12-4+Melamine+Effects+to+human+health

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 LD 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 0.5 milligrams per kg of body mass (reduced to 0.2 mg per kg in April 2010), Canada declared a limit of 0.35 mg and the US FDA’s limit was put at 0.63 mg, but was later reduced to 0.063 mg daily. 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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Acute toxicity
Melamine is reported to have an oral LD50 of 3248 mg /kg based on rat data. It is also an irritant when inhaled or in contact with the skin or eyes. The reported dermal LD50 is >1000 mg/kg for rabbits. A study by USSR researchers in the 1980s suggested that melamine cyanurate, commonly used as a fire retardant, could be more toxic than either melamine or cyanuric acid alone. For rats and mice, the reported LD50 for melamine cyanurate was 4.1 g/kg (given inside the stomach) and 3.5 g/kg (via inhalation), compared to 6.0 and 4.3 g/kg for melamine and 7.7 and 3.4 g/kg for cyanuric acid, respectively. A toxicology study in animals conducted after recalls of contaminated pet food concluded that the combination of melamine and cyanuric acid in diet does lead to acute renal failure in cats. A 2008 study produced similar experimental results in rats and characterized the melamine and cyanuric acid in contaminated pet food from the 2007 outbreak. A 2010 study from Lanzhou University attributed renal failure in humans to uric acid stone accumulation after ingestion of melamine resulting in a rapid aggradation of metabolites such as cyanuric acid diamide (ammeline ) and cyanuric acid.

Chronic toxicity
Ingestion of melamine may lead to reproductive damage, or bladder or kidney stones , which can lead to bladder cancer. A study in 1953 reported that dogs fed 3% melamine for a year had the following changes in their urine: (1) reduced specific gravity, (2) increased output , (3) melamine crystalluria , and (4) <span class="wiki_link_ext">protein and <span class="wiki_link_ext">occult blood. A survey commissioned by the American Association of Veterinary Laboratory Diagnosticians suggested that crystals formed in the kidneys when melamine combined with cyanuric acid, "don't dissolve easily. They go away slowly, if at all, so there is the potential for chronic toxicity."

Treatment of urolithiasis
Fast diagnosis and treatment of acute obstructive <span class="wiki_link_ext">urolithiasis may prevent the development of acute <span class="wiki_link_ext">renal failure .Urine alkalinization and stone liberalization have been reported to be the most effective treatments in humans.

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