Toxicity
Melamine is described as being "Harmful if swallowed, inhaled or absorbed through the skin. Chronic exposure may cause cancer or reproductive damage. Eye, skin and respiratory irritant.” However, the short-term lethal dose is on a par with common table salt with an LD50 of more than 3 grams per kilogram of bodyweight. U.S. Food and Drug Administration (FDA) scientists explained that when melamine and cyanuric acid are absorbed into the bloodstream, they concentrate and interact in the urine-filled renal microtubules, then crystallize and form large numbers of round, yellow crystals, which in turn block and damage the renal cells that line the tubes, causing the kidneys to malfunction.
The European Union set a standard for acceptable human consumption (Tolerable Daily Intake) of melamine at 0.2 mg per kg of body mass, (previously 0.5 milligrams), Canada declared a limit of 0.35 mg and the US FDA’s limit was put at 0.063 mg daily (previously 0.63 mg). The World Health Organization’s food safety director estimated that the amount of melamine a person could stand per day without incurring a bigger health risk, the "tolerable daily intake" (TDI), was 0.2 mg per kg of body mass.
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