small, but even small amounts of lead may have health consequences. In 1972 the Joint Food and Agricultural Organization/World Health Organization Committee on Food Additives (JECFA) recommended that the long term daily intake of lead by adults from food and water not exceed 430 mg/day. In 1993 this provisional tolerable weekly intake (PTWI) for adults was withdrawn and the PTWI for infants and children was extended to all age groups (JECFA, 1993). The current PTWI is 0.025 mg/kg body weight. This is equivalent to 250 mg/day for a 70-kg adult, but only 71 mg/d for a 20-kg child. There is evidence that use of dishes commonly found in U.S. households could result in lead intakes exceeding these values (Sheets, 1997). The U.S. Food and Drug Administration (FDA) has set provisional total tolerable intake levels (PTTILs) of lead from all sources at 25 mg/day for pregnant women and 6 mg/day for children younger than 6 years (FDA, 1997). Several of the studies reported below have found that dishes in use in U.S. homes release lead into food substances in amounts that could result in these recommended intake values being exceeded.

HISTORY OF LEAD USE IN DINNERWARE

Lead compounds are used in three different ways in the dinnerware industry: as fluxes in glazes, as fluxes for fusing decorations to glazes, and as colorants in the glazes and decorations themselves. Lead was used in glazes in Syria and Babylonia as early as 1000 B.C.E. and had found use in Chinese glazes by 500 B.C.E. During the Middle Ages lead glazes were used in Persia and Turkey, and by the 12th Century their use had spread to Europe (Geller and Creamer, 1939). Lead has been used as a flux in Majolica and Lusterware glazes in the Near East, Europe, and Mexico, and in Raku glazes in Japan. Lead glazes were by far the most widely used kinds of glazes throughout all of Europe after 500 C.E. and in America since 1500 C.E. Although pottery had been made by Europeans in North America since colonial times, the real beginnings of the American dinnerware industry occurred with the production of a dense white ware known as white granite or ironstone in the mid-19th century. Since that time, and throughout most of the 20th century, lead-glazed dinnerware has been the stock-in-trade of U.S. manufacturers. In the 1980s and 90s extensive research has gone into development of leadless glazes, and much of the current U.S.-produced dinnerware is made without lead. Lead glazes are still common on new dinnerware, however, especially on much of the ware imported from countries that include China, Mexico, and Italy.

FEDERAL REGULATION OF LEAD INTAKE AND EXPOSURE

Use of lead in the dinnerware industry has a major drawback: it is extremely toxic to humans. Early research into dangers of lead-glazed ceramicware has been documented by Geller and Creamer (1939), and by the International Lead and Zinc Research Corporation (ILZRO, 1971). Studies of lead glazes carried out during the 1930s - 1960s (ILZRO, 1971) culminated in the regulation of lead in dinnerware by the FDA. In 1971 guidelines were established for maximum permissible concentrations of lead that can be leached from ceramic ware. These limits (action levels) were lowered in 1979 and again in 1991 as more toxic effects of lead were discovered. In no case may a dish release more than 3.0 mg/mL of lead when subjected to the standard leaching procedure, test method ASTM C-738 (24-h leaching with 4% acetic acid). The FDA routinely inspects dinnerware imported into this country for harmful content of lead, and since 1990 has detained shipments of lead-containing ceramicware from 21 European and Asian countries. The agency reported that in Fiscal Year 1993 about 15% of all imported dinnerware lots analyzed were found to be in violation of FDA regulations for lead or cadmium (FDA, 1998) It is impossible to test every dish entering the country and, as a result, dishes containing excess lead sometimes reach retail outlets and are offered for sale to the public. If this situation is discovered, a recall of the product is issued by the importer. Because the initial distribution of the dinnerware is usually widespread, thousands of lead-contaminated dishes may be sold before the recall is initiated. These items may remain in use in homes for several years. Since 1990 at least 36 recall actions for excessive levels of leachable lead and/or cadmium in ceramic dinnerware have been reported by the FDA (FDA, 1990-1999). Some of the dinnerware had been distributed nationwide in undetermined amounts that certainly exceeded tens of thousands of pieces.

A different kind of problem, one not involving enforcement, arises in the case of the millions of old dishes now in household use or being offered for sale at flea markets, antique stores, garage sales, etc. The FDA monitoring of lead in dishes did not begin until the early 1970s and, as a result, dinnerware made in or imported into the U.S. before this time was not regulated for lead content. Recent investigations reveal that much of the dinnerware made before 1971 can release lead in concentrations higher than permitted by FDA regulations (Sheets, 1997). High lead concentrations are found in both everyday dishes and in fine china sets, including dinnerware made in many Asian and European countries as well as the U.S.

