Some tableware may release melamine when used to serve hot food, Taiwanese researchers have found.
However the amounts of melamine leached are unlikely to be at levels which would cause serious harm to people.
In the study entitled "A crossover study of noodle soup consumption in melamine bowls and total melamine excretion in urine", hot noddle soup was served to two groups, with one group given ceramic bowls and the other melamine bowls.
The participants gave urine samples before the meal and then every two hours for the next 12 hours. The samples of those who ate out of the melamine bowls had an average level of 8.35 micrograms of melamine in their samples, compared to 1.3 micrograms for those who ate of the ceramic bowls.
The study was led by Chia-Fang Wu, of Kaohsiung Medical University in Taiwan, and has been published in the journal JAMA Internal Medicine.
"Melamine tableware may release large amounts of melamine when used to serve high-temperature foods," Wu concluded.
The researchers said the amount of melamine released into food varied between brands and should not be generalised across all melamine tableware.
However the health effects of the melamine levels leeched from bowls into food are not yet clear.
"Although the clinical significance of what levels of urinary melamine concentration has not yet been established, the consequences of long-term melamine exposure should still be of concern," Wu said.
The researchers recommended people serve hot food in ceramic crockery, to be on the safe side.
High doses of melamine has been linked to kidney damage, with previously studies finding the chemical can increase the likelihood of kidney stones. The health risks of the compound melamine, used as a resin in plastics, were highlighted in 2008, when dairy products tainted with the chemical killed six babies and hospitalised thousands more in China.
Professor Sir Colin Berry, emeritus professor of Pathology, Queen Mary University of London, said the results of the study were not unexpected.
"This study has a good experimental design and shows very small amounts of melamine excreted, as expected. As the authors point out, no comments can be made about effects but at low levels of melamine you would not expect toxicity. The 'follow-up' paper would be to see if those who used melamine always have more stones than those who don't. But you would need huge numbers to carry this out so I am not sure it could be done. The findings of the current study are, in my view, noise of no clinical significance."
Dr Ian Musgrave, a senior lecturer at the University of Adelaide's Faculty of Medicine, said the total levels of urine excreted suggest an exposure to melamine more than 600 times lower than the most stringent exposure limit - despite the researchers using a brand of melamine bowls with the highest melamine leaching on contact with hot fluids.
"The Wu et al study suggests that even with a melamine ware that has a very high level of melamine leaching, the level of melamine exposure that results may have very minor health impacts, if any at all," Dr Musgrave said. "However, the fact that even small amounts of melamine can leach from these ubiquitous food containers at high temperatures should make us cautious. It may be useful to test melamine tableware for melamine leaching, and only permit the sale of low leachant tableware. It may also be prudent to avoid keeping very hot foods in melamine bowls for extended periods of time."