Everyone's heard of the problem of Pyrex cookware coming apart under the right circumstances and the danger of lead leaching from some types of ceramic bowls is well-known.
But who would have thought twice about eating soup or other hot foods from a melamine bowl?
Now researchers say they have evidence that serving hot foods in melamine bowls releases melamine, which has been shown to be associated with painful urinary stones in both children and adults and with kidney failure and even death when ingested in large quantities.
Melamine is a chemical with a high nitrogen content. Besides being used to make plastics, it has sometimes been added to animal feed to increase its apparent protein content -- and it has sometimes been illicitly added to human and pet food with disastrous results.
In 2008, more than 53,000 illnesses and at least four deaths were blamed on melamine-tainted milk in China and elsewhere.Â Thousands of dogs and cats became ill or died after melamine was added to pet food in 2007.
In 2008, the U.S. Food and Drug Administration said it had foundÂ melamine in infant formula but said trace amounts were probably safe.
The FDA has said that tiny amounts of melamine "can migrate very slowlyÂ out of the plastic into food that comes into contact with the tableware" but in a 2011 statement said that it "has been found that melamine does not migrate from melamine-formaldehyde tableware into most foods." Â
In the latest study, however, Chia-Fang Wu, M.S., Ph.D., of Kaohsiung Medical University, Taiwan, and colleagues conducted a crossover study of noodle soup consumption in melamine bowls and total melamine excretion in urine.
According to a research letter published in JAMA Internal Medicine, 12 healthy individuals (six men and six women) participated in the investigation. One group consumed 500 mL of hot noodle soup in a melamine bowl and another group consumed soup in ceramic bowls.
Urine samples were collected from all participants after consumption for 12 hours. After a three-week washout, the assigned treatments were reversed.
Total melamine excretion in urine for 12 hours was nearly eight times higher for the group served from melamine bowls compared to the group eating from ceramic bowls (8.35 Âµg vs. 1.31 Âµg).
"Melamine tableware may release large amounts of melamine when used to serve high-temperature foods. ... The amount of melamine released into food and beverages from melamine tableware varies by brand, so the results of this study of one brand may not be generalized to other brands. ... Although the clinical significance of what levels of urinary melamine concentration has not yet been established, the consequences of long-term melamine exposure still should be of concern," the authors conclude.
In its 2011 statement, the FDA said that the risk was confined primarily to heating foods in microwave ovens.
"FoodsÂ and drinks should not be heated on melamine-based dinnerware inÂ microwave ovens.Â Â OnlyÂ ceramic or otherÂ cookwareÂ which specifies thatÂ the cookware isÂ microwave-safe should be used. The food may then beÂ served on melamine-based tableware," the FDA said.