Ralph W. Sheets

Extraction of lead, cadmium and zinc from overglaze decorations on ceramic dinnerware by acidic and basic food substances

Dinnerware decorated with overglaze designs can release toxic metals into food substances in amounts high enough to constitute health hazards. When dishes made in the US before 1970 were filled with 4% acetic acid for 24 h, lead concentrations of up to 610 micrograms/ml and cadmium concentrations of up to 15 micrograms/ml were measured. Acetic acid leachates from more than half the dishes tested for lead (78 of 149) contained levels exceeding the US Food and Drug Administration (FDA) allowable concentration of 3.0 micrograms/ml. One-fourth of dishes tested for cadmium (26 of 98) exceeded the FDA limit of 0.5 microgram/ml. High concentrations of lead, cadmium and zinc were also released into 1% solutions of citric and lactic acids. Significant amounts of these metals were extracted by basic solutions of sodium citrate and sodium tripolyphosphate, as well as by commercial food substances including sauerkraut juice, pickle juice, orange juice, and low-lactose milk. Relative concentrations of lead, zinc and cadmium released depend on the leaching agent used. Citric acid leachates contain higher lead:cadmium and zinc:cadmium (but lower lead:zinc) ratios than do acetic acid leachates from nominally identical dishes. Repeated extractions with acetic acid show that even after 20 consecutive 24-h leachings many dishes still release lead in concentrations exceeding FDA limits.

Release of heavy metals from European and Asian porcelain dinnerware

Samples of porcelain dinnerware manufactured in five European and three Asian countries before the mid-1970s and subsequently brought into the US were subjected to acid leaching tests to investigate the release of heavy metals. Forty-six dishes decorated with decals or hand painted designs applied over the glaze were examined. Included in the selection were dishes from major manufacturers of fine dinnerware (Haviland Limoges, Rosenthal, Noritake) as well as samples from lesser-known or unidentified factories. During 24-h tests with 4% acetic acid, half of the samples (23 dishes) released lead in concentrations exceeding the US Food and Drug Administration (FDA) allowable maximum of 3.0 micrograms/ml and another 17 dishes released lead in concentrations ranging from 0.1 to 2.9 micrograms/ml. Five dishes released cadmium, but only one value exceeded the FDA limit of 0.5 microgram/ml. Zinc, cobalt, copper and chromium were also released by some of the dishes. None of the acetic acid solutions contained measurable concentrations of nickel although this metal, as well as those named above, could be extracted from some samples with 6 M nitric acid. The FDA has not established dinnerware extraction limits for any metals except lead and cadmium. All overglaze-decorated dishes imported into the US before the mid-1970s should be tested for lead release before they are used in the preparation, serving, or storage of food.

Effect of microwave heating on leaching of lead from old ceramic dinnerware.

When samples of pre-1950s U.S.-made ceramic dinnerware, purchased in antique shops and flea markets, were filled with 4% acetic acid or 0.5% citric acid and heated in a microwave oven for 2-5 min, lead was leached in amounts of up to 5 mg per dish. Concentrations of lead in the leachates were not significantly correlated with, and could not be predicted from, concentrations in leachates measured during 24-h room temperature acid leaching tests. Unsafe lead concentrations (>3 microg/ ml) were found in microwave leachates of dishes with uranium-containing glazes, with copper-containing glazes, and with floral over-the-glaze decals. This evidence suggests that use of such dishes to microwave common foods could result in the ingestion of dangerously large amounts of lead.

Relationship between soil lead and airborne lead concentrations at Springfield, Missouri, USA

This study tests whether lead deposited to soil from automobiles during past years in a medium-sized US city (population 150,000) may present a current health risk. It examines the relationship between current soil lead concentrations at nine locations within the city of Springfield, Missouri, and airborne lead levels measured at the same locations during years (1975-1981) when lead emissions from automobiles were much greater than at present. A strong, significant correlation is found between soil and airborne lead levels at eight of the sites (r = 0.91, P < 0.005 for soil lead vs. 1979 airborne lead), in low-traffic areas as well as in areas adjacent to heavy traffic flow. Residual lead concentrations in these soils are relatively low, even for the high-traffic sites, as expected for a medium sized city.

Acid extraction of lead and cadmium from newly-purchased ceramic and melamine dinnerware

Imported dishes can present human health hazards in two ways: (1) dinnerware that contains toxic metals in excessive amounts may gain entry to the US; and (2) imported decorative ceramic plates may be improperly labeled regarding permissible use with food. In the present study, non-random samples of dishes were purchased in new condition in US retail outlets and subjected to 24-h acid leaching tests. Two of 28 patterns of imported ceramic dinnerware were found to release lead in levels that exceed US Food and Drug Administration (FDA) limits, and 10 other patterns released lead in concentrations exceeding California Proposition 65 (CA 65) limits. One imported ceramic dish released cadmium in excess of FDA limits. Samples of new foreign-made melamine (plastic) dinnerware in four patterns released neither lead nor cadmium in detectable concentrations. One of three patterns of imported decorative ceramic plates released lead in concentrations exceeding 2000 micrograms/ml. These plates are not permanently labeled as hazardous and are in noncompliance with FDA regulations.

