Melamine toxicity.

Melamine contamination of infant formula in China and its health effects highlight the safety of the global food supply especially as it relates to formula-fed infants. Melamine is a widely used industrial chemical not considered acutely toxic with a high LD(50) in animals. The data available on acute and chronic human exposure to melamine have been limited and extrapolated from animal data. Pet food contamination in 2004 and 2007 showed stone formation and illness in animals when melamine was co-ingested with cyanuric acid. The recent outbreak in infants showed that melamine ingested in large doses may cause stones and illness without significant ingestion of cyanuric acid or other melamine-related chemicals. This may be due to increased uric acid excretion in infants and formation of melamine-uric acid stones. Diagnosis and treatment of infants exposed to melamine requires further study. Clinical signs and symptoms in infants are nonspecific. The stones may be radiolucent and are not consistently seen on ultrasound. The use of alkalinization of the urine for treatment has been proposed, but is of unproven benefit. The FDA and other regulatory agencies have recommended acceptable levels of melamine in foods for consumption. Melamine ingestion has been implicated in stone formation when co-ingested with cyanuric acid, but will cause urinary stones in infants when large amounts of melamine alone are ingested.