STATE REGULATION OF LEAD IN CERAMICWARE--PROPOSITION 65

The state of California is concerned that FDA regulations do not go far enough in protecting its citizens. In November 1986, California voters approved an initiative dealing with exposure to toxic chemicals. The legislation, officially called The Safe Drinking Water and Toxic Enforcement Act of 1986, but better known as Proposition 65, includes sections that regulate the amount of lead that can be leached from ceramicware. Proposition 65 does not ban any dinnerware from sale, but it does require that all dinnerware which exposes users to lead at concentrations higher than "no significant risk" levels must contain warning labels (Anonymous, 1993). Warnings are required on dishes that release more than 0.226 mg/mL lead for flatware, and 0.100 mg/mL for hollowware as determined by the ASTM C-738 test. In November 1991 the California Attorney General and the Environmental Defense Fund (EDF) filed a lawsuit against 10 of the world's leading manufacturers of ceramic dinnerware charging them with violating Proposition 65 requirements. In February 1993 the companies agreed to pay a total of $2.3 million to California and the EDF in an out-of-court settlement (Anonymous, 1993). The EDF has published a pamphlet, What You Should Know About Lead in China Dishes that includes a listing by manufacturer, brand, and pattern of all dinnerware that is known to meet Proposition 65 standards. The listing is available on the internet (http://www.edf.org/pubs/Brochure/LeadInChina/ index.html) and is continuously updated. In 1998 the list contained more than 8000 dinnerware patterns from 40 manufacturers and their subsidiaries.

CURRENT STATUS OF LEAD IN DINNERWARE

Even after promulgation of standards by the EPA in 1971, lead in dinnerware remained a health problem, and research on lead release from dinnerware has continued. Some investigations have concerned physical and chemical properties of glazes while others have dealt with the action of leaching agents themselves.

It has also been determined that hazardous amounts of lead can be leached from ceramic decorations (McCauley, 1982), and there has been a revival of interest in extraction of lead from overglaze-decorated dinnerware in the 1990s. Sheets (1997) investigated effects of acids and bases on overglaze-decorated dinnerware. Schellenberg (1990) and Sheets (1997) reported that successive leachings of a dish on a single day led to decreasing concentrations of lead in leachates, but allowing the dish to stand overnight (Sheets, 1997) or for several days (Schellenberg, 1990) resulted in leachate lead levels reaching or exceeding the initial levels. It was found that some overglaze-decorated dishes released lead exceeding FDA limits even after as many as 20 consecutive 24-h leachings with 4% acetic acid (Sheets, 1997).

Studies of lead release from ceramic dinnerware into acidic and basic food substances showed that more than 60,000 mg of lead was released from a single plate under standard testing conditions, and that, for a large sampling of dinnerware, values typically ranged from 2000-2500 mg of lead (Sheets, 1997). A comparison of reported lead releases with recommended chronic lead intake values for the general populace (not more than 25 mg/kg body weight of lead per week) (JECFA, 1993) indicates the magnitude of risk involved in regular use of such dishes for food preparation and storage. In some instances ingestion of as little as 25 mL of liquid left in a dish for 24 h would provide amounts of lead comparable to suggested maximum daily intakes and to estimated actual daily intakes from all sources (Sheets, 1997). Ingestion of as little as 1 mL of liquid from many of the dishes tested would exceed the FDA's PTTILs for young children and pregnant women.

Enforcement of California Proposition 65 standards has resulted in reduction or elimination of leachable lead in dinnerware by most of the world's major manufacturers. Current problems in the U.S. stem from three sources: 1) glazed ceramicware brought into this country by returning tourists, especially from Mexico and Italy; 2) use of new dinnerware, especially from China, that does not meet FDA limits, but which has slipped undetected through inspection; and 3) use of antique and collectible dinnerware for preparation, serving, or storage of foods (Sheets, 1997).The FDA has cautioned against storing acidic foods in ceramicware, recommended limiting use of old and collectible dinnerware to special occasions, and warned the consumer to be suspicious of highly-decorated ceramicware. This advice is still useful to the general public today.

REFERENCES

Anonymous (1993), Prop 65 News, 7:1-2.

FDA (1990-1999), FDA Enforcement Reports for 5/1/90; 8/14/90; 10/9/90; 6/11/91; 6/19/91; 7/23/91; 5/20/92; 9/16/92; 11/25/92; 3/10/93; 3/17/93; 4/4/93; 4/28/93; 9/29/93; 11/3/93; 12/1/93; 12/15/93; 1/19/94; 4/13/94; 8/24/94; 1/11/95; 1/18/95; 8/2/95; 8/9/95; 11/1/95; 1/31/96; 5/15/96; 11/20/96; 12/26/96; 3/19/97; 3/31/99; 8/24/99. Washington, DC, U.S. Food and Drug Administration.

FDA (1997), FDA Consumer, August, 1993). Updated [Online] http://www.verity.fda.gov/search97cgi/s97...rt%3D21%26ResultCount %3D10&hlnavigate=ALL (February, 1997).

FDA (1998), Import Alert No. 52-08, Revision 11/04/96, Attachment 4/23/98. Washington, DC, U.S. Food and Drug Administration.

Geller RF, Creamer AS (1939), J. Am. Ceramic Soc., 22:133-140.

ILZRO (1971), Lead Glazes for Dinnerware. New York, International Lead Zinc Research Organization.

JECFA (1993), Evaluation of Certain Food Additives and Contaminants, 41st Report. Geneva, Switzerland, Joint Food and Agricultural Organization/World Health Organization Expert Committee on Food Additives.

McCauley RA (1982), Glass Technology, 23:101-105.

Schellenberg KA (1990), Virginia J. Sci., 41:28-32.

Sheets RW (1997), Sci. Total Environ., 197:167-175.