Use of home test kits for detection of lead and cadmium in ceramic dinnerware

Commercial home test kits are advertised as a convenient means for assessing heavy metal hazards in old ceramic dinnerware. This paper reports investigations carried out with four commercial kits for detection of lead (Pb) and one for detection of cadmium (Cd) on pre-1970s ceramic dishes subsequently subjected to 24-h leaching tests with 4% acetic acid to determine heavy metal release. With the lead kits, fewer than 10% of dishes leaching greater than 3.0 micrograms Pb/ml yielded negative results (i.e. false negatives). When the cadmium kit was used according to manufacturers instructions, 29% of dishes leaching greater than 0.5 microgram Cd/ml yielded false negatives. Home lead test kits appear to be useful for screening of old dinnerware, but the cadmium kit may not be suitable for this purpose.

Airborne lead in the Springfield, Missouri, area during a 19-year period (1975-1993)

Concentrations of airborne lead at Springfield, Missouri, in 1975-1993 have been determined by analysis of particulate material collected on glass-fiber filters during the 19-year period. Nitric acid-soluble lead in 1100 samples collected at a total of 19 monitoring stations was determined by atomic absorption spectroscopy and by differential pulse polarography. Ambient concentrations of airborne lead were found to decrease steadily (by more than 90%) during this period in spite of increases in area population and in automobile traffic. The decrease is significantly correlated with national trends in total emissions of lead to the atmosphere and with US ambient lead levels. Airborne lead from a coal-fired power plant was small compared with that from gasoline burning.

Lead hazards from old ceramic dinnerware

Abstract Lead is found to leach from the glazes of some pre-1950s ceramic dinnerware in concentrations high enough to constitute a health hazard. When orange, uranium-containing glazed dishes made by U.S. dinnerware companies before 1943 were filled with acetic acid solutions comparable to household vinegar, concentrations of up to 350 micrograms of lead per milliliter of leachate (μg/ml) were measured. The values greatly exceed the 3 μg/ml limit allowed by U.S. Food and Drug Administration (FDA) regulations for 24-hour leaching of dinnerware with 4% acetic acid. Chromogen screening tests on 40 orange-glazed dishes manufactured by a total of 16 different U.S. companies showed that all release lead in concentrations exceeding FDA limits. Some blue or blue-green dishes manufactured by U.S. companies before 1950 were also found to release lead in unacceptably high concentrations. These glazes are colored with copper compounds and concentrations of lead leached by acetic acid are strongly correlated with concentrations of leached copper. Dishes of these types are widely collected in the U.S. and are readily available in antique stores and flea markets. These dishes are unsafe and should not be used for preparation, storage, or serving of food.

Accidental contamination from uranium compounds through contact with ceramic dinnerware

Examination of orange-colored dinnerware samples purchased in antique stores and flea markets has revealed the occasional presence of surface uranium compounds that are readily transferred to the hands and clothing. We have further been able to produce soluble uranium compounds on the surfaces of clean dishes by exposing them to household vinegar or bleach. We estimate that handling of a contaminated dish can transfer up to 1-2 becquerels or more of uranium compounds to the hands. Uranium contamination is of concern because the element is not only an alpha emitter but also a chemical nephrotoxin. Although the amount of uranium likely to be ingested as a result of casual handling may be small, it could still exceed by several times the amount occurring in the average diet (about 40 mBq/day). Furthermore, since fresh surface compounds are readily formed, it is possible that a person who regularly handles or eats from uranium-glazed dinnerware can accidentally ingest significant amounts of uranium.

Structural Dependence of Diurnal Fluctuations of Radon Progeny in Residential Buildings

Movement of radon progeny inside houses is a complex process that depends both on atmospheric conditions and on building structure. The indoor working level (WL) monitored in four houses of differing structures shows regular diurnal fluctuations related to solar warming of the atmosphere. In the two houses with full basements, radon is removed by indoor/outdoor pressure-driven airflow, and basement WL varies inversely with outdoor temperature. In the two houses with half basements open to crawl spaces, radon is drawn into the basement faster than it is removed, so that basement WL varies directly with outside temperature. Average WLs in basements are about twice as high as first floor WLs and as much as 18 times as high as outdoor WLs. Each house shows an individual pattern of radon progeny movement throughout the building.