The bright orange Fiesta dishware that many Americans use and collect is "hot" -- radioactive -- and could be giving off enough radon gas to pose a significant health risk, a Massachusetts geologist says.
"When we test homes and look for radon, we always suppose it comes from the ground," said Dr. Rudolph Hon of Boston College. "Maybe we need to make the public aware that some of it can be coming from the cabinet."
Fiesta ceramics made before 1972 "should be always considered as suspect" in homes where radon levels are high, concluded Dr. Hon and a graduate student, Christopher Zeman, in a paper presented recently in Binghamton, N.Y., to a meeting of the Geological Society of America.
The dishes' radioactive properties -- gamma ray emissions from uranium-based paint in the bright orange variety -- have been known for decades. The finding that the paint is also producing significant amounts of radon gas is new, Dr. Hon said.
Fiesta dishware sold by the millions in the 1930s and 1940s, and became one of the largest-selling lines in the country. It has recently become popular again among collectors, and is widely available in antique shops and flea markets.
Mr. Zeman, 22, said the study found that a single Fiesta plate in an unventilated, 15-by-15-foot room would produce radioactive radon gas at 28 picocuries per liter -- a concentration seven times the level considered safe by the federal government.
The gas, radon-222, is produced by the gradual decay of uranium-238.
The radon is believed to escape from the plates through microscopic cracks in the glaze. Fiesta ware in other colors is not radioactive, Dr. Hon said.
More than half the radiation to which Americans are exposed each year is believed to come from naturally occurring radon. It is a Class A carcinogen, ranked by the federal government with secondhand tobacco smoke, benzene and asbestos.
Emitted from rocks and soil and accumulated in poorly ventilated homes, radon may be responsible for up to 20,000 lung cancer deaths a year in the United States, according to the U.S. Environmental Protection Agency. However, the National Research Council suggests the EPA's figure may be too high.
The EPA urges property owners to test their homes for radon and reduce exposures to a level of 4 picocuries per liter or below by improving ventilation.
Frank Marcinowski, a health physiologist with the EPA's radon division, said his agency has asked Dr. Hon for more information on his study.
Radon emissions from Fiesta ware are "perfectly feasible," he said. "The isotopes I'm aware of in the Fiesta ware glazing are parent isotopes of radon." If Dr. Hon's radon measurements are accurate, Mr. Marcinowski said, "that level is definitely a cause for concern."
The dishware -- most of it marked "Fiesta" and "Made in U.S.A." on the bottom -- was manufactured by the Homer Laughlin China Co. in Newell, W.Va.
"We believe Fiesta is the largest-selling dinner line in the history of the industry," said David Conley, the company's national sales manager. Twelve million pieces in a variety of colors were shipped annually at its peak in the 1930s and 1940s, and perhaps 200 million in all since it was introduced in 1936.
The uranium-bearing orange variety was discontinued in 1943 when the government placed wartime restrictions on uranium. Production resumed in 1959 when the restrictions were lifted and continued until 1972. In 1976, the company reintroduced the Fiesta line, but the orange color could not be duplicated with the new lead- and uranium-free glazes.
Fiesta ware in its original colors has become a collector's item, and prices have climbed accordingly. A dinner plate that sold for 35 cents in 1936 is now worth $25 to $30, Mr. Conley said.
A reporter for The Sun purchased two saucers and a sugar bowl for less than $26 in a Cockeysville antique store. A serving platter was available for $46.
Other brand names that used uranium-based pigments included Caliente, Early California, Poppytrail, Stangl and Vistosa, according to the Food and Drug Administration.
For consumers, the uranium in Fiesta ware poses health issues that differ from those associated with radon gas.
The ionizing radiation from uranium can be a cancer hazard, depending on its strength, duration and distance from the body. If ingested, uranium is chemically harmful to the kidneys.
A 1992 study by the U.S. Geological Survey found that highly acidic foods can leach uranium from Fiesta ware at levels ranging from 24 to 1,600 times those considered safe for drinking water. The study said acidic foods, such as tomato sauce, sauerkraut, vinegar and orange juice, should not be consumed from such dinnerware.
Fiesta's manufacturer says that's good advice for any type of old dinnerware. "We would not recommend storing anything with a high acid content for a long period of time," said Mr. Conley.
Responding to a warning by New York state health authorities about the danger of uranium leaching from orange Fiesta ware, the FDA said in 1981 that the "levels of radioactive material in ceramic tableware are not considered hazardous."
The FDA warned, however, that eating or drinking from the orange dishes "should be avoided as unnecessary exposure to radioactive materials." Display by collectors was ruled safe.
Dr. Hon has calculated that the average "dose rate" of radiation, for someone close enough to eat from Fiesta ware three times a day for a year, is 1.1 rems. That is described as four times the average annual exposure to a U.S. citizen from natural sources, such as radioactive rock formations and outer space.
However, the level is only 20 percent of the maximum exposure of 5 rems a year considered safe by the federal government, Mr. Zeman said.
Those who want to get rid of Fiesta ware safely may dispose of it in local landfills with the rest of their garbage, according to Maryland environmental officials and Cynthia Jones, program safety chief at the Nuclear Regulatory Commission.